CN116657054A - Rare earth element-containing high-temperature oxidation resistant hot stamping steel and hot stamping forming process - Google Patents

Rare earth element-containing high-temperature oxidation resistant hot stamping steel and hot stamping forming process Download PDF

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CN116657054A
CN116657054A CN202310886845.4A CN202310886845A CN116657054A CN 116657054 A CN116657054 A CN 116657054A CN 202310886845 A CN202310886845 A CN 202310886845A CN 116657054 A CN116657054 A CN 116657054A
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hot stamping
steel
temperature oxidation
oxidation resistant
rare earth
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徐伟
李昭
王灵禺
胡军
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东北大学
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Abstract

A high-temperature oxidation resistant hot stamping steel containing rare earth elements and a hot stamping forming process belong to the field of hot stamping of steel materials. The hot stamping steel plate comprises the components of C, mn, si, cr, Y or Ce, nb, S, P, al, V, ti, cu, and the balance of Fe and unavoidable impurities. The hot stamping forming process comprises the following steps: heating the hot stamping forming steel plate, preserving heat, wherein the atmosphere in a heating furnace is an air environment, completely austenitizing the steel plate, transferring the steel plate into a die for stamping forming, maintaining the pressure of the die for cooling, and then placing the die into a heat treatment furnace for preserving heat to obtain hot stamping forming steel, wherein the obtained hot stamping forming steel structure is martensite and residual austenite with the volume percentage of 3-7%. The steel of the invention obtains a compact oxide layer below 0.5 mu m after hot stamping in the air, solves the problem of die damage caused by oxide scale falling, does not need equipment in protective atmosphere, improves the surface quality, and meets the mechanical property of hot stamping forming steel.

Description

Rare earth element-containing high-temperature oxidation resistant hot stamping steel and hot stamping forming process
Technical Field
The invention belongs to the field of hot stamping forming of steel materials, and particularly relates to high-temperature oxidation resistant hot stamping steel containing rare earth elements and a hot stamping forming process.
Background
With the increasing deterioration of the global environment, environmental protection, energy saving and safety are the main development directions of the automobile industry. The ultra-high strength steel plate is adopted to manufacture the automobile body, so that the weight of the automobile body can be effectively reduced, the oil consumption is reduced, the safety and the comfort level of the automobile are improved, and the automobile is also a necessary way for realizing the aim of double carbon. With the improvement of the strength of the advanced high-strength steel for the automobile, the tensile strength reaches more than 1500MPa, and the hot stamping forming process is adopted for direct processing forming, so that the hot stamping forming process is mainly used for producing parts with high automobile strength and high forming difficulty, and can avoid the problems of cracking, high rebound, poor part dimensional accuracy and shape stability and the like of a steel plate caused by high pressure required during cold forming. With further improvement of strength, the formability of the ultra-high strength steel plate is obviously reduced, and due to the characteristics of hot stamping forming steel production, the heating temperature is generally 900-950 ℃ and the temperature is kept for 3-10min, and protective atmosphere is generally introduced into a heating furnace to avoid serious oxidation. However, the control requirement on protective atmosphere is high in the actual processing process, and stable surface oxide skin state is not easy to obtain. In the hot stamping forming and heating process, iron and alloy elements in the matrix react with oxygen, carbon dioxide, water and the like in the air to form oxide scales, namely serious oxidation is generated. The oxide scale formed on the surface of the steel plate is easy to fall off in the forming process, abrasive particles are formed between the die and the steel plate to be worn, so that the accuracy and the appearance of the surface of the steel plate are improved, the surface of the die is damaged, and the service life of the die is prolonged.
The most mature hot stamping forming steel in the commercial stable production and technology is 1500MPa 22MnB5 grade and 1800MPa30MnB5 grade Mn-B series steel plates. Related researches show that the hot stamping forming steel with tensile strength of 1500MPa level replaces 800MPa level steel, and the weight of the automobile body can be reduced by more than 20 percent; if the tensile strength reaches 2000MPa, the weight can be further reduced by about 13%.
