Process for producing high-strength steel using scrap steel and nickel plate

Abstract

The application relates to the alloy production technical field, and proposes a process for producing high-strength steel by using scrap steel and nickel plates, which comprises the following steps: S1, performing shot blasting rust removal treatment on the scrap steel, performing baking treatment on the nickel plate and the alloy respectively, and obtaining the treated scrap steel, the nickel plate and the alloy; S2, smelting the treated scrap steel, the nickel plate and the alloy, adding slagging materials to perform slagging during the smelting process, and obtaining molten steel after the smelting is completed; S3, adding vanadium iron into the molten steel to perform refining, and obtaining refined molten steel; S4, transferring the refined molten steel to a ladle, adding aluminum wire and silicon-calcium wire for deoxidation treatment, and then performing continuous casting to obtain continuous casting billets; and S5, performing heat treatment on the continuous casting billets to obtain high-strength steel; the alloy is chromium iron, molybdenum iron, silicon iron and manganese iron. Through the above technical scheme, the problems of dendrite deflection, cracks, coarse grains and long heat treatment process period of the steel plate in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the field of alloy production technology, specifically to a process for producing high-strength steel using scrap steel and nickel plates. Background Technology

[0002] Starting in the early 1940s, the U.S. Navy pioneered the development of high-strength low-alloy steel to save on shipbuilding costs. This steel not only replaced ordinary steel but also met strength and toughness requirements, while possessing excellent weldability. Currently, ultra-high-strength steel is widely used in metallurgy, mining, engineering machinery, and power industries. High-strength steel not only possesses high strength but also high toughness. However, due to unstable domestic production technology and quality control, problems such as non-metallic inclusions, internal cracks, and short service life occur during the production of high-strength steel, severely limiting the utilization rate of steel plates. In recent years, with the continuous and steady development of my country's steel and automotive industries, researchers both domestically and internationally have developed a large number of new types of steel, such as aluminum alloys, magnesium alloys, and nickel alloys. However, with the increase in the content of various alloying elements in steel, dendrite deflection is easily formed during the solidification process of molten steel.

[0003] Currently, high-strength steel produced using nickel-containing alloys suffers from high nickel content, casting defects such as dendrite deflection, a high tendency to crack, low elongation, and requires numerous heat treatment steps with a cycle of 10-15 days. If rework is required due to lower performance, the cost and time become even higher. Therefore, to address the shortcomings of existing steel plates, such as dendrite deflection, cracking, coarse grains, and long heat treatment cycles, it is crucial to develop a process for producing high-strength steel. Summary of the Invention

[0004] This invention proposes a process for producing high-strength steel using scrap steel and nickel plates, which solves the defects of steel plates in related technologies, such as dendrite deflection, cracks, coarse grains, and long heat treatment process cycles.

[0005] The technical solution of the present invention is as follows:

[0006] This invention proposes a process for producing high-strength steel using scrap steel and nickel plates, comprising the following steps:

[0007] S1. The scrap steel is shot blasted to remove rust, and the nickel plate and alloy are baked separately to obtain the treated scrap steel, nickel plate and alloy.

[0008] S2. The processed scrap steel, nickel plate and alloy are smelted. Slag-forming materials are added during the smelting process to form slag. After smelting is completed, molten steel is obtained.

[0009] S3. Add ferrovanadium to the molten steel and refine it to obtain refined molten steel;

[0010] S4. Transfer the refined molten steel to a ladle, add aluminum wire and silicon-calcium wire for deoxidation treatment, and then continuously cast to obtain a continuously cast billet.

[0011] S5. Heat treat the continuously cast billet to obtain high-strength steel;

[0012] As a further technical solution, the heat treatment is high-temperature normalizing at 950~1000℃, conventional normalizing at 800~900℃, oil quenching at 800~900℃, tempering at 100~200℃, and secondary tempering at 100~200℃.

[0013] As a further technical solution, the alloy is ferrochrome, ferromolybdenum, ferrosilicon, and ferromanganese.

[0014] As a further technical solution, based on the added mass of scrap steel, the added mass of ferrochrome is 10~25 kg / t, the added mass of nickel plate is 10~25 kg / t, the added mass of ferromolybdenum is 5~10 kg / t, the added mass of ferrosilicon is 9~12 kg / t, and the added mass of ferromanganese is 9~12 kg / t.

[0015] As a further technical solution, the nickel plate has a nickel content of ≥99%.

