Steel bar for mining machinery and preparation method thereof

Abstract

The invention discloses a steel bar for mining machinery and a preparation method of the steel bar. The steel bar for the mining machinery comprises the following components in percentage by mass: 0.38%-0.43% of C, 0.22%-0.35% of Si, 0.95%-1.10% of Mn, less than or equal to 0.015% of P, less than or equal to 0.010% of S, 0.95%-1.10% of Cr, less than or equal to 0.25% of Ni, less than or equal to 0.05% of Mo, less than or equal to 0.15% of Cu and the balance of iron and inevitable impurities. The steel bar for the mining machinery is produced through the ecological electric furnace smelting, LF, RH, continuous casting and rolling technology, the high-end use requirement is met, the breakthrough of batch production of the steel bar for the mining machinery in the ecological electric furnace continuous casting process is achieved, the indexes such as the mechanical property and the high steel purity of finished steel of the steel bar for the mining machinery are guaranteed, and the production cost is reduced. And the surface quality level of the steel bar for the mining machinery is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of materials and metallurgy, and more specifically, to a steel bar for mining machinery and a preparation method thereof. Background Art

[0002] Mining machinery is a machine used directly for mineral mining and enrichment, serving important basic industrial sectors such as ferrous and nonferrous metallurgy, coal, building materials, chemical industry, and nuclear industry, and plays a very important role in most operations, even as a safety guarantee. The quality of steel used in mining machinery directly affects the service life and wear resistance of mining machinery, and even affects the safety of the entire vehicle operation process.

[0003] Currently, steel used in mining machinery has many impurities, poor wear resistance, low fatigue life, and mechanical properties that are difficult to meet application requirements. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and to provide a steel bar for mining machinery and a preparation method thereof. The steel bar for mining machinery produced by the ecological electric furnace smelting + LF + RH + continuous casting and rolling process meets the high-end use requirements and realizes a breakthrough in the batch production of steel bars for mining machinery by the ecological electric furnace continuous casting process. It not only ensures the mechanical properties of the finished steel and high steel purity of the steel bars for mining machinery, but also ensures the surface quality level of the steel bars for mining machinery, meeting the quality requirements of steel bars for mining machinery.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A steel bar for mining machinery comprises the following components in percentage by mass: C: 0.38% to 0.43%, Si: 0.22% to 0.35%, Mn: 0.95% to 1.10%, P≤0.015%, S≤0.010%, Cr: 0.95% to 1.10%, Ni≤0.25%, Mo≤0.05%, Cu≤0.15%, and the balance is iron and unavoidable impurities.

[0007] The present invention also discloses a method for preparing the steel bar for mining machinery as described above, comprising the following steps: ecological electric furnace smelting, LF refining, RH vacuum refining, continuous casting, heating process, rolling process and heat preservation process;

[0008] In the ecological electric furnace smelting, scrap steel is used as the furnace charge, and the scrap steel accounts for 100% by mass; the final composition of the electric furnace is: C: 0.15% to 0.18%, P ≤ 0.010%; deoxidation and alloying are performed during the steel tapping process;

[0009] In the LF refining, the molten steel discharged from the ecological electric furnace is put into the LF furnace for refining treatment;

[0010] During the RH vacuum refining, the molten steel treated by the LF refining is hoisted into the RH vacuum furnace for refining;

[0011] During the continuous casting, the molten steel after the RH vacuum refining treatment is continuously cast to obtain a continuously cast ingot, and the continuously cast ingot is sent to a heating furnace for heating, and then rolled and kept warm in sequence to obtain the steel bar for mining machinery.

[0012] Implementing the embodiments of the present invention will have the following beneficial effects:

[0013] (1) The 100t ECOARC ecological electric furnace + LF + RH + 390mm*480mm smelting process and rolling process are used to produce steel bars for mining machinery. The production specification is Φ130mm, which meets the mechanical performance requirements and ensures the purity of the steel.

[0014] (2) Reasonable component design and production process ensure surface quality and mechanical properties.

[0015] (3) The macrostructure and non-metallic inclusions of the finished steel meet the requirements of high-end products. DETAILED DESCRIPTION

[0016] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited in any way.

[0017] 1. Chemical composition

[0018] The invention discloses a steel bar for mining machinery, comprising the following components in weight percentage: C: 0.38%-0.43%, Si: 0.22%-0.35%, Mn: 0.95%-1.10%, P≤0.015%, S≤0.010%, Cr: 0.95%-1.10%, Ni≤0.25%, Mo≤0.05%, Cu≤0.15%, and the balance is iron and inevitable impurities.

[0019] 2. Production technology

[0020] The method for preparing a steel bar for mining machinery of the present invention comprises the following steps: ecological electric furnace smelting, LF refining, RH vacuum refining, continuous casting, heating process, rolling process and heat preservation process.

[0021] Further, the method specifically includes the following steps:

[0022] S1. In the ecological electric furnace smelting, scrap steel is used as the charge, and the scrap steel accounts for 100% by mass; the final composition of the electric furnace: C: 0.15%~0.18%, P≤0.010%; deoxidation and alloying are carried out during the steelmaking process.

[0023] In a specific embodiment, step S1 specifically includes: the scrap steel includes heavy scrap steel and lump-type scrap steel; wherein the mass percentage of heavy scrap steel in the charge is 80% to 95%; the tapping temperature is 1630°C to 1640°C; slag, pre-deoxidizer, and alloy are added when 1 / 4 to 1 / 3 of the steel is tapped, the tapping amount is 108t to 112t, and the smelting cycle is 45min to 50min; the amount of alloy added per ton of steel: 6.1Kg / t to 6.2Kg / t Silicon manganese, 7.1Kg / t~7.2Kg / t high carbon ferromanganese, 14Kg / t~14.2Kg / t high carbon ferrochrome, 1.1Kg / t~1.2Kg / t aluminum segments; auxiliary materials added per ton of steel: 45Kg / t~46Kg / t active lime, 1.0Kg / t~1.1Kg / t coke particles, 20Kg / t~21Kg / t magnesite, 6Kg / t~6.2Kg / t ladle ash.

[0024] In a specific embodiment, the size of the aluminum wire segment is Φ10mm-Φ16mm; the particle size of the active lime is 10mm-70mm; and the particle size of the magnesite is 10mm-60mm.

[0025] In a specific embodiment, 100% scrap steel is smelted, including 110t-113t of heavy scrap steel and 10t-11t of lump-type scrap steel.

[0026] In S2 and LF refining, the molten steel discharged from the ecological electric furnace is put into the LF furnace for refining.

