A steel bar for automotive drive shaft based on ecological electric furnace and a production method thereof

Abstract

The present application relates to a kind of ecological electric furnace based automobile drive shaft steel bar and production method, the chemical composition of automobile drive shaft steel bar is C:0.18%~0.22%, Si:0.22%~0.33%, Mn:0.85%~1.00%, P≤0.015%, S≤0.005%, Cr:1.05%~1.20%, Ni≤0.25%, Mo≤0.10%, Ti:0.05%~0.09%, Cu≤0.15%;The rest is Fe and impurity.Processing includes ecological electric furnace smelting, LF refining, RH refining, continuous casting, billet heating, rolling, heat preservation and heat treatment;The present application adopts the smelting continuous casting process of "ecological electric furnace+LF+RH+continuous casting", cooperates with appropriate rolling process, produces a kind of automobile drive shaft steel bar with high steel purity, has excellent mechanical properties and surface quality, can satisfy the requirement of high-end product.

Description

Technical Field

[0001] This invention relates to the field of bar production technology, and in particular to a steel bar for automotive drive shafts based on an eco-friendly electric furnace and its production method. Background Technology

[0002] The driveshaft is a crucial component in a car's transmission system, primarily responsible for transmitting power generated by the engine to the vehicle's drive wheels. The quality of the steel used in the driveshaft directly affects the safety of power transmission during vehicle operation. Therefore, the requirements for the steel used in automotive driveshafts are extremely high in terms of high temperature resistance, wear resistance, mechanical properties, fatigue life, and steel purity to ensure the safety of the vehicle during driving.

[0003] An eco-friendly electric arc furnace (also known as an eco-friendly electric furnace) is a high-efficiency electric arc furnace that employs advanced energy recovery and environmental protection technologies. It features high airtightness and prevents air from seeping into the scrap preheating chamber and furnace body. The eco-friendly electric furnace consists of a melting furnace and a preheating chamber. High-temperature waste gas is used to preheat the scrap steel, which is then loaded into a vertical preheating chamber connected to the furnace shell. By utilizing the CO gas contained in the waste gas, the eco-friendly electric furnace requires only a small amount of fuel to smelt steel, avoiding the generation of harmful chemical substances. Furthermore, the eco-friendly electric furnace can achieve different production processes using only scrap steel or a 0-60% proportion of molten iron. Raw materials are not limited by shape or size; it can utilize economical lightweight scrap steel for all-scrap steel smelting or increase the proportion of molten iron to develop high-purity steel.

[0004] Chinese patent application CN 116837291 A discloses a method for producing steel bars for automotive axle sleeves using an eco-friendly electric furnace. The chemical composition of the bars, by mass percentage, is: C: 0.18%–0.23%, Si: 0.20%–0.35%, Mn: 0.42%–0.60%, P: ≤0.015%, S: ≤0.010%, Cr: 0.82%–1.00%, Ni: ≤0.25%, Mo: 0.41%–0.53%, Cu: ≤0.15%, with the balance being iron and unavoidable impurities. The method employs an eco-friendly electric furnace smelting process → LF refining → RH refining → continuous casting → heating → rolling, achieving a breakthrough in the mass production of steel bars for automotive axle sleeves using an eco-friendly electric furnace continuous casting process.

[0005] This application develops a steel bar for automotive drive shafts with excellent mechanical properties and high steel purity, aiming to meet the requirements of high-end products. Summary of the Invention

[0006] This invention provides a steel bar for automotive drive shafts based on an eco-friendly electric furnace and its production method. It adopts a smelting and continuous casting process of "eco-friendly electric furnace + LF + RH + continuous casting" and a suitable rolling process to produce a steel bar for automotive drive shafts with high steel purity, excellent mechanical properties and surface quality. It can meet the requirements of high-end products and achieves a breakthrough in the mass production of steel bars for automotive drive shafts using the eco-friendly electric furnace continuous casting process.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] A steel bar for automotive drive shafts based on an eco-friendly electric furnace. The chemical composition of the steel bar for automotive drive shafts, by mass percentage, is: C: 0.18%–0.22%, Si: 0.22%–0.33%, Mn: 0.85%–1.00%, P≤0.015%, S≤0.005%, Cr: 1.05%–1.20%, Ni≤0.25%, Mo≤0.10%, Ti: 0.05%–0.09%, Cu≤0.15%; the remainder is Fe and unavoidable impurities.

[0009] Furthermore, the finished product properties of the steel bars for automotive drive shafts are as follows: tensile strength Rm≥1080MPa, yield strength Rel≥850MPa, elongation A≥10%, reduction of area z≥45%, and room temperature longitudinal impact absorption energy KU2≥55J for 5mm notched bars; low-magnification microstructure indicators: general porosity ≤1.5 grade, central porosity ≤1.5 grade, ingot segregation ≤1.5 grade, general spot segregation ≤1.0 grade, and edge spot segregation ≤1.0 grade; non-metallic inclusion indicators: Class A ≤2.0 grade, Class B ≤1.5 grade, Class C ≤1.5 grade, Class D ≤1.5 grade, and Class DS ≤2.0 grade.

[0010] A method for producing steel bars for automotive drive shafts based on an eco-electric furnace, the production process including eco-electric furnace smelting, LF refining, RH refining, continuous casting, billet heating, rolling, heat preservation and heat treatment;

[0011] The ecological electric furnace smelting process is as follows: by weight percentage, the proportion of molten iron is 35%–40%, and the proportion of scrap steel is 60%–65%; the molten iron inlet temperature is 1280–1290℃, and the tapping temperature is 1615–1625℃; the carbon content of the molten steel at tapping is 0.08%–0.12%, and the phosphorus content is ≤0.010%; when the tapping volume reaches 1 / 4–1 / 3 of the total molten steel volume, slag, pre-deoxidizer, and alloys are added; the smelting cycle is 55–65 minutes, and the furnace oxygen consumption is 21–22 m³ / t steel; the alloys and their addition amounts are as follows: The following materials are used: 4.0-4.2 kg / t steel for silicon-manganese alloy, 6.0-6.2 kg / t steel for medium-carbon ferromanganese, and 14.0-14.2 kg / t steel for low-carbon ferrochrome; the slag material is bearing steel synthetic slag, with an addition of 5.0-5.2 kg / t steel; the pre-deoxidizer is aluminum wire segment, with an addition of 0.8-0.9 kg / t steel; the auxiliary materials and their addition amounts are: 6.5-6.7 kg / t steel for coke particles, 5.8-6.2 kg / t steel for steel ladle ash, 35-36 kg / t steel for active lime, and 13.0-13.5 kg / t steel for magnesite.

[0012] Furthermore, the LF refining process is as follows: the LF inlet temperature is 1515–1525℃, and a high current of 35000–36000A is used for heating and slag formation. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime is added. After refining for 5–6 minutes, the first sample is taken for chemical composition analysis, and alloys and carbon are added according to the chemical composition. When the molten steel temperature reaches 1610–1620℃, 1.4–1.5 kg / t of alumina balls, a diffusion deoxidizer, is added for diffusion deoxidation. The furnace door is closed for 10–13 minutes, and when the molten steel temperature reaches 1625–1620℃, the process is repeated. A second sample was taken at 635℃ to analyze the chemical composition; after the second sample, the steel was removed from the station when the temperature reached 1645~1655℃; the LF smelting cycle was 45~50min, and the clearance was 420~430mm; the alloys added and their amounts were: ferrosilicon 0.3~0.32kg / t steel, high-carbon ferromanganese 3.5~3.6kg / t steel, high-carbon ferrochrome 5.8~6.0kg / t steel, ferrotitanium 1.4~1.5kg / t steel, and cutting aluminum 0.4~0.45kg / t steel; in addition, 5~5.2kg / t steel of active lime was added as an auxiliary material.

[0013] Furthermore, the RH refining process is as follows: the steel inlet temperature is 1635–1645℃, and the refining time is 45–55 min; before starting the vacuum pump, the argon pressure is controlled at 0.1–0.3 MPa, and timing begins when the vacuum reaches 100–110 Pa and is maintained for 10–15 min, while the argon pressure is adjusted to 0.3–0.5 MPa; after static argon blowing, 0.5–0.6 kg / t steel is added as a covering agent, and the clearance is maintained at 480–520 mm; the steel outlet temperature is 1585–1595℃; after the vacuum is broken, 0.6–0.62 kg / t steel is added as a ladle covering agent, 0.84–0.86 kg / t steel as silicon-calcium alloy cored wire, and 0.56–0.58 kg / t steel as sulfur concentrate powder cored wire.

