An anti-hydrogen embrittlement cold-rolled DH1200 steel plate and its production method

Abstract

The present invention provides a hydrogen embrittlement-resistant cold-rolled DH1200 steel plate and a production method thereof. The percentage of each element in the steel plate is as follows by weight: C: 0.15% - 0.25%, Mn: 1.5% - 2.5%, Si: 0.5% - 1.5%, Al: 0.7% - 7.0%, Cr: 0.02 - 0.80%, Ni: 0.05 - 0.80%, P ≤ 0.01%, S ≤ 0.01%, N ≤ 0.005%, Mg: 0.005% - 0.50%, Nb: 0.01% - 0.50%, Ti: 0.01% - 0.50%, and 5 ≤ Al / Si ≤ 10, with the balance being iron and unavoidable impurities; The present invention realizes the low-carbon, green, and lightweight design and development of automotive high-strength steel through a short-process and low-cost process route and an alloy design with extreme cost reduction, while taking into account the personalized requirements of ultra-high-strength steel for hydrogen embrittlement resistance, high plasticity, and high formability, namely, the hydrogen embrittlement-resistant cold-rolled DH1200 steel plate and a production method thereof.

Description

Technical Field

[0001] The present invention belongs to the field of metal materials, and particularly relates to a hydrogen embrittlement-resistant cold-rolled DH1200 steel plate and a production method thereof. Background Art

[0002] Hydrogen embrittlement (hydrogen-induced delayed cracking) refers to the problem that parts do not crack when manufactured, but over time, under the dual action of stress and corrosive media, stress corrosion cracking occurs, ultimately leading to part failure and the loss of safety protection. In this process, hydrogen plays a role in promoting crack initiation and propagation, and the hydrogen-induced delayed cracking sensitivity of ultra-high-strength steel will increase significantly with the increase of strength level. In actual production, it is found that the dual-phase steel (DH steel) with enhanced formability above the 1.2 GPa level has a higher risk of hydrogen-induced delayed cracking due to the presence of more phase structures, and this phenomenon seriously affects the normal service of parts. The delayed fracture phenomenon of ultra-high-strength DH steel has received great attention from manufacturers and users.

[0003] Under the background of "dual carbon", the steel industry is actively promoting energy conservation, environmental protection, and green transformation and development. DH steel products have the characteristics of diverse parts, diversified user needs, multiple product specifications, and special requirements for small-batch orders. Therefore, developing green and low-carbon DH steel products for automobiles, that is, alloy design for multiple uses of one steel and short-process low-cost preparation processes, can not only meet the special requirements of the automotive industry for diverse parts, diversified user needs, multiple specifications, and small-batch orders, but also be an effective measure for steel enterprises to improve their competitiveness, becoming a research hotspot for major steel suppliers. Based on the above research status, it is urgent to solve the problems of poor formability and hydrogen embrittlement of automotive high-strength steel, and at the same time adapt to the green and low-carbon product design of automotive high-strength steel under the dual-carbon background.

[0004] The relevant patent documents are as follows:

[0005] . Patent document CN112095046B discloses an ultra-high-strength cold-rolled DH1180 steel and a preparation method thereof. Its main chemical components are: C: 0.18% - 0.25%, Mn: 1.8% - 2.8%, Si: 0.5% - 1.4%, Al: 0.02% - 1.4%, Cr: 0.03% - 0.60%, Mo: 0.04% - 0.40%, Ti: 0.002% - 0.10%, P≤0.03%, S≤0.03%, V≤0.05%, Nb≤0.1%, and the rest is Fe and unavoidable impurities. This invention adopts a cold-rolling - continuous annealing production process to produce ultra-high-strength cold-rolled DH1180 steel. The product of this invention has excellent hydrogen embrittlement resistance and cold bending performance. However, this product has poor plasticity, is difficult to meet the requirements of both ultra-high strength and high plasticity and hydrogen embrittlement resistance, and the preparation process does not consider the electric furnace + scrap steel smelting process.

[0006] Patent document CN113403550A discloses a cold-rolled hot-dip galvanized DH1180 steel sheet with high plasticity and fatigue resistance and a preparation method thereof. Its main chemical components are as follows: C: 0.16% - 0.25%, Mn: 1.8% - 2.6%, Si: 0.2% - 0.8%, Al: 0.50% - 1.50%, Cr: 0.10 - 0.60%, Cu: 0.10 - 0.70%, P ≤ 0.01%, S ≤ 0.01%, N ≤ 0.003%, Nb: 0.005% - 0.15%, V: 0.005% - 0.15%, Ti: 0.005% - 0.15%, and the balance is Fe and other inevitable impurities. This invention adopts a cold-rolled - hot-dip galvanized production process to produce a cold-rolled hot-dip galvanized DH1180 steel sheet with high plasticity and fatigue resistance. This product exhibits excellent fatigue resistance and high hole expansion performance. However, this product does not consider the hydrogen embrittlement problem of ultra-high strength steel and is difficult to meet the requirements of both ultra-high strength, high plasticity and anti-hydrogen embrittlement, and the preparation process does not consider the electric furnace + scrap steel smelting process. Summary of the Invention

