Fe-Mn-Al-C-Zr high manganese steel and preparation method thereof

Abstract

The invention provides Fe-Mn-Al-C-Zr high manganese steel and a preparation method thereof, and belongs to the technical field of alloy materials. By controlling the content of the Al element, the density of the Al element is lower than that of the Fe element, so that the density of the high-manganese steel is reduced; by controlling the content of the C element, the stability and recovery power of an austenite phase in the high-manganese steel can be improved, internal stress is eliminated, the strength of the high-manganese steel is improved, meanwhile, an interstitial solution strengthening effect is achieved, and the obdurability and wear resistance of the high-manganese steel are improved; the austenite phase region can be expanded by controlling the Mn element content, and the austenite phase stability is improved; the Mn element also has a solid solution strengthening effect, so that the strength of the high-manganese steel can be improved; the content of the Zr element is controlled to ensure that the Zr element and the C element form a precipitated phase (such as ZrC), and the strength is further improved by separating out and strengthening refined grains.

Description

Technical Field

[0001] This invention relates to the field of alloy materials technology, specifically to a Fe-Mn-Al-C-Zr high manganese steel and its preparation method. Background Technology

[0002] High-manganese steel is an alloy steel with a manganese content of over 10%. It possesses high ultimate tensile strength and tensile strength, and is widely used in the automotive, aerospace, construction, and transportation industries. However, its strength is relatively low, with a yield strength of only 200 MPa at room temperature. Current research has found that the strength of high-manganese steel can be improved through alloying, optimized heat treatment processes, or microstructure control. For example, existing technology provides a high-strength high-manganese steel material and its preparation method with a composition of Mn 30.0%~37.0%, Al 0.7~5.0%, C 0.05~0.50%, and the remainder being Fe. By adding aluminum alloy and optimizing the heat treatment process, the strength of high-manganese steel has been improved, but its yield strength at room temperature is only 610~700 MPa, and its tensile strength is only 700~800 MPa, indicating room temperature potential for further improvement. Summary of the Invention

[0003] The purpose of this invention is to provide a Fe-Mn-Al-C-Zr high manganese steel and its preparation method. The Fe-Mn-Al-C-Zr high manganese steel provided by this invention has high strength.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a Fe-Mn-Al-C-Zr high manganese steel, the composition of which, by mass percentage, is: Zr 0.01~0.5%, C 0.6~1.1%, Al 6~8%, Mn 22~28%, and the balance Fe.

[0005] Preferably, the microstructure of the Fe-Mn-Al-C-Zr high-manganese steel comprises a recrystallized austenitic phase.

[0006] Preferably, the grain size of the recrystallized austenite phase is 0.2~5μm; the grain size of the non-recrystallized austenite is 10~30μm.

[0007] This invention also provides a method for preparing Fe-Mn-Al-C-Zr high-manganese steel as described in the above technical solution, comprising: After mixing the high-manganese steel raw materials, they are successively smelted, homogenized, rolled and annealed to obtain Fe-Mn-Al-C-Zr high-manganese steel.

[0008] Preferably, the homogenization treatment temperature is 1150~1200℃, and the homogenization treatment holding time is 90~180min; no cooling is performed after the homogenization treatment holding time.

[0009] Preferably, the rolling process includes hot rolling and cold rolling performed sequentially.

[0010] Preferably, the hot rolling temperature is 1100~1200℃; the hot rolling is a multi-pass hot rolling deformation, with each pass reducing the amount by no more than 15%, and the total deformation of the hot rolling is 33~42%.

[0011] Preferably, the cold rolling is a multi-pass rolling deformation, with each pass reducing the material by no more than 5%, and the total deformation of the cold rolling is 75-85%.

[0012] Preferably, the annealing temperature is 600~700℃, and the annealing time is 1~10min.

[0013] Preferably, the smelting is performed in a vacuum induction levitation furnace.