[0014] Furthermore, the continuous casting process is as follows: the ladle temperature is 1580-1590℃, the H content of the molten steel in the tundish is controlled to be ≤2ppm, the casting time is 38-42min, the superheat is controlled at 25-30℃, and the casting speed is 0.45-0.47m / min; the entire process is protected during casting, and medium carbon steel protective slag is used in the crystallizer, with an addition amount of 3.6-3.7kg / t steel.

[0015] Furthermore, the billet heating process is as follows: the billet temperature entering the heating furnace is 500℃~550℃, the preheating section temperature is 660℃~680℃, and the preheating section heating time is 1.4~1.5h; the second heating section temperature is 850℃~870℃, and the heating time is 1.3~1.5h; the first heating section temperature is 1210℃~1240℃, and the heating time is 1.3~1.5h; the soaking section temperature is 1210℃~1230℃, and the soaking section heating time is 1.3~1.5h; the tapping temperature is 1180℃~1210℃.

[0016] Furthermore, the rolling process includes a preliminary rolling process and a continuous rolling process, wherein:

[0017] The initial rolling process involves 9 passes; the rolling reduction is as follows: turning the steel → 1st pass reduction 65-65.01mm → 2nd pass reduction 70-70.01mm → turning the steel → 3rd pass reduction 64-64.01mm → 4th pass reduction 90-90.01mm → turning the steel → 5th pass reduction 42-42.01mm → 6th pass reduction 40-40.01mm → 7th pass reduction 35-35.01mm → 8th pass reduction 34-34.01mm → turning the steel → 9th pass reduction 82-82.01mm; after being rolled by 3 850mm mills and 1 735mm mill, it enters the continuous rolling mill for further rolling.

[0018] The continuous rolling process involves 7 passes; the rolling speeds are as follows: Pass 1: 0.27–0.272 m / s; Pass 2: 0.31–0.312 m / s; Pass 3: 0.31–0.312 m / s; Pass 4: 0.393–0.395 m / s; Pass 5: 0.499–0.500 m / s; Pass 6: 0.607–0.608 m / s; the finished product is obtained after 7 passes.

[0019] The billet dimensions changed as follows during the initial rolling process: Pass 1: width 408–408.01 mm, height 421–421.01 mm; Pass 2: width 426–426.01 mm, height 351–351.01 mm; Pass 3: width 370–370.01 mm, height 362–362.01 mm; Pass 4: width 397–397.01 mm, height 272–272.01 mm; Pass 5: width 285 mm. ~285.01mm wide, 355~355.01mm high; 6th pass rolled to 297~297.01mm wide, 315~315.01mm high; 7th pass rolled to 307~307.01mm wide, 280~280.01mm high; 8th pass rolled to 317~317.01mm wide, 246~246.01mm high; 9th pass rolled to 271~271.01mm wide, 235~235.01mm high;

[0020] The billet dimensions change as follows during continuous rolling: Pass 1: height 229–229.01 mm, width 245–245.01 mm; Pass 2: height 192–192.01 mm, width 235–235.01 mm; Pass 3: height 200–200.01 mm, width 195–195.01 mm; Pass 4: height 163–163.01 mm, width 200–200.01 mm; Pass 5: height 169–169.01 mm, width 176–176.01 mm; Pass 6: height 128–128.01 mm, width 172–172.01 mm; Pass 7: height 142–142.01 mm, width 142–142.01 mm.

[0021] Furthermore, during the insulation process, the temperature of the steel in the insulation pit is ≥570℃, the insulation time is 48~55h, and the temperature when it exits the insulation pit is ≤150℃.

[0022] Furthermore, the heat treatment process includes the following steps:

[0023] (1) First quenching: Quenching temperature 870~890℃, holding time 0.8~1.2h, oil cooling to room temperature;

[0024] (2) Second quenching: Quenching temperature 860~880℃, holding time 0.8~1.2h, oil cooling to room temperature;

[0025] (3) Tempering: Tempering temperature 190~210℃, holding time 1.8~2.2h, water cooling to room temperature.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] (1) The production process of “ecological electric furnace + LF + RH + continuous casting billet → heating → primary rolling mill → continuous rolling mill” ensures the purity of steel and the product has excellent mechanical properties.

[0028] (2) Through reasonable component design and matching production process, the surface quality and mechanical properties of steel bars are guaranteed;

[0029] (3) The low magnification structure and non-metallic inclusions of the finished steel bars meet the requirements of high-end products. Detailed Implementation

[0030] The present invention discloses a steel bar for automotive drive shafts based on an eco-friendly electric furnace. The chemical composition of the steel bar for automotive drive shafts, by mass percentage, is: C: 0.18%–0.22%, Si: 0.22%–0.33%, Mn: 0.85%–1.00%, P≤0.015%, S≤0.005%, Cr: 1.05%–1.20%, Ni≤0.25%, Mo≤0.10%, Ti: 0.05%–0.09%, Cu≤0.15%; the remainder is Fe and unavoidable impurities.

[0031] Furthermore, the finished product properties of the steel bars for automotive drive shafts are as follows: tensile strength Rm≥1080MPa, yield strength Rel≥850MPa, elongation A≥10%, reduction of area z≥45%, and room temperature longitudinal impact absorption energy KU2≥55J for 5mm notched bars; low-magnification microstructure indicators: general porosity ≤1.5 grade, central porosity ≤1.5 grade, ingot segregation ≤1.5 grade, general spot segregation ≤1.0 grade, and edge spot segregation ≤1.0 grade; non-metallic inclusion indicators: Class A ≤2.0 grade, Class B ≤1.5 grade, Class C ≤1.5 grade, Class D ≤1.5 grade, and Class DS ≤2.0 grade.

[0032] The present invention discloses a method for producing steel bars for automotive drive shafts based on an eco-electric furnace. The production process includes eco-electric furnace smelting, LF refining, RH refining, continuous casting, billet heating, rolling, heat preservation, and heat treatment.

[0033] The ecological electric furnace smelting process is as follows: by weight percentage, the proportion of molten iron is 35%–40%, and the proportion of scrap steel is 60%–65%; the molten iron inlet temperature is 1280–1290℃, and the tapping temperature is 1615–1625℃; the carbon content of the molten steel at tapping is 0.08%–0.12%, and the phosphorus content is ≤0.010%; when the tapping volume reaches 1 / 4–1 / 3 of the total molten steel volume, slag, pre-deoxidizer, and alloys are added; the smelting cycle is 55–65 minutes, and the furnace oxygen consumption is 21–22 m³ / t steel; the alloys and their addition amounts are as follows: The following materials are used: 4.0-4.2 kg / t steel for silicon-manganese alloy, 6.0-6.2 kg / t steel for medium-carbon ferromanganese, and 14.0-14.2 kg / t steel for low-carbon ferrochrome; the slag material is bearing steel synthetic slag, with an addition of 5.0-5.2 kg / t steel; the pre-deoxidizer is aluminum wire segment, with an addition of 0.8-0.9 kg / t steel; the auxiliary materials and their addition amounts are: 6.5-6.7 kg / t steel for coke particles, 5.8-6.2 kg / t steel for steel ladle ash, 35-36 kg / t steel for active lime, and 13.0-13.5 kg / t steel for magnesite.

[0034] Furthermore, the LF refining process is as follows: the LF inlet temperature is 1515–1525℃, and a high current of 35000–36000A is used for heating and slag formation. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime is added. After refining for 5–6 minutes, the first sample is taken for chemical composition analysis, and alloys and carbon are added according to the chemical composition. When the molten steel temperature reaches 1610–1620℃, 1.4–1.5 kg / t of alumina balls, a diffusion deoxidizer, is added for diffusion deoxidation. The furnace door is closed for 10–13 minutes, and when the molten steel temperature reaches 1625–1620℃, the process is repeated. A second sample was taken at 635℃ to analyze the chemical composition; after the second sample, the steel was removed from the station when the temperature reached 1645~1655℃; the LF smelting cycle was 45~50min, and the clearance was 420~430mm; the alloys added and their amounts were: ferrosilicon 0.3~0.32kg / t steel, high-carbon ferromanganese 3.5~3.6kg / t steel, high-carbon ferrochrome 5.8~6.0kg / t steel, ferrotitanium 1.4~1.5kg / t steel, and cutting aluminum 0.4~0.45kg / t steel; in addition, 5~5.2kg / t steel of active lime was added as an auxiliary material.

[0035] Furthermore, the RH refining process is as follows: the steel inlet temperature is 1635–1645℃, and the refining time is 45–55 min; before starting the vacuum pump, the argon pressure is controlled at 0.1–0.3 MPa, and timing begins when the vacuum reaches 100–110 Pa and is maintained for 10–15 min, while the argon pressure is adjusted to 0.3–0.5 MPa; after static argon blowing, 0.5–0.6 kg / t steel is added as a covering agent, and the clearance is maintained at 480–520 mm; the steel outlet temperature is 1585–1595℃; after the vacuum is broken, 0.6–0.62 kg / t steel is added as a ladle covering agent, 0.84–0.86 kg / t steel as silicon-calcium alloy cored wire, and 0.56–0.58 kg / t steel as sulfur concentrate powder cored wire.

