• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
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  • 优先权
    • 专利摘要:
    The present invention relates to a method for producing stainless steel sheet finished in at least three different ways including an HRAP finish, a 2D finish and a BA finish. The starting rolls of hot-rolled steel sheet have a thickness varying between 1.85 mm and 13.5 mm. In a first production line, this sheet steel is first annealed and pickled in a succession of pickling baths. Depending on the thickness of the sheet steel, the gearbox must be switched to a low or high gear. To make this possible without having to insert recyclable replacement rolls into the production line, during gear shifting, sheet metal is produced with a reduced thickness and with the 2D finish further made of stainless steel with one of the numbers 1.4301, 1.4306, 1.4307, 1.4401, 1.4404 and 1.4571 according to EN 10088-1: 2014.
    公开号:BE1026912B1
    申请号:E20195931
    申请日:2019-12-18
    公开日:2020-07-22
    发明作者:Jurgen Collas
    申请人:Aperam Stainless Belgium；
    IPC主号:
    专利说明:

    The present invention relates to a method of producing stainless steel finished in at least three different ways, including an HRAP finish ("Hot Rolled Annealed and Pickled" ), a 2D finish and a BA finish (gloss or bright annealed - “Bright Annealed”). By means of a surface roller, the sheet steel with the 2D finish can be further finished into sheet steel with a 2B finish that is glossier than the matt sheet steel with the 2D finish The production of the finished sheet steel is based on rolls of hot-rolled, not yet pickled sheet steel, the so-called black rolls, which are of various stainless steel grades, including ferritic, martensitic, austenitic and austenitic-ferritic duplex steel grades, and has a thickness that varies between 1.85mm and 13.5mm Rolled sheet steel are unrolled and are each guided by means of electric motors, each of which drives a guide roller via a gearbox that can be switched in a high and low gear, at a virtually constant speed through at least one first production line, at least one annealing furnace, a series of of at least four consecutive pickling baths and at least one subsequent passivating pickling bath.
    The process for producing the stainless steel sheet with the HRAP finish is carried out in the first production line. At least one of the said rollers is hereby unrolled hot-rolled, not yet pickled sheet steel, which has a thickness of up to
    D BE2019 / 5931 may have 13.55 mm, and passed through the first production line at an almost constant speed such that the sheet metal is successively annealed, pickled and passivated.
    The annealing is intended to remove the stresses created in the steel during the hot rolling while the pickling is intended to remove the oxide skin that has formed on the hot rolled sheet steel. In addition, the low-chromium layer underneath must be stained away such that a thin chromium oxide layer can be formed in the passivating pickling bath, which provides the stainless character of the steel.
    In the method of producing the stainless steel sheet with the 2D finish, the sheet steel produced in the first production line with the HRAP finish is further finished in a cold rolling mill and in a second production line. In order to be able to cold-roll the sheet metal optimally, it preferably has a thickness of at most 10 mm and more preferably a thickness of at most 8 mm. The second production line contains at least one further annealing furnace, a number of further successive pickling paths and at least one further passivating pickling bath. The sheet steel with the HRAP finish is thus cold-rolled and re-annealed, pickled and passivated.
    Cold rolling of the sheet metal, with the thickness of the sheet steel decreased by at least 25%, produces a smoother surface compared to the HRAP finish. Re-annealing is necessary to relieve the stresses in the material and re-pickling is required to re-remove the oxide layer formed during annealing, after which the sheet metal must then be passivated again. The matt surface of the 2D finish thus obtained is then usually made more glossy by further treating the sheet steel with a so-called surface roller. In this way, a 2B finish with a smooth surface is obtained.
    In the method for producing the stainless steel sheet with the BA finish, the sheet steel produced in the first production line with the HRAP finish is further finished in a cold rolling mill and in a third production line. In order to be able to cold-roll the sheet metal optimally, it preferably has a thickness of at most 10 mm and more preferably a thickness of at most 8 mm. The third production line contains at least one BA annealing furnace with a reducing atmosphere therein. The sheet steel with the HRAP finish is thus cold rolled and re-annealed. Due to the presence of the reducing atmosphere in the BA annealing furnace, only the stresses are removed from the material therein without the material oxidizing in the BA annealing furnace. The steel is given a glossy surface, whereby autopassivation then automatically forms a thin oxide layer again, which does not, however, negate the glossy character of the material.
    The following acids or combinations thereof are usually used for pickling stainless steel, in particular stainless chrome nickel steel: nitric acid (HNO3), hydrogen fluoride (HF), sulfuric acid (H2SO4) and hydrochloric acid (HCI). The action of these acids is described, for example, in the American Iron and Steel Institute's “Cleaning and descaling stainless steels” manual, which was reprinted in 1988 by the Nickel Development Institute.
    Because the different rolls of sheet metal can have different thicknesses, and because thicker sheet steel has to be heated longer in the annealing furnace before annealing, the sheet metal with the greater thicknesses must be passed through the first production line at a lower speed. This speed can be controlled by means of the electric motors. However, due to the greater force that must be exerted on thicker and thus stiffer and heavier sheet steel, it is also necessary to switch back to low gear with the reduction gearboxes mentioned. Thus, under a first predetermined thickness of the sheet metal, said reduction gearboxes are shifted into said high gear while shifting into said low gear above a second predetermined thickness greater than or equal to said first predetermined thickness. Before switching from high to low gear or vice versa, the first production line must be stopped and restarted after switching.
    The problem here is that it takes a few minutes, in particular three minutes, before all the reduction gearboxes have been switched over and the first production line can be restarted. After all, this is a production line that is several hundred meters long. Since, depending on the thickness of the sheet metal, its normal residence time in the annealing furnace is only 1 to 4 minutes, it is clear that the sheet metal which is in the furnace during standstill will be over-annealed. In practice, therefore, sheet metal is first introduced into the first production line, which will no longer be used before stopping the line for switching gear. After having been introduced into the production line several times, this replacement roller must be recycled. Part of the production is therefore lost to this. If available, it is preferable to use rolls that did not meet the quality requirements in any case.
    The drawback of introducing such replacement rollers is that it takes some time for them to be introduced into the production line and removed therefrom. This insertion and removal of the replacement roller thus increases the time that production stops. Moreover, the energy that is put into these rollers in the annealing furnace is completely lost. Because the pickling acids also act on these replacement rollers, these are also further used during the passing of the replacement rollers through the pickling baths. A final drawback of using the replacement rollers is that they are not black rolls, as they have previously been annealed and pickled. This changes the temperature development, which is created in the annealing furnace by means of gas burners. When a black roller is reinserted, which has considerably different absorption, reflection and emission values for heat compared to an already pickled roller, the temperature development in the annealing furnace will start to fluctuate and thus it will again take some time before a stable temperature trend is obtained.
    Where in the past the production of sheet metal has been carried out in larger campaigns in order to avoid the disadvantages of shifting gears, among other things, it has become increasingly important to be able to produce more to order, in order to avoid large stocks, in which it is of course essential to overcome the disadvantages associated with shifting gears.
    The object of the invention is therefore to provide a new method for producing stainless steel sheet with different finishes and in different thicknesses, which makes it possible to switch between different thicknesses, which require a different acceleration of the reduction gearboxes in the first production line, without replacement rollers must be introduced in the first production line and thus without unnecessary waste of acids and energy.
