A Fe-Mn-Al-C series lightweight steel with high strength-plasticity and ablation resistance and a preparation method thereof

Abstract

The present invention discloses a Fe-Mn-Al-C series lightweight steel with high strength and plasticity and ablation resistance and a preparation method thereof, wherein the lightweight steel comprises 27-30wt% Mn, 8.0-10.0wt% Al, 0.9-1.2wt% C, 2.5-3.5wt% Ni, 0.5-0.8wt% Cr, and the rest is Fe. The present invention adds high mass percentages of Al and C elements to the lightweight steel, so that the alloy produces a nano-scale kappa carbide by spinodal decomposition during aging treatment, which maintains a high coherence relationship with austenite, improves the strength and plasticity of the alloy, and then by adding Ni and Cr elements, Ni and Fe are infinitely solid-dissolved, and Ni element can expand the austenite phase region, and is an element that forms and stabilizes austenite, and Cr and Fe can also form a continuous solid solution, reducing the austenite phase region, thereby further improving the high strength and plasticity of the material, such as the ablation resistance.

Description

Technical Field

[0001] The invention relates to the technical field of lightweight steel, and in particular to a Fe-Mn-Al-C lightweight steel with high strength-plasticity and ablation resistance and a preparation method thereof. Background Art

[0002] As the most widely used alloy material, steel occupies an important position in all walks of life. However, its weight has become a bottleneck for its further widespread application in industry and life. With the rapid development of lighter titanium and aluminum alloys, it has brought huge challenges to the steel industry, so steel lightweighting has received great attention.

[0003] In recent years, many researchers have conducted in-depth research on Fe-Mn-Al-C lightweight steel and successfully applied it in many industries, such as automobiles, marine engineering, metallurgy, chemical industry, light industry, etc., among which the automotive industry is the most prominent. Compared with traditional steel materials, Fe-Mn-Al-C lightweight steel has a lower density, but its strength and plasticity need to be further improved. In order to meet many special high-temperature application scenarios, the ablation resistance of Fe-Mn-Al-C lightweight steel also needs to be improved. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art, one of the objects of the present invention is to provide a Fe-Mn-Al-C lightweight steel with high strength-ductility and ablation resistance to solve the above-mentioned traditional technical problems.

[0005] The second object of the present invention is to provide a method for preparing the above-mentioned Fe-Mn-Al-C lightweight steel with high strength-ductility and ablation resistance.

[0006] One of the purposes of the present invention is achieved by the following technical solution:

[0007] A Fe-Mn-Al-C lightweight steel with high strength-ductility and ablation resistance, comprising the following components calculated by mass percentage:

[0008] Mn 27-30wt%; Al 8.0-10.0wt%; C 0.9-1.2wt%; Ni 2.5-3.5wt%; Cr0.5-0.8wt%, and the rest is Fe.

[0009] That is, the present invention can reduce the density of Fe-Mn-Al-C lightweight steel by adding Al element. This is because the density of Al atoms is much lower than that of Fe atoms. Replacing Fe atoms with a part of Al atoms can reduce the density of steel. In addition, the addition of Al element causes lattice expansion, which increases the volume of lightweight steel and further reduces the density. The addition of C element can improve the stability of austenite in steel and the recovery power of austenite, expand the austenite phase area, and have an interstitial solid solution strengthening effect, thereby improving the strength and toughness of Fe-Mn-Al-C lightweight steel. It can also be dissolved in austenite to improve the wear resistance of steel. The addition of Mn element can expand the austenite phase area, increase the stability of austenite, and can stably exist at room temperature. In addition, Mn atoms have a solid solution strengthening effect. In the present invention, the contribution of each element to the density of lightweight steel is, by mass percentage, for every 1% of Al added, the density of steel decreases by 0.101g / cm 3 , can reduce weight by 1.3%; for every 1% addition of C, the density of steel decreases by 0.41g / cm 3 , can reduce weight by 5.2%; for every 1% addition of Mn, the density of steel decreases by 0.0085g / cm 3 , which can reduce weight by 0.1%. The addition of Ni is due to the fact that Ni and Fe are infinitely solid-soluble, and Ni can expand the austenite phase area. It is an element that forms and stabilizes austenite. Therefore, adding the ablation-resistant element Ni to Fe-Mn-Al-C low-density steel can further improve its ablation resistance and mechanical properties. The addition of Cr can improve the strength and hardness of the alloy, significantly increase the tough-brittle transition temperature of steel, and Cr and Fe can also form a continuous solid solution to reduce the austenite phase area.

