• 专利附录
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    • 专利摘要:
    The present invention relates to a steel composition comprising, in percentages by weight of the total composition: Carbon: 0.05-0.40, preferably 0.10-0.30; Chromium: 2.50-5.00, preferably 3.00-4.50; Molybdenum: 4.00-6.00; Tungsten: 0.01-1.80, preferably 0.02-1.50; Vanadium: 1.00-3.00, preferably 1.50-2.50; Nickel: 2.00-4.00; Cobalt: 2.00-8.00, preferably 3.00-7.00; Iron: balance and unavoidable impurities, optionally further comprising one or more of the following: Niobium: ≤ 2.00; Nitrogen: ≤ 0.50, preferably ≤ 0.20; Silicon: ≤ 0.70, preferably 0.05-0.50; Manganese: ≤ 0.70, preferably 0.05-0.50; Aluminum: ≤ 0.15, preferably ≤ 0.10; the combined Niobium + Vanadium content being in the range 1.00-3.50; and the carbon + nitrogen content being in the range 0.05-0.50. It also relates to its manufacturing process, the steel blank obtained and a mechanical member comprising it.
    公开号:FR3052789A1
    申请号:FR1655664
    申请日:2016-06-17
    公开日:2017-12-22
    发明作者:Jacques Bellus；Atman Benbahmed；Johanna Andre；Fredrik Sandberg
    申请人:ERASTEEL；Aubert and Duval SA；
    IPC主号:
    专利说明:

    Ces deux compositions sont très similaires. La principale différence tient à la teneur en W.
    Ces deux coulées laboratoire ont été transformées en barre de diamètre 40 mm par un procédé de forgeage à chaud sous presse de 2000T. Des barreaux de diamètre 30 mm ont été usinés dans la barre et cémentés.
    Les barreaux cémentés ont été traités par (1) un chauffage à 1150°C, (2) un maintien pendant 15 min à 1150°C pour austénitisation, (3) un refroidissement sous gaz neutre à une pression de 2 bars, (4) une période à température ambiante, (5) un refroidissement à -75°C pendant 2 heures, et (6) 3 revenus à 560°C pendant 1 heure chacun.
    Les profils de dureté superficielle en HV obtenus mesurés selon la norme ASTM E384 sont reportés dans la figure 1 avec ceux obtenus avec l'acier 50NÎL (0,12%C-4%Cr-4,2%Mo-3,4%Ni-l%V) ayant subit le même traitement.
    La composition selon l'invention ayant une faible teneur en W présente des niveaux de duretés plus élevés, de l'ordre de 860 HV correspondant à 66 H RC. Il faut aussi noter que la baisse de la teneur en W par rapport à l'art antérieur n'affecte pas significativement le niveau de dureté du métal de base qui est de l'ordre de 540 HV correspondant à 51 HRC. L'acier ayant la composition selon l'invention (faible teneur en W) permet donc d'obtenir de plus hauts niveaux de dureté avec un traitement thermique limité à 1150°C par rapport à celui de l'art antérieur ayant une plus forte teneur en W.
    The present invention relates to a new type of low carbon 20CrMoCo steel for thermochemical treatment particularly for the field of transmissions such as bearings and gears.
    Bearings are mechanical devices to ensure relative movements and constraints in orientation and direction between two parts. The bearings comprise several components: inner ring, outer ring as well as rolling bodies (ball or cylinder) arranged between these two rings. To ensure reliability and performance over time, it is important that these elements have good properties in rolling fatigue, wear, etc., ...
    Gears are mechanical power transmission devices. To ensure a favorable power density (power ratio transmitted by the size of the gears) and the reliability of operation, the gears must have good structural fatigue properties (tooth foot) and contact fatigue (tooth blanks). Conventional techniques for making these metal components use electrical steelmaking processes followed by possible remelting operations, or single or multiple vacuum rejections. The ingots thus produced are then shaped by hot transformation processes such as rolling or forging in the form of bar, tube or ring.
    There are two types of metallurgy to ensure the final mechanical properties. 1st type: the chemical composition of the component makes it possible to obtain the mechanical properties directly after suitable heat treatment. 2nd type: the component requires a thermochemical treatment to enrich the surface with interstitial elements such as carbon and nitrogen. This enrichment in general superficial chemical elements then allows to obtain high mechanical properties after heat treatment on depths of a few millimeters maximum. These steels generally have better ductility properties than the first type steels.
