A high-hardness corrosion-resistant steel material for structure and its preparation process

Abstract

The present invention relates to the technical field of structural steel, and specifically to a high-hardness, corrosion-resistant steel for structural use and a preparation process thereof. The steel is obtained by rolling, heat treating, and surface treating a steel billet. The steel billet comprises the following components, by mass percentage: C: 0.05-0.09%, Si: 0.05-0.12%, Mn: 1.35-1.60%, Al: 0.02-0.05%, Ti: 0.04-0.11%, Nb: 0.03-0.05%, Mo: 0.15-0.18%, V: 0.004-0.09%, B: ≤0.002%, P: ≤0.015%, S: ≤0.005%, N: ≤0.006%, O: ≤0.003%, and the balance is Fe. The present invention improves the mechanical properties and corrosion resistance of the steel by composite microalloying elements such as niobium, titanium, vanadium, and boron on a low-carbon, manganese-containing steel basis.

Description

Technical Field

[0001] The present invention relates to the technical field of structural steel, in particular to a high-hardness corrosion-resistant steel material for structure and a preparation process thereof. Background Art

[0002] The automotive frame is a major component of a car, supported on the wheels by the front and rear axles of the suspension system. It bears almost the entire weight of the car and its load, and its performance directly affects the service life and driving safety of the entire vehicle. The steel used in automotive frame beams has a weak point in application, namely, it is easily corroded when exposed to air in the natural environment. Without certain protective measures, its service life will be significantly shortened. In the actual production of automotive frame beams, galvanizing is often used as a means of corrosion protection. However, the hot-dip zinc layer on the steel surface will form loose intermetallic compounds with the steel matrix, affecting its hardness and corrosion resistance. Therefore, we propose a high-hardness, corrosion-resistant steel for structural use and a preparation process for it. Summary of the Invention

[0003] The object of the present invention is to provide a high-hardness corrosion-resistant steel material for structure and a preparation process thereof, so as to solve the problems raised in the above background technology.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions: a high-hardness corrosion-resistant steel material for structural use is obtained by rolling, heat treating and surface treating a steel billet;

[0005] Furthermore, the steel billet includes the following components: in percentage by mass, carbon C: 0.05-0.09%, silicon Si: 0.05-0.12%, manganese Mn: 1.35-1.60%, aluminum Al: 0.02-0.05%, titanium Ti: 0.04-0.11%, niobium Nb: 0.03-0.05%, molybdenum Mo: 0.15-0.18%, vanadium V: 0.004-0.09%, boron B: ≤0.002%, phosphorus P: ≤0.015%, sulfur S: ≤0.005%, nitrogen N: ≤0.006%, oxygen O: ≤0.003%, and the balance is iron Fe.

[0006] Furthermore, in terms of mass percentage, in the steel slab composition, Nb+Ti: ≤0.14%; Nb+V+Ti: ≤0.22%; V+B: ≤0.09%.

[0007] In the above technical solution, the steel billet's composition is characterized by low carbon and manganese content, and is compositely microalloyed with elements such as titanium, niobium, molybdenum, and vanadium. Titanium has a strong affinity with the carbon and nitrogen in the steel billet, and its low solubility in steel can influence the deformation and recrystallization of austenite, achieving microstructure refinement. It can also act as a deformation agent for sulfides in the steel, further improving the mechanical properties and anisotropy of the steel billet.

[0008] Niobium also has excellent affinity with carbon and nitrogen, forming fine carbonitrides that effectively inhibit recrystallization and grain growth. Compared to vanadium and titanium, niobium is more effective in inhibiting austenite growth and recrystallization. During the phase transformation process, niobium precipitation increases the ferrite nucleation rate and improves the strength of the steel billet, achieving both grain refinement and precipitation strengthening effects of niobium.

[0009] When niobium and titanium are added together, the amount of niobium added can be reduced, thereby lowering costs. However, a high titanium content can cause the precipitation of a coarse titanium-rich phase, which is detrimental to the overall performance of the steel. Therefore, controlling the niobium and titanium contents promotes the precipitation of small, uniformly distributed niobium and titanium carbonitrides, thereby preventing damage caused by stress concentration during deformation.

[0010] Vanadium can play a role in solid solution, segregation, and precipitation in the steel billet. It interacts with carbon and nitrogen to form carbonitrides in the steel billet matrix and grain boundaries, which strengthens precipitation, inhibits grain growth, and inhibits austenite recrystallization. Compared with niobium and titanium, vanadium has a higher solubility in austenite and less carbonitride precipitation. The solid-solution vanadium is retained in the austenite and precipitates during the subsequent rolling process, achieving a precipitation strengthening effect.

[0011] Niobium carbon and nitrides dissolve in high-temperature austenite and precipitate in low-temperature austenite, hindering the growth of the original austenite. Vanadium carbon and nitrides, on the other hand, dissolve in austenite and precipitate during or after the phase transformation. The precipitated carbonitrides are relatively fine and can pin the austenite grain boundaries, refining the ferrite grains after the phase transformation. This demonstrates the composite microalloying effect of niobium and vanadium in the steel billet.

