Steel bar for mining machinery and preparation method therefor

Abstract

Disclosed in the present invention are a steel bar for mining machinery and a preparation method therefor. The steel bar for mining machinery comprises the following components, in percentages by mass: 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 being iron and inevitable impurities. In the present invention, the steel bar for mining machinery is produced by means of the processes of eco-electric furnace smelting + LF + RH + continuous casting and rolling, and meets the requirements for high-end use. This process achieves a breakthrough in the mass production of the steel bar for mining machinery by using the process of eco-electric furnace continuous casting, ensuring properties such as mechanical properties and high steel purity of the finished steel bar for mining machinery, and also ensuring the surface quality level of the steel bar for mining machinery.

Description

Steel bar for mine machinery and preparation method thereof TECHNICAL FIELD

[0001] The present application relates to the field of materials and metallurgy, and more particularly to a steel bar for mine machinery and a preparation method thereof. BACKGROUND

[0002] Mine machinery is machinery directly used for mineral exploitation and enrichment operations, serving important basic industrial sectors such as black and non-ferrous metallurgy, coal, building materials, chemical industry, nuclear industry, and playing a very important role in most operation processes, even a safety guarantee role. The quality of the steel for mine machinery directly affects the service life and wear resistance of the mine machinery, and even relates to the safety of the entire vehicle operation process.

[0003] At present, the steel for mine machinery has the problems of many impurities, poor wear resistance, low fatigue life, and difficult to meet the application requirements of mechanical properties.

[0004] SUMMARY

[0005] The present application aims to overcome the above-mentioned defects in the prior art, and provides a steel bar for mine machinery and a preparation method thereof. The steel bar for mine machinery produced by the ecological electric furnace smelting + LF + RH + continuous casting and rolling process meets the high-end use requirements, realizes the breakthrough of ecological electric furnace continuous casting process for batch production of steel bars for mine machinery, ensures the mechanical properties and high steel purity of the finished steel bar for mine machinery, and ensures the surface quality level of the steel bar for mine machinery, meeting the quality requirements of the steel bar for mine machinery.

[0006] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0007] A steel bar for mine machinery, comprising the following components 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 being iron and unavoidable impurities.

[0008] The present application also discloses a preparation method of the steel bar for mine 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.

[0009] In the ecological electric furnace smelting, scrap steel is used as the furnace charge, and the scrap steel accounts for 100% in mass fraction; the electric furnace end composition is: C: 0.15% to 0.18%, P≤0.010%; deoxidation alloying is performed during the tapping process;

[0010] In the LF refining, the molten steel after tapping in the ecological electric furnace smelting is put into the LF furnace for refining treatment;

[0011] In the RH vacuum refining, the molten steel after the LF refining treatment is put into the RH vacuum furnace for refining treatment;

[0012] In the continuous casting, the molten steel after the RH vacuum refining treatment is continuously cast to obtain a continuous casting billet, and the continuous casting billet is sent into a heating furnace for heating, and then sequentially undergoes rolling and heat preservation to obtain the steel bar for mine machinery.

[0013] The embodiment of the present application has the following beneficial effects:

[0014] (1) The steel bar for mine machinery is produced by using a 100t ECOARC ecological electric furnace+LF+RH+390mm*480mm smelting process and rolling process, the production specification is Φ130mm, the mechanical properties meet the requirements, and the purity of the steel is ensured.

[0015] (2) The reasonable component design and production process ensure the surface quality and mechanical properties.

[0016] (3) The macrostructure and non-metallic inclusions of the finished steel meet the requirements of high-end products. DETAILED DESCRIPTION

[0017] The present application will be further described below in combination with specific embodiments, but the present application is not limited in any way by the embodiments.

[0018] I. Chemical composition

[0019] The present application discloses a steel bar for mine machinery, which comprises the following components by 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 unavoidable impurities.

[0020] II. Production process technology

[0021] The preparation method of the steel bar for mine machinery of the present application comprises the following steps: ecological electric furnace smelting, LF refining, RH vacuum refining, continuous casting, heating process, rolling process and heat preservation process.

[0022] Further, the method specifically comprises the following steps:

[0023] S1, in the ecological electric furnace smelting, scrap steel is used as the furnace charge, and the scrap steel accounts for 100% by mass fraction; the end point composition of the electric furnace: C: 0.15% to 0.18%, P≤0.010%; deoxidation and alloying is performed in the tapping process.

[0024] In a specific embodiment, step S1 specifically comprises: the scrap steel comprises heavy scrap steel and bale-type scrap steel; wherein the mass percentage of the heavy scrap steel in the furnace charge is 80% to 95%; the tapping temperature is 1630°C to 1640°C; slag material, pre-deoxidizing agent and alloy are added when 1 / 4 to 1 / 3 of the tapping is completed, the tapping amount is 108t to 112t, and the smelting cycle is 45min to 50min; the alloy addition amount per ton of steel is: 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, and 1.1Kg / t to 1.2Kg / t of aluminum wire segments; the auxiliary material addition amount per ton of steel is: 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, and 6Kg / t to 6.2Kg / t of ladle dust.

[0025] In a specific embodiment, the size specification of the aluminum wire segments is Φ10mm to Φ16mm; the particle size of the active lime is 10mm to 70mm; and the particle size of the magnesite is 10mm to 60mm.

[0026] In a specific embodiment, 100% scrap steel smelting is performed, wherein the heavy scrap steel is 110t to 113t, and the bale-type scrap steel is 10t to 11t.

[0027] S2, in the LF refining, the molten steel after tapping in the ecological electric furnace smelting is put into an LF furnace for refining treatment.