[0007] The purpose of the present invention is to overcome the above problems and deficiencies, and provide an anti-hydrogen embrittlement cold-rolled DH1200 steel sheet and a production method thereof, which realize the low-carbon, green and lightweight design and development of automotive high-strength steel through a short-process and low-cost process route and an alloy design for extreme cost reduction, while taking into account the personalized requirements of ultra-high strength steel for anti-hydrogen embrittlement, high plasticity and high formability.

[0008] The purpose of the present invention is achieved as follows:

[0009] An anti-hydrogen embrittlement cold-rolled DH1200 steel sheet, the composition of the steel sheet is as follows by weight percentage: C: 0.15% - 0.25%, Mn: 1.5% - 2.5%, Si: 0.5% - 1.5%, Al: 0.7% - 7.0%, Cr: 0.02 - 0.80%, Ni: 0.05 - 0.80%, P ≤ 0.01%, S ≤ 0.01%, N ≤ 0.005%, Mg: 0.005% - 0.50%, Nb: 0.01% - 0.50%, Ti: 0.01% - 0.50%, and 1 ≤ Al / Si ≤ 10, and the rest is iron and inevitable impurities.

[0010] In the DH1200 steel sheet, 0.4% ≤ Cr + Ni ≤ 1.4%.

[0011] The microstructure of the DH1200 steel plate is ferrite + martensite + retained austenite + bainite. The volume percentages of each microstructure are as follows: ferrite 10% - 30%, martensite 50% - 80%, retained austenite 3% - 12%, and bainite 3% - 15%. In the product of the present invention, the retained austenite exists in two forms: blocky and film-like, with a grain size between 0.05 μm and 0.50 μm. The blocky retained austenite is mainly distributed at the martensite / ferrite interface and inside the ferrite, while the film-like retained austenite is mainly distributed between the martensite laths.

[0012] The yield strength of the DH1200 steel plate is ≥850 MPa, the tensile strength is ≥1200 MPa, the elongation after fracture A80 is ≥14.0%, the hole expansion rate is ≥30%, and the density is 6.5 - 7.5 g / cm 3 ; The pre-stress is formed by 180° U-shaped bending and immersed in a 0.5 mol / L HCl solution for 14 days, and no delayed fracture occurs; it meets the requirements of ultra-high strength automotive steel for hydrogen embrittlement resistance, low density, high strength and high plasticity, and excellent formability.

[0013] The reasons for the composition design are as follows:

[0014] C: Carbon element ensures the strength requirements of the steel through solid solution strengthening. A sufficient amount of carbon element helps to stabilize austenite, thereby improving the formability of the steel. If the content of C element is too low, the mechanical properties of the steel in the present invention cannot be obtained; if the content is too high, the steel will become brittle and there is a risk of hydrogen-induced delayed fracture. Therefore, in the present invention, the content of C element is controlled to be 0.15% - 0.25%.

[0015] Mn: Manganese element is an austenite stabilizing element in steel, which can expand the austenite phase region, reduce the critical quenching rate of the steel. At the same time, it can also refine the grains and contribute to solid solution strengthening to improve the strength. If the content of Mn element is too low, the supercooled austenite is not stable enough, reducing the processing properties such as plasticity and toughness of the steel plate; if the content of Mn element is too high, it will lead to poor welding performance of the steel plate and an increase in production cost, which is not conducive to industrial production. Therefore, in the present invention, the content of Mn element is controlled to be 1.5% - 2.5%.

[0016] Si: Silicon element has a certain solid solution strengthening effect in ferrite to ensure that the steel has sufficient strength. At the same time, Si can also inhibit the decomposition of retained austenite and the precipitation of carbides, reducing inclusions in the steel. In the present invention, Si element and Al element are used in combination, and the design concept of substituting silicon with aluminum can significantly improve the surface quality of the steel. If the content of Si element is too low, it cannot play a strengthening role; if the content of Si element is too high, it will reduce the surface quality and welding performance of the steel plate. Therefore, in the present invention, the content of Si element is controlled to be 0.5% - 1.5%, and 1 ≤ Al / Si ≤ 10;.

