Steel for a spherical shell of a constant velocity joint and a method for producing the same

Abstract

The present application relates to a kind of steel for universal joint spherical shell and its production method, belong to automobile steel smelting technical field.Steel delivery state: microstructure in cementite exists in spheroidizing structure state, the rest is lamellar pearlite, wherein spheroidizing rate is ≥60%.Hardness is not more than 180HBW, the end quenching J3 of steel is 45-48HRC, J5 is 38-42HRC.Circular steel sample is after normalizing at 820 DEG C, tensile strength is ≥650MPa, yield strength is ≥400MPa, elongation after fracture is ≥14%, reduction of area is ≥45%.Element composition weight percentage is C:0.55~0.65%, Si:≤0.08%, Mn:0.60~0.90%, P:≤0.020%, S:≤0.010%, Cr:≤0.20%, Ni:≤0.10%, Mo:≤0.10%, Al:≤0.050%, B:0.0010~0.0020%, Ti:0.020~0.030%, Ca≤0.0010%, O:≤0.0010%, remainder is Fe and unavoidable impurities.Production process: preliminary smelting-external refining-vacuum degassing-continuous casting-continuous rolling-spheroidizing annealing, with good cold working performance, meet the material requirements of universal joint spherical shell.

Description

Technical Field

[0001] This invention relates to the field of automotive steel and its smelting technology, specifically to a steel for a constant velocity universal joint spherical shell and its production method. Background Technology

[0002] Universal joints are crucial components of automotive transmission systems. In automotive transmissions and other systems, universal joints are essential for transmitting power between shafts that intersect or whose relative positions frequently change. Currently, the most commonly used constant velocity universal joint in passenger cars is the ball-cage type. The function of the ball-cage type universal joint is to transmit engine power from the transmission to the two front wheels, driving the car at high speeds. It mainly consists of a spherical housing, a star-shaped sleeve, a ball cage, and steel balls. Because constant velocity universal joints transmit heavy driving torque, require high loads and high transmission precision, are in high demand, and are also safety components, their main parts are all precision-forged.

[0003] The modern automotive industry is facing increasingly fierce competition, placing higher demands on the power, handling, comfort, and safety of automobiles. Coupled with energy and environmental considerations, the design of key functional automotive components must comprehensively consider important indicators such as safety, functionality, economy, and emissions. This places higher demands on materials, requiring them to be lighter while ensuring performance. For materials used in automotive universal joint spherical shells, the components play a role in transmission and support, and also bear the long-term effects of alternating load stress. Therefore, the materials must possess sufficient wear resistance, fatigue resistance, and good toughness.

[0004] Currently, the spherical shell of a constant velocity universal joint is typically made of 20CrNiMo material, and the common processing method is bar blanking - hot forging - machining - carburizing and quenching heat treatment - grinding. Hot forging offers good material plasticity, facilitating forming, but results in low machining accuracy, low material utilization, and high energy consumption. Cold forging, on the other hand, requires less machining, has higher material utilization, saves energy, and reduces production costs. However, due to the large deformation rate of the spherical shell of the constant velocity universal joint, cold forging places stringent requirements on the material's cold forging properties, demanding good plasticity and toughness. Furthermore, depending on the application requirements of the universal joint spherical shell, it also needs good wear resistance and a certain degree of hardenability. In addition, non-metallic inclusions in the steel disrupt the continuity and homogeneity of the metal. Under alternating stress conditions, depending on the application, inclusions easily cause stress concentration, becoming fatigue crack initiation points, leading to crack formation and reduced product lifespan. To improve the final product's lifespan, it is essential to improve the purity of the steel and minimize non-metallic inclusions.

[0005] Current 20CrNiMo steel has a high alloy content, resulting in high production costs. Furthermore, due to this high alloy content, the original microstructure of hot-rolled bars often includes bainite in addition to ferrite and pearlite, leading to high hardness and poor plasticity, making it unsuitable for cold forging. To overcome these shortcomings, this invention proposes a medium-carbon steel for constant velocity universal joint spherical shells, comprehensively balancing the material's hardenability and cold forging characteristics. The hot-rolled original microstructure of this material is a uniform and fine lamellar structure of ferrite and pearlite. After spheroidizing annealing, the delivered steel exhibits cementite in a spheroidized microstructure with a spheroidization rate ≥60%, meeting customer cold working requirements. Simultaneously, the composition design incorporates low-silicon steel, further enhancing the steel's cold forging performance. Summary of the Invention

[0006] To meet the demand for steel for universal joint spherical shells, this invention has developed a new type of steel for universal joint spherical shells by rationally designing the chemical composition of the steel.