[0014] This invention provides a Fe-Mn-Al-C-Zr high manganese steel, wherein the components, by mass percentage, are: Zr 0.01~0.5%, C 0.7~1.1%, Al 6~8%, Mn 22~28%, and the balance Fe. This invention reduces the density of high-manganese steel by controlling the Al content, which is lower than that of Fe. Controlling the C content improves the stability and recovery kinetics of the austenite phase in the high-manganese steel, eliminates internal stress, and increases its strength. It also provides interstitial solid solution strengthening, enhancing the steel's toughness and wear resistance. Controlling the Mn content expands the austenite phase region and improves its stability. Mn also provides solid solution strengthening, further increasing the steel's strength. Controlling the Zr content utilizes its strong deoxidizing and desulfurizing capabilities, allowing it to form stable ZrO2, ZrS, and ZrN inclusions with non-metallic elements such as O, S, and N, thereby purifying the molten steel and inhibiting the formation of harmful inclusions. It also forms precipitates (such as ZrC) with C, refining the grains through precipitation strengthening and further enhancing strength. The results of the embodiments show that the lowest density of the Fe-Mn-Al-C-Zr high-manganese steel provided by this invention is 7.0 g / cm³. 3 The maximum tensile strength is 1391 MPa, the maximum yield strength is 1276 MPa, and the maximum elastic modulus is 154 GPa. Attached Figure Description

[0015] Figure 1 The electron backscattering pattern is shown for the Fe-Mn-Al-C-Zr high-manganese steel prepared in Example 1 of this invention. Figure 2 The electron backscattering pattern of Fe-Mn-Al-C-Zr high manganese steel prepared in Example 2 of this invention; Figure 3The electron backscattering pattern of Fe-Mn-Al-C-Zr high manganese steel prepared in Example 3 of this invention; Figure 4 The image shows the dimensions of the tensile specimens obtained by cutting the Fe-Mn-Al-C-Zr high manganese steel prepared in Examples 1-3 of this invention. Detailed Implementation

[0016] This invention provides a Fe-Mn-Al-C-Zr high manganese steel, the composition of which, by mass percentage, is: Zr 0.01~0.5%, C 0.7~1.1%, Al 6~8%, Mn 22~28%, and the balance Fe.

[0017] In this invention, the Fe-Mn-Al-C-Zr high-manganese steel comprises 0.01~0.5% Zr by mass percentage. In embodiments of this invention, the Zr content may specifically be 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, or 0.5% by mass percentage. This invention utilizes the extremely strong deoxidizing and desulfurizing capabilities of Zr by limiting its content. Zr can form stable ZrO2, ZrS, and ZrN inclusions with non-metallic elements such as O, S, and N, thereby purifying the molten steel and inhibiting the formation of harmful inclusions. It also forms precipitates (such as ZrC) with C, which strengthens and refines the grains, further improving strength.

[0018] In this invention, the Fe-Mn-Al-C-Zr high-manganese steel comprises 0.7-1.1% C by mass percentage. In embodiments of this invention, the C may specifically be 0.7%, 0.9%, or 1.1% by mass percentage. This invention ensures that C, by limiting the C content, can synergistically promote austenite formation with Mn, and that C dissolved in the austenite phase can enhance the strength and hardness of the steel.

[0019] In this invention, the Fe-Mn-Al-C-Zr high-manganese steel comprises 6-8% Al by mass percentage. In embodiments of this invention, the Al content may specifically be 6%, 7%, or 8% by mass percentage. This invention reduces the density of high-manganese steel by limiting the Al content to ensure that its density is lower than that of Fe; and by causing lattice expansion, increasing the volume of high-manganese steel, further reducing its density.

[0020] In this invention, the Fe-Mn-Al-C-Zr high-manganese steel comprises 22-28% Mn by mass percentage. In embodiments of this invention, the Mn content may specifically be 22%, 23%, 24%, 25%, or 28% by mass percentage. This invention ensures an expanded austenite phase region and improves austenite phase stability by limiting the Mn content; furthermore, Mn also has a solid solution strengthening effect, which can improve the strength of the high-manganese steel.

[0021] In this invention, the Fe-Mn-Al-C-Zr high-manganese steel, by weight percentage, also includes the balance Fe. This invention ensures that Fe fully forms a solid solution with manganese by limiting the Fe content, thereby enhancing the strength and hardness of the steel while maintaining good toughness.

