High-strength high-toughness antioxidant hot forming steel and mechanical metallurgy preparation method thereof

Abstract

The invention discloses high-strength high-toughness antioxidant hot forming steel and a mechanical metallurgy preparation method thereof. The hot forming steel comprises the following components: 0.20 to 0.30 percent of C, 1.00 to 1.80 percent of Mn, 2.00 to 2.50 percent of Cr, 0.60 to 1.20 percent of Si, 0.60 to 1.20 percent of Al, 0.05 to 0.20 percent of Nb, 0.05 to 0.20 percent of V, less than or equal to 0.01 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.003 percent of N and the balance of Fe and inevitable impurities. The preparation method comprises the steps that molten steel is smelted according to the chemical components, and then a slab is prepared through continuous casting; and the plate blank is sequentially subjected to heating pretreatment, descaling treatment and hot forming treatment, and the hot forming steel is obtained. Through cooperation of chemical components and the preparation method, the hot forming steel with excellent oxidation resistance and excellent obdurability is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of steel materials, and in particular to a high-strength, high-toughness, oxidation-resistant hot-formed steel and a mechanical and metallurgical preparation method thereof. Background Art

[0002] In recent years, the lightweighting of automobiles has played an increasingly critical role, and hot-formed steel is one of the highest-strength steels used in automobile body structures. Hot-formed steel is formed in the austenite region using a hot forming process, with a small amount of springback, which can meet the requirements of assembly accuracy. Ultra-high-strength components of 1500MPa and above can be obtained through pressure-holding quenching. However, due to the high heating temperature of the hot stamping process, the surface of the high-strength steel plate undergoes severe high-temperature oxidation and a large amount of iron oxide scale appears. The hard iron oxide scale will damage the mold surface and reduce the service life of the mold. At the same time, since the loose iron oxide scale on the surface is not conducive to the subsequent painting treatment, shot peening equipment is required to eliminate the surface iron oxide scale. Shot peening will cause deformation of the surface of the parts, further increasing the production cost. Another treatment method is to add aluminum-silicon coating or zinc-based coating, which can prevent the generation of iron oxide scale during the heating process, but the cost is high and it is easy to cause hydrogen embrittlement.

[0003] In order to solve the surface oxidation and decarburization problems in the hot forming process, reduce the production process and reduce the production cost, the patent with the patent announcement number CN116200655A discloses an oxidation-resistant hot forming steel and its production method. The synergistic effect of elements such as Mn, Cr, and Si improves the oxidation resistance of the steel and avoids the subsequent shot peening treatment. The yield strength of the hot forming steel is ≥1000MPa, the tensile strength is ≥1500MPa, and the elongation is ≥6%. The addition of B element improves the hardenability of the material. The structure of the hot forming steel is a full martensite structure, which limits the plasticity of the steel. The patent with the patent announcement number CN116334489A proposes a hot forming steel with ultra-high oxidation resistance. The rare earth elements RE and Cu are introduced to improve the oxidation resistance of the hot forming steel. The cost is reduced by reducing the content of expensive alloy elements such as Cr and Mo. The strength of the hot forming steel reaches 1500MPa and above, but the addition of rare earth elements still makes the hot forming steel have a high cost. In addition, the existing preparation processes of hot-formed steel are often complicated and difficult to apply to actual production. Therefore, how to improve the strength and plasticity of hot-formed steel while ensuring the anti-oxidation performance, and how to reduce the production cost, simplify the production process, and improve the production efficiency are the current research focuses of technicians in this field. Summary of the invention

[0004] The purpose of the present invention is to provide a high-strength, high-toughness, oxidation-resistant hot-formed steel and a mechanical and metallurgical preparation method thereof, so as to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention: a high-strength, high-toughness, oxidation-resistant hot-formed steel, wherein the chemical composition of the high-strength, high-toughness, oxidation-resistant hot-formed steel is as follows, by mass percentage: C: 0.20-0.30%, Mn: 1.00-1.80%, Cr: 2.00-2.50%, Si: 0.60-1.20%, Al: 0.60-1.20%, Nb: 0.05-0.20%, V: 0.05-0.20%, P≤0.01%, S≤0.005%, N≤0.003%, and the balance is Fe and unavoidable impurities;

[0007] Measured by volume percentage, the microstructure of the high-strength, high-toughness, oxidation-resistant hot-formed steel consists of 2-3.5% ferrite and 96.5-98% martensite.

[0008] The reasons for limiting the chemical composition of the high-strength, high-toughness, oxidation-resistant hot-formed steel of the present invention are as follows:

[0009] As a strengthening element in steel, C has a significant effect on the martensite content and tensile strength of the hot-formed steel plate. In order to ensure the martensite structure and sufficiently high tensile strength of the hot-formed steel, and to ensure good plasticity, toughness and weldability of the hot-formed steel, the C content is controlled to 0.20-0.30%.