[0007] The main technical indicators of the steel described in this invention are as follows: the steel is delivered in a state where cementite exists in a spheroidized structure, and the remainder is lamellar pearlite, with a spheroidization rate of ≥60%. This structural requirement is designed based on several considerations. On the one hand, spheroidized structure is the most stable structure in steel, which facilitates subsequent processing. However, since this product is low-carbon steel, the proportion of cementite is very small, and it cannot achieve 100% spheroidization like high-carbon bearing steel. Therefore, a spheroidization rate of ≥60% is required. On the other hand, steel that meets the above structural requirements has better hardness control. The hardness is not too high (suitable for subsequent cold working) nor too low (to prevent the steel from sticking to the tool during subsequent cold working).

[0008] After being normalized at 820℃, the finished round steel samples have a tensile strength ≥650MPa, a yield strength ≥400MPa, an elongation after fracture ≥14%, and a reduction of area ≥45%.

[0009] The hardness of the steel in the delivery condition shall not exceed 180 HBW. The end-quenched hardness of J3 steel is 45-48 HRC, and that of J5 steel is 38-42 HRC.

[0010] Non-metallic inclusions in steel shall be inspected according to GB / T 10561A method, wherein brittle and non-deformable inclusions shall be grade B fine ≤ 1.5, grade B coarse ≤ 1.0, grade D fine ≤ 1.0, grade D coarse ≤ 0.5, and grade Ds ≤ 1.0.

[0011] The elemental composition of the steel in this application, by weight percentage, is as follows: C: 0.55–0.65%, Si: ≤0.08%, Mn: 0.60–0.90%, P: ≤0.020%, S: ≤0.010%, Cr: ≤0.20%, Ni: ≤0.10%, Mo: ≤0.10%, Al: ≤0.050%, B: 0.0010–0.0020%, Ti: 0.020–0.030%, Ca: ≤0.0010%, O: ≤0.0010%, with the balance being Fe and unavoidable impurities.

[0012] The elemental composition of this application is based on:

[0013] 1) Determination of C content

[0014] Carbon (C) is an essential element for ensuring the wear resistance of steel. Increasing the carbon content in steel will increase its martensitic transformation ability, thereby improving its hardness and strength, and thus its wear resistance. However, excessively high C content is detrimental to the toughness of steel. Furthermore, excessively high C content can also lead to severe central C segregation, thus affecting the core toughness of the steel. This invention controls its content to be 0.55–0.65%. The steel of this invention belongs to the category of medium carbon steel.

[0015] 2) Determination of Si content

[0016] Si is the key element in this invention. Si, dissolved in the ferrite phase, has a strong solid solution strengthening effect, significantly improving the strength of ferrite, but simultaneously reducing its plasticity and toughness. Si is added to steel as a deoxidizing element during steelmaking. The steel of this invention is intended for cold working, requiring good cold working properties, which means excellent plasticity and toughness of the ferrite in the steel. Therefore, the Si content of the steel in this invention should be as low as possible to minimize the amount of Si dissolved in the ferrite and maximize the plasticity limit of ferrite; thus, the Si content is set within the range of ≤0.08%.

[0017] 3) Determination of Mn content

[0018] Mn, as a deoxidizing element in the steelmaking process, is an effective strengthening element for steel, playing a role in solid solution strengthening. Furthermore, Mn can improve the hardenability and hot working properties of steel. Mn can eliminate the influence of sulfur (S): in steelmaking, Mn can combine with S to form high-melting-point MnS, thereby weakening and eliminating the adverse effects of S. However, high Mn content will reduce the toughness of steel. In this invention, the Mn content is controlled at 0.60–0.90%.

[0019] 4) Determination of Al content

[0020] Al is added as a deoxidizing element in steel. Besides reducing dissolved oxygen in molten steel, Al combines with N to form fine, dispersed aluminum nitride inclusions, which refine the grain size. However, excessive Al content can lead to the formation of large, brittle inclusions such as Al₂O₃ particles during steelmaking, reducing the purity of the steel and affecting the service life of the finished product. In this invention, the Al content is defined as ≤0.05%.

[0021] 5) Determination of B content

[0022] Bo can improve the hardenability of steel, increase its high-temperature strength, and strengthen grain boundaries in steel. The content of Bo in this invention is determined to be in the range of 0.0010 to 0.0020%.