[0036] Furthermore, the continuous casting process is as follows: the ladle temperature is 1580-1590℃, the H content of the molten steel in the tundish is controlled to be ≤2ppm, the casting time is 38-42min, the superheat is controlled at 25-30℃, and the casting speed is 0.45-0.47m / min; the entire process is protected during casting, and medium carbon steel protective slag is used in the crystallizer, with an addition amount of 3.6-3.7kg / t steel.

[0037] Furthermore, the billet heating process is as follows: the billet temperature entering the heating furnace is 500℃~550℃, the preheating section temperature is 660℃~680℃, and the preheating section heating time is 1.4~1.5h; the second heating section temperature is 850℃~870℃, and the heating time is 1.3~1.5h; the first heating section temperature is 1210℃~1240℃, and the heating time is 1.3~1.5h; the soaking section temperature is 1210℃~1230℃, and the soaking section heating time is 1.3~1.5h; the tapping temperature is 1180℃~1210℃.

[0038] Furthermore, the rolling process includes a preliminary rolling process and a continuous rolling process, wherein:

[0039] The initial rolling process involves 9 passes; the rolling reduction is as follows: turning the steel → 1st pass reduction 65-65.01mm → 2nd pass reduction 70-70.01mm → turning the steel → 3rd pass reduction 64-64.01mm → 4th pass reduction 90-90.01mm → turning the steel → 5th pass reduction 42-42.01mm → 6th pass reduction 40-40.01mm → 7th pass reduction 35-35.01mm → 8th pass reduction 34-34.01mm → turning the steel → 9th pass reduction 82-82.01mm; after being rolled by 3 850mm mills and 1 735mm mill, it enters the continuous rolling mill for further rolling.

[0040] The continuous rolling process involves 7 passes; the rolling speeds are as follows: Pass 1: 0.27–0.272 m / s; Pass 2: 0.31–0.312 m / s; Pass 3: 0.31–0.312 m / s; Pass 4: 0.393–0.395 m / s; Pass 5: 0.499–0.500 m / s; Pass 6: 0.607–0.608 m / s; the finished product is obtained after 7 passes.

[0041] The billet dimensions changed as follows during the initial rolling process: Pass 1: width 408–408.01 mm, height 421–421.01 mm; Pass 2: width 426–426.01 mm, height 351–351.01 mm; Pass 3: width 370–370.01 mm, height 362–362.01 mm; Pass 4: width 397–397.01 mm, height 272–272.01 mm; Pass 5: width 285 mm. ~285.01mm wide, 355~355.01mm high; 6th pass rolled to 297~297.01mm wide, 315~315.01mm high; 7th pass rolled to 307~307.01mm wide, 280~280.01mm high; 8th pass rolled to 317~317.01mm wide, 246~246.01mm high; 9th pass rolled to 271~271.01mm wide, 235~235.01mm high;

[0042] The billet dimensions change as follows during continuous rolling: Pass 1: height 229–229.01 mm, width 245–245.01 mm; Pass 2: height 192–192.01 mm, width 235–235.01 mm; Pass 3: height 200–200.01 mm, width 195–195.01 mm; Pass 4: height 163–163.01 mm, width 200–200.01 mm; Pass 5: height 169–169.01 mm, width 176–176.01 mm; Pass 6: height 128–128.01 mm, width 172–172.01 mm; Pass 7: height 142–142.01 mm, width 142–142.01 mm.

[0043] Furthermore, during the insulation process, the temperature of the steel in the insulation pit is ≥570℃, the insulation time is 48~55h, and the temperature when it exits the insulation pit is ≤150℃.

[0044] Furthermore, the heat treatment process includes the following steps:

[0045] (1) First quenching: Quenching temperature 870~890℃, holding time 0.8~1.2h, oil cooling to room temperature;

[0046] (2) Second quenching: Quenching temperature 860~880℃, holding time 0.8~1.2h, oil cooling to room temperature;

[0047] (3) Tempering: Tempering temperature 190~210℃, holding time 1.8~2.2h, water cooling to room temperature.

[0048] Unless otherwise specified, all percentages in this invention are weight percentages.

[0049] The following embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0050]

Example 1

[0051] In this embodiment, the chemical composition of the steel bar for the automotive drive shaft, by mass percentage, is: C: 0.19%, Si: 0.26%, Mn: 0.88%, P: 0.012%, S: 0.004%, Cr: 1.08%, Ni: 0.08%, Mo: 0.02%, Ti: 0.07%, Cu: 0.02%, with the remainder being Fe and unavoidable impurities.

[0052] In this embodiment, the steel bars for the automotive drive shaft are smelted in an eco-friendly electric furnace. The specific process route is as follows: eco-friendly electric furnace smelting + LF refining + RH refining + continuous casting → heating furnace heating → rolling → heat holding → heat treatment. The specific process is as follows:

[0053] (1) Ecological electric furnace smelting

[0054] The molten iron ratio is 37%, and the scrap steel ratio is 63%. The molten iron charging temperature is 1285℃, and the tapping temperature is 1620℃. At tapping, the carbon content is 0.09%, and the phosphorus content is 0.008%. Slag, pre-deoxidizer, and alloying agents are added when the molten steel volume is 1 / 4 full. The smelting cycle is 60 minutes, and the furnace oxygen consumption is 21m³. 3 / t steel. Alloys and their addition amounts are: silicon-manganese alloy 4.0kg / t steel, medium-carbon ferromanganese 6.0kg / t steel, low-carbon ferrochrome 14.0kg / t steel. Slag is bearing steel synthetic slag, added at 5.0kg / t steel. Pre-deoxidizer is aluminum wire segments (12mm diameter), added at 0.8kg / t steel. Auxiliary materials and their addition amounts are: coke granules 6.6kg / t steel, steel ladle ash 6.0kg / t steel, active lime (30mm particle size) 35kg / t steel, magnesite (40mm particle size) 13.0kg / t steel.

[0055] (2) LF furnace refining

[0056] The LF furnace enters at 1521℃ and uses a 35300A high-current heating method for slag formation. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime is added. After 5 minutes of refining, a first sample is taken for chemical composition analysis. Alloys are added according to the chemical composition, and carbon is increased to promote rapid melting and homogenization of the alloys and carbon powder. When the molten steel temperature reaches 1615℃, 1.4 kg / t of diffusion deoxidizer (alumina balls) is added for diffusion deoxidation, and the furnace door is closed for 12 minutes. When the molten steel temperature reaches 1628℃, a second sample is taken for chemical composition analysis to confirm the deviation of each chemical element content from the target value. After the second sample is taken, the furnace leaves when the molten steel temperature reaches 1648℃. The LF smelting cycle is 47 minutes, with a clearance of 425 mm. The supplementary alloys include: ferrosilicon 0.3 kg / t steel, high-carbon ferromanganese 3.5 kg / t steel, high-carbon ferrochrome 5.9 kg / t steel, ferrotitanium (FeTi70-A) 1.4 kg / t steel, and machined aluminum (10mm×3mm×1mm) 0.42 kg / t steel. The supplementary auxiliary material is: active lime (30mm particle size) 5 kg / t steel.

[0057] (3) RH refining

[0058] The inlet temperature was 1640℃, and the refining time was 49 minutes. Before starting the vacuum pump, the argon pressure was controlled at 0.1 MPa, with slight movement of the slag surface and no exposed molten steel. When the vacuum reached 100 Pa, timing began and was maintained for 12 minutes, while the argon pressure was adjusted to 0.3 MPa. After static argon blowing, 0.5 kg / t of covering agent was added, with a clearance of 500 mm and an outlet temperature of 1589℃. After breaking the vacuum, 0.6 kg / t of ladle covering agent, 0.85 kg / t of silicon-calcium alloy cored wire (14 mm diameter), and 0.56 kg / t of sulfur concentrate powder cored wire (13 mm diameter) were added.

[0059] (5) Continuous casting

[0060] The ladle temperature upon arrival is 1586℃, the hydrogen content of the molten steel in the tundish is controlled at 1.5ppm, the casting time is 40min, the superheat is 27℃, the casting speed is 0.46m / min, the entire casting process is protected, and medium carbon steel protective slag is used in the crystallizer, with an addition amount of 3.6kg / t steel.