[0027] In a specific embodiment, step S2 specifically includes: the LF inlet temperature is 1520°C to 1530°C, and after heating and melting the slag with a large current of 35000A to 36000A, when the slag surface fluctuates and the molten steel and the arc are not exposed, 4.5Kg / t steel to 5.5Kg / t steel of active lime is added, and the chemical composition is analyzed for the first time after 5min to 6min, and the alloy is added according to the target composition requirements, and carbon is added to promote the rapid melting and homogenization of the alloy and carbon powder; when the molten steel temperature reaches 1560°C to 1570°C, 1.5kg / t steel to 1.6kg / t steel of diffusion deoxidizer alumina balls are added for diffusion deoxidation, and the furnace door is closed for 10min to 13min; when the molten steel temperature reaches 1590°C to 1600°C, the chemical composition is analyzed for the second time to confirm that the content of each chemical element is within the target value requirement. The deviation value is taken away by the secondary sample. When the molten steel temperature reaches 1615℃~1625℃, the station is left. The LF smelting cycle is 55min~60min. The additional alloy addition per ton of steel is as follows: 0.9kg / t~1.1kg / t of ferrosilicon, 1.3kg / t~1.4kg / t of high carbon ferromanganese, 2.9kg / t~3.0kg / t of high carbon ferrochrome, 1.4kg / t~1.5kg / t of alumina balls, 0.5kg / t~0.6kg / t of aluminum segments, where the size of the aluminum segments is Φ10mm~Φ12mm; the additional auxiliary materials addition per ton of steel is as follows: 5kg / t~5.2kg / t of active lime with a particle size of 10mm~70mm, 1.4kg / t~1.5kg / t of silicon carbide with a particle size of 2mm~5mm, and 0.4kg / t~0.5kg / t of coke particles.

[0028] In S3 and RH vacuum refining, the molten steel treated by LF refining is hoisted into the RH vacuum furnace for refining.

[0029] In a specific embodiment, step S3 specifically includes: the station entry temperature is 1610°C to 1620°C, the operation time is 40min to 50min, and the vacuum pump is started when the argon pressure is controlled to be 0.1MPa to 0.3MPa, so that the molten steel is not exposed by micro-movement of the slag surface, and when the vacuum degree reaches 100Pa to 110Pa, the time is maintained for 10min to 15min, and the argon pressure is adjusted to 0.3MPa to 0.5MPa. The temperature after re-pressurization is 1580°C to 1590°C. After the static argon blowing is completed, 0.6kg / t steel to 0.7kg / t steel of the covering agent and 0.8m / t steel to 0.9m / t steel of the silicon-calcium alloy cored wire are added, wherein the size specification of the silicon-calcium alloy cored wire is Φ14mm to Φ14.2mm; the station exit temperature is 1560°C to 1570°C.

[0030] S4. During continuous casting, the molten steel after RH vacuum refining is continuously cast to obtain a continuous casting ingot.

[0031] In a specific embodiment, step S4 specifically includes: ladle casting temperature of 1520°C to 1530°C, molten steel volume of 95t to 105t, H content in the middle ladle ≤ 2ppm, full-process protective casting, and the crystallizer protective slag uses medium carbon steel protective slag.

[0032] S5. In the heating process, the billets produced in the continuous casting process are fed into the heating furnace, and the heating furnace temperature is 480℃~550℃; the temperature of the preheating section is 670℃~700℃, and the time is 1.4h~1.5h; the heating section includes heating section 1 with a temperature of 1195℃~1220℃, and the time is 1.4h~1.5h; heating section 2 with a temperature of 860℃~870℃, and the time is 1.4h~1.5h; the temperature of the soaking section is 1190℃~1210℃, and the time is 1.4h~1.5h; and the steel tapping temperature is 1180℃~1195℃.

[0033] S6. In the rolling process, the heated continuous casting billet is initially rolled and opened. The initial rolling adopts 9 rolling passes, four steel turnings, passes through 3 850mm rolling mills and 1 735mm rolling mill, and then enters the 8-frame continuous rolling unit for rolling; the steel is turned once before rolling 1 pass, the steel is turned for the second time after rolling 2 passes, the steel is turned for the third time after rolling 2 passes, and the steel is turned for the fourth time after rolling 4 passes; the width of the first pass is 408mm~408.1mm , height 421mm~421.1mm, reduction 65mm~65.1mm; 2nd pass width 426mm~426.1mm, height 351mm~351.1mm, reduction 70mm~70.1mm; 3rd pass width 370mm~370.1mm, height 362mm~362.1mm, reduction 64mm~64.1mm; 4th pass width 397mm~3 97.1mm, height 272mm~272.1mm, reduction 90mm~90.1mm; 5th pass width 285mm~285.1mm, height 355mm~355.1mm, reduction 42mm~42.1mm; 6th pass width 297mm~297.1mm, height 315mm~315.1mm, reduction 40mm~40.1mm; 7th pass width 3 07mm~307.1mm, height 280mm~280.1mm, reduction 35mm~35.1mm; the 8th pass width 317mm~317.1mm, height 246mm~246.1mm, reduction 34mm~34.1mm; the 9th pass width 271mm~271.1mm, height 235mm~235.1mm, reduction 82mm~82.1mm.

[0034] The continuous rolling product is rolled in 9 passes; the first pass is 229mm~229.1mm high and 245mm~245.1mm wide; the second pass is 192mm~192.1mm high and 235mm~235.1mm wide; the third pass is 200mm~200.1mm high and 195mm~195.1mm wide; the fourth pass is 173mm~173.1mm high and 210mm~210.1mm wide; the fifth pass is 180mm~180.1mm high and 170mm~180.1mm wide. 8.2mm~178.3mm; the 6th pass is 142mm~142.1mm high and 190mm~190.1mm wide; the 7th pass is 158mm~158.1mm high and 154.8mm~154.9mm wide; the 8th pass is 121mm~121.1mm high and 131.76mm~131.80mm wide; the 9th pass is 131.76mm~131.80mm high and 162.8mm~162.9mm wide; the finished product is produced after the 9th pass.

[0035] S7. In the insulation process, the bars prepared by the rolling process are insulated, the temperature of the lower insulation pit is ≥560°C, the insulation time is 52h~56h, and the exit temperature is ≤160°C.

[0036] S8, in the heat treatment, the steel material after heat preservation is heat treated, and the heat treatment includes the following steps:

[0037] (1) The steel after heat preservation is quenched at a heating temperature of 830°C to 850°C, heat preservation for 0.9h to 1.2h, and oil cooling;

[0038] (2) After quenching and cooling, the steel is tempered at a temperature of 540°C to 560°C, kept warm for 1.9h to 2.2h, and oil cooled.

[0039] The following are specific embodiments

[0040] Embodiment 1:

[0041] 1Chemical composition

[0042] The internal controlled chemical composition is determined to be C: 0.40%, Si: 0.25%, Mn: 1.04%, P: 0.012%, S: 0.005%, Cr: 1.03%, Ni: 0.05%, Mo: 0.02%, Cu: 0.04%, and the balance is iron and inevitable impurities.