[0016] As a further technical solution, the ferrochrome contains ≥60% chromium, the ferromolybdenum contains ≥60% molybdenum, the ferrosilicon contains ≥70% silicon, and the ferromanganese contains ≥65% manganese.

[0017] As a further technical solution, the baking temperature of the nickel plate is 500~700℃ and the baking time is 1~3h, and the baking temperature of the alloy is 100~150℃ and the baking time is 1~2h.

[0018] As a further technical solution, the baking temperature of the nickel plate is 630℃ and the baking time is 2 hours, and the baking temperature of the alloy is 135℃ and the baking time is 80 minutes.

[0019] As a further technical solution, the slag-forming material comprises the following components in parts by weight: 40-60 parts of active limestone, 10-20 parts of calcium hydroxide, 5-10 parts of magnesite, 1-3 parts of fluorite, and 1-3 parts of sodium fluoride.

[0020] As a further technical solution, the amount of slag-forming material added is 0.5‰ to 1‰ of the mass of scrap steel.

[0021] As a further technical solution, the active limestone is limestone modified with aluminate and hexadecanoic acid.

[0022] As a further technical solution, the sum of the mass of the aluminate and hexadecanoic acid is 0.5% to 1.5% of the mass of limestone, and the mass ratio of the aluminate to hexadecanoic acid is 5:5 to 7:3.

[0023] As a further technical solution, the slag-forming temperature is 1000~1500℃.

[0024] As a further technical solution, the high-strength steel is composed of the following components by mass percentage: C: 0.26%~0.29%, Si: 0.8%~1.0%, Mn: 0.8%~1.0%, P≤0.02%, S≤0.02%, Cr: 0.9%~1.1%, Ni: 1.9%~2.2%, Mo: 0.35%~0.45%, Cu: ≤0.3%, Al: ≤0.015%, V: 0.06%~0.08%, Ca: 0.1%, Zr≤0.003%, N≤0.010%, with the balance being Fe and unavoidable impurities.

[0025] The working principle and beneficial effects of this invention are as follows:

[0026] 1. In this invention, shot blasting of scrap steel for rust removal and baking of nickel plates and alloys respectively remove moisture from the added scrap steel, nickel plates, and alloys, reducing energy consumption. Adding slag-forming materials to the molten steel during smelting effectively removes phosphorus and sulfur impurities during steel plate casting, protects the molten steel from excessive oxidation and absorption of harmful gases, reduces the loss of beneficial elements, ensures the smooth discharge of carbon monoxide from the molten steel, and reduces the tendency for steel plate cracking. Adding ferrovanadium to the molten steel after smelting significantly improves the strength and ductility of the steel. Adding aluminum wire and calcium silicon wire for deoxidation reduces the solubility of oxygen in the steel plate, preventing subcutaneous bubbles and porosity defects during casting, reducing the hot brittleness of the steel plate, and thus reducing dendrite deflection. Heat treatment improves the strength, toughness, and weldability of the steel plate, removes internal stress, and effectively reduces dendrite deflection. By adding ferrochrome, ferromolybdenum, ferrosilicon, and ferromanganese to the alloy, low-carbon alloys can be formed with scrap steel, thereby improving the tensile strength and elongation of high-strength steel.

[0027] 2. In this invention, a mixture of aluminate and hexadecanoic acid is added to limestone, which increases the specific surface area of ​​the limestone slag-forming material, refines the limestone grains, and reduces the water absorption of limestone to comprehensively improve the activity of limestone, thereby increasing the slag-forming speed, reducing the slag-forming time, and effectively improving the tensile strength of steel plates.

[0028] 3. In this invention, the heat treatment process of high-temperature normalizing, conventional normalizing, oil quenching, tempering, and secondary tempering improves the toughness, strength, and plasticity of the steel plate and reduces cracking. The secondary tempering can more fully transform the residual austenite in the steel plate, thereby increasing the strength of the steel. The heat treatment process shortens the high-temperature time by 10 hours, thereby shortening the heat treatment cycle time by 29%, and increasing the steel plate elongation qualification rate by 72%. This effectively improves the casting efficiency and tensile strength of the steel plate and significantly reduces production costs. Attached Figure Description

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0030] Figure 1 The microstructure of the high-strength steel prepared in Example 1 is shown in the as-cast microstructure analysis diagram.

[0031] Figure 2 The microstructure of the high-strength steel prepared in the normalized state is shown in Figure 1.