[0028] In a specific embodiment, step S2 specifically comprises: the LF inlet temperature is 1520-1530℃, after using 35000A-36000A large current to heat and slag, when the slag surface fluctuates, the molten steel and the arc are not exposed, 4.5-5.5 Kg / t steel of active lime is added, after 5-6 min, the first sampling analysis chemical composition is performed, the alloy is added according to the target composition requirement, and the carbon is increased to promote the rapid melting and homogenization of the alloy and the carbon powder; when the molten steel temperature reaches 1560-1570℃, 1.5-1.6 Kg / t steel of diffusion deoxidizer alumina ball is added for diffusion deoxidation, and the furnace door is closed for 10-13 min; when the molten steel temperature reaches 1590-1600℃, the second sampling analysis chemical composition is performed to confirm the deviation of the chemical element composition content from the target value requirement, after the second sampling is taken away, when the molten steel temperature reaches 1615-1625℃, the LF smelting cycle is 55-60 min, the alloy addition amount per ton of steel is: 0.9-1.1 Kg / t of ferrosilicon, 1.3-1.4 Kg / t of high-carbon ferromanganese, 2.9-3.0 Kg / t of high-carbon ferrochrome, 1.4-1.5 Kg / t of alumina ball, and 0.5-0.6 Kg / t of aluminum wire segment, wherein the size specification of the aluminum wire segment is Φ10-Φ12 mm; the auxiliary material addition amount per ton of steel is: 5-5.2 Kg / t of active lime with a particle size of 10-70 mm, 1.4-1.5 Kg / t of silicon carbide with a particle size of 2-5 mm, and 0.4-0.5 Kg / t of coke particles.

[0029] S3, in the RH vacuum refining, the molten steel treated by the LF refining is hoisted into the RH vacuum furnace for refining treatment.

[0030] In a specific embodiment, step S3 specifically comprises: the inlet temperature is 1610-1620℃, the operation time is 40-50 min, the argon pressure is controlled to 0.1-0.3 MPa, the vacuum pump is started, the slag surface is slightly moved, and the molten steel is not exposed, when the vacuum degree reaches 100-110 Pa, the holding time is 10-15 min, the argon pressure is adjusted to 0.3-0.5 MPa at the same time, the temperature after re-pressurization is 1580-1590℃, after the static argon blowing is completed, 0.6-0.7 Kg / t steel of covering agent and 0.8-0.9 Kg / t steel of silicon-calcium alloy cored wire are added, wherein the size specification of the silicon-calcium alloy cored wire is Φ14-Φ14.2 mm; the outlet temperature is 1560-1570℃.

[0031] S4, in the continuous casting, the molten steel treated by the RH vacuum refining is continuously cast to obtain a continuous casting billet.

[0032] In a specific embodiment, step S4 specifically comprises: ladle casting temperature 1520-1530℃, molten steel amount 95-105t, tundish H content ≤2ppm, whole process protective casting, and crystallizer protective slag using medium carbon steel protective slag.

[0033] In the heating process, the billet discharged from the continuous casting process is sent into a heating furnace, the temperature of the heating furnace is 480-550℃; the temperature of the preheating section is 670-700℃, and the time is 1.4-1.5h; the heating section includes heating section 1 with a temperature of 1195-1220℃ and a time of 1.4-1.5h; heating section 2 with a temperature of 860-870℃ and a time of 1.4-1.5h; the soaking section with a temperature of 1190-1210℃ and a time of 1.4-1.5h; and the temperature of the discharged steel is 1180-1195℃.

[0034] In the rolling process, the heated continuous casting billet is initially rolled and opened, the initial rolling adopts 9-pass rolling and opening, four times of steel turning, passes through 3 sets of 850mm rolling mills, 1 set of 735mm rolling mill, and then enters 8 sets of continuous rolling mill groups; once steel turning before 1-pass rolling, second steel turning after 2-pass rolling, third steel turning after 2-pass rolling, and fourth steel turning after 4-pass rolling; the width of the 1st pass is 408-408.1mm, the height is 421-421.1mm, and the reduction is 65-65.1mm; the width of the 2nd pass is 426-426.1mm, the height is 351-351.1mm, and the reduction is 70-70.1mm; the width of the 3rd pass is 370-370.1mm, the height is 362-362.1mm, and the reduction is 64-64.1mm; the width of the 4th pass is 397-397.1mm, the height is 272-272.1mm, and the reduction is 90-90.1mm; the width of the 5th pass is 285-285.1mm, the height is 355-355.1mm, and the reduction is 42-42.1mm; the width of the 6th pass is 297-297.1mm, the height is 315-315.1mm, and the reduction is 40-40.1mm; the width of the 7th pass is 307-307.1mm, the height is 280-280.1mm, and the reduction is 35-35.1mm; the width of the 8th pass is 317-317.1mm, the height is 246-246.1mm, and the reduction is 34-34.1mm; and the width of the 9th pass is 271-271.1mm, the height is 235-235.1mm, and the reduction is 82-82.1mm.

[0035] The continuous rolling produces the rolled material 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 178.2mm-178.3mm wide; the sixth pass is 142mm-142.1mm high and 190mm-190.1mm wide; the seventh pass is 158mm-158.1mm high and 154.8mm-154.9mm wide; the eighth pass is 121mm-121.1mm high and 131.76mm-131.80mm wide; the ninth pass is 131.76mm-131.80mm high and 162.8mm-162.9mm wide; the finished product is obtained after the ninth pass.

[0036] S7, in the heat preservation process, the bar prepared by the rolling process is heat preserved, the temperature of the lower heat preservation pit is ≥560℃, the heat preservation time is 52h-56h, and the pit exit temperature is ≤160℃.

[0037] S8, in the heat treatment, the heat preserved steel is heat treated, and the heat treatment comprises the following steps:

[0038] (1) the heat preserved steel is quenched, the heating temperature is 830℃-850℃, the heat preservation time is 0.9h-1.2h, and the oil cooling is performed;

[0039] (2) the quenched steel is tempered, the tempering temperature is 540℃-560℃, the heat preservation time is 1.9h-2.2h, and the oil cooling is performed.