[0012] Boron has a strong affinity for nitrogen and oxygen, and can combine with sulfur and carbon, forming substitutional or interstitial solid solutions with iron. Boron preferentially segregates at grain boundaries, reducing the segregation of impurity elements such as sulfur and phosphorus at grain boundaries, mitigating intergranular fracture, and improving grain boundary bonding within the steel. Boron can also adsorb on the surfaces of sulfides and oxides, preventing their growth and promoting their refinement and uniform distribution. This alleviates local stress concentration and crack propagation, effectively improving the toughness of the steel. Boron, when combined with vanadium, enhances the drag of niobium on solidification, reducing interfacial migration rates and the driving force for recrystallization, further refining grains, and helping to improve hardenability, impact toughness, high-temperature strength, and creep properties. Excessive boron content in steel can lead to continuous boron deposition at grain boundaries, reducing the impact toughness of the steel.

[0013] The combined addition of vanadium and boron improves the stability of austenite, increases the starting temperature of ferrite transformation, delays phase transformation, and helps to obtain high-strength bainite structure after rolling, so that the steel coil has higher hardness.

[0014] The addition of molybdenum increases the solubility of niobium carbonitrides in austenite, retaining more molybdenum in solid solution and promoting its dispersion and precipitation during low-temperature transformation, thereby exerting a better strengthening effect. Molybdenum can increase the nucleation sites of carbides, promoting the refinement and increase in the number of carbides; and helps improve the corrosion resistance of the steel.

[0015] A process for preparing high-hardness corrosion-resistant steel for structures, comprising the following processes:

[0016] The steel billet is rolled, heat treated and surface treated in sequence to obtain high-hardness corrosion-resistant steel.

[0017] Furthermore, the thickness of the steel billet is 32 to 55 mm.

[0018] Furthermore, the rolling process is as follows: heating the steel billet to 1230-1270° C. and holding the temperature for 60 minutes; the rough rolling start temperature is 1130-1160° C. and the finishing temperature is 860-880° C.; the number of passes is 5-8, and the reduction of the first pass is 13-16%;

[0019] Then, the steel is cooled to 600-630°C at a cooling rate of 18-25°C / s and coiled to obtain a steel coil.

[0020] Furthermore, the thickness of the steel coil is 2 to 6 mm.

[0021] In the above technical solution, the steel slab is rolled to produce the coil. During the hot rolling and cooling process, stress deformation and high-temperature rapid cooling promote phase transformation in the steel structure. Bainite and ferrite are formed in the austenite, and carbon is expelled into the austenite.

[0022] The steel billet structure forms a high-density dislocation, and during relaxation, a fine dislocation cellular structure is formed. Elements such as niobium and titanium are strain-induced to precipitate within this structure. Molybdenum has a certain refining effect on the precipitates, creating numerous nucleation sites, promoting the formation of bainite in the steel billet, and segmenting and refining the deformed austenite grains. Molybdenum raises the austenite transformation temperature, shrinks the austenite phase region, expands the bainite phase region, and promotes bainite formation. The refined grains inhibit phase transformation, refining the structure to a certain extent. This allows for the precipitation and refinement of acicular ferrite and bainite in the coil structure, exerting a phase transformation strengthening effect and improving the coil's mechanical properties.

[0023] Furthermore, the heat treatment process is as follows: the heat treatment temperature is 450-600° C., and the insulation time is 135-180 minutes.

[0024] In the above technical solution, the steel coil is tempered after hot rolling to eliminate residual stresses in the coil and stabilize the matrix structure. At the heat treatment temperature, carbon and nitrides of alloying elements such as titanium and niobium precipitate, increasing their number and exerting a precipitation strengthening effect. As the tempering temperature increases, the particle size of these carbon and nitrides gradually decreases, improving the mechanical properties of the steel coil. However, if the tempering temperature is too high, the precipitates coarsen and grow, which is detrimental to improving the coil's performance.

[0025] Furthermore, the surface treatment includes powder spraying and hot-dip galvanizing.

[0026] Furthermore, the process conditions for powder spraying are: air flow rate 88-90 L / min, propane flow rate 80-85 L / min, hydrogen flow rate 33-38 L / min, and nitrogen flow rate 28-32 L / min;

[0027] The spraying distance is 20 cm, the spraying angle is 90°, the powder feeding rate is 45-60 g / min, and the spraying speed is 800-1000 mm / s.

[0028] Furthermore, the spraying powder is obtained by mixing boride powder, cobalt powder, iron powder, polyethylene glycol and anhydrous ethanol, ball milling, vacuum drying and sintering.

[0029] Furthermore, the mass ratio of boride powder, cobalt powder, and iron powder is (66.9-84.4):(8-17):(7.6-16.1);

[0030] Polyethylene glycol is 1% of the total mass of boride powder, cobalt powder and iron powder;

[0031] The total volume of anhydrous ethanol, boride powder, cobalt powder and iron powder is the same.

