A production method for high-quality carbon structural steel for automobile transmission system

Abstract

The present invention belongs to the field of metallurgy and discloses a method for preparing high-quality carbon structural steel for automobile transmission systems. The carbon structural steel comprises, by weight, the following components: C 0.45-0.49%, Si 0.10-0.40%, Mn 0.70-0.85%, P ≤ 0.025%, S 0.008-0.025%, Al 0.015-0.040%, Cu ≤ 0.25%, Cr 0-0.35%, O ≤ 0.0015%, and a Di value of 33-42 mm. By rationally designing the smelting process (converter, LF refining, and RH vacuum treatment to improve molten steel purity), the continuous casting process, and the rolling process (finish rolling and controlled cooling), the castability of the molten steel and the material's Ds-type inclusions are controlled. The dimensional accuracy and surface quality of the round steel are improved, and the turning and fine grinding processes can be eliminated, allowing the use of black bar steel instead of silver-bright steel.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallurgy, and relates to a high-quality carbon structural steel for automobile transmission systems and a production method thereof, and in particular to a steelmaking and rolling process for the high-quality carbon structural steel for automobile transmission systems. Background Art

[0002] Carbon structural steels generally do not undergo heat treatment and are used directly as supplied. Q195, Q215, and Q235 steels typically have a low carbon mass fraction, good weldability, good ductility, and toughness, and possess a certain strength. They are often rolled into thin plates, rebar, and welded steel pipes for use in structures such as bridges and buildings, and in the manufacture of common screws and nuts. Q255 and Q275 steels have a slightly higher carbon mass fraction, resulting in higher strength, good ductility and toughness, and are weldable. They are typically rolled into profiles, bars, and plates for structural components, as well as for the manufacture of connecting rods, gears, couplings, pins, and other parts in simple machinery.

[0003] Compared to ordinary carbon structural steel, high-quality carbon structural steel contains lower levels of sulfur, phosphorus, and other non-metallic inclusions. Based on carbon content and application, these steels are broadly divided into three categories: ① Low carbon steels with less than 0.25% carbon are considered low-carbon steels. Steels like 08F and 08Al, with carbon contents below 0.10%, are widely used for deep-drawn parts such as automobiles and cans due to their excellent deep-drawability and weldability. 20G is the primary material for ordinary boilers. Low carbon steels are also widely used as carburizing steels in the machinery manufacturing industry. ② Medium carbon steels with carbon contents between 0.25% and 0.60% are primarily used in the quenched and tempered state to make parts for the machinery manufacturing industry. ③ High carbon steels with carbon contents greater than 0.6% are primarily used in the manufacture of springs, gears, rollers, and other applications. Based on manganese content, these steels can be further divided into two groups: those with normal manganese content (0.25% to 0.8%) and those with higher manganese content (0.7% to 1.0% and 0.9% to 1.2%). Manganese can improve the quench-hardening ability of steel, strengthen the ferrite and improve the yield strength, tensile strength and wear resistance of steel. Usually mark "Mn" is added to the designation of steel with high manganese content, such as 15Mn and 20Mn to distinguish it from carbon steel with normal manganese content.

[0004] Furthermore, with the trend toward lightweight and energy-efficient vehicles, carbon structural steel 45# is being modified with an appropriate increase in Mn and a certain amount of Cr to improve hardenability. After induction hardening, it is used to manufacture core components such as automotive drive shafts and axles. However, optimizing the composition to achieve the appropriate hardenability, achieving a material with high outer surface hardness and good core toughness after surface induction hardening, while also improving surface quality and dimensional accuracy, and replacing silver-bright material with black-skin material to eliminate the surface peeling process, has become a major challenge for the industry. Summary of the Invention

[0005] In response to the technical shortcomings of carbon steel 45, the present invention proposes a high-quality carbon structural steel (XC45) with uniform structure and excellent hardenability and its production process, which is used to produce automobile half-axles, drive shafts and other parts, and uses black skin material instead of silver bright material (the produced structural steel does not need to be peeled or ground and can be used directly), ultimately achieving the same use effect.

[0006] The purpose of the present invention is mainly achieved through the following technical solutions:

[0007] The present invention relates to high-quality carbon structural steel for automobile transmission systems and a production method thereof. By optimizing and adjusting elements and matching a suitable finishing rolling process, the metallographic structure of the high-quality carbon structural steel is uniform, the purity of the molten steel is high, and the dimensional accuracy is excellent, so that black skin material can be directly used instead of silver bright material.

