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    • 专利摘要:
    The present invention provides a steel plate having a low welding crack susceptibility and a yield strength of 800 MPa and a manufacturing method for the same. The steel plate having a low welding crack susceptibility comprises the following chemical components (wt.%: percent by weight): C:0.03-0.08wt.%, Si:0.05-0.70wt.%, Mn:1.30-2.20w.t%, Mo:0.10-0.30wt.%, Nb:0.03-0.10wt.%, V:0.03-0.45wt.%, Ti:0.002-0.040wt.%, Al:0.02-0.04wt.%, B:0.0010-0.0020wt.%, the balance being Fe and unavoidable impurities, and the welding crack susceptibility index meets the following formula: Pcm‰¤0.20%. The theimo-mechanical controlled rolling and cooling processes is used to obtain an ultrafine bainite batten matrix structure, which increases the intensity, plasticity and toughness of the steel plate. The steel plate with a low welding crack susceptibility of the present invention has a yield strength of greater than 800 MPa, a tensile strength of greater than 900 MPa, a Charpy impact energy Akv (-20°C) of no less than 150J and an excellent welding performance.
    公开号:SE535302C2
    申请号:SE0900863
    申请日:2008-10-24
    公开日:2012-06-19
    发明作者:Liandeng Yao；Xiaoting Zhao；Sixin Zhao
    申请人:Baoshan Iron & Steel；
    IPC主号:
    专利说明:

    535 302 is that preheating is not required before welding, or that only a low preheating is needed, without cracks occurring, which mainly solves the problems when welding large steel structures.
    The method of reducing Pcm is to reduce the addition amount of carbon or alloying elements to high strength steels produced by hardening and hardening processes by reducing the addition amount of carbon or alloying elements, however, will inevitably lead to a decrease in the strength of the steel. The use of thermomechanically controlled rolling and cooling processes (TMCP) can overcome this defect.
    In addition, compared to the thermal refining process, thermomechanically controlled rolling and cooling processes (TMCP) can refine the crystal grains, which improves the steel's low temperature toughness.
    At present, the alloying elements of steel with low sensitivity to weld cracks produced by TMCP technology are usually Mn-Ni-Nb-Mo-Ti and Si-Mn-Cr-Mo-Ni-Cu-Nb-Ti-Al-B systems. For example, the chemical substances of a low-alloy, high-strength steel produced by a TMCP process disclosed in International Publication WO99 / 05335 are as follows: (wt.%, Weight percent): C: 0.05-0.10 wt.% , Mn: 1.7 - 2.1 wt.%, Ni: 0.2-1.0 wt.%, Mo: 0.25 - 0.6 wt%, Nb: 0.01-0.10 wt. %, Ti: 0.005-0.03 wt.%, PS0.015 wt.%, SS0.003 wt.%. For example, the chemical components of a carbon bainite steel as described in CN15212285 are as follows: (wt.% By weight): C: 0.01-0.05 wt.%, Si: 0.05-0.5 wt. %, Mn: 1.0 - 2.2 wt.%, Ni: 0.0-1.0 wt.%, Mo: 0.0-0.5 wt.%, Cr: 0.0-0.7 wt.%, Cu: 0.0-1.8 wt.%, Nb: 0.0l-0-0.070 wt.%, Ti: 0.005-0.03 wt.%, B: 0.0005-0.005 wt.%, Al: 0.015-0.07 wt.%. The alloying elements of the steels described above are designed as Mn-Ni-Nb-Mo-Ti and Si-Mn-Cr-Mo-Ni-Cu-Nb-Ti-Al-B systems, respectively. Since Mo and Ni are both precious metals, the production costs for this type of steel sheet are relatively high, with respect to the type and the total amount of addition of added alloying elements. In addition, heat curing is used for both types, which increases the production costs of the steel sheet and its PCM values are relatively high, which has an opposite effect on the welding properties.
    To solve the problems mentioned above, in the present invention a steel with a Si-Mn-Nb-Mo-V-Ti-Al-B system is used, and the inventors have constructed a superfine bainite-woven steel sheet with low sensitivity to welding cracks and a yield strength of 800 MPa, by using the reinforcing effect of V and thermomechanically controlled rolling and cooling processes without thermal refining, giving the produced steel sheet excellent low temperature toughness and weldability.