The problem of high-temperature oxidation resistance of hot stamping forming steel is solved, and at present, two main solutions exist: firstly, a plating technology is adopted, and secondly, a non-plating technology is adopted. At present, commercial hot stamping forming steel mainly uses Al-Si coating steel, the main function of the Al-Si coating is to prevent decarburization and oxidation of the surface of a steel plate in the austenitizing process, and the coating can isolate a matrix from the external environment, so that the commercial hot stamping forming steel has a certain anti-corrosion function, but the existence of the Al-Si coating also prevents diffusion of hydrogen to often cause cracking of the coating, hydrogen embrittlement is caused, and sticking of rollers occurs in the hot stamping forming process, so that the service life of a roller way is reduced, and the production cost is increased. The bare board is subjected to severe high-temperature oxidation in the hot stamping forming process, thick oxide skin which is easy to fall off is formed on the surface of the bare board, the subsequent welding quality and welding strength are seriously affected, shot blasting treatment is needed, but the shot blasting technology easily causes deformation of parts, and the corrosion resistance is poor. At present, the technology of no coating is mainly used for researching a forming method, strength, atmosphere and the like, most of the technology needs to be protected by introducing inert gas in the hot stamping forming process, stable surface state is not easy to obtain, and the cost is increased due to additional gas protection. The main problems of the prior art are represented by the following: the price of the coating is high, and the process is complex; the non-plating plate needs corresponding equipment for preparing inert gas, a closed heating furnace and the like, internal oxidation is inevitably generated, the surface quality cannot be ensured to be stable, the production efficiency is affected, and large-scale stable production cannot be realized.
Disclosure of Invention
Aiming at the problems existing in the prior art, the invention aims to provide the high-temperature oxidation resistant hot stamping steel containing rare earth elements and the hot stamping forming process, so as to solve the problems of high-temperature oxidation resistance, internal oxidation caused by unstable atmosphere of a heating furnace and difficult control of surface quality which are difficult to solve in the prior art. The high-temperature oxidation resistant hot stamping steel provided by the invention adopts a proper amount of Cr alloy, and forms a continuous Cr-rich layer in the hot stamping forming process, so that the effect of changing the structure of an oxide layer is achieved; meanwhile, a continuous Si-rich layer is formed in the oxide layer by utilizing the Si alloy, so that oxidation is further inhibited, and the thickness of the oxide layer is reduced. In order to rapidly form a continuous Cr-rich and Si-rich oxide layer, a proper amount of rare earth Y or Ce is added in the technology to accelerate the formation of the Cr-rich and Si-rich layers, so that the formation of a continuous Mn-rich band is further promoted, the inward diffusion of oxygen anions is slowed down, the high-temperature oxidation resistance is further enhanced, a stable oxidation structure in an air atmosphere is realized, the thickness of the oxide layer is lower than 0.5 mu m, and the stable surface quality is obtained.
In order to achieve the above object, the present invention provides the following technical solutions:
the high-temperature oxidation resistant hot stamping steel containing rare earth elements comprises the following chemical components in percentage by mass: c:0.15-0.35%, mn:0.8-3.2%, si:0.8-2.8%, cr:1.5-3.9%, Y:0.1-0.3% or Ce:0.1-0.5%, nb:0.01-0.05%, S: < 0.01%, P: < 0.015%, al:0.01-0.05%, V:0.01-0.05%, ti:0.01-0.03%, cu:0.05-0.15%, and the balance of Fe and other unavoidable impurities.
Further, the high-temperature oxidation resistant hot stamping steel ladle contains 0.15-0.35% of C. C is an austenite stability element, and the combination of C and a microalloying element can play a role of precipitation strengthening, and the welding performance is deteriorated due to the excessively high content of C, so that the mass percentage of C is 0.15-0.35%.
Further, the high-temperature oxidation resistant hot stamping steel ladle contains 0.8-3.2% of Mn. Mn can obviously increase hardenability, while high Mn content improves carbon equivalent, worsens welding performance, and reduces high-temperature oxidation resistance in the hot stamping forming process, so that the mass percentage of Mn is 0.8-3.2%.
Further, the high-temperature oxidation resistant hot stamping steel ladle contains 1.5-3.9% of Cr. Cr can obviously improve hardenability, refine and quench martensite lath, and Cr can well form a continuous Cr oxide layer to play a role of high-temperature oxidation resistance in the hot stamping forming process, and the mass percent of Cr is 1.5-3.9% from the performance of the hot stamping forming steel with the grade of more than 1500MPa.
Further, the high-temperature oxidation resistant hot stamping steel ladle contains 0.8-2.8% of Si. Si can play a role in solid solution strengthening, can effectively inhibit the formation of coarse carbides, and a proper amount of Si can form continuous amorphous SiO 2 The layer prevents further oxidation of the substrate, and the excessive content of Si causes brittleness, so that the mass percentage of Si is 0.8-2.8%.