[0061] (5) Heating

[0062] The billet enters the heating furnace at a temperature of 520℃, the preheating section at 660℃, and is heated for 1.4 hours; the second heating section at 870℃, is heated for 1.3 hours; the first heating section at 1216℃, is heated for 1.3 hours; the soaking section at 1205℃, is heated for 1.5 hours; and the tapping temperature is 1195℃.

[0063] (6) Rolling

[0064] The initial rolling process involves 9 passes, specifically: Turning the steel over → Pass 1: Roll to a width of 408mm, a height of 421mm, and a reduction of 65mm → Pass 2: Roll to a width of 426mm, a height of 351mm, and a reduction of 70mm → Turning the steel over → Pass 3: Roll to a width of 370mm, a height of 362mm, and a reduction of 64mm → Pass 4: Roll to a width of 397mm, a height of 272mm, and a reduction of 90mm → Turning the steel over → Pass 5: Roll to a width of 285mm, a height of 355mm, and a reduction of 64mm → Pass 6 ...6: Roll to a width of 285mm, a height of 355mm, and a reduction of 64mm → Pass 7: Roll to a width of 408mm, a height of 421mm, and a reduction of 65mm → Pass 6: Roll to a width of 408mm, a height of 421mm, and a reduction of 65mm → Pass 6: Roll to a width of 426mm, a height of 351mm, and a reduction of 70mm → Turning the steel over → Pass 6: Roll to a width of 285mm, a height of 355mm, and a reduction of 64mm → Pass 7: Roll to a width of 397mm, a height of 272mm, and a reduction of 90mm → Turn 42mm reduction → 6th pass: rolled to 297mm width, 315mm height, 40mm reduction → 7th pass: rolled to 307mm width, 280mm height, 35mm reduction → 8th pass: rolled to 317mm width, 246mm height, 34mm reduction → Turned over → 9th pass: rolled to 271mm width, 235mm height, 82mm reduction; After being rolled by 3 850mm rolling mills and 1 735mm rolling mill, it enters the continuous rolling mill unit for rolling.

[0065] The continuous rolling process consists of 7 passes: the first pass rolls the material to a height of 229 mm and a width of 245 mm at a speed of 0.27 m / s; the second pass rolls the material to a height of 192 mm and a width of 235 mm at a speed of 0.31 m / s; the third pass rolls the material to a height of 200 mm and a width of 195 mm at a speed of 0.31 m / s; the fourth pass rolls the material to a height of 163 mm and a width of 200 mm at a speed of 0.393 m / s; the fifth pass rolls the material to a height of 169 mm and a width of 176 mm at a speed of 0.499 m / s; the sixth pass rolls the material to a height of 128 mm and a width of 172 mm at a speed of 0.607 m / s; and the seventh pass rolls the material to a height of 142 mm and a width of 142 mm. The finished product is then produced after 7 passes.

[0066] (7) Insulation

[0067] The temperature of the steel in the insulation pit is 580℃, and it is kept in the insulation pit for 52 hours. The temperature when it comes out of the pit is 120℃.

[0068] (8) Heat treatment

[0069] After heat treatment, samples of the steel were taken and subjected to heat treatment, which included the following steps:

[0070] 1) First quenching: Hold at 880℃ for 1.0h, then oil cool;

[0071] 2) Second quenching: Hold at 870℃ for 1.0 h, then oil cool;

[0072] 3) Tempering: Hold at 200℃ for 2.0h, then water-cool.

[0073]

Example 2

[0074] In this embodiment, the chemical composition of the steel bar for the automotive drive shaft, by mass percentage, is: C: 0.21%, Si: 0.27%, Mn: 0.90%, P: 0.011%, S: 0.005%, Cr: 1.10%, Ni: 0.07%, Mo: 0.02%, Ti: 0.07%, Cu: 0.02%, with the remainder being Fe and unavoidable impurities.

[0075] In this embodiment, the steel bars for the automotive drive shaft are smelted in an eco-friendly electric furnace. The specific process route is as follows: eco-friendly electric furnace smelting + LF refining + RH refining + continuous casting → heating furnace heating → rolling → heat holding → heat treatment. The specific process is as follows:

[0076] (1) Ecological electric furnace smelting

[0077] The molten iron ratio is 38%, and the scrap steel ratio is 62%. The molten iron charging temperature is 1285℃, and the tapping temperature is 1619℃. At tapping, the carbon content is 0.09%, and the phosphorus content is 0.008%. Slag, pre-deoxidizer, and alloying agents are added when the molten steel volume is 1 / 4 full. The smelting cycle is 62 minutes, and the furnace oxygen consumption is 21m³. 3 / t steel. Alloys and dosages: 4.0 kg / t steel for silicon-manganese alloy, 6.0 kg / t steel for medium-carbon ferromanganese, and 14.0 kg / t steel for low-carbon ferrochrome. Slag is bearing steel synthetic slag, with a dosage of 5.0 kg / t. Pre-deoxidizer is aluminum wire segments (12 mm in diameter), with a dosage of 0.8 kg / t steel. Auxiliary materials and dosages are: 6.5 kg / t steel for coke particles, 5.9 kg / t steel for steel ladle ash, 35 kg / t steel for active lime (30 mm particle size), and 13.2 kg / t steel for magnesite (40 mm particle size).

[0078] (2) LF Refining

[0079] The LF furnace enters at 1520℃ and uses a 35500A high-current heating method for slag formation. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime is added. After 5 minutes of refining, a first sample is taken for chemical composition analysis. Alloys are added according to the chemical composition, and carbon is increased to promote rapid melting and homogenization of the alloys and carbon powder. When the molten steel temperature reaches 1615℃, 1.4 kg / t of diffusion deoxidizer (alumina balls) is added for diffusion deoxidation, and the furnace door is closed for 10 minutes. When the molten steel temperature reaches 1629℃, a second sample is taken for chemical composition analysis to confirm the deviation of each chemical element content from the target value. After the second sample is taken, the furnace leaves when the molten steel temperature reaches 1650℃. The LF smelting cycle is 48 minutes, with a clearance of 425 mm. The supplementary alloys include: ferrosilicon 0.3 kg / t steel, high-carbon ferromanganese 3.5 kg / t steel, high-carbon ferrochrome 5.8 kg / t steel, ferrotitanium (FeTi70-A) 1.4 kg / t steel, and machined aluminum (10mm×3mm×1mm) 0.42 kg / t steel. The supplementary auxiliary material is: active lime (30mm particle size) 5 kg / t steel.

[0080] (3) RH refining

[0081] The inlet temperature was 1640℃, and the refining time was 48 minutes. Before starting the vacuum pump, the argon pressure was controlled at 0.1 MPa, with slight movement of the slag surface and no exposed molten steel. When the vacuum reached 100 Pa, timing began and was maintained for 11 minutes, while the argon pressure was adjusted to 0.3 MPa. After static argon blowing, 0.52 kg / t of covering agent was added, the clearance was 495 mm, and the outlet temperature was 1590℃. After breaking the vacuum, 0.6 kg / t of ladle covering agent, 0.85 kg / t of silicon-calcium alloy cored wire (14 mm diameter), and 0.57 kg / t of sulfur concentrate powder cored wire (13 mm diameter) were added.

[0082] (6) Continuous casting

[0083] The ladle temperature upon arrival is 1586℃, the H content of the molten steel in the tundish is controlled at 1.3ppm, the casting time is 39min, the superheat is 28℃, the casting speed is 0.46m / min, the entire casting process is protected, and medium carbon steel protective slag is used in the crystallizer, with an addition amount of 3.6kg / t steel.

[0084] (5) Heating

[0085] The billet enters the heating furnace at a temperature of 520℃, the preheating section at 660℃, and is heated for 1.3 hours; the second heating section at 870℃, is heated for 1.4 hours; the first heating section requires a temperature of 1214℃, and is heated for 1.3 hours; the soaking section at 1204℃, is heated for 1.3 hours; and the tapping temperature is 1195℃.

[0086] (6) Rolling

[0087] The initial rolling process involves 9 passes, specifically: Turning the steel over → Pass 1: Roll to a width of 408mm, a height of 421mm, and a reduction of 65mm → Pass 2: Roll to a width of 426mm, a height of 351mm, and a reduction of 70mm → Turning the steel over → Pass 3: Roll to a width of 370mm, a height of 362mm, and a reduction of 64mm → Pass 4: Roll to a width of 397mm, a height of 272mm, and a reduction of 90mm → Turning the steel over → Pass 5: Roll to a width of 285mm, a height of 355mm, and a reduction of 64mm → Pass 6 ...6: Roll to a width of 285mm, a height of 355mm, and a reduction of 64mm → Pass 7: Roll to a width of 408mm, a height of 421mm, and a reduction of 65mm → Pass 6: Roll to a width of 408mm, a height of 421mm, and a reduction of 65mm → Pass 6: Roll to a width of 426mm, a height of 351mm, and a reduction of 70mm → Turning the steel over → Pass 6: Roll to a width of 285mm, a height of 355mm, and a reduction of 64mm → Pass 7: Roll to a width of 397mm, a height of 272mm, and a reduction of 90mm → Turn 42mm reduction → 6th pass: rolled to 297mm width, 315mm height, 40mm reduction → 7th pass: rolled to 307mm width, 280mm height, 35mm reduction → 8th pass: rolled to 317mm width, 246mm height, 34mm reduction → Turned over → 9th pass: rolled to 271mm width, 235mm height, 82mm reduction; After being rolled by 3 850mm rolling mills and 1 735mm rolling mill, it enters the continuous rolling mill unit for rolling.

