Method for improving non-uniformity of high-hardenability silicon-manganese bearing steel GCr15SiMn carbide

Abstract

The invention discloses a method for improving the non-uniformity of high-hardenability silicon-manganese bearing steel GCr15SiMn carbides, and relates to the technical field of metallurgy, and the method comprises the following steps: controlling the superheat degree of a continuous casting process to be 20-35 DEG C, controlling the pulling speed to be 0.54-0.57 m / min, and controlling the soft reduction at the solidification tail end of a casting blank to be 13-15 mm. The casting temperature, the pulling speed and the solidification tail end rolling reduction in the continuous casting procedure are controlled, and the reasonable high-temperature heating time is set in the steel rolling procedure, so that the carbide nonuniformity of the rolled metal core part is greatly improved, and the carbide banding is effectively controlled to be smaller than or equal to 2.0 grades, the carbide network is effectively controlled to be smaller than or equal to 2.0 grades, and the carbide liquation is effectively controlled to be smaller than or equal to 0 grades.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgy, and in particular to a method for improving the inhomogeneity of carbides of high-hardenability silicon-manganese bearing steel GCr15SiMn. Background Art

[0002] High-carbon chromium bearing steel is a fully hardenable material suitable for bearings (high hardness, high strength, and high wear resistance). Depending on the service conditions of the bearing, bearing sizes can be selected based on their hardenability. They are categorized into the traditional high-carbon chromium bearing steel GCr15 series and the silicon-manganese bearing steel GCr15SiMn series. The GCr15 series is suitable for bearings of standard sizes, while the silicon-manganese bearing steel GCr15SiMn series is suitable for thick-walled bearing rings, large-size bearing rollers, or steel balls. GCr15SiMn is required for bearings with wall thicknesses exceeding 30mm or roller / ball diameters exceeding 38mm to ensure full hardening during quenching.

[0003] Compared to the currently produced GCr15, GCr15SiMn boasts higher Si and Mn contents and is traditionally produced using die casting, offering advantages such as high structural uniformity and density. In recent years, continuous casting has been adopted to compete on cost. Currently, carbide inhomogeneity in continuous casting is a production challenge. Therefore, a method to improve carbide inhomogeneity in high-hardenability silicon-manganese bearing steel is urgently needed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for improving the heterogeneity of carbides in high hardenability silicon-manganese bearing steel GCr15SiMn.

[0005] In order to solve the above technical problems, the technical solutions of the present invention are as follows: A method for improving the inhomogeneity of carbides in high hardenability silicon-manganese bearing steel GCr15SiMn, comprising: The superheat degree of the continuous casting process is controlled at 20~35℃, the casting speed is controlled at 0.54~0.57m / min, and the soft reduction at the end of the solidification of the casting is controlled at 13~15mm.

[0006] As a preferred solution of the method for improving the heterogeneity of carbides of high hardenability silicon-manganese bearing steel GCr15SiMn according to the present invention, it further comprises: The heating temperature of the steel rolling heating furnace in the steel rolling process is controlled to be 1200~1230℃, and the heating time is controlled to be 550~600min.

[0007] As a preferred solution of the method for improving the heterogeneity of carbides of high hardenability silicon-manganese bearing steel GCr15SiMn according to the present invention, it further comprises: The final rolling temperature in the steel rolling process is controlled to be 780~830℃.

[0008] As a preferred solution of the method for improving the heterogeneity of carbides of high hardenability silicon-manganese bearing steel GCr15SiMn according to the present invention, it further comprises: The diameter of the round steel after rolling in the steel rolling process is controlled to be greater than or equal to 50mm.

[0009] As a preferred solution of the method for improving the heterogeneity of carbides of high hardenability silicon-manganese bearing steel GCr15SiMn according to the present invention, it further comprises: The rolled round steel is cooled by water.

[0010] As a preferred solution of the method for improving the carbide heterogeneity of high hardenability silicon-manganese bearing steel GCr15SiMn according to the present invention, the red-return temperature of the cooling bed on the round steel is controlled to be 630°C.

[0011] The beneficial effects of the present invention are: (1) The present invention significantly improves the carbide heterogeneity in the core of the rolled material by controlling the pouring temperature, drawing speed and reduction at the end of solidification in the continuous casting process and setting a reasonable high-temperature heating time in the steel rolling process, and effectively controls the carbide banding ≤ 2.0 level, carbide network ≤ 2.0 level, and carbide liquid separation ≤ 0 level.