[0010] Furthermore, the high-strength-ductility and ablation-resistant Fe-Mn-Al-C lightweight steel comprises the following components calculated by mass percentage:

[0011] Mn 27.5-30wt%; Al 8.5-9.5wt%; C 0.95-1.2wt%; Ni 3-3.5wt%; Cr0.6-0.8wt%, and the rest is Fe.

[0012] Furthermore, the high-strength-ductility and ablation-resistant Fe-Mn-Al-C lightweight steel comprises the following components calculated by mass percentage:

[0013] Mn 28-29.5wt%; Al 9-9.5wt%; C 0.95-1.1wt%; Ni 3-3.3wt%; Cr 0.7-0.8wt%, and the rest is Fe.

[0014] Furthermore, the high-strength-plasticity and ablation-resistant Fe-Mn-Al-C lightweight steel also includes the following components calculated in percentage by mass:

[0015] O≤0.019wt%; P≤0.010wt%; S≤0.0047wt%; Si≤0.088wt%; N≤0.0018wt%.

[0016] Furthermore, the performance of the high strength-ductility and ablation-resistant Fe-Mn-Al-C lightweight steel is as follows: the density is 6.78 g / cm 3 The tensile strength can reach 1185MPa, the yield strength can reach 880MPa, the elongation after fracture is 35.8%, the cross-sectional shrinkage rate is 40.3%, and the material strength-plasticity product reaches 41GPa%.

[0017] The second object of the present invention is achieved by adopting the following technical solution:

[0018] A method for preparing a Fe-Mn-Al-C lightweight steel with high strength-plasticity and ablation resistance, comprising the following preparation steps:

[0019] (1) Chemical materials: 50% C particles, industrial pure iron, Cr and Ni that have been dried are added into the furnace. After the furnace is evacuated to make the pressure inside the furnace within 1000-1200 Pa, electricity is turned on to melt the materials, and 2kgAl is added;

[0020] (2) Slag reduction: adding another 50% of C and the remaining Al material;

[0021] (3) Refining: After the charge is fully melted, the temperature of the molten steel is rapidly raised to 1500°C and kept at this temperature for 30 minutes;

[0022] (4) Mn alloying: After refining, introduce Ar gas to 50,000-60,000 Pa, add Mn blocks, and add all the metal Mn in eight batches, with each batch adding 20% ​​of the total amount;

[0023] (5) Second refining: After Mn is fully melted, the molten steel temperature is maintained at 1500°C for 30 min;

[0024] (6) Sampling: Take samples for composition analysis, and reduce the power and temperature to below the melting point to solidify the molten steel until the composition meets the requirements;

[0025] (7) Casting: Ar gas is introduced to increase the vacuum degree to 75000Pa, the temperature of molten steel is increased to 1560℃, and the raw material ingot with a diameter of 70mm is cast under electric current; during the casting process, a prefabricated tundish with both slag blocking and filtering functions is used to filter the slag; the slag is demoulded after cooling in the steel mold.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention adds a high mass percentage of Al and C elements to the lightweight steel, so that the alloy generates a nano-scale kappa carbide through spinodal decomposition during the aging treatment process, which maintains a high coherence relationship with austenite and improves the strength and plasticity of the alloy. Then, by adding Ni and Cr elements, Ni and Fe are infinitely solid-dissolved, and Ni element can expand the austenite phase region and is an element for forming and stabilizing austenite. Cr and Fe can also form a continuous solid solution and reduce the austenite phase region, thereby further improving the material's high strength and plasticity, ablation resistance and other properties.

[0028] 2. The density of the Fe-Mn-Al-C lightweight steel provided by the present invention is 6.78 g / cm 3 After subsequent processing, the tensile strength can reach 1185MPa, the yield strength can reach 880MPa, the elongation after fracture is 35.8%, the cross-sectional shrinkage rate is 40.3%, and the material strength-plasticity product reaches 41GPa%.

[0029] 3. The Fe-Mn-Al-C lightweight steel provided by the present invention has excellent ablation resistance. No corrosion pits or peeling are found after ablation under a high-temperature flame of 1200°C for more than 5 minutes, and the weight loss rate is only 0.6%. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form a new embodiment.

[0031] Example 1

[0032] An alloy bar comprises the following components calculated by mass percentage:

[0033] Mn: 28.28wt%; Al: 9.39wt%; C: 1.00wt%, Ni: 3.28wt%; Cr: 0.54wt%, and the rest is Fe.

[0034] The preparation steps are as follows:

[0035] (1) Chemical materials: 50% C particles, industrial pure iron, Cr and Ni that have been dried are added into the furnace. The furnace is evacuated to make the pressure inside the furnace reach within 1000-1200Pa, then electricity is turned on to melt the materials, and 2kgAl is added.

