CN109182909B - Medium carbon steel for automobile steering system and production method thereof - Google Patents
Medium carbon steel for automobile steering system and production method thereof Download PDFInfo
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- CN109182909B CN109182909B CN201811190024.2A CN201811190024A CN109182909B CN 109182909 B CN109182909 B CN 109182909B CN 201811190024 A CN201811190024 A CN 201811190024A CN 109182909 B CN109182909 B CN 109182909B
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/064—Dephosphorising; Desulfurising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D7/00—Modifying the physical properties of iron or steel by deformation
- C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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Abstract
The invention belongs to the technical field of production of steel for automobile structures, and particularly relates to medium carbon steel for an automobile steering system and a production method thereof. Aiming at the problems of high cost, complex process, poor mechanical property and the like of the existing medium carbon steel for producing the automobile steering system, the invention provides the medium carbon steel for the automobile steering system, which comprises the following chemical components: according to weight percentage, C is 0.20-0.30%, Mn: 1.0% -2.0%, Si: 0.05 to 0.30 percent of the total weight of the alloy, less than or equal to 0.020 percent of P, less than or equal to 0.010 percent of S, and the balance of Fe and inevitable impurities. The invention also provides a production method of the medium carbon steel, which sequentially comprises the steps of smelting, continuous casting, heating, rough rolling, finish rolling, laminar cooling and coiling, wherein the continuous casting adopts low superheat degree and constant-speed casting. The invention adopts a component system of C-Mn steel, reduces Si content, and obtains steel with better mechanical property through low superheat degree casting, constant speed continuous casting, controlled rolling and controlled cooling processes. The invention has simple process and is suitable for popularization and application.
Description
Technical Field
The invention belongs to the technical field of production of steel for automobile structures, and particularly relates to medium carbon steel for an automobile steering system and a production method thereof.
Background
The automobile steering system is used for controlling the driving direction of an automobile, and the tail end of a rotating shaft of an automobile steering wheel is connected with a steering tie rod and a steering knuckle so as to realize the functions and effects of synchronizing wheels on two sides and adjusting toe-in. The automobile steering system is an important safety part of an automobile, the performance and the reliability of the automobile steering system directly influence the driving safety of the automobile, once the automobile steering system is deformed or broken, the automobile steering or driving function is slightly failed, and the safety accident is directly caused. At present, medium carbon quenched and tempered steel and non-quenched and tempered steel are widely applied to automobile steering systems, wherein noble alloys such as V, Mo and Cr are added to the quenched and tempered steel, and modulation heat treatment is assisted to form structures such as tempered sorbite, and finished products of the tempered sorbite have good strength and toughness and meet the requirements of steel for automobile transmission systems. However, in recent years, the proportion of non-heat treated steel in steel for automobile steering systems has increased significantly due to the high alloy cost and process cost.
CN100478480A discloses a high-performance low-cost non-quenched and tempered steel, which adopts the components of C, Mn steel, adds a small amount of Al for deoxidation, refines crystal grains at the same time, and improves the strong plasticity through controlled rolling and controlled cooling. However, since AlN has a weak effect of refining grains, the grain size is 5 to 9 grades, and grains are coarse, which may cause poor formability and affect use.
CN10133363A discloses a low-carbon bainite type Nb-V composite microalloyed non-quenched and tempered steel and a preparation method thereof, wherein the Nb-V microalloyed non-quenched and tempered steel is used for replacing non-quenched and tempered steel only containing V, and compared with ferrite-pearlite non-quenched and tempered steel, the toughness is higher on the same strength level. However, Nb in the invention belongs to expensive metal, so that the alloy cost is greatly increased, and the bainite steel process control window is narrow.
CN103668004A discloses a preparation method of hot rolled steel for automobile transmission shaft pipes, which produces steel grades with high strength, good toughness and good service performance by optimizing alloy components and adjusting a manufacturing process, but the alloy components are complex, contain various micro-alloy elements such as Cu, Ag, Be, Ga, Tb, Sc, Sb and the like, and meanwhile, the slab heating system is complex and the process popularization is poor.