[0010] Mn plays a role in solid solution strengthening and improving toughness in steel. However, when the Mn content is too high, it is easy to cause segregation of the ingot and affect the uniformity of the structure. The Mn content is controlled to 1.00-1.80%.

[0011] The addition of Si can play a role in solid solution strengthening, improve the stability of austenite, and promote the subsequent martensite transformation. At the same time, Si can form a dense oxide film during hot forming, inhibiting the continued growth of the oxide film on the surface of the steel plate, thereby improving the high-temperature oxidation resistance of the steel. However, too high Si content will lead to deterioration of weldability and toughness of the welding heat-affected zone. The Si content is controlled to 0.60-1.20%;

[0012] Cr can improve the hardenability of steel and promote martensitic transformation. At the same time, Cr can improve the high temperature oxidation resistance of steel. The Cr content is controlled to 2.00-2.5%.

[0013] The Al element can improve the oxidation resistance and hydrogen embrittlement resistance of hot-formed steel at the same time, and can also refine the grains. However, when the Al content is too high, non-metallic inclusions will be produced, causing adverse effects. Therefore, the Al content is controlled to 0.60-1.20%.

[0014] Nb and V are strong carbide-forming elements, which precipitate to form composite carbides during the preparation process. The Nb and V composite carbides can act as hydrogen traps, which can reduce the concentration of diffusible hydrogen, thereby reducing the hydrogen embrittlement sensitivity of hot-formed steel and improving the safety of automotive hot stamping parts. In addition, the Nb and V composite carbides dispersed in ferrite can improve the strength of ferrite and resist the strength reduction caused by the presence of ferrite. Taking all factors into consideration, the mass percentage of Nb is 0.05-0.20%, and the mass percentage of V is 0.05-0.20%. The above-mentioned element composition cooperates synergistically, combined with the mechanical metallurgical preparation method, to obtain a high-strength, high-toughness, and oxidation-resistant hot-formed steel composed of 2-3.5% ferrite and 96.5-98% martensite.

[0015] By introducing 2-3.5% fine ferrite and precipitating nano-phase carbides in it, the strength and toughness of the material are improved at the same time. In the process of ferrite precipitation, the excess carbon is discharged into the austenite, which improves the strength of the martensite produced during the forming process. However, the presence of too much ferrite will reduce the strength of hot-formed steel and have an adverse effect on safety, so the ferrite content is controlled to 2-3.5%.

[0016] Technical solution 2 of the present invention: The mechanical metallurgical preparation method of the above-mentioned high-strength, high-toughness, oxidation-resistant hot-formed steel comprises the following steps:

[0017] After melting molten steel according to the chemical composition, a slab is prepared by continuous casting; the slab is subjected to hot forming treatment to obtain the high-strength, high-toughness, and oxidation-resistant hot-formed steel;

[0018] The thermoforming process is performed in one of the following ways:

[0019] Method 1: hot rolling and cold rolling are performed on the slab in sequence to obtain a thin steel plate; the thin steel plate is kept warm at a two-phase temperature, and then press-quenched to obtain the high-strength, high-toughness, and oxidation-resistant hot-formed steel;

[0020] Method 2: rough rolling and finish rolling are sequentially performed on the slab to obtain a thin steel plate; then the thin steel plate is immediately press-quenched to obtain the high-strength, high-toughness, and oxidation-resistant hot-formed steel;

[0021] The start rolling temperature of the finishing rolling is A c3 -10℃~A c3 The final rolling temperature is A c1 ~A c3 .

[0022] In the first method, the thin steel plate obtained after hot rolling and cold rolling is kept at the temperature of the two-phase region, which is beneficial to the formation of fine proeutectoid ferrite in the structure;

[0023] In method 2, the rolling temperature is controlled to be A c3-10℃~A c3 The final rolling temperature is A c1 ~A c3 Finish rolling is beneficial to the formation of fine proeutectoid ferrite in the structure, and the total deformation of finish rolling within the above temperature range is large, which is beneficial to refine the ferrite and promote the precipitation of carbides.

[0024] Furthermore, the thickness of the slab is 150-200 mm, the casting speed during the continuous casting process is 1.4-1.5 m / min, and the superheat of the molten steel is 20-30°C.

[0025] Furthermore, the hot forming process also includes heating pretreatment and descaling steps for the slab before the hot forming process.

[0026] Furthermore, the temperature of the heating pretreatment is 1210-1215° C., and the time is 4-5 hours.

[0027] Furthermore, the descaling treatment adopts a high-pressure water descaling method, the slab temperature before descaling is 1200-1210° C., and the descaling water pressure is 15-20 MPa.