[0043] 2. Production process of steel bars for mining machinery

[0044] Process route: ecological electric furnace + LF + RH + continuous casting billet → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery.

[0045] (1) Ecological electric furnace smelting

[0046] Scrap loading: 100% scrap steel smelting, including 111t heavy scrap steel and 10t lump scrap steel; tapping temperature 1634℃, C at tapping time 0.16%, P 0.008%, slag, pre-deoxidizer, alloy added when 1 / 4 of the steel is tapped, tapping volume 109t, smelting cycle 47min. Alloy addition per ton of steel: 6.1Kg / t silicon manganese, 7.1Kg / t high carbon ferromanganese, 14Kg / t high carbon ferrochrome, 1.1Kg / t aluminum wire segment (14mm). Auxiliary material addition per ton of steel: 45Kg / t active lime (40mm), 1.0Kg / t coke particles, 20Kg / t magnesite (35mm), 6Kg / t ladle ash.

[0047] (2) LF furnace refining

[0048] The LF station temperature is 1525℃, and the 35500A high current is used to heat and melt the slag. When the slag surface fluctuates and the molten steel and arc are not exposed, active lime is added. After 5 minutes, the chemical composition is analyzed for the first time. According to the target value of the chemical composition, alloy is added and carbon is added to promote the rapid melting and homogenization of the alloy and carbon powder. When the temperature of the molten steel reaches 1565℃, 1.5kg / t of diffusion deoxidizer alumina balls are added for diffusion deoxidation. The furnace door is closed for 12 minutes. When the temperature of the molten steel reaches 1595℃, the chemical composition is analyzed for the second time to confirm the deviation value of the content of each chemical element from the target value. After the second sample is taken away, the station is left when the temperature of the molten steel reaches 1618℃. The LF smelting cycle is 57 minutes. The amount of alloy added to each ton of steel is: 1.0kg / t of ferrosilicon, 1.3kg / t of high carbon ferromanganese, 2.9kg / t of high carbon ferrochrome, 1.4kg / t of alumina balls, and 0.5kg / t of aluminum wire segments (Φ10mm). The amount of supplementary materials added per ton of steel: active lime (35mm) 5Kg / t, silicon carbide (3mm) 1.4kg / t, coke particles 0.4kg / t.

[0049] (3) RH refining

[0050] The inlet temperature is 1616℃, the operation time is 45min, and the argon pressure is controlled at 0.1MPa before the vacuum pump is started, so that the slag surface moves slightly and the molten steel is not exposed. When the vacuum degree reaches 103Pa, the timing starts and the holding time is 12min. At the same time, the argon pressure is adjusted to 0.3MPa. The temperature after re-pressurization is 1587℃. After the static argon blowing is completed, 0.8m / t steel of silicon-calcium alloy cored wire (Φ14mm) and 0.6kg / t steel of covering agent are added. The outlet temperature is 1565℃.

[0051] (4) Continuous casting

[0052] The ladle casting temperature is 1528℃, the molten steel volume is 102t, the H content in the tundish is controlled at 1.5ppm, the whole process is protected casting, and the crystallizer protection slag uses medium carbon steel protection slag.

[0053] (5) Heating process: The temperature entering the heating furnace is 520℃, the temperature of the preheating section is required to be 680℃, and the time is 1.4h; the temperature of the heating section 2 is required to be 864℃, and the time is 1.4h; the temperature of the heating section 1 is required to be 1210℃, and the time is 1.4h; the temperature of the soaking section is required to be 1205℃, and the time is 1.5h; the steel tapping temperature is 1188℃.

[0054] (6) Rolling process

[0055] Continuous casting slab initial rolling process: rolling 9 times, turning steel → 1st pass width 408mm, height 421mm, reduction 65mm → 2nd pass width 426mm, height 351mm, reduction 70mm → turning steel → 3rd pass width 370mm, height 362mm, reduction 64mm → 4th pass width 397mm, height 272mm, reduction 90mm → turning steel → 5th pass width 285mm, height 355mm, reduction The steel is rolled at a width of 42mm, a height of 315mm and a reduction of 40mm in the 6th pass. The steel is rolled at a width of 307mm, a height of 280mm and a reduction of 35mm in the 7th pass. The steel is rolled at a width of 317mm, a height of 246mm and a reduction of 34mm in the 8th pass. The steel is turned over and the 9th pass is a width of 271mm, a height of 235mm and a reduction of 82mm. It passes through 3 850mm rolling mills and 1 735mm rolling mill and then enters the 8-stand continuous rolling mill for rolling.

[0056] Rolling process of the produced material: 9 passes, the 1st pass is 229mm high and 245mm wide; the 2nd pass is 192mm high and 235mm wide; the 3rd pass is 200mm high and 195mm wide; the 4th pass is 173mm high and 210mm wide; the 5th pass is 180mm high and 178.2mm wide; the 6th pass is 142mm high and 190mm wide; the 7th pass is 158mm high and 154.8mm wide; the 8th pass is 121mm high and 131.76mm wide; the 9th pass is 131.76mm high and 162.8mm wide; the finished product is produced after 9 passes.

[0057] (7) Insulation process: Steel insulation, lower insulation pit temperature 580℃, insulation 54h, exit pit temperature 150℃.

[0058] (8) Heat treatment process

[0059] The steel after insulation is heat treated, and the heat treatment includes the following steps:

[0060] 1) Quenching: 840℃, holding time 1.0h, oil cooling;

[0061] 2) Tempering: 550℃, keep warm for 2.0h, oil cooling.

[0062] Embodiment 2:

[0063] 1Chemical composition

[0064] The internal controlled chemical composition is determined to be C: 0.41%, Si: 0.25%, Mn: 1.00%, P: 0.011%, S: 0.004%, Cr: 1.02%, Ni: 0.05%, Mo: 0.02%, Cu: 0.05%, and the balance is iron and inevitable impurities.

[0065] 2. Production process of steel bars for mining machinery

[0066] Process route: ecological electric furnace + LF + RH + continuous casting billet → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery.

[0067] (1) Ecological electric furnace smelting

[0068] Scrap loading: 100% scrap steel smelting, including 110t heavy scrap steel and 10t lump scrap steel; tapping temperature 1634℃, C is 0.16% and P is 0.007% when tapping, slag, pre-deoxidizer and alloy are added when 1 / 4 of the steel is tapped, the tapping amount is 110t, and the smelting cycle is 47min. Alloy addition per ton of steel: 6.1Kg / t silicon manganese, 7.1Kg / t high carbon ferromanganese, 14Kg / t high carbon ferrochrome, 1.1Kg / t aluminum wire segment (12mm). Auxiliary material addition per ton of steel: 45Kg / t active lime (40mm), 1.0Kg / t coke particles, 20Kg / t magnesite (35mm), 6Kg / t ladle ash.