[0008] The object of the present invention is achieved through the following technical solutions:

[0009] The invention discloses a high-quality carbon structural steel for automobile transmission systems. The carbon structural steel comprises the following components by weight: C 0.45-0.49%, Si 0.10-0.40%, Mn 0.70-0.85%, P≤0.025%, S 0.008-0.025%, Al 0.015-0.040%, Cu≤0.25%, Cr 0-0.35%, O≤0.0015%, Di value 33-42 mm, and the remainder is Fe and unavoidable impurities.

[0010] Preferably, the carbon structural steel has the following components by weight: C 0.46-0.48%, Si 0.27-0.35%, Mn 0.75-0.85%, Cr 0.10-0.15%, P≤0.015%, S 0.010-0.020%, Al0.020-0.030%, Cu≤0.10%, O≤0.0012%, Di value 36-42 mm, Ti≤0.0030%, and the balance is Fe and unavoidable impurities.

[0011] The production process includes converter smelting, LF refining, RH vacuum treatment, continuous casting and rolling. The process flow is as follows:

[0012] (1) For the converter, a furnace-front quick separation system is used to automatically detect the composition, shortening the detection time from the original 5-8 minutes of manual detection to 2-3 minutes, improving the endpoint hit rate, controlling the endpoint carbon content to 0.15-0.35%, and controlling the endpoint phosphorus content to ≤0.011%. An infrared monitoring system is used during the converter tapping process to prevent slag from being discharged during tapping, and to prevent over-oxidation of tapping, controlling the oxygen content of tapping to ≤600ppm;

[0013] (2) During the converter tapping process, deoxidizing materials are added in sequence: 1.0-1.2 kg / ton of aluminum iron, 150 kg / furnace of silicon carbide; recarburizers and alloy materials: low aluminum and low titanium ferrosilicon, low carbon ferromanganese, and low titanium ferrochrome;

[0014] (3) In the LF refining process, medium and low basicity slag is used. Calcium carbide is used for deoxidation in the first 20 minutes of refining to control the slag basicity to 2.0-3.0 to achieve deoxidation of molten steel; in the middle and late stages (after 20 minutes of refining), SiC is used to deoxidize the slag, reduce the slag basicity, and increase silicon. Silicon-containing alloys are not used to increase silicon. The slag basicity in the middle and late stages is controlled to 1.5-2.0 to achieve sulfur conservation operation and control the S content before LF to 0.015-0.025%. This can increase the fluidity of the slag, improve the slag's ability to absorb inclusions, and eliminate the sulfur addition process, thereby reducing the large amount of foreign inclusions brought in by the addition of sulfur iron. At the same time, the LF process strictly adjusts the alloy composition to ensure that the Di value is controlled at 36-42 mm, and the Di value is used to guide the adjustment of the alloy element content;

[0015] (4) The RH process strengthens the degassing and inclusion removal of molten steel, ensuring the ultimate vacuum treatment time of 16 to 25 minutes. The alloy composition shall not be adjusted after vacuum treatment. The feeding amount of silicon calcium wire in the first furnace is 50 to 80 meters to improve the castability of molten steel and ensure the smooth progress of production. The continuous casting furnace does not carry out calcium treatment, thereby improving the purity of molten steel and controlling Ds type inclusions. The soft argon blowing time after vacuum is controlled to 20 to 40 minutes, which is conducive to promoting the floating of inclusions.

[0016] (5) Continuous casting uses 220*260mm 2 In terms of cross-section, the first batch of ingots was changed to national standard 45 steel for general mechanical purposes. In order to improve the surface quality of the ingots, the pulling speed was 0.9-1.0m / min, weak cooling was used for secondary cooling, and the secondary cooling water volume was controlled at 0.17-0.19L / kg; argon blowing plug rods and argon blowing nozzles were used in continuous casting to improve the castability of the molten steel, eliminate the need for calcium treatment, and facilitate the control of Ds-type inclusions.

[0017] (6) To prevent decarburization during the steel rolling process, the temperature of the entire heating process is controlled not to exceed 1180°C (preferably 1100-1180°C), and the entire heating time is not to exceed 210 minutes.