    For this purpose, the method according to the invention is characterized in that, before switching from the high gear to the low gear, the first production line is stopped: - when in the first production line there is only sheet steel that is of said austenitic quality and which is manufactured made of stainless steel with one of the numbers 1.4301, 1.4306, 1.4307,
    1.4401, 1.4404 and 1.4571 according to EN 10088-1: 2014; and
    - in said annealing furnace there is only sheet steel with a thickness between 2.8 and 4.0 mm and in said pickling baths, including the passivating pickling bath, only sheet metal with a thickness between 1.8 and 4.0 mm; that, before switching from low gear to high gear, the first production line is stopped: - when the first production line contains only sheet steel of the aforementioned austenitic quality and which is made of stainless steel with one of the numbers 1.4301, 1.4306 , 1.4307,
    1.4401, 1.4404 and 1.4571 according to EN 10088-1: 2014; and - in said annealing furnace there is only sheet metal with a thickness between 2.8 and 4.0 mm and in said pickling baths, including the passivating pickling bath, only sheet metal with a thickness of 4.0 to 6.0 mm; and that the sheet steel contained therein during the standstill of the first production line is further finished in said cold rolling mill and in said second production line to produce said sheet metal with the 2D finish. According to the invention, it was surprisingly found that, for certain stainless steels, too long a residence time thereof in the annealing furnace and pickling baths in the first production line does not hinder the production of sheet metal with the required mechanical and surface properties when the thickness of the sheet metal in the first production line meets the conditions stated above and when the sheet steel is subsequently cold-rolled and further annealed and pickled to produce sheet metal with the 2D finish. This sheet steel with the 2D finish can then be further finished to a more glossy 2B finish. Certain properties to be met by austenitic sheet steel are described, for example, in EN 10088-2: 2014 and include mechanical features such as tensile strength and elongation.
    As described in the pickling handbook “Pickling Handbook - Surface Treatment of Stainless Steels” by voestalpine Böhler Welding Nordic AB, among other things, stainless steels can be divided into four groups according to their pickling behavior, namely very easy to pickle (group 1), easy to pickle (group 2), difficult to stain (group 3) and very difficult to stain (group 4). The steels used according to the invention during gear shifting all belong to group 2 of the easily pickling steels.
    Of course, such easy-to-pickle steels are also easily over-stained if they are pickled for too long, for example during the standstill of the first production line in the pickling baths. As described, for example, in the publication “Effect of Acid Pickling on Microstructure and Surface Roughness of 316L Stainless Steel” by Rahil Izzati Mohd Asri et al., Pickling the sheet metal for too long results in a rough surface, which in the method according to the present invention is undesirable.
    In order to avoid over-pickling of the sheet metal during the standstill of the first production line, it would thus be appropriate to use more difficult-to-pickle steels during gear shifting. However, the inventors have found that with such steel which is more difficult to pickle in the first production line it was not possible to produce sheet metal with the required properties during its standstill. In particular, they have found that in order to remedy the errors caused by too long a residence time in the annealing furnace it was essential that the sheet metal be easily pickled. After all, when annealing for too long, a relatively thick oxide skin was formed, including a less corrosion-resistant steel layer with a reduced chromium content, which both had to be stained away in the pickling baths. This was only possible with sample from the easy to stain group (group 2). Stainless steel from the group of the very easy-to-pickle steel grades was again over-stained to achieve the desired end quality.
    Essential in the method according to the invention is that the sheet metal produced during the gear shifting in the first production line is further cold-rolled and re-annealed and pickled in the second production line to form sheet metal with the 2D or 2B finish. This further processing not only corrects the surface sheet metal errors, but also corrects the internal structure of the sheet metal that was disturbed during the material's annealing time. This internal structure is essential to obtain the required mechanical properties of the material. In an embodiment of the method according to the invention, said first production line is annealed, from 4.0 to 6.0 mm thick, plated steel, pickled and passivated with said gearboxes in low gear and then switched to the first production line. annealing, pickling and passivation of stainless steel sheet with a thickness between 2.8 and 4.0 mm, said stainless steel sheet with a thickness between 2.8 and 40 mm being passed through said annealing furnace, with the reduction gearboxes still in low gear, wherein after said stainless steel sheet with a thickness of between 2.8 and 4.0 mm fully extends through said annealing furnace, and said stainless steel sheet with a thickness of 4.0 to 6.0 mm is preferably still in said pickling baths, the first production line is shut down, the gearboxes are switched to high gear and the first production line is restarted. The presence of relatively thin sheet steel in the annealing furnace offers the advantage that if it is heated too strongly by the standstill, it can still be cooled back sufficiently quickly before it is passed through the pickling baths. Furthermore, the internal structure of such thin sheet steel will be easier to restore during cold rolling and re-annealing and pickling. The minimum thickness allows the sheet metal to be rolled flat enough. This embodiment also offers the advantage that a smaller length of thin sheet metal is passed through the annealing furnace too slowly, and therefore remains there for too long, since the gear is shifted to higher gear when the thicker sheet steel is still in the pickling baths.
    In an embodiment of the method according to the invention, in said first production line, stainless steel sheet with a thickness of more than 6.0 mm is annealed, pickled and passivated with said reduction gears in low gear and is switched to annealing, pickling in the first production line and passivating stainless steel sheet with a thickness between 2.8 and 4.0 mm, before switching to annealing, pickling and passivating stainless steel sheet with a thickness between 2.8 and 4.0 mm before switching to the annealing, pickling and passivation of stainless steel sheet with a thickness of 4.0 to 6.0 mm and only then for annealing, pickling and passivation of stainless steel sheet with a thickness between 2.8 and 4.0 mm, whereby only at this last switch, the first production line is shut down and the gearboxes are switched from low to high gear. This embodiment therefore provides an option with min. Imale effect on quality switching from producing the thickest sheet steel to thin sheet steel.
    In an embodiment of the method according to the invention, in said first production line, stainless steel sheet with a thickness between 2.8 and 4.0 mm is annealed, pickled and passivated with said gearboxes in high gear and then switched to the first production line. annealing,
    pickling and passivation of stainless steel sheet with a thickness of at least 4.0 mm, before said stainless steel sheet with a thickness of at least 4.0 mm is introduced into said annealing furnace, and the sheet steel with a thickness between 2.8 and 4 , 0 mm still fully extends through the aforementioned annealing furnace, the first production line is shut down, the gearboxes are shifted to low gear, the first production line is restarted and the sheet metal with a thickness of at least 4.0 mm is led into the annealing furnace .
    The presence of relatively thin sheet steel in the annealing furnace again offers the advantage that if it is heated too strongly by the standstill, it can still be cooled back sufficiently quickly before it is passed through the pickling baths. Furthermore, the internal structure of such thin sheet steel will be easier to restore during cold rolling and re-annealing and pickling. The minimum thickness allows the sheet metal to be rolled flat enough.
    In an embodiment of the method according to the invention, the sheet steel has a thickness before the cold rolling which is reduced by at least 25%, preferably by at least 30% and more preferably by at least 35% by cold rolling. Preferably, the sheet metal that is in the first production line during the standstill of the first production line has a thickness which is reduced by at least 35%, preferably by at least 40% and more preferably by at least 45% during cold rolling.