[0032] Furthermore, the process conditions of ball milling are: rotation speed 200-240 r / min, duration 8-10 h;

[0033] The process conditions of vacuum drying are: temperature 75-80℃, time 8-10h;

[0034] The sintering process conditions are as follows: heating to 300-320°C at a heating rate of 1-2°C / min, keeping warm for 60-80 min; heating to 420-430°C, keeping warm for 60-80 min;

[0035] Heat to 1160-1180°C at a heating rate of 9-10°C / min, keep warm for 120-130 minutes; heat to 1250-1270°C, keep warm for 150-160 minutes;

[0036] After sintering, the product is crushed, ground and sieved to retain the powder with a particle size of 37 to 48 μm.

[0037] Furthermore, the boride powder is prepared by the following process:

[0038] The chromium boride and aluminum powder are mixed, added with anhydrous ethanol, ball-milled, dried, passed through a 120-mesh sieve, pressed into blocks, and sintered to obtain the product.

[0039] Furthermore, the mass ratio of chromium boride to aluminum powder is 10:(2.5-6.5);

[0040] The total volume of anhydrous ethanol, chromium boride and aluminum powder is the same.

[0041] Furthermore, the process conditions of ball milling are: rotation speed 300-400 rpm, duration 4-6 h;

[0042] Drying temperature is 40-50℃;

[0043] The process conditions for briquetting are: applying pressure of 80-100 MPa and maintaining pressure for 10-15 minutes;

[0044] The sintering process conditions are as follows: heating to 950-1000°C at a heating rate of 9-10°C / min under nitrogen atmosphere, keeping the temperature for 180-200 minutes, and cooling with the furnace;

[0045] After sintering, the product is crushed, ground and sieved to retain the powder with a particle size of 37 to 48 μm.

[0046] Further, the hot dip galvanizing process is as follows:

[0047] The steel coil obtained after powder spraying is heated to 460-480°C, placed in zinc liquid, hot-dip plated for 3-5 seconds, pulled out, purged with nitrogen, and cooled to room temperature at a cooling rate of 100°C / s to obtain a coating.

[0048] Furthermore, the temperature of the zinc solution is 450-460°C;

[0049] The zinc liquid comprises the following components: in percentage by mass, silicon Si: 0.1-0.5%, aluminum Al: 4.0-8.0%, and the balance is zinc Zn.

[0050] In the above technical solution, during hot-dip galvanizing, a complex physical and chemical reaction occurs between the steel surface and the incorporated aluminum. The zinc atoms combine with the iron atoms to form a hard and brittle intermetallic compound (Γ phase), which can effectively prevent the zinc liquid from dissolving and further penetrating the steel matrix, slowing down the diffusion process. Iron atoms and zinc atoms diffuse in the Γ phase to form the δ phase, which is strong and has toughness and ductility. The δ phase has certain pores, which accelerate the diffusion of zinc atoms and react with the δ phase to form the ζ phase. The ζ phase is bundle-shaped and relatively loose. It is easy to fall off and peel off under thermal convection and the scouring of zinc liquid. Therefore, the present application performs powder spraying on the steel coil before hot-dip galvanizing. The spraying powder contains boride, which is sprayed at high speed to impact the steel coil, ceramicizing the surface of the steel coil, which can significantly improve the surface hardness, thermal stability, corrosion resistance, wear resistance and other properties of the steel coil. Cobalt can form a continuous solid solution with iron to form a soft and tough phase, thereby improving the bonding ability between the coating and the steel coil; and helps to improve the adhesion of the coating to the surface of the steel coil. Boride is prepared from chromium boride and aluminum powder. Aluminum is introduced into the chromium boride through sintering, forming a Cr-Al-B powder. This reduces the brittleness of the boride, allowing the resulting steel to achieve high surface hardness and strength while also possessing good toughness and modulus. This also contributes to better corrosion resistance. Furthermore, the coating applied to the steel surface reduces notch sensitivity, helping to improve notch impact performance.

[0051] During hot-dip galvanizing, the spray powder combines with the zinc solution, which forms metallic bonds with elements such as iron and cobalt to form an intermediate layer. This effectively improves the surface hardness and corrosion resistance of the resulting steel. Furthermore, the zinc solution has difficulty diffusing across the coating surface, effectively reducing the formation of loose iron-aluminum phases. The aluminum in the zinc solution significantly improves the surface corrosion resistance of the steel. However, excessive aluminum can lead to an excess of brittle Fe-Al compounds on the steel surface, compromising the adhesion between the coating and the coil. The small amount of silicon in the zinc solution inhibits the growth of Fe-Al compounds, improving the adhesion between the coating and the coil.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] 1. The present invention describes a high-hardness, corrosion-resistant steel for structural use. The steel is micro-alloyed with niobium, titanium, vanadium, boron and other elements based on low-carbon, manganese-containing steel to improve its mechanical properties and corrosion resistance.