[0032] Figure 3 The microstructure of the high-strength steel prepared in Example 1 in the quenched state is shown in the diagram.

[0033] Figure 4 The image shows the microstructure of the high-strength steel prepared in Example 1 in the tempered state. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] The scrap steel contains ≥65% iron, nickel plates contain ≥99% nickel, ferrochrome contains ≥60% chromium, ferromolybdenum contains ≥60% molybdenum, ferrosilicon contains ≥70% silicon, ferromanganese contains ≥65% manganese, and ferrovanadium contains ≥40% vanadium.

[0036] Magnesite composition: MgO 35%~47%, CaO 0.2%-4%, SO2 0.2%~8%, Fe2O3 and Al2O3 ≤1%.

[0037] Example 1

[0038] Preparation of pre-treated scrap steel, nickel plate, and alloy: 1 ton of scrap steel is shot blasted to remove rust. 10 kg of nickel plate is placed in a baking furnace and baked at 500°C for 1 hour. 10 kg of ferrochrome, 5 kg of ferromolybdenum, 9 kg of ferrosilicon, and 9 kg of ferromanganese are placed in another baking furnace and baked at 100°C for 1 hour.

[0039] Preparation of activated limestone: 1.25g aluminate and 1.25g hexadecanoic acid were added to 200ml anhydrous ethanol, stirred and dispersed, heated to 80℃, and 500g limestone powder was added. The mixture was stirred for 30min to obtain activated limestone.

[0040] Pretreated scrap steel, nickel plates, and alloys are transferred to a smelting furnace and smelted at 1000℃. Slag is formed by adding 0.4 kg of active limestone, 0.1 kg of calcium hydroxide, 0.05 kg of magnesite, 0.01 kg of fluorite, and 0.01 kg of sodium fluoride. The resulting molten steel is then transferred to a refining furnace, where 0.003 kg of ferrovanadium is added. The furnace is then refined at 1200℃ to obtain refined molten steel. This refined steel is transferred to a ladle. 0.5 kg of aluminum wire is added to the bottom of the ladle, followed by another 0.5 kg of aluminum wire and 0.5 kg of silicon-calcium wire. The ladle is then deoxidized and continuously cast to obtain a continuously cast billet. The billet is then subjected to high-temperature normalizing at 997℃, conventional normalizing at 895℃, oil quenching at 853℃, tempering at 103℃ for 1 hour, and a second tempering at 106℃ for 2 hours to obtain high-strength steel.

[0041] The high-strength steel of Example 1 underwent microstructural analysis in its as-cast, normalized, quenched, and tempered states during the manufacturing process. Figure 1-4 As shown;

[0042] Among them, the as-cast microstructure analysis shows obvious dendrites and regional segregation; it consists of blocky ferrite + fine pearlite + a small amount of bainite; there is obvious micro shrinkage porosity and inclusions.

[0043] Normalized microstructure analysis: The microstructure consists of ferrite + pearlite + a small amount of granular bainite, with an actual grain size of 5-6.

[0044] Analysis of the microstructure in the quenched state: The microstructure is quenched martensite, with an actual grain size of 6-7.

[0045] Analysis of the microstructure in the tempered state: The microstructure is tempered martensite, with an actual grain size of 6-7.

[0046] Example 2

[0047] Preparation of pre-treated scrap steel, nickel plates, and alloys: 1 ton of scrap steel is shot blasted to remove rust. 20 kg of nickel plates are placed in a baking furnace and baked at 600°C for 2 hours. 20 kg of ferrochrome, 10 kg of ferromolybdenum, 9 kg of ferrosilicon, and 9 kg of ferromanganese are placed in another baking furnace and baked at 150°C for 1.5 hours.

[0048] Preparation of activated limestone: 6g of aluminate and 4g of hexadecanoic acid were added to 200ml of anhydrous ethanol, stirred and dispersed, heated to 80℃, and 1000g of limestone powder was added. The mixture was stirred for 30min to obtain activated limestone.