    OBJECTS OF THE INVENTION The object of the present invention is to provide a steel sheet with low sensitivity to weld cracks and a yield strength of 800 MPa.
    Another object of the invention is to provide a steel sheet manufacturing method with low sensitivity to weld cracks.
    The first aspect. of the present invention is to provide a steel sheet with low sensitivity to weld cracks and a yield strength of 800 MPa, which comprises the following chemical components (wt.%: weight percent): C: 0.03-0.08 wt.%, Si: 0 , 05-0.70 wt.%, Mn: 535 302 1.30-2.20 wt.%, Mo: 0, 10.0.30 wt.%, Nh: 0.03-0.10 wt.% , V.0.03-0.45 wt.%, Ti: 0.002-0.040 wt.%, Al: 0.02-0.04 wt.%, B: 0.0010-0.0020 wt.%, Where the counterweight consists of Fe and unavoidable contaminants and the index value of the sensitivity to weld cracks corresponds to the following formula: Pcm S 0.20%.
    The steel sheet with low sensitivity to welding cracks has a super fine bainite fabric structure.
    The index value Pcm for the sensitivity to weld cracks in the steel sheet with low sensitivity to weld cracks can be determined using the following formula: PCm (%) = C + Si / 30 + Ni / 60 + (Mn + Cr + Cu) / 20 + MO / l5 + V / 10H + 5B.
    The index value for the sensitivity to weld cracks Pcm is an index value that reflects the presence of cold weld cracks. The lower the Pcm value, the better the weldability, and the higher the Pcm value, the worse the weldability. Good weldability refers to a steel that is difficult to generate weld cracks when welding, while poor weldability refers to a steel that easily creates cracks. To prevent cracking, preheating is required and the better the weldability, the lower the preheating temperature is required and vice versa, a higher preheating temperature is required with poorer weldability. According to the provisions of the Chinese Iron Metallurgy Industry Standard YB / T 4137-2005, the PCM value for Q80OCF brand steel should be less than 0.28%. The pcm value of the steel plate with low sensitivity to welding cracks according to this invention is lower than 0.20%, which is in accordance with the provisions of the above-mentioned standard and has an excellent weldability.
    The chemical components of the steel sheet with low sensitivity to weld cracks and a yield strength of 800 MPa are described in detail below. 535,302 ° C; Enlargement of an austenitic area C in a supersaturated ferrite structure created in the hardening process can increase the strength of the steel. However, C has the opposite effect on welding performance. The higher the proportion C, the poorer the welding performance. In the case of bainite steel produced by a TMCP process, the lower the proportion of C, the better its toughness, and a low proportion of C can give a thicker steel sheet with higher toughness and a super fine bainite matrix structure comprising a high density of voids. places in the atomic lattice can be achieved. Therefore, the proportion C in the present invention is controlled to 0.03 to 0.08 wt%.
    Si: Does not form a carbide in the steel, but exists in the bainite, ferrite or austenite in the form of a solid solution, which can increase the strength of the bainite, ferrite or austenite in the steel, and the reinforcing solution effect of Si is stronger than that of Mn, Nb , Cr, W, Mo and V. Si can also reduce the diffusion rate of carbon in the austenite and place the ferritic and perlite C-curve lower to the right of the CCT curve, so that the creation of bainite structures is simplified in the continuous cooling process. No more than 0.70 wt% Si is added to the steel of the invention, which is advantageous for improving the suitable relationship between strength and toughness of the steel.
    Mo: A ferritic element that reduces the austenitic area. Mo, solid dissolved in austenite and ferrite, can increase the strength of the steel, improve the hardenability of the steel and prevent toughened brittleness. Since the present invention does not require treatment by thermal refining, no more than 0.30 wt% of Mo, which is a very expensive substance, is added, thus reducing the cost. Nb: In the present invention, a relatively large amount of Nb is added to achieve two purposes, one being to refine crystal grains and increase the thickness of the steel sheet, and the other object is to increase the non-crystallization temperature. of the steel and simplify the use of a relatively high final rolling temperature in the rolling process, which accelerates the rolling speed and increases the production efficiency.