CN103266287A discloses a medium carbon ferrite-pearlite type non-quenched and tempered steel and a manufacturing method thereof, wherein the strength and plasticity index of hot rolled steel reaches the 40Cr or 40Mn quenched and tempered steel level without modulation heat treatment, but the invention aims at rod and wire materials and has limitation in production process.
At present, medium carbon steel equipment and process applied to automobile transmission and steering systems have poor adaptability, or a large number of microalloy elements are added to increase the toughness of a steel plate, so that the alloy cost is high, or heat treatment is required to increase the production process cost.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the existing method for producing the medium carbon steel for the automobile steering system has the problems of high cost, complex process, poor mechanical property and the like.
The technical scheme for solving the technical problems comprises the following steps: provides medium carbon steel for an automobile steering system. The chemical components are as follows: according to weight percentage, C is 0.20-0.30%, Mn: 1.0% -2.0%, Si: 0.05 to 0.30 percent of the total weight of the alloy, less than or equal to 0.020 percent of P, less than or equal to 0.010 percent of S, and the balance of Fe and inevitable impurities.
Wherein the crystalline phase structure of the medium carbon steel for the automobile steering system is a ferrite-pearlite structure, and the grain size is more than or equal to 10 grades.
The invention also provides a production method of the medium carbon steel for the automobile steering system, which sequentially comprises the steps of smelting, continuous casting, heating, rough rolling, finish rolling, laminar cooling and coiling;
smelting in a converter, refining in an LF furnace, performing vacuum treatment in an RH furnace, and feeding a calcium wire;
the continuous casting adopts low superheat degree and constant-speed casting;
the heating temperature is 1150-1250 ℃, and the heating time is 3-5 h; the rough rolling is 5-7 passes of rolling, and the finish rolling is 6-7 passes of rolling; and carrying out laminar cooling after finish rolling, wherein the final cooling temperature is 550-650 ℃.
Further, in the production method of the medium carbon steel for the automobile steering system, the molten steel is desulfurized by producing the reducing slag during refining in the LF furnace. Further, argon blowing treatment is carried out during RH vacuum treatment, and the argon blowing time is more than 8 min.
Further, in the production method of the medium carbon steel for the automobile steering system, the temperature of the tundish molten steel is 1500-1550 ℃ during molten steel continuous casting, and the drawing speed is 0.50-1.50 m/min.
Further, in the production method of the medium carbon steel for the automobile steering system, the thickness of a plate blank cast by the molten steel is 200-250 mm, the deformation of each pass of rough rolling is required to be more than or equal to 15%, and the thickness of the plate blank after rough rolling is 40-60 mm.
Further, in the production method of the medium carbon steel for the automobile steering system, the finish rolling start temperature is 1000-1100 ℃, and the finish rolling temperature is 800-900 ℃.
Further, in the production method of the medium carbon steel for the automobile steering system, the thickness of the plate blank after the steel plate is finish rolled is 5-10 mm.
Further, in the production method of the medium carbon steel for the automobile steering system, the laminar cooling speed is 10-30 ℃/s.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a medium carbon steel for an automobile steering system and a production method thereof, wherein a C-Mn steel component system is adopted, the Si content is controlled to be lower, the steel with high strength, good toughness, good room temperature bending property and good low-temperature impact toughness is obtained by optimizing a smelting process and adjusting a controlled rolling and controlled cooling process, the yield strength is more than or equal to 400MPa, the tensile strength is more than or equal to 520MPa, the elongation is more than or equal to 20%, the 180-degree cold bending test d is qualified as 2a, the impact energy at-10 ℃ is more than or equal to 40J (the sample size is 7.5 multiplied by 10 multiplied by 55mm), the grain size is more than or equal to 10 grade, and the metallographic structure is ferrite-pearlite. The preparation method of the carbon steel has strong technological adaptability, does not need heat treatment, has simple operation and low cost, and has obvious economic benefit.
