Low-density steel material and preparation method thereof

Abstract

The invention relates to a low-density steel material and a preparation method thereof. The material comprises the following chemical components in percentage by mass: 0.7-1.1% of C, 5-11% of Al, 0.3-0.9% of Si, 10-15% of Mn, 3-5% of Ni, 0.001-0.002% of Ce and the balance of Fe. A medium-frequency induction furnace remelting process is adopted, the return scrap and the high-manganese steel waste are used as main raw materials, 40% of the return scrap and 60% of the high-manganese steel waste are used as raw materials for smelting, the content of Mn in the steel is reduced, and the work hardening of the material is improved; the cost of the low-density steel is reduced, and the weight of the low-density steel is reduced by about 10% compared with 42CrMo; by adding the rare earth Ce, the problem that the Al element yield is low when low-density steel is smelted in an intermediate frequency furnace is solved, smelting of the material in an intermediate frequency induction furnace is achieved, and meanwhile the chemical components of the steel are guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of low-density steel manufacturing, specifically relating to a low-density steel material and its preparation method, and in particular, a low-cost novel low-density steel material and its preparation method. Background Technology

[0002] Fe-Mn-Al-C series high-strength steel is a widely studied low-density steel. For every 1% Al added to the steel, the density decreases by 0.101 g / cm³. 3 For every 1% increase in carbon (C) added to steel, the density decreases by 0.41 g / cm³. 3 For every 1% Mn added to steel, the density decreases by 0.0086 g / cm³. 3 Its density can reach 6.2 g / cm³. 3 -7.2g / cm 3 The commonly used low-density steel A350L-2 has a density of 6.8 g / cm³. 3 It has a tensile strength ≥950MPa, yield strength ≥700MPa, elongation ≥15%, impact energy ≥50J, and a price of approximately 50,000 yuan / ton. Currently, it is mainly produced in the form of low-density steel plates.

[0003] Fe-Mn-Al-C series low-density steels, with their high Mn and Al content, are prone to reaction with O and S during the smelting process, reducing the internal quality of the material. To prevent oxidation, vacuum induction furnaces are required for smelting, leading to high smelting costs. Simultaneously, the high C, Mn, and Al content results in severe work hardening, making the material susceptible to oxidation during machining. The finished sheet surface is pale yellow, and the machining process causes significant tool sticking and damage, limiting the widespread use of low-density steel in lightweight structural components. Summary of the Invention

[0004] This invention provides a low-density steel material and its preparation method. The low-density steel material is manufactured by remelting in a medium-frequency induction furnace. By selecting appropriate cutting tools and optimizing processing parameters, the processing performance of the low-density steel is improved.

[0005] To solve the above technical problems, the present invention provides a low-density steel material, characterized in that its chemical composition by mass percentage is: C 0.7~1.1%, Al 5~11%, Si 0.3~0.9%, Mn 10~15%, Ni 3~5%, Ce 0.001~0.002%, with the balance being Fe and unavoidable impurities.

[0006] Furthermore, its density is 6.8~7.4 g / cm³.

[0007] A method for preparing the aforementioned low-density steel material, characterized by comprising the following steps: S1. Prepare low-density steel plate return material and high-manganese steel processing waste as raw materials in proportion; S2. Add the raw materials to a medium-frequency induction furnace and heat them to 1610~1680℃ to melt them; S3. Add ferrosilicon for deoxidation and add slag collector to remove impurities; S4. After adjusting the Al content, add 0.45~0.50 kg of rare earth alloy and cast to obtain steel ingots.

[0008] Furthermore, the mass ratio of the returned material to the waste material is 4:6.

[0009] Furthermore, the rare earth alloy contains 19% Ce and 81% Fe.

[0010] Furthermore, the pouring temperature is 1520~1610℃.

[0011] Furthermore, the cast steel ingot undergoes heat treatment: Hold at 950~1050℃ for 0.5~1h, then oil-cool. It was then kept at 690℃ for 0.2~0.3 hours and then water-cooled.

[0012] Furthermore, in S2, the weight of a single furnace of molten steel is 200 kg.