[0018] (7) The finishing process is adopted, and the roller ring is used in the early stage. The amount of steel passed before rolling the steel grade is controlled to not exceed 800 tons. The roller ring is adjusted online to control the size deviation range before final rolling: -0.25~+0.25mm. The final rolling is carried out using KOCKS three-roll rolling (generally, the KOCKS movement is replaced and the movement with excellent quality in the early stage is selected). Through online adjustment, the final size deviation of the finished product is controlled to -0.10~+0.15mm, thereby reducing the quality deviation of the user's blanking. The use of thermal eye equipment is conducive to infrared online flaw detection of red steel, and round steel with surface defects exceeding 0.1mm is timely selected. Finally, black skin material is used instead of silver bright material, which saves the user a turning and fine grinding process and saves a lot of cost.

[0019] (8) Achieve low-temperature rolling and control the temperature of the cooling bed on the rolled material to 750-780℃, so as to prevent surface defects such as scratches on the cooling bed rollers due to the high temperature of the cooling bed and the softening of the rolled material.

[0020] The beneficial effects of the present invention are as follows: considering that 45 steel has poor hardenability and poor purity of molten steel, especially Ds-type inclusions easily exceed the standard, and conventional rolling dimensional accuracy is insufficient, requiring peeling and fine grinding before use. The present invention has the following features:

[0021] ①. The chemical composition was optimized and adjusted, and the hardenability index Di value was strictly controlled, especially the hardenability-influencing elements such as Mn and Cr.

[0022] ②. The converter adopts a fast separation system to automatically and accurately determine the composition, thereby improving the hit rate of the endpoint composition. LF refining adopts a medium-low basicity slag system, eliminating the sulfur addition process, preventing the molten steel from being contaminated by sulfur addition and achieving precise control of the composition. The RH vacuum process improves the purity of the molten steel by degassing, removing inclusions, and eliminating the calcium treatment process, especially reducing Ds-type inclusions.

[0023] ③. During the continuous casting process, argon-blown plugs and nozzles are used to improve the castability of the molten steel and avoid Ds-type inclusions caused by calcium treatment; appropriate casting speed and weak cooling are used to ensure the surface quality of the sulfur-containing steel ingot.

[0024] ④ During the rolling heating process, surface decarburization is reduced by controlling the heating temperature and time. A KOCKS three-roll mill and a finishing process are used to control dimensional deviations in the finished product. Furthermore, low-temperature rolling is employed to prevent surface scratches and facilitate online flaw detection of round steel using infrared thermal eye equipment. These efforts stabilize the material's hardenability, improve molten steel purity, enhance the dimensional accuracy of the finished product, reduce decarburization and surface scratches, eliminate processes such as calcium treatment and sulfur addition, and eliminate a peeling and fine grinding step, ultimately improving the material's user performance. DETAILED DESCRIPTION

[0025] The present invention is described in detail below with reference to specific examples, wherein the conditions not limited thereto are XC45 conventional conditions.

[0026] Example 1

[0027] A high-quality carbon structural steel for automobile transmission systems has the following chemical composition by weight: C 0.48%, Si 0.31%, Mn 0.82%, Cr 0.14%, Di value 37.6 mm, Al 0.025%, P 0.011%, S 0.021%, Cu 0.02%, O 0.0007%, Ti 0.0013%, and the balance Fe.

[0028] The process includes 120t converter smelting, LF refining, RH vacuum treatment, continuous casting and rolling.

[0029] (1) Converter smelting: The composition is automatically detected by the furnace front fast separation system. The carbon content of the converter steel is 0.11%, the phosphorus content of the steel is 0.009%, and the oxygen content of the steel is 573ppm.

[0030] (2) During the tapping process of the converter, 130 kg of aluminum iron and 150 kg of silicon carbide are added. Silicon manganese alloy 1450

[0031] ±20 kg, ferrosilicon alloy 250±10 kg, high carbon ferrochrome alloy 270±10 kg, recarburizer 260

[0032] ±10 kg.

[0033] (3) In the LF refining process, calcium carbide is used for deoxidation in the early stage of refining to control the slag basicity to 2.3 in the early stage to achieve deoxidation of molten steel; in the middle and late stages, the slag basicity is 1.6, and the elements C, Cr, Si, Mn, Al, and S are adjusted to their proper levels during refining.

[0034] (4) RH vacuum treatment, the treatment time is 17 minutes at high vacuum (≤67Pa); after vacuum treatment, 55 meters of silicon calcium wire is fed into the molten steel for modification treatment, and the soft argon blowing time is 20-40 minutes.