[0017] Al: The density of aluminum is much lower than that of Fe. Adding an appropriate amount of Al to steel can significantly reduce the density of steel, which is conducive to the lightweight development of steel. At the same time, Al has an antioxidant effect. Adding it in combination with Si can effectively improve the surface quality of steel, which is conducive to the design of one steel for multiple uses. In addition, Al can also inhibit the decomposition of residual austenite and the precipitation of carbides, and accelerate the transformation of bainite to improve the coordinated deformation ability. In addition, aluminum can inhibit the decomposition of residual austenite and the precipitation of carbides, and accelerate the transformation of bainite to improve the coordinated deformation ability. If the Al content is too high, it will not only increase the production cost, but also cause difficulties in continuous casting production. When the aluminum content is too low, the low-density design of the material cannot be achieved. Therefore, in the present invention, the range of the Al content is controlled within 0.7% to 7.0%, and 1≤Al / Si≤10.

[0018] Cr: Chromium can increase the hardenability of steel to ensure the strength of steel, and can stabilize the retained austenite. When properly matched with Ni, it helps to significantly improve the material's resistance to hydrogen embrittlement, which is conducive to the realization of a one-steel-multi-purpose product design. Too low a Cr content will affect the hardenability of steel, and too high a Cr content will increase production costs. Therefore, in the present invention, the Cr content is controlled within the range of 0.02% to 0.80%, and 0.4% ≤ Cr + Ni ≤ 1.4%.

[0019] Ni: Nickel is an important element for improving the welding performance of steel. The addition of Ni is beneficial to improving the toughness of the weld, especially the low-temperature impact toughness, and reducing the brittle transition temperature. Reasonable combination with Cr can effectively control the phase transformation process of the weld metal, and obtain a composite structure of martensite and a certain proportion of residual austenite, thereby taking into account high crack resistance and high strength, which is conducive to realizing the design of one steel for multiple uses. The present invention controls the content of Ni element in the range of 0.05% to 0.80%, and 0.4%≤Cr+Ni≤1.4%.

[0020] P: P is a harmful element in steel, which is very easy to segregate to the grain boundary and seriously reduce the plasticity and deformation performance of the steel. The lower its content, the better. Considering the cost, the content of P in the present invention is controlled to P≤0.01%.

[0021] S: S is a harmful element in steel. Sulfur and manganese are easily combined to form MnS inclusions. After rolling and deformation, the transverse properties of the material will be significantly reduced, which seriously affects the formability of the steel. The lower the content, the better. Considering the cost, the content of S in the present invention is controlled to S≤0.01%.

[0022] N: N element easily reacts with Ti to precipitate large TiN particles, which act as crack sources during deformation and are detrimental to the anti-hydrogen embrittlement performance. Therefore, the N element content in the steel must be strictly controlled. The present invention controls the N content to N≤0.005%.

[0023] Mg: Magnesium is a good deoxidizer, desulfurizer and spheroidizer in steel. Mg can reduce the number of inclusions in steel, make their size smaller, distribution more uniform, and morphology improved. A small amount of magnesium can improve the carbide size and distribution in DH steel, promote the carbide particles to be fine and uniform, and also contribute to the realization of low-density material design. In order to control the production cost, the content of Mg element in this invention is controlled within 0.005% - 0.50%.

[0024] Nb: The microalloying element Nb forms compounds with carbon and nitrogen, which helps to delay the recrystallization of the material during hot rolling, has the effect of refining the grain size, and significantly improves the strength, toughness and fatigue resistance of the material. In this invention, the content of Nb element is controlled within 0.01% - 0.50%.

[0025] Ti: Adding a small amount of Ti element can refine the grain size. The precipitates can pin dislocations to delay the propagation of crack sources and significantly improve the strength and toughness of the material. In this invention, the content of Ti element is controlled within 0.01% - 0.50%.

[0026] The second technical solution of this invention is to provide a production method of hydrogen embrittlement-resistant cold-rolled DH1200 steel plate, which is characterized by including the following steps: electric furnace smelting, medium-thin slab continuous casting and rolling, pickling and cold rolling, continuous annealing or continuous hot-dip coating process or alloyed hot-dip galvanizing, skin pass. The specific steps of this preparation process are as follows:

[0027] Electric furnace smelting: In this invention, 30% - 70% of scrap steel is selected as raw material, and the molten steel temperature is between 1600 - 1750 °C.

[0028] Medium-thin slab continuous casting and rolling: High-aluminum steel special protective slag is used for casting. Preferably, the Li2O content range in the protective slag is 0.5% - 10.0%, the casting temperature is 1530 - 1600 °C, the casting machine drawing speed is 1.0 - 5.5 m / min, and the continuous casting billet thickness is between 60 - 115 mm. The starting rolling temperature is between 1000 - 1150 °C, the finishing rolling temperature is above 900 °C, and the coiling temperature is between 600 - 700 °C. The thickness specification of the hot-rolled coil is 2.0 - 4.5 mm.