    In addition, since Nb enhances the grain refining effect, a thicker steel sheet can be produced. In the present invention, 0.03-0.10 wt.% Nb is added to take into account the reinforcing solution effect and the fine-grained reinforcing effect of Nb.
    V: A ferritic formation substance that significantly reduces the austenitic area. V dissolved in an austenite at high temperature can improve the hardenability of the steel. The carbide of V, e.g. The V4C3 steel is relatively stable and can prevent movements of the grain boundary and the growth of the crystal grains.
    V can refine a casting structure of weld metal, reduce the susceptibility to overheating of the welded base material and prevent violent grain growth and grain enlargement near the melting line of the welded base material, which is advantageous for welding performance. In the present invention, 0.03-, 0.45 wt.% V is added to significantly improve the strength of the steel, both V and Cu can play a role in precipitation reinforcement in the steel, but compared to Cu, only an extremely small amount V to achieve the same effect regarding the precipitation gain.
    In addition, since Cu tends to cause grain boundary cracks in the steel, Ni, which is also a very expensive alloy, must be added in an amount equal to at least half the amount, Cu, to avoid these cracks. Replacing Cu with V can therefore significantly reduce the steel's manufacturing costs. 535 302 Ti: A ferritic formation substance which significantly reduces the austenitic area. The carbide of Ti, e.g. TiC, is relatively stable and can prevent the growth of crystal grains. Ti, solid dissolved in austenite is advantageous for improving the hardenability of the steel. Ti can reduce the first type of annealing embrittlement point, e.g. 250- 400 ° C annealing embrittlement point. Since the present invention does not require a thermal refining, the added amount of Ti can be reduced. In the present invention, 0.002-0.040 wt% Ti is added which forms fine carbonitride for precipitation which refines the bainite fabric structure.
    Al: Al can improve the driving force of the phase change from austenite to ferrite and can reduce the phase cycle of austenite in an intense way. Al interacts with PJ in the steel to form fine and diffusive AlN which precipitates and can prevent the growth of the crystal grains so that the goal of refining crystal grains can be achieved and improves the low temperature toughness of the steel. Too high a proportion of Al will have the opposite effect on the steel's hardenability and welding performance. In the present invention, no more than 0.04 wt.% Al is added to refine crystal grains, improve the toughness of the steel and guarantee the welding performance.
    B: B can dramatically increase the hardenability. at the steel. In the present invention, 0.001-0.002 wt.% B is added so that a very strong bainite structure of steel can be easily achieved under certain cooling conditions.
    The second aspect of the present invention is to provide a steel sheet manufacturing method with low sensitivity to weld cracks and a yield strength of 800 MPa, which comprises melting, casting, heating, rolling and cooling processes, in which after the rolling procedure, the steel is subjected to a cooling procedure. without thermal refining.
    In a preferred embodiment, the thickness of the cast, smooth ingot or steel bar is not less than 4 times the thickness of the finished steel sheet.
    In another preferred embodiment, the heating temperature in the heating process is 1050 to 1180 ° C, and the lying time is 120 to 180 minutes.
    In another preferred embodiment, the rolling is divided into the first step of the rolling and the second step of the rolling.
    In another preferred embodiment, the starting temperature for rolling in the first step of rolling is 1050 to 110 ° C, and when the thickness of the rolled piece is two or three times the thickness of the finished sheet, the rolled piece remains on the rolling bed until the temperature reaches 800-860 ° C.
    In another preferred embodiment, the Pass deformation rate in the second rolling step is 10-28%, and the final rolling temperature is 780-840 ° C.
    In another preferred embodiment, in the cooling process, the steel plate is introduced into an accelerated cooling device and cooled at a rate of 15 to 30 ° C / s to a temperature of 350 to 400 ° C, followed by air cooling.
    In another preferred embodiment, the air cooling is performed by cooling in a packed formation or bench cooling.