[0023] 6) Determination of Ti content

[0024] Ti in steel forms TiN inclusions, which are hard and angular, severely affecting the fatigue life of the material. However, Ti preferentially reacts with N in molten steel, reducing the failure caused by the reaction of N with B in the molten steel, which leads to the addition of B element. Therefore, this invention requires the addition of Ti element. After comprehensive calculation, the Ti content range of this invention is determined to be 0.02% to 0.03%.

[0025] 8) Determination of Ca content

[0026] The Ca content increases the number and size of dot oxides in steel. Furthermore, because dot oxides have high hardness and poor plasticity, they do not deform during steel deformation and easily form voids at interfaces, thus degrading the steel's properties. In this invention, the Ca content range is determined to be ≤0.001%.

[0027] 9) Determination of O content

[0028] Oxygen content represents the total amount of oxide inclusions. The brittle inclusions of oxides limit the service life of the finished product. Numerous experiments have shown that reducing oxygen content is significantly beneficial for improving steel purity, especially reducing the content of brittle oxide inclusions in the steel. In this invention, the oxygen content range is defined as ≤0.0010%.

[0029] 10) Determination of P and S content

[0030] Phosphorus (P) severely causes segregation during solidification in steel. P dissolves in ferrite, causing grain distortion and coarsening, and increasing cold brittleness. In this invention, the P content is defined as ≤0.020%. Sulfur (S) causes hot brittleness in steel, reducing its ductility and toughness. In this invention, the S content is defined as ≤0.010%.

[0031] The production process for the steel used in the universal joint spherical shell is as follows: primary refining in an electric furnace or converter — ladle refining — VD or RH vacuum degassing — continuous casting — continuous rolling — spheroidizing annealing — finishing — parts packaging and warehousing.

[0032] Its main production steps are as follows:

[0033] Step 1: Preliminary Refining: According to the elemental composition ratio, high-quality molten iron and high-quality alloy are loaded into an electric furnace or converter, and oxygen is blown to assist melting. The final carbon content is controlled at 0.15-0.25% to prevent over-oxidation of the molten steel. The final phosphorus content is controlled at ≤0.020%. The steel is tapped using the slag-blocking tapping method. After tapping, the slag is immediately removed.

[0034] Step 2: Steel Refining: The entire refining process employs bottom-blown argon stirring of the molten steel, with slag formation on the surface. Because it is low-silicon steel, silicon carbide and silicon-containing alloys are not permitted for deoxidation to prevent excessive silicon content. Strong deoxidation is achieved using aluminum wire and aluminum particles: the aluminum wire penetrates deep into the molten steel for precipitation deoxidation, while the aluminum particles diffuse on the surface for deoxidation. When the stoichiometric amount of aluminum in the molten steel exceeds that of oxygen, insoluble clusters of Al2O3 non-metallic inclusions with a density less than that of the molten steel will form in the molten steel. Larger clusters of Al2O3 will quickly float to the slag on the surface of the molten steel. Temperature sampling in the refining furnace is controlled 3–5 times, maintaining the furnace temperature at 1520–1650℃. The entire refining process takes ≥40 minutes.

[0035] Step 3 Vacuum Degassing: The refined molten steel is subjected to high vacuum degassing treatment, preferably with a vacuum degree ≤133Pa and a vacuum holding time ≥15min. After the vacuum treatment, titanium-iron wire is fed in to control the titanium content in the molten steel within the set range. At the same time, about 100m of silicon-calcium wire is fed in to modify the Al2O3 inclusions in the molten steel, transforming Al2O3 or MgO·Al2O3 into calcium aluminates and composite inclusions with lower melting points, ensuring smooth subsequent casting.

[0036] Step 4 Continuous Casting: The steel billet is cast using the continuous casting process. Preferably, the entire continuous casting process adopts a protective casting mode, that is, the molten steel and air are completely isolated, and the superheat of the molten steel in the tundish is controlled at 10-15℃. During the continuous casting process, a composite electromagnetic stirring of MEMS for crystallizer and FEMS for solidification end is used, and the end electromagnetic stirring is combined with the continuous casting light reduction to improve the segregation in the center of the continuously cast billet.

