CN117684095A - 900 MPa-grade hot-rolled high-strength steel and preparation method thereof - Google Patents
900 MPa-grade hot-rolled high-strength steel and preparation method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 100
- 239000010959 steel Substances 0.000 title claims abstract description 100
- 238000002360 preparation method Methods 0.000 title abstract description 9
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims abstract description 22
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 16
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 12
- 229910052726 zirconium Inorganic materials 0.000 claims abstract description 12
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 11
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 11
- 239000012535 impurity Substances 0.000 claims abstract description 10
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 10
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 9
- 238000005096 rolling process Methods 0.000 claims description 58
- 239000010936 titanium Substances 0.000 claims description 36
- 229910001566 austenite Inorganic materials 0.000 claims description 30
- 229910000859 α-Fe Inorganic materials 0.000 claims description 19
- 238000010438 heat treatment Methods 0.000 claims description 17
- 239000000126 substance Substances 0.000 claims description 17
- 238000009749 continuous casting Methods 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 15
- 238000007670 refining Methods 0.000 claims description 12
- 238000001953 recrystallisation Methods 0.000 claims description 11
- 238000001816 cooling Methods 0.000 claims description 9
- 229910052799 carbon Inorganic materials 0.000 claims description 8
- 230000008569 process Effects 0.000 claims description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 238000003723 Smelting Methods 0.000 claims description 6
- 230000009466 transformation Effects 0.000 claims description 5
- 238000004804 winding Methods 0.000 claims description 5
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 229910001200 Ferrotitanium Inorganic materials 0.000 claims description 3
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 3
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 238000007664 blowing Methods 0.000 claims description 3
- 238000007872 degassing Methods 0.000 claims description 3
- 230000009286 beneficial effect Effects 0.000 abstract description 6
- 239000000463 material Substances 0.000 abstract description 3
- 230000002787 reinforcement Effects 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 26
- 238000001556 precipitation Methods 0.000 description 14
- 229910000742 Microalloyed steel Inorganic materials 0.000 description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 239000013078 crystal Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 238000005098 hot rolling Methods 0.000 description 4
- 238000005728 strengthening Methods 0.000 description 4
- 239000002131 composite material Substances 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- NDUKHFILUDZSHZ-UHFFFAOYSA-N [Fe].[Zr] Chemical compound [Fe].[Zr] NDUKHFILUDZSHZ-UHFFFAOYSA-N 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 238000005242 forging Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000006698 induction Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000003303 reheating Methods 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 229910020018 Nb Zr Inorganic materials 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 229910001563 bainite Inorganic materials 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- RCFVMJKOEJFGTM-UHFFFAOYSA-N cerium zirconium Chemical compound [Zr].[Ce] RCFVMJKOEJFGTM-UHFFFAOYSA-N 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 230000016507 interphase Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
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- 230000001737 promoting effect Effects 0.000 description 1
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- 238000005204 segregation Methods 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
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Abstract
The invention discloses 900 MPa-grade hot-rolled high-strength steel and a preparation method thereof, and belongs to the technical field of hot-rolled high-strength steel. The hot-rolled high-strength steel comprises the following components in percentage by weight: 0.05 to 0.20 percent of Si, 1.60 to 2.00 percent of Mn, 0.090 to 0.130 percent of Ti, 0.020 to 0.040 percent of Nb, 0.020 to 0.040 percent of Zr, 0.010 to 0.060 percent of Als, less than or equal to 0.020 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.0050 percent of N, 7.6 to 7.6 percent of CTi/4+ (Nb+Zr)/7.6+0.02 percent of Ti/4+ (Nb+Zr), and the balance of Fe and impurities. The invention solves the technical problem of controlling the size and the quantity of the liquid-out TiN in the Ti microalloyed high-strength steel while realizing high reinforcement, and is beneficial to improving the forming performance of the material.