    There are also thermochemical processes applied to steels of the first type aimed at enriching the surface with nitrogen to obtain very high mechanical properties.
    The first of the properties required in the field of rolling or gears is obtaining a very high level of hardness. These type 1 and type 2 steels generally have superficial hardness levels greater than 58 H RC. The most common grades known as M50 (0.8% C-4% Cr-4.2% Mo-1% V), or 50NL (0.12% C-4% Cr-4.2%) Mo-3.4% Ni-1% V) do not exceed after possible thermochemical treatment and heat treatment adapted a surface hardness of 63 H RC.
    GB2370281 discloses a valve seat steel by powder metallurgy technology compacted from powder mixtures of an iron base and harder particles whose matrix has the following composition, in percentages by weight of the composition Total:
    Carbon: 0.2-2.0;
    Chrome: 1.0-9.0;
    Molybdenum: 1.0-9.0;
    Silicon: 0.1-1.0;
    Tungsten: 1.0-3.0;
    Vanadium: 0.1-1.0;
    Nickel-ι-Cobalt + Copper: 3.0-15.0;
    Iron: balance
    However, this matrix comprises 5 to 40% by volume of perlite, which results in a lack of ductility of this matrix and therefore embrittlement.
    The patent application WO2015 / 082342 describes a rolling steel having the following composition, in percentages by weight of the total composition:
    Carbon: 0.05-0.5;
    Chromium: 2.5-5.0;
    Molybdenum: 4-6;
    Tungsten: 2-4.5;
    Vanadium: 1-3;
    Nickel: 2-4;
    Cobalt: 2-8;
    Iron: balance as well as unavoidable impurities, optionally further comprising one or more of the following:
    Niobium: 0-2;
    Nitrogen: 0-0.5;
    Silicon: 0-0.7;
    Manganese: 0-0.7;
    Aluminum: 0-0.15; and in particular composition grade MIX5 (0.18% C-3.45% Cr-4.93% Mo-3.05% W-2.09% V-0.30% Si-2.89% Ni -5.14% Co-0.27% Mn) which is the most interesting because it has the greatest surface hardness.
    This grade makes it possible to reach a superficial hardness after solution treatment at 1150 ° C. and returned at 560 ° C. to a maximum hardness level of about 800 HV, ie an equivalent of 64 HRC maximum (comparative example 1). Obtaining surface hardnesses greater than 64 HRC, in particular using a solution heat treatment at a temperature of less than or equal to 1160 ° C, is therefore difficult to obtain whereas it would make it possible to improve significantly the properties of the component.
    The inventors have surprisingly found that by lowering the tungsten content of the steel described in application WO2015 / 082342, the steel obtained has, after thermochemical treatment, a very high surface hardness and even greater than or equal to 64 HRC after solution heat treatment at 1160 ° C and tempering above 500 ° C.
    This was not at all obvious in view of this document which encouraged the use of a high tungsten content such as in the MIX5 grade (3% tungsten) which is considered as the composition having the best hardness.
    The present invention therefore relates to a steel composition comprising, advantageously consisting essentially of, in particular consisting of, in percentages by weight of the total composition:
    Carbon: 0.05-0.40, preferably 0.10-0.30;
    Chromium: 2.50-5.00, preferably 3.00-4.50;
    Molybdenum: 4.00-6.00;
    Tungsten: 0.01 - 1.80, preferably 0.02-1.50;
    Vanadium: 1.00-3.00, preferably 1.50-2.50;
    Nickel: 2.00-4.00;
    Cobalt: 2.00-8.00, preferably 3.00-7.00;
    Iron: balance as well as unavoidable impurities, optionally further comprising one or more of the following:
    Niobium: <2.00;
    Nitrogen: <0.50, preferably <0.20;
    Silicon: <0.70, preferably 0.05-0.50;
    Manganese: <0.70, preferably 0.05-0.50;
    Aluminum: <0.15, preferably <0.10; the combined Niobium + Vanadium content being in the range 1.00-3.50; and the carbon + nitrogen content being in the range 0.05-0.50.
