A kind of hydrogen embrittlement resistant cold-rolled DH1500 steel and its manufacturing method

Abstract

The present invention provides a hydrogen embrittlement resistant cold-rolled DH1500 steel and a manufacturing method thereof. The components of the steel plate are as follows by weight percentage: C: 0.20% to 0.30%, Mn: 2.0% to 3.0%, Si: 0.8% to 2.0%, Al: 0.8% to 8.0%, Mo: 0.02% to 0.80%, Cu: 0.05% to 0.80%, P≤0.01%, S≤0.01%, N≤0.005%, Mg: 0.005% to 0.50%, Ti: 0.01% to 0.50 %, V: 0.01% ~ 0.50%, and 1 ≤ Al / Si ≤ 10; the rest are iron and unavoidable impurities; the manufacturing method includes electric furnace smelting, medium and thin slab continuous casting and rolling, pickling and cold rolling, continuous annealing or continuous hot-dip process or alloying hot-dip galvanizing, and skin pass; the present invention realizes the low-carbon, green and lightweight design and development of automotive high-strength steel with a short-process low-cost process path and an extremely cost-reducing alloy design, while taking into account the personalized needs of ultra-high-strength steel for hydrogen embrittlement resistance, high plasticity and high formability, providing reliable technical solutions for the majority of automobile manufacturers and steel companies.

Description

Technical Field

[0001] The invention belongs to the field of metal materials, and in particular relates to a hydrogen embrittlement resistant cold-rolled DH1500 steel and a manufacturing method thereof. Background Art

[0002] Hydrogen embrittlement (hydrogen-induced delayed cracking) refers to the problem that parts do not crack when they are manufactured, but over time, under the dual effects of stress and corrosive media, stress corrosion cracking occurs, which eventually leads to part failure and loss of safety protection. In this process, hydrogen promotes crack initiation and expansion, 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 1.5GPa-level enhanced formability dual-phase steel (DH steel) 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] DH steel products have the characteristics of diversified parts, diversified user needs, multiple product specifications, and special needs of small batch orders. Therefore, the development of green and low-carbon DH steel products for automobiles, that is, one steel multi-purpose alloy design and short process low-cost preparation technology, can not only meet the characteristics of multiple parts, diversified user needs, multiple specifications, and special needs of small batch orders in the automotive industry, but also is an effective measure for steel companies to improve their competitiveness, and has become a research hotspot for major steel suppliers. Based on the above research status, it is urgent to solve the poor forming performance and hydrogen embrittlement problems of automotive high-strength steel, and at the same time adapt to the design of green and low-carbon products of automotive high-strength steel.

[0004] Related patent documents:

[0005] Patent document CN113388779A discloses a 1.5GPa grade ultra-high strength, high plasticity and high hole expansion DH steel plate and a preparation method, whose main chemical components are: C: 0.20%~0.26%, Mn: 1.8%~2.8%, Si: 1.0%~2.0%, Al: 0.02%~0.08%, Cr: 0.20%~0.80%, P≤0.01%, S≤0.01%, Nb: 0.02%~0.15%, V: 0.02%~0.15%, Ti: 0~0.10%, and the rest are Fe and unavoidable impurities. This invention adopts the production process of cold rolling-continuous annealing to produce 1.5GPa grade ultra-high strength, high plasticity and high hole expansion DH steel plate. The product of this invention has excellent hole expansion performance. However, the plasticity of this product is poor and the hydrogen embrittlement problem existing in ultra-high strength steel is not considered. It is difficult to meet the requirements of both high plasticity and hydrogen embrittlement resistance, and the preparation process fails to consider the electric furnace + scrap steel smelting process.