[0054] 2. The high-hardness, corrosion-resistant steel for structure described in the present invention is powder-coated and hot-dip galvanized on the steel coils obtained after hot rolling and tempering, and a boride-containing coating and a zinc layer are provided on the surface of the steel coils to achieve improved surface hardness and corrosion resistance of the steel, and help improve the steel's sensitivity to notches. DETAILED DESCRIPTION

[0055] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0056] In the following specific embodiments, the thickness of the steel billet is 32 mm; the thickness of the steel coil is 5 mm;

[0057] Chromium boride: average particle size 1.8 μm, purity > 98.5%, sourced from Zhongke Jinyan (Beijing) Technology Co., Ltd.

[0058] Aluminum powder: particle size 300 mesh, sourced from Beikuang New Materials Technology Co., Ltd.

[0059] Cobalt powder: average particle size 2.3 μm, purity 99.8%, sourced from Nanjing Hanrui Cobalt Co., Ltd.

[0060] Iron powder: average particle size 5 μm, sourced from China Science and Technology Research (Beijing) Technology Co., Ltd.

[0061] Example 1: A process for preparing high-hardness corrosion-resistant steel for structural use, comprising the following steps:

[0062] Step 1, rolling: heating the steel billet to 1230°C and holding it for 60 minutes; rough rolling starts at 1130°C and finishes at 860°C; the number of passes is 8, with a first-pass reduction of 13%; then cooling to 600°C at a cooling rate of 18°C / s and coiling; tempering at 450°C and holding it for 135 minutes to obtain a steel coil;

[0063] The steel slab includes the following components: in mass percentage, C: 0.08%, Si: 0.07%, Mn: 1.38%, Al: 0.03%, Ti: 0.08%, Nb: 0.03%, Mo: 0.17%, V: 0.07%, B: 0.0017%, P: 0.010%, S: 0.002%, N: 0.003%, O: 0.001%, and the balance is Fe;

[0064] Step 2: Surface treatment:

[0065] (1) Powder coating:

[0066] Chromium boride and aluminum powder were mixed in a mass ratio of 10:2.5 and anhydrous ethanol was added; the mixture was ball-milled at 300 rpm for 6 hours; dried at 40°C and passed through a 120-mesh sieve; a pressure of 80 MPa was applied and maintained for 15 minutes to form a cylindrical compact with a diameter of 50 mm; sintering was carried out under a nitrogen atmosphere at a heating rate of 9°C / min to 950°C, maintained at this temperature for 180 minutes, and cooled in the furnace; after sintering, the mixture was crushed, ground, and sieved to retain a particle size of 37-48 μm to obtain a boride powder; the total volume of anhydrous ethanol, chromium boride, and aluminum powder was the same;

[0067] The boride powder, cobalt powder and iron powder were mixed in a mass ratio of 84.4:8:7.6, polyethylene glycol and anhydrous ethanol were added, and the mixture was ball-milled at a speed of 200 r / min for 10 hours; vacuum dried at 75°C for 10 hours, and sintered. The sintering process conditions were as follows: heating to 300°C at a heating rate of 1°C / min, holding for 60 minutes; heating to 420°C, holding for 60 minutes; heating to 1160°C at a heating rate of 9°C / min, holding for 120 minutes; heating to 1250°C, holding for 150 minutes; after sintering, the mixture was crushed, ground and sieved to retain powder with a particle size of 37 to 48 μm to obtain a spray powder; the polyethylene glycol was 1% of the total mass of the boride powder, cobalt powder and iron powder; and the total volume of anhydrous ethanol was the same as that of the boride powder, cobalt powder and iron powder.

[0068] The coating was formed by spraying powder on the surface of the steel coil under the following process conditions: air flow rate 89 L / min, propane flow rate 82 L / min, hydrogen flow rate 35 L / min, nitrogen flow rate 30 L / min; spraying distance 20 cm, spraying angle 90°, powder feed rate 45 g / min, spraying speed 800 mm / s;

[0069] (2) Hot dip galvanizing:

[0070] The powder-sprayed steel coil is heated to 460°C, placed in a 450°C zinc bath, hot-dip plated for 4 seconds, pulled out, purged with nitrogen, and cooled to room temperature at a cooling rate of 100°C / s to form a coating, thereby obtaining a high-hardness, corrosion-resistant steel. The zinc bath comprises the following components, by mass percentage: 0.2% Si, 4.1% Al, and the balance Zn.

[0071] Example 2: A process for preparing high-hardness corrosion-resistant steel for structural use, comprising the following steps:

[0072] Step 1, rolling: heating the steel billet to 1250°C and holding it for 60 minutes; rough rolling starts at 1145°C and finishes at 870°C; the number of passes is 8, with a first-pass reduction of 15%; then cooling to 615°C at a cooling rate of 20°C / s and coiling; tempering at 525°C and holding it for 160 minutes to obtain a steel coil;

[0073] The steel slab includes the following components: in mass percentage, C: 0.08%, Si: 0.07%, Mn: 1.38%, Al: 0.03%, Ti: 0.08%, Nb: 0.03%, Mo: 0.17%, V: 0.07%, B: 0.0017%, P: 0.010%, S: 0.002%, N: 0.003%, O: 0.001%, and the balance is Fe;