[0040] The following is a specific embodiment

[0041] Embodiment 1:

[0042] 1 Chemical composition

[0043] The internal control chemical composition 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 of iron and inevitable impurities is determined.

[0044] 2 Steel bar production process for mining machinery

[0045] Process route: ecological electric furnace + LF + RH + continuous casting billet → heating furnace heating → rolling → heat preservation → finishing → inspection → packaging and delivery to the warehouse → delivery.

[0046] (1) ecological electric furnace smelting

[0047] Charge: 100% scrap smelting, including heavy scrap 111 t, bale scrap 10 t; tapping temperature 1634°C, C 0.16%, P 0.008% at tapping, slag, pre-deoxidizer, alloy added at 1 / 4 tapping, tapping amount 109 t, smelting cycle 47 min. Alloy addition per ton of steel: silicon-manganese 6.1 kg / t, high-carbon ferromanganese 7.1 kg / t, high-carbon ferrochrome 14 kg / t, aluminum wire segment (14 mm) 1.1 kg / t. Auxiliary material addition per ton of steel: active lime (40 mm) 45 kg / t, coke particles 1.0 kg / t, magnesite (35 mm) 20 kg / t, ladle powder 6 kg / t.

[0048] (2) LF refining

[0049] LF entry temperature 1525°C, 35500 A large current to heat slag, when the slag surface fluctuates, the molten steel and the electric arc are not exposed, active lime is added, the first sampling analysis of chemical composition is taken after 5 min, 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 1565°C, 1.5 kg / t of steel of diffusion deoxidizer alumina balls is added for diffusion deoxidation, the furnace door is closed for 12 min, and when the molten steel temperature reaches 1595°C, the second sampling analysis of chemical composition is taken to confirm the deviation of each chemical element composition from the target value. After the second sampling is taken away, when the molten steel temperature reaches 1618°C, the LF refining cycle is 57 min, and the alloy addition per ton of steel is: ferrosilicon 1.0 kg / t, high-carbon ferromanganese 1.3 kg / t, high-carbon ferrochrome 2.9 kg / t, alumina balls 1.4 kg / t, aluminum wire segment (Φ10 mm) 0.5 kg / t. Auxiliary material addition per ton of steel: active lime (35 mm) 5 kg / t, silicon carbide (3 mm) 1.4 kg / t, coke particles 0.4 kg / t.

[0050] (3) RH refining

[0051] Entry temperature 1616°C, operation time 45 min, argon pressure controlled at 0.1 MPa before the vacuum pump is started, the molten steel is not exposed with the slag surface slightly moving, the timing is started when the vacuum degree reaches 103 Pa, the holding time is 12 min, and the argon pressure is adjusted to 0.3 MPa at the same time. After the re-pressurization, the temperature is 1587°C, after the end of the argon blowing, the silicon-calcium alloy cored wire (Φ14 mm) 0.8 m / t steel is added, the covering agent 0.6 kg / t steel, and the exit temperature is 1565°C.

[0052] (4) Continuous casting

[0053] Ladle pouring temperature 1528°C, molten steel amount 102 t, tundish H control 1.5 ppm, whole process protective casting, mold powder medium carbon steel powder is used.

[0054] (5) Heating process: the temperature of the inlet of the heating furnace is 520°C, the temperature of the preheating section is required to be 680°C, the time is 1.4h; the temperature of heating section 2 is required to be 864°C, the time is 1.4h; the temperature of heating section 1 is required to be 1210°C, the time is 1.4h; the temperature of the soaking section is required to be 1205°C, the time is 1.5h; the temperature of the outlet is 1188°C.

[0055] (6) Rolling process

[0056] Continuous casting billet roughing process: 9 passes, turn over the steel → the first pass width 408mm, height 421mm, reduction 65mm → the second pass width 426mm, height 351mm, reduction 70mm → turn over the steel → the third pass width 370mm, height 362mm, reduction 64mm → the fourth pass width 397mm, height 272mm, reduction 90mm → turn over the steel → the fifth pass width 285mm, height 355mm, reduction 42mm → the sixth pass width 297mm, height 315mm, reduction 40mm → the seventh pass width 307mm, height 280mm, reduction 35mm → the eighth pass width 317mm, height 246mm, reduction 34mm → turn over the steel → the ninth pass width 271mm, height 235mm, reduction 82mm, through 3 sets of 850mm rolling mill, 1 set of 735mm rolling mill, and then enter 8 sets of continuous rolling mill group.

[0057] Product rolling process: 9 passes, the first pass height 229mm, width 245mm; the second pass height 192mm, width 235mm; the third pass height 200mm, width 195mm; the fourth pass height 173mm, width 210mm; the fifth pass height 180mm, width 178.2mm; the sixth pass height 142mm, width 190mm; the seventh pass height 158mm, width 154.8mm; the eighth pass height 121mm, width 131.76mm; the ninth pass height 131.76mm, width 162.8mm; after 9 passes, the finished product is discharged.

[0058] (7) Holding process: the steel is held, the temperature of the lower holding pit is 580°C, the holding time is 54h, and the temperature of the outlet is 150°C.

[0059] (8) Heat treatment process

[0060] The steel after holding is subjected to heat treatment, which comprises the following steps:

[0061] 1) Quenching: 840°C, holding for 1.0h, oil cooling;

[0062] 2) Tempering: 550°C, holding for 2.0h, oil cooling.

[0063] Example 2:

[0064] 1Chemical composition

[0065] The internal control chemical composition 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 of iron and inevitable impurities were determined.