[0069] (2) LF furnace refining

[0070] The LF station temperature is 1525℃, and the 35600A high current is used to heat and melt the slag. When the slag surface fluctuates and the molten steel and arc are not exposed, active lime is added. After 5 minutes, the chemical composition is analyzed for the first time. The alloy is added according to the target value of the chemical composition, and carbon is added to promote the rapid melting and homogenization of the alloy and carbon powder. When the molten steel temperature reaches 1567℃, the diffusion deoxidizer alumina balls 1.5kg / t steel are added for diffusion deoxidation. The furnace door is closed for 12 minutes. When the molten steel temperature reaches 1596℃, the chemical composition is analyzed for the second time to confirm the deviation value of the content of each chemical element from the target value. After the second sample is taken away, the station is left when the molten steel temperature reaches 1620℃. The LF smelting cycle is 57 minutes. The alloys are added: ferrosilicon 0.9kg / t, high carbon ferromanganese 1.3kg / t, high carbon ferrochrome 2.9kg / t, alumina balls 1.4kg / t, aluminum wire segments (Φ10mm) 0.5kg / t. Supplementary materials: active lime (35mm) 5Kg / t, silicon carbide (3mm) 1.4kg / t, coke particles 0.4kg / t.

[0071] (3) RH refining

[0072] The inlet temperature is 1615℃, the operation time is 45min, and the argon pressure is controlled at 0.1MPa before the vacuum pump is started, so that the slag surface moves slightly and the molten steel is not exposed. When the vacuum degree reaches 104Pa, the timing starts and the holding time is 12min. At the same time, the argon pressure is adjusted to 0.3MPa. The temperature after re-pressurization is 1584℃. After the static argon blowing is completed, 0.8m / t steel of silicon-calcium alloy cored wire (Φ14mm) and 0.6kg / t steel of covering agent are added. The outlet temperature is 1567℃.

[0073] (4) Continuous casting

[0074] The ladle casting temperature is 1524℃, the molten steel volume is 101t, the H content in the tundish is controlled at 1.3ppm, the whole process is protected casting, and the crystallizer protection slag uses medium carbon steel protection slag.

[0075] (5) Heating process: The temperature entering the heating furnace is 510℃, the temperature of the preheating section is required to be 685℃, and the time is 1.4h; the temperature of the heating section 2 is required to be 865℃, and the time is 1.5h; the temperature of the heating section 1 is required to be 1208℃, and the time is 1.4h; the temperature of the soaking section is required to be 1196℃, and the time is 1.4h; the steel tapping temperature is 1190℃.

[0076] (6) Rolling process

[0077] Continuous casting slab initial rolling process: rolling 9 times, turning steel → 1st pass width 408mm, height 421mm, reduction 65mm → 2nd pass width 426mm, height 351mm, reduction 70mm → turning steel → 3rd pass width 370mm, height 362mm, reduction 64mm → 4th pass width 397mm, height 272mm, reduction 90mm → turning steel → 5th pass width 285mm, height 355mm, reduction The steel is rolled at a width of 42mm, a height of 315mm and a reduction of 40mm in the 6th pass. The steel is rolled at a width of 307mm, a height of 280mm and a reduction of 35mm in the 7th pass. The steel is rolled at a width of 317mm, a height of 246mm and a reduction of 34mm in the 8th pass. The steel is turned over and the 9th pass is a width of 271mm, a height of 235mm and a reduction of 82mm. It passes through 3 850mm rolling mills and 1 735mm rolling mill and then enters the 8-stand continuous rolling mill for rolling.

[0078] Rolling process of the produced material: 8 rolling passes, the 1st pass is 229mm high and 245mm wide; the 2nd pass is 192mm high and 235mm wide; the 3rd pass is 200mm high and 195mm wide; the 4th pass is 173mm high and 210mm wide; the 5th pass is 180mm high and 178.2mm wide; the 6th pass is 142mm high and 190mm wide; the 7th pass is 158mm high and 154.8mm wide; the 8th pass is 121mm high and 131.76mm wide; the 9th pass is 131.76mm high and 162.8mm wide; the finished product is produced after 9 passes.

[0079] (7) Insulation process: Steel insulation, lower insulation pit temperature 575℃, insulation 55h, exit pit temperature 120℃.

[0080] (8) Heat treatment process

[0081] The steel after insulation is heat treated, and the heat treatment includes the following steps:

[0082] 1) Quenching: 840℃, holding time 1.0h, oil cooling;

[0083] 2) Tempering: 550℃, keep warm for 2.0h, oil cooling.

[0084] Embodiment 3:

[0085] 1. Component optimization design

[0086] The internal control chemical composition is determined to be C: 0.40%, Si: 0.25%, Mn: 0.98%, P: 0.010%, S: 0.005%, Cr: 0.99%, Ni: 0.05%, Mo: 0.02%, Cu: 0.05%, and the balance is iron and inevitable impurities.

[0087] 2. Production process of steel bars for mining machinery

[0088] Process route: ecological electric furnace + LF + RH + continuous casting billet → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery.

[0089] (1) Ecological electric furnace smelting

[0090] Scrap loading: 100% scrap smelting, including 112t heavy scrap and 10t lump scrap; tapping temperature 1635℃, C is 0.16% and P is 0.008% when tapping, slag, pre-deoxidizer and alloy are added when 1 / 4 of the steel is tapped, the tapping amount is 110t, and the smelting cycle is 47min. Alloy addition per ton of steel: 6.1Kg / t silicon manganese, 7.1Kg / t high carbon ferromanganese, 14Kg / t high carbon ferrochrome, 1.1Kg / t aluminum wire segment (12mm). Auxiliary material addition per ton of steel: 45Kg / t active lime (40mm), 1.0Kg / t coke particles, 20Kg / t magnesite (35mm), 6Kg / t ladle ash.

[0091] (2) LF furnace refining

[0092] The LF station temperature is 1526℃, and the 35700A high current is used to heat and melt the slag. When the slag surface fluctuates and the molten steel and arc are not exposed, active lime is added. After 5 minutes, the chemical composition is analyzed for the first time. According to the target value of the chemical composition, alloy is added and carbon is added to promote the rapid melting and homogenization of the alloy and carbon powder. When the temperature of the molten steel reaches 1565℃, 1.5kg / t steel of alumina balls, a diffusion deoxidizer, is added for diffusion deoxidation. The furnace door is closed for 11 minutes. When the temperature of the molten steel reaches 1595℃, the chemical composition is analyzed for the second time to confirm the deviation value of the content of each chemical element from the target value. After the second sample is taken away, the station is left when the temperature of the molten steel reaches 1620℃. The LF smelting cycle is 57 minutes. The amount of alloy added to each ton of steel is: 1.0kg / t of ferrosilicon, 1.3kg / t of high carbon ferromanganese, 2.9kg / t of high carbon ferrochrome, 1.4kg / t of alumina balls, and 0.5kg / t of aluminum wire segments (Φ10mm). The amount of supplementary materials added per ton of steel: active lime (35mm) 5Kg / t, silicon carbide (3mm) 1.4kg / t, coke particles 0.4kg / t.