[0074] Step 2: Surface treatment:

[0075] (1) Powder coating:

[0076] Chromium boride and aluminum powder were mixed in a mass ratio of 10:4.5, and anhydrous ethanol was added; the mixture was ball-milled at 350 rpm for 5 hours; dried at 45°C, and passed through a 120-mesh sieve; a pressure of 90 MPa was applied and maintained for 12 minutes to form a cylindrical compact with a diameter of 50 mm; sintering: Under a nitrogen atmosphere, the mixture was heated to 980°C at a heating rate of 9°C / min, maintained at this temperature for 190 minutes, and cooled in the furnace; after sintering, the mixture was crushed, ground, and sieved to retain a particle size of 37-48 μm to obtain a boride powder; the total volume of anhydrous ethanol, chromium boride, and aluminum powder was the same;

[0077] The boride powder, cobalt powder and iron powder were mixed in a mass ratio of 76.2:12:11.8, polyethylene glycol and anhydrous ethanol were added, and the mixture was ball-milled at a speed of 220 r / min for 9 hours; vacuum dried at 78°C for 9 hours, and sintered. The sintering process conditions were as follows: heating to 310°C at a heating rate of 1°C / min and holding for 70 minutes; heating to 425°C and holding for 70 minutes; heating to 1170°C at a heating rate of 9°C / min and holding for 125 minutes; heating to 1260°C and holding for 155 minutes; after sintering, the mixture was crushed, ground and sieved to retain powder with a particle size of 37 to 48 μm to obtain a spray powder; the polyethylene glycol was 1% of the total mass of the boride powder, cobalt powder and iron powder; and the total volume of anhydrous ethanol was the same as that of the boride powder, cobalt powder and iron powder.

[0078] The coating was formed by spraying powder on the surface of the steel coil under the following process conditions: air flow rate 89 L / min, propane flow rate 82 L / min, hydrogen flow rate 35 L / min, nitrogen flow rate 30 L / min; spraying distance 20 cm, spraying angle 90°, powder feed rate 50 g / min, spraying speed 900 mm / s;

[0079] (2) Hot dip galvanizing:

[0080] The powder-sprayed steel coil is heated to 470°C, placed in a 455°C zinc bath, hot-dip plated for 3 seconds, pulled out, purged with nitrogen, and cooled to room temperature at a cooling rate of 100°C / s to form a coating, thereby obtaining a high-hardness, corrosion-resistant steel. The zinc bath comprises the following components, by mass percentage: 0.3% Si, 6.2% Al, and the balance Zn.

[0081] Example 3: A process for preparing high-hardness corrosion-resistant steel for structural use, comprising the following steps:

[0082] Step 1, rolling: heating the steel billet to 1270°C and holding it for 60 minutes; rough rolling starts at 1160°C and finishes at 880°C; the number of passes is 8, with a first-pass reduction of 13%; then cooling to 630°C at a cooling rate of 25°C / s and coiling; tempering at 600°C and holding it for 180 minutes to obtain a steel coil;

[0083] The steel slab includes the following components: in mass percentage, C: 0.08%, Si: 0.07%, Mn: 1.38%, Al: 0.03%, Ti: 0.08%, Nb: 0.03%, Mo: 0.17%, V: 0.07%, B: 0.0017%, P: 0.010%, S: 0.002%, N: 0.003%, O: 0.001%, and the balance is Fe;

[0084] Step 2: Surface treatment:

[0085] (1) Powder coating:

[0086] Chromium boride and aluminum powder were mixed in a mass ratio of 10:6.5, and anhydrous ethanol was added; the mixture was ball-milled at 400 rpm for 4 hours; dried at 50°C, and passed through a 120-mesh sieve; a pressure of 100 MPa was applied and maintained for 15 minutes to form a cylindrical compact with a diameter of 50 mm; sintered: under a nitrogen atmosphere, heated to 1000°C at a heating rate of 10°C / min, maintained for 200 minutes, and cooled in the furnace; after sintering, the mixture was crushed, ground, and sieved to retain a powder with a particle size of 37-48 μm to obtain a boride powder; the total volume of anhydrous ethanol, chromium boride, and aluminum powder was the same;

[0087] The boride powder, cobalt powder and iron powder were mixed in a mass ratio of 66.9:17:16.1, polyethylene glycol and anhydrous ethanol were added, and the mixture was ball-milled at a speed of 240 r / min for 8 hours; vacuum dried at 80°C for 10 hours, and sintered. The sintering process conditions were as follows: heating to 320°C at a heating rate of 2°C / min, holding for 80 minutes; heating to 430°C, holding for 80 minutes; heating to 1180°C at a heating rate of 10°C / min, holding for 130 minutes; heating to 1270°C, holding for 160 minutes; after sintering, the mixture was crushed, ground and sieved to retain powder with a particle size of 37 to 48 μm to obtain a spray powder; the polyethylene glycol was 1% of the total mass of the boride powder, cobalt powder and iron powder; the total volume of anhydrous ethanol was the same as that of the boride powder, cobalt powder and iron powder;