[0029] The microstructure of the steel plate after hot rolling is ferrite + pearlite + bainite + cementite; the volume percentages of each microstructure are as follows: ferrite 30% - 60%, pearlite 20% - 50%, bainite 5% - 20%, cementite 1% - 5%;

[0030] Pickling and cold rolling: Before cold rolling, the hot-rolled steel coil removes the scale on the surface through acid solution, and the cold rolling reduction rate is 45% - 70%. If the reduction rate is too high, it will lead to too large deformation resistance and it is difficult to roll to the target thickness; if the reduction rate is too low, it will lead to a decrease in the elongation of the cold-rolled steel plate, and the thickness of the cold-rolled finished product is 1.0 mm - 2.0 mm.

[0031] The cold-rolled steel sheet is subjected to continuous annealing, continuous hot-dip coating process or alloying hot-dip galvanizing;

[0032] The continuous hot-dip coating process is continuous hot-dip galvanizing or continuous hot-dip aluminum-magnesium zinc.

[0033] Skin pass: In the skin pass process, elongation closed-loop control is adopted, and the skin pass elongation is 0.2% - 0.6%.

[0034] Among them, continuous annealing: The strip speed is controlled at 60 - 180 m / min, the furnace temperature in the soaking section is 760 - 880 °C, the soaking time is 10 - 600 s, the slow cooling outlet temperature is 700 - 750 °C, the rapid cooling rate is greater than 25 °C / s, the rapid cooling temperature is between 450 - 470 °C, the aging temperature is 250 - 460 °C, and the aging time is 60 - 1000 s. The annealing temperature is 760 - 880 °C. If the annealing temperature is too high, since austenitization tends to be complete and the ferrite ratio is insufficient, the ductility of the steel will be reduced; if the annealing temperature is too low, the proportion of soft-phase ferrite in the final material will be too high, which will greatly reduce the strength of the material. The annealing time is 10 - 600 s. If the annealing time is too long, it will cause the grains of the steel sheet to become coarse. If the annealing time is too short, the steel sheet will not have enough time to complete the annealing and recrystallization processes, resulting in a decrease in the elongation of the steel sheet.

[0035] Among them, continuous hot-dip galvanizing / aluminum-magnesium zinc: The strip speed is controlled at 60 - 180 m / min, the annealing temperature is between 760 - 880 °C, the dew point temperature is controlled between -20 - -10 °C, the annealing time is between 30 - 300 s, the slow cooling outlet temperature is 680 - 720 °C, the rapid cooling rate is greater than 20 °C / s, the rapid cooling outlet temperature is 450 - 470 °C, the galvanizing temperature is 450 - 470 °C. After galvanizing, the strip is first cooled by an air knife to 400 - 420 °C, and then air-cooled. The temperature of the top roll of the cooling tower is controlled at 250 - 300 °C.

[0036] The composition of the galvanizing bath contains 0.16% - 0.25% Al, and the rest is Zn and inevitable impurities. The zinc layer weight per unit area is 60 - 200 g / cm 2 .

[0037] The composition of the aluminum-magnesium zinc galvanizing bath contains 2.0% - 10.0% Al, 1.0% - 5.0% Mg, 0.001% - 0.1% Si, and the rest is Zn and inevitable impurities. The zinc-aluminum-magnesium coating weight per unit area is 50 - 200 g / cm 2 .

[0038] Among them, for alloying hot-dip galvanizing: the strip speed is controlled at 60 - 180 m / min, the annealing temperature is 770 - 870 °C, the annealing time is between 30 - 300 s, the dew point is controlled at -20 - -10 °C, the slow cooling outlet temperature is 680 - 750 °C, the rapid cooling rate is greater than 20 °C / s, the fast cooling outlet temperature is between 450 - 470 °C, the galvanizing temperature is 450 - 470 °C. After galvanizing, the strip is first cooled by an air knife to 400 - 420 °C, and then alloying treatment is carried out. The alloying temperature is 470 - 530 °C, and the alloying holding time is 5 - 60 s.

[0039] The microstructure of the steel plate produced by the present invention is ferrite + martensite + retained austenite + bainite. The proportions of each microstructure by volume percentage are as follows: ferrite 10% - 30%, martensite 50% - 80%, retained austenite 3% - 12%, bainite structure 3% - 15%. And in the product of the present invention, the retained austenite exists in two forms: blocky and film-like, the grain size is between 0.05 μm - 0.50 μm. The blocky retained austenite is mainly distributed at the martensite / ferrite interface and inside the ferrite, while the film-like retained austenite is mainly distributed between the martensite laths.