    A particularly advantageous composition comprises, advantageously consists essentially of, in particular consists of, in percentages by weight of the total composition:
    Carbon: 0.10-0.30, preferably 0.15-0.25;
    Chromium: 3.00 - 4.50, preferably 3.50 - 4.50;
    Molybdenum: 4.00-6.00, preferably 4.50-5.50;
    Tungsten 0.02 - 1.50, preferably 0.03 - 1.40;
    Vanadium: 1.50-2.50; preferably 1.70-2.30;
    Nickel: 2.00-4.00, preferably 2.50-3.50;
    Cobalt: 3.00-7.00, preferably 4.00-6.00;
    Silicon: 0.05-0.50, preferably 0.05-0.30;
    Manganese: 0.05-0.50, preferably 0.05-0.30;
    Iron: balance as well as unavoidable impurities, optionally it also includes one or more of the following:
    Niobium: <2.00;
    Nitrogen: <0.20;
    Aluminum: <0.10; the combined Niobium + Vanadium content being in the range 1.00-3.50; and the carbon + nitrogen content being in the range 0.05-0.50.
    In particular the unavoidable impurities, chosen in particular from Titanium (Ti), Sulfur (S), Phosphorus (P), Copper (Cu), Tin (Sn), Lead (Pb), Oxygen ( O) and their mixtures are kept at the lowest level. These impurities are generally due mainly to the manufacturing process and the quality of charging. Advantageously, the composition according to the invention comprises at most 1% by weight of unavoidable impurities, advantageously at most 0.75% by weight, still more advantageously at most 0.50% by weight, relative to the total weight of the composition.
    The carbide-forming elements, which also have a stabilizing effect on ferrite, so-called alphagenes, are essential to the steel composition according to the invention so as to provide sufficient hardness, resistance to heat and wear. . In order to obtain a ferrite-free microstructure which would weaken the component, it is necessary to add stabilizing elements of the austenite, so-called gammagenic elements.
    A correct combination of austenite stabilizing elements (carbon, nickel, cobalt and manganese) and stabilizing elements of ferrite (molybdenum, tungsten, chromium, vanadium and silicon) makes it possible to obtain a steel composition according to the invention. invention having superior properties, especially after thermochemical treatment such as carburizing.
    The steel composition according to the invention therefore comprises carbon (C) in a content in the range 0.05-0.40%, preferably 0.10-0.30%, even more preferably 0.15- 0.25%, more advantageously 0.18-0.20% by weight relative to the total weight of the composition. Indeed the Carbon (C) stabilizes the austenitic phase of the steel at the heat treatment temperatures and is essential for the formation of carbides which bring the mechanical properties in general in particular the mechanical resistance, the high hardness, the resistance to the heat and to wear. The presence of a small amount of carbon in a steel is beneficial to avoid the formation of unwanted and fragile intermetallic particles and to form small amounts of carbides to prevent excessive grain growth during quenching. The initial carbon content, however, should not be too high since it is possible to increase the surface hardness of the components formed from the steel composition by carburizing. During cementation, the carbon is implanted in the surface layers of the component, so as to obtain a hardness gradient. Carbon is the main element for controlling the hardness of the martensitic phase formed after cementation and heat treatment. In case-hardened steel, it is essential to have a strong core with a low carbon content while having a hard surface with a high carbon content after thermochemical carburizing treatment.
    The steel composition according to the invention also comprises chromium (Cr) in a content in the range 2.50-5.00%, preferably 3.00-4.50%, even more preferred 3.50 4.50%, still more advantageously 3.80-4.00% by weight relative to the total weight of the composition.
    Chrome contributes to the formation of carbides in steel and is, after carbon, the main element that controls the hardenability of steels. However, chromium can also favor ferrite and residual austenite. In addition, increasing the chromium content reduces the maximum quenching temperature. The chromium content of the steel composition according to the invention should not be too high.
    The steel composition according to the invention also comprises molybdenum (Mo) in a content in the range 4.00-6.00%, preferably 4.50-5.50%, even more preferably 4.80- 5.20%, by weight relative to the total weight of the composition.
    Molybdenum improves the resistance to wear, wear resistance and hardness of steel. However, molybdenum has a strong stabilizing effect on the ferrite phase and must not be present in excessive amounts in the steel composition according to the invention.
    The steel composition according to the invention further comprises Tungsten (W) in a content in the range 0.01-1.80%, preferably 0.02-1.50%, even more preferred 0.03 -1.40%, advantageously 0.04-1.30%, more advantageously 0.05-1.30%, by weight relative to the total weight of the composition.
    Tungsten is a ferrite stabilizer and a strong carbide-forming element. It improves resistance to heat treatment and wear and hardness by carbide formation. It is, however, very expensive and as a ferrite stabilizer also lowers the surface hardness of the steel and especially the ductility and toughness properties. For this element to play its full role, it is necessary to carry out high temperature dissolution.