Further, the high-temperature oxidation resistant hot stamping steel ladle contains 0.01-0.05% of Nb. Nb suppresses austenite recrystallization in the controlled rolling process, can obviously refine high-temperature austenite grains, realizes the function of hot rolling instead of cold rolling process, and worsens the surface quality of the continuous casting billet due to the excessively high Nb content, so that the mass percentage of Nb is 0.01-0.05%.
Further, the high-temperature oxidation resistant hot stamping steel ladle contains 0.01-0.05% of V. V can refine the quenched martensite lath, and the V and Nb jointly precipitate phase to play a role in precipitation strengthening, and the precipitate phase can improve the hydrogen embrittlement resistance, so that the mass percentage of V is 0.01-0.05%.
Further, the high-temperature oxidation resistant hot stamping steel ladle contains 0.01-0.03% of Ti. The Ti has the function of refining the prior austenite grains, and a trace amount of Ti fixes N atoms to form a precipitated phase to inhibit abnormal growth of the austenite grains in a welding coarse-grain heat affected zone, so that the mass percentage of the Ti is 0.01-0.03%.
Further, the high-temperature oxidation resistant hot stamping steel ladle contains 0.05-0.15% of Cu. Cu can improve corrosion resistance, and too high Cu causes brittleness, so that the mass percentage of Cu is 0.05-0.15%.
Further, the high-temperature oxidation resistant hot stamping steel ladle contains 0.01-0.05% of Al. Al is mainly used for deoxidizing and refining grains, and improves the structural property uniformity of steel to a certain extent, so that the mass percentage of Al is 0.01-0.05%.
Further, the high-temperature oxidation resistant hot stamping steel ladle contains 0.1-0.3% of Y or 0.1-0.5% of Ce. Both rare earth Y and Ce affect the structure of the oxide scale and its adhesiveness, and are one of the important elements of the present invention. Rare earths Y and Ce promote the formation of continuous Cr and Si oxide layers, improving the oxide scale adhesion, while at the same time inhibiting the in-diffusion of oxygen at the grain boundaries. The lower rare earth content does not significantly improve the oxidation resistance of the hot stamping forming steel in the air, and the higher rare earth content increases the cost, so that 0.1-0.3% of Y or 0.1-0.5% of Ce by mass percent is adopted.
Furthermore, the S content in the high-temperature oxidation resistant hot stamping steel is controlled to be less than 0.01%. S is generally a residual element in steel, which is detrimental to the properties of the steel.
Furthermore, the content of P in the high-temperature oxidation resistant hot stamping steel is controlled to be less than 0.015%. P is often a detrimental element in steel and segregation at grain boundaries increases the brittleness of the material significantly. The addition of the rare earth Y and Ce alloy can effectively avoid the segregation of P at the interface, so that the P exists in a solid solution mode.
Further, the high-temperature oxidation resistant hot stamping steel is heated for 5min at 930 ℃, the yield strength is more than or equal to 1200MPa, the tensile strength is more than or equal to 1500MPa, and the total elongation is more than or equal to 7.0% after being transferred to a die for quenching.
Furthermore, the thickness of the high-temperature oxidation resistant hot stamping steel oxide layer is less than or equal to 0.5 mu m.
Further, the preparation process of the high-temperature oxidation resistant hot stamping steel comprises the procedures of steelmaking, continuous casting, hot rolling, pickling, cold rolling and annealing.
The invention also provides a hot stamping forming process of the high-temperature oxidation resistant hot stamping steel, which comprises the following steps of: heating the hot stamped steel plate to 880-950 ℃ and keeping the temperature for 3-10min, wherein the atmosphere in a heating furnace is an air environment, so that the steel plate is completely austenitized; after the steel plate is completely austenitized, the steel plate is transferred into a die for stamping forming, the die closing temperature is 720-860 ℃, the die is subjected to pressure maintaining and cooling, the pressure is 3-25MPa, and the cooling speed is 5-50 ℃/s; then placing the steel into a heat treatment furnace at 170 ℃ for heat preservation to obtain the high-temperature oxidation resistant hot stamping steel, wherein the obtained high-temperature oxidation resistant hot stamping steel structure is martensite plus a small amount of residual austenite structure.