[0006] Patent document CN113416889A discloses an ultra-high strength hot-dip galvanized DH1470 steel with good welding performance and a preparation method, wherein the main chemical components are: C: 0.18%-0.26%, Mn: 2.0%-2.9%, Si: 0.2%-1.2%, Al: 0.50%-1.60%, Mo: 0.30%-0.80%, Ni: 0.20%-0.90%, P≤0.01%, S≤0.01%, N≤0.003%, Nb: 0-0.15%, V: 0.015%-0.15%, Ti: 0.02%-0.20%, and the remainder is Fe and other inevitable impurities. This invention adopts the cold rolling-hot dip galvanizing production process to produce ultra-high strength hot dip galvanized DH1470 steel with good welding performance. The product exhibits excellent welding performance. However, the product does not take into account the hydrogen embrittlement problem of ultra-high strength steel and its poor plasticity. It is difficult to meet the requirements of both high plasticity and resistance to hydrogen embrittlement, and the preparation process fails to take into account the electric furnace + scrap steel smelting process. Summary of the invention

[0007] The purpose of the present invention is to overcome the above-mentioned problems and shortcomings and to provide a low-carbon, green and lightweight design and development of automotive high-strength steel with a short-process, low-cost process path and an extremely cost-reduced alloy design, while taking into account the personalized needs of ultra-high-strength steel for hydrogen embrittlement resistance, high plasticity and high formability, so as to provide a reliable technical solution for the majority of automobile manufacturers and steel companies. Cold-rolled DH1500 steel and its manufacturing method that resist hydrogen embrittlement.

[0008] The object of the invention is achieved in this way:

[0009] A cold-rolled DH1500 steel resistant to hydrogen embrittlement, the steel plate has the following components by weight percentage: C: 0.20%-0.30%, Mn: 2.0%-3.0%, Si: 0.8%-2.0%, Al: 0.8%-8.0%, Mo: 0.02%-0.80%, Cu: 0.05%-0.80%, P≤0.01%, S≤0.01%, N≤0.005%, Mg: 0.005%-0.50%, Ti: 0.01%-0.50%, V: 0.01%-0.50%, and 1≤Al / Si≤10; the rest is iron and unavoidable impurities.

[0010] In the DH1500 steel, 5≤Mo / Ti≤10.

[0011] The DH1500 steel microstructure is ferrite+martensite+residual austenite, and the volume percentage of each microstructure is as follows: ferrite 10%-30%, martensite 50%-80%, and residual austenite 3%-12%; and the residual austenite in the product of the present invention is in two forms: block and film, with a grain size between 0.05μm and 0.50μm, the blocky residual austenite is mainly distributed at the martensite / ferrite interface and inside the ferrite, and the film-like residual austenite is mainly distributed between the martensite laths.

[0012] DH1500 steel yield strength ≥1000MPa, tensile strength ≥1500MPa, A80 elongation ≥11.0%, hole expansion rate ≥20%, density 6.5~7.5g / cm 3 ; The steel was pre-stressed by 180° U-bending and immersed in 0.5mol / L HCl solution for 14 days without delayed fracture; it meets the requirements of ultra-high-strength automotive steel for hydrogen embrittlement resistance, low density, high strength and high plasticity, and excellent forming performance.

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

[0014] C: Carbon element ensures the strength requirement of steel through solid solution strengthening. A sufficient amount of carbon element helps stabilize austenite, thereby improving the formability of 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 0.20% to 0.30%.

[0015] Mn: Manganese is an austenite stabilizing element in steel. It can expand the austenite phase area and reduce the critical quenching rate of steel. At the same time, it can also refine the grains and help to improve the strength through solid solution strengthening. If the Mn content is too low, the supercooled austenite is not stable enough, which reduces the processing properties such as plasticity and toughness of the steel plate; if the Mn content is too high, the welding performance of the steel plate will deteriorate and the production cost will increase, which is not conducive to industrial production. Therefore, in the present invention, the Mn content is controlled to 2.0% to 3.0%.

[0016] Si: Silicon has a certain solid solution strengthening effect in ferrite, ensuring that the steel has sufficient strength. At the same time, Si can also inhibit the decomposition of residual austenite and the precipitation of carbides, reducing inclusions in the steel. In the present invention, the Si element is used in combination with the Al element, and the design concept of replacing silicon with aluminum can significantly improve the surface quality of the steel. If the Si element content is too low, it will not have a strengthening effect; if the Si element content is too high, it will reduce the surface quality and welding performance of the steel plate. Therefore, in the present invention, the Si element content is controlled to 0.8% to 2.0%, 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 0.8% to 8.0%, and 1≤Al / Si≤10.