[0066] 2Production process of steel bar for mining machinery

[0067] Process route: ecological electric furnace + LF + RH + continuous casting billet → heating furnace heating → rolling → heat preservation → finishing → inspection → packaging and delivery to the warehouse → delivery.

[0068] (1) Ecological electric furnace smelting

[0069] Scrap charging amount: 100% scrap smelting, among which heavy scrap 110t, bale type scrap 10t; tapping temperature 1634℃, C 0.16% at tapping, P 0.007% at tapping, slag, pre-deoxidizer, and alloy were added at 1 / 4 of tapping, tapping amount 110t, smelting period 47min. Alloy addition amount per ton of steel: silicon manganese 6.1Kg / t, high-carbon ferromanganese 7.1Kg / t, high-carbon ferrochrome 14Kg / t, aluminum wire segment (12mm) 1.1Kg / t. Auxiliary material addition amount per ton of steel: active lime (40mm) 45Kg / t, coke particles 1.0Kg / t, magnesite (35mm) 20Kg / t, ladle ash 6Kg / t.

[0070] (2) LF furnace refining

[0071] LF inlet temperature 1525℃, 35600A large current to heat and slag, when the slag surface fluctuates, the molten steel and the electric arc are not exposed, active lime is supplemented, the first sampling analysis of chemical composition is taken after 5min, alloy is supplemented according to the target value of chemical composition, and carbon is increased to promote the rapid melting and homogenization of alloy and carbon powder. When the molten steel temperature reaches 1567℃, 1.5kg / t of steel of diffusion deoxidizer alumina ball is added for diffusion deoxidization, the furnace door is closed for 12min, when the molten steel temperature reaches 1596℃, the second sampling analysis of chemical composition is taken to confirm the deviation of each chemical element content from the target value, after the second sampling is taken away, when the molten steel temperature reaches 1620℃, the LF smelting period is 57min, the supplemented alloy: ferrosilicon 0.9kg / t, high-carbon ferromanganese 1.3kg / t, high-carbon ferrochrome 2.9kg / t, alumina ball 1.4kg / t, aluminum wire segment (Φ10mm) 0.5kg / t. Supplementary auxiliary materials: active lime (35mm) 5Kg / t, silicon carbide (3mm) 1.4kg / t, coke particles 0.4kg / t.

[0072] (3) RH refining

[0073] Inlet temperature 1615℃, operation time 45min, argon pressure control 0.1MPa before vacuum pump starting, with slag surface micro-movement molten steel not exposed, when vacuum degree reaches 104Pa, start timing, holding time 12min, at the same time, adjust argon pressure to 0.3MPa, after re-pressurizing, temperature 1584℃, after static argon blowing, add silicon-calcium alloy cored wire (Φ14mm) 0.8m / t steel, covering agent 0.6kg / t steel, outlet temperature 1567℃.

[0074] (4) Continuous casting

[0075] Ladle pouring temperature 1524℃, molten steel quantity 101t, tundish H control 1.3ppm, whole process protection pouring, mold powder using medium carbon steel mold powder.

[0076] (5) Heating process: inlet heating furnace temperature 510℃, preheating section temperature requirement 685℃, time 1.4h; heating 2 section temperature requirement 865℃, time 1.5h; heating 1 section temperature requirement 1208℃, time 1.4h; soaking section temperature requirement 1196℃, time 1.4h; outlet temperature 1190℃.

[0077] (6) Rolling process

[0078] Continuous casting billet initial rolling and cogging process: rolling 9 passes, turning over→1st pass wide 408mm, high 421mm, reduction 65mm→2nd pass wide 426mm, high 351mm, reduction 70mm→turning over→3rd pass wide 370mm, high 362mm, reduction 64mm→4th pass wide 397mm, high 272mm, reduction 90mm→turning over→5th pass wide 285mm, high 355mm, reduction 42mm→6th pass wide 297mm, high 315mm, reduction 40mm→7th pass wide 307mm, high 280mm, reduction 35mm→8th pass wide 317mm, high 246mm, reduction 34mm→turning over→9th pass wide 271mm, high 235mm, reduction 82mm, through 3 sets of 850mm rolling mill, 1 set of 735mm rolling mill, then enter 8 sets of continuous rolling mill group rolling.

[0079] Finished product rolling process: rolling 8 passes, 1st pass high 229mm, wide 245mm; 2nd pass high 192mm, wide 235mm; 3rd pass high 200mm, wide 195mm; 4th pass high 173mm, wide 210mm; 5th pass high 180mm, wide 178.2mm; 6th pass high 142mm, wide 190mm; 7th pass high 158mm, wide 154.8mm; 8th pass high 121mm, wide 131.76mm; 9th pass high 131.76mm, wide 162.8mm; after 9 passes, outlet finished product.

[0080] (7) Holding process: holding of steel, holding pit temperature 575°C, holding for 55h, pit exit temperature 120°C.

[0081] (8) Heat treatment process

[0082] The steel after holding is subjected to heat treatment, which includes the following steps:

[0083] 1) Quenching: 840°C, holding for 1.0h, oil cooling;

[0084] 2) Tempering: 550°C, holding for 2.0h, oil cooling.

[0085] Example 3:

[0086] 1 Component optimization design

[0087] The internal control chemical composition 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 of iron and inevitable impurities are determined.

[0088] 2 Mine machinery steel bar production process

[0089] Process route: ecological electric furnace + LF + RH + continuous casting billet → heating furnace heating → rolling → holding → finishing → inspection → packaging and delivery to the warehouse → delivery.