[0022] In one embodiment of the present invention, the microstructure of the Fe-Mn-Al-C-Zr high-manganese steel may include recrystallized austenite phase and non-recrystallized austenite. By limiting the microstructure of the Fe-Mn-Al-C-Zr high-manganese steel to a recrystallized austenite phase, the present invention can improve the strength-ductility product of the material, suppress martensitic phase transformation, reduce the instability of retained austenite, and decrease temper brittleness and overheat sensitivity.

[0023] In one embodiment of the present invention, the grain size of the recrystallized austenite can be 0.2~5 μm. In specific embodiments of the present invention, the grain size of the recrystallized austenite can be 0.2 μm, 0.5 μm, 1 μm, 2 μm, or 3 μm, 5 μm. In another embodiment of the present invention, the grain size of the non-recrystallized austenite can be 10~30 μm. In specific embodiments of the present invention, the grain size of the non-recrystallized austenite can be 10 μm, 20 μm, or 30 μm. By limiting the grain size of the recrystallized austenite, the present invention can significantly improve the strength and toughness of the material.

[0024] In one embodiment of the present invention, the microstructure of the Fe-Mn-Al-C-Zr high-manganese steel, by volume percentage, may include 20-40% recrystallized austenite and 60-80% non-recrystallized austenite. The present invention can control the plasticity and strength of Fe-Mn-Al-C-Zr high-manganese steel by defining its microstructure.

[0025] In one embodiment of the present invention, the microstructure of the Fe-Mn-Al-C-Zr high-manganese steel, by volume percentage, may include 20-40% recrystallized austenite, and may also include 25-35% recrystallized austenite. In another embodiment of the present invention, the microstructure of the Fe-Mn-Al-C-Zr high-manganese steel, by volume percentage, may include 60-80% non-recrystallized austenite, and may also include 65-75%.

[0026] This invention reduces the density of high-manganese steel by controlling the Al content, which has a lower density than Fe. Controlling the C content improves the stability and recovery kinetics of the austenite phase in high-manganese steel, eliminates internal stress, and increases its strength. It also provides interstitial solid solution strengthening, enhancing the steel's toughness and wear resistance. Controlling the Mn content expands the austenite phase region and improves its stability. Mn also provides solid solution strengthening, further increasing the steel's strength. Controlling the Zr content refines the austenite grains, further enhancing the steel's strength.

[0027] As one embodiment of the present invention, the present invention also provides a method for preparing Fe-Mn-Al-C-Zr high-manganese steel as described in the above technical solution, comprising: After mixing the high-manganese steel raw materials, they are successively smelted, homogenized, rolled and annealed to obtain Fe-Mn-Al-C-Zr high-manganese steel.

[0028] In one embodiment of the present invention, the high-manganese steel raw material can be electrolytic iron, electrolytic manganese, high-purity aluminum, high-purity carbon, and zirconium blocks. By limiting the high-manganese steel raw materials to high purity electrolytic iron, electrolytic manganese, high-purity aluminum, high-purity carbon, and zirconium blocks, the present invention can fully exert the strengthening effect, improve the hardenability, tensile strength, and toughness of the high-manganese steel, increase the purity of the resulting high-manganese steel, reduce impurity interference, and lower processing difficulty.

[0029] In one embodiment of the present invention, the mass percentage of the high-manganese steel raw material is consistent with the composition of the high-manganese steel described in the above technical solution.

[0030] The present invention does not impose any special limitations on the mixing of the high manganese steel raw materials; any mixing method well known in the art can be used.

[0031] In one embodiment of the present invention, the high-manganese steel raw material can be pretreated before smelting. In one embodiment of the present invention, the pretreatment can be: mixing the high-manganese steel raw material and then sequentially subjecting it to ultrasonication and drying. In one embodiment of the present invention, the solvent for ultrasonication can be alcohol, and the ultrasonication time can be 10-15 minutes.