[0088] The coating was formed by spraying powder on the surface of the steel coil under the following process conditions: air flow rate 89 L / min, propane flow rate 82 L / min, hydrogen flow rate 35 L / min, nitrogen flow rate 30 L / min; spraying distance 20 cm, spraying angle 90°, powder feed rate 60 g / min, spraying speed 1000 mm / s;

[0089] (2) Hot dip galvanizing:

[0090] The powder-sprayed steel coil is heated to 480°C, placed in a 460°C zinc bath, hot-dip plated for 5 seconds, pulled out, purged with nitrogen, and cooled to room temperature at a cooling rate of 100°C / s to form a coating, thereby obtaining a high-hardness, corrosion-resistant steel. The zinc bath comprises the following components, by mass percentage: 0.48% Si, 7.8% Al, and the balance Zn.

[0091] Comparative Example 1: A process for preparing high-hardness corrosion-resistant steel for structural use, comprising the following processes:

[0092] Step 1 is the same as in Example 1, obtaining a steel coil;

[0093] Step 2, surface treatment: (1) powder spraying:

[0094] Chromium boride and aluminum powder were mixed in a mass ratio of 10:2.5 and anhydrous ethanol was added; the mixture was ball-milled at 300 rpm for 6 hours; dried at 40°C and passed through a 120-mesh sieve; a pressure of 80 MPa was applied and maintained for 15 minutes to form a cylindrical compact with a diameter of 50 mm; sintering was carried out under a nitrogen atmosphere at a heating rate of 9°C / min to 950°C, maintained at this temperature for 180 minutes, and cooled in the furnace; after sintering, the mixture was crushed, ground, and sieved to retain a particle size of 37-48 μm to obtain a boride powder; the total volume of anhydrous ethanol, chromium boride, and aluminum powder was the same;

[0095] Boride powder and iron powder with a mass ratio of 91.7:8.3 were mixed, polyethylene glycol and anhydrous ethanol were added, and the mixture was ball-milled at a speed of 200 r / min for 10 hours; vacuum dried at 75°C for 10 hours, and sintered. The sintering process conditions were as follows: heating to 300°C at a heating rate of 1°C / min, holding for 60 minutes; heating to 420°C, holding for 60 minutes; heating to 1160°C at a heating rate of 9°C / min, holding for 120 minutes; heating to 1250°C, holding for 150 minutes; after sintering, the mixture was crushed, ground, and sieved to retain powder with a particle size of 37 to 48 μm to obtain a spray powder; the polyethylene glycol was 1% of the total mass of the boride powder and iron powder; and the total volume of anhydrous ethanol was the same as that of the boride powder and iron powder.

[0096] The coating was formed by spraying powder on the surface of the steel coil under the following process conditions: air flow rate 89 L / min, propane flow rate 82 L / min, hydrogen flow rate 35 L / min, nitrogen flow rate 30 L / min; spraying distance 20 cm, spraying angle 90°, powder feed rate 45 g / min, spraying speed 800 mm / s;

[0097] (2) Hot-dip galvanizing is the same as in Example 1 to form a coating to obtain a high-hardness, corrosion-resistant steel material.

[0098] Comparative Example 2: A process for preparing high-hardness corrosion-resistant steel for structural use, comprising the following processes:

[0099] Step 1 is the same as in Example 1, obtaining a steel coil;

[0100] Step 2, surface treatment: (1) powder spraying:

[0101] Chromium boride and iron powder are mixed in a mass ratio of 92.4:7.6, polyethylene glycol and anhydrous ethanol are added, and the mixture is ball-milled at a speed of 200 r / min for 10 hours; vacuum dried at 75°C for 10 hours, and sintered. The sintering process conditions are as follows: heating to 300°C at a heating rate of 1°C / min, holding for 60 minutes; heating to 420°C, holding for 60 minutes; heating to 1160°C at a heating rate of 9°C / min, holding for 120 minutes; heating to 1250°C, holding for 150 minutes; after sintering, the mixture is crushed, ground, and sieved to retain powder with a particle size of 37 to 48 μm to obtain a spray powder; the polyethylene glycol is 1% of the total mass of the chromium boride and iron powder; the total volume of anhydrous ethanol is the same as that of the chromium boride and iron powder;

[0102] The coating was formed by spraying powder on the surface of the steel coil under the following process conditions: air flow rate 89 L / min, propane flow rate 82 L / min, hydrogen flow rate 35 L / min, nitrogen flow rate 30 L / min; spraying distance 20 cm, spraying angle 90°, powder feed rate 45 g / min, spraying speed 800 mm / s;

[0103] (2) Hot-dip galvanizing is the same as in Example 1 to form a coating to obtain a high-hardness, corrosion-resistant steel material.