[0028] Furthermore, the starting rolling temperature of the hot rolling is 1200° C., the final rolling temperature is 950-960° C., and the total reduction ratio is 70-98%; the total reduction ratio of the cold rolling is 50-60%.

[0029] Furthermore, the two-phase region temperature is A c3 -30℃~A c3 The insulation time at the two-phase temperature is 1 to 5 minutes.

[0030] Furthermore, the starting rolling temperature of the rough rolling is 1200° C., the final rolling temperature is 920-930° C., and the total reduction ratio is 70-90%; the total reduction ratio of the finish rolling is 70-90%.

[0031] Furthermore, after the hot rolling and before the cold rolling, a coiling operation is also included.

[0032] Furthermore, the parameters of the press quenching forming include: a pressure of 500t and a holding time of 10s.

[0033] Furthermore, the coiling temperature is 640°C.

[0034] The present invention discloses the following technical effects:

[0035] The present invention provides a high-strength, high-toughness, oxidation-resistant hot-formed steel and a mechanical metallurgical preparation method thereof. Through the coordination of chemical composition and mechanical metallurgical preparation method, a hot-formed steel product with excellent oxidation resistance and excellent strength and toughness is obtained.

[0036] The chemical components used in the high-strength, high-toughness, oxidation-resistant hot-formed steel of the present invention are cheap and readily available, and the production cost is low.

[0037] The mechanical metallurgical preparation method of the invention has simple production process and high production efficiency.

[0038] The thermoforming temperature in the present invention is relatively low, which can save energy, reduce carbon dioxide emissions, and reduce costs. DETAILED DESCRIPTION

[0039] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0040] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0041] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0042] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0043] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0044] As a first aspect of the present invention, the present invention provides a high-strength, high-toughness, oxidation-resistant hot-formed steel. The chemical composition of the high-strength, high-toughness, oxidation-resistant hot-formed steel is as follows, by mass percentage: C: 0.20-0.30%, Mn: 1.00-1.80%, Cr: 2.00-2.50%, Si: 0.60-1.20%, Al: 0.60-1.20%, Nb: 0.05-0.20%, V: 0.05-0.20%, P≤0.01%, S≤0.005%, N≤0.003%, and the balance is Fe and unavoidable impurities;

[0045] Measured by volume percentage, the microstructure of the high-strength, high-toughness, oxidation-resistant hot-formed steel consists of 2-3.5% ferrite and 96.5-98% martensite.

[0046] As a second aspect of the present invention, the present invention provides a mechanical metallurgical preparation method of the above-mentioned high-strength, high-toughness, oxidation-resistant hot-formed steel, comprising the following steps:

[0047] After melting molten steel according to the chemical composition, a slab is prepared by continuous casting; the slab is subjected to hot forming treatment to obtain the high-strength, high-toughness, and oxidation-resistant hot-formed steel;

[0048] The thermoforming process is performed in one of the following ways:

[0049] Method 1: hot rolling and cold rolling are performed on the slab in sequence to obtain a thin steel plate; the thin steel plate is kept warm at a two-phase temperature, and then press-quenched to obtain the high-strength, high-toughness, and oxidation-resistant hot-formed steel;

[0050] Method 2: rough rolling and finish rolling are sequentially performed on the slab to obtain a thin steel plate; then the thin steel plate is immediately press-quenched to obtain the high-strength, high-toughness, and oxidation-resistant hot-formed steel;

[0051] The start rolling temperature of the finishing rolling is A c3 -10℃~A c3 The final rolling temperature is A c1 ~A c3 .

[0052] As a preferred embodiment of the present invention, the thickness of the slab is 150-200 mm, the casting speed during the continuous casting process is 1.4-1.5 m / min, and the superheat of the molten steel is 20-30°C.

[0053] As a preferred embodiment of the present invention, the hot forming process also includes heating pretreatment and descaling steps of the slab before the hot forming process.

[0054] As a preferred embodiment of the present invention, the temperature of the heating pretreatment is 1210-1215° C. and the time is 4-5 hours.

[0055] As a preferred embodiment of the present invention, the descaling treatment adopts a high-pressure water descaling method, the slab temperature before descaling is 1200-1210° C., and the descaling water pressure is 15-20 MPa.

[0056] As a preferred embodiment of the present invention, the hot rolling start temperature is 1200°C, the final rolling temperature is 950-960°C, and the total reduction ratio is 70-98%; the cold rolling total reduction ratio is 50-60%.

[0057] As a preferred embodiment of the present invention, the two-phase region temperature is A c3 -30℃~A c3 The insulation time at the two-phase temperature is 1 to 5 minutes.

[0058] As a preferred embodiment of the present invention, the starting rolling temperature of the rough rolling is 1200°C, the final rolling temperature is 920-930°C, and the total reduction ratio is 70-90%; the total reduction ratio of the finish rolling is 70-90%.