[0037] Step 5: Heating the steel: High-temperature diffusion: The continuously cast billet is heated in the furnace to a temperature of 1100-1200℃ and held at this temperature for more than 3 hours. The air-coal ratio of the gas is controlled at 1.01-1.08 to reduce the residual oxygen content, prevent the steel from being decarburized beyond the standard, and avoid the subsequent steel surface from being unable to be spheroidized into the required microstructure due to severe decarburization.

[0038] Step 6: Rolling: Set the initial rolling temperature to 950-1150℃ and the final rolling temperature to 850-950℃, ensuring that the entire rolling deformation process takes place within the austenite recrystallization temperature range. The deformation amount per pass is controlled at 10%-20%. After final rolling, the steel is transferred to a cooling bed and slowly cooled using an insulation cover. The cooling rate during this process is controlled at 20℃ / min-30℃ / min, and the cooling time on the cooling bed is controlled at approximately 20 minutes. This results in a uniform and fine ferrite and pearlite lamellar structure, with the pearlite lamellar structure accounting for 30%-50%. This microstructure creates conditions for ensuring the required spheroidization rate in subsequent processes.

[0039] Step 7: Spheroidizing Annealing. First, the rolled steel is held at 730℃±(0-10℃) for 7 hours, allowing some cementite to dissolve into the austenite, while the matrix retains cementite particles for subsequent nucleation, achieving dynamic equilibrium. Then, water mist cooling is performed, cooling to 670℃±(0-10℃) within 3 minutes and holding for 5 hours. Finally, it is cooled in the furnace for about 6 hours to 250℃±(0-10℃) before being removed from the furnace. This process promotes the transformation of pearlite lamellae into spheroidal carbides, resulting in a final spheroidization rate of ≥60% for the finished steel (if the spheroidization rate is too low, the steel structure will be unstable, and the hardness will be too high, which is not conducive to subsequent cold working).

[0040] Compared with the prior art, the advantages of the present invention are as follows:

[0041] 1) In the elemental composition design, the present invention adopts a low silicon steel design and adds trace alloying elements such as B and Ti. While reducing costs, the mechanical properties of the steel are significantly improved, which can meet the application requirements.

[0042] 2) This invention uses special steelmaking, rolling and spheroidizing annealing processes to ensure that the steel achieves a special metallographic structure and meets the low hardness requirements, thus better satisfying the cold working performance of the material. Attached Figure Description

[0043] Figure 1 The image shows a typical metallographic structure of the steel used for the constant velocity universal joint spherical shell according to an embodiment of the present invention. The structure in the image is lamellar pearlite + spheroidal cementite (spheroidization rate > 60%).

[0044] Figure 2 The image shows the metallographic structure of the steel described in the comparative example of this invention. The microstructure in the image is ferrite + pearlite + bainite. Detailed Implementation

[0045] The present invention will be further described in detail below with reference to embodiments and comparative examples. The embodiments are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention.

[0046] The chemical composition (wt%) of the steel used for the constant velocity universal joint spherical shells corresponding to Examples 1-3 of this invention is shown in Tables 1 and 2. It is also compared with the control steel 20CrNiMo.

[0047] Table 1

[0048] Example C Si Mn P S Cr Cu Ni Al B This invention 1 0.56 0.03 0.63 0.018 0.002 0.08 0.01 0.02 0.015 0.0015 This invention 2 0.61 0.05 0.72 0.016 0.002 0.06 0.01 0.02 0.023 0.0012 This invention 3 0.65 0.08 0.85 0.015 0.001 0.05 0.02 0.03 0.020 0.0017 Compared to steel 0.20 0.23 0.83 0.018 0.005 0.58 0.03 0.54 0.027 0.0002

[0049] Table 2

[0050] Example Mo Ca Ti O This invention 1 0.01 0.0002 0.027 0.00076 This invention 2 0.02 0.0002 0.025 0.00071 This invention 3 0.01 0.0001 0.028 0.00068 Compared to steel 0.28 0.0005 0.0025 0.0010

[0051] The mechanical properties of the round steel bar samples in Examples 1-3 of this application after normalizing are shown in Table 3.

[0052] Table 3 Comparison of mechanical properties of each embodiment

[0053]

[0054] The hardness and metallographic data of the steel in each embodiment are shown in Table 4 below. Typical metallographic structures of the embodiments of the present invention are shown in... Figure 1 The metallographic structure of the comparison is shown below. Figure 2 .