[0088] The continuous rolling process consists of 7 passes: the first pass rolls the material to a height of 229 mm and a width of 245 mm at a speed of 0.27 m / s; the second pass rolls the material to a height of 192 mm and a width of 235 mm at a speed of 0.31 m / s; the third pass rolls the material to a height of 200 mm and a width of 195 mm at a speed of 0.31 m / s; the fourth pass rolls the material to a height of 163 mm and a width of 200 mm at a speed of 0.393 m / s; the fifth pass rolls the material to a height of 169 mm and a width of 176 mm at a speed of 0.499 m / s; the sixth pass rolls the material to a height of 128 mm and a width of 172 mm at a speed of 0.607 m / s; and the seventh pass rolls the material to a height of 142 mm and a width of 142 mm. The finished product is then produced after 7 passes.

[0089] (7) Insulation

[0090] The temperature of the steel in the insulation pit was 585℃, and it was kept in the insulation pit for 53 hours. The temperature when it came out of the pit was 120℃.

[0091] (8) Heat treatment

[0092] After heat treatment, samples of the steel were taken and subjected to heat treatment, which included the following steps:

[0093] 1) First quenching: Hold at 880℃ for 1.0h, then oil cool;

[0094] 2) Second quenching: Hold at 870℃ for 1.0 h, then oil cool;

[0095] 3) Tempering: Hold at 200℃ for 2.0h, then water-cool.

[0096]

Example 3

[0097] In this embodiment, the chemical composition of the steel bar for the automotive drive shaft, by mass percentage, is: C: 0.20%, Si: 0.26%, Mn: 0.90%, P: 0.010%, S: 0.004%, Cr: 1.10%, Ni: 0.08%, Mo: 0.05%, Ti: 0.07%, Cu: 0.02%, with the remainder being Fe and unavoidable impurities.

[0098] In this embodiment, the steel bars for the automotive drive shaft are smelted in an eco-friendly electric furnace. The specific process route is as follows: eco-friendly electric furnace smelting + LF refining + RH refining + continuous casting → heating furnace heating → rolling → heat holding → heat treatment. The specific process is as follows:

[0099] (1) Ecological electric furnace smelting

[0100] The molten iron content is 38%, and the scrap steel content is 62%. Of the scrap steel, heavy scrap accounts for 45%, carbon structural steel cuts account for 12%, and the remainder is baled automotive steel scrap. The molten iron charging temperature is 1285℃, and the tapping temperature is 1620℃. At tapping, the carbon content is 0.10%, and the phosphorus content is 0.008%. Slag, pre-deoxidizer, and alloying agents are added when the molten steel is reduced to 1 / 4 of its total volume. The smelting cycle is 62 minutes, and the furnace oxygen consumption is 21 m³ / min. 3 / t steel. Alloys and their addition amounts are: silicon-manganese alloy 4.0kg / t steel, medium-carbon ferromanganese 6.0kg / t steel, low-carbon ferrochrome 14.0kg / t steel. Slag is bearing steel synthetic slag, added at 5.0kg / t steel. Pre-deoxidizer is aluminum wire segments (12mm diameter), added at 0.8kg / t steel. Auxiliary materials and their addition amounts are: coke granules 6.5kg / t steel, steel ladle ash 6.0kg / t steel, active lime (30mm particle size) 35kg / t steel, magnesite (40mm particle size) 13.2kg / t steel.

[0101] (2) LF Refining

[0102] The LF furnace enters at a temperature of 1521℃, using a 35600A high-current heating method for slag formation. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime is added. After 5 minutes of refining, a first sample is taken for chemical composition analysis. Alloys are added according to the chemical composition, and carbon is increased to promote rapid melting and homogenization of the alloys and carbon powder. When the molten steel temperature reaches 1615℃, 1.4 kg / t of diffusion deoxidizer (alumina balls) is added for diffusion deoxidation. The furnace door is closed for 10 minutes. When the molten steel temperature reaches 1628℃, a second sample is taken for chemical composition analysis to confirm the deviation of each chemical element content from the target value. After the second sample is taken, the furnace leaves when the molten steel temperature reaches 1652℃. The LF smelting cycle is 48 minutes, with a clearance of 425 mm. The supplementary alloys include: ferrosilicon 0.3 kg / t steel, high-carbon ferromanganese 3.5 kg / t steel, high-carbon ferrochrome 5.8 kg / t steel, ferrotitanium (FeTi70-A) 1.4 kg / t steel, and machined aluminum (10mm×3mm×1mm) 0.42 kg / t steel. The supplementary auxiliary material is: active lime (30mm particle size) 5 kg / t steel.

[0103] (3) RH refining

[0104] The inlet temperature was 1641℃, the refining time was 48 minutes, and the argon pressure was controlled at 0.1 MPa before the vacuum pump was started, ensuring the molten steel was not exposed and the slag surface was slightly moved. Timing began when the vacuum reached 100 Pa and was maintained for 12 minutes, while the argon pressure was adjusted to 0.3 MPa. After static argon blowing, 0.5 kg / t of covering agent was added, the clearance was 495 mm, and the outlet temperature was 1588℃. After the vacuum was broken, 0.6 kg / t of ladle covering agent, 0.85 kg / t of silicon-calcium alloy cored wire (14 mm diameter), and 0.57 kg / t of sulfur concentrate powder cored wire (13 mm diameter) were added.

[0105] (7) Continuous casting

[0106] The ladle temperature upon arrival is 1585℃, the hydrogen content of the molten steel in the tundish is controlled at 1.5ppm, the casting time is 40min, the superheat is 27℃, the casting speed is 0.46m / min, the entire casting process is protected, and medium carbon steel protective slag is used in the crystallizer, with an addition amount of 3.6kg / t steel.

[0107] (5) Heating

[0108] The billet enters the heating furnace at a temperature of 520℃, the preheating section at 660℃, and is heated for 1.5 hours; the second heating section at 870℃, is heated for 1.3 hours; the first heating section at 1214℃, is heated for 1.3 hours; the soaking section at 1204℃, is heated for 1.3 hours; and the tapping temperature is 1195℃.

[0109] (6) Rolling

[0110] The initial rolling process consists of 9 passes: Turning the steel over → Pass 1: Roll to a width of 408mm, a height of 421mm, and a reduction of 65mm → Pass 2: Roll to a width of 426mm, a height of 351mm, and a reduction of 70mm → Turning the steel over → Pass 3: Roll to a width of 370mm, a height of 362mm, and a reduction of 64mm → Pass 4: Roll to a width of 397mm, a height of 272mm, and a reduction of 90mm → Turning the steel over → Pass 5: Roll to a width of 285mm and a height of 355mm 42mm reduction → 6th pass: rolled to 297mm width, 315mm height, 40mm reduction → 7th pass: rolled to 307mm width, 280mm height, 35mm reduction → 8th pass: rolled to 317mm width, 246mm height, 34mm reduction → Turned over → 9th pass: rolled to 271mm width, 235mm height, 82mm reduction; After passing through 3 850mm rolling mills and 1 735mm rolling mill, it enters the continuous rolling mill unit for rolling.

[0111] The continuous rolling process consists of 7 passes: the first pass rolls the material to a height of 229 mm and a width of 245 mm at a speed of 0.27 m / s; the second pass rolls the material to a height of 192 mm and a width of 235 mm at a speed of 0.31 m / s; the third pass rolls the material to a height of 200 mm and a width of 195 mm at a speed of 0.31 m / s; the fourth pass rolls the material to a height of 163 mm and a width of 200 mm at a speed of 0.393 m / s; the fifth pass rolls the material to a height of 169 mm and a width of 176 mm at a speed of 0.499 m / s; the sixth pass rolls the material to a height of 128 mm and a width of 172 mm at a speed of 0.607 m / s; and the seventh pass rolls the material to a height of 142 mm and a width of 142 mm. The finished product is then produced after 7 passes.