    The steel composition according to the invention further comprises vanadium (V) in a content in the range of 1.00-3.00%, preferably 1.50-2.50%, even more preferred 1.70 -2.30%, advantageously 2.00-2.20%, by weight relative to the total weight of the composition.
    Vanadium stabilizes the ferrite phase and has a strong affinity for carbon and nitrogen. Vanadium provides resistance to wear and tear by forming hard vanadium carbides. Vanadium may be partly substituted by niobium (Nb), which has similar properties.
    The combined Niobium + Vanadium content must therefore be in the range 1.00-3.50% by weight relative to the total weight of the composition.
    If the Niobium is present, its content must be <2.00% by weight relative to the total weight of the composition. Advantageously, the steel composition according to the invention does not comprise Niobium.
    The steel composition according to the invention also comprises nickel (Ni) in a content in the range 2.00-4.00%, preferably 2.50-3.50%, more preferably 2.70- 3.30%, advantageously 3.00-3.20%, by weight relative to the total weight of the composition.
    Nickel promotes the formation of austenite and therefore inhibits the formation of ferrite. Another effect of nickel is to decrease the temperature Ms, that is to say the temperature at which transformation of austenite to martensite begins during cooling. This can prevent the formation of martensite. The amount of nickel must therefore be controlled so as to avoid the formation of residual austenite in the cemented components.
    The steel composition according to the invention also comprises cobalt (Co) in a content in the range 2.00-8.00%, preferably 3.00-7.00%, even more preferred 4.00 -6.00%, advantageously 4.50-5.50%, more preferably 4.90-5.20%, by weight relative to the total weight of the composition.
    Cobalt is a highly stabilizing element of austenite that prevents the formation of undesirable ferrite. Unlike Nickel, Cobalt increases the Ms temperature, which in turn decreases the amount of residual austenite. Cobalt, in combination with nickel, allows the presence of ferrite stabilizers such as the carbide-forming elements Mo, W, Cr and V. The carbide-forming elements are essential for the steel according to the invention because of their effect on hardness, resistance to heat and wear. Cobalt has a small effect of increasing hardness on steel. However, the increase in hardness is correlated with the decrease in toughness. It is therefore not necessary for the steel composition according to the invention to contain an excessive amount of cobalt.
    The steel composition according to the invention may further comprise silicon (Si) in a content <0.70%, by weight relative to the total weight of the composition. Advantageously, it comprises silicon, in particular in a content in the range 0.05-0.50%, preferably 0.05-0.30%, advantageously 0.07-0.25%, more advantageously 0 , 10-0.20%, by weight relative to the total weight of the composition.
    Silicon strongly stabilizes ferrite, but is often present during the steelmaking process during the deoxidation of liquid steel. Low oxygen contents are indeed also important for obtaining low levels of non-metallic inclusion and good mechanical properties such as fatigue resistance and strength.
    The steel composition according to the invention may further comprise manganese (Mn) in a content <0.70%, by weight relative to the total weight of the composition. Advantageously, it comprises manganese, in particular in a content in the range 0.05-0.50%, preferably 0.05-0.30%, advantageously 0.07-0.25%, even more advantageously 0 , 10-0.20%, by weight relative to the total weight of the composition.
    Manganese stabilizes the austenite phase and decreases the Ms temperature in the steel composition. Manganese is generally added to steels during manufacture so as to attach to Sulfur by formation of manganese sulfide during solidification. This eliminates the risk of formation of iron sulphides which have an adverse effect on the hot machining of steels. Manganese is also part of the deoxidation step like Silicon. The combination of manganese with silicon gives deoxidation more efficient than each of these elements alone.
    Optionally, the steel composition according to the invention may comprise nitrogen (N), in a content <0.50%, preferably <0.20%, by weight relative to the total weight of the composition. Nitrogen promotes the formation of austenite and lowers the transformation of austenite to martensite. Nitrogen can to a certain extent replace the carbon in the steel according to the invention. However, the carbon + nitrogen content must be in the range 0.05-0.50% by weight relative to the total weight of the composition.