[0090] (1) Ecological electric furnace smelting

[0091] Scrap charging amount: 100% scrap smelting, among which heavy scrap 112t, bale type scrap 10t; tapping temperature 1635°C, C at tapping 0.16%, P 0.008%, slag, pre-deoxidizer, alloy are added at 1 / 4 tapping, tapping amount 110t, smelting cycle 47min. Alloy addition amount per ton of steel: silicon manganese 6.1Kg / t, high carbon ferromanganese 7.1Kg / t, high carbon ferrochrome 14Kg / t, aluminum wire segment (12mm) 1.1Kg / t. Auxiliary material addition amount per ton of steel: active lime (40mm) 45Kg / t, coke particles 1.0Kg / t, magnesite (35mm) 20Kg / t, ladle dust 6Kg / t.

[0092] (2) LF furnace refining

[0093] LF entry temperature 1526℃, 35700A large current temperature slag, when the slag surface fluctuation, molten steel and arc not exposed, add active lime, 5 min after the first sampling analysis of chemical composition, according to the chemical composition of the target value of alloying, and carbon, to promote alloy and carbon powder rapid melting and homogenization. When the molten steel temperature reaches 1565℃, add diffusion deoxidizer alumina ball 1.5kg / t steel for diffusion deoxidation, closed door 11 min, when the molten steel temperature reaches 1595℃, second sampling analysis of chemical composition, to confirm the deviation of each chemical element composition from the target value, after the second sample, when the molten steel temperature reaches 1620℃, off station, LF smelting cycle 57 min, the amount of alloying per ton of steel: silicon iron 1.0kg / t, high carbon ferromanganese 1.3kg / t, high carbon chromium iron 2.9kg / t, alumina ball 1.4kg / t, aluminum wire segment (Φ10mm) 0.5kg / t. The amount of auxiliary material per ton of steel: active lime (35mm) 5Kg / t, silicon carbide (3mm) 1.4kg / t, coke particles 0.4kg / t.

[0094] (3) RH refining

[0095] Entry temperature 1614℃, operation time 45min, before the vacuum pump starts, argon pressure control 0.1MPa, with slag surface micro motion molten steel not exposed, when the vacuum degree reaches 102Pa, start timing, holding time 12min, at the same time, adjust the argon pressure to 0.3MPa, after re-pressing, temperature 1584℃, after static argon blowing, add silicon calcium alloy cored wire (Φ14mm) 0.8m / t steel, covering agent 0.6kg / t steel, exit temperature 1565℃.

[0096] (4) Continuous casting

[0097] ladle pouring temperature 1527℃, molten steel 99t, tundish H control 1.3ppm, whole process protection casting, mold protection slag using medium carbon steel protection slag.

[0098] (5) Heating process: entry heating furnace temperature 510℃, preheating temperature requirement 690℃, time 1.4h; heating 2 temperature requirement 865℃, time 1.4h; heating 1 temperature requirement 1210℃, time 1.5h; soaking temperature requirement 1196℃, time 1.4h; exit temperature 1192℃.

[0099] (6) Rolling process

[0100] Continuous casting billet roughing process: 9 passes, turn over the steel → the first pass wide 408 mm, high 421 mm, reduction 65 mm → the second pass wide 426 mm, high 351 mm, reduction 70 mm → turn over the steel → the third pass wide 370 mm, high 362 mm, reduction 64 mm → the fourth pass wide 397 mm, high 272 mm, reduction 90 mm → turn over the steel → the fifth pass wide 285 mm, high 355 mm, reduction 42 mm → the sixth pass wide 297 mm, high 315 mm, reduction 40 mm → the seventh pass wide 307 mm, high 280 mm, reduction 35 mm → the eighth pass wide 317 mm, high 246 mm, reduction 34 mm → turn over the steel → the ninth pass wide 271 mm, high 235 mm, reduction 82 mm, through 3 850 mm rolling mill, 1 735 mm rolling mill, and then enter 8 continuous rolling mill group rolling.

[0101] Product rolling process: 8 passes, the first pass high 229 mm, wide 245 mm; the second pass high 192 mm, wide 235 mm; the third pass high 200 mm, wide 195 mm; the fourth pass high 173 mm, wide 210 mm; the fifth pass high 180 mm, wide 178.2 mm; the sixth pass high 142 mm, wide 190 mm; the seventh pass high 158 mm, wide 154.8 mm; the eighth pass high 121 mm, wide 131.76 mm; the ninth pass high 131.76 mm, wide 162.8 mm; after 9 passes, the finished product is out.

[0102] (7) Holding process: the steel is held, the temperature of the holding pit is 580 ℃, the holding time is 55 h, and the temperature out of the pit is 140 ℃.

[0103] (8) Heat treatment process

[0104] The steel after holding is subjected to heat treatment, and the heat treatment includes the following steps:

[0105] 1) Quenching: 840 ℃, holding for 1.0 h, oil cooling;

[0106] 2) Tempering: 550 ℃, holding for 2.0 h, oil cooling.

[0107] Example 4:

[0108] 1 Component optimization design

[0109] The internal control chemical composition 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 inevitable impurities.

[0110] 2 Mine machinery steel bar production process

[0111] Process route: ecological electric furnace + LF + RH + continuous casting billet → heating furnace heating → rolling → holding → finishing → inspection → packaging and delivery to the warehouse → delivery.

[0112] (1) Ecological electric furnace smelting

[0113] Scrap loading: 100% scrap smelting, including heavy scrap 112 t, bale scrap 10 t; tapping temperature 1635℃, C 0.16% and P 0.008% at tapping, slag, pre-deoxidizer and alloy are added at 1 / 4 tapping, tapping amount 110 t, smelting cycle 46 min. Alloy addition per ton of steel: silicon manganese 6.1 Kg / t, high-carbon ferromanganese 7.1 Kg / t, high-carbon ferrochrome 14 Kg / t, aluminum wire segment (12 mm) 1.1 Kg / t. Auxiliary material addition per ton of steel: active lime (40 mm) 45 Kg / t, coke particles 1.0 Kg / t, magnesite (35 mm) 20 Kg / t, ladle dust 6 Kg / t.