In summary, compared with the prior art, the invention has the following beneficial effects:
1. according to the invention, through the added rare earth Y or Ce, the thickness of the oxide skin of the steel plate is less than 0.5 mu m in the heating furnace in the hot stamping forming window under the air atmosphere, nitrogen production equipment and a closed heating furnace are not needed in the hot stamping forming process, equipment needed by hot stamping is simplified, the requirement of the hot stamping forming steel plate on the environment is reduced, an extremely thin oxide layer can still be obtained, the surface quality of the steel plate is more stable, and the steel plate is hardly influenced by the atmosphere.
2. On one hand, the addition of rare earth Y or Ce promotes the interface between the matrix and the oxide layer to form continuous Cr 2 O 3 And SiO 2 On the other hand reduce formation of Cr 2 O 3 Is a critical Cr content of (C). Continuous Cr 2 O 3 The formation of the layer can effectively prevent the outward diffusion of metal ions and the inward diffusion of oxygen ions. SiO (SiO) 2 The layer itself can hinder the inter-diffusion of ions and SiO 2 The contact area between the oxide layer and the substrate can be increased, so that the bonding strength between the oxide layer and the substrate is effectively increased. The oxide layer is compact and stable, is not easy to crack and fall off, and has better high-temperature oxidation resistance.
3. The addition of rare earth elements prevents the interdiffusion of oxygen ions and metal cations along the alloy grain boundary or lattice, thereby changing the growth mechanism of the oxide layer and slowing down the growth rate of the oxide scale. The clusters of rare earth solutes at the grain boundary can not effectively prevent outward diffusion of Mn, and the formation of Mn-rich bands in the oxide layer can effectively prevent inward diffusion of oxygen ions, slow down further oxidation of a matrix, and improve the high-temperature oxidation resistance of the hot stamping forming steel.
4. The invention aims at the conventional plating-free hot stamping forming steel in the prior art, although the oxidation resistance effect is better, the thickness of the oxide skin is controlled below 0.5 mu m, but nitrogen production equipment, a closed heating furnace and the like are needed in the hot stamping forming process, and enough protective gases such as nitrogen and air or nitrogen, methane and air are needed to be introduced to control the oxide skin below 0.5 mu m, so that the instability of the atmosphere is very easy to cause the deterioration of the surface quality of the hot stamping forming steel, therefore, the steel does not need nitrogen production equipment, the closed heating furnace and the like in the hot stamping forming process, the thickness of the oxide skin can still be ensured below 0.5 mu m under the air atmosphere, the surface quality is more stable, and the oxide skin is thinner, thereby being suitable for industrial production.
Drawings
FIG. 1 shows that the high-temperature oxidation resistant hot stamping steel added with Y or Ce element is in protective atmosphere N 2 And the cross-sectional oxide thicknesses of examples 1 and 2 and comparative examples 1 and 2 in air, wherein a is the cross-sectional oxide thickness of comparative example 1, b is the cross-sectional oxide thickness of comparative example 2, c is the cross-sectional oxide of example 1, and d is the cross-sectional oxide of example 2.
Fig. 2 is a graph showing the thickness of the cross-sectional oxide layers of examples 3 and 4 and comparative example 3 of the high temperature oxidation resistant hot stamped steel added with Y or Ce element according to the present invention in air, wherein a is a cross-sectional oxide layer thickness graph of comparative example 3, b is a cross-sectional oxide layer graph of example 3, and c is a cross-sectional oxide layer graph of example 4.
Fig. 3 is a graph showing the thickness of the cross-sectional oxide layers of examples 5 and 6 and comparative example 4 of the high temperature oxidation resistant hot stamped steel added with Y or Ce element according to the present invention in air, wherein a is a cross-sectional oxide layer thickness graph of comparative example 4, b is a cross-sectional oxide layer graph of example 5, and c is a cross-sectional oxide layer graph of example 6.
Fig. 4 is a graph showing the thickness of the cross-sectional oxide layers of examples 5 and 6 and comparative example 5 of the high temperature oxidation resistant hot stamped steel added with Y or Ce element according to the present invention in air, wherein a is a cross-sectional oxide layer thickness graph of comparative example 5, b is a cross-sectional oxide layer graph of example 5, and c is a cross-sectional oxide layer graph of example 6.