    Optionally, the steel composition according to the invention may comprise aluminum (Al), in a content of <0.15%, preferably <0.10%, by weight relative to the total weight of the composition. . Aluminum (Al) can indeed be present during the steel manufacturing process according to the invention and contributes very effectively to the deoxidation of the liquid steel. This is particularly the case during reflow processes such as the VIM-VAR process. The aluminum content is generally higher in the steels produced using the VIM-VAR process than in the steels obtained by the powder technology. Aluminum causes difficulties during the atomization by obstruction of the casting nozzle by oxides. A low oxygen content is important for good micro-cleanliness as well as good mechanical properties such as fatigue resistance and mechanical strength. The oxygen content obtained by ingot is typically less than 15 ppm.
    Advantageously, the composition according to the present invention is cementable, that is to say it can undergo a cementation treatment, and even advantageously it can undergo a thermochemical treatment, in particular chosen from carburizing, nitriding, carbonitriding and carburizing followed by nitriding.
    These treatments make it possible to improve the surface hardness of the steel by adding carbon and / or nitrogen elements. Thus, if carburization is used, the carbon content of the surface of the steel increases and thus its surface hardness. The surface is thus advantageously enriched with carbon with an enrichment in particular of between 0.5% - 1.7% by weight, relative to the total weight of the composition.
    If nitriding is used, it is the nitrogen content that increases on the surface of the steel, and therefore also its surface hardness.
    If carbonitriding or cementation followed by nitriding are used, it is the carbon and nitrogen contents on the surface of the steel which are increased and therefore also its surface hardness.
    These methods are well known to those skilled in the art.
    In an advantageous embodiment, the steel composition according to the invention, after a thermochemical treatment, advantageously carburizing or nitriding or carbonitriding or carburizing and then nitriding, followed by a heat treatment, a superficial hardness superior or equal to 64 H RC, advantageously greater than or equal to 65 H RC, still more advantageously greater than or equal to 66 HRC, measured according to ASTM E18 or equivalent standard.
    Said heat treatment may comprise: (1) dissolving the steel at a temperature of between 1100.degree. C. and 1160.degree. C., advantageously between 1140.degree. And 1155.degree. C., in particular 1150.degree. a maintenance at this temperature until complete austenitization, in particular for a period of 15 minutes (quenching), (these 2 phases (1) and (2) allow the total or partial solution of the carbides initially present), - (3) then optionally a first cooling (quenching), in particular under a neutral gas at, for example, a pressure of 2 bar, advantageously up to room temperature (this phase makes it possible to obtain a mainly martensitic microstructure with residual austenite This residual austenite is a function of the cooling temperature: the content decreases with the cooling temperature), - (4) optionally followed by a maintenance at ambient temperature, - (5) then a second cooling at a temperature below -40 ° C, more preferably below -60 ° C, even more preferably about -75 ° C, in particular for 2 hours (this phase decreases the residual austenite), (6) and advantageously one or more incomes, more advantageously at least three incomes, advantageously at a temperature greater than 500 ° C., in particular greater than 550 ° C., more particularly about 560 ° C., more particularly for 1 hour each (this or these revenues allow the precipitation of carbides and the partial or total decomposition of the residual austenite. This makes it possible to obtain ductility properties). The advantage of the steel according to the invention is therefore to obtain high levels of hardness with a limited heat treatment (temperature between 1100oC-1160 ° C, preferably between 1140 and 1155 ° C, in particular 1150 ° C ).
    In a particularly advantageous embodiment, the steel composition according to the invention, after a thermochemical treatment, advantageously carburizing or nitriding or carbonitriding or carburizing and then nitriding, followed by a heat treatment, a martensitic structure having a residual austenite content of less than 10% by weight and free from ferrite and pearlite, known phases to reduce the surface hardness of the steel.
    Said heat treatment may be as described above.
    The present invention further relates to a method of manufacturing a steel blank having the composition according to the invention, characterized in that it comprises: a) a step of producing the steel; (b) a step of processing the steel; c) a thermochemical treatment; d) and a heat treatment.
    Advantageously, the heat treatment of step d) of the process according to the present invention is as described above.
    Advantageously, the thermochemical treatment of step c) of the process according to the present invention consists of a carburizing or nitriding or carbonitriding or cementation and then nitriding treatment, advantageously it is a cementation treatment.
    In particular, step b) of the process according to the present invention consists of a rolling, forging and / or spinning step. These methods are well known to those skilled in the art.
    In an advantageous embodiment, the step a) of developing the process according to the present invention is carried out by a conventional process for preparing a furnace with refining and reflowing under a conductive slag (ESR), or by a VIM process. -VAR, possibly with a step of remelting under conductive slag (ESR) and / or under vacuum (VAR), or by metallurgy of the powders such as atomization by gas and compression by hot isostatic compaction (HIP).