[0112] (7) Insulation

[0113] The temperature of the steel in the insulation pit is 580℃, and it is kept in the insulation pit for 54 hours. The temperature when it comes out of the pit is 120℃.

[0114] (8) Heat treatment

[0115] After heat treatment, samples of the steel were taken and subjected to heat treatment, which included the following steps:

[0116] 1) First quenching: Hold at 880℃ for 1.0h, then oil cool;

[0117] 2) Second quenching: Hold at 870℃ for 1.0 h, then oil cool;

[0118] 3) Tempering: Hold at 200℃ for 2.0h, then water-cool.

[0119]

Example 4

[0120] In this embodiment, the chemical composition of the steel bar for the automotive drive shaft, by mass percentage, is: C: 0.20%, Si: 0.26%, Mn: 0.92%, P: 0.012%, S: 0.004%, Cr: 1.10%, Ni: 0.08%, Mo: 0.03%, Ti: 0.07%, Cu: 0.02%, with the remainder being Fe and unavoidable impurities.

[0121] In this embodiment, the steel bars for the automotive drive shaft are smelted in an eco-friendly electric furnace. The specific process route is as follows: eco-friendly electric furnace smelting + LF refining + RH refining + continuous casting → heating furnace heating → rolling → heat holding → heat treatment. The specific process is as follows:

[0122] (1) Ecological electric furnace smelting

[0123] The molten iron content is 37%, and the scrap steel content is 63%. Of the scrap steel, heavy scrap accounts for 45%, carbon structural steel cuts account for 13%, and the remainder is baled automotive steel scrap. The molten iron charging temperature is 1286℃, and the tapping temperature is 1622℃. At tapping, the carbon content is 0.09%, and the phosphorus content is 0.007%. Slag, pre-deoxidizer, and alloying agents are added when the molten steel is about 1 / 4 full. The smelting cycle is 59 minutes, and the furnace oxygen consumption is 21 m³ / s. 3 / t steel. Alloys and their addition amounts are: silicon-manganese alloy 4.0kg / t steel, medium-carbon ferromanganese 6.0kg / t steel, low-carbon ferrochrome 14.0kg / t steel. Slag is bearing steel synthetic slag, added at 5.0kg / t steel. Pre-deoxidizer is aluminum wire segments (12mm diameter), added at 0.9kg / t steel. Auxiliary materials and their addition amounts are: coke granules 6.5kg / t steel, steel ladle ash 6.0kg / t steel, active lime (30mm particle size) 35kg / t steel, magnesite (40mm particle size) 13.2kg / t steel.

[0124] (2) LF Refining

[0125] The LF furnace enters at a temperature of 1521℃ and uses a high current of 35600A for slag heating. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime is added. After refining for 5 minutes, the first sample is taken for chemical composition analysis. Alloys are added according to the chemical composition, and carbon is increased to promote rapid melting and homogenization of the alloys and carbon powder. When the molten steel temperature reaches 1614℃, 1.4 kg / t of diffusion deoxidizer (alumina balls) is added for diffusion deoxidation. The furnace door is closed for 10 minutes. When the molten steel temperature reaches 1629℃, a second sample is taken for chemical composition analysis to confirm the deviation of the content of each chemical element from the target value. After the second sample is taken, the furnace leaves when the molten steel temperature reaches 1648℃. The LF smelting cycle is 47 minutes, with a clearance of 425 mm. The supplementary alloys include: ferrosilicon 0.3 kg / t steel, high-carbon ferromanganese 3.5 kg / t steel, high-carbon ferrochrome 5.8 kg / t steel, ferrotitanium (FeTi70-A) 1.4 kg / t steel, and machined aluminum (10mm×3mm×1mm) 0.41 kg / t steel. The supplementary auxiliary material is: active lime (30mm particle size) 5 kg / t steel.

[0126] (3) RH refining

[0127] The inlet temperature was 1638℃, the refining time was 52 minutes, and the argon pressure was controlled at 0.1 MPa before the vacuum pump was started. The molten steel was not exposed due to slight movement of the slag surface. Timing began when the vacuum reached 100 Pa and was maintained for 10 minutes, while the argon pressure was adjusted to 0.3 MPa. After static argon blowing, 0.5 kg / t of covering agent was added, the clearance was 510 mm, and the outlet temperature was 1590℃. After the vacuum was broken, 0.6 kg / t of ladle covering agent, 0.85 kg / t of silicon-calcium alloy cored wire (14 mm diameter), and 0.57 kg / t of sulfur concentrate powder cored wire (13 mm diameter) were added.

[0128] (8) Continuous casting

[0129] The ladle temperature upon arrival is 1585℃, the hydrogen content of the molten steel in the tundish is controlled at 1.5ppm, the casting time is 40min, the superheat is 27℃, the casting speed is 0.46m / min, the entire casting process is protected, and medium carbon steel protective slag is used in the crystallizer, with an addition amount of 3.6kg / t steel.

[0130] (5) Heating

[0131] The billet enters the heating furnace at a temperature of 520℃, the preheating section at 670℃, and is heated for 1.4 hours; the second heating section at 870℃, is heated for 1.5 hours; the first heating section at 1215℃, is heated for 1.3 hours; the soaking section at 1204℃, is heated for 1.4 hours; and the tapping temperature is 1194℃.

[0132] (6) Rolling

[0133] The initial rolling process involves 9 passes, specifically: Turning the steel over → Pass 1: Roll to a width of 408mm, a height of 421mm, and a reduction of 65mm → Pass 2: Roll to a width of 426mm, a height of 351mm, and a reduction of 70mm → Turning the steel over → Pass 3: Roll to a width of 370mm, a height of 362mm, and a reduction of 64mm → Pass 4: Roll to a width of 397mm, a height of 272mm, and a reduction of 90mm → Turning the steel over → Pass 5: Roll to a width of 285mm, a height of 355mm, and a reduction of 64mm → Pass 6 ...6: Roll to a width of 285mm, a height of 355mm, and a reduction of 64mm → Pass 7: Roll to a width of 408mm, a height of 421mm, and a reduction of 65mm → Pass 6: Roll to a width of 408mm, a height of 421mm, and a reduction of 65mm → Pass 6: Roll to a width of 426mm, a height of 351mm, and a reduction of 70mm → Turning the steel over → Pass 6: Roll to a width of 285mm, a height of 355mm, and a reduction of 64mm → Pass 7: Roll to a width of 397mm, a height of 272mm, and a reduction of 90mm → Turn 42mm reduction → 6th pass: rolled to 297mm width, 315mm height, 40mm reduction → 7th pass: rolled to 307mm width, 280mm height, 35mm reduction → 8th pass: rolled to 317mm width, 246mm height, 34mm reduction → Turned over → 9th pass: rolled to 271mm width, 235mm height, 82mm reduction; After being rolled by 3 850mm rolling mills and 1 735mm rolling mill, it enters the continuous rolling mill unit for rolling.

[0134] The continuous rolling process consists of 7 passes: the first pass rolls the material to a height of 229 mm and a width of 245 mm at a speed of 0.27 m / s; the second pass rolls the material to a height of 192 mm and a width of 235 mm at a speed of 0.31 m / s; the third pass rolls the material to a height of 200 mm and a width of 195 mm at a speed of 0.31 m / s; the fourth pass rolls the material to a height of 163 mm and a width of 200 mm at a speed of 0.393 m / s; the fifth pass rolls the material to a height of 169 mm and a width of 176 mm at a speed of 0.499 m / s; the sixth pass rolls the material to a height of 128 mm and a width of 172 mm at a speed of 0.607 m / s; and the seventh pass rolls the material to a height of 142 mm and a width of 142 mm. The finished product is then produced after 7 passes.

[0135] (7) Insulation

[0136] The temperature of the steel in the insulation pit is 580℃, and it is kept in the insulation pit for 54 hours. The temperature when it comes out of the pit is 120℃.

[0137] (8) Heat treatment

[0138] After heat treatment, samples of the steel were taken and subjected to heat treatment, which included the following steps:

[0139] 1) First quenching: Hold at 880℃ for 1.0h, then oil cool;

[0140] 2) Second quenching: Hold at 870℃ for 1.0 h, then oil cool;

[0141] 3) Tempering: Hold at 200℃ for 2.0h, then water-cool.

[0142]

Example 5

[0143] In this embodiment, the chemical composition of the steel bar for the automotive drive shaft, by mass percentage, is: C: 0.20%, Si: 0.25%, Mn: 0.92%, P: 0.010%, S: 0.004%, Cr: 1.09%, Ni: 0.05%, Mo: 0.02%, Ti: 0.06%, Cu: 0.01%, with the remainder being Fe and unavoidable impurities.