[0018] Mo: Mo is a strengthening element in steel, which helps to stabilize the residual austenite and has a significant effect on improving the hardenability of steel. Mo and Ti can form a large number of TiMoC precipitates, which is conducive to making the diffuse hydrogen in the steel dispersed and reducing the aggregation of diffuse hydrogen, so that high strength and hydrogen embrittlement resistance can be taken into account. The present invention controls the content of Mo element in the range of 0.02% to 0.80%, and 5≤Mo / Ti≤10.

[0019] Cu: Cu is a solid solution strengthening element, which can not only improve the hardenability of steel, but also effectively improve the thermodynamic stability of austenite, help form stable residual austenite at room temperature, and further improve the plasticity and delayed fracture resistance of the material; but considering the high cost of copper, the present invention controls the content of Cu within the range of 0.05% to 0.80%.

[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, reduce their size, make their distribution uniform and improve their morphology. A small amount of magnesium can improve the carbide size and distribution of DH steel, promote the fine and uniform carbide particles, and also help to achieve low-density material design. In order to control production costs, the Mg content is controlled at 0.005% to 0.50% in the present invention.

[0024] Ti: A small amount of Ti element can refine the grain size, and the precipitates can pin dislocations to delay the expansion of crack sources and significantly improve the strength and toughness of the material. In the present invention, the Ti element content is controlled at 0.01% to 0.50%, and 5≤Mo / Ti≤10.

[0025] V: Microalloying element vanadium mainly exists in the form of VC, which improves the strength and fatigue resistance of the material through fine grain strengthening and dispersion strengthening. In the hot-dip galvanizing annealing heating process, undissolved VC particles can pin the ferrite grain boundary, thereby playing a role in refining the grains; when the annealing temperature increases to the two-phase region, the VC dissolution temperature is low, so it is fully dissolved in the matrix, and the solid solution C atoms are enriched in the austenite to improve its stability; during the annealing process, the VC in the ferrite will re-precipitate, thereby producing obvious precipitation strengthening. Therefore, in the present invention, the V element content is controlled at 0.01-0.50%.

[0026] The second technical solution of the present invention is to provide a method for manufacturing hydrogen embrittlement resistant cold-rolled DH1500 steel, comprising the following steps: electric furnace smelting, continuous casting and rolling of medium and thin slabs, pickling and cold rolling, continuous annealing or continuous hot-dip process or alloying hot-dip galvanizing, and skin pass.

[0027] Electric furnace smelting: The present invention uses 30% to 70% scrap steel as raw material and smelts it in an electric furnace.

[0028] Continuous casting and rolling of medium-thin slabs: Use special protective slag for high-aluminum steel, preferably the mass percentage of Li2O in the protective slag is 0.5% to 10.0%; cast, the casting temperature is between 1530 and 1600°C, the casting machine pulling speed is 1.0 to 5.5 m / min, and the thickness of the continuous casting slab is between 60 and 115 mm. The starting rolling temperature is between 1000 and 1150°C, the final rolling temperature is above 900°C, and the coiling temperature is between 600 and 700°C. The thickness specification of the hot-rolled coil is 2.0 to 4.5 mm, and the hot-rolled microstructure of the product is composed of 30% to 60% (volume ratio) ferrite, 20% to 50% (volume ratio) pearlite, 5% to 20% (volume ratio) bainite, and 1% to 5% (volume ratio) cementite;

[0029] Pickling cold rolling: Before cold rolling, the hot rolled steel coil is treated with acid to remove the surface iron oxide scale, and the cold rolling reduction rate is 45% to 60%. If the reduction rate is too high, the deformation resistance will be too large, and it will be difficult to roll to the target thickness; if the reduction rate is too low, the elongation of the cold rolled steel plate will decrease. The thickness of the finished product after cold rolling is 1.0mm to 2.0mm.

[0030] After cold rolling, the steel sheet undergoes continuous annealing or continuous hot-dip process or alloyed hot-dip galvanizing.

[0031] The continuous hot-dip process is continuous hot-dip galvanizing or continuous hot-dip galvanizing aluminum-magnesium.