Description
Technical Field
The invention belongs to the technical field of hot-rolled high-strength steel, relates to a production method of high-strength hot-continuous-rolled steel, and in particular relates to 900 MPa-level hot-rolled high-strength steel and a preparation method thereof.
Background
In recent years, with the improvement of the smelting capability of high-purity molten steel, ti microalloying technology is widely applied to steel grade development. The Ti microalloyed steel has the advantages of high precipitation strengthening increment and low alloy price, but has the problem of easy formation of liquid-out TiN inclusion, and meanwhile, the effect of Ti on inhibiting austenite recrystallization is inferior to that of Nb, so that the grain uniformity and the grain refinement degree of the Ti microalloyed steel are inferior to those of Nb-containing steel. Recent research results show that Zr applied to Ti microalloyed steel can improve TiN morphology, reduce TiN quantity, reduce austenite recrystallization temperature, promote grain refinement and improve grain uniformity. The addition of Zr can improve the problem of forming cracking due to liquation of TiN, uneven crystal grains, and the like in Ti microalloyed steel, in response to the usability.
Through retrieval, CN 110684930A discloses low-temperature high-toughness cerium-zirconium composite treatment FH40 ship plate steel and a preparation method thereof, wherein the steel comprises the following chemical components in percentage by mass: 0.04 to 0.08 percent of C,0.2 to 0.4 percent of Si,1.4 to 1.7 percent of Mn, less than or equal to 0.012 percent of P, less than or equal to 0.005 percent of S, 0.020 to 0.055 percent of Nb,0.01 to 0.02 percent of Ti,0.025 to 0.060 percent of V,0.20 to 0.35 percent of Ni,0.01 to 0.04 percent of Al,0.01 to 0.04 percent of Ce,0.01 to 0.03 percent of Zr and the balance of Fe and unavoidable impurities; the preparation method comprises the following steps: preparing raw materials and smelting the raw materials into billets; forging to obtain a forging stock; rolling; cooling to steel. The obtained steel plate structure is ferrite and bainite, the yield strength is more than or equal to 435MPa, the tensile strength is more than or equal to 530MPa, the elongation after fracture is more than or equal to 22.4%, and the low-temperature impact energy at minus 60 ℃ is more than or equal to 244J.
From the above, zr added in the steel in the prior patent mainly plays roles of improving purity of molten steel, reducing O activity in molten steel, reducing inclusions and the like, and no report on control and microstructure regulation of liquid separation TiN by Zr is found.
Disclosure of Invention
Aiming at the technical problems, the invention aims to provide 900 MPa-level hot-rolled high-strength steel and a preparation method thereof.
The technical scheme adopted for solving the technical problems is as follows: the 900 MPa-grade hot rolled high-strength steel comprises the following chemical components in percentage by weight: 0.05 to 0.20 percent of Si, 1.60 to 2.00 percent of Mn, 0.090 to 0.130 percent of Ti, 0.020 to 0.040 percent of Nb, 0.020 to 0.040 percent of Zr0.020 to 0.040 percent of Als 0.010 to 0.060 percent of Als, less than or equal to 0.020 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.0050 percent of N, 7.6 to 7.6 percent of CTi/4+ (Nb+Zr)/7.6+0.02 percent of Fe and unavoidable impurity elements.
The 900 MPa-grade hot rolled high-strength steel comprises the following chemical components in percentage by weight: 0.05 to 0.10 percent of Si, 1.80 to 2.00 percent of Mn, 0.100 to 0.120 percent of Ti, 0.030 to 0.040 percent of Nb, 0.030 to 0.040 percent of Zr, 0.030 to 0.050 percent of Als, less than or equal to 0.015 percent of P, less than or equal to 0.003 percent of S, less than or equal to 0.0040 percent of N, 0.04 to 0.06 percent of C, and the balance of Fe and unavoidable impurity elements.