Drawings
FIG. 1 is a metallographic structure diagram of a medium carbon steel for an automobile steering system prepared in example 1;
FIG. 2 is a metallographic structure diagram of medium carbon steel for an automobile steering system prepared in example 2;
FIG. 3 is a metallographic structure diagram of a medium carbon steel for an automobile steering system prepared in comparative example 3;
FIG. 4 is a metallographic structure diagram showing a medium carbon steel for an automobile steering system prepared in comparative example 4.
Detailed Description
The invention provides medium carbon steel for an automobile steering system, which comprises the following chemical components: according to weight percentage, C is 0.20-0.30%, Mn: 1.0% -2.0%, Si: 0.05 to 0.30 percent of the total weight of the alloy, less than or equal to 0.020 percent of P, less than or equal to 0.010 percent of S, and the balance of Fe and inevitable impurities.
Wherein the crystalline phase structure of the medium carbon steel for the automobile steering system is a ferrite-pearlite structure, and the grain size is more than or equal to 10 grades.
In the medium carbon steel for the automobile steering system, C is one of the strengthening elements, and in order to ensure the strength and rigidity of the steel for the automobile steering system and not reduce the toughness and the formability of the steel, the content of C is controlled to be 0.20-0.30%; the main effect of Mn is solid solution strengthening, and meanwhile, the plasticity of steel is improved, the Mn content is controlled to be 1.0-2.0%, but the higher Mn content can cause casting blank segregation and influence the toughness of steel, so the steelmaking process is strictly controlled and the segregation level is reduced; the invention reduces the content of Si, inhibits the diffusion of C element in austenite, and avoids the segregation of C element at the grain boundary in the process of diffusing from austenite to ferrite to form a cementite structure. The Si content is controlled to be 0.005-0.50%, and the forming performance is improved; s is severely segregated in steel, reduces the plasticity of the steel at high temperature and is a harmful element. It exists as FeS with a lower melting point, which precipitates at the primary grain boundaries as the steel solidifies. When the steel is rolled at 1100-1200 ℃, FeS on a grain boundary is melted, the bonding force between crystal grains is greatly weakened, and the hot brittleness phenomenon of the steel is caused, so that S is strictly controlled within 0.010%.
According to the invention, the steel with high strength, good toughness, good room temperature bending performance and good low-temperature impact toughness can be obtained by accurately controlling the content of each component in the steel.
The invention provides a production method of medium carbon steel for an automobile steering system, which sequentially comprises the steps of smelting, continuous casting, heating, rough rolling, finish rolling, laminar cooling and coiling;
wherein the smelting adopts a converter for smelting, then adopts an LF furnace for refining, then adopts an RH furnace for vacuum treatment, and feeds a calcium wire;
the continuous casting adopts low superheat degree and constant-speed casting;
the heating temperature is 1150-1250 ℃, and the heating time is 3-5 h; the rough rolling is 5-7 passes of rolling, and the finish rolling is 6-7 passes of rolling; and carrying out laminar cooling after finish rolling, wherein the final cooling temperature is 550-650 ℃.
The steel for the automobile steering system has strict requirements on toughness and fatigue performance, and sulfide inclusions have great harm on the toughness and the fatigue performance. Therefore, in order to reduce the content of sulfide inclusions in steel, the molten steel needs to be desulfurized to produce reducing slag during the refining in the LF furnace. And argon blowing treatment is carried out during RH vacuum treatment, and the argon blowing time is more than 8 min.
The medium carbon steel C, Mn of the invention has higher content, the casting blank has higher possibility of segregation, the temperature gradient is large when the molten steel with high superheat degree is solidified, which is beneficial to the development of coarse columnar crystals, so that inclusions are enriched at the front of the crystallization and among dendrites, the element segregation is formed at the central position of the casting blank, and meanwhile, the center porosity and the hole defect of the casting blank are easily caused due to unstable casting blank pulling speed. Therefore, the invention adopts low superheat degree casting and constant speed casting, and strictly controls the segregation of the casting blank. The temperature of the tundish molten steel is 1500-1550 ℃ during the molten steel continuous casting, and the drawing speed is 0.50-1.50 m/min.