[0012] (2) The purpose of controlling the superheat in the continuous casting process to 20-35°C in the present invention is to ensure the consistency of the liquid phase hole length of the billet at the end of solidification; the continuous casting speed is controlled to 0.54-0.57m / min to achieve effective reduction of the straightening roller group in the range of 0.3-0.7; the light reduction at the end of solidification of the billet is 13-15mm, and the billet is lightly reduced at the end of solidification to break the dendrite bridge to offset the volume shrinkage of the liquid phase solidification in the center of the billet, so that the remaining liquid phase enriched with solute between the dendrites remains in its original position, thereby reducing or even eliminating the center segregation.

[0013] (3) The present invention controls the steel rolling heating furnace to maintain a temperature of 1200°C or higher for 550-600 minutes. This long-term high-temperature heating allows the carbide bands and liquid precipitation to diffuse and dissolve. Simultaneously, the heating temperature of the steel rolling heating furnace is controlled to be less than or equal to 1230°C to prevent overheating of the low-melting-point material in the core, which could lead to micropores. Afterwards, controlled cooling is performed by water piercing after rolling. Rapid cooling allows the steel to quickly escape from the precipitation area of a large amount of secondary cementite, thereby improving the carbide network. DETAILED DESCRIPTION

[0014] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific implementation methods.

[0015] The present application provides a method for improving the carbide inhomogeneity of high hardenability silicon manganese bearing steel GCr15SiMn, which specifically includes continuous casting process control and steel rolling process control. Among them, the pouring temperature, pulling speed and the amount of reduction at the end of solidification need to be controlled in the continuous casting process. The steel rolling process formulates a reasonable high-temperature heating time to greatly improve the carbide inhomogeneity in the core of the rolled material, and effectively control the carbide banding ≤ 2.0 level, carbide network ≤ 2.0 level, and carbide liquid precipitation ≤ 0 level.

[0016] Specifically, the method for improving the inhomogeneity of carbides in high hardenability silicon-manganese bearing steel GCr15SiMn comprises the following steps: Step S101: During the continuous casting process, the superheat is controlled to be 20-35°C, the continuous casting speed is controlled to be 0.54-0.57 m / min, and the soft reduction at the end of solidification of the ingot is controlled to be 13-15 mm.

[0017] Specifically, the purpose of controlling the superheat during the continuous casting process to 20-35°C is to ensure the consistency of the liquid phase hole length at the end of solidification. Secondly, to achieve effective reduction by the straightening roll group within the reduction range of fs: 0.3-0.7, the continuous casting speed must be controlled to 0.54-0.57m / min. Finally, based on simulation calculations, the light reduction at the end of solidification is set to 13-15mm. This light reduction at the end of solidification breaks the dendritic bridges, offsets the volume shrinkage of the liquid phase solidification at the center of the billet, and allows the residual solute-rich liquid phase between the dendrites to remain in its original position, thereby reducing or even eliminating center segregation.

[0018] Step S102: During the rolling process, the heating furnace temperature is controlled to 1200-1230°C, and the heating time is controlled to 550-600 minutes. For rolling round steel ≥50 mm, the finishing temperature is controlled to 780-830°C. After rolling, water cooling is performed to keep the steel's return temperature on the cooling bed at 600-650°C.

[0019] Specifically, the steel rolling furnace is first maintained at a temperature of 1200°C or higher for 550-600 minutes. This prolonged high-temperature heating allows the carbide bands and liquid precipitation to diffuse and dissolve. Simultaneously, the heating temperature of the steel rolling furnace is controlled to be less than or equal to 1230°C to prevent overheating of low-melting-point materials in the core, which could lead to micropores. Afterwards, controlled cooling is performed by water piercing after rolling. Rapid cooling allows the steel to quickly escape from areas with large amounts of secondary cementite precipitation, improving the carbide network.

[0020] The above solution will be further described below through specific embodiments.

[0021] Example 1: This example provides a method for improving the inhomogeneity of carbides in high hardenability silicon-manganese bearing steel GCr15SiMn. The specific steps are as follows: Step S101: During the continuous casting process, superheat was controlled at 20°C to ensure consistent liquidus hole length at the end of solidification. The continuous casting speed was maintained at a constant 0.54 m / min, with a total soft reduction of 13 mm. Macroscopic sampling was performed in accordance with GB / T 18254-2016, and central segregation was assessed according to GB / T 18254-2016.