Fig. 5 is a graph showing the thickness of the cross-sectional oxide layers of examples 5 and 6 and comparative example 6 of the high temperature oxidation resistant hot stamped steel added with Y or Ce element according to the present invention in air, wherein a is a cross-sectional oxide layer thickness graph of comparative example 6, b is a cross-sectional oxide layer graph of example 5, and c is a cross-sectional oxide layer graph of example 6.
Fig. 6 is a graph showing the thickness of the cross-sectional oxide layers of examples 5 and 6 and comparative example 7 of the high temperature oxidation resistant hot stamped steel added with Y or Ce element according to the present invention in air, wherein a is a cross-sectional oxide layer thickness graph of comparative example 7, b is a cross-sectional oxide layer graph of example 5, and c is a cross-sectional oxide layer graph of example 6.
FIG. 7 is a graph showing the comparison of oxide scale thickness after hot stamping in air of a bare 22MnB5 plate with and without rare earth addition according to the present invention.
Fig. 8 is an element distribution diagram of the cross-sectional oxide layers of example 6 and comparative example 6 of the high temperature oxidation resistant hot stamped steel of the present invention added with rare earth Ce in air, wherein a is an element distribution diagram of comparative example 6 and b is an element distribution diagram of example 6.
Detailed Description
The following is a further detailed description of the technical solution of the present invention with reference to the accompanying drawings and specific embodiments. The hot stamping forming equipment is a hot stamping forming press; in the embodiment of the invention, an Ultra 55 field emission scanning electron microscope of Zeiss company is adopted for observing the cross-sectional morphology of the oxide skin.
Example 1
The high-temperature oxidation resistant hot stamping forming steel added with the Y element comprises the following alloy components in percentage by mass: c:0.2%, mn:1.3%, si:1.5%, cr:2.5%, Y:0.25%, nb:0.02%, S:0.005%, P:0.008%, al:0.03%, V:0.01%, ti:0.03%, cu:0.05%, the balance being Fe and other unavoidable impurities. Heating the hot stamping forming steel plate to 930 ℃, and introducing a certain amount of N into a heating furnace 2 And (3) protecting, preserving heat for 5min to ensure that the steel plate is completely austenitized, transferring to a stamping die for stamping forming, keeping the die clamping temperature at 800 ℃, keeping the pressure at 4MPa, cooling at a cooling speed of 40 ℃/s, and then placing the steel plate into a heat treatment furnace at 130 ℃ for preserving heat to obtain the high-temperature oxidation-resistant hot stamped steel.
Example 2
The Ce-added high-temperature oxidation resistant hot stamping forming steel comprises the following alloy components in percentage by mass: c:0.2%, mn:1.3%, si:1.5%, cr:2.5%, ce:0.14%, nb:0.02%, S:0.005%, P:0.008%, al:0.03%, V:0.01%, ti:0.03%, cu:0.05%, the balance being Fe and other unavoidable impurities. Heating the hot stamping forming steel plate to 930 ℃, and introducing a certain amount of N into a heating furnace 2 And (3) protecting, preserving heat for 5min to ensure that the steel plate is completely austenitized, transferring to a stamping die for stamping forming, keeping the die clamping temperature at 800 ℃, keeping the pressure at 4MPa, cooling at a cooling speed of 40 ℃/s, and then placing the steel plate into a heat treatment furnace at 170 ℃ for preserving heat to obtain the high-temperature oxidation-resistant hot stamped steel.
Example 3
The high-temperature oxidation resistant hot stamping forming steel added with the Y element comprises the following alloy components in percentage by mass: c:0.2%, mn:1.3%, si:1.5%, cr:2.5%, Y:0.25%, nb:0.02%, S:0.005%, P:0.008%, al:0.03%, V:0.01%, ti:0.03%, cu:0.05%, the balance being Fe and other unavoidable impurities. The hot stamping forming steel plate is heated to 930 ℃, protective atmosphere is not needed in a heating furnace, the steel plate is kept in air for 5min to be fully austenitized, then the steel plate is transferred to a stamping die for stamping forming, the stamping die closing temperature is 800 ℃,4MPa pressure maintaining cooling is carried out, the cooling speed is 40 ℃/s, and then the steel plate is put into a heat treatment furnace at 170 ℃ for heat preservation, so that the high-temperature oxidation resistant hot stamping steel is obtained.