In the invention, in order to ensure that the plate blank is fully heated and alloy elements are fully dissolved in a solid solution and prevent the abnormal growth of austenite grains, the heating temperature is 1150-1250 ℃, and the heating time is 3-5 h.
Further, in the production method of the medium carbon steel for the automobile steering system, the thickness of a plate blank cast by the molten steel is 200-250 mm, the deformation of each pass of rough rolling is required to be more than or equal to 15%, and the thickness of the plate blank after rough rolling is 40-60 mm.
Furthermore, in order to add deformation of a finish rolling non-recrystallization region, refine austenite grains, promote austenite flattening, and form a large number of ferrite nucleation cores through deformation induced phase transformation, the start rolling temperature of the finish rolling is 1000-1100 ℃, and the finish rolling temperature is 800-900 ℃.
Further, in the production method of the medium carbon steel for the automobile steering system, the thickness of the plate blank after the steel plate is finish rolled is 5-10 mm.
Further, in the production method of the medium carbon steel for the automobile steering system, the laminar cooling speed is 10-30 ℃/s. Laminar cooling is carried out at the speed to 550-650 ℃, the phase change superheat degree can be increased, ferrite-pearlite phase change is carried out on a phase change core formed in the finish rolling process, a fully refined finished product structure is formed, and the mechanical properties matched with strength and toughness are obtained.
When the medium carbon steel for the automobile steering system is prepared, the content of P, S is reduced by reducing the content of Si; the content of gas elements such as O, N and the like is reduced through vacuum treatment, so that the level of inclusions is reduced; then, low superheat degree casting and continuous casting dynamic soft reduction are adopted, and the segregation grade of the casting blank is reduced; the rolling and cooling control capability is fully exerted, and the requirements of reducing the grain size and improving the forming performance are met. The invention also reduces the reheating temperature of the plate blank to be lower, improves the rough rolling reduction, reduces the finish rolling inlet temperature, increases the finish rolling accumulated deformation through the corresponding controlled rolling and controlled cooling process, and obtains a ferrite-pearlite structure with a thinner size; by controlling the metallographic structure to be ferrite-pearlite, the uniformity of the structure is improved, the grain size of the final structure is reduced, and the toughness of the steel is improved. The yield strength of the finally produced medium carbon steel for the automobile steering system is more than or equal to 400MPa, the tensile strength is more than or equal to 520MPa, the elongation is more than or equal to 20%, the steel is qualified in a 180-degree cold bending test d-2 a, the impact energy at minus 10 ℃ is more than or equal to 70J (the sample size is 10 multiplied by 55mm), and the grain size is more than or equal to 10 grade. Has the characteristics of stable mechanical property, good obdurability matching and excellent forming performance.
The following examples are intended to illustrate specific embodiments of the present invention and are not intended to limit the scope of the invention.
Example 1 preparation of Medium carbon Steel for automobile steering System by the method of the present invention
Producing medium carbon steel for automobile steering system with 6.4mm thickness. The method comprises the following specific steps:
the steel billet is obtained by molten iron pretreatment, converter smelting, LF heating furnace refining, RH vacuum refining and continuous casting, the tundish temperature is 1520 ℃, the casting blank pulling speed is 0.90m/s, and the finished product comprises the following components: 0.24% of C, 0.10% of Si, 1.25% of Mn, 0.009% of P, 0.001% of S, and the balance of Fe and inevitable impurities. Reheating the steel billet at 1186 ℃ for 206 min; the rough rolling adopts 0+5 passes of rolling, the thickness of an intermediate blank is 49mm, and the deformation of each pass of the rough rolling is 20%, 21%, 26%, 32% and 32%; the finish rolling is 7-frame hot continuous rolling, the initial rolling temperature is 1000 ℃, the final rolling temperature is 830 ℃, and after the finish rolling is finished, the steel is cooled to 560 ℃ by adopting a front-section cooling mode at a cooling speed of 19 ℃/s.