    The stronger flat-rolling offers the advantage that the sheet material not only becomes thinner but also smoother, whereby the surface defects, in particular the surface that is too rough, which can be produced during over-pickling, can be better eliminated. Errors in the internal structure caused by excessive annealing can also be corrected in this way.
    In an embodiment of the method according to the invention, during the annealing and re-annealing of the steel sheet, the steel sheet is heated to a temperature of at least 800 ° C, preferably to a temperature of at least 900 ° C.
    In an embodiment of the method according to the invention, said first predetermined thickness and said second predetermined thickness are comprised between 3.5 and 45 mm. Preferably said first predetermined thickness is substantially equal to said second predetermined thickness, said first and said second predetermined thickness being approximately 4.0 mm. It has been found that it is advantageous to switch to the lower gear from a previously limited sheet metal thickness, so as to burden the electric motors as little as possible. In an embodiment of the method according to the invention, at least a part of the sheet metal with the 2D finish, and preferably almost all the sheet steel with the 2D finish, is passed through a surface roller at least once in order to obtain stainless steel with a 2B finish that has a shinier surface than the stainless steel sheet with the 2D finish. Preferably, at least the sheet steel that is in the first production line during the standstill of the first production line is passed through a surface roller (37) at least once in order to produce stainless steel sheet with a 2B finish that has a glossier surface than the stainless steel sheet with the 2D finish. Preferably, the sheet metal has a thickness before the treatment with the surface roller which is not reduced, or at the most by 1%, by the treatment with said surface roller. In this embodiment, the surface quality of the sheet metal is improved. A further annealing step is not necessary here because the internal structure of the sheet metal has not been changed by the surface roller.
    In an embodiment of the method according to the invention, at least a part of the sheet metal with the BA finish, and preferably almost all the sheet steel with the BA finish, is passed through a surface roller at least once in order to obtain a shinier surface obtained.
    Preferably, the sheet metal has a thickness before the treatment with the surface roller which is not reduced, or at the most by 1%, by the treatment with said surface roller.
    Also in this embodiment the surface quality of the already glossy sheet steel is further improved.
    A further annealing step is not necessary here because the internal structure of the sheet metal has not been changed by the surface roller.
    In an embodiment of the method according to the invention, it is characterized in that, for producing the stainless steel sheet with the HRAP finish, said pickling paths are in a first configuration, wherein said series of pickling baths is divided into a first series with at least the first three pickling baths and in a second series of at least one pickling bath and in which the pickling baths of said first series of pickling baths each contain a mixed acid pickling agent based on at least hydrogen fluoride and sulfuric acid and / or nitric acid, wherein said pickling bath is an acid pickling agent based on at least hydrogen fluoride and wherein the passivating pickling bath contains a passivating pickling agent based on at least hydrogen fluoride and nitric acid; that, for producing the stainless steel sheet with the BA finish, said pickling baths are in a second configuration, wherein the pickling baths of said first series each contain a hydrochloric acid pickling agent based on at least hydrochloric acid, wherein said pickling pickling pad is a further acid pickling agent based at least hydrogen fluoride and wherein the passivating pickling bath is a further passivating pickling agent based on at least hydrogen fluoride and nitric acid; and that, to produce the stainless steel sheet with the 2D finish, said pickling baths are in said first or in said second configuration.
    It has been found that for the annealed BA finish, the best surface quality of the glossy sheet steel can be obtained by the second pickling path configuration, namely by a sequence of pickling baths in which the first series contains a hydrochloric acid based pickling agent. The hydrochloric acid pickling agent, in particular, makes it possible to better stain away the grain boundary attack in order to obtain the desired gloss effect. For the 2D, or the 2B finish to be further produced therefrom, it was found that in order to obtain a good surface quality it was possible to use the first configuration of pickling paths, namely to mix the acid with hydrogen fluoride and sulfuric acid and / or nitric acid. to be used in the first series of pickling baths and thus it was not necessary to use hydrochloric acid which is difficult to regenerate or recycle. For the HRAP finish, the use of the mixing acid of the first configuration in the successive pickling baths of the first series was found to be most suitable.
    In an embodiment of the method according to the invention, said passivating mordant is a mordant based on hydrogen fluoride, nitric acid and sulfuric acid and said further passivating mordant is a mordant based on hydrogen fluoride and nitric acid.
    Thus, in this embodiment, the pickling agent in the passivating pickling bath contains additional sulfuric acid for stronger pickling when the pickling baths are in their first configuration in which pickling is mainly done with the less strong mixed acid pickling agent.
    Preferably, during the production of the stainless steel sheet with the HRAP or 2D finish, with the pickling baths in said first configuration, sulfuric acid is metered into said passivating pickling bath to compensate for sulfuric acid reacting therein during pickling.
    In this way, an improved pickling can be obtained without using the stronger pickling hydrochloric acid pickling agent in the first set of pickling baths.
    In an embodiment of the method according to the invention, said acid pickling agent is a hydrofluoric acid and sulfuric acid pickling agent and said further acid pickling agent is a hydrogen fluoride based pickling agent.
    In this embodiment, the pickling agent in the acid pickling bath contains additional sulfuric acid so as to be able to pick more strongly when the pickling baths are in their first configuration in which pickling is mainly done with the less strong mixed acid pickling agent.
    Preferably, during the production of the stainless steel sheet with the HRAP or 2D finish, with the pickling baths in said first configuration, sulfuric acid is metered into said acid pickling bath to compensate for sulfuric acid which reacts away during pickling.
    In this way, an improved pickling can be obtained without using the stronger pickling hydrochloric acid pickling agent in the first set of pickling baths.
    In an embodiment of the method according to the invention, said mixed acid pickling agent, said acid pickling agent and said passivating pickling agent contain sulfuric acid, wherein during the production of the stainless steel sheet with the HRAP or 2D finish, with the pickling baths in said first configuration, sulfuric acid in said pickling baths are metered into said acid pickling bath and said passivating pickling bath to compensate for sulfuric acid which reacts away during pickling.
    In this way, the required pickling action of the mixed acids in the different baths during pickling can be maintained.
    In an embodiment of the method according to the invention, the mixed acid pickling agent which is in the first configuration in the last or the last pickling paths of said first series is a mixed acid pickling agent based on hydrogen fluoride and sulfuric acid and the mixed acid pickling agent which is at least in the first configuration in the first or at least in the first two pickling baths of said first series there is a mixed acid pickling agent based on hydrogen fluoride, sulfuric acid and nitric acid.
    In this embodiment, the pickling action of the first or the first two pickling baths is enhanced in order to be able to optimally address the part of the black oxide skin that is still on the sheet steel at that time.
    In an embodiment of the method according to the invention, said first series of pickling baths contains at least four pickling baths.
    In an embodiment of the method according to the invention, production is effected almost continuously with said first production line, with an average of at least once a week, and in particular at least once every five days, switching from high gear to low gear or other way around.
    By regularly switching gears, it is possible to produce all the sheet metal thicknesses to order, so that only a minimal amount of stock has to be maintained.
    In an embodiment of the method according to the invention, the pickling agent is sprayed onto the sheet steel in said pickling paths, the sheet steel preferably also being immersed in the pickling agent.
    By spraying the mordant onto the sheet metal, the stained material is removed more efficiently, so that pickling can be done more efficiently, especially when the sheet metal is also immersed in the mordant.