[0114] (2) LF furnace refining

[0115] LF inlet temperature 1526℃, 35400A large current to heat and slag, when the slag surface fluctuates, the molten steel and the electric arc are not exposed, active lime is added, the first sampling and chemical composition analysis is taken after 5 min, alloy is added according to the target value of chemical composition, and carbon is added to promote the rapid melting and homogenization of alloy and carbon powder. When the molten steel temperature reaches 1565℃, 1.5 kg / t of steel of diffusion deoxidizer alumina ball is added for diffusion deoxidation, the furnace door is closed for 11 min, when the molten steel temperature reaches 1596℃, the second sampling and chemical composition analysis is taken to confirm the deviation of each chemical element content from the target value, after the second sampling is taken away, when the molten steel temperature reaches 1619℃, the LF smelting cycle is 57 min, alloy addition per ton of steel: ferrosilicon 0.9 kg / t, high-carbon ferromanganese 1.3 kg / t, high-carbon ferrochrome 2.9 kg / t, alumina ball 1.4 kg / t, aluminum wire segment (Φ10 mm) 0.5 kg / t. Auxiliary material addition per ton of steel: active lime (35 mm) 5 Kg / t, silicon carbide (3 mm) 1.4 kg / t, coke particles 0.4 kg / t.

[0116] (3) RH refining

[0117] Inlet temperature 1615℃, operation time 45 min, argon pressure control 0.1 MPa before vacuum pump starts, with the slag surface slightly moving the molten steel not exposed, when the vacuum degree reaches 103 Pa, the timing starts, the holding time is 12 min, at the same time the argon pressure is adjusted to 0.3 MPa, after the re-pressing the temperature is 1586℃, after the end of the argon blowing, 0.8 meters / t of steel of silicon-calcium alloy cored wire (Φ14 mm) is added, 0.6 kg / t of steel of covering agent is added, outlet temperature 1564℃.

[0118] (4) Continuous casting

[0119] The ladle casting temperature was 1526°C, the molten steel amount was 102t, the tundish H control was 1.5ppm, the whole process was protected casting, and the crystallizer protecting slag used a medium carbon steel protecting slag.

[0120] (5) Heating process: the temperature entering the heating furnace was 520°C, the temperature required in the preheating section was 680°C, and the time was 1.4h; the temperature required in the heating 2 section was 880°C, and the time was 1.5h; the temperature required in the heating 1 section was 1210°C, and the time was 1.4h; the temperature required in the soaking section was 1205°C, and the time was 1.4h; and the temperature of the molten steel was 1190°C.

[0121] (6) Rolling process

[0122] The continuous casting billet initial rolling and cogging process was as follows: rolling 9 passes, turning over→the first pass width 408mm, height 421mm, reduction 65mm→the second pass width 426mm, height 351mm, reduction 70mm→turning over→the third pass width 370mm, height 362mm, reduction 64mm→the fourth pass width 397mm, height 272mm, reduction 90mm→turning over→the fifth pass width 285mm, height 355mm, reduction 42mm→the sixth pass width 297mm, height 315mm, reduction 40mm→the seventh pass width 307mm, height 280mm, reduction 35mm→the eighth pass width 317mm, height 246mm, reduction 34mm→turning over→the ninth pass width 271mm, height 235mm, reduction 82mm, passing through 3 850mm rolling mills, 1 735mm rolling mill, and then entering 8 continuous rolling mill groups for rolling.

[0123] The product rolling process was as follows: rolling 8 passes, the first pass height 229mm, width 245mm; the second pass height 192mm, width 235mm; the third pass height 200mm, width 195mm; the fourth pass height 173mm, width 210mm; the fifth pass height 180mm, width 178.2mm; the sixth pass height 142mm, width 190mm; the seventh pass height 158mm, width 154.8mm; the eighth pass height 121mm, width 131.76mm; the ninth pass height 131.76mm, width 162.8mm; and the finished product was discharged after 9 passes.

[0124] (7) Holding process: the steel was held, the temperature in the holding pit was 590°C, the holding time was 54h, and the pit discharge temperature was 130°C.

[0125] (8) Heat treatment process

[0126] The steel after holding was heat treated, and the heat treatment included the following steps:

[0127] 1) Quenching: 840°C, holding for 1.0 h, oil cooling;

[0128] 2) Tempering: 550°C, holding for 2.0 h, oil cooling.

[0129] Example 5:

[0130] 1 Component optimization design

[0131] The internal control chemical composition 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 of iron and inevitable impurities are determined.

[0132] 2 Mine machinery steel bar production process

[0133] Process route: ecological electric furnace + LF + RH + continuous casting billet → heating furnace heating → rolling → holding → finishing → inspection → packaging and depositing in the library → delivery.

[0134] (1) Ecological electric furnace smelting

[0135] Scrap charging amount: 100% scrap smelting, among which heavy scrap steel 112t, bale type scrap steel 10t; tapping temperature 1635℃, C 0.16% at tapping, P 0.007% at tapping, slag, pre-deoxidizer, alloy are added at 1 / 4 tapping, tapping amount 110t, smelting cycle 47min. Alloy addition per ton of steel: silicon manganese 6.1Kg / t, high carbon ferromanganese 7.1Kg / t, high carbon ferrochrome 14Kg / t, aluminum wire segment (12mm) 1.1Kg / t. Auxiliary material addition per ton of steel: active lime (35mm) 45Kg / t, coke particles 1.0Kg / t, magnesite (40mm) 20Kg / t, ladle ash 6Kg / t.