[0093] (3) RH refining

[0094] The inlet temperature is 1614℃, the operation time is 45min, and the argon pressure is controlled at 0.1MPa before the vacuum pump is started, so that the slag surface moves slightly and the molten steel is not exposed. When the vacuum degree reaches 102Pa, the timing starts and the holding time is 12min. At the same time, the argon pressure is adjusted to 0.3MPa. The temperature after re-pressurization is 1584℃. After the static argon blowing is completed, 0.8m / t steel of silicon-calcium alloy cored wire (Φ14mm) and 0.6kg / t steel of covering agent are added. The outlet temperature is 1565℃.

[0095] (4) Continuous casting

[0096] The ladle casting temperature is 1527℃, the molten steel volume is 99t, the H content in the tundish is controlled at 1.3ppm, the whole process is protected casting, and the crystallizer protection slag uses medium carbon steel protection slag.

[0097] (5) Heating process: The temperature entering the heating furnace is 510℃, the temperature of the preheating section is required to be 690℃, and the time is 1.4h; the temperature of the heating section 2 is required to be 865℃, and the time is 1.4h; the temperature of the heating section 1 is required to be 1210℃, and the time is 1.5h; the temperature of the soaking section is required to be 1196℃, and the time is 1.4h; the steel tapping temperature is 1192℃.

[0098] (6) Rolling process

[0099] Continuous casting slab initial rolling process: rolling 9 times, turning steel → 1st pass width 408mm, height 421mm, reduction 65mm → 2nd pass width 426mm, height 351mm, reduction 70mm → turning steel → 3rd pass width 370mm, height 362mm, reduction 64mm → 4th pass width 397mm, height 272mm, reduction 90mm → turning steel → 5th pass width 285mm, height 355mm, reduction The steel is rolled at a width of 42mm, a height of 315mm and a reduction of 40mm in the 6th pass. The steel is rolled at a width of 307mm, a height of 280mm and a reduction of 35mm in the 7th pass. The steel is rolled at a width of 317mm, a height of 246mm and a reduction of 34mm in the 8th pass. The steel is turned over and the 9th pass is a width of 271mm, a height of 235mm and a reduction of 82mm. It passes through 3 850mm rolling mills and 1 735mm rolling mill and then enters the 8-stand continuous rolling mill for rolling.

[0100] Rolling process of the produced material: 8 rolling passes, the 1st pass is 229mm high and 245mm wide; the 2nd pass is 192mm high and 235mm wide; the 3rd pass is 200mm high and 195mm wide; the 4th pass is 173mm high and 210mm wide; the 5th pass is 180mm high and 178.2mm wide; the 6th pass is 142mm high and 190mm wide; the 7th pass is 158mm high and 154.8mm wide; the 8th pass is 121mm high and 131.76mm wide; the 9th pass is 131.76mm high and 162.8mm wide; the finished product is produced after 9 passes.

[0101] (7) Insulation process: Steel insulation, lower insulation pit temperature 580℃, insulation 55h, exit pit temperature 140℃.

[0102] (8) Heat treatment process

[0103] The steel after insulation is heat treated, and the heat treatment includes the following steps:

[0104] 1) Quenching: 840℃, holding time 1.0h, oil cooling;

[0105] 2) Tempering: 550℃, keep warm for 2.0h, oil cooling.

[0106] Embodiment 4:

[0107] 1. Component optimization design

[0108] The internal controlled chemical composition is determined to be C: 0.41%, Si: 0.25%, Mn: 0.99%, P: 0.011%, S: 0.005%, Cr: 1.01%, Ni: 0.05%, Mo: 0.02%, Cu: 0.05%, and the balance is iron and unavoidable impurities.

[0109] 2. Production process of steel bars for mining machinery

[0110] Process route: ecological electric furnace + LF + RH + continuous casting billet → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery.

[0111] (1) Ecological electric furnace smelting

[0112] Scrap loading: 100% scrap steel smelting, including 112t heavy scrap steel and 10t lump scrap steel; tapping temperature 1635℃, C is 0.16% and P is 0.008% when tapping, slag, pre-deoxidizer and alloy are added when 1 / 4 of the steel is tapped, the tapping amount is 110t, and the smelting cycle is 46min. Alloy addition per ton of steel: 6.1Kg / t silicon manganese, 7.1Kg / t high carbon ferromanganese, 14Kg / t high carbon ferrochrome, 1.1Kg / t aluminum wire segment (12mm). Auxiliary material addition per ton of steel: 45Kg / t active lime (40mm), 1.0Kg / t coke particles, 20Kg / t magnesite (35mm), 6Kg / t ladle ash.

[0113] (2) LF furnace refining

[0114] The LF station temperature is 1526℃, and the 35400A high current is used to heat and melt the slag. When the slag surface fluctuates and the molten steel and arc are not exposed, active lime is added. After 5 minutes, the chemical composition is analyzed for the first time. According to the target value of the chemical composition, alloy is added and carbon is added to promote the rapid melting and homogenization of the alloy and carbon powder. When the temperature of the molten steel reaches 1565℃, 1.5kg / t steel of alumina balls, a diffusion deoxidizer, is added for diffusion deoxidation. The furnace door is closed for 11 minutes. When the temperature of the molten steel reaches 1596℃, the chemical composition is analyzed for the second time to confirm the deviation value of the content of each chemical element from the target value. After the second sample is taken away, the station is left when the temperature of the molten steel reaches 1619℃. The LF smelting cycle is 57 minutes. The amount of alloy added to each ton of steel is: 0.9kg / t of ferrosilicon, 1.3kg / t of high carbon ferromanganese, 2.9kg / t of high carbon ferrochrome, 1.4kg / t of alumina balls, and 0.5kg / t of aluminum wire segments (Φ10mm). The amount of supplementary materials added per ton of steel: active lime (35mm) 5Kg / t, silicon carbide (3mm) 1.4kg / t, coke particles 0.4kg / t.

[0115] (3) RH refining

[0116] The inlet temperature is 1615℃, the operation time is 45min, and the argon pressure is controlled at 0.1MPa before the vacuum pump is started, so that the slag surface moves slightly and the molten steel is not exposed. When the vacuum degree reaches 103Pa, the timing starts and the holding time is 12min. At the same time, the argon pressure is adjusted to 0.3MPa. The temperature after re-pressurization is 1586℃. After the static argon blowing is completed, 0.8m / t steel of silicon-calcium alloy cored wire (Φ14mm) and 0.6kg / t steel of covering agent are added. The outlet temperature is 1564℃.