    In the manufacturing method of a steel sheet with low sensitivity to weld cracks and a yield strength of 800 MPa, the technical control mechanism for the main steps is analyzed as follows: 535 302 _ 9 _ 1. Rolling process When the thickness of the rolled piece reaches a thickness of two to four times the thickness of the finished steel sheet, the rolled piece remains on the roller conveyor until the temperature reaches 800 to 860 ° C. For steels containing Nb, the temperature for non-recrystallization is about 950 to 1050 ° C, and it is first rolled at a relatively high temperature of from 1050 to 110 ° C to produce a certain density of empty sites in the atomic lattice of the austenite. During the relaxation process of lowering the temperature to 800-860 ° C to roll the eel, the interior of the austenitic crystal grains is subjected to a reset and a static recrystallization process so that the austenite crystal grains are refined. During the relaxation process, individual precipitation and complex precipitation of carbonitride take place in Nb, V and Ti. The precipitated carbonitrides attach to the empty space in the atomic lattice and the movement of the sub-grain boundaries, reserve a number of empty spaces in the austenitic crystal grains and provide a variety of nucleation sites for the formation of bainite during the cooling process. Rolling at 800 ~ 860 ° C increases the density of empty sites in the atomic lattice of the austenite and the carbonitride which precipitates at the empty site in the atomic lattice prevents the further movement of the deformed crystal grains. Due to the precipitation effect caused by deformation, a relatively high Pass deformation will facilitate the formation of finer and with diffusive educts. High density of empty sites in the atomic lattice and fine and diffusive educts give a high density of nucleation sites for bainite, and the attachment effect of the second phase particles to the interface of the bainite growth prevents the growth and relocation of the bainite web, which benefits both steel strength and toughness. The final rolling temperature is controlled in the low temperature section of the non-recrystallization area, and at the same time this temperature section is close to the transmission point Ar3, i.e. the final rolling temperature is 780-840 ° C, and by ending the rolling within this temperature range, the defects in the austenite can be increased by increasing the deformation and preventing the recovery, giving a higher energy accumulation for the bainite phase change, without putting too much load on the roll, which is suitable for producing thick sheet metal. 2. Cooling process After the rolling is completed, the steel plate is introduced into an accelerated cooling device and cooled down to 450 to 500 ° C at a cooling rate of 15 to 30 ° C / S. A high cooling rate can prevent the formation of ferrite and perlite and the steel plate directly entering the bainite transition region of the CCT curve. The driving force of the phase change of the bainite can be described with ÅG = AGchem + AGQ where AGdæm is a chemical driving force, AG where a voltage stored energy is caused by defects. Since a high cooling rate causes supercooling of the austenite and increases the driving force of a chemical phase change, AGdæm should be examined in combination. with the voltage stored energy AGd, which is caused in the rolling process to increase the driving force of the bainitic nucleation. Due to the high density of empty sites in the atomic lattice of the crystal grains, the bainitic nucleation sites increase.
    Well considered by combining the thermodynamic and dynamic factors, the bainite can form a core at a very high speed. A high cooling rate makes it possible to quickly complete the bainitic conversion and prevents the bainitic web pattern from coarsening. After the steel plate has left the accelerated cooling device, the steel is cooled in a packed form at 450-550 ° C or air cooled in a cold bed to make the carbide of V in the ferritic precipitate more complete, so that the addition of the precipitation reinforcement to the strength is improved.