[0059] A c1 is the starting temperature of pearlite to austenite transformation during heating, A c3 It is the final temperature at which all the proeutectoid ferrite is transformed into austenite during heating, which can be obtained by testing with a dynamic phase change thermal expansion instrument.

[0060] As a preferred embodiment of the present invention, after the hot rolling and before the cold rolling, a coiling operation is also included.

[0061] As a preferred embodiment of the present invention, the parameters of the press quenching forming include: a pressure of 500t and a holding time of 10s.

[0062] As a preferred embodiment of the present invention, the coiling temperature is 640°C.

[0063] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0064] In the specific embodiment of the present invention, there is no limit on the number of hot rolling, cold rolling, rough rolling and finishing rolling, and multiple passes can be performed. As long as the required total reduction ratio can be achieved in the required start rolling temperature and final rolling temperature range, the specific number of rolling passes has no effect on the performance of hot-formed steel; as long as the required total reduction ratio can be achieved in cold rolling, the specific number of rolling passes has no effect on the performance of hot-formed steel.

[0065] Example 1

[0066] A high-strength, high-toughness, oxidation-resistant hot-formed steel, whose chemical composition, by mass percentage, is: C: 0.20%, Mn: 1.00%, Cr: 2.00%, Si: 1.20%, Al: 0.60%, Nb: 0.20%, V: 0.20%, P≤0.01%, S≤0.005%, N≤0.003%, and the balance is Fe and unavoidable impurities.

[0067] The mechanical metallurgical preparation method is as follows: molten steel is melted according to the set chemical composition, and the molten steel is used to prepare slabs through continuous casting equipment. The slab thickness is 200 mm, the billet drawing speed is 1.5 m / min, and the superheat of the molten steel during the continuous casting process is 30°C; the slab is heated in a heating furnace for pretreatment at a heating temperature of 1210°C and a holding time of 4 hours; the slab is taken out of the heating furnace and quickly descaled by high-pressure water descaling technology. The slab temperature before descaling is 1200°C. The descaling water pressure is 20MPa; the descaling slab is hot rolled, the starting rolling temperature is 1200℃, the final rolling temperature is 950℃, and the total reduction rate is 97.5% to obtain a 5mm thick steel plate; then the steel plate is cooled in a 640℃ furnace to the coiling temperature (640℃), and the steel plate is coiled to obtain a hot-rolled thin strip; the hot-rolled thin strip is cold rolled, and the total reduction rate is 60% to obtain a 2mm thick thin steel plate; the thin steel plate is placed in 840℃ (tested A c3 After being kept in a heating furnace at a temperature of 848°C for 5 minutes, the steel plate was immediately press-quenched, specifically, it was put into a press while hot and kept at a pressure of 500t for 10 seconds, then the steel plate was taken out and naturally cooled to room temperature to obtain a high-strength, high-toughness, and oxidation-resistant hot-formed steel plate formed part. According to GB / T 228.1-2021 and GB T4340.1-2009, the room temperature tensile properties and hardness tests of the formed plate were carried out to obtain its mechanical properties data; according to GB / T 13303-1991, the thickness of the oxide layer of the formed plate was statistically analyzed to obtain its oxidation resistance data; the organization was observed, and the ferrite content and carbide distribution were statistically analyzed, and the results are shown in Table 1.

[0068] Table 1

[0069]

[0070] Example 2

[0071] A high-strength, high-toughness, oxidation-resistant hot-formed steel, whose chemical composition, by mass percentage, is: C: 0.30%, Mn: 1.00%, Cr: 2.50%, Si: 0.60%, Al: 1.20%, Nb: 0.05%, V: 0.05%, P≤0.01%, S≤0.005%, N≤0.003%, and the balance is Fe and unavoidable impurities.

[0072] The mechanical metallurgical preparation method is as follows: molten steel is melted according to the set chemical composition, and the molten steel is used to prepare slabs through continuous casting equipment. The slab thickness is 200 mm, the billet drawing speed is 1.5 m / min, and the superheat of the molten steel during the continuous casting process is 30°C; the slab is heated in a heating furnace for pretreatment at a heating temperature of 1210°C and a holding time of 4 hours; the slab is taken out of the heating furnace and quickly descaled by high-pressure water descaling technology. The slab temperature before descaling is 1200°C. The descaling water pressure is 20MPa; the descaling slab is hot rolled, the starting rolling temperature is 1200℃, the final rolling temperature is 950℃, and the total reduction rate is 97.5% to obtain a 5mm thick steel plate; then the steel plate is cooled in a 640℃ furnace to the coiling temperature (640℃), and the steel plate is coiled to obtain a hot-rolled thin strip; the hot-rolled thin strip is cold rolled, and the total reduction rate is 60% to obtain a 2mm thick thin steel plate; the thin steel plate is placed in 820℃ (tested A c3 After being kept in a heating furnace at a temperature of 825°C for 5 minutes, the steel plate was immediately press-quenched, specifically, it was put into a press while hot and kept at a pressure of 500t for 10 seconds, then the steel plate was taken out and naturally cooled to room temperature to obtain a high-strength, high-toughness, and oxidation-resistant hot-formed steel plate formed part. According to "GB / T 228.1-2021" and "GB T4340.1-2009", the tensile properties and hardness of the formed plate were tested to obtain its mechanical properties data; according to "GB / T 13303-1991", the thickness of the oxide layer of the formed plate was statistically analyzed to obtain its oxidation resistance data; the organization was observed, and the ferrite content and carbide distribution were statistically analyzed, and the results are shown in Table 2.