    Further advantages and details of the invention will become apparent from the following description of some special embodiments of the method according to the invention. This description is made with reference to the accompanying drawings in which: Figure 1 schematically shows an overview of the first production line used in an embodiment of the method according to the invention for producing sheet steel with an HRAP finish; Figures 2A to 2C schematically show three different cold rolling used for cold rolling a part of the sheet steel with the HRAP finish produced in the first production line shown in Figure 1; Figure 3 schematically shows an overview of a first Embodiment of a second production line used in an Embodiment of the method according to the invention for further processing the cold-rolled sheet steel into sheet metal with a 2D finish; Figure 4 schematically shows a surface roller for making the sheet steel smoother and more glossy, in particular for further finishing the sheet steel with the 2D finish obtained in the second production line according to Figure 3, to sheet steel with a 2B finish; Figure 5 schematically shows an overview of a second embodiment of the second production line used in an embodiment of the method according to the invention for further processing of the cold-rolled sheet steel, which second production line corresponds to the second production line according to Figure 3 with inline a surface roller as shown in Figure 4, thus producing sheet metal with a 2B finish directly; Figure 6 schematically shows an overview of a third production line, namely a blank annealing line, used in an embodiment of the method according to the invention for further processing the cold-rolled sheet steel into sheet steel with a BA finish; and Figure 7 shows two successive pickling baths from the first production line shown in Figure 1 with the associated reservoirs required to replace the pickling solution in both pickling baths.
    The invention generally relates to a method of producing stainless steel sheet with different finishes. In particular, sheet steel with an HRAP finish (hot rolled, annealed and pickled - “Hot Rolled Annealed and Pickled”), sheet steel with a 2D finish (cold rolled, annealed and pickled) and sheet steel with a BA finish (cold rolled and bright annealed - "Bright Annealed") produced. Both the sheet metal with the BA finish and the sheet steel with the 2D finish are usually made more glossy by passing it through a surface roller. The matte 2D finish is thus converted into the more glossy 2B finish.
    The stainless steel contains iron and at least 10.5% by weight of chromium. The carbon content is up to 1.2% by weight. The stainless steel can further contain other elements such as nickel, molybdenum, titanium, manganese, copper, aluminum, etc. The stainless steel can be of the austenitic, ferritic or duplex type. The invention applies in particular to the production of stainless steel of the austenitic type, but can also be used in the production of the other steel types.
    In particular, all steel grades described in EN 10088-1: 2014 can be produced.
    After producing the stainless steel material itself in the various electric arc furnaces and the AOD refining units, it is cooled and solidified in a continuous casting plant and burned to length. These slabs are, at a high temperature, hot rolled into rolls of sheet steel 1 with a thickness of, for example, 1.85 to 13.5 mm. Due to the high temperature to which the steel has been subjected, a relatively thick, black oxide skin has formed on the sheet steel. Furthermore, the steel has hardened during hot rolling and tensions have built up in it. The method according to the invention now relates to the further processing of these black rolls of sheet steel into the sheet steel with the finishes described above.
    A first continuous production line that is used for this is shown schematically in figure 1. At the beginning of the line, the black rolls of sheet steel 1 are unrolled and welded together by means of a welding machine 2 to form a continuous strip of sheet steel 3. This continuous strip of sheet steel 3 is guided over different rollers 4 through the first production line. A number of the rollers 4 are arranged in an S-configuration in order to be able to exert sufficient grip and traction on the strip of sheet steel 3 and are each driven by means of electric motors 5 via a reduction gearbox 6. The speed of the electric motors 5 can be controlled to adjust the line speed, depending on the thickness and / or material of the sheet steel 3 passing through the production line. The gearbox 6 also allows shifting in high or low gear. The production line must always be shut down to change the gear. The present invention relates to a method which, as will be described in further detail below, allows not having to insert recyclable replacement rollers in the first production line for this switching and, in particular, to stop the first production line for a moment to shift from gear during the production of the sheet metal itself.
    In a first section of the production line, the sheet steel accumulator 7, the strip of sheet steel 3 is guided zigzag over rollers 4. The distance between these rollers 4 can be changed in order to accumulate more or less sheet steel in this first zone, such that, for instance during welding of the rolls of sheet steel 1, the sheet steel 3 still remains at a constant speed throughout the production line and in particular can continue to move through its annealing furnace.
    After all, after the first section there is an annealing furnace 8 in the first production line in which the sheet steel 3 is heated to a temperature of at least 800 ° C, and more particularly to a temperature of at least 900 ° C. The temperature in the annealing furnace 8 is usually below 1200 ° C. In the annealing furnace 8, the sheet metal 3 undergoes a certain temperature profile, as a result of which the stresses disappear from the sheet steel 3 and the desired internal structure is obtained.
    After the annealing furnace 8, a guench section 9 follows in which the sheet steel 3 is cooled again by means of water and possibly air. The sheet steel 3 then passes through a dryer 10 in which it is dried. After the dryer 10, an oxide breaker 11 follows, in which the relatively thick, black oxide skin on the sheet steel 3 is broken.
    In a next step, the sheet metal 3 is passed through a blasting machine 12 with which metal grains are blasted on the oxide skin of the sheet steel 3 to make it loose and porous. The oxide skin is then mechanically removed as much as possible by means of brushes 13.
    After an electrochemical pickling, in the electrochemical pickling baths 14, the sheet steel 3 is brushed again, with the brushes 15, and the sheet steel 3 is then rinsed, in the rinsing bath 16 in which the rinsing agent is sprayed on the sheet steel 3.
    In the chemical pickling section, with six successive chemical pickling baths 17A-F, the sheet steel 3 is then pickled and passivated in the last pickling bath 17F. The last pickling bath is therefore a passivating pickling bath 17F. After the chemical pickling, the sheet steel 3 is again rinsed in a rinsing bath 55, dried in a dryer 18 and then zigzagged through an accumulator 19. In an inspection station 20, the quality of the steel can be monitored, after which the continuous strip of sheet steel 3 is cut into pieces again, with metal shears 21, and rolled into rolls 22 with the sheet steel with the HRAP finish. A part of these rolls 22 can be used as a final product, optionally after first cutting them into plates. The stainless steel sheet with the HRAP finish is matte and gray in color and has a fairly rough surface. The thickness of this sheet steel is the same as the thickness of the hot-rolled sheet steel, and is in particular included between 1.85 and 13.5 mm.
    In the first place, this can be cold-rolled for the further finishing of the HRAP sheet steel. HRAP sheet steel with a thickness of up to 10 mm and preferably with a thickness of less than or equal to 8 mm is particularly suitable for cold rolling. By cold rolling, the thickness of the sheet steel 3 is firstly reduced to the desired final thickness. In particular, this thickness is reduced by 25 to 75%, and preferably by at least 30%, and more preferably by at least 35%. In addition to obtaining the desired final thickness, rolling has additional objectives such as obtaining good flatness, a high surface quality and the desired mechanical properties (crystal structure). Different types of rollers can be used for cold rolling.