[0104] Comparative Example 3: A process for preparing high-hardness corrosion-resistant steel for structural use, comprising the following processes:

[0105] Step 1 is the same as in Example 1, obtaining a steel coil;

[0106] Step 2, hot dip galvanizing:

[0107] The steel coil obtained after powder spraying is heated to 460°C, sent to 450°C zinc liquid, hot-dip coated for 4 seconds, pulled out, purged with nitrogen, and cooled to room temperature at a cooling rate of 100°C / s to form a coating to obtain a high-hardness corrosion-resistant steel; the zinc liquid includes the following components: Si: 0.2%, Al: 4.1%, chromium boride: 2.0%, and the balance Zn

[0108] Step 2: Hot-dip galvanizing is the same as in Example 1 to form a coating to obtain a high-hardness, corrosion-resistant steel.

[0109] Comparative Example 4: A process for preparing high-hardness corrosion-resistant steel for structural use, comprising the following processes:

[0110] The steel slab was heated to 1230°C and held at that temperature for 60 minutes. The rough rolling temperature was 1130°C and the finishing temperature was 860°C. The number of passes was 5, and the reduction of the first pass was 13%. The steel slab was then cooled to 600°C at a cooling rate of 18°C / s and coiled. The steel slab was tempered at 450°C and held at that temperature for 135 minutes to obtain a steel coil.

[0111] The steel billet includes the following components: in mass percentage, C: 0.08%, Si: 0.07%, Mn: 1.45%, Al: 0.05%, Ti: 0.12%, Nb: 0.04%, Mo: 0.15%, P: 0.012%, S: 0.002%, N: 0.004%, O: 0.001%, and the balance is Fe.

[0112] Experiment: The steel coils and high-hardness corrosion-resistant steel obtained in Examples 1-3 and Comparative Examples 1-4 were used to prepare samples, and their properties were tested and the test results were recorded:

[0113] Hardness test: Using GB / T 4340.1 as the reference standard, the Vickers hardness of high-hardness corrosion-resistant steel samples (the steel coil samples in Comparative Example 4) was tested. The load was applied for 10 seconds, and eight different locations on the sample surface were tested. The average value was taken as the test result.

[0114] Corrosion resistance test: The sample was placed in a salt spray chamber to test the corrosion resistance of the high hardness corrosion resistant steel (the steel coil sample in Comparative Example 4). The temperature in the salt spray chamber was 35°C, the relative humidity was 90%, and the temperature was 100°C per 80cm. 2 The salt spray deposition is 2.0 mL / h, and the salt spray is 5 wt% sodium chloride solution. The time for the sample to develop red rust in the salt spray test is observed.

[0115] Tensile performance test: GB / T 228.1 is used as the reference standard, and a tensile testing machine is used to test the yield strength and tensile strength of the steel coil sample; the tensile speed is 5mm / min;

[0116] Impact performance test: Using standard Charpy V-notch specimens, the low-temperature impact energy of high-hardness corrosion-resistant steel specimens (steel coil specimens in Comparative Example 4) was tested on a pendulum impact tester; the test temperature was -20°C.

[0117] Vickers hardness (HV) Yield strength (MPa) Tensile strength (MPa) Impact energy (J) Corrosion resistance time (h) Example 1 303 785 818 232 2500 Example 2 320 780 813 240 2700 Example 3 341 776 807 238 2800 Comparative Example 1 288 \ \ 184 2200 Comparative Example 2 326 \ \ 171 2100 Comparative Example 3 224 \ \ 152 1700 Comparative Example 4 280 745 806 120 96

[0118] According to the data in the above table, we can clearly draw the following conclusions:

[0119] The high hardness corrosion-resistant steel coils obtained in Examples 1-3 were compared with the high hardness corrosion-resistant steel coils obtained in Comparative Examples 1-3 and the steel coils obtained in Comparative Example 4. The test results show that:

[0120] Compared to the comparative example, the steel coils and high-hardness, corrosion-resistant steels obtained in Examples 1-3 exhibited significantly higher Vickers hardness, yield strength, tensile strength, impact energy, and corrosion resistance time. This demonstrates that the present invention improves the mechanical properties of the steel coils and the impact toughness, surface hardness, and corrosion resistance of the high-hardness, corrosion-resistant steel.

[0121] Compared to Example 1, the spray powder in Comparative Example 1 was prepared from boride and iron powder; the spray powder in Comparative Example 2 was prepared from chromium boride and iron powder; and the surface treatment process in Comparative Example 3 was hot-dip galvanizing, with the zinc bath containing chromium boride. The high-hardness, corrosion-resistant steels obtained in Comparative Examples 1-3 exhibited different surface treatment processes, resulting in lower Vickers hardness, impact energy, and corrosion resistance time. This indicates that the present application's selection of steel surface treatment processes and the components used can improve notch sensitivity, surface hardness, and corrosion resistance.

[0122] The high-hardness, corrosion-resistant steels obtained in Examples 1-3 were compared with the steel coil obtained in Comparative Example 4. The steel coil obtained in Comparative Example 4 had a different billet composition than that of Examples 1-3. Test results showed that the steel coil obtained in Comparative Example 4 had lower yield strength and tensile strength. This indicates that the compositional changes in the billet used in this application contribute to improved mechanical properties.