The yield strength of the 900 MPa-grade hot rolled high-strength steel is more than or equal to 800MPa, the tensile strength is more than or equal to 900MPa, and the elongation is more than or equal to 12%; the microstructure is ferrite, the average grain size of ferrite is less than or equal to 10 mu m, the average grain size of original austenite is less than or equal to 30 mu m, and the number density of liquid-separated TiN inclusion is not higher than 30 pieces/mm 2 The size is not higher than 10 μm.
The preparation method of the 900 MPa-level hot rolled high-strength steel comprises the following steps: and (3) smelting by a converter, LF refining, RH refining and continuous casting to obtain a continuous casting blank, and heating the continuous casting blank, rough rolling, finish rolling, laminar cooling and coiling to obtain a finished steel plate.
In the RH refining process, zirconium iron or zirconium sponge is added after RH vacuum circulation degassing, ferrotitanium or titanium sponge is added, and argon blowing treatment is performed.
Further, in the continuous casting step, the thickness of the continuous casting billet is 200 to 250mm.
Further, in the slab heating process, the heating temperature of the steel slab is 1230-1280 ℃; further, the heating temperature of the steel slab is 1250-1270 ℃.
Further, in the rough rolling process, 5-6 times of rough rolling are adopted, and the thickness of the intermediate billet after rough rolling is 30-60 mm; further, the thickness of the intermediate billet after rough rolling is 34-58 mm.
Further, in the finish rolling step, 6 to 7 passes of rolling are adopted, and the finish rolling start temperature is not higher than the austenite recrystallization termination temperature T nr ，T nr (℃)＝887+464C+(6445Nb-644Nb 1/2 )+(732V-230V 1/2 ) +890Ti+363Al-357Si; further, the finish rolling start temperature is 1030 to 1060 ℃.
Further, in the finish rolling step, the finish rolling finishing temperature is not lower than the ferrite initial transformation temperature A r3 ，A r3 (℃)＝5/9{1670-558[C+(Mn+Mo)/3.875+Cu/15.5+Cr/20.67+Ni/5.636]+16[(FPT/25.4)-0.315]-32}, wherein FPT is the thickness of the finish rolled steel sheet, and is 2-10 mm; further, the finish rolling temperature is 880 to 920 ℃.
Further, in the winding step, the winding temperature is 570 to 630 ℃, and further, the winding temperature is 580 to 620 ℃.
The beneficial effects of the invention are as follows: the steel provided by the invention solves the technical problem of controlling the size and the quantity of the liquid-out TiN in the Ti microalloyed high-strength steel while realizing high reinforcement, and is beneficial to improving the forming performance of the material. The steel provided by the invention reduces the austenite recrystallization temperature through Ti-Zr-Nb composite microalloying, realizes the refinement of austenite grain size, improves the mixed crystal structure of the Ti microalloyed steel, and is beneficial to improving the forming performance of the material. The Ti-Zr-Nb composite microalloying technology and the rolling and cooling control technology provided by the invention can be popularized to other high-strength steel types.
Drawings
FIG. 1 is a microstructure of the steel of example 1 of the present invention;
FIG. 2 is a prior austenite structure of the steel of example 1 of the present invention;
FIG. 3 shows the liquid-out TiN inclusion of the steel of example 1 of the present invention;
FIG. 4 is a microstructure of the steel of example 2 of the present invention;
FIG. 5 is a microstructure of the steel of example 3 of the present invention;
FIG. 6 is a microstructure of the steel of comparative example 1 of the present invention;
FIG. 7 is a drawing of a liquid out TiN inclusion of the steel of comparative example 1 of the present invention;
FIG. 8 is a microstructure of the steel of comparative example 2 of the present invention;
FIG. 9 is a microstructure of the steel of comparative example 3 of the present invention;
FIG. 10 is a prior austenite structure of the steel of comparative example 3 of the present invention.
Detailed Description
The technical scheme of the invention can be implemented in the following way.