    The first type is a quarto roll 23, which is shown schematically in Figure 2a. The roller group of such a roller consists of two working cylinders 24 between which the sheet metal 3 is rolled and two much larger supporting cylinders 25. The supporting cylinders 25 serve to absorb the enormous forces acting on the working cylinders 24. The desired decrease in thickness is obtained by passing the sheet steel 3 through this roller 23 one or more times, the sheet steel being unrolled and rolled in front and behind the sheet. To avoid damage to the sheet steel 3 and to the cylinders, the roll gap is cooled with an oil emulsion.
    A second type of roller is a sexto roller 26 which is shown schematically in Figure 2b. This roller again contains two working cylinders 24 and two supporting cylinders 25, but an intermediate cylinder 27 is still arranged between the working and supporting cylinders.
    The roller 28, shown in figure 2C, is a twenty roller roller and contains two working cylinders 24, eight supporting cylinders 25 and ten intermediate cylinders 27 between them. This roller 28 can be used by the optimum pressure distribution and by means of very fine ground working cylinders 24, in combination with clean roller oil instead of the oil emulsion, a high-quality surface quality can be obtained. This twintig roller 28 is used in particular for the production of sheet steel with the high-gloss or BA finish, but can also be used for the production of the sheet steel with the 2D or 2B finish.
    After cold rolling, the sheet metal 3 must be re-annealed to remove the stresses from the material again and to obtain the desired crystal structure therein. This can happen in a second production line that is built approximately the same as the first.
    The main parts of a possible embodiment of the second production line are shown in figure 3.
    These parts again include a welder 29, an accumulator 30, an annealing furnace 56, electrochemical pickling baths 31, chemical pickling baths 32A-F including a passivating pickling bath 32F, a dryer 33, an accumulator 34, and a metal shear 35. The sheet steel thus produced has a 2D finish, and has a rather matte appearance, and is rolled up into rolls 36. To improve the surface quality of this sheet steel, the rolls 36 are further treated with a surface roller 37, shown in figure 4. This surface roller has only two working cylinders 38 which exert only a limited pressure on the sheet steel 3, such that the thickness of the sheet steel is not reduced, or in any case reduced by less than 1%.
    By the action of the surface roller 37, the quality of the surface of the sheet steel 3 can be further improved and in particular the rather matte 2D finish is transformed into the more glossy 2B finish.
    In order to make optimum use of the twintig roller 28, it is used not only in the production of the sheet steel 3 with the BA finish, but also in the production of part of the sheet steel with the 2D or 2B finish.
    In order to avoid stains on the sheet steel with the 2D or 2B finish as a result of the oil remaining on the surface thereof after cold rolling, a spraying installation 57 is provided for the further annealing furnace 56, with which an extra layer of oil is applied to the top surface of the cold-rolled sheet steel 3 is sprayed.
    The same oil or a different type of oil can be used here as it was applied to the working cylinders 24 of the cold roll 28 with which the relevant sheet steel 3 was cold-rolled.
    It was found that in this way the appearance of stains on the end product due to the presence of the rolling oil could be optimally avoided.
    Even if the sheet metal is first cold-rolled in the quatro roller 23 or in the sexto-roller 26, in which an oil emulsion is always used, it is advantageous to apply a continuous layer of oil on the surface of the cold-rolled sheet steel before after all, it is also possible to prevent the occurrence of stains caused by the presence of the limited amount of oil-in-water emulsion on the surface of the sheet metal.
    Figure 5 schematically shows a second embodiment of the second production line in which the surface roller 37 is incorporated at the back of the production line itself.
    In this way, sheet metal with the 2B finish is produced immediately and the rollers 36 therefore no longer have to be treated separately with the surface roller 37.
    Figure 6 shows the main parts of a third production line, namely a production line for producing sheet steel 3 with a high-gloss finish (BA finish). This third production line contains a welding machine 39, an accumulator 40, a BA annealing furnace 41 with a reducing atmosphere, in particular with an atmosphere based on hydrogen gas, a further accumulator 42 and a metal shears 43. The produced sheet metal with the BA finish is rolled up into rollers 44. These rollers 44 are preferably also treated with the surface roller 37 to improve the gloss and the surface quality of the sheet metal.
    The rolls of sheet steel with the HRAP finish, the 2D finish, the 2B finish and the BA finish can be the end product as such, but can also first be cut into plates or strips.
    In the method of producing steel sheet with the different finishes, the first production line, shown in Figure 1, is used in the production of all the different finishes.
    A problem here is that the composition of the acids in the
    24, BE2019 / 5931 pickling baths 17A-F should be adapted.
    After all, for the production of sheet steel with the HRAP finish, the 2D finish and the 2B finish, a mixed acid pickling agent can be used in the pickling baths, while for the production of sheet steel with the
    BA finishing is essential that the sheet metal is treated with hydrochloric acid pickling agent in the first production line.
    Such a hydrochloric acid pickling agent can in theory also be used for the production of the other finishes, but in practice this is not possible due to the fact that it is not possible to process all the chlorine-containing waste water that would be created by this.
    In the method according to the invention, therefore, the composition of the pickling baths is changed regularly in order to be able to produce the different finishes alternately, on order.
    Figure 7 gives a schematic overview of the first two pickling seams 17A and B of the first production line.
    The other pickling baths are constructed in the same way.
    As can be seen in more detail in this overview, the pickling baths are thus contained two by two in separate tanks 45.
    The pickling agent in both pickling baths is separated by a partition 46 such that it cannot flow from one pickling bath to another.
    The mordant itself is introduced into the mordant baths by spraying the mordant both at the top and at the bottom of the sheet metal by means of nozzles 47.
    The mordant sprayed into the pickling baths, in particular in the first pickling bath 17A, according to the first configuration described below, is pumped via the discharge pipes 48 and the pump 49A into a settling tank 50A from which it overflows into a reservoir 51A.
    The mordant is then again sprayed from this reservoir 51A by means of a pump 52A through a conduit 53A into the mordant bath 17A.
    The sediment formed in the settling tank 50A can be pumped out by means of a pump 54A.
    In order to be able to exchange the pickling agent in the pickling baths in order to thus obtain the second configuration described below, the same second system for the second pickling agent is provided, namely a discharge pump 49A ', a settling tank 50A', a reservoir 51A ', a pump 52A', a line 53A 'and a sedimentation pump 54A'. For the second pickling bath, also shown in Figure 7, and for the subsequent pickling paths, the same numbers are used for these elements but with the letter corresponding to the letter of the pickling bath.
    In the first configuration, namely in the configuration with the mixed acid pickling agent for the production of the HRAP, 2D or 2B finish, the first and second pickling baths 17A and B contain a mixed acid pickling agent containing mainly hydrogen fluoride, sulfuric acid and nitric acid, the third and fourth pickling pads 17C and D a mixed acid pickling agent with predominantly hydrogen fluoride and sulfuric acid, the fifth pickling bath, namely said acid pickling bath 17E, an acid pickling agent again containing mainly hydrogen fluoride and sulfuric acid, and the sixth pickling bath, said passivating pickling bath 17F, a passivating pickling agent with mainly hydrogen fluoride, nitric acid and sulfuric acid.
    Through a connection (not shown) between the reservoirs 51A-E for this mixed acid pickling agent, the pickling agent is preferably flowed in cascade from the fifth 51E to the first reservoir 51A so as to be able to pickling in the fifth pickling bath 17E with purer pickling agent, i.e. pickling agent with less salts dissolved therein.