[0117] (4) Continuous casting

[0118] The ladle casting temperature is 1526℃, the molten steel volume is 102t, the H content in the tundish is controlled at 1.5ppm, the whole process is protected casting, and the crystallizer protection slag uses medium carbon steel protection slag.

[0119] (5) Heating process: The temperature entering the heating furnace is 520℃, the temperature of the preheating section is required to be 680℃, and the time is 1.4h; the temperature of the heating section 2 is required to be 880℃, and the time is 1.5h; the temperature of the heating section 1 is required to be 1210℃, and the time is 1.4h; the temperature of the soaking section is required to be 1205℃, and the time is 1.4h; the steel tapping temperature is 1190℃.

[0120] (6) Rolling process

[0121] Continuous casting slab initial rolling process: rolling 9 times, turning steel → 1st pass width 408mm, height 421mm, reduction 65mm → 2nd pass width 426mm, height 351mm, reduction 70mm → turning steel → 3rd pass width 370mm, height 362mm, reduction 64mm → 4th pass width 397mm, height 272mm, reduction 90mm → turning steel → 5th pass width 285mm, height 355mm, reduction The steel is rolled at a width of 42mm, a height of 315mm and a reduction of 40mm in the 6th pass. The steel is rolled at a width of 307mm, a height of 280mm and a reduction of 35mm in the 7th pass. The steel is rolled at a width of 317mm, a height of 246mm and a reduction of 34mm in the 8th pass. The steel is turned over and the 9th pass is a width of 271mm, a height of 235mm and a reduction of 82mm. It passes through 3 850mm rolling mills and 1 735mm rolling mill and then enters the 8-stand continuous rolling mill for rolling.

[0122] Rolling process of the produced material: 8 rolling passes, the 1st pass is 229mm high and 245mm wide; the 2nd pass is 192mm high and 235mm wide; the 3rd pass is 200mm high and 195mm wide; the 4th pass is 173mm high and 210mm wide; the 5th pass is 180mm high and 178.2mm wide; the 6th pass is 142mm high and 190mm wide; the 7th pass is 158mm high and 154.8mm wide; the 8th pass is 121mm high and 131.76mm wide; the 9th pass is 131.76mm high and 162.8mm wide; the finished product is produced after 9 passes.

[0123] (7) Insulation process: Steel insulation, lower insulation pit temperature 590℃, insulation 54h, exit pit temperature 130℃.

[0124] (8) Heat treatment process

[0125] The steel after insulation is heat treated, and the heat treatment includes the following steps:

[0126] 1) Quenching: 840℃, holding time 1.0h, oil cooling;

[0127] 2) Tempering: 550℃, keep warm for 2.0h, oil cooling.

[0128] Embodiment 5:

[0129] 1. Component optimization design

[0130] The internal controlled chemical composition is determined to be C: 0.40%, Si: 0.25%, Mn: 1.01%, P: 0.010%, S: 0.005%, Cr: 1.02%, Ni: 0.05%, Mo: 0.02%, Cu: 0.05%, and the balance is iron and inevitable impurities.

[0131] 2. Production process of steel bars for mining machinery

[0132] Process route: ecological electric furnace + LF + RH + continuous casting billet → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery.

[0133] (1) Ecological electric furnace smelting

[0134] Scrap loading: 100% scrap steel smelting, including 112t heavy scrap steel and 10t lump scrap steel; tapping temperature 1635℃, C is 0.16% and P is 0.007% when tapping, slag, pre-deoxidizer and alloy are added when 1 / 4 of the steel is tapped, the tapping amount is 110t, and the smelting cycle is 47min. Alloy addition per ton of steel: 6.1Kg / t silicon manganese, 7.1Kg / t high carbon ferromanganese, 14Kg / t high carbon ferrochrome, 1.1Kg / t aluminum wire segment (12mm). Auxiliary material addition per ton of steel: 45Kg / t active lime (35mm), 1.0Kg / t coke particles, 20Kg / t magnesite (40mm), 6Kg / t ladle ash.

[0135] (2) LF furnace refining

[0136] The LF station temperature is 1526℃, and the 35600A high current is used to heat and melt the slag. When the slag surface fluctuates and the molten steel and arc are not exposed, active lime is added. After 5 minutes, the chemical composition is analyzed for the first time. The alloy is added according to the target value of the chemical composition, and carbon is added to promote the rapid melting and homogenization of the alloy and carbon powder. When the molten steel temperature reaches 1564℃, the diffusion deoxidizer alumina balls 1.5kg / t steel are added for diffusion deoxidation. The furnace door is closed for 11 minutes. When the molten steel temperature reaches 1595℃, the chemical composition is analyzed for the second time to confirm the deviation value of the content of each chemical element from the target value. After the second sample is taken away, the station is left when the molten steel temperature reaches 1618℃. The LF smelting cycle is 57 minutes. The amount of alloy added to each ton of steel is: ferrosilicon 0.9kg / t, high carbon ferromanganese 1.3kg / t, high carbon ferrochrome 2.9kg / t, alumina balls 1.4kg / t, aluminum wire segment (Φ10mm) 0.5kg / t. The amount of supplementary materials added per ton of steel: active lime (35mm) 5Kg / t, silicon carbide (3mm) 1.4kg / t, coke particles 0.4kg / t.

[0137] (3) RH refining

[0138] The inlet temperature is 1614℃, the operation time is 45min, and the argon pressure is controlled at 0.1MPa before the vacuum pump is started, so that the slag surface moves slightly and the molten steel is not exposed. When the vacuum degree reaches 105Pa, the timing starts and the holding time is 12min. At the same time, the argon pressure is adjusted to 0.3MPa. The temperature after re-pressurization is 1585℃. After the static argon blowing is completed, 0.8m / t steel of silicon-calcium alloy cored wire (Φ14mm) and 0.6kg / t steel of covering agent are added. The outlet temperature is 1565℃.

[0139] (4) Continuous casting

[0140] The ladle casting temperature is 1525℃, the molten steel volume is 102t, the H content in the tundish is controlled at 1.4ppm, the whole process is protected casting, and the crystallizer protection slag uses medium carbon steel protection slag.

[0141] (5) Heating process: The temperature entering the heating furnace is 510℃, the temperature of the preheating section is required to be 690℃, and the time is 1.4h; the temperature of the heating section 2 is required to be 865℃, and the time is 1.4h; the temperature of the heating section 1 is required to be 1210℃, and the time is 1.4h; the temperature of the soaking section is required to be 1205℃, and the time is 1.4h; the steel tapping temperature is 1190℃.