[0035] (5) Continuous casting: The continuous casting process adopts protective casting, the continuous casting section is 200mm×260mm, the continuous casting speed is controlled at 0.95m / min, and the secondary cooling water volume is controlled at 0.18L / kg.

[0036] (6) Rolling process: The highest soaking section temperature of the heating furnace is controlled at 1175°C, the heating time is 180 min, and the upper cooling bed temperature is controlled at 765°C. The size of the 56mm round steel after rolling is 55.97~56.08mm, and the size deviation is -0.03~+0.08mm.

[0037] Example 2

[0038] A high-quality carbon structural steel for automobile transmission systems has the following chemical composition by weight: C 0.46%, Si 0.27%, Mn 0.80%, Cr 0.10%, Di value 37.3 mm, Al 0.023%, P 0.012%, S 0.022%, Cu 0.02%, O 0.0006%, Ti 0.0017%, and the balance Fe.

[0039] The process includes 120t converter smelting, LF refining, RH vacuum treatment, continuous casting and rolling.

[0040] (1) Converter smelting: The carbon content of converter steel is 0.15%, the phosphorus content of steel is 0.010%, and the oxygen content of molten steel is 554ppm.

[0041] (2) During the converter tapping process, 140 kg of ferroaluminum, 150 kg of silicon carbide, 1430 ± 20 kg of silicon-manganese alloy, 200 ± 10 kg of ferrosilicon alloy, 180 ± 10 kg of high-carbon ferrochromium alloy, and 240 ± 10 kg of recarburizer are added.

[0042] (3) During the LF refining process, the slag basicity is controlled at 2.6 in the early stage and 1.8 in the later stage. At the same time, the elements C, Cr, Si, Mn, Al, and S are adjusted to their proper positions through refining.

[0043] (4) RH vacuum treatment, the treatment time is 18 minutes in high vacuum (≤67Pa); after vacuum treatment, 50 meters of silicon calcium wire is fed into the molten steel for modification treatment.

[0044] (5) Continuous casting: The continuous casting process adopts protective casting, the continuous casting section is 200mm×260mm, the continuous casting speed is controlled at 0.95m / min, and the secondary cooling water volume is controlled at 0.18L / kg.

[0045] (6) Rolling process: The highest soaking section temperature of the heating furnace is controlled at 1162°C, the heating time is 185 min, the upper cooling bed temperature is controlled at 766°C, and the size of the 56mm round steel after rolling is 56.0~56.10mm, with a size deviation of 0~+0.10mm.

[0046] Example 3

[0047] A high-quality carbon structural steel for automobile transmission systems has the following chemical composition by weight: C 0.48%, Si 0.35%, Mn 0.75%, Cr 0.14%, Di value 37.9 mm, Al 0.020%, P 0.010%, S 0.019%, Cu 0.02%, O 0.0008%, Ti 0.0015%, and the balance Fe.

[0048] The process includes 120t converter smelting, LF refining, RH vacuum treatment, continuous casting and rolling.

[0049] (1) Converter smelting: The carbon content of converter steel is 0.20%, the phosphorus content of steel is 0.008%, and the oxygen content of molten steel is 520ppm.

[0050] (2) During the tapping process of the converter, 135 kg of ferroaluminum, 150 kg of silicon carbide, 1350 ± 20 kg of silicon manganese alloy, 300 ± 10 kg of ferrosilicon alloy, 270 ± 10 kg of high carbon ferrochromium alloy, and 270 ± 10 kg of recarburizer are added.

[0051] (3) During the LF refining process, the slag basicity is controlled at 2.6 in the early stage and 1.6 in the later stage. At the same time, the elements C, Cr, Si, Mn, Al, and S are adjusted to their proper positions through refining.

[0052] (4) RH vacuum treatment, the treatment time is 19 minutes in high vacuum (≤67Pa); after vacuum treatment, 50 meters of silicon calcium wire is fed into the molten steel for modification treatment.

[0053] (5) Continuous casting: The continuous casting process adopts protective casting, the continuous casting section is 200mm×260mm, the continuous casting speed is controlled at 0.95m / min, and the secondary cooling water volume is controlled at 0.18L / kg.

[0054] (6) Rolling process: The highest soaking section temperature of the heating furnace is controlled at 1160°C, the heating time is 178 min, and the upper cooling bed temperature is controlled at 760°C. The size of the 56mm round steel after rolling is 55.96~56.05mm, and the size deviation is -0.04~+0.05mm.