    In each of the pickling paths, the free acid content is preserved during pickling by additionally adding sulfuric acid. In the first and second pickling bath, the nitric acid is dosed to enhance its pickling action.
    In the second configuration, namely in the configuration with the hydrochloric acid pickling agent for the production of the BA finish, the first to the fourth pickling bath 17A-D contains a hydrochloric pickling agent with mainly hydrochloric acid, the fifth or said acid pickling bath 17E, a further acid pickling agent with mainly hydrogen fluoride , and the sixth or said passivating pickling bath 17F, a further passivating pickling agent containing mainly hydrogen fluoride and nitric acid.
    To switch from the first to the second configuration or vice versa, the first production line is no longer shut down. The switch from the first to the second configuration or vice versa is carried out during the production of sheet metal with the 2D or 2B finish.
    To switch from the first to the second configuration, one continues to produce sheet steel with the 2D or 2B finish. In a first step, the mixed acid pickling agent in the fourth pickling bath 17D is replaced by the hydrochloric acid pickling agent by first pumping the pickling bath into the reservoir 51D, which takes about fifteen minutes, and then the sheet metal in the fourth pickling bath 17D with the Hydrochloric pickling agent from reservoir 51D to spray. Subsequently, the dosage of sulfuric acid in the acid pickling bath 17E and in the passivating pickling bath 17F can be stopped such that the sulfuric acid can be used therein to form the further acid pickling agent and the further passivating pickling agent with no or virtually no sulfuric acid. After all, the hydrochloric acid pickling agent in the fourth pickling bath 17D has a sufficiently strong effect at that time to sufficiently stain away any drying stains.
    After all, in the next step, the third pickling bath 17C is emptied and the mixed acid pickling agent therein is replaced by the hydrochloric acid pickling agent. The same then happens for the second pickling bath 17B and finally for the first pickling pad 17A. As soon as the hydrochloric acid pickling agent is sprayed onto the sheet metal in the first pickling bath 17A, this sheet steel can be used for the production of sheet metal with the BA finish.
    In order to switch from the second configuration to the first configuration again, production of sheet metal with the 2D or 2B finish is started again.
    In a first step, the hydrochloric acid pickling agent in the first pickling pad 17A is replaced by the mixed acid pickling agent by first pumping the pickling bath empty into the reservoir 51A ', which takes about fifteen minutes, and then by removing the sheet metal in the first pickling pad 17A with the mixing acid pickling agent from the reservoir 51A to be sprayed.
    In the next step, the second pickling pad 17B is emptied and the hydrochloric acid pickling agent therein is replaced by the mixed acid pickling agent.
    The same then happens for the third pickling bath 17C and finally for the fourth pickling bath 17D.
    Before the fourth pickling bath 17D is emptied, sulfuric acid is added to the acid pickling soap 17E and to the passivating pickling bath 17F, preferably when the hydrochloric acid pickling agent in the third pickling pad 17C is replaced by the mixed acid pickling agent.
    In this way, the acid pickling bath 17E and the passivating pickling bath 17F have a stronger pickling action when the fourth pickling bath 17D becomes empty and thus dry spots can be formed on the sheet metal.
    After all, these drying spots are already at least partially eliminated by the stronger pickling action of the latter two pickling baths 17E and F.
    As soon as the mixed acid pickling agent is sprayed onto the sheet steel in the fourth pickling bath 17D, this sheet steel can no longer be used for the production of sheet steel with the 2D or 2B finish, but also for the HRAP finish.
    The inspection of the sheet metal produced with the different finishes showed that no significant deviations from the 2D or 2B finish sheet metal produced during the changeover could be detected during the change of the pickling bath configuration in the manner described above, and that the prescribed quality requirements were met. However, if sheet metal with the BA finish, or with the HRAP finish, was produced during the exchange, quality deviations were found, which in particular for the BA finish were such that the prescribed quality requirements were no longer met. The same was noted when the replacement of the pickling solutions in the different pickling baths was not carried out in the order described above.
    For the tests carried out, the different pickling baths each had a length of approximately seventeen meters. Because the sheet steel with the 2D or 2B finish had a thickness of less than 8 mm, and was thus guided relatively quickly through the first production line, its residence time in the different baths varied between 15 and 30 seconds.
    According to the present invention, it is also possible to operate without replacement rollers when changing gearboxes from high to low gear or vice versa. The high gear allows the electric motors 5 to pull the sheet metal 3 at a greater maximum speed through the first production line, for example at a maximum speed of about 100 m / min while the low gear allows the sheet metal 3 to pass through with a greater force. to draw the first production line. This greater force is necessary when the sheet steel 3 has a greater thickness, for instance a thickness greater than 4 mm. The greater force is necessary not only because of the greater weight of the thicker sheet steel 3, but mainly because the thicker sheet steel 3 is stiffer and thus more difficult to guide around the different rollers 4.
    When switching from high gear to low gear, it is important that the sheet metal 3 which is in the annealing furnace 14 during the standstill of the first production line has a thickness between
    2.8 and 4.0 mm and that the sheet steel 3 currently present in the pickling baths 17A-E and in the passivating pickling bath 17F has a thickness between 1.8 and 4.0 mm. When switching from the low gear to the high, it is important that the sheet steel 3 which is in the annealing furnace 14 during the standstill of the first production line has a thickness between 2.8 and 4.0 mm and that the sheet steel 3 at that time in the pickling paths 17A-E and in the passivating pickling bath 17F there is a thickness between 4.0 and 6.0 mm.
    If sheet metal with a thickness of more than 6 mm, at a low speed, is processed in the first production line, and it is desired to switch to machining thinner sheet steel, with a thickness of less than 4 mm, at a higher speed, first switched to sheet steel with a thickness of 4.0 to 6.0 mm. Then the switch is made to sheet steel with a thickness between 2.8 and 40 mm. As soon as this thin sheet steel extends completely through the annealing furnace 14, and the sheet steel with a thickness of 4.0 to 6.0 mm is still in the pickling baths 17A-F, the first production line is shut down and the gearboxes 6 are switched to the high gear. Even with this high gear, the necessary force or sheet metal with a thickness of 4.0 to 6.0 mm can be applied to pull it out of the pickling baths. The thinner sheet steel, with a thickness of 2.8 to 4.0 mm, which was located in the annealing furnace 14, can be cooled quickly enough because of the limited thickness, even if it was heated too much. Due to the small thickness, the internal structure can also be fully restored afterwards by cold rolling to obtain the required mechanical properties.
    If sheet metal with a thickness between 1.8 and 2.8 mm, at a high speed, is processed in the first production line, and you want to switch to machining thicker sheet steel, with a thickness of more than 4 mm, at a lower speed, is first switched to sheet steel with a thickness of 2.8 to 4.0 mm. Then it is then switched to sheet steel with a thickness of more than 4.0 mm. As soon as this thick sheet steel extends completely through the annealing furnace 14, and the sheet steel with a thickness of 1.8 to 2.8 mm is still in the pickling baths 17A-F, the first production line is shut down and the gearboxes 6 are switched to the high gear. The sheet steel, with a thickness of 2.8 to 4.0 mm, which was in the annealing furnace 14, can be cooled sufficiently quickly, due to the limited thickness, even if it was heated too much. Due to the minimum thickness of 2.8 mm, this sheet steel can also be rolled sufficiently flat.