[0040] Through the above method, a hydrogen embrittlement-resistant cold-rolled DH1200 steel plate can be obtained with a yield strength ≥ 850 MPa, a tensile strength ≥ 1200 MPa, an elongation after fracture of A80 ≥ 14.0%, an expansion rate ≥ 30%, and a density of 6.5 - 7.5 g / cm3. The 180° U-shaped bending forming pre-stress is adopted and immersed in a 0.5 mol / L HCl solution for 14 days, and no delayed fracture occurs.

[0041] The technical effects of the present invention are as follows:

[0042] (1) The chemical composition of the steel in the present invention mainly uses C, Mn, Al, and Si as the main elements, and the original cost is relatively low.

[0043] (2) The present invention adopts a new short-process low-cost production process of "large proportion of scrap steel + electric furnace smelting + medium and thin slab continuous casting and rolling", which can greatly reduce carbon emissions and save energy consumption;

[0044] (3) The hydrogen embrittlement-resistant cold-rolled DH1200 steel plate produced by the present invention adds a certain proportion of retained austenite on the basis of traditional cold-rolled dual-phase steel. Under the action of the transformation-induced plasticity (TRIP) effect, its high strength, high plasticity, and formability are realized;

[0045] (4) The hydrogen embrittlement-resistant cold-rolled DH1200 steel plate produced by the present invention adds a large amount of aluminum element, which can achieve low density of high-strength steel and meet the requirements of automotive lightweight design;

[0046] (5) The hydrogen embrittlement-resistant cold-rolled DH1200 steel plate produced by the present invention can meet the diverse product requirements of continuous annealing, continuous hot-dip galvanizing / galvanized aluminum-magnesium, and alloyed hot-dip galvanizing with a set of alloy systems due to its special design in composition and process, that is, it can be used for multiple purposes with one steel. It can not only significantly shorten the product development cycle and R & D costs, but also enable the conversion between multiple grades of products and significantly improve the product production efficiency.

[0047] (6) The hydrogen embrittlement-resistant cold-rolled DH1200 steel plate produced by the present invention can achieve a yield strength ≥ 850 MPa, a tensile strength ≥ 1200 MPa, an elongation after fracture of A80 ≥ 14.0%, an expansion rate ≥ 30%, and a density of 6.5 - 7.5 g / cm³; it has excellent performance that no delayed fracture occurs after being pre-stressed by 180° U-shaped bending and immersed in 0.5 mol / L HCl solution for 14 days. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is the metallographic diagram of the microstructure of Example 1-1 of the present invention.

[0049] Figure 2 It is the metallographic diagram of the microstructure of Example 1-3 of the present invention.

[0050] Figure 3 It is the stress-strain curve of Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0051] The present invention will be further described below through embodiments.

[0052] In the embodiments of the present invention, according to the component ratios of the technical solutions, electric furnace smelting, medium-thin slab continuous casting and rolling, pickling cold rolling, continuous annealing or continuous hot-dip coating process or alloyed hot-dip galvanizing, and skin pass rolling are carried out.

[0053] Electric furnace smelting: 30% - 70% proportion of scrap steel is added as raw material, and the molten steel temperature is 1600 - 1750 °C;

[0054] Medium-thin slab continuous casting and rolling: Special protective slag for high-aluminum steel is used for casting, the casting temperature is 1530 - 1600 °C, the casting machine drawing speed is 1.0 - 5.5 m / min, and the continuous casting slab thickness is 60 - 115 mm;

[0055] The starting rolling temperature is 1000 - 1150 °C, the final rolling temperature is above 900 °C, and the coiling temperature is 600 - 700 °C; the thickness of the hot-rolled coil steel plate is 2.0 - 4.5 mm; the microstructure of the steel plate after hot rolling is ferrite + pearlite + bainite + cementite; the volume percentages of each microstructure are as follows: ferrite 30% - 60%, pearlite 20% - 50%, bainite 5% - 20%, cementite 1% - 5%;

[0056] Pickling and cold rolling: The cold rolling reduction rate is 45% - 70%; the finished thickness after cold rolling is 1.0 mm - 2.0 mm;

[0057] After cold rolling, the steel plate is subjected to continuous annealing or continuous hot-dip coating process or alloying hot-dip galvanizing;

[0058] The continuous hot-dip coating process is continuous hot-dip galvanizing or continuous hot-dip aluminum-magnesium-zinc.

[0059] Skin pass: In the skin pass process, elongation closed-loop control is adopted, and the skin pass elongation is 0.2% - 0.6%.

[0060] Furthermore; continuous annealing: The strip speed is controlled at 60 - 180 m / min, the annealing temperature is 760 - 880 °C, the soaking time is 10 - 600 s, the slow cooling outlet temperature is 700 - 750 °C, the rapid cooling rate is greater than 25 °C / s, the rapid cooling temperature is reduced to 450 - 470 °C, the aging temperature is 250 - 460 °C, and the aging time is 60 - 1000 s.