    The steel for mechanical equipment with high intensity and iron construction building requirements requires high strength and excellent toughness. A number of factors affect the strength, which can be described by the following formula: c = cf + cp + cgl + cd where of is fine-grained gain; cp is the precipitation reinforcement, Ga is the solid solution reinforcement and od is the reinforcement of empty spaces in the atomic lattice. Thermomechanical. treatment of the steel sheet is usually done with thermomechanically controlled rolling and cooling process (TMCP), which refines the microstructures or forms high intensity structures such as ultrafine bainite by controlling the deformation rate and cooling rate, which improves the steel yield strength. Modified TMCP and Relaxation Precipitation Controlling (RPC) technology creates a stable network of empty spaces in the atomic lattice, diffusive and fine second-phase particles precipitate at the empty space in the atomic lattice and at the sub-core boundary, the bainite tissue is refined by promoting nucleation and its growth and combined effect of reinforcement of empty spaces in the atomic lattice, precipitation reinforcement and fine grain reinforcement is achieved, which increases the strength and toughness of the steel.The most important mechanism is: empty plastics in the atomic lattice are significantly increased in the austenite. Restoration and recrystallization that takes place during rolling refines the original austenite crystal boundaries. After rolling and deformation, empty spaces in the atomic lattice of the crystals will be rearranged during the controlled cooling relaxation. Since a hydrostatic pressure field exists in the empty spaces of the adjacent atomic lattice, atoms filling the gap, such as B, will enrich the empty ones. the sites in the atomic lattice, grain boundaries and sub-grain boundaries, reduce the mobility of the empty spaces in the atomic lattice and finally the high density of empty spaces in the atomic lattice caused by the deformation will develop during the restoration to create a stable network of empty plastics in the atomic lattice. During the relaxation, microalloy substances such as Nb, V, Ti and the like precipitate at the grain boundary, the subgrain boundary and the empty plastics in the atomic lattice in the form of carbonitride with different stoichiometric ratios such as (Nb, V, Ti) x (C, N) y and the like. Second phase particles, such as precipitated carbonitrides, attach to the empty sites in the atomic lattice and sub-grain boundary within the crystal grains and stabilize substructures such as the dislocation wall.
    After the relaxation, the density of empty spaces in the atomic lattice of the austenite is increased by the second phase of the rolling process. After relaxation, when the deformed austenite is cooled accelerated, the effect of the austenite with empty spaces in the atomic lattice and precipitation created by the relaxation process on the following phase transfer can be interpreted as (unlike the fact that no relaxation occurs after the deformation and a lot of empty spaces in atomic lattice precipitates in disorder): first, a sub-grain boundary having a definite orientation difference is a preferred position for nucleation, and if a second phase having an incoherent interface with the matrix precipitates, this will facilitate the nucleation of the new phase 535 302 _ 13 _ nucleation and , after relaxation, a quantity of crystal grains from the new phase will form a core within the original austenite crystal boundaries. Second, because a certain amount of empty plastics in the atomic lattice will move to the sub-grain boundary after relaxation, which to a certain turnover increases the orientation difference between the sub-grains. After the product converted at the intermediate temperature, such as bainite, forms a core at the sub-grain boundary, it is hindered by the anterior sub-grain boundary during growth. When the bainitic ferrite is formed, its phase change interface is contaminated by the carbonitride particles precipitated during the second phase, which prevents its growth. TMCP plus RPC processes form a high density structure of a network of empty sites in the atomic lattice, and the material from the second phase precipitation provides a variety of potential nucleation sites for bainite ferrite nucleation and the fouling effect of the second phase particles on the moving interface and the developed sub-grain boundary prevents the growth of the bainite.
    For this reason, the manufacturing process of the present invention can play a combined role by promoting the nucleation of the bainite and preventing the growth of bainite, which refines the final product.
    FIGURE DESCRIPTION FIG. 1a is a scanning electron microscopic (SEM) micrograph showing the microstructure of the steel sheet with a low sensitivity to weld cracks for the present example 5.
    FIG. lb is an electron transmission microscopic (TEM) micrograph showing the microstructure of the steel sheet with a low sensitivity to weld cracks for the present example 5.
    BEST MODE FOR CARRYING OUT THE PRESENT INVENTION The invention is further illustrated by the following examples in combination with the figures. These examples are intended only to illustrate the best mode of the invention and are not intended to limit the scope of the invention.
    Example 1 The chemicals shown in Table 1 were melted in an electric furnace or converter and cast into a smooth cast iron or steel bar, which was then heated to 110 ° C for 120 minutes and subjected to the first step of rolling in an intermediate thick rolling mill. where the initial rolling temperature in the first rolling step was 1050 ° C, and when the thickness of the rolled piece was 60 mm, it remained in the web until the temperature reached 850 ° C. Then, the second rolling step was performed, in which the Pass deformation rate in the second rolling step was 15-28%, the final rolling temperature was 830 ° C, and the thickness of the finished steel sheet was 20 mm. After the rolling was completed, the steel plate was delivered to an accelerated cooling device (ACC) and cooled to 500 ° C at a cooling rate of 30 ° C / s, followed by cooling in a packed design or in a cold bed.