    As a result, the internal structure can also be completely restored to obtain the required mechanical properties.
    When shutting down the first production line for gear shifting, it has also proved essential that the stainless steel contained therein when shutting down the first production line is stainless steel with one of the numbers 1.4301,
    1.4306, 1.4307, 1.4401, 1.4404 and 1.4571 according to EN 10088-1: 2014. By using these steel grades, it was possible to continue producing sheet metal with a 2D or a 2B finish during gear shifting that meets the required quality requirements, in particular surface quality and mechanical properties, such as these in particular. required by EN 10088-2: 2014.
    With other steel grades, especially with steel grades with numbers 1.4003, 1.4512, 1.4016, 1.4510, 1.4521, 1.4513, 1.4526,
    1.4509 and 1.4621, with steel grades with numbers 1.4021, 1.4028,
    1.4034 and 1.4419 and with steel grades with numbers 1.4550, 1.4371,
    1.4618, 1.4833, 1.4062, 1.4362, 1.4462 and 1.4410, this turned out to be impossible. Of the latter steels, steel grade No. 1.4016 is very easy to pickle, steel grade No. 1.4462 is difficult to pickle and steel grade No. 1.4410 is very difficult to pickle.
    权利要求:
    Claims (23)
    [1]
    1. Method for producing stainless steel sheet finished in at least three different ways, including an HRAP finish (“Hot Rolled Annealed and Pickled”), a 2D finish and a BA finish (“Bright Annealed”), in which method rolls (1) are hot-rolled, not yet pickled sheet steel of various stainless steel grades, including ferritic, martensitic, austenitic and austenitic-ferritic duplex steel grades, with a thickness ranging between 1.85 mm and 13.5 mm, and each of which is guided through at least a first production line at a predetermined, substantially constant speed by means of electric motors, each driving a guide roller via a gearbox which can be switched in a high and low gear, the first production line comprising at least one annealing furnace (8) , a series of at least four consecutive pickling baths (17A-E) and at least one subsequent passivating pickling bath (17 F), wherein the process for producing the stainless steel sheet with the HRAP finish is carried out in said first production line and comprises the following steps: - providing at least one of said rolls (1) with hot rolled, unpainted sheet steel (3); - unrolling the roll (1) of sheet steel; - guiding the unrolled sheet steel (3) at a substantially constant speed through said first production line for successively annealing, pickling and passivating the unrolled sheet steel, and - removing the thus obtained sheet steel from the first production line with the HRAP -finishing, the method for producing the stainless steel sheet with the 2D finish in said first production line and further in a cold rolling mill (23, 26, 28) and in a second production line, at least one further annealing furnace (56), includes a number of further successive pickling paths (32A - E)) and at least one further passivating pickling bath (32F), and comprises the following steps:
    - providing at least one of said rollers (1)
    hot-rolled sheet metal, not yet pickled (3);
    - unrolling the sheet metal roll;
    - guiding the unrolled sheet steel (3) at a substantially constant speed through said first production line for successively annealing, pickling and passivating the unrolled sheet steel;
    - cold rolling of the passivated sheet steel;
    re-annealing, pickling and passivating the cold-rolled steel sheet in said second production line; and
    - removing the thus obtained sheet steel with the 2D finish from the second production line, the method for producing the stainless steel sheet with the BA finish being carried out in said first production line and further in a cold rolling mill (28) and in a third production line, without pickling paths but with at least one BA annealing furnace (41) containing a reducing atmosphere, and comprising the following steps:
    - providing at least one of said rolls (1) hot-rolled, not yet pickled sheet steel (3);
    - unrolling the sheet metal roll;
    - guiding the unrolled sheet steel (3) at a substantially constant speed through said first production line for successively annealing, pickling and passivating the unrolled sheet steel;
    - cold rolling of the passivated sheet steel;
    re-annealing the cold-rolled steel sheet under said reducing atmosphere in said third production line; and
    - removing the thus obtained sheet metal with the BA finish from the third production line, wherein said predetermined speed is adjusted in function of the thickness of the sheet steel, said gearboxes being shifted into said high gear under a first predetermined thickness of the sheet steel and wherein above a second predetermined thickness, which is greater than or equal to said first predetermined thickness, said gearboxes are shifted into said low gear, with the first production line being shut down before switching from high to low gear or vice versa, and again after switching is started, characterized in that, before switching from high gear to low gear, the first production line is stopped: - when the first production line contains only sheet steel of the aforementioned austenitic quality and which is made of stainless steel with one of the numm ers 1.4301, 1.4306, 1.4307,
    1.4401, 1.4404 and 1.4571 according to EN 10088-1: 2014; and - when in said annealing furnace there is only sheet metal with a thickness between 2.8 and 4.0 mm and in said pickling baths and in said passivating pickling bath, only sheet metal with a thickness between 1.8 and 4.0 mm; that, before switching from low gear to high gear, the first production line is stopped: - in the first production line there is only sheet steel of the aforementioned austenitic quality and which is made of stainless steel with one of the numbers 1.4301, 1.4306 , 1.4307,
    1.4401, 1.4404 and 1.4571 according to EN 10088-1: 2014; and - when in said annealing furnace there is only sheet steel with a thickness between 2.8 and 4.0 mm and in said pickling baths and in said passivating pickling bath, only sheet steel with a thickness of 4.0 to 6.0 mm; and that the sheet steel contained therein during the standstill of the first production line is further finished in said cold rolling mill and in said second production line to produce said sheet metal with the 2D finish.
    [2]
    Method according to claim 1, characterized in that in said first production line, stainless steel sheet with a thickness of 4.0 to 6.0 mm is annealed, pickled and passivated with said gearboxes in low gear and then switched to the gearbox in the first production line annealing, pickling and passivation of stainless steel sheet with a thickness between 2.8 and 4.0 mm, whereby said stainless steel sheet with a thickness between 2.8 and 4.0 mm is passed through said annealing furnace, with the reduction boxes still in low gear, wherein after said stainless steel sheet with a thickness of between 2.8 and 4.0 mm fully extends through said annealing furnace, and said stainless steel sheet with a thickness of 4.0 to 6.0 mm is preferably still in said pickling baths, the first production line is shut down, the gearboxes are switched to high gear and the first production line is restarted.
    [3]
    Method according to claim 2, characterized in that in said first production line, stainless steel sheet with a thickness of more than 6.0 mm is annealed, pickled and passivated with said reduction gear in the low gear and that it is switched to annealing in the first production line , pickling and passivation of stainless steel sheet with a thickness between 2.8 and 4.0 mm, whereby before switching to annealing, pickling and passivating stainless steel sheet with a thickness between 2.8 and 40 mm is first switched to annealing , pickling and passivation of stainless steel with a thickness of 4.0 to 6.0 mm and only then annealing, pickling and passivation of stainless steel with a thickness between 2.8 and 4.0 mm, with the latter only switching the first production line is shut down and the gearboxes are switched from low to high gear.