[0061] Furthermore; continuous hot-dip galvanizing or continuous hot-dip aluminum-magnesium-zinc process: The annealing temperature is 760 - 880 °C, the dew point temperature is -20 - -10 °C, the annealing time is 30 - 300 s, the slow cooling outlet temperature is 680 - 720 °C, the rapid cooling rate is greater than 20 °C / s, the rapid cooling outlet temperature is 450 - 470 °C, the plating bath temperature is 450 - 470 °C. After the plating is completed, the strip is first cooled by an air knife to 400 - 420 °C, and then air-cooled. The temperature of the top roll at the cooling tower is 250 - 300 °C.

[0062] During continuous hot-dip galvanizing, the plating bath composition by mass percentage is Al: 0.16% - 0.25%, and the rest is Zn and inevitable impurities; the zinc coating weight per unit area of the steel plate after continuous hot-dip galvanizing is 60 - 200 g / cm 2 .

[0063] During continuous hot-dip aluminum-magnesium-zinc, the plating bath composition by mass percentage is Al: 2.0% - 10.0%, Mg: 1.0% - 5.0%, Si: 0.001% - 0.1%, and the rest is Zn and inevitable impurities. The zinc-aluminum-magnesium coating weight per unit area of the steel plate after continuous hot-dip aluminum-magnesium-zinc is 50 - 200 g / cm 2 .

[0064] Furthermore; the alloying hot-dip galvanizing: The annealing temperature is 770 - 870 °C, the annealing time is 30 - 300 s, the dew point control is -20 - -10 °C, the slow cooling outlet temperature is 680 - 750 °C, the rapid cooling rate is greater than 20 °C / s, the rapid cooling outlet temperature is 450 - 470 °C, the galvanizing temperature is 450 - 470 °C. After galvanizing, the strip is first cooled by an air knife to 400 - 420 °C, and then alloying treatment is carried out. The alloying temperature is 470 - 530 °C, and the alloying holding time is 5 - 60 s.

[0065] The chemical composition of the steel in the embodiments of the present invention is shown in Table 1. The main process parameters of steel smelting, continuous casting and rolling, and the hot-rolled microstructure in the embodiments of the present invention are shown in Table 2. The main process parameters of continuous annealing of the steel in the embodiments of the present invention are shown in Table 3. The main process parameters of continuous hot-dip galvanizing of the steel in the embodiments of the present invention are shown in Table 4. The main process parameters of continuous hot-dip galvanizing of aluminum-magnesium alloy on the steel in the embodiments of the present invention are shown in Table 5. The main process parameters of alloying hot-dip galvanizing of the steel in the embodiments of the present invention are shown in Table 6. The properties of the steel in the embodiments of the present invention are shown in Table 7. The proportion of the microscopic structure of the steel in the embodiments of the present invention is shown in Table 8.

[0066] Table 1 Chemical composition of the steel in the embodiments of the present invention (wt%)

[0067] Example C Mn Si Al Cr Ni P S N Mg Nb Ti Al / Si Cr+Ni 1 0.21 1.54 0.56 2.83 0.56 0.21 0.002 0.006 0.002 0.012 0.062 0.086 5.05 0.77 2 0.19 1.66 0.87 4.96 0.21 0.45 0.005 0.002 0.003 0.023 0.031 0.12 5.70 0.66 3 0.17 2.47 0.92 0.95 0.42 0.33 0.003 0.003 0.001 0.041 0.097 0.21 1.03 0.75 4 0.18 1.95 0.86 5.52 0.74 0.12 0.003 0.004 0.001 0.121 0.16 0.042 6.42 0.86 5 0.15 2.31 0.64 4.49 0.13 0.64 0.002 0.001 0.004 0.304 0.42 0.18 7.02 0.77 6 0.18 1.74 1.28 3.88 0.71 0.20 0.002 0.005 0.003 0.173 0.37 0.39 3.03 0.91

[0068] Table 2 Main process parameters of steel smelting, continuous casting and rolling, and hot-rolled microstructure in the embodiments of the present invention

[0069]

[0070] Table 3 Main process parameters of continuous annealing of the steel in the embodiments of the present invention

[0071]

[0072] Table 4 Main process parameters of continuous hot-dip galvanizing of the steel in the embodiments of the present invention

[0073]

[0074] Table 5 Main process parameters of continuous hot-dip galvanizing of aluminum-magnesium alloy on the steel in the embodiments of the present invention

[0075]

[0076] Table 6 Main process parameters of alloying hot-dip galvanizing of the steel in the embodiments of the present invention

[0077]

[0078] Table 7 Properties of the steel in the embodiments of the present invention

[0079]

[0080] Note: The evaluation of the hydrogen embrittlement resistance (anti-delayed fracture) performance is carried out by U-shaped bending immersion evaluation. The cold bending radius of 180° is 5 mm. Each group has 5 parallel specimens, which are immersed in 0.5 mol / L HCl solution for 14 days. If no fracture occurs, it is determined that the specimen has no risk of delayed fracture and is marked as Ο; if fracture occurs, it is determined that the specimen has a risk of delayed fracture and is marked as ×.