[0013] Further, the recycled material and waste are added to the medium-frequency induction furnace, along with some nickel plates, and then heating begins. The power is continuously increased during the heating process until it reaches 1610ºC~1680ºC, at which point all the raw materials are melted.

[0014] Furthermore, rare earth alloys have a density comparable to that of steel.

[0015] Beneficial effects: This invention designs a new low-density steel with a low-cost chemical composition. It replaces vacuum induction furnace melting with medium-frequency induction furnace raw material remelting and uses high-manganese steel processing waste and low-density steel plate return materials to replace alloy materials to manufacture low-density steel materials. At the same time, by selecting cutting tools and optimizing processing parameters, it achieves efficient processing of low-cost new low-density steel, reduces material manufacturing costs, and improves the processing performance of low-density steel. Detailed Implementation

[0016] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below.

[0017] The present invention proposes a low-density steel material, the chemical composition of which, by mass percentage, is: C 0.7~1.1%, Al 5~11%, Si 0.3~0.9%, Mn 10~15%, Ni 3~5%, Ce 0.001~0.002%, with the balance being Fe and unavoidable impurities.

[0018] A method for preparing low-density steel material, the specific steps of which are as follows: (1) Prepare the return material and scrap required for smelting, of which 40% is Fe-Mn-Al-C series low-density steel plate return material (chemical composition: C 1.0~1.2%, Al 10~12%, Si 0.3~0.9%, Mn 25~30%, Fe is the balance), and 60% is high manganese steel processing scrap. The weight of a single furnace of molten steel is 200kg. Add the return material and scrap to the medium frequency induction furnace, add some nickel plates, and then start heating. During the heating process, continuously increase the power until it is heated to 1610ºC~1680ºC, at which point all the raw materials are melted.

[0019] (2) After the steel melts, ferrosilicon is added to the steel to deoxidize it. At the same time, a slag collector is added to the surface of the steel during the melting process to collect the impurities inside the steel on the surface of the induction furnace. The impurities are removed by using tools such as spoons. The slag collection process is repeated many times until the surface of the steel is visually clean and free of impurities. At this time, the chemical composition of the steel is tested online.

[0020] (3) At this point, observe the difference between the Al content in the molten steel and the set value. Then, add aluminum wire to the molten steel. After sampling and testing the chemical composition and finding it to be qualified, add 0.45~0.50 kg of rare earth alloy to the molten steel. The rare earth alloy contains 19% Ce and 81% Fe elements, with a density of approximately 7.8 g / cm³. 3 It has a density similar to that of steel, so it will not float on top of molten steel.

[0021] (4) After adding rare earth elements for 1-2 minutes, begin pouring at a temperature of 1520-1610ºC. The tested density result is 7.2 g / cm³. 3 This resulted in a reduction in weight; A heat treatment method for low-density steel: The low-density steel is subjected to water quenching, held at 950~1050ºC for 0.5~1h, cooled in oil, then held at 690ºC for 0.2~0.3h, and cooled in water to obtain the final state of the low-density steel.

[0022] The drilling process for low-density steel plates using the material of this invention is as follows: (1) Drilling is divided into two parts: centering and drilling. A carbide center drill is used to center the low-density steel. The linear speed is 150-200m / min, the feed rate is 0.2-0.3mm / rev, and the depth is 3-5mm. For drilling, a solid carbide drill bit with CrN coating is used. A large helix angle and parabolic groove design are selected. Small feed is avoided during the machining process to prevent hardening. High speed is avoided to prevent thermal wear. Moderate feed is used. The linear speed is 80-120m / min and the feed rate is 0.15-0.25mm / rev. (2) After drilling, use an integral carbide chamfering tool to remove burrs around the hole. The surface of the processed material has a silvery-white metallic luster.

[0023] Therefore, it can be seen that the low-density steel using the material of this invention has excellent effects.