[0032] In one embodiment of the present invention, the melting can be performed in a vacuum induction levitation furnace. In another embodiment, the melting power can be 80-140 kW, or 90-120 kW; the melting time can be 3-5 minutes; and the vacuum degree of the melting can be 4 × 10⁻⁶. -2 Pa, the melting process can be repeated 5 to 7 times. This invention ensures that the metal raw materials are melted into a liquid by limiting the melting parameters, allowing for a more thorough and uniform mixing of the various metal elements. In one embodiment of this invention, the melting can be carried out in high-purity argon gas.

[0033] In one embodiment of the present invention, after the melting is completed, the melted product is poured into a mold and allowed to cool naturally to room temperature.

[0034] In one embodiment of the present invention, the heating rate of the homogenization treatment can be 10℃ / min. The temperature of the homogenization treatment can be 1150~1200℃; in embodiments of the present invention, the temperature of the homogenization treatment can specifically be 1150℃, 1160℃, 1170℃, 1180℃, 1190℃, or 1200℃. The holding time of the homogenization treatment can be 90~180min; in embodiments of the present invention, the holding time of the homogenization treatment can specifically be 90min, 120min, 140min, 160min, or 180min. The present invention ensures sufficient diffusion of metal atoms and eliminates dendritic segregation (such as intracrystalline solute enrichment) by limiting the parameters of the homogenization treatment, thus bringing the composition close to equilibrium.

[0035] In one embodiment of the present invention, the homogenization treatment is not cooled after heat preservation.

[0036] In one embodiment of the present invention, the rolling process can be hot rolling and cold rolling performed sequentially. The present invention first refines the grains and eliminates internal defects through high-temperature rolling, thereby improving the strength and toughness of the material; then, cold rolling further processes the material, improving the hardness and surface quality of the high-manganese steel through work hardening.

[0037] In one embodiment of the present invention, the hot rolling temperature can be 1100~1200℃. In embodiments of the present invention, the hot rolling temperature can specifically be 1100℃, 1150℃, or 1200℃. In one embodiment of the present invention, the hot rolling can be a multi-pass hot rolling deformation. In one embodiment of the present invention, the hot rolling passes can be 4~6. In one embodiment of the present invention, the reduction per pass can not exceed 15%, or can be 12~15%. In one embodiment of the present invention, except for the final hot rolling pass, each hot rolling pass is followed by heat preservation. In one embodiment of the present invention, the heat preservation temperature is the same as the homogenization treatment temperature described above, and will not be repeated here. In one embodiment of the present invention, the heat preservation time is 5~15 minutes. In one embodiment of the present invention, the total deformation of the hot rolling can be 33~42%. In embodiments of the present invention, the total deformation of the hot rolling can specifically be 33%, 34%, 35%, 36%, 37%, 39%, 40%, or 42%. This invention improves the strength and toughness of high-manganese steel by limiting the parameters of hot rolling to control the microstructure of high-manganese steel to recrystallized austenite phase and refine its grain size. Refining the grain size enhances the strength and toughness of the steel while reducing the brittle transition temperature.

[0038] In one embodiment of the present invention, the cooling method after hot rolling can be water quenching to room temperature.

[0039] In one embodiment of the present invention, the cold rolling can be a multi-pass rolling deformation process. In one embodiment of the present invention, the number of cold rolling passes can be 16 to 18. In one embodiment of the present invention, the reduction per pass can not exceed 5%, or can be 0.05 to 5%. In one embodiment of the present invention, the total deformation of the cold rolling can be 75% to 85%. In embodiments of the present invention, the total deformation of the cold rolling can specifically be 75%, 77%, 80%, 83%, or 85%. The present invention, by limiting the parameters of cold rolling, ensures uniform grain orientation and residual stress distribution in the resulting high-manganese steel, reduces plate defects (such as waviness and warping), and simultaneously improves the mechanical properties of high-manganese steel (such as yield strength and hardness).