[0055] Example 4

[0056] A high-quality carbon structural steel for automobile transmission systems has the following chemical composition by weight: C 0.46%, Si 0.27%, Mn 0.85%, Cr 0.15%, Di value 39.3 mm, Al 0.027%, P 0.013%, S 0.017%, Cu 0.03%, O 0.0008%, Ti 0.0014%, and the balance Fe.

[0057] The process includes 120t converter smelting, LF refining, RH vacuum treatment, continuous casting and rolling.

[0058] (1) Converter smelting: The carbon content of converter steel is 0.22%, the phosphorus content of steel is 0.0011%, and the oxygen content of molten steel is 523ppm.

[0059] (2) During the converter tapping process, 135 kg of ferroaluminum, 150 kg of silicon carbide, 1500 ± 20 kg of silicon-manganese alloy, 180 ± 10 kg of ferrosilicon alloy, 290 ± 10 kg of high-carbon ferrochromium alloy, and 235 ± 10 kg of recarburizer are added.

[0060] (3) During the LF refining process, the slag basicity is controlled at 2.7 in the early stage and 1.8 in the later stage. At the same time, the elements C, Cr, Si, Mn, Al, and S are adjusted to their proper positions through refining.

[0061] (4) RH vacuum treatment, the treatment time is 17 minutes in high vacuum (≤67Pa); after vacuum treatment, 60 meters of silicon calcium wire is fed into the molten steel for modification treatment.

[0062] (5) Continuous casting: The continuous casting process adopts protective casting, the continuous casting section is 200mm×260mm, the continuous casting speed is controlled at 0.95m / min, and the secondary cooling water volume is controlled at 0.18L / kg.

[0063] (6) Rolling process: The highest soaking section temperature of the heating furnace is controlled at 1155°C, the heating time is 175 min, and the upper cooling bed temperature is controlled at 758°C. The size of the 56mm round steel after rolling is 55.98~56.10mm, and the size deviation is -0.02~+0.10mm.

[0064] Comparative Example 1

[0065] Comparative Example 1 is different from Example 1 in that the composition is adjusted by reducing C 0.44%, Si 0.20%, Mn 0.70%, Cr 0.10%, and the Di value is controlled to 32 mm. Other operations are the same as Example 1.

[0066] Comparative Example 2

[0067] Comparative Example 2 is different from Example 1 in that low-aluminum, low-titanium ferrosilicon and low-titanium ferrochrome are not used, but ordinary ferrosilicon and high-carbon ferrochrome are used instead. Other operations are the same as those in Example 1.

[0068] Comparative Example 3

[0069] Compared with Example 1, Comparative Example 3 differs in that: the entire refining process uses high-basicity slag refining, the basicity is controlled at 6.2, and other operations are the same as Example 1.

[0070] Comparative Example 4

[0071] Comparative Example 4 is different from Example 1 in that low-temperature rolling is not performed during the rolling process, the upper cooling bed temperature is controlled at 890° C., and other operations are the same as in Example 1.

[0072] Comparative Example 5

[0073] Comparative Example 5 is different from Example 1 in that: no finish rolling is performed, the round steel size is controlled to be 55.65 to 56.37 mm, the size deviation is -0.35 to +0.37 mm, and other operations are the same as Example 1.

[0074] Comparative Example 6

[0075] Compared with Example 1, Comparative Example 6 differs in that the maximum temperature of the entire heating process is controlled to be 1200° C., the entire heating time is 240 min, and other operations are the same as Example 1.

[0076] The comprehensive performance indicators of Examples 1 to 4 of the present invention and Comparative Examples 1 to 5 are compared in Table 1 below:

[0077] Table 1 Comprehensive performance comparison

[0078]

[0079]

[0080] The results show that: through the reasonable optimization design of the composition, especially the reasonable control of the Di value, the hardenability of the material fully meets the user's requirements. The smelting process strengthens the control of the molten steel purity, and the Ds inclusion level that affects the service life of the material is controlled to level 0, reaching the domestic leading level. The rolling process adopts a controlled cooling process to reduce the scratch rate of the product. In addition, the product dimensional accuracy is controlled within -0.1 to +0.1 mm through fine rolling. At the same time, defective materials are picked out through online flaw detection with infrared thermal eyes, which can save a turning and fine grinding process, save materials, reduce costs, improve production efficiency, and enhance corporate benefits.