The 900 MPa-grade hot rolled high-strength steel comprises the following chemical components in percentage by weight: 0.05 to 0.20 percent of Si, 1.60 to 2.00 percent of Mn, 0.090 to 0.130 percent of Ti, 0.020 to 0.040 percent of Nb, 0.020 to 0.040 percent of Zr, 0.010 to 0.060 percent of Als, less than or equal to 0.020 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.0050 percent of N, 7.6 to 7.6 percent of Ti/4+ (Nb+Zr)/7.6+0.02 percent of C, and the balance of Fe and unavoidable impurity elements.
The 900 MPa-grade hot rolled high-strength steel comprises the following chemical components in percentage by weight: 0.05 to 0.10 percent of Si, 1.80 to 2.00 percent of Mn, 0.100 to 0.120 percent of Ti, 0.030 to 0.040 percent of Nb, 0.030 to 0.040 percent of Zr, 0.030 to 0.050 percent of Als, less than or equal to 0.015 percent of P, less than or equal to 0.003 percent of S, less than or equal to 0.0040 percent of N, 0.04 to 0.06 percent of C, and the balance of Fe and unavoidable impurity elements.
The yield strength of the 900 MPa-grade hot rolled high-strength steel is more than or equal to 800MPa, the tensile strength is more than or equal to 900MPa, and the elongation is more than or equal to 12%; the microstructure is ferrite, the average grain size of ferrite is less than or equal to 10 mu m, the average grain size of original austenite is less than or equal to 30 mu m, and the number density of liquid-separated TiN inclusion is not higher than 30 pieces/mm 2 The size is not higher than 10 μm.
The reasons for the limitation of the main alloying elements in the steel according to the invention will be explained below.
Mn has the functions of solid solution strengthening and toughness improvement in steel, and the content of Mn element is properly improved, so that the toughness of the steel can be improved, but when the content of Mn is too high, casting blank segregation is easily caused, and the uniformity of a structure is affected, so that the content of Mn is controlled to be 1.60-2.00%.
Ti can be combined with C element in steel to form nano TiC precipitated phase, which can play a strong role in precipitation strengthening, and meanwhile, ti can inhibit coarsening of original austenite structure in the slab reheating process, thereby being beneficial to grain refinement. However, the Ti content should not be too high to form large-size, high-density liquid-out TiN inclusions. Therefore, in the present invention, in order to increase the tensile strength of steel to 900MPa or more, a relatively high content of Ti is added, and the Ti content is controlled to be 0.090 to 0.130%.
Nb can raise the end temperature of austenite recrystallization, and is favorable for rolling in the non-recrystallized region of austenite at higher finish rolling start temperature, thereby promoting the flattening of austenite and refining the final ferrite structure. In the present invention, the Nb content is controlled to be 0.020 to 0.040%.
Zr is the same-family element of Ti and has slightly active chemical property than Ti, so that Zr is added into the steel to form ZrN with N, thereby reducing the size and quantity of liquid-out TiN, simultaneously, zr can also improve the austenite recrystallization activation energy of the Ti microalloyed steel, promote the refinement of original austenite structure and lighten the mixed crystal structure which is easy to occur in the Ti microalloyed steel. In addition, zr and C are combined to form nano ZrC particles, so that the precipitation strengthening effect can be achieved. In the present invention, the Zr content is controlled to be 0.020 to 0.040%.
The impurity elements such as P, S, N can deteriorate the toughness and plasticity of steel, increase the number of inclusions, and simultaneously S, N can form Ti4S2C2, tiN and other inclusions with Ti element, so that the content of P, S, N is controlled to be less than or equal to 0.020%, less than or equal to 0.005% and less than or equal to 0.0050% respectively.