Example 4
The Ce-added high-temperature oxidation resistant hot stamping forming steel comprises the following alloy components in percentage by mass: c:0.2%, mn:1.35%, si:1.5%, cr:2.5%, ce:0.14%, nb:0.02%, S:0.005%, P:0.008%, al:0.03%, V:0.01%, ti:0.03%, cu:0.05%, the balance being Fe and other unavoidable impurities. The hot stamping forming steel plate is heated to 930 ℃, protective atmosphere is not needed in a heating furnace, the steel plate is kept in air for 5min to be fully austenitized, then the steel plate is transferred to a stamping die for stamping forming, the stamping die closing temperature is 800 ℃,4MPa pressure maintaining cooling is carried out, the cooling speed is 40 ℃/s, and then the steel plate is put into a heat treatment furnace at 170 ℃ for heat preservation, so that the high-temperature oxidation resistant hot stamping steel is obtained.
Example 5
The high-temperature oxidation resistant hot stamping forming steel added with the Y element comprises the following alloy components in percentage by mass: c:0.2%, mn:1.35%, si:1.5%, cr:2.5%, Y:0.25%, nb:0.02%, S:0.005%, P:0.008%, al:0.03%, V:0.01%, ti:0.03%, cu:0.05%, the balance being Fe and other unavoidable impurities. The hot stamping forming steel plate is heated to 930 ℃, protective atmosphere is not needed in a heating furnace, the steel plate is kept in air for 6min to enable the steel plate to be completely austenitized, then the steel plate is transferred to a stamping die to be stamped and formed, the stamping die closing temperature is 800 ℃,4MPa pressure maintaining cooling is carried out, the cooling speed is 40 ℃/s, and then the steel plate is placed in a heat treatment furnace at 170 ℃ to be kept in temperature to obtain the high-temperature oxidation resistant hot stamping steel.
Example 6
The Ce-added high-temperature oxidation resistant hot stamping forming steel comprises the following alloy components in percentage by mass: c:0.2%, mn:1.35%, si:1.5%, cr:2.5%, ce:0.14%, nb:0.02%, S:0.005%, P:0.008%, al:0.03%, V:0.01%, ti:0.03%, cu:0.05%, the balance being Fe and other unavoidable impurities. The hot stamping forming steel plate is heated to 930 ℃, protective atmosphere is not needed in a heating furnace, the steel plate is kept in air for 6min to enable the steel plate to be completely austenitized, then the steel plate is transferred to a stamping die to be stamped and formed, the stamping die closing temperature is 800 ℃,4MPa pressure maintaining cooling is carried out, the cooling speed is 40 ℃/s, and then the steel plate is placed in a heat treatment furnace at 180 ℃ to be kept in temperature to obtain the high-temperature oxidation resistant hot stamping steel.
The steel sheet comprises the following processes before hot stamping forming: steelmaking, continuous casting, hot rolling, pickling, cold rolling and annealing.
Smelting and casting by using a 50kg vacuum induction furnace, wherein the content of impurity elements is controlled as strictly as possible in the smelting process, then, heating the steel ingot to 1300 ℃, preserving heat for 2 hours for homogenization, and the forging temperature is 1180 ℃ and the final forging temperature is 880 ℃; forging the ingot into a blank after multiple times of forging. Homogenizing at 1285 deg.C for 2 hr, hot rolling to obtain hot rolled plate, pickling to remove oxide skin, and cold rollingPerforming multi-pass rolling on a machine until the cold rolling thickness is 1.0-1.4mm, and performing annealing treatment at 750-780 ℃ by adopting N 2 -H 2 Atmosphere protection, ensuring uniform annealing of the matrix and eliminating the banded structure.
The hot stamping forming process of the steel plate comprises the following steps: heating the hot stamping formed steel plate to 880-950 ℃, and preserving heat for 3-10min to enable the steel plate to be completely austenitized; the whole heating process is in an air environment, after the steel plate is completely austenitized, the steel plate is transferred to a stamping die to be stamped and formed, the pressure maintaining and cooling are carried out, the cooling speed is controlled to be 5-50 ℃/s, then the steel plate is placed into a heat treatment furnace at 170 ℃ to be preserved, the hot stamping formed steel is obtained, and the obtained hot stamping formed steel structure is a martensite plus a small amount of residual austenite structure.
For better practice of the present invention, table 1 shows the alloy compositions of the examples of the steel sheet of the present invention and the comparative alloy compositions and the corresponding hot stamping forming processes, and the contents of S in each of the examples of the present invention and the comparative examples are < 0.01%, and P < 0.015%.