[0055] Table 4

[0056] Example Hardness HBW Metallographic structure Example 1 1 162 Lamellar pearlite + spherical cementite Example 2 2 165 Lamellar pearlite + spherical cementite Example 3 3 167 Lamellar pearlite + spherical cementite Comparative Example 205 Ferrite + Pearlite + Bainite

[0057] The manufacturing process of the steel for the constant velocity universal joint spherical shell in Examples 1-3 is as follows: electric furnace or converter — ladle refining — VD or RH vacuum degassing — continuous casting — continuous rolling — spheroidizing annealing — finishing — parts packaging and warehousing.

[0058] In the three embodiments, the tapping endpoint C is controlled at 0.15-0.25%, the endpoint P is required to be ≤0.020%, and other basic smelting process points are executed according to the requirements of steps 1-4 above. The continuous casting superheat is controlled within 10-15℃. The specific rolling process of the continuously cast billet in each embodiment is as follows: the continuously cast billet is heated in a walking beam furnace at a temperature of 1100-1200℃ and held at this temperature for more than 3 hours. The air-coal ratio of the gas is controlled at 1.01-1.08 to reduce residual oxygen and prevent excessive decarburization of the steel. The initial rolling temperature is set at 950-1150℃ and the final rolling temperature is set at 850-950℃. The entire rolling deformation process is carried out in the austenite recrystallization temperature range, and the deformation amount of each pass is controlled at 10%-20%. After the final rolling, the steel is slowly cooled using an insulation cover. The cooling rate of the steel during the slow cooling process is controlled at 20℃ / min-30℃ / min. Finally, a uniform and fine ferrite and pearlite lamellar structure is obtained, with the pearlite lamellar structure accounting for 30%-50%. The spheroidizing annealing process in each embodiment is performed according to the process requirements described in step 7. The final finished steel has a spheroidization rate of ≥60%, with the remainder being lamellar pearlite. See the metallographic photographs for details. Figure 1 .

[0059] As can be seen from the data in Tables 1-3, compared with the traditional 20CrNiMo, the constant velocity universal joint spherical shell steel in the above embodiments exhibits improved performance in terms of composition design. This is achieved through a low-Si design that enhances the cold working properties of the steel, coupled with microalloying by adding B and Ti. The tensile strength, yield strength, hardenability, and other mechanical properties of this invention are roughly equivalent to or slightly lower than those of 20CrNiMo, while significantly reducing the content of precious metals such as Ni and Mo, thus lowering costs and enhancing market competitiveness. Furthermore, the hardness of this steel after spheroidizing annealing is significantly lower than that of the comparative steel, making it more suitable for cold forging. In terms of metallographic structure, the spheroidized structure is more stable, resulting in better processing stability than the comparative steel with its ferrite + pearlite + bainite metallographic structure. In conclusion, the steel of this invention is significantly superior to the comparative steel in terms of cost and processing performance, giving it better market competitiveness.