[0073] Table 2

[0074]

[0075] Example 3

[0076] A high-strength, high-toughness, oxidation-resistant hot-formed steel, whose chemical composition, by mass percentage, is: C: 0.20%, Mn: 1.00%, Cr: 2.00%, Si: 1.20%, Al: 0.60%, Nb: 0.20%, V: 0.20%, P≤0.01%, S≤0.005%, N≤0.003%, and the balance is Fe and unavoidable impurities.

[0077] The mechanical metallurgical preparation method is as follows: molten steel is melted according to the set chemical composition, and the molten steel is used to prepare a slab through a continuous casting device, the slab thickness is 200 mm, the billet drawing speed is 1.5 m / min, and the superheat of the molten steel during the continuous casting process is 30°C; the slab is heated in a heating furnace for pretreatment, the heating temperature is 1210°C, and the insulation time is 4 hours; the slab is taken out of the heating furnace and quickly descaled by a high-pressure water descaling technology, the slab temperature before descaling is 1200°C, and the descaling water pressure is 20 MPa; the dephosphorized slab is rough rolled and finished rolled, the starting rolling temperature of the rough rolling is 1200°C, the final rolling temperature is 920°C, and the total reduction rate is 90%; the starting rolling temperature of the finishing rolling is 840°C, and the final rolling temperature is 820°C (after detection A c3 848℃, A c1 771℃), the total reduction rate is 90%, and a 2mm thick thin steel plate is obtained; after the finish rolling, press quenching is immediately carried out, specifically, the hot plate is placed in the press and maintained at a pressure of 500t for 10s, and then the steel plate is taken out and naturally cooled to room temperature to obtain a high-strength, high-toughness, and oxidation-resistant hot-formed steel plate formed part. According to "GB / T 228.1-2021" and "GB T4340.1-2009", the tensile properties and hardness of the formed plate are tested to obtain its mechanical properties data; according to "GB / T 13303-1991", the thickness of the oxide layer of the formed plate is statistically analyzed to obtain its antioxidant performance data; the organization is observed, and the ferrite content and carbide distribution are statistically analyzed, and the results are shown in Table 3.

[0078] Table 3

[0079]

[0080] Example 4

[0081] A high-strength, high-toughness, oxidation-resistant hot-formed steel, whose chemical composition, by mass percentage, is: C: 0.30%, Mn: 1.00%, Cr: 2.50%, Si: 0.60%, Al: 1.20%, Nb: 0.05%, V: 0.05%, P≤0.01%, S≤0.005%, N≤0.003%, and the balance is Fe and unavoidable impurities.

[0082] The mechanical metallurgical preparation method is as follows: molten steel is melted according to the set chemical composition, and the molten steel is used to prepare a slab through a continuous casting device, the slab thickness is 200 mm, the billet drawing speed is 1.5 m / min, and the superheat of the molten steel during the continuous casting process is 30°C; the slab is heated in a heating furnace for pretreatment, the heating temperature is 1210°C, and the insulation time is 4 hours; the slab is taken out of the heating furnace and quickly descaled by a high-pressure water descaling technology, the slab temperature before descaling is 1200°C, and the descaling water pressure is 20 MPa; the dephosphorized slab is subjected to rough rolling and finish rolling, the start rolling temperature of the rough rolling is 1200°C, the final rolling temperature is 920°C, and the total reduction rate is 90%; the start rolling temperature of the finish rolling is 820°C, and the final rolling temperature is 810°C (after detection A c3 825℃, A c1 770℃), the total reduction rate is 90%, and a 2mm thick thin steel plate is obtained; after the finish rolling, press quenching is immediately carried out, specifically, the hot plate is placed in the press and maintained at a pressure of 500t for 10s, and then the steel plate is taken out and naturally cooled to room temperature to obtain a high-strength, high-toughness, and oxidation-resistant hot-formed steel plate formed part. According to "GB / T 228.1-2021" and "GB T4340.1-2009", the tensile properties and hardness of the formed plate are tested to obtain its mechanical properties data; according to "GB / T 13303-1991", the thickness of the oxide layer of the formed plate is statistically analyzed to obtain its antioxidant performance data; the organization is observed, and the ferrite content and carbide distribution are statistically analyzed, and the results are shown in Table 4.