[0032] Among them; continuous annealing: belt speed is controlled at 60-180m / min, annealing temperature is 760-880℃, soaking time is 10-600s, slow cooling outlet temperature is 700-750℃, rapid cooling rate is greater than 35℃ / s, rapid cooling temperature is between 250-350℃, aging temperature is 250-350℃, aging time is 60-1000s. The annealing temperature is 760-880℃. If the annealing temperature is too high, the ductility of the steel will be reduced due to the complete austenitization and insufficient ferrite ratio; if the annealing temperature is too low, the soft phase ferrite ratio of the final material will be too high, which will greatly reduce the strength of the material. The annealing time is 30-300s. If the annealing time is too long, the steel plate will have coarse grains. If the annealing time is too short, the steel plate will not have time to complete the annealing and recrystallization process, resulting in a decrease in the elongation of the steel plate.

[0033] Among them; continuous hot-dip galvanizing or continuous galvanized aluminum-magnesium: the belt speed is controlled at 60-180m / min, the annealing temperature is between 760-880℃, the dew point temperature is controlled between -20--10℃, the annealing time is between 30-300s, the slow cooling outlet temperature is 680-750℃, the rapid cooling rate is greater than 20℃ / s, the rapid cooling outlet temperature is 450-470℃, the plating solution temperature is 450-470℃, after the hot-dip galvanizing, the strip is first air-knife cooled to 400-420℃, and then air-cooled, and the cooling tower top roller temperature is controlled at 250-300℃.

[0034] The zinc plating solution contains 0.16% to 0.25% Al, the rest is Zn and unavoidable impurities, and the weight of the zinc layer per unit area is 60 to 200 g / cm 2 The zinc-aluminum-magnesium plating solution contains 2.0% to 10.0% Al, 1.0% to 5.0% Mg, 0.001% to 0.1% Si, and the rest is Zn and unavoidable impurities. The weight of the zinc-aluminum-magnesium coating per unit area is 50 to 200 g / cm 2 .

[0035] Among them; alloyed hot-dip galvanizing: the strip speed is controlled at 60-180m / min, the annealing temperature is 770-870℃, the annealing time is between 30-300s, the dew point is controlled at -20--10℃, the slow cooling outlet temperature is 680-750℃, the rapid cooling rate is greater than 20℃ / s, the rapid cooling outlet temperature is between 450-470℃, the galvanizing temperature is 450-470℃, after galvanizing, the strip is first air-knife cooled to 400-420℃, and then alloying treatment is carried out, the alloying temperature is 470-530℃, and the alloying holding time is 5-60s.

[0036] Skin finishing: The skin finishing process adopts rolling force control, the rolling force is controlled at 1000-3500kN, and the rolling tension is 500~2000kN.

[0037] The microstructure of the steel plate produced by the present invention is ferrite+martensite+residual austenite; the microstructures are as follows by volume percentage: ferrite 10%-30%, martensite 50%-80%, and residual austenite 3%-12%; and the residual austenite in the product of the present invention is in two forms, block and film, with a grain size between 0.05μm and 0.50μm, the block residual austenite is mainly distributed at the martensite / ferrite interface and inside the ferrite, and the film residual austenite is mainly distributed between the martensite laths.

[0038] The method can obtain a yield strength ≥1000MPa, a tensile strength ≥1500MPa, an A80 elongation after fracture ≥11.0%, a hole expansion rate ≥20%, and a density of 6.5-7.5g / cm3; a method for manufacturing hydrogen embrittlement-resistant cold-rolled DH1500 steel that adopts 180° U-shaped bending to pre-stress and is immersed in a 0.5mol / L HCl solution for 14 days without delayed fracture.

[0039] The technical effects of the present invention are as follows:

[0040] (1) The chemical composition of the steel material of the present invention mainly includes C, Mn, Al and Si as main elements, and the initial cost is relatively low.

[0041] (2) The present invention adopts a new short-process, low-cost production process of "large proportion of scrap steel + electric furnace smelting + medium-thin slab continuous casting and rolling", which can save energy consumption;

[0042] (3) The hydrogen embrittlement resistant cold-rolled DH1500 steel manufactured by the present invention has a certain proportion of retained austenite added to the conventional cold-rolled dual-phase steel, and has the characteristics of high strength, high plasticity and formability under the action of transformation induced plasticity (TRIP) effect;

[0043] (4) The hydrogen embrittlement resistant cold-rolled DH1500 steel produced by the present invention can add a large amount of aluminum elements to achieve low density of high-strength steel, meeting the requirements of lightweight design of automobiles;