[0040] In one embodiment of the present invention, the annealing temperature can be 600~700℃, and the annealing time can be 1~10min. In an embodiment of the present invention, the annealing temperature can specifically be 600℃, 650℃, or 700℃. In an embodiment of the present invention, the annealing time can specifically be 1min, 3min, 5min, 7min, or 10min. In one embodiment of the present invention, the cooling method for annealing can be water quenching. The present invention, by limiting the annealing parameters to ensure partial recrystallization of the grains, enables high manganese steel to have a dual-state microstructure, further improving the strength of high manganese steel. Compared with the traditional full annealing (solution treatment) + aging treatment, the mechanical properties are significantly improved, and the process is simpler.

[0041] This invention involves melting metal raw materials to ensure uniform mixing of various metal elements; then homogenization treatment to eliminate dendritic segregation; followed by high-temperature rolling to refine the grains, eliminate internal defects, and improve the strength and toughness of the material; then cold rolling for further processing to improve the hardness and surface quality of high-manganese steel through work hardening; and finally annealing to ensure partial recrystallization of the grains and refine the grains to improve mechanical properties.

[0042] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0043] Example 1 A Fe-Mn-Al-C-Zr high-manganese steel has the following composition by mass percentage: Zr 0.01%, C 0.9%, Al 7%, Mn 25%, and the balance Fe; the microstructure of the Fe-Mn-Al-C-Zr high-manganese steel consists of 31% recrystallized austenite with a size of 0.5~2μm by volume and 69% non-recrystallized austenite with a size of 10~18μm by volume; the density of the Fe-Mn-Al-C-Zr high-manganese steel is 7.0 g / cm³. 3 .

[0044] The preparation method of the above Fe-Mn-Al-C-Zr high-manganese steel is as follows: Electrolytic iron, electrolytic manganese, high-purity aluminum, high-purity carbon, and zirconium blocks, calculated according to the mass percentages of the above Fe-Mn-Al-C-Zr high-manganese steel composition, are mixed and ultrasonicated in alcohol for 10 minutes. After drying, the mixture is placed in a graphite crucible in a vacuum induction levitation furnace. A vacuum of 0.03 MPa is drawn, followed by the introduction of high-purity argon gas to a vacuum of 0.04 MPa. The mixture is then melted at 120 kW for 3 minutes, repeated 5 times, and then poured into a mold and allowed to cool naturally to room temperature. Finally, it is placed in a muffle furnace. The temperature was raised to 1200℃ at 10℃ / min for homogenization treatment. After holding at this temperature for 2 hours, the material was not cooled and was quickly removed and hot rolled at 1200℃ for the first pass. Then, it was placed in a muffle furnace and held at 1200℃ for 5 minutes without cooling. The material was then quickly removed and hot rolled at 1200℃ for the next pass. This process was repeated until the fifth pass of hot rolling. After that, the material was quickly water quenched and cooled to room temperature. Then, it was placed on a twin-roll mill for 16 passes of cold rolling. Finally, it was held in a muffle furnace at an annealing temperature of 700℃ for 3 minutes to obtain Fe-Mn-Al-C-Zr high manganese steel. The hot rolling process consists of 5 passes; the reduction per pass is 13%; the total deformation of the hot rolling process is 40%; the cold rolling process consists of 16 passes; the reduction per pass is 0.05%; the total deformation of the hot rolling process is 80%.

[0045] Example 2 The difference between this embodiment and Embodiment 1 is that 0.05% Zr is used instead of 0.01% Zr; the annealing temperature is 650℃; the rest is the same as in Embodiment 1, resulting in a density of 7.0 g / cm³. 3 The microstructure consists of 28% recrystallized austenite with a size of 0.5~3μm by volume and 72% non-recrystallized austenite with a size of 10~20μm in volume.

[0046] Example 3 The difference between this embodiment and Embodiment 1 is that 0.1% Zr is used instead of 0.01% Zr; the annealing temperature is 600℃; the rest is the same as in Embodiment 1, resulting in a density of 7.0 g / cm³. 3 The microstructure consists of 22% recrystallized austenite with a size of 1-3 μm by volume and 78% non-recrystallized austenite with a size of 10-15 μm in volume.