[0083] Table 4

[0084]

[0085] Comparative Example 1

[0086] The invention discloses an oxidation-resistant hot-forming steel, which has the following chemical compositions by mass percentage: C: 0.20%, Mn: 1.00%, Cr: 2.00%, Si: 1.20%, Al: 0.60%, Nb: 0.20%, V: 0.20%, P≤0.01%, S≤0.005%, N≤0.003%, and the balance is Fe and unavoidable impurities.

[0087] The mechanical metallurgical preparation method is as follows: molten steel is melted according to the set chemical composition, and the molten steel is used to prepare a slab through a continuous casting device. The slab thickness is 200 mm, the billet drawing speed is 1.5 m / min, and the superheat of the molten steel during the continuous casting process is 30°C; the slab is heated in a heating furnace for pretreatment, the heating temperature is 1210°C, and the insulation time is 4 hours; the slab is taken out of the heating furnace and quickly descaled by high-pressure water descaling technology, the slab temperature before descaling is 1200°C, and the descaling water pressure is 20 MPa; the descaled slab is hot rolled, and the rolling start temperature is 120 0℃, the final rolling temperature is 950℃, the total reduction rate is 97.5%, and a 5mm thick steel plate is obtained. The steel plate is then cooled in a 640℃ furnace to the coiling temperature (640℃) to obtain a hot-rolled thin strip; the hot-rolled thin strip is cold-rolled with a total reduction rate of 60% to obtain a 2mm thick thin steel plate; the thin steel plate is placed in a 930℃ heating furnace and kept warm for 5min, and then press-quenched immediately, specifically, it is placed in a press while hot and kept under a pressure of 500t for 10s, and then the steel plate is taken out and naturally cooled to room temperature to obtain an oxidation-resistant hot-formed steel plate formed part. According to "GB / T 228.1-2021" and "GBT4340.1-2009", the tensile properties and hardness of the formed plates were tested to obtain their mechanical properties data; according to "GB / T 13303-1991", the oxide layer thickness of the formed plates was tested to obtain their antioxidant performance data; the organization was observed, and the ferrite content and carbide distribution were statistically analyzed. The results are shown in Table 5.

[0088] Table 5

[0089]

[0090] Comparative Example 2

[0091] The invention discloses an oxidation-resistant hot-forming steel, wherein the chemical composition is, by mass percentage, C: 0.21%, Mn: 0.84%, Cr: 2.62%, Si: 0.42%, Al: 0.60%, Nb: 0.50%, V: 0.10%, P≤0.01%, S≤0.005%, N≤0.003%, and the balance is Fe and unavoidable impurities.

[0092] The mechanical metallurgical preparation method is as follows: melt molten steel according to the set chemical composition, and prepare slabs through continuous casting equipment. The slab thickness is 200mm, the billet drawing speed is 1.5m / min, and the superheat of the molten steel in the continuous casting process is 30℃; the slab is heated in a heating furnace for pretreatment, the heating temperature is 1210℃, and the insulation time is 4 hours; the slab is taken out of the heating furnace and quickly descaled by high-pressure water descaling technology. The temperature of the slab before descaling is 12 00℃, the descaling water pressure is 20MPa; the descaling slab is hot rolled, the starting rolling temperature is 1200℃, the final rolling temperature is 950℃, the total reduction rate is 97.5%, and a 5mm thick steel plate is obtained, and then the steel plate is cooled in a 640℃ furnace to the coiling temperature (640℃) to obtain a hot-rolled thin strip; the hot-rolled thin strip is cold rolled, the total reduction rate is 60%, and a 2mm thick thin steel plate is obtained; the thin steel plate is placed in a 930℃ (tested A c3 After being kept in a heating furnace at 838℃ for 5 minutes, the steel plate was immediately press-quenched, specifically, it was put into a press while hot and kept under a pressure of 500t for 10 seconds, then the steel plate was taken out and naturally cooled to room temperature to obtain an anti-oxidation hot-formed steel plate formed part. According to GB / T228.1-2021 and GB T4340.1-2009, the tensile properties and hardness of the formed plate were tested to obtain its mechanical properties data; according to GB / T 13303-1991, the thickness of the oxide layer of the formed plate was statistically analyzed to obtain its anti-oxidation performance data; the organization was observed, and the ferrite content and carbide distribution were statistically analyzed, and the results are shown in Table 6.

[0093] Table 6

[0094]

[0095] Comparative Example 3

[0096] The invention discloses an oxidation-resistant hot-forming steel, wherein the chemical composition is as follows, by mass percentage: C: 0.30%, Mn: 1.00%, Cr: 2.50%, Si: 0.60%, Al: 1.20%, Nb: 0.05%, V: 0.05%, P≤0.01%, S≤0.005%, N≤0.003%, and the balance is Fe and unavoidable impurities.