Through detection, the mechanical properties of the medium carbon steel for the automobile steering system produced in the embodiment 1 are as follows: the yield strength was 472MPa, the tensile strength was 655MPa, the elongation was 38.5%, and the 180 ℃ cold bending test d-2 a passed and the impact energy at-10 ℃ was 68.1J (sample size 7.5X 10X 55 mm). The metallographic structure is ferrite-pearlite (see figure 1), and the grain size is 11 grades.
Example 2 preparation of Medium carbon Steel for automobile steering System by the method of the present invention
And producing the medium carbon steel with the thickness of 8.4mm for the automobile steering system. The method comprises the following specific steps:
the steel billet is obtained by molten iron pretreatment, converter smelting, LF heating furnace refining, RH vacuum refining and continuous casting, the temperature of a tundish is 1540 ℃, the casting blank drawing speed is 1.10m/s, and the finished product comprises the following components: 0.27% of C, 0.30% of Si, 1.40% of Mn, 0.015% of P, 0.006% of S, and the balance of Fe and inevitable impurities. Reheating the billet at 1216 ℃ for 223 min; 3+3 passes of rough rolling are adopted, the thickness of an intermediate blank is 54mm, and the deformation of each pass of rough rolling is 16%, 17%, 18%, 24%, 30% and 30%; the finish rolling is 7-frame hot continuous rolling, the initial rolling temperature is 1055 ℃, the final rolling temperature is 870 ℃, and after the finish rolling is finished, the steel is cooled to 625 ℃ by adopting a front-section cooling mode at a cooling speed of 15 ℃/s.
Through detection, the mechanical properties of the medium carbon steel for the automobile steering system produced in the embodiment 2 are as follows: the yield strength was 441MPa, the tensile strength was 635MPa, the elongation was 36.5%, and the 180 ℃ cold bending test d was 2 a-pass and the impact energy at-10 ℃ was 53.2J (sample size 7.5X 10X 55 mm). The metallographic structure is ferrite-pearlite (see fig. 2), and the grain size is 10.5 grade.
Comparative example 3 preparation of Medium carbon Steel for automobile steering System without Using the method of the present invention
Producing medium carbon steel for automobile steering system with thickness of 6.0 mm. The method comprises the following specific steps:
the steel billet is obtained by molten iron pretreatment, converter smelting, LF heating furnace refining, RH vacuum refining and continuous casting, the temperature of the tundish is 1560 ℃, the casting blank drawing speed is 0.80m/s, and the finished product comprises the following components: 0.31% of C, 0.35% of Si, 1.40% of Mn, 0.015% of P, 0.006% of S, and the balance of Fe and inevitable impurities. Reheating the steel billet at 1170 ℃ for 190 min; the rough rolling adopts 1+5 passes of rolling, the thickness of an intermediate blank is 45mm, and the deformation of each pass of the rough rolling is 13%, 19%, 23%, 24%, 25% and 29%; the finish rolling is 7-frame hot continuous rolling, the initial rolling temperature is 1105 ℃, the final rolling temperature is 890 ℃, and after the finish rolling is finished, the steel is cooled to 655 ℃ by adopting a front-section cooling mode at a cooling speed of 16 ℃/s.
In the comparative example 3, the carbon content and the silicon content in the steel components are improved, and through detection, the mechanical properties of the medium carbon steel for the automobile steering system produced in the comparative example 3 are as follows: the yield strength was 455MPa, the tensile strength was 665MPa, the elongation was 18%, and the cold bending test d at 180 ℃ failed at 2a and the impact energy at 10 ℃ was 32.4J (sample size: 7.5X 10X 55 mm). The metallographic structure is ferrite-pearlite (see fig. 3), block-shaped pearlite aggregates exist, the level of the banded structure is 3.0, and the grain size is 9.5.