[0144] In this embodiment, the steel bars for the automotive drive shaft are smelted in an eco-friendly electric furnace. The specific process route is as follows: eco-friendly electric furnace smelting + LF refining + RH refining + continuous casting → heating furnace heating → rolling → heat holding → heat treatment. The specific process is as follows:

[0145] (1) Ecological electric furnace smelting

[0146] The molten iron content is 38%, and the scrap steel content is 62%. Of the scrap steel, heavy scrap accounts for 45%, carbon structural steel cuts account for 12%, and the remainder is baled automotive steel scrap. The molten iron charging temperature is 1285℃, and the tapping temperature is 1620℃. At tapping, the carbon content is 0.10%, and the phosphorus content is 0.008%. Slag, pre-deoxidizer, and alloying agents are added when the molten steel is about 1 / 4 full. The smelting cycle is 58 minutes, and the furnace oxygen consumption is 21 m³ / min. 3 / t steel. Alloys and their addition amounts are: silicon-manganese alloy 4.0kg / t steel, medium-carbon ferromanganese 6.0kg / t steel, low-carbon ferrochrome 14.0kg / t steel. Slag is bearing steel synthetic slag, with an addition amount of 5.0kg / t steel. Pre-deoxidizer is aluminum wire segments (12mm diameter), with an addition amount of 0.8kg / t steel. Auxiliary materials and their addition amounts are: coke particles 6.6kg / t steel, steel ladle ash 6.0kg / t steel, active lime (30mm particle size) 35kg / t steel, and magnesite (40mm particle size) 13.2kg / t steel.

[0147] (2) LF Refining

[0148] The LF furnace enters at 1520℃ and uses a 35600A high-current heating method for slag formation. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime is added. After refining for 5 minutes, the first sample is taken for chemical composition analysis. Alloys are added according to the chemical composition, and carbon is increased to promote rapid melting and homogenization of the alloys and carbon powder. When the molten steel temperature reaches 1615℃, 1.4 kg / t of diffusion deoxidizer (alumina balls) is added for diffusion deoxidation. The furnace door is closed for 11 minutes. When the molten steel temperature reaches 1630℃, a second sample is taken for chemical composition analysis to confirm the deviation of the content of each chemical element from the target value. After the second sample is taken, the furnace leaves when the molten steel temperature reaches 1648℃. The LF smelting cycle is 47 minutes, with a clearance of 425 mm. The supplementary alloys include: ferrosilicon 0.3 kg / t steel, high-carbon ferromanganese 3.5 kg / t steel, high-carbon ferrochrome 5.9 kg / t steel, ferrotitanium (FeTi70-A) 1.4 kg / t steel, and machined aluminum (10mm×3mm×1mm) 0.42 kg / t steel. The supplementary auxiliary material is: active lime (30mm particle size) 5.0 kg / t steel.

[0149] (3) RH refining

[0150] The inlet temperature was 1640℃, the refining time was 52 minutes, and the argon pressure was controlled at 0.1 MPa before the vacuum pump was started. The molten steel was not exposed due to slight movement of the slag surface. Timing began when the vacuum reached 100 Pa and was maintained for 12 minutes, while the argon pressure was adjusted to 0.3 MPa. After static argon blowing, 0.5 kg / t of covering agent was added, the clearance was 495 mm, and the outlet temperature was 1591℃. After the vacuum was broken, 0.6 kg / t of ladle covering agent, 0.85 kg / t of silicon-calcium alloy cored wire (14 mm diameter), and 0.57 kg / t of sulfur concentrate powder cored wire (13 mm diameter) were added.

[0151] (9) Continuous casting

[0152] The ladle temperature upon arrival is 1587℃, the hydrogen content of the molten steel in the tundish is controlled at 1.4ppm, the casting time is 40min, the superheat is 27℃, the casting speed is 0.46m / min, the entire casting process is protected, and medium carbon steel protective slag is used in the crystallizer, with an addition amount of 3.6kg / t steel.

[0153] (5) Heating

[0154] The billet enters the heating furnace at a temperature of 520℃, the preheating section at 660℃, and is heated for 1.4 hours; the second heating section at 870℃, is heated for 1.3 hours; the first heating section at 1215℃, is heated for 1.4 hours; the soaking section at 1203℃, is heated for 1.3 hours; and the tapping temperature is 1194℃.

[0155] (6) Rolling

[0156] The initial rolling process involves 9 passes, specifically: Turning the steel over → Pass 1: Roll to a width of 408mm, a height of 421mm, and a reduction of 65mm → Pass 2: Roll to a width of 426mm, a height of 351mm, and a reduction of 70mm → Turning the steel over → Pass 3: Roll to a width of 370mm, a height of 362mm, and a reduction of 64mm → Pass 4: Roll to a width of 397mm, a height of 272mm, and a reduction of 90mm → Turning the steel over → Pass 5: Roll to a width of 285mm, a height of 355mm, and a reduction of 64mm → Pass 6 ...6: Roll to a width of 285mm, a height of 355mm, and a reduction of 64mm → Pass 7: Roll to a width of 408mm, a height of 421mm, and a reduction of 65mm → Pass 6: Roll to a width of 408mm, a height of 421mm, and a reduction of 65mm → Pass 6: Roll to a width of 426mm, a height of 351mm, and a reduction of 70mm → Turning the steel over → Pass 6: Roll to a width of 285mm, a height of 355mm, and a reduction of 64mm → Pass 7: Roll to a width of 397mm, a height of 272mm, and a reduction of 90mm → Turn 42mm reduction → 6th pass: rolled to 297mm width, 315mm height, 40mm reduction → 7th pass: rolled to 307mm width, 280mm height, 35mm reduction → 8th pass: rolled to 317mm width, 246mm height, 34mm reduction → Turned over → 9th pass: rolled to 271mm width, 235mm height, 82mm reduction; After being rolled by 3 850mm rolling mills and 1 735mm rolling mill, it enters the continuous rolling mill unit for rolling.

[0157] The continuous rolling process consists of 7 passes: the first pass rolls the material to a height of 229 mm and a width of 245 mm at a speed of 0.27 m / s; the second pass rolls the material to a height of 192 mm and a width of 235 mm at a speed of 0.31 m / s; the third pass rolls the material to a height of 200 mm and a width of 195 mm at a speed of 0.31 m / s; the fourth pass rolls the material to a height of 163 mm and a width of 200 mm at a speed of 0.393 m / s; the fifth pass rolls the material to a height of 169 mm and a width of 176 mm at a speed of 0.499 m / s; the sixth pass rolls the material to a height of 128 mm and a width of 172 mm at a speed of 0.607 m / s; and the seventh pass rolls the material to a height of 142 mm and a width of 142 mm. The finished product is then produced after 7 passes.

[0158] (7) Insulation

[0159] The temperature of the steel in the insulation pit is 585℃, the insulation time is 52 hours, and the temperature when it comes out of the pit is 120℃.

[0160] (8) Heat treatment

[0161] After heat treatment, samples of the steel were taken and subjected to heat treatment, which included the following steps:

[0162] 1) First quenching: Hold at 880℃ for 1.0h, then oil cool;

[0163] 2) Second quenching: Hold at 870℃ for 1.0 h, then oil cool;

[0164] 3) Tempering: Hold at 200℃ for 2.0h, then water-cool.

[0165] Finished product inspection results: The diameter produced in Examples 1-5 is... Taking the standard steel bar as an example, the results of low-magnification microstructure inspection are shown in Table 1, the results of non-metallic inclusion inspection are shown in Table 2, and the mechanical properties are shown in Table 3.