[0081] Table 8 Microscopic structure of the steel in the embodiments of the present invention

[0082] Example Ferrite / % Martensite / % Retained austenite / % Bainite / % 1-1 29.8 50.2 8.1 11.9 2-1 32.7 43.1 11 13.2 3-1 44.1 35.5 8.7 11.7 4-1 43.4 38.2 7.8 10.6 5-1 35.5 48.6 6.3 9.6 6-1 26.9 50.6 10.7 11.8 1-2 40.2 40.8 8.6 10.4 2-2 44.7 37.8 11.8 5.7 3-2 41.4 40.2 8.3 10.1 4-2 42.8 38.1 7.3 11.8 5-2 35.5 48.3 9.7 6.5 6-2 28.8 49.8 12.7 8.7 1-3 37.4 47 6.1 9.5 2-3 36.8 45.2 9.2 8.8 3-3 41.9 43.9 5.7 8.5 4-3 43.3 39.8 8.2 8.7 5-3 30.1 50.9 8.6 10.4 6-3 41.7 40.8 11.8 5.7 1-4 41.9 42.8 8.1 7.2 2-4 28.3 48.0 9.6 14.1 3-4 36.4 43.4 9.5 10.7 4-4 43.9 39.6 7.3 9.2 5-4 41.4 38.8 10.1 9.7 6-4 38.2 40.5 7.7 13.6

[0083] In order to describe the present invention, the present invention has been appropriately and fully described by way of examples above. The above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Those of ordinary skill in the relevant technical field can also make various changes and modifications without departing from the spirit and scope of the present invention. Any modifications, equivalent replacements, improvements, etc. should be included within the protection scope of the present invention. The patent protection scope of the present invention shall be defined by the claims.

Claims

1. A hydrogen embrittlement-resistant cold-rolled DH1200 steel plate, characterized in that, The components of each element in the steel plate are as follows by mass percentage: C: 0.15% - 0.25%, Mn: 1.5% - 2.5%, Si: 0.92% - 1.5%, Al: 0.95% - 7.0%, Cr: 0.02% - 0.80%, Ni: 0.45% - 0.80%, P ≤ 0.01%, S ≤ 0.01%, N ≤ 0.005%, Mg: 0.023% - 0.50%, Nb: 0.01% - 0.50%, Ti: 0.01% - 0.50%, and 3.03 ≤ Al / Si ≤ 10, with the rest being iron and inevitable impurities; the microstructure of the DH1200 steel plate is ferrite + martensite + retained austenite + bainite, and the volume percentages of each microstructure are as follows: ferrite 10% - 30%, martensite 50% - 80%, retained austenite 3% - 12%, bainite structure 3% - 15%; and the retained austenite presents two forms of blocky and film-like, the grain size is between 0.05 µm and 0.50 µm, the blocky retained austenite is mainly distributed at the martensite / ferrite interface and inside the ferrite, while the film-like retained austenite is mainly distributed between the martensite laths.

2. The anti-hydrogen embrittlement cold-rolled DH1200 steel plate according to claim 1, characterized in that, In the DH1200 steel plate, 0.66% ≤ Cr + Ni ≤ 1.4%.

3. The hydrogen embrittlement resistant cold-rolled DH1200 steel sheet according to claim 1, characterized in that, The yield strength of the DH1200 steel plate is ≥850 MPa, the tensile strength is ≥1200 MPa, the elongation after fracture of A80 is ≥14.0%, the hole expansion rate is ≥30%, and the density is 6.5 - 7.5 g / cm 3 .