[0123] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include," "comprise," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0124] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A high-hardness corrosion-resistant steel material for structure, characterized in that: The steel material is obtained by rolling, heat treatment and surface treatment of steel billets; The steel billet comprises the following components: in percentage by mass, C: 0.05-0.09%, Si: 0.05-0.12%, Mn: 1.35-1.60%, Al: 0.02-0.05%, Ti: 0.04-0.11%, Nb: 0.03-0.05%, Mo: 0.15-0.18%, V: 0.004-0.09%, B: ≤0.002%, P: ≤0.015%, S: ≤0.005%, N: ≤0.006%, O: ≤0.003%, and the balance is Fe; The steel preparation process includes: heating a steel billet to 1230-1270°C and holding the temperature for 60 minutes; performing rough rolling at a starting rolling temperature of 1130-1160°C and a finishing rolling temperature of 860-880°C; performing 5-8 passes, with a first-pass reduction of 13-16%; cooling to 600-630°C at a cooling rate of 18-25°C / s, coiling, and heat treating to obtain a steel coil; then performing powder spraying and hot-dip galvanizing in sequence to obtain a high-hardness, corrosion-resistant steel; wherein the hot-dip galvanizing zinc solution comprises the following components, by mass percentage, silicon (Si): 0.1-0.5%, aluminum (Al): 4.0-8.0%, and the balance zinc (Zn); The process conditions for the powder spraying are: air flow rate 88-90 L / min, propane flow rate 80-85 L / min, hydrogen flow rate 33-38 L / min, nitrogen flow rate 28-32 L / min; spraying distance 20 cm, spraying angle 90°, powder feed rate 45-60 g / min, spraying speed 800-1000 mm / s; The spray powder is obtained by mixing boride powder, cobalt powder, iron powder, polyethylene glycol and anhydrous ethanol, ball milling, vacuum drying and sintering; The mass ratio of the boride powder, cobalt powder and iron powder is (66.9-84.4): (8-17): (7.6-16.1), and the boride powder is prepared by the following process: mixing chromium boride and aluminum powder in a mass ratio of 10: (2.5-6.5), adding anhydrous ethanol, ball milling, drying, passing through a 120-mesh sieve, briquetting, sintering, and crushing, grinding and sieving after sintering to retain powder with a particle size of 37-48 μm.

2. The high-hardness corrosion-resistant steel material for structure according to claim 1, characterized in that: In terms of mass percentage, in the steel billet composition, Nb+Ti: ≤0.14%; Nb+V+Ti: ≤0.22%; V+B: ≤0.09%.

3. A process for preparing a high-hardness corrosion-resistant steel for structure, for preparing the high-hardness corrosion-resistant steel for structure as claimed in any one of claims 1 or 2, characterized in that: Including the following processes: Heat the steel billet to 1230-1270℃ and keep it warm for 60min; the starting temperature of rough rolling is 1130-1160℃, and the finishing temperature is 860-880℃; the number of passes is 5-8, and the reduction of the first pass is 13-16%; Cooling to 600-630°C at a cooling rate of 18-25°C / s, coiling, and heat treating to obtain a steel coil; Then, powder spraying and hot-dip galvanizing are performed in sequence to obtain a high-hardness, corrosion-resistant steel material, wherein the hot-dip galvanizing zinc solution comprises the following components: in mass percentage, silicon Si: 0.1-0.5%, aluminum Al: 4.0-8.0%, and the balance is zinc Zn; The process conditions for the powder spraying are: air flow rate 88-90 L / min, propane flow rate 80-85 L / min, hydrogen flow rate 33-38 L / min, nitrogen flow rate 28-32 L / min; spraying distance 20 cm, spraying angle 90°, powder feed rate 45-60 g / min, spraying speed 800-1000 mm / s; The spray powder is obtained by mixing boride powder, cobalt powder, iron powder, polyethylene glycol, and anhydrous ethanol, ball milling, vacuum drying, and sintering; wherein the mass ratio of the boride powder, cobalt powder, and iron powder is (66.9-84.4):(8-17):(7.6-16.1).

4. The process for preparing a high-hardness corrosion-resistant steel material for structure according to claim 3, characterized in that: The process conditions of the heat treatment are: temperature 450-600° C., and insulation time 135-180 minutes.

5. The process for preparing a high-hardness corrosion-resistant steel material for structure according to claim 4, characterized in that: The sintering process conditions are: heating to 300-320°C at a heating rate of 1-2°C / min, keeping warm for 60-80 minutes; heating to 420-430°C, keeping warm for 60-80 minutes; Heat to 1160-1180°C at a heating rate of 9-10°C / min, keep warm for 120-130 minutes; heat to 1250-1270°C, keep warm for 150-160 minutes; After sintering, the product is crushed, ground and sieved to retain the powder with a particle size of 37 to 48 μm.

6. The process for preparing a high-hardness corrosion-resistant steel material for structure according to claim 5, characterized in that: The sintering process conditions are: heating to 950-1000° C. at a heating rate of 9-10° C. / min under nitrogen atmosphere, keeping the temperature for 180-200 minutes, and cooling with the furnace.