[0097] The mechanical metallurgical preparation method is as follows: molten steel is melted according to the set chemical composition, and the molten steel is used to prepare a slab through a continuous casting device. The slab thickness is 200 mm, the billet drawing speed is 1.5 m / min, and the superheat of the molten steel during the continuous casting process is 30°C; the slab is heated in a heating furnace for pretreatment, the heating temperature is 1210°C, and the insulation time is 4 hours; the slab is taken out of the heating furnace and quickly descaled by high-pressure water descaling technology, the slab temperature before descaling is 1200°C, and the descaling water pressure is 20 MPa; the descaled slab is hot rolled, the starting rolling temperature is 1200°C, and the final The rolling temperature is 950°C, the total reduction rate is 97.5%, and a 5mm thick steel plate is obtained; the steel plate is then cooled in a 640°C furnace to the coiling temperature (640°C), and the steel plate is coiled to obtain a hot-rolled thin strip; the hot-rolled thin strip is cold-rolled with a total reduction rate of 60% to obtain a 2mm thick thin steel plate; the thin steel plate is placed in a 930°C heating furnace and kept warm for 5 minutes, and then immediately press-quenched, specifically, placed in a press while hot and kept at a pressure of 500t for 10s, then the steel plate is taken out and naturally cooled to room temperature to obtain an oxidation-resistant hot-formed steel plate formed part. According to "GB / T228.1-2021" and "GB T4340.1-2009", the tensile properties and hardness tests of the formed plates were carried out to obtain their mechanical properties data; according to "GB / T 13303-1991", the thickness of the oxide layer of the formed plates was statistically analyzed to obtain its antioxidant performance data; the organization was observed, and the ferrite content and carbide distribution were statistically analyzed. The results are shown in Table 7.

[0098] Table 7

[0099]

[0100] Comparative Example 4

[0101] The invention discloses an oxidation-resistant hot-forming steel, which has the following chemical compositions by mass percentage: C: 0.20%, Mn: 1.00%, Cr: 2.00%, Si: 1.20%, Al: 0.60%, Nb: 0.20%, V: 0.20%, P≤0.01%, S≤0.005%, N≤0.003%, and the balance is Fe and unavoidable impurities.

[0102] The mechanical metallurgical preparation method is as follows: molten steel is melted according to the set chemical composition, and the molten steel is used to prepare a slab through a continuous casting device, the slab thickness is 200 mm, the billet drawing speed is 1.5 m / min, and the superheat of the molten steel during the continuous casting process is 30°C; the slab is heated in a heating furnace for pretreatment, the heating temperature is 1210°C, and the insulation time is 4 hours; the slab is taken out of the heating furnace and quickly descaled by a high-pressure water descaling technology, the slab temperature before descaling is 1200°C, and the descaling water pressure is 20 MPa; the dephosphorized slab is rough rolled and finished rolled, the starting rolling temperature of the rough rolling is 1200°C, the final rolling temperature is 950°C, and the total reduction rate is 90%; the starting rolling temperature of the finishing rolling is 920°C, and the final rolling temperature is 860°C (after detection A c3 848℃, A c1 771℃), the total reduction rate is 90%, and a 2mm thick thin steel plate is obtained; after the finish rolling, press quenching is immediately carried out, specifically, the hot plate is placed in the press and maintained at a pressure of 500t for 10s, and then the steel plate is taken out and naturally cooled to room temperature to obtain an anti-oxidation hot-formed steel plate formed part. According to "GB / T 228.1-2021" and "GB T4340.1-2009", the tensile properties and hardness of the formed plate are tested to obtain its mechanical properties data; according to "GB / T 13303-1991", the thickness of the oxide layer of the formed plate is statistically analyzed to obtain its anti-oxidation performance data; the organization is observed, and the ferrite content and carbide distribution are statistically analyzed, and the results are shown in Table 8.

[0103] Table 8

[0104]

[0105] Comparative Example 5

[0106] The invention discloses an oxidation-resistant hot-forming steel, wherein the chemical composition is as follows, by mass percentage: C: 0.30%, Mn: 1.00%, Cr: 2.50%, Si: 0.60%, Al: 1.20%, Nb: 0.05%, V: 0.05%, P≤0.01%, S≤0.005%, N≤0.003%, and the balance is Fe and unavoidable impurities.