[0036] (2) Slag: Add another 50% of C and the remaining Al material

[0037] (3) Refining: After the charge is fully melted, the temperature of the molten steel is rapidly raised to 1500°C and kept at this temperature for 30 minutes.

[0038] (4) Mn alloying: After refining, Ar gas is introduced to 50,000-60,000 Pa, and Mn blocks are added. All metal Mn is added in eight batches, and the amount added in each batch is 20% of the total amount added.

[0039] (5) Second refining: After Mn is fully melted, the temperature of the molten steel is maintained at 1500°C for 30 min.

[0040] (6) Sampling: Take samples for analysis of composition, and reduce power and temperature to below the melting point to solidify the molten steel into a film.

[0041] (7) Casting: Ar gas is introduced to increase the vacuum degree to 75000Pa, the temperature of molten steel is increased to melt, the temperature of molten steel is adjusted to 1560℃, and raw material ingots with a diameter of 70mm are cast under power. During the casting process, a prefabricated tundish with both slag blocking and filtering functions is used to filter the slag. After cooling in the steel mold, the mold is removed.

[0042] Example 2

[0043] An alloy bar comprises the following components calculated by mass percentage:

[0044] Mn: 29.5wt%; Al: 9.0wt%; C: 9.5wt%, Ni: 3.28wt%; Cr: 0.54wt%, and the rest is Fe.

[0045] The preparation steps are the same as those in Example 1.

[0046] Example 3

[0047] An alloy bar comprises the following components calculated by mass percentage:

[0048] Mn: 28.28wt%; Al: 9.39wt%; C: 1.00wt%, Ni: 3.28wt%; Cr: 0.54wt%, O: 0.019wt%; P: 0.010wt%; S: 0.0047wt%; Si: 0.088wt%; N: 0.0018wt%; the rest is Fe.

[0049] The preparation steps are as follows:

[0050] (1) Chemical materials: 50% C particles, industrial pure iron, Cr and Ni that have been dried are added into the furnace. The furnace is evacuated to make the pressure inside the furnace reach within 1000-1200Pa, then electricity is turned on to melt the materials, and 2kgAl is added.

[0051] (2) Slag: Add another 50% of C and the remaining Al material

[0052] (3) Refining: After the charge is fully melted, the temperature of the molten steel is rapidly raised to 1500°C and kept at this temperature for 30 minutes.

[0053] (4) Mn alloying: After refining, Ar gas is introduced to 50,000-60,000 Pa, and Mn blocks are added. All metal Mn is added in eight batches, and the amount added in each batch is 20% of the total amount added.

[0054] (5) Second refining: After Mn is fully melted, the remaining elements are added and the steel liquid temperature is maintained at 1500°C for 30 minutes.

[0055] (6) Sampling: Take samples to analyze the composition, and reduce the power and temperature to below the melting point to solidify the molten steel into a film.

[0056] (7) Casting: Ar gas is introduced to increase the vacuum degree to 75000Pa, the temperature of molten steel is increased to melt, the temperature of molten steel is adjusted to 1560℃, and raw material ingots with a diameter of 70mm are cast under power. During the casting process, a prefabricated tundish with both slag blocking and filtering functions is used to filter the slag. After cooling in the steel mold, the mold is removed.

[0057] Comparative Example 1

[0058] An alloy bar comprises the following components calculated by mass percentage:

[0059] Mn: 28.28wt%; Al: 9.39wt%; C: 1.00wt%, and the rest is Fe.

[0060] The preparation steps are as follows:

[0061] (1) Chemical materials: 50% C particles and industrial pure iron that have been dried are added into the furnace. The furnace is evacuated to make the pressure inside the furnace reach within 1000-1200Pa, then electricity is turned on to melt the materials, and 2kgAl is added.

[0062] (2) Slag: Add another 50% of C and the remaining Al material

[0063] (3) Refining: After the charge is fully melted, the temperature of the molten steel is rapidly raised to 1500°C and kept at this temperature for 30 minutes.

[0064] (4) Mn alloying: After refining, Ar gas is introduced to 50,000-60,000 Pa, and Mn blocks are added. All metal Mn is added in eight batches, and the amount added in each batch is 20% of the total amount added.

[0065] (5) Second refining: After Mn is fully melted, the temperature of the molten steel is maintained at 1500°C for 30 min.

[0066] (6) Sampling: Take samples to analyze the composition, and reduce the power and temperature to below the melting point to solidify the molten steel into a film.