Table 1 chemical composition table (mass%) and hot stamping forming process (temperature-time min) of each example and comparative example
Comparative example 1 is a conventional plating-free hot stamping steel composition without addition of rare earth Y and Ce, hot stamping is performed under nitrogen and air atmosphere for 930-5 min; comparative example 2 is a composition of typical 22MnB5 on the market, hot stamping forming was performed under nitrogen and air atmosphere for 930-5 min; comparative example 3 is a composition of typical 22MnB5 on the market, hot stamping forming was performed in an air atmosphere of 930-5 min; comparative example 4 is a conventional plating-free hot stamping steel composition without adding rare earth Y and Ce, hot stamping is performed in an air atmosphere of 930-5 min; comparative example 5 is a composition of typical 22MnB5 on the market, hot stamping forming was performed in an air atmosphere of 950-6 min; comparative example 6 is a high conventional plating-free hot stamping steel composition without addition of rare earth Y and Ce, hot stamping is performed in an air atmosphere of 950-6 min; comparative example 7 is a conventional plating-free hot-stamping steel composition with a low Y content of 0.05%, hot-stamping is performed in an air atmosphere of 950-6 min.
As can be seen from FIG. 7, the thickness of the oxide layer of the rare earth added in the air atmosphere is significantly lower than that of 22MnB5 and conventional plating-free hot stamping steel, and the thickness of the oxide layer of the hot stamping steel added with rare earth Y or Ce is less than or equal to 0.5 μm in air. Referring to fig. 1, comparative examples 1 and 2, conventional plating-free hot-stamped steel and 22MnB5 hot-stamped steel had oxide layer thicknesses of 0.233 μm and 6.383 μm, respectively, under a protective atmosphere of nitrogen gas. The high-temperature oxidation resistant hot stamping steel added with 0.25 percent of Y or 0.14 percent of Ce is characterized in that N 2 And the scale thickness under air was 0.077 μm and 0.082 μm, respectively. Referring to FIGS. 2 and 3, comparative examples 3 and 4, the scale thicknesses of 930-5 min in air, 22MnB5 and conventional electroless hot stamping steel were 62.9 μm and 4.91 μm, respectively. The high-temperature oxidation resistant hot stamping steel added with 0.25% of Y or 0.14% of Ce of rare earth has oxide skin thicknesses of 0.127 μm and 0.119 μm respectively under air. Referring to fig. 4 and 5, comparative examples 5 and 6, the scale thicknesses of 22mnb5 and conventional plating-free hot-stamped steel in air were 84.7 μm and 23.05 μm, respectively. The high-temperature oxidation resistant hot stamping steel added with 0.25% of Y or 0.14% of Ce of rare earth has oxide skin thicknesses of 0.141 μm and 0.134 μm respectively under air. Referring to FIG. 6, comparative example 7, a small amount of 0.05% Y was added to air for 950-6 min to give a high temperature oxidation resistant hot stamped steel oxide layer thickness of 13.92. Mu.m. The high-temperature oxidation resistant hot stamping steel added with 0.25% of Y or 0.14% of Ce of rare earth has oxide skin thicknesses of 0.141 μm and 0.134 μm respectively under air.
As can be seen from FIG. 8, 0.14% Ce was addedThe high-temperature oxidation resistant hot stamping steel has obvious continuous enrichment zones of Cr and Mn in the surface oxide layer after hot stamping forming, and the continuous enrichment layer of Si cannot be identified due to the limitation of the resolution of SEM; the outer layer of the oxide layer on the surface of the conventional plating-free hot stamping forming steel is an enriched oxide of Fe, and the inner layer is an oxide of Cr and Si. In the invention, Y or Ce is added to promote the interface of the matrix oxide layer to form continuous Cr on one hand 2 O 3 And SiO 2 On the other hand reduce formation of Cr 2 O 3 Is a critical Cr content of (C). Cr (Cr) 2 O 3 The formation of the oxide layer can effectively prevent the outward diffusion of metal ions and the inward diffusion of oxygen ions. SiO (SiO) 2 The layer itself can hinder the inter-diffusion of ions and SiO 2 The contact area between the oxide layer and the substrate can be increased, so that the bonding strength between the oxide layer and the substrate is effectively increased. The oxide layer is compact and stable, is not easy to crack and fall off, and has better high-temperature oxidation resistance. Meanwhile, the addition of the rare earth element prevents the mutual diffusion of oxygen ions and metal cations along the alloy grain boundary, so that the growth mechanism of the oxide layer is changed, and the growth rate of the oxide layer is slowed down. Clusters of rare earth solutes at the grain boundary can not effectively prevent outward diffusion of Mn, and formation of Mn-rich bands in the oxide layer can effectively prevent inward diffusion of oxygen ions, slow down further oxidation of a matrix, and improve high-temperature oxidation resistance of hot stamping steel.