    Thus the steel according to the present invention can be produced by a VIM-VAR process. This process makes it possible to obtain a very good inclusion cleanliness and improves the chemical homogeneity of the ingot. It is also possible to carry out a conductive slag remelting path (ESR: Electro Slag Remelting) or to combine ESR and VAR operations (vacuum remelting).
    This steel can also be obtained by metallurgy powders. This process makes it possible to produce high purity metal powder by atomization, preferably gas atomization, which makes it possible to obtain very low oxygen contents. The powder is then compressed using, for example, hot isostatic compaction (HIP).
    These methods are well known to those skilled in the art.
    The present invention also relates to a steel blank that can be obtained by the process according to the invention. This blank is made of steel having the composition according to the present invention and as described above.
    It further relates to the use of a blank according to the invention or a steel composition according to the invention for the manufacture of a mechanical member, advantageously in the field of transmission such as gears, shafts transmission and bearings.
    Finally, it relates to a mechanical member, advantageously a transmission member or a gear, in particular a gear, a transmission shaft or a bearing, more particularly a bearing, made of steel having the composition according to the invention or obtained from a steel blank according to the invention.
    Indeed, with the steel composition according to the invention, it is possible to combine the high surface hardness and the surface wear resistance with a core having a high resistance to fatigue and a high mechanical strength.
    These steels are therefore usable in demanding areas such as bearings for aerospace.
    In addition, the steel obtained is inexpensive, in particular because of the low tungsten content, although it has a surface hardness level after high thermochemical treatment, with a martensite structure free of massive phases of the austenite or ferrite or perlite type. The invention will be better understood on reading the examples and figures which follow, which are given by way of non-limiting indication.
    In the examples, unless otherwise indicated, all percentages are by weight, the temperature is expressed in degrees Celsius and the pressure is atmospheric pressure.
    FIG. 1 represents the profile of surface hardness (microhardness in HV0.5 as a function of the depth of the steel (in mm) of an example according to the invention and a comparative example according to the application WO2015 / 082342 having the composition shown in Table 1 below and a comparative example 50NIL (0.12% C-4% Cr-4.2% Mo-3.4% Ni-1% V), obtained after cementation and treatment thermal reactor comprising the following steps: (1) heating at 1150 ° C, (2) holding for 15 min at 1150 ° C for austenitization, (3) cooling under a neutral gas at a pressure of 2 bar, (4) a period at room temperature, (5) cooling to -75 ° C for 2 hours, and (6) 3 revenue at 560 ° C for 1 hour each.
    Example 1
    Two laboratory flows (an example according to the invention: Example 1 and a comparative example according to the application WO2015 / 082342: Comparative Example 1) were developed by the VIM-VAR method according to the composition shown in Table 1 below:
    Table 1
    These two compositions are very similar. The main difference is the W content.
    These two laboratory flows were converted into a 40 mm diameter bar by a 2000T press hot forging process. Bars of diameter 30 mm were machined in the bar and case hardened.
    The cemented bars were treated with (1) heating at 1150 ° C, (2) holding for 15 min at 1150 ° C for austenitization, (3) cooling under a neutral gas at a pressure of 2 bar, (4) a period at room temperature, (5) cooling to -75 ° C for 2 hours, and (6) 3 revenue at 560 ° C for 1 hour each.
    The profiles of surface hardness in HV obtained measured according to the ASTM E384 standard are reported in FIG. 1 with those obtained with 50NL steel (0.12% C-4% Cr-4.2% Mo-3.4% Ni -l% V) having undergone the same treatment.
    The composition according to the invention having a low W content has higher hardness levels, of the order of 860 HV corresponding to 66 H RC. It should also be noted that the drop in the W content relative to the prior art does not significantly affect the hardness level of the base metal which is of the order of 540 HV corresponding to 51 HRC. The steel having the composition according to the invention (low W content) thus makes it possible to obtain higher levels of hardness with a heat treatment limited to 1150 ° C. compared to that of the prior art having a higher content. in W.