[0044] (5) The hydrogen embrittlement resistant cold-rolled DH1500 steel manufactured by the present invention can realize a set of alloy systems to meet the diversified product requirements such as continuous annealing, continuous hot-dip galvanizing / galvanized aluminum-magnesium and alloyed hot-dip galvanizing due to the special design of composition and process, that is, one steel can be used for multiple purposes, which can significantly save product manufacturing costs. It can not only greatly shorten the product development cycle and R&D costs, but also realize the conversion between multiple grades of products and significantly improve product production efficiency;

[0045] (6) The hydrogen embrittlement resistant cold-rolled DH1500 steel manufactured by the present invention can achieve a yield strength ≥1000MPa, a tensile strength ≥1500MPa, an A80 elongation after fracture ≥11.0%, a hole expansion rate ≥20%, and a density of 6.5-7.5g / cm3; it adopts 180° U-shaped bending to pre-stress and is immersed in 0.5mol / LHCl solution for 14 days without delayed fracture, showing excellent performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is the metallographic microstructure diagram of Example 1-1 of the present invention.

[0047] Figure 2 This is a metallographic microstructure diagram of Example 1-2 of the present invention.

[0048] Figure 3 The microstructure metallographic diagrams of Examples 1-3 of the present invention are shown in FIG.

[0049] Figure 4 The microstructure metallographic diagrams of Examples 1-4 of the present invention are shown in FIG.

[0050] Figure 5 This is the stress-strain curve of Example 1 of the present invention. DETAILED DESCRIPTION

[0051] The present invention will be further described below by way of examples.

[0052] According to the component ratio of the technical solution, the embodiment of the present invention carries out electric furnace smelting, continuous casting and rolling of medium and thin slabs, pickling and cold rolling, continuous annealing or continuous hot-dip process or alloying hot-dip galvanizing and skin pass.

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

[0054] Continuous casting and rolling of medium and thin slabs: using special protective slag for high aluminum steel for casting, casting temperature 1530~1600℃, casting machine pulling speed 1.0~5.5m / min, continuous casting slab thickness 60~115mm;

[0055] The starting rolling temperature is 1000-1150℃, the final rolling temperature is above 900℃, and the coiling temperature is 600-700℃; the hot rolled coil thickness specification is 2.0-4.5mm;

[0056] Pickling cold rolling: cold rolling reduction rate is 45% to 60%;

[0057] After cold rolling, the steel sheet undergoes continuous annealing or continuous hot-dip coating or alloy hot-dip galvanizing;

[0058] Skin finishing: The skin finishing process adopts rolling force control, the rolling force is controlled at 1000-3500kN, and the rolling tension is 500~2000kN.

[0059] Further; continuous annealing: belt speed control 60 ~ 180m / min, soaking section furnace temperature 760 ~ 880 ℃, soaking time 10 ~ 600s, slow cooling outlet temperature 700 ~ 750 ℃, rapid cooling rate greater than 35 ℃ / s, rapid cooling temperature 250 ~ 350 ℃, aging temperature 250 ~ 350 ℃, aging time 60 ~ 1000s.

[0060] Further; the continuous hot-dip process is continuous hot-dip galvanizing or continuous galvanizing aluminum-magnesium;

[0061] The strip speed of continuous hot-dip galvanizing or continuous galvanized aluminum-magnesium is controlled at 60-180m / min: annealing temperature is 760-880℃, dew point temperature is controlled at -20--10℃, annealing time is 30-300s, slow cooling outlet temperature is 680-750℃, rapid cooling rate is greater than 20℃ / s, rapid cooling outlet temperature is 450-470℃, plating solution temperature is 450-470℃, after hot-dip galvanizing, the strip is first air-knife cooled to 400-420℃, and then air-cooled, and the temperature of the cooling tower top roller is controlled at 250-300℃.