    Example 2 This example was carried out as Example 1, except that the heating was carried out at 1050 ° C for 240 minutes, where the initial rolling temperature in the first rolling step was 1040 ° C, and the thickness of the rolled piece was 90 mm, the initial rolling temperature in the second the rolling step was 840 ° C, the Pass deformation rate was 15-20%, the final rolling temperature was 81 ° C, and the thickness of the finished steel plate was 30 mm, and the cooling rate of the steel plate was 25 ° C / s and the final temperature was 490 ° C.
    Example 3 This example was carried out as Example 1, except that the heating was performed at 1150 ° C for 150 minutes, where the initial rolling temperature in the first rolling step was 1080 ° C and the thickness of the rolled piece was 120 mm, the initial rolling temperature in the second rolling step was 830 ° C, the Pass deformation rate was 10-15%, the final rolling temperature was 820 ° C, and the thickness of the finished steel sheet was 40 mm, and the cooling rate of the steel sheet was 20 ° C / s and the final temperature was 530 ° C.
    Example 4 This example was carried out as Example 1, except that the heating was carried out at 120 ° C for 180 minutes, where the initial rolling temperature in the first rolling step was 1070 ° C, and the thickness of the rolled piece was 150 mm, the initial rolling temperature in the second the rolling step was 830 ° C, the Pass deformation rate was 10-20%, the final rolling temperature was 800 ° C, and the thickness of the finished steel sheet was 50 mm, and the cooling rate of the steel sheet was 15 ° C / s and the final temperature was 515 ° C.
    Example 5 This example was carried out as Example 1, except that the heating was carried out at 130 ° C for 180 minutes, where the initial rolling temperature in the first rolling step was 1080 ° C, and the thickness of the rolled piece was 150 mm, the the initial rolling temperature in the second rolling step was B40 ° C, the Pass deformation rate was 10-15%, the final rolling temperature was 810 ° C, and the thickness of the finished steel plate was 60 mm, and the cooling plate cooling rate was 15 ° C / s and the final temperature was 480 ° C.
    Example 6 This example was carried out as Example 1, except that the heating was carried out at 120 ° C for 180 minutes, where the initial rolling temperature in the first rolling step was 1,050 ° C, and the thickness of the rolled piece was 120 mm, the initial rolling temperature in the second the rolling step was 820 ° C, the Pass deformation rate was 15-25%, the final rolling temperature was 780 ° C, and the thickness of the finished steel sheet was 40 mm, and the cooling rate of the steel sheet was 20 ° C / s and the final temperature was 540 ° C .
    Table 1. The chemical substances (wt.% Weight percent) and Pcm (%) of the steel sheet with low sensitivity to welding cracks in Examples 1-6 of the present invention Example C Si Mn Nb wt.% V A1 Ti Mo B wtÅ Fe and Pcm in; wt.% wt.% wt.% wt.% wt.% unavoidable impurities wt.% 1 0.04 0.35 1.80 0.070 0.055 0.02 0.015 0.30 0.00lB balance 0.176 2 0.03 0.60 1 .50 0.045 0.45 0.03 0.02 0.22 0.001 balance 0.189 3 0.04 0.40 2.2 0.035 0.10 0.04 0.12 0.10 0.0011 balance 0.186 4 0.05 0.55 1.50 0.040 0.15 0.03 0.01 0.01 0.25 0.0015 balance 0.183 5 0.06 0.05 1.45 0.065 0.30 0.03 0.02 0.20 0.0010 balance 0.183 535 302 _17 ... 6 0.06 0.15 1.30 0.047 0.03 0.02 0.03 0.03 0.25 0.0020 balance 0.180 Test Example 1 The steel plates with low sensitivity to weld cracks in Examples 1-6 of the present invention were tested for their mechanical properties and the results of this are shown in Table 2.