    权利要求:
    Claims (17)
    [1" id="c-fr-0001]
    A steel composition comprising, advantageously consisting essentially of, in percentages by weight of the total composition: Carbon: 0.05-0.40, preferably 0.10-0.30; Chromium: 2.50-5.00, preferably 3.00-4.50; Molybdenum: 4.00-6.00; Tungsten: 0.01-1.80, preferably 0.02-1.50; Vanadium: 1.00-3.00, preferably 1.50-2.50; Nickel: 2.00-4.00; Cobalt: 2.00-8.00, preferably 3.00-7.00; Iron: balance as well as unavoidable impurities, optionally further comprising one or more of the following: Niobium: <2.00; Nitrogen: <0.50, preferably <0.20; Silicon: <0.70, preferably 0.05-0.50; Manganese: <0.70, preferably 0.05-0.50; Aluminum: <0.15, preferably <0.10; the combined Niobium + Vanadium content being in the range 1.00-3.50; and the carbon + nitrogen content being in the range 0.05-0.50.
    [2" id="c-fr-0002]
    2. A steel composition according to claim 1, characterized in that it comprises, advantageously in that it consists essentially of, in percentages by weight of the total composition: Carbon: 0.10-0.30, preferably 0.15-0.25; Chromium: 3.00 - 4.50, preferably 3.50 - 4.50; Molybdenum: 4.00-6.00, preferably 4.50-5.50; Tungsten 0.02-1.50, preferably 0.03-1.40; Vanadium: 1.50-2.50; Nickel: 2.00-4.00, preferably 2.50-3.50; Cobalt: 3.00-7.00, preferably 4.00-6.00; Silicon: 0.05-0.50, preferably 0.05-0.30; Manganese: 0.05-0.50, preferably 0.05-0.30; Iron: balance as well as unavoidable impurities, optionally further comprising one or more of the following: Niobium: <2.00; Nitrogen: <0.20; Aluminum: <0.10; the combined Niobium + Vanadium content being in the range 1.00-3.50; and the carbon + nitrogen content being in the range 0.05-0.50.
    [3" id="c-fr-0003]
    3. Steel composition according to any one of claims 1 or 2, characterized in that it comprises at most 1% by weight of unavoidable impurities, preferably at most 0.5% by weight relative to the total weight of the composition.
    [4" id="c-fr-0004]
    4. A steel composition according to any one of claims 1 to 3, characterized in that the unavoidable impurities are selected from titanium, sulfur, phosphorus, copper, tin, lead, oxygen and their mixtures.
    [5" id="c-fr-0005]
    5. Steel composition according to any one of claims 1 to 4, characterized in that the tungsten content is in the range 0.03-1.40, preferably in the range 0.04-1.30 in percentages by weight of the total composition.
    [6" id="c-fr-0006]
    6. A steel composition according to any one of claims 1 to 5, characterized in that it is cementable.
    [7" id="c-fr-0007]
    7. A steel composition according to any one of claims 1 to 6, characterized in that it has, after a thermochemical treatment, preferably carburizing or nitriding or carbonitriding or carburizing and nitriding, followed by a heat treatment, a superficial hardness greater than or equal to 64 H RC, advantageously greater than or equal to 65 H RC.
    [8" id="c-fr-0008]
    8. A steel composition according to any one of claims 1 to 7, characterized in that it has, after a thermochemical treatment, preferably carburizing or nitriding or carbonitriding or carburizing and nitriding, followed by a heat treatment, a martensitic structure having a residual austenite content of less than 10% and free from ferrite and pearlite.
    [9" id="c-fr-0009]
    9. A steel composition according to any one of claims 7 or 8, characterized in that the heat treatment comprises a dissolution at a temperature between 1100 ° C-1160 ° C followed by quenching with possibly cooling to a temperature below -40 ° C and several incomes, advantageously at least three incomes, at a temperature above 500 ° C.
    [10" id="c-fr-0010]
    10. A method of manufacturing a steel blank having the composition according to any one of claims 1 to 9, characterized in that it comprises: a) a step of forming the steel; (b) a step of processing the steel; c) a thermochemical treatment; d) and a heat treatment.
    [11" id="c-fr-0011]
    11. Manufacturing process according to claim 10, characterized in that step c) consists of a carburizing treatment or nitriding or carbonitriding or carburizing and then nitriding, advantageously it is a cementation treatment.
    [12" id="c-fr-0012]
    12. The manufacturing method according to any one of claims 10 or 11, characterized in that step d) comprises dissolving at a temperature between 1100oC-1160 ° C, preferably 1150 ° C, followed by maintaining at this temperature until complete austenitization with optionally cooling at a temperature below -40 ° C, preferably -75 ° C, and several incomes, preferably at least three incomes, at a temperature above 500 ° C, advantageously 560 ° C.