The C element is combined with strong carbide forming elements such as Nb, ti, zr and the like to form a nano MC (NbC, tiC, zrC) precipitated phase, which is beneficial to improving the strength of steel, but when the C content is higher, an M3C (alloy cementite) phase is formed at a higher temperature, and is easy to gather at a grain boundary, so that the toughness and plasticity of the steel are affected, the nano MC precipitated phase is reduced, and the strength of the steel is reduced. Therefore, in the present invention, the C content is controlled to be Ti/4+ (Nb+Zr)/7.6 to Ti/4+ (Nb+Zr)/7.6+0.02% according to the stoichiometric ratio with Nb, ti and Zr.
The preparation method of the 900 MPa-level hot rolled high-strength steel comprises the following steps: and (3) smelting by a converter, LF refining, RH refining and continuous casting to obtain a continuous casting blank, and heating the continuous casting blank, rough rolling, finish rolling, laminar cooling and coiling to obtain a finished steel plate.
Further, after RH vacuum circulation and degassing, adding zirconium iron or sponge zirconium, adding ferrotitanium or sponge titanium, and then carrying out argon blowing treatment.
Further, the thickness of the continuous casting billet of the steel is 200-250 mm.
Further, the heating temperature of the slab is 1230 to 1280 ℃, preferably 1250 to 1270 ℃.
Further, the steel slab is rough rolled for 5 to 6 times, and the thickness of the intermediate slab after rough rolling is 30 to 60mm, preferably 34 to 58mm.
Further, the steel is finish-rolled in 6 to 7 passes, and the finish-rolling start temperature is not higher than the austenite recrystallization termination temperature T nr Wherein T is nr (DEGC) =887+464C+ (6445 Nb-644Nb 1/2) + (732V-230V 1/2) +890Ti+363Al-357Si. Preferably, the finish rolling inlet temperature is 1030-1060 ℃, and the finish rolling finishing temperature is not lower than the ferrite initial transformation temperature A r3 Wherein A is r3 (℃)＝5/9{1670-558[C+(Mn+Mo)/3.875+Cu/15.5+Cr/20.67+Ni/5.636]+16[(FPT/25.4)-0.315]-32}, wherein the FPT is the thickness of the finish rolled steel plate and is 2-10 mm. Preferably, the finish rolling temperature is 880 to 920 ℃.
Further, the steel is subjected to laminar cooling after finish rolling, and the coiling temperature is 570 to 630 ℃, preferably 580 to 620 ℃.
The reasons for the limitation of the production process of the steel according to the present invention will be explained.
As mentioned above, zr has more active chemical property than Ti, and in order to control the quantity and size of the liquid-separated TiN inclusion, zr and Ti should be added after vacuum circulation, and Zr and Ti should be added first, so as to achieve the purpose of reducing N content and liquid-separated TiN.
In order to promote the sufficient solid solution of the microalloy elements such as Mn, nb, ti, zr and improve the strength of steel, a high slab heating temperature is adopted, but when the heating temperature is too high, austenite grains are coarse instead. Therefore, the slab reheating temperature is controlled to 1230-1280 ℃.
In order to ensure austenite grain refinement, the finish rolling process generally requires a compression ratio of not less than 5 to ensure sufficient austenite flattening and provide sufficient nucleation sites for subsequent ferrite transformation, thereby refining the grains. The thickness of the finished steel plate after finish rolling is 2-10 mm, and the thickness of the intermediate billet after rough rolling is controlled to be 30-60 mm according to different thicknesses of the finished steel plate to ensure that the compression ratio is more than or equal to 5.
In the finish rolling process, the rolling of the non-recrystallized region should be increased as much as possible in order to refine grains and improve strength, which requires that the finish rolling temperature be lower than the austenite recrystallization termination temperature T nr According to the empirical formula T nr (DEGC) =887+464C+ (6445 Nb-644Nb 1/2) + (732V-230V 1/2) +890Ti+363Al-357Si, and bringing the mass percentages of the chemical components of the steel into a formula to obtain T nr About 1069 deg.C, the initial temperature of finish rolling is controlled between 1030-1060 deg.C.