[0107] The mechanical metallurgical preparation method is as follows: molten steel is melted according to the set chemical composition, and the molten steel is used to prepare a slab through a continuous casting device, the slab thickness is 200 mm, the billet drawing speed is 1.5 m / min, and the superheat of the molten steel during the continuous casting process is 30°C; the slab is heated in a heating furnace for pretreatment, the heating temperature is 1210°C, and the insulation time is 4 hours; the slab is taken out of the heating furnace and quickly descaled by a high-pressure water descaling technology, the slab temperature before descaling is 1200°C, and the descaling water pressure is 20 MPa; the dephosphorized slab is rough rolled and finished rolled, the starting rolling temperature of the rough rolling is 1200°C, the final rolling temperature is 950°C, and the total reduction rate is 90%; the starting rolling temperature of the finishing rolling is 920°C, and the final rolling temperature is 860°C (after detection A c3 825℃, A c1 770℃), the total reduction rate is 90%, and a 2mm thick thin steel plate is obtained; after the finish rolling, press quenching is immediately performed, specifically, it is placed in the press while hot and maintained at a pressure of 500t for 10s, and then the steel plate is taken out and naturally cooled to room temperature to obtain an anti-oxidation hot-formed steel plate formed part. According to "GB / T 228.1-2021" and "GB T4340.1-2009", the tensile properties and hardness of the formed plate are tested to obtain its mechanical properties data; according to "GB / T 13303-1991", the thickness of the oxide layer of the formed plate is statistically analyzed to obtain its anti-oxidation performance data; the organization is observed, and the ferrite content and carbide distribution are statistically analyzed, and the results are shown in Table 9.

[0108] Table 9

[0109]

[0110] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A high-strength, high-toughness, oxidation-resistant hot-formed steel, characterized in that: The chemical composition of the high-strength, high-toughness, oxidation-resistant hot-formed steel is as follows, by mass percentage: C: 0.20-0.30%, Mn: 1.00-1.80%, Cr: 2.00-2.50%, Si: 0.60-1.20%, Al: 0.60-1.20%, Nb: 0.05-0.20%, V: 0.05-0.20%, P≤0.01%, S≤0.005%, N≤0.003%, and the balance is Fe and unavoidable impurities; Measured by volume percentage, the microstructure of the high-strength, high-toughness, oxidation-resistant hot-formed steel consists of 2-3.5% ferrite and 96.5-98% martensite.

2. The mechanical metallurgical preparation method of high-strength, high-toughness, oxidation-resistant hot-formed steel according to claim 1, characterized in that: The following steps are involved: After melting molten steel according to the chemical composition, a slab is prepared by continuous casting; the slab is subjected to hot forming treatment to obtain the high-strength, high-toughness, and oxidation-resistant hot-formed steel; The thermoforming process is performed in one of the following ways: Method 1: hot rolling and cold rolling are performed on the slab in sequence to obtain a thin steel plate; the thin steel plate is kept warm at a two-phase temperature, and then press-quenched to obtain the high-strength, high-toughness, and oxidation-resistant hot-formed steel; Method 2: rough rolling and finish rolling are sequentially performed on the slab to obtain a thin steel plate; then the thin steel plate is immediately press-quenched to obtain the high-strength, high-toughness, and oxidation-resistant hot-formed steel; The start rolling temperature of the finishing rolling is A c3 -10℃~A c3 The final rolling temperature is A c1 ~A c3 .

3. The mechanical metallurgical preparation method according to claim 2, characterized in that: The thickness of the slab is 150-200 mm, the drawing speed during the continuous casting process is 1.4-1.5 m / min, and the superheat degree of the molten steel is 20-30°C.

4. The mechanical metallurgical preparation method according to claim 2, characterized in that: The hot forming process also includes heating pretreatment and descaling steps for the slab.

5. The mechanical metallurgical preparation method according to claim 4, characterized in that: The temperature of the heating pretreatment is 1210-1215° C., and the time is 4-5 hours; the descaling treatment adopts a high-pressure water descaling method, the slab temperature before descaling is 1200-1210° C., and the descaling water pressure is 15-20 MPa.

6. The mechanical metallurgical preparation method according to claim 2, characterized in that: The starting rolling temperature of the hot rolling is 1200° C., the final rolling temperature is 950-960° C., and the total reduction rate is 70-98%; the total reduction rate of the cold rolling is 50-60%.

7. The mechanical metallurgical preparation method according to claim 2, characterized in that: The two-phase region temperature is A c3 -30℃~A c3 The insulation time at the two-phase temperature is 1 to 5 minutes.

8. The mechanical metallurgical preparation method according to claim 2, characterized in that: The starting rolling temperature of the rough rolling is 1200° C., the final rolling temperature is 920-930° C., and the total reduction rate is 70-90%; the total reduction rate of the finish rolling is 70-90%.

9. The mechanical metallurgical preparation method according to claim 2, characterized in that: After the hot rolling and before the cold rolling, the process also includes a coiling operation.

10. The mechanical metallurgical preparation method according to claim 2, characterized in that: The press quenching forming parameters include: a pressure of 500t and a holding time of 10s.

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