    Table 2 The Mechanical Properties of Steel Sheets Near Low Sensitivity to Weld Cracks in Examples 1-6 of the Present Invention Example Tensile Limit Fracture Limit Elongation (%) -20 ° C Akv (MPa) (MPa) (Longitudinal) (J) 1,840, 950, 17.0, 221.216.224 865 965 16.5 2 850, 960, 15.9, 218.210209 875 970 17.2 3 855, 958, 16.0, 215.2222, 222 860 965 16.0 4 845, 954, 16 , 1, 21l, 208,206 840 950 16.3 5 858, 969, 17, 227, 23l, 224 875 973 17.5 6 859, 967, 17.3, 2l5.21l, 2l9 863 982 17.3 From Table 1 and 2, it can be seen that the Pcm of the steel sheet with a low sensitivity 'to welding cracks of the present invention was S 0.20%, the yield strength was greater than 800 MPa, the yield strength was greater than 90OMPa, and the Charpy impact energy Akv (-20 ° C) was 2l50J, and the plate thickness was up to 60 mm, and that the steel plate had excellent low temperature toughness and weldability.
    Test Example 2 535 302 _18 ..
    The steel sheet with a low sensitivity to weld cracks in Example 1 of the present invention was tested for its weldability (small Tekken test). At an ambient temperature and 50 ° C, no cracks were observed (see Table 3), indicating that the steel sheet of the present invention has excellent welding properties and that no preheating is usually required in welding.
    Table 3 The test results for the weldability of the steel sheet with low sensitivity to cracks from Example 1 of the present invention.
    Test Sample no. Surface cracks Root cracks Cross-sectional ambient Relative temperature in percent, in percent, cracks in temperature humidity%% percent,% l 0 0 0 RT 2 O 0 0 25% 65% 3 0 0 0 50% 4 0 0 0 5 0 0 0 Test Example 3 The low sensitivity steel sheet to cracks in Example 5 of the present invention was studied for its microscopic structure and its scanning electron microscopic (SBM) micrograph and electron transmission microscopic (TEM) micrograph are shown in Figure 1a and Figure 1b, respectively.
    In Figure 1a it can be seen that the bainite fabric has been thinned and that carbide is deposited on the edge of the bainite fabric, and that fine 535 302 _19_ carbide is also deposited on the bainite fabric. In Figure 1b it can be seen that the bainite fabric consists of fine nanoscale bainite fabric.
    In summary, the steel sheet of the present invention has a fine baitin fabric structure and an ultrafine nanoscale bainite fabric substructure. The ultrafine bainite web structure provides fine-grained reinforcing effect, the second phase particles precipitate along the grain boundary of the ultrafine bainite fabric and provide a reinforcing effect of the precipitation, and the structure with empty sites in the atomic lattice within the ultrafine bainite web provides reinforcement of these sites in the atomic nucleus. the strength and toughness of the steel plate of the present invention.
    INDUSTRIAL APPLICABILITY The beneficial effects of the present invention are as follows: 1. The chemical substances are appropriately designed by a significant reduction of the proportion C, partial replacement of Mo with inexpensive alloying substances such as Mn, replacement of the reinforcing effect of the precipitation of Cu with the reinforcing effect of precipitation of fine precipitated particles of carbonitride of V, and no addition of noble substances such as Ni. As a result, the proportion of alloying elements is low, the sensitivity to cracks is low and no preheating is needed before welding. Since the steel sheet of the present invention does not require an additional thermal refining treatment, the manufacturing process is simplified and the manufacturing cost of the steel is reduced. 535 302 _ 20 _ 3. Due to the suitable components and process design regarding the realization effects, the process conditions are relatively simplified and the steel plate can be produced stably in an intermediate production line for thick steel sheet. 4. The yield strength of the steel sheet with low sensitivity to cracks in the present invention is higher than 8OOMPa, the yield strength is higher than 9OOMPa, and the Charpy impact energy Akv (-20 ° C) is> 15 ° C, and the thickness of the sheet is up to 60 mm, the index value for the sensitivity to welding cracks Pcm is 30.20%, and the steel sheet has excellent low temperature toughness and weldability.
    权利要求:
    Claims (11)
    [1] 1. A steel plate having a low welding crack susceptibility and a yíeld strength of 800MPa, wherein the steel plate having a lov: welding crack susceptibility compríses thefollowing chemical components (wt.%: percent by weight):C:0.03-0.08wt.%,Si:0.05-0.70wt.%, Mn:l.30-2.20m.%, Mo:0.l0-0.30wt.%, Nb:0.03-0.10wt.%,V:0.03-0.45wt.%, Ti:0.002-0.040m.%, Al:0.02-0.04wt.%, B:0.00l0-0.0020wt.%, thebalance being Fe and unavoidable impurities, and the welding crack susceptibility indexmeets the following formuia: Pcm$0.20%.