[0166] Table 1 Diameter Low magnification structure of sized steel bars

[0167] Serial Number Generally loose Central loose Ingot segregation General speckled segregation Edge spot-like 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

[0168] Table 2 Diameter Specifications of steel bars and non-metallic inclusions

[0169]

[0170] Table 3 Diameter Specifications of mechanical properties of steel bars

[0171]

[0172] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for producing a steel bar for automotive drive shafts based on ecological electric furnace, characterized in that, The chemical composition of the automobile transmission shaft steel bar is C: 0.18-0.22%, Si: 0.22-0.33%, Mn: 0.85-1.00%, P≤0.015%, S≤0.005%, Cr: 1.05-1.20%, Ni≤0.25%, Mo≤0.10%, Ti: 0.05-0.09%, Cu≤0.15%, and the rest is Fe and inevitable impurities; the production process comprises ecological electric furnace smelting, LF refining, RH refining, continuous casting, casting blank heating, rolling, heat preservation and heat treatment; The ecological electric furnace smelting process is as follows: the proportion of molten iron is 35%-40% and the proportion of scrap steel is 60%-65% by weight; the temperature of molten iron entering the furnace is 1280-1290 DEG C, and the tapping temperature is 1615-1625 DEG C; the C content of molten steel is 0.08%-0.12% and P is less than or equal to 0.010% when tapping; the slag material, pre-deoxidizer and alloy are added when the tapping amount reaches 1 / 4-1 / 3 of the total molten steel amount; the smelting period is 55-65 min, the oxygen consumption of the furnace is 21-22 m 3 / t steel; the alloy and the adding amount are as follows: silicon-manganese alloy 4.0-4.2 kg / t steel, medium-carbon manganese iron 6.0-6.2 kg / t steel, low-carbon chromium iron 14.0-14.2 kg / t steel; the slag material is bearing steel synthetic slag, and the adding amount is 5.0-5.2 kg / t steel; the pre-deoxidizer is aluminum wire segment, and the adding amount is 0.8-0.9 kg / t steel; the auxiliary material and the adding amount are as follows: coke particles 6.5-6.7 kg / t steel, ladle ash 5.8-6.2 kg / t steel, active lime 35-36 kg / t steel, and magnesite 13.0-13.5 kg / t steel; The heat treatment process comprises the following steps: (1) first quenching: quenching temperature 870-890℃, holding time 0.8-1.2h, oil cooling to room temperature; (2) second quenching: quenching temperature 860-880℃, holding time 0.8-1.2h, oil cooling to room temperature; (3) tempering: tempering temperature 190-210℃, holding time 1.8-2.2h, water cooling to room temperature.

2. A process for producing a steel rod for automotive propeller shaft based on ecological electric furnace as claimed in claim 1, wherein, The finished product performance of the automobile transmission shaft steel bar is: tensile strength Rm≥1080MPa, yield strength Rel≥850MPa, elongation A≥10%, reduction of area z≥45%, 5mm notch room temperature longitudinal impact energy KU2≥55J; macrostructure indexes: general porosity≤1.5 level, center porosity≤1.5 level, ingot type segregation≤1.5 level, general spot segregation≤1.0 level, edge spot segregation≤1.0 level; non-metallic inclusion indexes: A type≤2.0 level, B type≤1.5 level, C type≤1.5 level, D type≤1.5 level, DS type≤2.0 level.

3. A process for producing a steel rod for automotive propeller shaft based on ecological electric furnace as claimed in claim 1, wherein, The LF refining process is: the LF inlet temperature is 1515-1525℃, 35000-36000A large current is used to heat and slag, and active lime is additionally added when the slag surface fluctuates and the molten steel and arc are not exposed; the chemical composition is analyzed by sampling for the first time after 5-6min of refining, and alloy is additionally added and carbon is increased; when the molten steel temperature reaches 1610-1620℃, 1.4-1.5kg / t steel of alumina balls is added for diffusion deoxidization; the furnace door is closed for 10-13min, and the chemical composition is analyzed by sampling for the second time when the molten steel temperature reaches 1625-1635℃; after the second sampling, the molten steel temperature reaches 1645-1655℃ when leaving the station; the LF smelting cycle is 45-50min, and the clearance is 420-430mm; the additional alloy and the added amount are: ferrosilicon 0.3-0.32kg / t steel, high-carbon ferromanganese 3.5-3.6kg / t steel, high-carbon ferrochrome 5.8-6.0kg / t steel, ferrotitanium 1.4-1.5kg / t steel, and cutting aluminum 0.4-0.45kg / t steel; additionally, 5-5.2kg / t steel of auxiliary active lime is additionally added.

4. A process for producing a steel rod for automotive propeller shaft based on ecological electric furnace as claimed in claim 1, wherein, The RH refining process is as follows: the temperature of molten steel entering the station is 1635-1645 DEG C, the refining time is 45-55 min; the argon pressure is controlled at 0.1-0.3 MPa before the vacuum pump is started, the timing is started when the vacuum degree reaches 100-110 Pa, and is kept for 10-15 min, and the argon pressure is adjusted to 0.3-0.5 MPa at the same time; after the static argon blowing is finished, the covering agent is added at 0.5-0.6 kg / t steel, and the clearance is kept at 480-520 mm; the temperature of molten steel leaving the station is 1585-1595 DEG C; after the vacuum is broken, the ladle covering agent is added at 0.6-0.62 kg / t steel, the silicon-calcium alloy cored wire is added at 0.84-0.86 kg / t steel, and the sulfur concentrate powder cored wire is added at 0.56-0.58 kg / t steel.

5. A process for producing a steel rod for automotive propeller shaft based on ecological electric furnace as claimed in claim 1, wherein, The continuous casting process is as follows: the temperature of the ladle entering the station is 1580-1590 DEG C, the H content of molten steel in the tundish is controlled to be less than or equal to 2 ppm, the casting time is 38-42 min, the superheat is controlled at 25-30 DEG C, and the drawing speed is 0.45-0.47 m / min; the whole process is protected casting, the mold powder is the medium-carbon steel powder, and the adding amount is 3.6-3.7 kg / t steel.

6. A process for producing a steel rod for automotive propeller shaft based on ecological electric furnace as claimed in claim 1, wherein, The casting blank heating process is as follows: the temperature of the casting blank entering the heating furnace is 500-550 DEG C, the temperature of the preheating section is 660-680 DEG C, and the preheating section heating time is 1.4-1.5 h; the temperature of the second heating section is 850-870 DEG C, and the heating time is 1.3-1.5 h; the temperature of the first heating section is 1210-1240 DEG C, and the heating time is 1.3-1.5 h; the temperature of the soaking section is 1210-1230 DEG C, and the soaking section heating time is 1.3-1.5 h; the steel temperature is 1180-1210 DEG C.

7. A process for producing a steel rod for automotive propeller shaft based on an ecological electric furnace as claimed in claim 1, characterized in that, The rolling process includes the rough rolling process and the continuous rolling process, wherein: The rough rolling process is rolled for 9 passes; the rolling reduction is as follows: turning over the steel → the first pass reduction 65-65.01 mm → the second pass reduction 70-70.01 mm → turning over the steel → the third pass reduction 64-64.01 mm → the fourth pass reduction 90-90.01 mm → turning over the steel → the fifth pass reduction 42-42.01 mm → the sixth pass reduction 40-40.01 mm → the seventh pass reduction 35-35.01 mm → the eighth pass reduction 34-34.01 mm → turning over the steel → the ninth pass reduction 82-82.01 mm; after being rolled by 3 sets of 850 mm rolling mills and 1 set of 735 mm rolling mill, the steel is rolled by the continuous rolling mill group; The continuous rolling process is rolled for 7 passes; the rolling speed is as follows: the first pass rolling speed 0.27-0.272 m / s; the second pass rolling speed 0.31-0.312 m / s; the third pass rolling speed 0.31-0.312 m / s; the fourth pass rolling speed 0.393-0.395 m / s; the fifth pass rolling speed 0.499-0.500 m / s; the sixth pass rolling speed 0.607-0.608 m / s; after being rolled for 7 passes, the finished product is obtained. The size of the billet changes in the roughing process as follows: the first pass is rolled to a width of 408-408.01 mm and a height of 421-421.01 mm; the second pass is rolled to a width of 426-426.01 mm and a height of 351-351.01 mm; the third pass is rolled to a width of 370-370.01 mm and a height of 362-362.01 mm; the fourth pass is rolled to a width of 397-397.01 mm and a height of 272-272.01 mm; the fifth pass is rolled to a width of 285-285.01 mm and a height of 355-355.01 mm; the sixth pass is rolled to a width of 297-297.01 mm and a height of 315-315.01 mm; the seventh pass is rolled to a width of 307-307.01 mm and a height of 280-280.01 mm; the eighth pass is rolled to a width of 317-317.01 mm and a height of 246-246.01 mm; and the ninth pass is rolled to a width of 271-271.01 mm and a height of 235-235.01 mm. The size of the billet changes in the continuous rolling process as follows: the first pass is rolled to a height of 229-229.01 mm and a width of 245-245.01 mm; the second pass is rolled to a height of 192-192.01 mm and a width of 235-235.01 mm; the third pass is rolled to a height of 200-200.01 mm and a width of 195-195.01 mm; the fourth pass is rolled to a height of 163-163.01 mm and a width of 200-200.01 mm; the fifth pass is rolled to a height of 169-169.01 mm and a width of 176-176.01 mm; the sixth pass is rolled to a height of 128-128.01 mm and a width of 172-172.01 mm; the seventh pass is rolled to a height of 142-142.01 mm and a width of 142-142.01 mm.

8. A method of producing a steel rod for automotive propeller shafts based on an ecological electric furnace according to claim 1, characterized in that, In the holding process, the temperature of the billet in the holding pit is greater than or equal to 570 DEG C, the holding time is 48-55 h, and the temperature of the billet when leaving the holding pit is less than or equal to 150 DEG C.

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