After the steel plates of each example and comparative example are processed according to the hot stamping forming process, the mechanical properties such as yield strength, tensile strength, elongation and the like are detected according to the national standard, and specific detection data are shown in table 2.
Sample of Yield strength (MPa) Tensile strength (MPa) Elongation (MPa)
Example 3 1245 1533 7.8
Example 4 1383 1622 8.0
Example 6 1368 1629 7.4
Comparative example 3 1055 1500 6.0
Comparative example 4 1372 1740 8.5
Comparative example 7 1303 1611 6.7
As can be seen from Table 2, the yield strength of the steel plate is more than or equal to 1200MPa, the tensile strength is more than or equal to 1500MPa, and the total elongation is more than or equal to 7.0% after the steel plate is heated at 930 ℃ for 5 min. By adding rare earth Y or Ce, the equiaxed crystal area is enlarged in the solidification process, the growth of recrystallized grains is inhibited, the refinement of original austenite and martensite laths is realized, and the strength and toughness of the steel are improved.
The above is only a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above examples. Any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art without departing from the technical concept of the present invention are intended to be included in the scope of the present invention.

Claims (7)

1. The high-temperature oxidation resistant hot stamping steel containing rare earth elements is characterized by comprising the following alloy components in percentage by mass: c:0.15-0.35%, mn:0.8-3.2%, si:0.8-2.8%, cr:1.5-3.9%, Y:0.1-0.3% or Ce:0.1-0.5%, nb:0.01-0.05%, S: < 0.01%, P: < 0.015%, al:0.01-0.05%, V:0.01-0.05%, ti:0.01-0.03%, cu:0.05-0.15%, and the balance of Fe and other unavoidable impurities.
2. The rare earth element-containing high-temperature oxidation resistant hot stamping steel as claimed in claim 1, wherein the element Y or Ce content in mass percent is: y:0.15-0.3% or Ce:0.1-0.23%.
3. A hot stamping process for a rare earth element-containing high temperature oxidation resistant hot stamped steel as claimed in claim 1 or 2, characterized by comprising the steps of:
step 1, heating a steel plate for hot stamping forming to 880-950 ℃, and keeping the temperature for 3-10min to ensure complete austenitization, wherein protective gas is not introduced into the furnace, namely, under an air environment, so that the components are ensured to be uniform;
step 2, after the steel plate is transferred, stamping and die assembly are carried out at the temperature of 720-860 ℃;
step 3, hot stamping forming treatment: and (3) carrying out hot stamping forming on the steel plate in a die with a cooling system, placing the steel plate in a pressure maintaining state, cooling, and then placing the steel plate in a heat treatment furnace for heat preservation to obtain hot stamping forming steel.
4. A hot stamping process for producing a rare earth element-containing high temperature oxidation resistant hot stamping steel as claimed in claim 3, wherein the pressure in the state of pressure retention in step 3 is 3-25MPa, the temperature in the heat treatment furnace is 130-180 ℃, and the cooling rate is 5-50 ℃/s.
5. A hot stamping process for a rare earth element-containing high temperature oxidation resistant hot stamping steel as claimed in claim 3, wherein the yield strength of the hot stamped steel is greater than or equal to 1200MPa and the tensile strength is greater than or equal to 1500MPa in an air atmosphere.
6. A hot stamping process for a rare earth element-containing high temperature oxidation resistant hot stamped steel as claimed in claim 3, wherein the total elongation of the hot stamped steel is greater than or equal to 7.0% in an air atmosphere.
7. A hot stamping process for a rare earth element-containing high temperature oxidation resistant hot stamping steel as claimed in claim 3, wherein the hot stamping structure is martensite and 3-7% by volume of retained austenite.
CN202310886845.4A 2023-07-19 2023-07-19 Rare earth element-containing high-temperature oxidation resistant hot stamping steel and hot stamping forming process Pending CN116657054A (en)

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