[0047] Backscattered electron imaging was performed on the Fe-Mn-Al-C-Zr high-manganese steel prepared in Examples 1-3 using an Oxford C-nano system in conjunction with a Gemini 300 scanning electron microscope. The resulting electron backscattered images of the Fe-Mn-Al-C-Zr high-manganese steel are shown below. Figures 1-3 As shown in the figure, the Fe-Mn-Al-C-Zr high-manganese steels prepared in Examples 1-3 are all composed of fine recrystallized austenite grains and coarse non-recrystallized austenite grains.

[0048] Comparative Example 1 Fe-30Mn-9Al-0.9C-0.45Mo was prepared according to the "Properties and Deformation Mechanism of Age-Tempered Fe-Mn-Al-C Steel" (Wang Ping, Guo Aimin, Hou Qingyu, Guo Yunxia, ​​Huang Zhenyi, Guang Jianfeng, 2021, 35(03): 184-192, Journal of Materials Research).

[0049] The tensile strength, yield strength, and elastic modulus of the Fe-Mn-Al-C-Zr high-manganese steels prepared in Examples 1-3 and the Fe-Mn-Al-C high-manganese steel prepared in Comparative Example 1 were tested using an Instron 5982 universal testing machine. Specifically, the Fe-Mn-Al-C-Zr high-manganese steels prepared in Examples 1-3 were respectively obtained by wire electrical discharge machining (EDM) to form the following... Figure 4 The tensile specimens shown were then tested, and the results are shown in Table 1.

[0050] Table 1. Tensile strength, yield strength, and elastic modulus of Fe-Mn-Al-C-Zr high manganese steels prepared in Examples 1-3

[0051] As shown in Table 1, the Fe-Mn-Al-C-Zr high manganese steels prepared in Examples 1-3 of the present invention have a tensile strength of 978-1391 MPa, a yield strength of 693-1276 MPa, and an elastic modulus of 193-154 GPa; the Fe-Mn-Al-C high manganese steels prepared in Comparative Example 1 have a tensile strength and a yield strength of 575 MPa and 863 MPa, respectively, which are much lower than those of the present invention.

[0052] The experimental results above show that the Fe-Mn-Al-C-Zr high manganese steel provided by this invention has high strength and low density.

[0053] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A Fe-Mn-Al-C-Zr high manganese steel, the composition by mass percentage being: Zr 0.01~0.5%, C 0.7~1.1%, Al 6~8%, Mn 22~28% and the balance Fe.

2. The high-manganese steel according to claim 1, characterized in that, The microstructure of the Fe-Mn-Al-C-Zr high-manganese steel includes recrystallized austenite and non-recrystallized austenite.

3. The high-manganese steel according to claim 2, characterized in that, The grain size of the recrystallized austenite is 0.2~5μm; the grain size of the non-recrystallized austenite is 10~30μm.

4. A method for preparing Fe-Mn-Al-C-Zr high-manganese steel according to any one of claims 1 to 3, comprising: After mixing the high-manganese steel raw materials, they are successively smelted, homogenized, rolled and annealed to obtain Fe-Mn-Al-C-Zr high-manganese steel.

5. The preparation method according to claim 4, characterized in that, The homogenization treatment temperature is 1150~1200℃, and the holding time of the homogenization treatment is 90~180min; no cooling is performed after the homogenization treatment.

6. The preparation method according to claim 5, characterized in that, The rolling process includes hot rolling and cold rolling performed sequentially.

7. The preparation method according to claim 6, characterized in that, The hot rolling temperature is 1100~1200℃; the hot rolling is a multi-pass hot rolling deformation, with each pass reducing the amount by no more than 15%, and the total deformation of the hot rolling is 33~42%.

8. The preparation method according to claim 6, characterized in that, The cold rolling is a multi-pass rolling deformation, with each pass reducing the amount by no more than 5%, and the total deformation of the cold rolling is 75-85%.

9. The preparation method according to claim 4, characterized in that, The annealing temperature is 600~700℃, and the annealing time is 1~10min.

10. The preparation method according to claim 4, characterized in that, The smelting process is carried out in a vacuum induction levitation furnace.

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