4. A production method of an anti-hydrogen embrittlement cold-rolled DH1200 steel plate according to any one of claims 1-3, characterized in that, Including electric furnace smelting, medium thin slab continuous casting and rolling, pickling and cold rolling, continuous annealing or continuous hot-dip coating process or alloyed hot-dip galvanizing, skin pass; the components of each element in the steel plate are as follows by mass percentage: C: 0.15% - 0.25%, Mn: 1.5% - 2.5%, Si: 0.92% - 1.5%, Al: 0.97% - 7.0%, Cr: 0.02% - 0.80%, Ni: 0.45% - 0.80%, P ≤ 0.01%, S ≤ 0.01%, N ≤ 0.005%, Mg: 0.023% - 0.50%, Nb: 0.01% - 0.50%, Ti: 0.01% - 0.50%, and 3.03 ≤ Al / Si ≤ 10, with the rest being iron and inevitable impurities; Electric furnace smelting: Adding 30% - 70% proportion of scrap steel as raw material, the molten steel temperature is 1600 - 1750 °C; Medium thin slab continuous casting and rolling: Using special protective slag for high-aluminum steel for casting, the casting temperature is 1530 - 1600 °C, the casting machine pulling speed is 1.0 - 5.5 m / min, and the continuous casting slab thickness is 60 - 115 mm; The starting rolling temperature is 1000 - 1150 °C, the final rolling temperature is above 900 °C, and the coiling temperature is 600 - 700 °C; the thickness of the hot rolled coil steel plate is 2.0 - 4.5 mm; the microstructure of the steel plate after hot rolling is ferrite + pearlite + bainite + cementite; the volume percentages of each microstructure are as follows: ferrite 30% - 60%, pearlite 20% - 50%, bainite 5% - 20%, cementite 1% - 5%; Pickling and cold rolling: The cold rolling reduction rate is 45% - 70%; the thickness of the finished product after cold rolling is 1.0 mm - 2.0 mm; The steel plate after cold rolling is subjected to continuous annealing or continuous hot-dip coating process or alloyed hot-dip galvanizing; The continuous hot-dip coating process is continuous hot-dip galvanizing or continuous hot-dip aluminum-magnesium zinc; Skin pass: The skin pass process adopts closed-loop control of elongation, and the skin pass elongation is 0.2% - 0.6%.

5. The production method of an anti-hydrogen embrittlement cold-rolled DH1200 steel sheet according to claim 4, characterized in that Continuous annealing: The strip speed is controlled at 60 - 180 m / min, the annealing temperature is 760 - 835 °C, the annealing time is 10 - 600 s, the slow cooling outlet temperature is 738 - 750 °C, the rapid cooling rate is greater than 25 °C / s, the rapid cooling temperature is reduced to 450 - 470 °C, the aging temperature is 250 - 460 °C, and the aging time is 60 - 1000 s.

6. The production method of an anti-hydrogen embrittlement cold-rolled DH1200 steel sheet according to claim 4, characterized in that Continuous hot-dip galvanizing or continuous hot-dip galvanized aluminum-magnesium process: The annealing temperature is 760 - 880 °C, the dew point temperature is -20 - -10 °C, the annealing time is 30 - 300 s, the slow cooling outlet temperature is 680 - 720 °C, the rapid cooling rate is greater than 20 °C / s, the rapid cooling outlet temperature is 450 - 470 °C, the plating bath temperature is 450 - 470 °C. After plating, the strip is first cooled by an air knife to 400 - 420 °C, and then air-cooled. The temperature of the top roll at the cooling tower is 250 - 300 °C.

7. The production method of a hydrogen embrittlement resistant cold-rolled DH1200 steel plate according to claim 6, characterized in that, During the continuous hot-dip galvanizing process, the composition of the plating solution is by mass percentage: Al: 0.16% - 0.25%, and the rest is Zn and inevitable impurities; the weight of the zinc layer per unit area of the steel plate after continuous hot-dip galvanizing is 60 - 200 g / cm 2 .

8. The production method of a hydrogen embrittlement-resistant cold-rolled DH1200 steel plate according to claim 6, characterized in that, During the continuous hot-dip galvanizing-aluminum-magnesium process, the composition of the plating solution is, by mass percentage, Al: 2.0% - 10.0%, Mg: 1.0% - 5.0%, Si: 0.001% - 0.1%, and the rest is Zn and inevitable impurities. After the continuous hot-dip galvanizing-aluminum-magnesium process, the weight of the zinc-aluminum-magnesium coating per unit area of the steel plate is 50 - 200 g / cm 2 .

9. The production method of an anti-hydrogen embrittlement cold-rolled DH1200 steel plate according to claim 4, characterized in that, The alloying hot-dip galvanizing: The annealing temperature is 770 - 870 °C, the annealing time is 30 - 300 s, the dew point control is -20 - -10 °C, the slow cooling outlet temperature is 680 - 750 °C, the rapid cooling rate is greater than 20 °C / s, the rapid cooling outlet temperature is 450 - 470 °C, the galvanizing temperature is 450 - 470 °C. After galvanizing, the strip is first cooled by an air knife to 400 - 420 °C, and then alloying treatment is carried out. The alloying temperature is 470 - 530 °C, and the alloying holding time is 5 - 60 s.

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