    [13" id="c-fr-0013]
    13. The manufacturing method according to any one of claims 10 to 12, characterized in that step b) consists of a rolling step, forging and / or spinning.
    [14" id="c-fr-0014]
    14. Manufacturing process according to any one of claims 10 to 13, characterized in that the step a) of elaboration is implemented by a conventional process of elaboration oven arc refining and reflow slag conductor (ESR ), or by a VIM-VAR process, possibly with a conductive slag remelting step (ESR) and / or under vacuum (VAR), or by powder metallurgy such as gas atomization and hot isostatic compaction compression (HIP). ).
    [15" id="c-fr-0015]
    15. Steel blank obtainable by a process according to any one of claims 10 to 14.
    [16" id="c-fr-0016]
    16. Use of a blank according to claim 15 or a steel composition according to any one of claims 1 to 9 for the manufacture of a mechanical member, preferably a bearing.
    [17" id="c-fr-0017]
    Mechanical member, advantageously a bearing or a gear, made of steel having the composition according to any one of claims 1 to 9 or obtained from a steel blank according to claim 15.
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    同族专利:
    公开号 | 公开日
    FR3052789B1|2018-07-13|
    EP3472363A1|2019-04-24|
    US10865457B2|2020-12-15|
    CN109790594A|2019-05-21|
    JP2019522732A|2019-08-15|
    US20190338383A1|2019-11-07|
    WO2017216500A1|2017-12-21|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    GB2370281A|2000-10-27|2002-06-26|Nippon Piston Ring Co Ltd|Iron-based sintered alloy for valve seats|
    US20040187972A1|2003-03-24|2004-09-30|Kozo Ozaki|Low alloy high speed tool steel having constant toughness|
    WO2015082342A1|2013-12-02|2015-06-11|Erasteel|A steel alloy and a component comprising such a steel alloy|CN110216429A|2019-04-30|2019-09-10|兴化市统一齿轮有限公司|A kind of automobile gearbox gear and its manufacturing method|
    CN112828292A|2021-01-05|2021-05-25|西安交通大学|Powder metallurgy duplex gear manufacturing and processing method|JP2004169177A|2002-11-06|2004-06-17|Daido Steel Co Ltd|Alloy tool steel, its manufacturing method, and die using it|
    CN102226254B|2011-06-10|2013-03-20|钢铁研究总院|High-strength high-toughness anticorrosion high-temperature bearing/pinion steel and preparation method thereof|
    CN102242316B|2011-06-29|2012-10-10|江苏环立板带轧辊有限公司|H13 die steel and preparation method thereof|FR3078978B1|2018-03-14|2020-03-13|Aubert & Duval|STEEL COMPOSITION|
    CN108588633A|2018-05-21|2018-09-28|江苏万力机械股份有限公司|A kind of medium temperature gas nitrocarburizing quenching technical|
    CN110423955B|2019-07-29|2020-10-20|中国航发北京航空材料研究院|Surface layer super-hardening type super-strength heat-resistant gear bearing steel and preparation method thereof|
    CN113249680B|2021-05-13|2022-01-11|江苏新合益机械有限公司|Surface treatment method of high-strength corrosion-resistant precision piston rod|
    法律状态:
    2017-06-28| PLFP| Fee payment|Year of fee payment: 2 |
    2017-12-22| PLSC| Search report ready|Effective date: 20171222 |
    2018-06-26| PLFP| Fee payment|Year of fee payment: 3 |
    2020-06-19| PLFP| Fee payment|Year of fee payment: 5 |
    2021-04-23| TP| Transmission of property|Owner name: AUBERT & DUVAL, FR Effective date: 20210316 |
    2021-06-22| PLFP| Fee payment|Year of fee payment: 6 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1655664|2016-06-17|
    FR1655664A|FR3052789B1|2016-06-17|2016-06-17|STEEL COMPOSITION|FR1655664A| FR3052789B1|2016-06-17|2016-06-17|STEEL COMPOSITION|
    US16/310,267| US10865457B2|2016-06-17|2017-06-16|Steel composition|
    PCT/FR2017/051584| WO2017216500A1|2016-06-17|2017-06-16|Steel composition|
    JP2019518154A| JP2019522732A|2016-06-17|2017-06-16|Steel composition|
    EP17737334.7A| EP3472363A1|2016-06-17|2017-06-16|Steel composition|
    CN201780047104.XA| CN109790594A|2016-06-17|2017-06-16|Steel compositions|
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