[0067] (7) Casting: Ar gas is introduced to increase the vacuum degree to 75000Pa, the temperature of molten steel is increased to melt, the temperature of molten steel is adjusted to 1560℃, and raw material ingots with a diameter of 70mm are cast under power. During the casting process, a prefabricated tundish with both slag blocking and filtering functions is used to filter the slag. After cooling in the steel mold, the mold is removed.

[0068] Performance Testing

[0069] The performance of the rods of Example 1 and Comparative Example 1 was tested, and the test results are shown in Table 1 below.

[0070] Table 1

[0071] Sample tensile strength Yield Strength Elongation after fracture Sectional shrinkage Strong plastic product Comparative Example 1 1043Mpa 805Mpa 30.4％ 36.7％ 37GPa% Example 1 1185Mpa 880Mpa 35.8％ 40.3％ 41GPa%

[0072] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A Fe-Mn-Al-C lightweight steel with high strength-ductility and ablation resistance, characterized in that: The following components are included in percentage by mass: Mn: 28.28wt%; Al: 9.39wt%; C: 1.00wt%, Ni: 3.28wt%; Cr: 0.54wt%, the rest is Fe; The preparation steps are as follows: (1) Chemical materials: 50% C particles, industrial pure iron, Cr and Ni that have been dried are added into the furnace. The furnace is evacuated to make the pressure inside the furnace reach within 1000-1200Pa, then electricity is turned on to melt the materials, and 2kgAl is added; (2) Slag reduction: adding another 50% of C and the remaining Al material; (3) Refining: After the charge is fully melted, the temperature of the molten steel is rapidly raised to 1500°C and kept at this temperature for 30 minutes; (4) Mn alloying: After refining, introduce Ar gas to 50,000-60,000 Pa, add Mn blocks, and add all the metal Mn in eight batches, with each batch adding 20% ​​of the total amount; (5) Second refining: After Mn is fully melted, the molten steel temperature is maintained at 1500°C for 30 min; (6) Sampling: Take samples for composition analysis, and reduce the power and temperature to below the melting point to solidify the molten steel until the composition meets the requirements; (7) Casting: Ar gas is introduced to increase the vacuum degree to 75000Pa, the temperature of molten steel is increased to 1560°C, and the raw material ingot with a diameter of 70mm is cast under electric current; during the casting process, a prefabricated tundish with both slag blocking and filtering functions is used to filter the slag; the slag is demoulded after cooling in the steel mold; The density of the Fe-Mn-Al-C lightweight steel is 6.78 g / cm 3 The tensile strength can reach 1185MPa, the yield strength can reach 880MPa, the elongation after fracture is 35.8%, the cross-sectional shrinkage rate is 40.3%, and the material strength-plasticity product reaches 41GPa%.

2. The high-strength-ductility and ablation-resistant Fe-Mn-Al-C lightweight steel according to claim 1, characterized in that: The high-strength-ductility and ablation-resistant Fe-Mn-Al-C lightweight steel also includes the following components calculated by mass percentage: O≤0.019wt%; P≤0.010wt%; S≤0.0047wt%; Si≤0.088wt%; N≤0.0018wt%.

3. A method for preparing the Fe-Mn-Al-C lightweight steel with high strength-ductility and ablation resistance as claimed in any one of claims 1 or 2, characterized in that: The method comprises the following preparation steps: (1) Chemical materials: 50% C particles, industrial pure iron, Cr and Ni that have been dried are added into the furnace. After the furnace is evacuated to make the pressure inside the furnace within 1000-1200 Pa, electricity is turned on to melt the materials, and 2kgAl is added; (2) Slag reduction: adding another 50% of C and the remaining Al material; (3) Refining: After the charge is fully melted, the temperature of the molten steel is rapidly raised to 1500°C and kept at this temperature for 30 minutes; (4) Mn alloying: After refining, introduce Ar gas to 50,000-60,000 Pa, add Mn blocks, and add all the metal Mn in eight batches, with each batch adding 20% ​​of the total amount; (5) Second refining: After Mn is fully melted, the molten steel temperature is maintained at 1500°C for 30 min; (6) Sampling: Take samples for composition analysis, and reduce the power and temperature to below the melting point to solidify the molten steel until the composition meets the requirements; (7) Casting: Ar gas is introduced to increase the vacuum degree to 75000Pa, the temperature of molten steel is increased to 1560℃, and the raw material ingot with a diameter of 70mm is cast under electric current; during the casting process, a prefabricated tundish with both slag blocking and filtering functions is used to filter the slag; the slag is demoulded after cooling in the steel mold.