[0062] Furthermore, in the continuous hot-dip galvanizing process, the composition of the plating solution is Al: 0.16% to 0.25% by mass, and the rest is Zn and unavoidable impurities. The weight of the zinc layer per unit area of ​​the steel plate after hot-dip galvanizing is 60 to 200 g / cm 2 ;

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

[0064] Further; alloyed hot-dip galvanizing: the strip speed is controlled at 60-180m / min, the annealing temperature is 770-870℃, the annealing time is between 30 and 300s, the dew point is controlled at -20--10℃, the slow cooling outlet temperature is 680-750℃, the rapid cooling rate is greater than 20℃ / s, the rapid cooling outlet temperature is 450-470℃, the galvanizing temperature is 450-470℃, after galvanizing, the strip is first air-knife cooled to 400-420℃, and then alloying treatment is carried out, the alloying temperature is 470-530℃, and the alloying holding time is 5-60s.

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

[0066] Table 1 Composition of steel according to the present invention

[0067]

[0068] Table 2 Main process parameters and hot rolling structure of steel smelting, continuous casting and rolling according to the embodiment of the present invention

[0069]

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

[0071]

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

[0073]

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

[0075]

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

[0077]

[0078] Table 7 Properties of steel according to the present invention

[0079]

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

[0081] Table 8 Microstructure of steel in the embodiment of the present invention

[0082] Example Ferrite / % Martensite / % Retained austenite / % 1-1 23.8 67.1 9.1 2-1 17.1 71.5 11.4 3-1 18.4 72 9.6 4-1 26.5 64.7 8.8 5-1 18.7 74.8 6.5 6-1 20.2 69.2 10.6 1-2 13.3 77.1 9.6 2-2 14.1 75.2 10.7 3-2 16.6 77.8 5.6 4-2 17.5 74.3 8.2 5-2 13.7 77.5 8.8 6-2 14.3 73.1 12.6 1-3 23.6 68.9 7.5 2-3 19.2 74 6.8 3-3 16.5 73.4 10.1 4-3 14.4 78.3 7.3 5-3 18.2 74.2 7.6 6-3 15.3 75.5 9.2 1-4 19.7 74 6.3 2-4 14.7 76.2 9.1 3-4 16.2 78.3 5.5 4-4 23.2 68.7 8.1 5-4 13.6 77.0 9.4 6-4 26.2 69.1 4.7

[0083] In order to describe the present invention, the present invention is appropriately and fully illustrated by the examples in the above. The above implementation modes are only used to illustrate the present invention, but not to limit the present invention. Ordinary technicians in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made should be included in the protection scope of the present invention. The patent protection scope of the present invention should be defined by the claims.

Claims

1. A hydrogen embrittlement resistant cold-rolled DH1500 steel, characterized in that: The components of the steel plate are as follows by weight percentage: C: 0.20%-0.30%, Mn: 2.0%-3.0%, Si: 0.8%-2.0%, Al: 2.83%-8.0%, Mo: 0.56%-0.80%, Cu: 0.64%-0.80%, P≤0.01%, S≤0.01%, N≤0.005%, Mg: 0.173%-0.50%, Ti: 0.031%-0.50%, V: 0.18%-0.50%, and 1≤Al / Si≤10; the rest is iron and unavoidable impurities.

2. The hydrogen embrittlement resistant cold-rolled DH1500 steel according to claim 1, characterized in that: In the DH1500 steel, 5≤Mo / Ti≤10.

3. The hydrogen embrittlement resistant cold-rolled DH1500 steel according to claim 1, characterized in that: The DH1500 steel microstructure is ferrite+martensite+residual austenite, and the volume percentage of each microstructure is as follows: ferrite 13.3%-30%, martensite 50%-80%, and residual austenite 3%-12%; and the residual austenite is in two forms: block and film, with a grain size between 0.05μm and 0.50μm, the blocky residual austenite is mainly distributed at the martensite / ferrite interface and inside the ferrite, and the film-like residual austenite is mainly distributed between the martensite laths.

4. The hydrogen embrittlement resistant cold-rolled DH1500 steel according to claim 1, characterized in that: DH1500 steel yield strength ≥1000MPa, tensile strength ≥1500MPa, A80 elongation ≥11.0%, hole expansion rate ≥20%, density 6.5~7.5g / cm 3 .