Claims

1. A method for producing steel for a constant velocity universal joint spherical shell, characterized in that: The elemental composition of steel by weight percentage is: C: 0.55–0.65%, Si: ≤0.08%, Mn: 0.60–0.90%, P: ≤0.020%, S: ≤0.010%, Cr: ≤0.20%, Ni: ≤0.10%, Mo: ≤0.10%, Al: ≤0.050%, B: 0.0010–0.0020%, Ti: 0.020–0.030%, Ca: ≤0.0010%, O: ≤0.0010%, with the balance being Fe and unavoidable impurities; the production methods include… Step 1, Preliminary Refining: According to the elemental composition ratio, high-quality molten iron and high-quality alloy are loaded into an electric furnace or converter, and oxygen is blown to assist melting. The final carbon content is controlled at 0.15-0.25% to prevent over-oxidation of the molten steel, and the final phosphorus content is controlled at ≤0.020%. The steel is tapped using the slag-blocking tapping method, and slag removal is carried out immediately after tapping. Step 2, Refining: The entire refining process employs bottom-blown argon stirring of molten steel, with slag formation on the surface of the molten steel. Silicon carbide and silicon-containing alloys are not permitted for deoxidation. Strong deoxidation is achieved using aluminum wire and aluminum particles: the aluminum wire penetrates deep into the molten steel for precipitation deoxidation, while the aluminum particles diffuse on the surface of the molten steel for deoxidation. When the stoichiometric amount of aluminum in the molten steel exceeds that of oxygen, clusters of Al2O3 non-metallic inclusions, insoluble in the molten steel and with a density less than that of the molten steel, will form in the molten steel. Larger clusters of Al2O3 will quickly float to the slag on the surface of the molten steel. The refining furnace temperature is measured and sampled 3-5 times, maintaining the refining furnace temperature at 1520-1650℃. The entire refining process takes ≥40 minutes. Step 3, Vacuum Degassing: The refined molten steel is degassed under high vacuum. After the vacuum treatment is completed, titanium-iron wire is fed in to control the titanium content in the molten steel within the set range. At the same time, silicon-calcium wire is fed in to modify the Al2O3 inclusions in the molten steel, transforming Al2O3 or MgO·Al2O3 into calcium aluminates and composite inclusions with lower melting points. Step 4, Continuous casting: Molten steel is poured into steel billets using the continuous casting process; Step 5, Steel Rolling Heating: High-Temperature Diffusion: The steel billet is heated in the furnace at a temperature of 1100-1200℃ and held at this temperature for more than 3 hours, while controlling the air-to-coal ratio of the gas in the furnace at 1.01-1.08; Step Six: Rolling: The entire rolling deformation process is carried out in the austenite recrystallization temperature range, and the deformation amount of each pass is controlled at 10%-20%. After the final rolling is completed, the steel is transferred to the cooling bed and slowly cooled using an insulation cover. The cooling rate of the steel during the slow cooling process is controlled at 20℃ / min-30℃ / min, and the slow cooling time on the cooling bed is controlled at more than 20 minutes. Finally, a uniform and fine ferrite and pearlite lamellar structure is obtained, with the pearlite lamellar structure accounting for 30%-50%. Step 7, Spheroidizing Annealing: First, the rolled steel is held at 730℃±10℃, allowing some cementite to dissolve in the austenite, while the matrix retains cementite particles for subsequent nucleation, achieving dynamic equilibrium. Then, water mist cooling is performed to 670℃±10℃, and the temperature is held. Finally, the steel is cooled in the furnace to 250℃±10℃ before being removed from the furnace, promoting the transformation of pearlite lamellars into spheroidal carbides. The delivered condition of the steel is: cementite exists in a spheroidized structure, with the remainder being lamellar pearlite, of which the spheroidization rate is ≥60%.

2. The method for producing steel for a constant velocity universal joint spherical shell according to claim 1, characterized in that: The hardness of the steel in the delivery condition shall not exceed 180 HBW, and the end-quenched hardness of J3 steel shall be 45-48 HRC, and that of J5 steel shall be 38-42 HRC.

3. The method for producing steel for constant velocity universal joint spherical shells according to claim 1, characterized in that: After being normalized at 820℃, the finished round steel samples have a tensile strength ≥650MPa, a yield strength ≥400MPa, an elongation after fracture ≥14%, and a reduction of area ≥45%.

4. The method for producing steel for a constant velocity universal joint spherical shell according to claim 1, characterized in that: Non-metallic inclusions in steel shall be tested according to GB / T 10561 Method A, wherein brittle and non-deformable inclusions shall be grade B fine ≤ 1.5, grade B coarse ≤ 1.0, grade D fine ≤ 1.0, grade D coarse ≤ 0.5, and grade Ds ≤ 1.

0.

5. The method for producing steel for a constant velocity universal joint spherical shell according to claim 1, characterized in that: In step three, the vacuum degree of the high vacuum degassing treatment is ≤133Pa, and the vacuum degree is maintained for ≥15min.

6. The method for producing steel for a constant velocity universal joint spherical shell according to claim 1, characterized in that: In step four, the entire continuous casting process adopts a protective casting mode, which completely isolates the molten steel from the air and controls the superheat of the molten steel in the tundish at 10-15℃. During the continuous casting process, a composite electromagnetic stirring of MEMS for the crystallizer and FEMS for the solidification end is used, and the end electromagnetic stirring is combined with the continuous casting light reduction to improve the segregation in the center of the continuously cast billet.

7. The method for producing steel for a constant velocity universal joint spherical shell according to claim 1, characterized in that: In step six, the initial rolling temperature is set to 950-1150℃, and the final rolling temperature is set to 850-950℃.

8. The method for producing steel for constant velocity universal joint spherical shells according to claim 1, characterized in that: In step seven, the rolled steel is held at 730℃±10℃ for 7 hours, then cooled with water mist to 670℃±10℃ within 3 minutes and held for 5 hours. Finally, it is cooled in the furnace for 6 hours to 250℃±10℃ before being taken out of the furnace.

Images