[0049] Pretreated scrap steel, nickel plates, and alloys are transferred to a smelting furnace and smelted at 1000℃. 0.5 kg of active limestone, 0.1 kg of calcium hydroxide, 0.07 kg of magnesite, 0.03 kg of fluorite, and 0.03 kg of sodium fluoride are added to form slag, yielding molten steel. The molten steel is then transferred to a refining furnace, where 0.003 kg of ferrovanadium is added, and the furnace is refined at 1200℃ to obtain refined molten steel. The refined molten steel is transferred to a ladle, where 0.5 kg of aluminum wire is added to the bottom and then to the inside of the ladle, followed by 0.5 kg of silicon-calcium wire for deoxidation. The ladle is then continuously cast to obtain a continuously cast billet. The continuously cast billet is subjected to high-temperature normalizing at 997℃, conventional normalizing at 895℃, oil quenching at 853℃, tempering at 103℃ for 1 hour, and secondary tempering at 106℃ for 2 hours to obtain high-strength steel.

[0050] Example 3

[0051] Pretreatment preparation of scrap steel, nickel plate, and alloy: 1 ton of scrap steel is shot blasted to remove rust. 25 kg of nickel plate is placed in a baking furnace and baked at 700°C for 3 hours. 25 kg of ferrochrome, 10 kg of ferromolybdenum, 12 kg of ferrosilicon, and 12 kg of ferromanganese are placed in another baking furnace and baked at 150°C for 2 hours.

[0052] Preparation of activated limestone: 10.5g aluminate and 4.5g hexadecanoic acid were added to 200ml anhydrous ethanol, stirred and dispersed, heated to 80℃, and 1000g limestone powder was added. The mixture was stirred for 30min to obtain activated limestone.

[0053] Pretreated scrap steel, nickel plates, and alloys are transferred to a smelting furnace and smelted at 1000℃. 0.6 kg of active limestone, 0.2 kg of calcium hydroxide, 0.1 kg of magnesite, 0.03 kg of fluorite, and 0.03 kg of sodium fluoride are added to obtain molten steel. The molten steel is then transferred to a refining furnace, where 0.003 kg of ferrovanadium is added, and the mixture is refined at 1200℃ to obtain refined molten steel. The refined molten steel is then transferred to a ladle. 0.5 kg of aluminum wire is first added to the bottom of the ladle, followed by another 0.5 kg of aluminum wire and 0.5 kg of silicon-calcium wire. After deoxidation, the ladle is continuously cast to obtain a continuously cast billet. The continuously cast billet is then subjected to high-temperature normalizing at 997℃, conventional normalizing at 895℃, oil quenching at 853℃, tempering at 103℃ for 1 hour, and a second tempering at 106℃ for 2 hours to obtain high-strength steel.

[0054] Example 4

[0055] The only difference between this embodiment and Embodiment 1 is that 15 kg of ferromanganese and 35 kg of nickel plate are added during the preparation of scrap steel, nickel plate, and alloy pretreatment.

[0056] Example 5

[0057] The only difference between this embodiment and Embodiment 1 is that 15 kg of ferromanganese is added during the preparation of scrap steel, nickel plates, and alloy pretreatment.

[0058] Example 6

[0059] The only difference between this embodiment and Embodiment 1 is that 35 kg of nickel plate is added during the preparation of scrap steel, nickel plate, and alloy pretreatment.

[0060] Example 7

[0061] The only difference between this embodiment and Embodiment 1 is the addition of 0.4 kg of limestone, without any modification.

[0062] Example 8

[0063] The only difference between this embodiment and Example 1 is that only 2.5g of aluminate was added during the modification of the active limestone.

[0064] Example 9

[0065] The only difference between this embodiment and Example 1 is that only 2.5g of hexadecanoic acid was added during the modification of the active limestone.

[0066] Examples 10-15 and Comparative Examples 1-5 differ from Example 1 only in the heat treatment, the specific heat treatment conditions of which are shown in the table below:

[0067]

[0068] The compositions of the high-strength steels obtained in Examples 1, 10-15, 1-5, and 2-6 are shown in the table below:

[0069]

[0070] The high-strength steels obtained in Examples 1-15 and Comparative Examples 1-5 were tested for tensile strength and elongation according to the test methods of GB / T20564.4-2022.

[0071]

[0072] In summary, based on the data from Examples 1, 10-15 and Comparative Examples 1-5, it can be seen that the present invention can significantly improve the tensile strength and elongation of high-strength steel through heat treatment of high-temperature normalizing at 950~1000℃, conventional normalizing at 800~900℃, oil quenching at 800~900℃, tempering at 100~200℃, and secondary tempering at 100~200℃.

[0073] According to the data from Examples 1 and 4-6, it can be seen that by adding 10-25 kg / t of nickel plate and 9-12 kg / t of ferromanganese to scrap steel, the present invention can improve the tensile strength and elongation of high-strength steel.