[0024] Example 1: Smelting of low-density steel The raw materials were prepared according to the following mass percentages: C 0.8%, Al 8%, Si 0.6%, Mn 12%, Ni 4%, Ce 0.0015%, with the balance being Fe and unavoidable impurities. 40% recycled low-density steel plate and 60% high-manganese steel scrap were added to a medium-frequency induction furnace, along with a nickel plate, and heated to 1650℃ for melting. Ferrosilicon was added for deoxidation, and after slag collection and impurity removal, a sample was taken. Aluminum wire was added to adjust the Al content, and then 0.48 kg of rare earth alloy (containing 19% Ce and 81% Fe) was added. After 1.5 minutes, the mixture was poured at 1560℃, and the density was measured to be 7.2 g / cm³.

[0025] Example 2: Heat Treatment The above steel ingots were subjected to water quenching: held at 1000℃ for 45 minutes, then oil cooled; subsequently held at 690℃ for 0.25 hours, then water cooled.

[0026] Example 3: Drilling Centering was performed using a carbide center drill at a linear speed of 180 m / min, a feed rate of 0.25 mm / rev, and a depth of 4 mm. Drilling was then carried out using a solid carbide drill bit with a CrN coating and a large helix angle parabolic flute, at a linear speed of 100 m / min and a feed rate of 0.2 mm / rev. The finished surface has a silvery-white metallic luster.

[0027] Key points of the invention 1. Controlling the chemical composition of low-density steel involves reducing the Mn content while ensuring the steel's strength; 2. Control of microalloying elements in steel: Adding rare earth elements improves the machinability of steel. The timing of rare earth addition must be precisely controlled during the smelting process. Adding rare earth elements too early or too late will lead to severe oxidation of rare earth elements and poor results.

[0028] The advantages of this invention are: 1. Using 40% recycled material and 60% high-manganese steel scrap as raw materials for smelting reduces the Mn content in the steel and improves the work hardening of the material; 2. The cost of low-density steel is reduced, and its weight is reduced by about 10% compared with 42CrMo; 3. The addition of rare earth Ce solves the problem of low Al element recovery rate in the medium-frequency furnace smelting of low-density steel, realizing the smelting of this material in a medium-frequency induction furnace while ensuring the chemical composition of the steel.

[0029] 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 technical principles 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 low-density steel material, characterized in that, Its chemical composition by mass percentage is: C 0.7~1.1%, Al 5~11%, Si 0.3~0.9%, Mn 10~15%, Ni 3~5%, Ce 0.001~0.002%, with the balance being Fe and unavoidable impurities.

2. The low-density steel material according to claim 1, characterized in that, Its density is 6.8~7.4 g / cm³.

3. A method for preparing the low-density steel material as described in claim 1, characterized in that, Includes the following steps: S1. Prepare low-density steel plate return material and high-manganese steel processing waste as raw materials in proportion; S2. Add the raw materials to a medium-frequency induction furnace and heat them to 1610~1680℃ to melt them; S3. Add ferrosilicon for deoxidation and add slag collector to remove impurities; S4. After adjusting the Al content, add 0.45~0.50 kg of rare earth alloy and cast to obtain steel ingots.

4. The preparation method according to claim 3, characterized in that, The mass ratio of the recycled material to the waste material is 4:

6.

5. The preparation method according to claim 3, characterized in that, The rare earth alloy contains 19% Ce and 81% Fe.

6. The preparation method according to claim 3, characterized in that, The pouring temperature is 1520~1610℃.

7. The preparation method according to claim 3, characterized in that, Heat treatment is performed on the cast steel ingot: Hold at 950~1050℃ for 0.5~1h, then oil-cool. It was then kept at 690℃ for 0.2~0.3 hours and then water-cooled.

8. The preparation method according to claim 3, characterized in that, In S2, the weight of molten steel in a single furnace is 200 kg.

9. The preparation method according to claim 3, characterized in that, Returned materials and waste are added to the medium-frequency induction furnace, along with some nickel plates. Heating begins, with the power continuously increased until the temperature reaches 1610ºC~1680ºC, at which point all the raw materials are melted.

10. The preparation method according to claim 3, characterized in that, Rare earth alloys have a density comparable to that of steel.