[0136] (2) LF furnace refining

[0137] LF entry temperature 1526℃, 35600A large current temperature slag, when the slag surface fluctuation, molten steel and arc not exposed, add active lime, 5 min after the first sampling analysis of chemical composition, according to the chemical composition of the target value of alloying, and carbon, to promote alloy and carbon powder rapid melting and homogenization. When the molten steel temperature reaches 1564℃, add diffusion deoxidizer alumina ball 1.5kg / t steel for diffusion deoxidation, closed door 11 min, when the molten steel temperature reaches 1595℃, second sampling analysis of chemical composition, to confirm the deviation of each chemical element composition from the target value, after the second sample, when the molten steel temperature reaches 1618℃, off station, LF smelting cycle 57 min, the amount of alloying per ton of steel: silicon iron 0.9kg / t, high carbon ferromanganese 1.3kg / t, high carbon chromium iron 2.9kg / t, alumina ball 1.4kg / t, aluminum wire segment (Φ10mm) 0.5kg / t. The amount of auxiliary material per ton of steel: active lime (35mm) 5Kg / t, silicon carbide (3mm) 1.4kg / t, coke particles 0.4kg / t.

[0138] (3) RH refining

[0139] Entry temperature 1614℃, operation time 45min, before the vacuum pump starts, argon pressure control 0.1MPa, with slag surface micro motion molten steel not exposed, when the vacuum degree reaches 105Pa, start timing, holding time 12min, at the same time, adjust the argon pressure to 0.3MPa, after re-pressing, temperature 1585℃, after static argon blowing, add silicon calcium alloy cored wire (Φ14mm) 0.8m / t steel, covering agent 0.6kg / t steel, exit temperature 1565℃.

[0140] (4) Continuous casting

[0141] Ladle pouring temperature 1525℃, molten steel 102t, tundish H control 1.4ppm, whole process protection casting, mold powder using medium carbon steel powder.

[0142] (5) Heating process: entry heating furnace temperature 510℃, preheating temperature requirement 690℃, time 1.4h; heating 2 temperature requirement 865℃, time 1.4h; heating 1 temperature requirement 1210℃, time 1.4h; soaking temperature requirement 1205℃, time 1.4h; exit temperature 1190℃.

[0143] (6) Rolling process

[0144] Continuous casting billet roughing and blooming process: 9 passes, turn over the steel → the first pass width 408 mm, height 421 mm, reduction 65 mm → the second pass width 426 mm, height 351 mm, reduction 70 mm → turn over the steel → the third pass width 370 mm, height 362 mm, reduction 64 mm → the fourth pass width 397 mm, height 272 mm, reduction 90 mm → turn over the steel → the fifth pass width 285 mm, height 355 mm, reduction 42 mm → the sixth pass width 297 mm, height 315 mm, reduction 40 mm → the seventh pass width 307 mm, height 280 mm, reduction 35 mm → the eighth pass width 317 mm, height 246 mm, reduction 34 mm → turn over the steel → the ninth pass width 271 mm, height 235 mm, reduction 82 mm, through 3 850 mm rolling mills, 1 735 mm rolling mill, and then enter 8 continuous rolling mill groups to roll.

[0145] Finished product rolling process: 8 passes, the first pass height 229 mm, width 245 mm; the second pass height 192 mm, width 235 mm; the third pass height 200 mm, width 195 mm; the fourth pass height 173 mm, width 210 mm; the fifth pass height 180 mm, width 178.2 mm; the sixth pass height 142 mm, width 190 mm; the seventh pass height 158 mm, width 154.8 mm; the eighth pass height 121 mm, width 131.76 mm; the ninth pass height 131.76 mm, width 162.8 mm; after 9 passes, the finished product is discharged.

[0146] (7) Holding process: the steel is held, the temperature of the holding pit is 580℃, the holding time is 54 h, and the temperature of the pit is 130℃.

[0147] (8) Heat treatment process

[0148] The steel after holding is subjected to heat treatment, and the heat treatment comprises the following steps:

[0149] 1) Quenching: 840℃, holding for 1.0 h, oil cooling;

[0150] 2) Tempering: 550℃, holding for 2.0 h, oil cooling.

[0151] 2, finished product inspection results

[0152] (1) Low magnification structure of Φ130 mm specification, see the following table:

[0153] Table 1 Performance test results of examples 1-5

[0154] (2) Non-metallic inclusions of Φ130 mm specification, see the following table:

[0155] (3) The mechanical properties of Φ130mm specification are shown in the following table:

[0156] According to the above table, the steel bars for mine machinery produced by the "100t ECOARC ecological electric furnace + LF + RH + 390mm*480mm smelting process and rolling process" in Examples 1-5 meet the high-end use requirements, realizes the breakthrough of the ecological electric furnace continuous casting process in batch production of steel bars for mine machinery, and guarantees the mechanical properties and high steel purity of the finished steel bars for mine machinery, and guarantees the surface quality level of the steel bars for mine machinery.

[0157] The above-described examples only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the application. It should be pointed out that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A steel bar for a mining machine, characterized by, Comprise the following components by mass 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 of iron and inevitable impurities.