[0022] Step S102: The rolling furnace temperature is controlled between 1200°C and 1210°C for 550 minutes. After rolling into 50mm round bars, the final rolling temperature is controlled at 805°C to 810°C. After rolling, water cooling is performed, and the return temperature on the upper cooling bed is controlled to approximately 630°C. Carbide inhomogeneity sampling and testing is performed in accordance with GB / T18254-2016, with the testing location at the core of the round bar. Carbide banding is controlled to level 2.0, and carbide network to level 1.5, as assessed according to GB / T18254-2016.

[0023] Example 2: This example provides a method for improving the inhomogeneity of carbides in high hardenability silicon-manganese bearing steel GCr15SiMn. The specific steps are as follows: Step S101: During the continuous casting process, superheat was controlled at 25°C to ensure consistent liquidus hole length at the end of solidification. The continuous casting speed was maintained at a constant 0.54 m / min, with a total soft reduction of 14 mm. Macroscopic sampling was performed in accordance with GB / T 18254-2016, and central segregation was assessed according to GB / T 18254-2016.

[0024] Step S102: The rolling furnace temperature is controlled between 1220°C and 1230°C for 570 minutes. After rolling into 60mm round steel, the final rolling temperature is controlled at 810°C to 820°C. After rolling, water cooling is performed, and the return temperature on the upper cooling bed is controlled to approximately 615°C. Carbide inhomogeneity sampling and testing is performed in accordance with GB / T18254-2016, with the testing location at the core of the round steel. Carbide banding is controlled at level 2.0, and carbide network at level 2.0, as assessed according to GB / T18254-2016.

[0025] Example 3: This example provides a method for improving the inhomogeneity of carbides in high hardenability silicon-manganese bearing steel GCr15SiMn. The specific steps are as follows: Step S101: During the continuous casting process, superheat was controlled at 32°C to ensure consistent liquidus hole length at the end of solidification. The continuous casting speed was maintained at a constant 0.57 m / min, with a total soft reduction of 15 mm. Macroscopic sampling was performed in accordance with GB / T 18254-2016, and central segregation was assessed according to GB / T 18254-2016.

[0026] Step S102: The temperature of the rolling furnace is controlled at 1220-1230°C for 600 minutes. After rolling into 60mm round steel, the final rolling temperature is controlled at 790-800°C. After rolling, water cooling is performed, and the return temperature on the upper cooling bed is controlled to approximately 605°C. Carbide inhomogeneity sampling and testing is performed in accordance with GB / T18254-2016. The testing location is the core of the round steel. According to GB / T18254-2016, carbide banding is controlled to level 1.5, and carbide network is controlled to level 1.5.

[0027] In addition to the above embodiments, the present invention may also have other implementation methods; any technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention.

Claims

1. A method for improving the carbide heterogeneity of high hardenability silicon manganese bearing steel GCr15SiMn, characterized by: include: The superheat degree of the continuous casting process is controlled at 20~35℃, the casting speed is controlled at 0.54~0.57m / min, and the soft reduction at the end of the solidification of the casting is controlled at 13~15mm.

2. The method for improving the carbide heterogeneity of high hardenability silicon-manganese bearing steel GCr15SiMn according to claim 1, characterized in that: Also includes: The heating temperature of the steel rolling heating furnace in the steel rolling process is controlled to be 1200~1230℃, and the heating time is controlled to be 550~600min.

3. The method for improving the carbide heterogeneity of high hardenability silicon-manganese bearing steel GCr15SiMn according to claim 2, characterized in that: Also includes: The final rolling temperature in the steel rolling process is controlled to be 780~830℃.

4. The method for improving the carbide heterogeneity of high hardenability silicon-manganese bearing steel GCr15SiMn according to claim 3, characterized in that: Also includes: The diameter of the round steel after rolling in the steel rolling process is controlled to be greater than or equal to 50mm.

5. The method for improving the carbide heterogeneity of high hardenability silicon-manganese bearing steel GCr15SiMn according to claim 4, characterized in that: Also includes: The rolled round steel is cooled by water.

6. The method for improving the carbide heterogeneity of high hardenability silicon-manganese bearing steel GCr15SiMn according to claim 5, characterized in that: The red-return temperature of the round steel cooling bed is controlled to be 630℃.