The finish rolling temperature is generally controlled to be at ferrite initial transformation temperature A r3 Above, according to the empirical formula A r3 (℃)＝5/9{1670-558[C+(Mn+Mo)/3.875+Cu/15.5+Cr/20.67+Ni/5.636]+16[(FPT/25.4)-0.315]-32}, bringing the mass percentages of the chemical components of the steel of the invention into a formula to obtain A r3 About 750 ℃. Meanwhile, in order to reduce deformation induction precipitation in the finish rolling process, interphase precipitation and ferrite supersaturation precipitation in the laminar cooling and coiling processes are increased, tiC precipitation effect increment is improved, and strength of steel is improved, and the finish rolling temperature is properly increased, so that the finish rolling temperature is controlled to 880-920 ℃.
The temperature of the nose point of supersaturation precipitation of TiC in ferrite is about 600 ℃, and in order to promote precipitation of a second phase and improve the strength of steel, the coiling temperature is controlled to be about 600 ℃, specifically 570-630 ℃. The technical scheme and effect of the present invention will be further described by practical examples.
Examples
The 900 MPa-level hot rolled high-strength steel comprises the following chemical components in percentage by weight: si 0.05-0.20%, mn 1.60-2.00%, ti 0.090-0.130%, nb 0.020-0.040%, zr 0.020-0.040%, als 0.010-0.060%, P less than or equal to 0.020%, S less than or equal to 0.005%, N less than or equal to 0.0050%, CTi/4+ (Nb+Zr)/7.6-Ti/4+ (Nb+Zr)/7.6+0.02%, and the balance Fe and unavoidable impurity elements. Table 1 shows the specific chemical compositions of examples 1-3 and comparative examples 1-3 according to the present invention.
TABLE 1 chemical composition/%
| C | Si | Mn | P | S | Ti | Nb | Zr | Als | N | |
| Example 1 | 0.04 | 0.16 | 1.62 | 0.018 | 0.002 | 0.125 | 0.028 | 0.035 | 0.033 | 0.0035 |
| Example 2 | 0.05 | 0.09 | 1.83 | 0.009 | 0.005 | 0.110 | 0.030 | 0.039 | 0.029 | 0.0031 |
| Example 3 | 0.06 | 0.05 | 1.95 | 0.011 | 0.003 | 0.095 | 0.035 | 0.028 | 0.040 | 0.0028 |
| Comparative example 1 | 0.05 | 0.08 | 1.78 | 0.010 | 0.002 | 0.130 | 0.021 | / | 0.032 | 0.0040 |
| Comparative example 2 | 0.10 | 0.10 | 1.88 | 0.015 | 0.004 | 0.080 | 0.035 | 0.034 | 0.045 | 0.0021 |
| Comparative example 3 | 0.05 | 0.12 | 1.91 | 0.008 | 0.003 | 0.112 | / | 0.035 | 0.038 | 0.0026 |
The production process flow of the embodiment and the comparative example of the invention is as follows: and (3) smelting by a converter, LF refining, RH refining and continuous casting to obtain a continuous casting blank, and heating by a plate blank heating furnace, rough rolling, finish rolling, laminar cooling and coiling to obtain a finished steel plate. The hot rolling process parameters are shown in Table 2.
Table 2 process parameters
| Process for producing a solid-state image sensor | Example 1 | Example 2 | Example 3 | Comparative example 1 | Comparative example 2 | Comparative example 3 |
| Slab heating temperature/°c | 1265 | 1258 | 1244 | 1261 | 1225 | 1251 |
| Thickness/mm of intermediate blank | 55 | 48 | 40 | 52 | 38 | 45 |
| Thickness/mm of finished product | 10 | 6 | 2 | 8 | 3 | 10 |
| Finish rolling start temperature/mm | 1031 | 1036 | 1045 | 1032 | 1070 | 1035 |
| Finish rolling finishing temperature/°c | 885 | 906 | 914 | 855 | 880 | 895 |
| Coiling temperature/. Degree.C | 575 | 603 | 618 | 606 | 635 | 590 |
Table 3 shows the mechanical properties and microstructure index of the steels of the examples and comparative examples of the present invention. The yield strength of the finished steel plate is more than 800MPa,the tensile strength is greater than 900MPa, the elongation is greater than 12%, the microstructure is ferrite, the average grain size of ferrite is less than or equal to 10 mu m, the average grain size of original austenite is less than or equal to 30 mu m, and the number density of liquid-separated TiN inclusion is not higher than 30/mm 2 The size is not higher than 10 μm.