[0142] (6) Rolling process

[0143] Continuous casting slab initial rolling process: rolling 9 times, turning steel → 1st pass width 408mm, height 421mm, reduction 65mm → 2nd pass width 426mm, height 351mm, reduction 70mm → turning steel → 3rd pass width 370mm, height 362mm, reduction 64mm → 4th pass width 397mm, height 272mm, reduction 90mm → turning steel → 5th pass width 285mm, height 355mm, reduction The steel is rolled at a width of 42mm, a height of 315mm and a reduction of 40mm in the 6th pass. The steel is rolled at a width of 307mm, a height of 280mm and a reduction of 35mm in the 7th pass. The steel is rolled at a width of 317mm, a height of 246mm and a reduction of 34mm in the 8th pass. The steel is turned over and the 9th pass is a width of 271mm, a height of 235mm and a reduction of 82mm. It passes through 3 850mm rolling mills and 1 735mm rolling mill and then enters the 8-stand continuous rolling mill for rolling.

[0144] Rolling process of the produced material: 8 rolling passes, the 1st pass is 229mm high and 245mm wide; the 2nd pass is 192mm high and 235mm wide; the 3rd pass is 200mm high and 195mm wide; the 4th pass is 173mm high and 210mm wide; the 5th pass is 180mm high and 178.2mm wide; the 6th pass is 142mm high and 190mm wide; the 7th pass is 158mm high and 154.8mm wide; the 8th pass is 121mm high and 131.76mm wide; the 9th pass is 131.76mm high and 162.8mm wide; the finished product is produced after 9 passes.

[0145] (7) Insulation process: Steel insulation, lower insulation pit temperature 580℃, insulation 54h, exit pit temperature 130℃.

[0146] (8) Heat treatment process

[0147] The steel after insulation is heat treated, and the heat treatment includes the following steps:

[0148] 1) Quenching: 840℃, holding time 1.0h, oil cooling;

[0149] 2) Tempering: 550℃, keep warm for 2.0h, oil cooling.

[0150] 2. Finished product inspection results

[0151] (1) Φ130mm specification macrostructure, see the table below:

[0152] Table 1 Performance test results of Examples 1-5

[0153] Serial number Generally loose Loose center Ingot segregation General spot segregation Edge spot segregation standard ≤1.5 ≤1.5 ≤1.5 ≤1.0 ≤1.0 Example 1 0.5 0.5 0.5 0 0 Example 1 0.5 0.5 0.5 0 0 Example 2 0.5 0.5 0.5 0 0 Example 2 0.5 0.5 0.5 0 0 Example 3 0.5 0.5 0.5 0 0 Example 3 0.5 0.5 0.5 0 0 Example 4 0.5 0.5 0.5 0 0 Example 4 0.5 0.5 0.5 0 0 Example 5 0.5 0.5 0.5 0 0 Example 5 0.5 0.5 0.5 0 0

[0154] (2) Φ130mm non-metallic inclusions, see the table below:

[0155]

[0156]

[0157] (3) Mechanical properties of Φ130mm specification, see the table below:

[0158] Serial number Quenching / ℃ Tempering / ℃ Rm / MPa Rel / MPa A / ％ z / ％ Impact / KU2 (vertical) standard 840, oil cooling 550, oil-cooled ≥980 ≥835 ≥9 ≥45 ≥47 Example 1 840, oil cooling 550, oil-cooled 1143 886 15 65 65 Example 1 840, oil cooling 550, oil-cooled 1138 890 17 67 68 Example 2 840, oil cooling 550, oil-cooled 1134 876 16 60 64 Example 2 840, oil cooling 550, oil-cooled 1137 880 16 67 59 Example 3 840, oil cooling 550, oil-cooled 1129 855 18 65 64 Example 3 840, oil cooling 550, oil-cooled 1130 860 17 64 66 Example 4 840, oil cooling 550, oil-cooled 1142 878 15 67 64 Example 4 840, oil cooling 550, oil-cooled 1128 890 15 64 65 Example 5 840, oil cooling 550, oil-cooled 1140 869 17 63 67 Example 5 840, oil cooling 550, oil-cooled 1137 878 16 67 64

[0159] According to the above table, Examples 1-5 use "100t ECOARC ecological electric furnace + LF + RH + 390mm*480mm smelting process and rolling process" to produce steel bars for mining machinery, which meets high-end use requirements and achieves a breakthrough in the batch production of steel bars for mining machinery by the ecological electric furnace continuous casting process, which not only ensures the mechanical properties and high steel purity of the finished steel bars for mining machinery, but also ensures the surface quality level of the steel bars for mining machinery.

[0160] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A steel bar for mining machinery, characterized in that: The following components are included in mass percentage: C: 0.38% to 0.43%, Si: 0.22% to 0.35%, Mn: 0.95% to 1.10%, P≤0.015%, S≤0.010%, Cr: 0.95% to 1.10%, Ni≤0.25%, Mo≤0.05%, Cu≤0.15%, and the balance is iron and unavoidable impurities.

2. A method for preparing a steel bar for mining machinery according to claim 1, characterized in that: The following steps are involved: Ecological electric furnace smelting, LF refining, RH vacuum refining, continuous casting, heating process, rolling process and insulation process; In the ecological electric furnace smelting, scrap steel is used as the furnace charge, and the scrap steel accounts for 100% by mass; the final composition of the electric furnace is: C: 0.15% to 0.18%, P ≤ 0.010%; deoxidation and alloying are performed during the steel tapping process; In the LF refining, the molten steel discharged from the ecological electric furnace is put into the LF furnace for refining treatment; During the RH vacuum refining, the molten steel treated by the LF refining is hoisted into the RH vacuum furnace for refining; During the continuous casting, the molten steel after the RH vacuum refining treatment is continuously cast to obtain a continuously cast ingot, and the continuously cast ingot is sent to a heating furnace for heating, and then rolled and kept warm in sequence to obtain the steel bar for mining machinery.

3. The preparation method according to claim 2, characterized in that: In the ecological electric furnace smelting, the scrap steel includes heavy scrap steel and lump-type scrap steel; wherein the mass percentage of heavy scrap steel in the charge is 80% to 95%; the tapping temperature is 1630°C to 1640°C; slag, pre-deoxidizer and alloy are added when 1 / 4 to 1 / 3 of the steel is tapped, and the smelting cycle is 45min to 50min; the amount of alloy added per ton of steel: 6.1Kg / t to 6.2Kg / t of silicon manganese, 7.1Kg / t to 7.2Kg / t of high carbon ferromanganese, 14Kg / t to 14.2Kg / t of high carbon Ferrochrome, 1.1Kg / t to 1.2Kg / t of aluminum segments, wherein the size of the aluminum segments is Φ10mm to Φ16mm; auxiliary materials added per ton of steel: 45Kg / t to 46Kg / t of active lime, 1.0Kg / t to 1.1Kg / t of coke particles, 20Kg / t to 21Kg / t of magnesite, 6Kg / t to 6.2Kg / t of ladle ash; wherein the particle size of the active lime is 10mm to 70mm; the particle size of the magnesite is 10mm to 60mm.