5. A method for manufacturing a hydrogen embrittlement resistant cold-rolled DH1500 steel according to any one of claims 1 to 4, characterized in that: Including electric furnace smelting, medium and thin slab continuous casting and rolling, pickling and cold rolling, continuous annealing or continuous hot-dip process or alloy hot-dip galvanizing, skin pass; The composition of DH1500 steel is as follows by weight percentage: C: 0.20% to 0.30%, Mn: 2.0% to 3.0%, Si: 0.8% to 2.0%, Al: 2.83% to 8.0%, Mo: 0.56% to 0.80%, Cu: 0.64% to 0.80%, P≤0.01%, S≤0.01%, N≤0.005%, Mg: 0.173% to 0.50%, Ti: 0.031% to 0.50%, V: 0.18% to 0.50%, and 1≤Al / Si≤10; the rest is iron and unavoidable impurities; Electric furnace smelting: 30% to 70% scrap steel is used as raw material, and the molten steel temperature is 1600 to 1750°C; Continuous casting and rolling of medium and thin slabs: using special protective slag for high aluminum steel for casting, casting temperature 1530~1600℃, casting machine pulling speed 1.0~5.5m / min, continuous casting slab thickness 60~115mm; The starting rolling temperature is 1000-1150℃, the final rolling temperature is above 900℃, and the coiling temperature is 600-700℃; the hot rolled coil thickness specification is 2.0-4.5mm; Pickling cold rolling: cold rolling reduction rate is 45% to 60%; After cold rolling, the steel sheet undergoes continuous annealing or continuous hot-dip coating or alloy hot-dip galvanizing; Skin finishing: The skin finishing process adopts rolling force control, the rolling force is controlled at 1000~3500kN, and the rolling tension is 500~2000kN.

6. The method for manufacturing a hydrogen embrittlement resistant cold-rolled DH1500 steel according to claim 5, characterized in that: Continuous annealing: belt speed control 60 ~ 180m / min, annealing temperature 760 ~ 880℃, soaking time 10 ~ 600s, slow cooling outlet temperature 700 ~ 750℃, rapid cooling rate greater than 35℃ / s, rapid cooling temperature 250 ~ 350℃, aging temperature 250 ~ 350℃, aging time 60 ~ 1000s.

7. The method for manufacturing a hydrogen embrittlement resistant cold-rolled DH1500 steel according to claim 5, characterized in that: The continuous hot-dip process is continuous hot-dip galvanizing or continuous galvanizing aluminum-magnesium; Continuous hot-dip galvanizing or continuous galvanized aluminum-magnesium: belt speed is controlled at 60-180m / min, annealing temperature is 760-880℃, dew point temperature is controlled at -20--10℃, annealing time is 30-300s, slow cooling outlet temperature is 680-750℃, rapid cooling rate is greater than 20℃ / s, rapid cooling outlet temperature is 450-470℃, plating solution temperature is 450-470℃, after hot-dip galvanizing, the strip is first air-knife cooled to 400-420℃, and then air-cooled, and the temperature of the cooling tower top roller is controlled at 250-300℃.

8. The method for manufacturing a hydrogen embrittlement resistant cold-rolled DH1500 steel according to claim 7, characterized in that: In the process of continuous hot-dip galvanizing, the composition of the plating solution is Al: 0.16%~0.25% by mass, and the rest is Zn and unavoidable impurities. The weight of the zinc layer per unit area of ​​the steel plate after hot-dip galvanizing is 60~200g / cm 2 ; In the process of continuous zinc-aluminum-magnesium plating, the composition of the plating solution is calculated by mass percentage: Al: 2.0%~10.0%, Mg: 1.0%~5.0%, Si: 0.001%~0.1%, and the rest is Zn and unavoidable impurities. The weight of the zinc-aluminum-magnesium coating per unit area after hot-dip plating is 50~200g / cm 2 .

9. The method for manufacturing a hydrogen embrittlement resistant cold-rolled DH1500 steel according to claim 5, characterized in that: Alloyed hot-dip galvanizing: the strip speed is controlled at 60-180m / min, the annealing temperature is 770-870℃, the annealing time is between 30 and 300s, the dew point is controlled at -20--10℃, the slow cooling outlet temperature is 680-750℃, the rapid cooling rate is greater than 20℃ / s, the rapid cooling outlet temperature is 450-470℃, the galvanizing temperature is 450-470℃, after galvanizing, the strip is first air-knife cooled to 400-420℃, and then alloying treatment is carried out, the alloying temperature is 470-530℃, and the alloying holding time is 5-60s.

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