    [2] 2. The steel plate having a low welding crack snsceptibility and a yield strength of800 MPa according to claim l, wherein the steel plate has a superfine baínite battenedstructure.
    [3] 3. A' manufacture method for the steel plate having a low welding cracksusceptibility and a yield strength of '800 MPa according to clairn l, conrprisingsmelting, casting, heating, rolling and coolâng procedures, wherein after rollingprocedure, the steel is subjected to the cooling procedure directly-
    [4] 4. The manufacture method for the steel plate having a low welding cracksusceptibility and a yield strength of 800 MPa according to claim 3, wherein the thicknessof the casted continuous casting billet or steel ingot is not less than 4 times of thethickness of the finished steel plate.
    [5] 5. The manufacrure method for the steel plate having a low welding cracksusceptibility and a yield strength of 800 MPa according to claim 3, wherein the heatingtemperature in the heating process is 1050 to 1180 °C, and the holding time is 120 to 180minutes.
    [6] 6. The manufacture method for the steel plate having a low welding cracksusceptibility and a yíeld strength of 800 MPa according to claim 3, wherein the rolling isdivided into the first stage of rolling and the second stage of roliing.
    [7] 7. The manufacture method for the steel plate having a low welding cracksusceptibility and a yield strength of 800 MPa according to claim 6, wherein in the firststage of rolling, the start rolling temperature is 1050 to 1150 °C, and when the thicknessof the rolled piece reaches twice to four times of that of the finished steel plate, the rolledpiece stays on the roller bed until the temperature reaches 800-860 °C and then issubjected to the second stege of rolling. _
    [8] 8. The manufacture method for the steel plate having a low welding crack _s_usceptibility and a yield strength of 80.0 MPa according to claim 6, wherein the Pass ' Ztctnperatnre is 780-840 °C. dcformhtíon rate in the second stage of rolling is 10-28%, and the finish rolling 'Fåomh sett. emotional To oo4s311o2ø4o i:- 25 H' ' | - .1s-.ruN-29 16:29 mom SPTL gHgNgHglTo ø1a4s3112ta4o P26
    [9] 9. The manufacture method for the steel plate having a low welding cracksusceptibility and a yield strength of 800 MPa according to claim 3", wherein the coolingprocess comprises a forced cooling in an aocelerated cooling device and air cooling, andthe steel plate enters an acoelerated cooling device and is cooïed at a rate of 15 to 30°C/S to a temperature of 350 to 400 °C, and then is air cooled after exiting from theaccelerated cooling device. 10, The manufacture method for the steel plate having a low welding crack susccptibility and a yield strength of 800 MPa according to claim 9, wherein the airoooling is performed by the way of cooling in packad formation or bank eooling. IS
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    同族专利:
    公开号 | 公开日
    CN101418416A|2009-04-29|
    EP2218801B1|2013-05-01|
    EP2218801A1|2010-08-18|
    ZA200901450B|2010-08-25|
    DE112008000562T5|2010-01-28|
    KR20100070310A|2010-06-25|
    US8702876B2|2014-04-22|
    JP5233020B2|2013-07-10|
    ZA200904458B|2010-10-27|
    WO2009056055A1|2009-05-07|
    FI127175B|2017-12-29|
    KR101563929B1|2015-10-28|
    JP2010516895A|2010-05-20|
    US20100032062A1|2010-02-11|
    SE0900863L|2009-07-27|
    FI20095872A|2009-08-25|
    DE112008000562B4|2013-05-29|
    EP2218801A4|2012-02-01|
    ES2424009T3|2013-09-26|
    CN101418416B|2010-12-01|
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    CN2007100941772A|CN101418416B|2007-10-26|2007-10-26|Low welding crack sensitivity steel plate with yield strength of 800MPa grade and method for producing the same|
    PCT/CN2008/072807|WO2009056055A1|2007-10-26|2008-10-24|Steel plate with yield strength of 800mpa grade and low weld cracking sensitivity, and manufacture method thereof|
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