4. The preparation method according to claim 2, characterized in that: In the LF refining, the LF inlet temperature is 1520°C to 1530°C, and after heating and melting the slag with a large current of 35000A to 36000A, when the slag surface fluctuates and the molten steel and the arc are not exposed, 4.5Kg / t steel to 5.5Kg / t steel of active lime is added, and the first sampling and analysis is performed after 5min to 6min, and the molten steel component content is adjusted according to the target component requirements; when the molten steel temperature reaches 1560°C to 1570°C, 1.5kg / t steel to 1.6kg / t steel of diffusion deoxidizer alumina balls are added for diffusion deoxidation, and the furnace door is closed for 10min to 13min; when the molten steel temperature reaches 1590°C to 1600°C, the second sampling and analysis is performed; when the molten steel temperature reaches 1615°C to 1625°C, the station is left, The LF smelting cycle is 55min to 60min, and the amount of additional alloy added per ton of steel is: 0.9kg / t to 1.1kg / t of ferrosilicon, 1.3kg / t to 1.4kg / t of high carbon ferromanganese, 2.9kg / t to 3.0kg / t of high carbon ferrochrome, 1.4kg / t to 1.5kg / t of alumina balls, 0.5kg / t to 0.6kg / t of aluminum segments, wherein the size of the aluminum segments is Φ10mm to Φ12mm; the amount of additional auxiliary materials added per ton of steel is: 5kg / t to 5.2kg / t of active lime with a particle size of 10mm to 70mm, 1.4kg / t to 1.5kg / t of silicon carbide with a particle size of 2mm to 5mm, and 0.4kg / t to 0.5kg / t of coke particles.

5. The preparation method according to claim 2, characterized in that: In the RH vacuum refining, the inlet temperature is 1610°C to 1620°C, the operation time is 40min to 50min, the vacuum pump is started when the argon pressure is controlled to be 0.1MPa to 0.3MPa, and when the vacuum degree reaches 100Pa to 110Pa, the time is maintained for 10min to 15min, and the argon pressure is adjusted to 0.3MPa to 0.5MPa. The temperature after re-pressurization is 1580°C to 1590°C. After the static argon blowing is completed, 0.6kg / t steel to 0.7kg / t steel covering agent and 0.8m / t steel to 0.9m / t steel silicon-calcium alloy cored wire are added, wherein the size specification of the silicon-calcium alloy cored wire is Φ14mm to Φ14.2mm; the outlet temperature is 1560°C to 1570°C.

6. The preparation method according to claim 2, characterized in that: In the continuous casting, the ladle casting temperature is 1520° C. to 1530° C., the molten steel volume is 95t to 105t, the H content in the middle ladle is ≤2ppm, the whole process is protected casting, and the crystallizer protection slag uses medium carbon steel protection slag.

7. The preparation method according to claim 2, characterized in that: In the heating process, the square billets produced in the continuous casting process are fed into a heating furnace, the temperature of the heating furnace is 480°C to 550°C; the temperature of the preheating section is 670°C to 700°C, and the time is 1.4h to 1.5h; the heating section includes a heating section 1 with a temperature of 1195°C to 1220°C, and a time of 1.4h to 1.5h; a heating section 2 with a temperature of 860°C to 870°C, and a time of 1.4h to 1.5h; a soaking section with a temperature of 1190°C to 1210°C, and a time of 1.4h to 1.5h; and a tapping temperature of 1180°C to 1195°C.

8. The preparation method according to claim 2, characterized in that: In the rolling process, the heated continuous casting billet is initially rolled to form a billet, and the initial rolling adopts 9 rolling passes to form a billet, and the steel is turned four times, and then passes through 3 850mm rolling mills and 1 735mm rolling mill, and then enters 8 continuous rolling mills for rolling; the steel is turned once before rolling 1 pass, the steel is turned for the second time after rolling 2 passes, the steel is turned for the third time after rolling 2 passes, and the steel is turned for the fourth time after rolling 4 passes; the width of the first pass is 408mm-408.1mm , height 421mm~421.1mm, reduction 65mm~65.1mm; 2nd pass width 426mm~426.1mm, height 351mm~351.1mm, reduction 70mm~70.1mm; 3rd pass width 370mm~370.1mm, height 362mm~362.1mm, reduction 64mm~64.1mm; 4th pass width 397mm~3 97.1mm, height 272mm~272.1mm, reduction 90mm~90.1mm; 5th pass width 285mm~285.1mm, height 355mm~355.1mm, reduction 42mm~42.1mm; 6th pass width 297mm~297.1mm, height 315mm~315.1mm, reduction 40mm~40.1mm; 7th pass width 3 07mm~307.1mm, height 280mm~280.1mm, reduction 35mm~35.1mm; the 8th pass width 317mm~317.1mm, height 246mm~246.1mm, reduction 34mm~34.1mm; the 9th pass width 271mm~271.1mm, height 235mm~235.1mm, reduction 82mm~82.1mm.

9. The preparation method according to claim 2, characterized in that: In the rolling process, the continuous rolling product is rolled for 9 passes; the first pass is 229mm-229.1mm high and 245mm-245.1mm wide; the second pass is 192mm-192.1mm high and 235mm-235.1mm wide; the third pass is 200mm-200.1mm high and 195mm-195.1mm wide; the fourth pass is 173mm-173.1mm high and 210mm-210.1mm wide; the fifth pass is 180mm-180.1mm high, Width: 178.2mm~178.3mm; The 6th pass: height: 142mm~142.1mm, width: 190mm~190.1mm; The 7th pass: height: 158mm~158.1mm, width: 154.8mm~154.9mm; The 8th pass: height: 121mm~121.1mm, width: 131.76mm~131.80mm; The 9th pass: height: 131.76mm~131.80mm, width: 162.8mm~162.9mm; The finished product is produced after the 9th pass.

10. The preparation method according to claim 2, characterized in that: In the insulation process, the bar prepared by the rolling process is insulated, the lower insulation pit temperature is ≥560°C, the insulation is 52h-56h, and the exit temperature is ≤160°C; the steel after insulation is heat treated, and the heat treatment includes the following steps: (1) The steel after heat preservation is quenched at a heating temperature of 830°C to 850°C, heat preservation for 0.9h to 1.2h, and oil cooling; (2) After quenching and cooling, the steel is tempered at a temperature of 540°C to 560°C, kept warm for 1.9h to 2.2h, and oil cooled.

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