2. A method of producing a steel bar for a mining machine as claimed in claim 1, characterized by, Comprise the following steps: ecological electric furnace smelting, LF refining, RH vacuum refining, continuous casting, heating process, rolling process and heat preservation process; In the ecological electric furnace smelting, scrap steel is used as the furnace charge, and the scrap steel accounts for 100% by mass fraction; the end-point composition of the electric furnace: C: 0.15%~0.18%, P≤0.010%; deoxidation alloying is carried out during tapping; In the LF refining, the molten steel after tapping in the ecological electric furnace smelting is put into the LF furnace for refining treatment; In the RH vacuum refining, the molten steel after the LF refining treatment is hoisted into the RH vacuum furnace for refining treatment; In the continuous casting, the molten steel after the RH vacuum refining treatment is continuously cast to obtain a continuous casting billet, and the continuous casting billet is sent into a heating furnace for heating, and then sequentially undergoes rolling and heat preservation to obtain the steel bar for mine 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 bale-type scrap steel; wherein the mass percentage of heavy scrap steel in the furnace charge is 80%~95%; the tapping temperature is 1630℃~1640℃; slag, pre-deoxidizer and alloy are added at 1 / 4~1 / 3 of the tapping time, and the smelting period is 45min~50min; the alloy addition amount per ton of steel is: 6.1Kg / t~6.2Kg / t of silicon manganese, 7.1Kg / t~7.2Kg / t of high-carbon ferromanganese, 14Kg / t~14.2Kg / t of high-carbon ferrochrome, and 1.1Kg / t~1.2Kg / t of aluminum wire segments, wherein the size specification of the aluminum wire segments is Φ10mm~Φ16mm; the auxiliary material addition amount per ton of steel is: 45Kg / t~46Kg / t of active lime, 1.0Kg / t~1.1Kg / t of coke particles, 20Kg / t~21Kg / t of magnesite, and 6Kg / t~6.2Kg / t of ladle dust; wherein the particle size of the active lime is 10mm~70mm; the particle size of the magnesite is 10mm~60mm.

4. The preparation method according to claim 2, characterized in that, In the LF refining, the LF inlet temperature is 1520-1530 DEG C, after the slag is heated by 35000A-36000A large current, when the slag surface fluctuates, the molten steel and the arc are not exposed, 4.5-5.5 Kg / t steel active lime is added, after 5-6 min, the first sampling analysis is carried out, the molten steel component content is adjusted according to the target component requirement; when the molten steel temperature reaches 1560-1570 DEG C, 1.5-1.6 Kg / t steel diffusion deoxidizer alumina ball is added for diffusion deoxidation, the furnace door is closed for 10-13 min; when the molten steel temperature reaches 1590-1600 DEG C, the second sampling analysis is carried out; when the molten steel temperature reaches 1615-1625 DEG C, the LF refining cycle is 55-60 min, the alloy addition amount per ton of steel is 0.9-1.1 Kg / t silicon iron, 1.3-1.4 Kg / t high-carbon ferromanganese, 2.9-3.0 Kg / t high-carbon ferrochrome, 1.4-1.5 Kg / t alumina ball, 0.5-0.6 Kg / t aluminum wire segment, wherein the size specification of the aluminum wire segment is Φ10-Φ12 mm; the auxiliary material addition amount per ton of steel is 5-5.2 Kg / t active lime with a particle size of 10-70 mm, 1.4-1.5 Kg / t silicon carbide with a particle size of 2-5 mm, 0.4-0.5 Kg / t coke particles.

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

6. The preparation method according to claim 2, characterized in that, In the continuous casting, the ladle casting temperature is 1520-1530 DEG C, the molten steel amount is 95-105 t, the tundish H content is ≤2 ppm, the whole process is protected casting, and the crystallizer protective slag is medium-carbon steel protective slag.

7. The preparation method according to claim 2, characterized in that, In the heating process, the square billet offline in the continuous casting process is sent into a heating furnace, the heating furnace temperature is 480-550 DEG C; the preheating section temperature is 670-700 DEG C, and the time is 1.4-1.5 h; the heating section includes heating section 1 temperature 1195-1220 DEG C, time 1.4-1.5 h; heating section 2 temperature 860-870 DEG C, time 1.4-1.5 h; the soaking section temperature is 1190-1210 DEG C, and the time is 1.4-1.5 h; the casting temperature is 1180-1195 DEG C.

8. The preparation method according to claim 2, characterized in that, In the rolling process, the heated continuous casting billet is roughed and opened, the roughing adopts 9-pass rolling and opening, four times of turning, passes through 3 850mm rolling mills, 1 735mm rolling mill, and then enters 8 continuous rolling mill groups; once turning after 1-pass rolling, second turning after 2-pass rolling, third turning after 2-pass rolling, and fourth turning after 4-pass rolling; the first-pass width is 408mm-408.1mm, the height is 421mm-421.1mm, and the reduction is 65mm-65.1mm; the second-pass width is 426mm-426.1mm, the height is 351mm-351.1mm, and the reduction is 70mm-70.1mm; the third-pass width is 370mm-370.1mm, the height is 362mm-362.1mm, and the reduction is 64mm-64.1mm; the fourth-pass width is 397mm-397.1mm, the height is 272mm-272.1mm, and the reduction is 90mm-90.1mm; the fifth-pass width is 285mm-285.1mm, the height is 355mm-355.1mm, and the reduction is 42mm-42.1mm; the sixth-pass width is 297mm-297.1mm, the height is 315mm-315.1mm, and the reduction is 40mm-40.1mm; the seventh-pass width is 307mm-307.1mm, the height is 280mm-280.1mm, and the reduction is 35mm-35.1mm; the eighth-pass width is 317mm-317.1mm, the height is 246mm-246.1mm, and the reduction is 34mm-34.1mm; and the ninth-pass width is 271mm-271.1mm, the height is 235mm-235.1mm, and the reduction is 82mm-82.1mm.

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

10. The method of claim 2, wherein, In the heat preservation process, the rod prepared by the rolling process is preserved, the temperature of the lower preservation pit is ≥560℃, the preservation time is 52h-56h, and the pit exit temperature is ≤160℃; the heat treated steel after preservation comprises the following steps: (1) the steel material after the heat preservation is quenched, the heating temperature is 830-850℃, the heat preservation time is 0.9-1.2h, and oil cooling is conducted; (2) the steel material after the quenching is tempered, the tempering temperature is 540-560℃, the heat preservation time is 1.9-2.2h, and oil cooling is conducted.

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