Comparative example 4 production of Medium carbon Steel for automobile steering System without Using the method of the present invention
And producing the medium carbon steel with the thickness of 8.9mm for the automobile steering system. The method comprises the following specific steps:
the steel billet is obtained by molten iron pretreatment, converter smelting, LF heating furnace refining, RH vacuum refining and continuous casting, the temperature of the tundish is 1560 ℃, the casting blank drawing speed is 0.80m/s, and the finished product comprises the following components: 0.25% of C, 0.35% of Si, 1.20% of Mn, 0.025% of P, 0.012% of S, and the balance of Fe and inevitable impurities. Reheating the steel billet at 1230 ℃, and reheating for 261 min; 3+3 passes of rough rolling are adopted, the thickness of an intermediate blank is 45mm, and the deformation of each pass of rough rolling is 13%, 15%, 16%, 25%, 30% and 29%; the finish rolling is 7-frame hot continuous rolling, the initial rolling temperature is 1065 ℃, the final rolling temperature is 875 ℃, and after the finish rolling is finished, the steel is cooled to 575 ℃ at the cooling speed of 21 ℃/s by adopting a front-section cooling mode.
In comparative example 4, the content of silicon in the steel components is increased, and through detection, the mechanical properties of the medium carbon steel for the automobile steering system produced in comparative example 4 are as follows: the steel sheet had a yield strength of 395MPa, a tensile strength of 585MPa, and an elongation of 22%, and passed a 180 ℃ cold bending test d-2 a, and an impact energy of 38.4J (sample size 7.5X 10X 55mm) at-10 ℃. The metallographic structure was ferrite-pearlite (see fig. 4), the band structure was of grade 3.0, and the grain size was of grade 10.5.
According to the embodiment and the comparative example, the composition of the medium carbon steel for the automobile steering system is controlled, low superheat degree casting and continuous casting dynamic soft reduction are adopted in the production process, the segregation level of a casting blank is reduced, the rolling and cooling control capacity is fully exerted, the grain size is reduced, and the forming performance is improved. The medium carbon steel for the automobile steering system prepared by the method has the grain size of more than or equal to 10 grades and has more excellent mechanical property.
Claims (10)
1. The medium carbon steel for the automobile steering system is characterized by comprising the following chemical components: according to weight percentage, C is 0.20-0.30%, Mn: 1.0% -2.0%, Si: 0.05-0.10 percent of the total weight of the alloy, less than or equal to 0.020 percent of P, less than or equal to 0.010 percent of S, and the balance of Fe and inevitable impurities; the production method comprises the following steps: smelting, continuous casting, heating, rough rolling, finish rolling, laminar cooling and coiling;
smelting in a converter, refining in an LF furnace, performing vacuum treatment in an RH furnace, and feeding a calcium wire;
the LF furnace is used for refining, and reducing slag is produced and desulfurized on the molten steel; argon blowing is carried out during RH vacuum treatment, and the argon blowing time is more than 8 min; the temperature of the tundish molten steel is 1500-1550 ℃ during the molten steel continuous casting, and the drawing speed is 0.9-1.1 m/min;
the continuous casting adopts low superheat degree and constant-speed casting;
the heating temperature is 1150-1250 ℃, and the heating time is 3-5 h; the rough rolling is 5-7 passes of rolling, and the finish rolling is 6-7 passes of rolling; and carrying out laminar cooling after finish rolling, wherein the final cooling temperature is 550-650 ℃.
2. The medium carbon steel for an automobile steering system according to claim 1, wherein the medium carbon steel has a crystalline phase structure of ferrite-pearlite structure and a grain size of not less than 10 grade.