[0074] Based on the data from Examples 1 and 7, it can be seen that modifying limestone can significantly improve the tensile strength of high-strength steel.

[0075] According to the data in Examples 1 and 8-9, the present invention improves the tensile strength of high-strength steel by modifying limestone with a mixture of aluminate and hexadecanoic acid.

[0076] According to the data in Example 1 and Comparative Example 1, the present invention significantly improves the tensile strength and elongation of high-strength steel through oil quenching heat treatment process.

[0077] According to the data in Example 1 and Comparative Example 2, the present invention fully transforms the residual austenite through a secondary tempering heat treatment process, which significantly improves the tensile strength and elongation of high-strength steel.

[0078] Based on the data from Example 1 and Comparative Examples 3-4, it can be seen that the present invention can significantly improve the tensile strength and elongation of high-strength steel by high-temperature normalizing at 950~1000℃ and conventional normalizing at 800~900℃.

[0079] According to the data from Example 1 and Comparative Example 5, the oil quenching process of the present invention at 800~900℃ can significantly improve the tensile strength and elongation of high-strength steel.

[0080] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for producing high-strength steel using scrap steel and nickel plates, characterized in that, Includes the following steps: S1. The scrap steel is shot blasted to remove rust, and the nickel plate and alloy are baked separately to obtain the treated scrap steel, nickel plate and alloy. S2. The processed scrap steel, nickel plate and alloy are smelted. Slag-forming materials are added during the smelting process to form slag. After smelting is completed, molten steel is obtained. S3. Add ferrovanadium to the molten steel and refine it to obtain refined molten steel; S4. Transfer the refined molten steel to a ladle, add aluminum wire and silicon-calcium wire for deoxidation treatment, and then continuously cast to obtain a continuously cast billet. S5. Heat-treat the continuously cast billet to obtain high-strength steel; the heat treatment is high-temperature normalizing at 950~1000℃, conventional normalizing at 800~900℃, oil quenching at 800~900℃, tempering at 100~200℃ and holding, and secondary tempering at 100~200℃ and holding. The slag-forming material comprises the following components in parts by weight: 40-60 parts of active limestone, 10-20 parts of calcium hydroxide, 5-10 parts of magnesite, 1-3 parts of fluorite, and 1-3 parts of sodium fluoride. The active limestone is limestone modified with aluminate and hexadecanoic acid; The high-strength steel is composed of the following components by mass percentage. Composition: C: 0.26%~0.29%, Si: 0.8%~1.0%, Mn: 0.8%~1.0%, P≤0.02%, S≤0.02%, Cr: 0.9%~1.1%, Ni: 1.9%~2.2%, Mo: 0.35%~0.45%, Cu: ≤0.3%, Al: ≤0.015%, V: 0.06%~0.08%, Ca: 0.1%, Zr≤0.003%, N≤0.010%, with the balance being Fe and unavoidable impurities.

2. The process for producing high-strength steel using scrap steel and nickel plates according to claim 1, characterized in that, The alloy is ferrochrome, ferromolybdenum, ferrosilicon, and ferromanganese.

3. The process for producing high-strength steel using scrap steel and nickel plates according to claim 2, characterized in that, Based on the mass of scrap steel added, the mass of ferrochrome added is 10~25 kg / t, the mass of nickel plate added is 10~25 kg / t, the mass of ferromolybdenum added is 5~10 kg / t, the mass of ferrosilicon added is 9~12 kg / t, and the mass of ferromanganese added is 9~12 kg / t.

4. The process for producing high-strength steel using scrap steel and nickel plates according to claim 1, characterized in that, The nickel plate is baked at a temperature of 500-700℃ for 1-3 hours, and the alloy is baked at a temperature of 100-150℃ for 1-2 hours.

5. The process for producing high-strength steel using scrap steel and nickel plates according to claim 1, characterized in that, The amount of slag-forming material added is 0.5‰ to 1‰ of the mass of scrap steel.

6. The process for producing high-strength steel using scrap steel and nickel plates according to claim 1, characterized in that, The sum of the mass of the aluminate and hexadecanoic acid added is 0.5% to 1.5% of the mass of limestone, and the mass ratio of the aluminate to hexadecanoic acid is 5:5 to 7:

3.

7. The process for producing high-strength steel using scrap steel and nickel plates according to claim 1, characterized in that, The slag-forming temperature is 1000~1500℃.

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