TABLE 3 mechanical Properties
| Performance index | Example 1 | Example 2 | Example 3 | Comparative example 1 | Comparative example 2 | Comparative example 3 |
| Thickness/mm of finished product | 10 | 6 | 2 | 8 | 3 | 10 |
| Yield strength/MPa | 836 | 843 | 854 | 792 | 806 | 811 |
| Tensile strength/MPa | 925 | 941 | 948 | 884 | 891 | 903 |
| Elongation/% | 20 | 21 | 20 | 18 | 21 | 20 |
| Original austenite grain size/. Mu.m | 15 | 16 | 19 | 18 | 22 | 32 |
| Ferrite grain size/. Mu.m | 8 | 7 | 6 | 11 | 9 | 12 |
| Liquid separation TiN number density/mm-2 | 12 | 11 | 15 | 38 | 22 | 25 |
Fig. 1 to 3 show a microstructure diagram, a prior austenite structure diagram and a liquid-out TiN inclusion morphology diagram of the test steel corresponding to the example 1. Fig. 4 and 5 are microstructure diagrams of test steels corresponding to example 2 and example 3.
Zr is not added in the steel of comparative example 1, the finish rolling temperature is slightly lower than 855 ℃ (880-920 ℃ is required), and the contents of the other chemical components and the hot rolling process parameters meet the requirements of the invention. Since no Zr was added, the comparative example 1 steel had a liquid-out TiN number density higher than 30 pieces/mm 2, and the liquid-out TiN morphology exhibited a remarkable angular shape. The final rolling temperature of finish rolling is lower, so that the deformation induction precipitation of the finished steel is increased, the ferrite supersaturation precipitation is reduced, and the yield strength and the tensile strength of the steel of comparative example 1 are lower.
The comparative example 2 steel has lower Ti content, lower slab heating temperature, higher coiling temperature, and other chemical components and hot rolling process parameters meeting the requirements of the invention. The strength of the steel of comparative example 2 was low because the Ti element in solid solution was reduced due to the lower Ti content and the lower slab heating temperature, the precipitation of the titanium-containing second phase precipitated after laminar cooling was reduced, and the second phase precipitation was reduced even when the nose temperature of the second phase precipitation was around 600 c and the coiling temperature was higher (635 c).
The steel of comparative example 3 is free from adding Nb, the thickness of the intermediate billet is lower, and the content of the rest chemical components and the hot rolling process parameters meet the requirements of the invention. Since Nb can promote rolling of steel in an austenite unrecrystallized region by increasing the austenite recrystallization temperature and promote austenite flattening, the prior austenite grains of the comparative example 3 steel to which Nb is not added are slightly coarser than those of the examples, and at the same time, since the intermediate billet thickness is lower, the austenite recrystallization degree of the comparative example 3 steel is lower than that of the examples, and thus the finished microstructure of comparative example 3 has a mixed crystal structure and the grain size is coarser than that of the examples.
Claims (10)
- The hot rolled high-strength steel of 1.900MPa grade is characterized by comprising the following chemical components in percentage by weight: 0.05 to 0.20 percent of Si, 1.60 to 2.00 percent of Mn, 0.090 to 0.130 percent of Ti, 0.020 to 0.040 percent of Nb, 0.020 to 0.040 percent of Zr, 0.010 to 0.060 percent of Als, less than or equal to 0.020 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.0050 percent of N, 7.6 to 7.6 percent of Ti/4+ (Nb+Zr)/7.6+0.02 percent of C, and the balance of Fe and unavoidable impurity elements.