[0081] Unless otherwise specified, the raw materials and equipment used in the present invention are commonly used in the art; unless otherwise specified, the methods used in the present invention are conventional methods in the art. The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications to the above embodiments based on the technical essence of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for producing high-quality carbon structural steel for automobile transmission systems, characterized in that: The carbon structural steel has the following components by weight: C 0.45-0.49%, Si 0.10-0.40%, Mn 0.70-0.85%, P≤0.025%, S 0.008-0.025%, Al 0.015-0.040%, Cu≤0.25%, Cr 0-0.35%, O≤0.0015%, Di value 33-42 mm, balance Fe and unavoidable impurities; The preparation method comprises: (1) In converter smelting, a furnace-front quick separation system is used to automatically detect the composition, controlling the endpoint carbon content to 0.10-0.35%, and the endpoint phosphorus content to ≤0.011%. An infrared monitoring system is used during the converter tapping process to control the oxygen content of the tapped steel to ≤600ppm. (2) Deoxidizing materials, carburizers and alloy materials are added in sequence during the converter tapping process; in order to control the titanium content in the steel, alloy materials used are low-aluminum and low-titanium ferrosilicon, low-carbon ferromanganese and low-titanium ferrochrome; (3) LF refining process: In the early stage of refining, calcium carbide is used for deoxidation, and the slag basicity is controlled at 2.0-3.0 to achieve deoxidation of molten steel; in the middle and late stages, SiC is used for slag deoxidation, reducing slag basicity and increasing silicon. Silicon-containing alloys are not used to increase silicon. The slag basicity in the middle and late stages is controlled at 1.5-2.0, and the S content before LF is controlled at 0.015-0.025%. At the same time, the alloy composition is adjusted during the LF process to ensure that the Di value is controlled at 36-42 mm, and the Di value is used to guide the adjustment of the alloy element content; (4) RH vacuum treatment, control the vacuum degree ≤ 67pa, vacuum treatment time 16 to 25 minutes, the alloy composition shall not be adjusted after vacuum treatment, silicon calcium wire is fed into the first furnace to ensure the castability of molten steel, the continuous casting furnace is not subjected to calcium treatment, and the soft argon blowing time after vacuum is controlled is 20 to 40 minutes; (5) The continuous casting adopts 220*260mm2 cross section, the first cast billet is changed to national standard 45 steel for general mechanical use, the casting speed is controlled at 0.9-1.0m / min, the secondary cooling water volume is 0.17-0.19L / kg; the continuous casting adopts argon blowing plug rod and argon blowing nozzle; (6) The temperature of the entire heating process during the steel rolling process shall not exceed 1180°C, and the entire heating time shall not exceed 210 minutes; (7) The finishing rolling process is adopted, and the early roller ring is used to control the amount of steel passed before rolling the steel grade to no more than 800 tons. The roller ring is adjusted online to control the size deviation range before final rolling: -0.25~+0.25mm. The final rolling is carried out using KOCKS three-roll rolling, and the final size deviation of the finished product is controlled by online adjustment to -0.10~+0.15mm. The thermal eye equipment is used to facilitate infrared online flaw detection of red steel and remove round steel with surface defects exceeding 0.1mm. (8) Low temperature rolling: control the temperature of the cooling bed on the rolled material to 750-780℃.

2. The method for producing high-quality carbon structural steel for automobile transmission systems according to claim 1, characterized in that: The composition of carbon structural steel by weight percentage is: C 0.46~0.48%, Si 0.27~0.35%, Mn 0.75~0.85%, Cr 0.10~0.15%, P≤0.015%, S 0.010~0.020%, Al 0.020~0.030%, Cu≤0.10%, O≤0.0012%, Di value 36~42mm, Ti≤0.0030%, and the balance is Fe and inevitable impurities.

3. The method for producing high-quality carbon structural steel for automobile transmission systems according to claim 1, characterized in that: In step (2), the deoxidizing materials are 1.0-1.2 kg / ton of aluminum iron and 150 kg / furnace of silicon carbide.

4. The method for producing high-quality carbon structural steel for automobile transmission systems according to claim 1, characterized in that: Step (4) After RH vacuum treatment, 50-80 meters of calcium silicon wire is fed into the first furnace.

5. The method for producing high-quality carbon structural steel for automobile transmission systems according to claim 1, characterized in that: Step (6) The steel rolling process controls the temperature of the entire heating process to 1100-1180°C.

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