3. A method for producing a medium carbon steel for an automobile steering system according to claim 1 or 2, characterized in that: sequentially comprising the steps of smelting, continuous casting, heating, rough rolling, finish rolling, laminar cooling and coiling;
smelting in a converter, refining in an LF furnace, performing vacuum treatment in an RH furnace, and feeding a calcium wire;
the continuous casting adopts low superheat degree and constant-speed casting;
the heating temperature is 1150-1250 ℃, and the heating time is 3-5 h; the rough rolling is 5-7 passes of rolling, and the finish rolling is 6-7 passes of rolling; and carrying out laminar cooling after finish rolling, wherein the final cooling temperature is 550-650 ℃.
4. The method for producing medium carbon steel for an automobile steering system according to claim 3, characterized in that: and carrying out reduction slag making and desulfurization on the molten steel during the LF furnace refining.
5. The method for producing medium carbon steel for an automobile steering system according to claim 3, characterized in that: and argon blowing treatment is carried out during RH vacuum treatment, and the argon blowing time is more than 8 min.
6. The method for producing medium carbon steel for an automobile steering system according to claim 3, characterized in that: the temperature of the tundish molten steel is 1500-1550 ℃ during the molten steel continuous casting, and the drawing speed is 0.50-1.50 m/min.
7. The method for producing medium carbon steel for an automobile steering system according to claim 3, characterized in that: the thickness of the plate blank cast by the molten steel is 200-250 mm, the deformation of each pass of rough rolling is not less than 15%, and the thickness of the plate blank after rough rolling is 40-60 mm.
8. The method for producing medium carbon steel for an automobile steering system according to claim 3, characterized in that: the start rolling temperature of finish rolling is 1000-1100 ℃, and the finish rolling temperature is 800-900 ℃.
9. The method for producing medium carbon steel for an automobile steering system according to claim 3, characterized in that: the thickness of the plate blank after the steel plate is finely rolled is 5-10 mm.
10. The method for producing medium carbon steel for an automobile steering system according to claim 3, characterized in that: the laminar cooling speed is 10-30 ℃/s.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811190024.2A CN109182909B (en) | 2018-10-12 | 2018-10-12 | Medium carbon steel for automobile steering system and production method thereof |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811190024.2A CN109182909B (en) | 2018-10-12 | 2018-10-12 | Medium carbon steel for automobile steering system and production method thereof |
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| Publication Number | Publication Date |
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| CN112442632B (en) * | 2020-10-26 | 2022-01-18 | 首钢集团有限公司 | High-bending-resistance hot-rolled hot-forming steel and preparation method thereof |
| CN112410653B (en) * | 2020-11-06 | 2022-05-24 | 安阳钢铁股份有限公司 | Method for effectively preventing 40Cr cold thin slab slitting cracks from being generated |
| CN113106223A (en) * | 2021-04-15 | 2021-07-13 | 天津市新天钢钢铁集团有限公司 | Method for rolling low-alloy high-strength Q355B thin steel strip by using common carbon steel billet |
| CN114058949B (en) * | 2021-10-18 | 2022-10-21 | 首钢集团有限公司 | Hot-forming steel pickling plate and method for reducing intercrystalline oxidation of surface of steel pickling plate |
| CN114000064B (en) * | 2021-10-29 | 2023-03-31 | 攀钢集团攀枝花钢铁研究院有限公司 | Ultrahigh-strength hot-rolled steel strip with thickness less than 4mm and production method thereof |
| CN114262847A (en) * | 2021-12-20 | 2022-04-01 | 马鞍山钢铁股份有限公司 | High-surface-quality hot-rolled automobile steel with tensile strength larger than 1300MPa and manufacturing method thereof |
| CN114686753B (en) * | 2022-04-20 | 2023-03-28 | 张家港宏昌钢板有限公司 | Method for producing 40Mn hot-rolled steel, and use thereof |
| CN115874107B (en) * | 2022-12-29 | 2024-02-23 | 包头钢铁（集团）有限责任公司 | Method for improving impact toughness of steel for medium carbon ERW petroleum casing pipe |
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