- 2. The 900 MPa-grade hot-rolled high-strength steel according to claim 1, wherein the chemical components thereof are as follows in weight percent: 0.05 to 0.10 percent of Si, 1.80 to 2.00 percent of Mn, 0.100 to 0.120 percent of Ti, 0.030 to 0.040 percent of Nb, 0.030 to 0.040 percent of Zr, 0.030 to 0.050 percent of Als, less than or equal to 0.015 percent of P, less than or equal to 0.003 percent of S, less than or equal to 0.0040 percent of N, 0.04 to 0.06 percent of C, and the balance of Fe and unavoidable impurity elements.
- 3. 900 MPa-grade hot-rolled high-strength steel according to claim 1 or 2, characterized in that: the yield strength is more than or equal to 800MPa, the tensile strength is more than or equal to 900MPa, and the elongation is more than or equal to 12%; the microstructure is ferrite, the average grain size of ferrite is less than or equal to 10 mu m, the average grain size of original austenite is less than or equal to 30 mu m, and the number density of liquid-separated TiN inclusion is not higher than 30 pieces/mm 2 The size is not higher than 10 μm.
- 4. A method for producing 900 MPa-grade hot-rolled high-strength steel according to any one of claims 1 to 3, characterized in that: and (3) smelting by a converter, LF refining, RH refining and continuous casting to obtain a continuous casting blank, and heating the continuous casting blank, rough rolling, finish rolling, laminar cooling and coiling to obtain a finished steel plate.
- 5. The method for preparing 900 MPa-grade hot-rolled high-strength steel according to claim 4, wherein: at least one of the following is satisfied:in the RH refining process, adding ferrozirconium or zirconium sponge after RH vacuum circulation degassing, adding ferrotitanium or titanium sponge, and then carrying out argon blowing treatment;in the continuous casting process, the thickness of the continuous casting billet is 200-250 mm;in the slab heating procedure, the heating temperature of the steel slab is 1230-1280 ℃;in the rough rolling procedure, 5-6 times of rough rolling are adopted, and the thickness of the intermediate billet after rough rolling is 30-60 mm;in the finish rolling process, 6-7 times of rolling are adopted, and the finish rolling starting temperature is not higher than the austenite recrystallization termination temperature T nr Finish rolling finishing temperature is not lower than ferrite initial transformation temperature A r3 The thickness of the finish rolled steel plate is 2-10 mm;in the winding step, the winding temperature is 570-630 ℃.
- 6. The method for preparing 900 MPa-grade hot-rolled high-strength steel according to claim 5, wherein: the heating temperature of the steel plate blank is 1250-1270 ℃.
- 7. The method for preparing 900 MPa-grade hot-rolled high-strength steel according to claim 5, wherein: the thickness of the intermediate billet after rough rolling is 34-58 mm.
- 8. The method for preparing 900 MPa-grade hot-rolled high-strength steel according to claim 5, wherein:T nr (℃)＝887+464C+(6445Nb-644Nb 1/2 )+(732V-230V 1/2 )+890Ti+363Al-357Si；A r3 (℃)＝5/9{1670-558[C+(Mn+Mo)/3.875+Cu/15.5+Cr/20.67+Ni/5.636]+16[(FPT/25.4)-0.315-32 }, wherein FPT is the thickness of the finish rolled steel sheet.
- 9. The method for preparing 900 MPa-grade hot-rolled high-strength steel according to claim 5, wherein: the initial rolling temperature of the finish rolling is 1030-1060 ℃, and the final rolling temperature of the finish rolling is 880-920 ℃.
- 10. The method for preparing 900 MPa-grade hot-rolled high-strength steel according to claim 5, wherein: the coiling temperature is 580-620 ℃.
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