    [4]
    Method according to any one of claims 1 to 3, characterized in that in said first production line, stainless steel sheet with a thickness of between 2.8 and 4.0 mm is annealed, pickled and passivated with said gearboxes in high gear and then switched annealing, pickling and passivation of stainless steel sheet with a thickness of at least 4.0 mm in the first production line, whereby before said stainless steel sheet with a thickness of at least 4.0 mm is introduced into said annealing furnace, and the sheet steel with a thickness between 2.8 and 4.0 mm still fully extends through said annealing furnace, the first production line is shut down, the gearboxes are switched to low gear, the first production line is restarted and the sheet metal with a thickness of at least 4.0 mm is fed into the annealing furnace.
    [5]
    Method according to claim 4, characterized in that in said first production line stainless steel steel with a thickness of less than 2.8 mm is annealed, pickled and passivated with said reduction gear in the high gear and that it is switched to annealing in the first production line , pickling and passivation of stainless steel with a thickness of more than 4.0 mm, before switching to annealing, pickling and passivating stainless steel with a thickness of more than 40 mm, before switching to annealing, pickling and passivation made of stainless steel with a thickness of 2.8 to 4.0 mm and only then for annealing, pickling and passivation of stainless steel with a thickness of more than 4.0 mm, the first production line only being shut down when the latter is switched and the gearboxes are switched from high to low gear.
    [6]
    Method according to any one of claims 1 to 5, characterized in that before the cold rolling, the sheet steel (3) has a thickness that by cold rolling by at least 25%, preferably by at least 30% and more preferably by at least Is reduced by 35%.
    [7]
    Method according to any one of claims 1 to 6, characterized in that the sheet steel which is present in the first production line during standstill of the first production line has a thickness which during cold rolling is at least 35%, preferably at least 40%. % and more preferably is reduced by at least 45%.
    [8]
    Method according to any one of claims 1 to 7, characterized in that during the annealing and re-annealing of the sheet metal, the sheet metal is heated to a temperature of at least 800 ° C, preferably to a temperature of at least 900 ° C C.
    [9]
    Method according to any one of claims 1 to 8, characterized in that said first predetermined thickness and said second predetermined thickness are comprised between 3.5 and 4.5 mm.
    [10]
    Method according to any one of claims 1 to 9, characterized in that said first predetermined thickness is substantially equal to said second predetermined thickness, said first and said second predetermined thickness being approximately 4.0 mm.
    [11]
    Method according to any one of claims 1 to 10, characterized in that at least a part of the sheet metal with the 2D finish, and preferably almost all the sheet steel with the 2D finish, at least once through a surface roller (37 ) in order to produce stainless steel sheet with a 2B finish that has a shinier surface than the stainless steel sheet with the 2D finish.
    [12]
    Method according to claim 11, characterized in that at least the sheet steel which is in the first production line during the standstill of the first production line is passed through a surface roller (37) at least once in order to form stainless steel sheet with a 2B finish produce a glossier surface than the stainless steel sheet with the 2D finish.
    [13]
    Method according to any one of claims 1 to 12, characterized in that at least part of the sheet metal with the BA finish, and preferably almost all sheet steel with the BA finish, at least once through a surface roller (37 ) is obtained in order to obtain a shinier surface.
    [14]
    Method according to claim 12 or 13, characterized in that before the treatment with the surface roller (37), the sheet steel (3) has a thickness which is not reduced, or at the most by 1%, by the treatment with said surface roller.
    [15]
    Method according to any one of claims 1 to 14, characterized in that, for producing the stainless steel sheet with the HRAP finish, said pickling baths (17A-E) are in a first configuration, wherein said set of pickling paths is divided into a first series comprising at least the first three pickling baths (17A-D) and in a second series comprising at least one acid pickling bath (17E) and wherein the pickling baths (17A-D) of said first series pickling baths each comprise a mixed acid pickling agent based on at least hydrogen fluoride and sulfuric acid and / or nitric acid, wherein said acid pickling bath (17E) contains an acid pickling agent based on at least hydrogen fluoride and wherein the passivating pickling bath contains a passivating pickling agent based on at least hydrogen fluoride and nitric acid; that, for producing the stainless steel sheet with the BA finish, said pickling baths (17A-E) are in a second configuration, wherein the pickling baths (17A-D) of said first series each contain hydrochloric acid pickling agent based on at least hydrochloric acid wherein said acid pickling bath (17E) is a further acid pickling agent based on at least hydrogen fluoride and wherein the passivating pickling bath is a further passivating pickling agent based on at least hydrogen fluoride and nitric acid; and that, to produce the stainless steel sheet with the 2D finish, said pickling baths (17A-E) are in said first or in said second configuration;
    [16]
    A method according to claim 15, characterized in that said passivating mordant is a hydrofluoric, nitric and sulfuric acid mordant and said further passivating mordant is a hydrofluoric and nitric acid mordant.
    [17]
    Method according to claim 15 or 16, characterized in that during the production of the stainless steel sheet with the HRAP or 2D finish, with the pickling baths (17A-E) in said first configuration, sulfuric acid in said passivating pickling bath (17F ) is dosed to compensate for sulfuric acid which reacts away during pickling.
    [18]
    Method according to any one of claims 15 to 17, characterized in that said acid pickling agent is a hydrofluoric acid and sulfuric acid pickling agent and that said further acid pickling agent is a hydrogen fluoride based pickling agent.
    [19]
    Method according to claim 18, characterized in that during the production of the stainless steel sheet with the HRAP or 2D finish, with the pickling baths (17A-E) in said first configuration, sulfuric acid is dosed in said acid pickling bath (17E) to compensate for sulfuric acid which reacts during pickling.
    [20]
    Method according to any one of claims 15 to 19, characterized in that said mixed acid pickling agent, said acid pickling agent and said passivating pickling agent contain sulfuric acid, wherein during the production of the stainless steel sheet with the HRAP or 2D finish, with the pickling baths (17A -E) in said first configuration, sulfuric acid is metered into said pickling baths (17A-E) and into said passivating pickling bath (17F) to compensate for sulfuric acid which reacts away during pickling.
    [21]
    Method according to any one of claims 15 to 20, characterized in that the mixed acid pickling agent, which in the first configuration is in the last or last pickling paths (17C and D) of said first series, is a hydrogen fluoride and sulfuric acid mixed pickling agent and that the mixed acid pickling agent contained in the first configuration at least in the first or at least in the first two pickling baths (17A and B) of said first series is a mixed acid pickling agent based on hydrogen fluoride, sulfuric acid and nitric acid.
    [22]
    Method according to any one of claims 15 to 21, characterized in that said first series of pickling baths (17A-D) contains at least four pickling paths (17A-D).
    [23]
    Method according to any one of claims 1 to 22, characterized in that production is carried out almost continuously with said first production line, with an average changeover from the high at least once a week, and in particular at least once every five days. gear to low gear or vice versa.
    Method according to any one of claims 1 to 23, characterized in that the pickling agent is sprayed onto said sheet steel (3) in said pickling baths (17A-E), the sheet steel preferably also being immersed in the pickling agent.
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    同族专利:
    公开号 | 公开日
    BE1026906B1|2020-07-22|
    BE1026912A1|2020-07-14|
    BE1026906A1|2020-07-14|
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    法律状态:
    2020-08-26| FG| Patent granted|Effective date: 20200722 |
    优先权:
    申请号 | 申请日 | 专利标题
    BE20185926A|BE1026906B1|2018-12-20|2018-12-20|Method for producing stainless steel sheet finished in at least three different ways|
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