Rolling method for reducing carbide network rating of high-carbon chromium bearing steel

Abstract

A rolling method for reducing a carbide network rating of high-carbon chromium bearing steel, sequentially comprising: billet heating, descaling, rough rolling, intermediate rolling, controlled rolling, intermediate material segmentation, finish rolling, controlled cooling, and cooling on a cooling bed. By improving the rolling process and using a "segmentation before cooling" method to adjust the rolling procedure, the problems that the temperature is too low due to water quenching after rolling, the hardness of a rolled material is high, and normal operation of a shearing device cannot be guaranteed are solved, and the effect of reducing the carbide network rating is achieved, thereby avoiding the additional work procedures and costs caused by the non-compliant carbide network of the rolled material.

Description

Rolling method for reducing carbide network level of high-carbon chromium bearing steel TECHNICAL FIELD

[0001] The present application relates to the field of rolling technology, in particular to a rolling method for reducing carbide network level of high-carbon chromium bearing steel. BACKGROUND

[0002] High-carbon chromium bearing steel belongs to hypereutectoid steel, during the cooling process after rolling, excess secondary carbide is precipitated along the austenite grain boundary, during spheroidizing annealing process, the secondary carbide network distributed along the austenite grain boundary, after final heat treatment (quenching + tempering), presents carbide network structure. If normalizing is used to eliminate the network carbide, the process and cost will be increased, and the problem of uneven carbide will be caused.

[0003] Carbide network structure increases the brittleness of steel and reduces the fatigue life of bearing parts. In the rolling process, if the segregation by diffusion annealing is not improved, the network level must be reduced by reducing the finish rolling temperature and increasing the cooling rate after rolling. In order to avoid this temperature, a large amount of water cooling is required. However, in the actual production process, the rolling process is: water cooling after rolling - double-length segmentation - cooling on cooling bed, segmentation is cut by segmented shear, but the temperature after water cooling is too low, the hardness of the rolled material is high, and the equipment shear cannot guarantee normal operation. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a rolling method for reducing carbide network level of high-carbon chromium bearing steel.

[0005] In order to solve the above technical problems, the technical scheme of the present application is as follows:

[0006] A rolling method for reducing carbide network level of high-carbon chromium bearing steel, in turn comprising: billet heating - descaling - rough rolling - medium rolling - controlled rolling - intermediate material type segmentation - finish rolling - controlled cooling - cooling bed cooling.

[0007] As a preferred scheme of the rolling method for reducing carbide network level of high-carbon chromium bearing steel, wherein: the temperature of the rolled piece before the cooling bed cooling treatment is controlled at 630℃±20℃.

[0008] As a preferred scheme of the rolling method for reducing carbide network level of high-carbon chromium bearing steel, wherein: the cooling bed cooling comprises:

[0009] When the diameter of the rolled piece is less than or equal to 55mm, air cooling is used for cooling, and when the diameter of the rolled piece is greater than 55mm, stack cooling is used for cooling.

[0010] As a preferred scheme of the rolling method for reducing the carbide network level of high-carbon chromium bearing steel, the finishing rolling temperature is controlled at 820℃±10℃.

[0011] As a preferred scheme of the rolling method for reducing the carbide network level of high-carbon chromium bearing steel, the intermediate material type segmentation comprises segmenting the rolled piece by using a segmenting shear.

[0012] The present application has the following beneficial effects:

[0013] The present application adjusts the rolling process by improving the rolling process and adopting the mode of segmenting first and cooling later, thereby not only avoiding the problem that the equipment shear cannot ensure normal operation due to the high hardness of the rolled piece after rolling and the water temperature being too low, but also achieving the effect of reducing the carbide network level and avoiding the increase of process and cost caused by the unqualified carbide network of the rolled piece. DETAILED DESCRIPTION

[0014] In order to make the content of the present application more easily understood, the present application will be further described in detail below according to the specific embodiments and in combination with the accompanying drawings.

[0015] The traditional rolling process of high-carbon chromium bearing steel is as follows: billet heating - descaling - rough rolling - intermediate rolling - controlled rolling - finishing rolling - controlled cooling - double-length segmentation - cooling bed cooling. The temperature of the billet is relatively low after the controlled cooling, which leads to the high hardness of the rolled piece and the inability of the equipment shear to ensure normal operation.

[0016] The present application provides a rolling method for reducing the carbide network level of high-carbon chromium bearing steel, which comprises the following process steps in sequence: billet heating - descaling - rough rolling - intermediate rolling - controlled rolling - intermediate material type segmentation - finishing rolling - controlled cooling - cooling bed cooling.

[0017] The rolling method adopts the mode of segmenting first and cooling later to adjust the rolling process, which not only enables the equipment shear to segment normally, but also enables rapid cooling.

[0018] The temperature of the rolled piece needs to be controlled at 630℃±20℃ during the cooling bed cooling, which can effectively reduce the carbide network level of high-carbon chromium bearing steel.

[0019] During the cooling cooling zone treatment, if the diameter of the rolled piece is less than or equal to 55mm, air cooling is adopted for cooling; if the diameter of the rolled piece is greater than 55mm, stack cooling is adopted for cooling.

[0020] In the rolling method, the finishing rolling temperature is controlled at 820℃±10℃.

[0021] The present application will be described below with specific embodiments:

[0022] Table 1 is the use of water tank, channel, segmented shear of different specifications of rolled material.

[0023]

[0024] Table 1

[0025] According to the production specification, different specifications adopt different times of steel tapping, adopt different segmented shear, discard the 5# flying shear segmentation function, and only keep the broken function. As shown in Table 1, among them, 10V, 12V steel tapping adopts 2# flying shear segmentation; 14V and 16V steel tapping adopts 3# flying shear segmentation; 18V and 20V steel tapping adopts 4# flying shear segmentation. According to the rolling specification, the opening degree and flow of the water tank are adjusted, the final rolling temperature is controlled at 820±10℃, the temperature on the cooling bed is controlled at 630℃±20, and then the specifications φ≤55mm are air cooled, and the specifications φ>55mm are stack cooled.

[0026] Therefore, the technical scheme of the present application improves the rolling process, not only avoids the problem that the equipment shear cannot guarantee normal operation due to the high hardness of the rolled material after rolling and the water temperature is too low, but also realizes the effect of reducing the carbide network level, and avoids the increase of process and cost caused by unqualified carbide network of the rolled material.

[0027] In addition to the above embodiments, the present application can have other implementation manners; any technical scheme formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present application.

Claims

1. A rolling method for reducing the carbide network level in high-carbon chromium bearing steel, characterized in that: In order, they include: Billet heating—descaling—rough rolling—intermediate rolling—controlled rolling—intermediate material segmentation—finish rolling—controlled cooling—cooling bed cooling.

2. The rolling method for reducing the carbide network level of high-carbon chromium bearing steel according to claim 1, characterized in that: The temperature of the rolled piece before the cooling bed is controlled at 630℃±20℃.

3. The rolling method for reducing the carbide network level of high-carbon chromium bearing steel according to claim 1, characterized in that: The cooling bed includes: Air cooling is used when the diameter of the rolled piece is less than or equal to 55 mm, and stack cooling is used when the diameter of the rolled piece is greater than 55 mm.

4. The rolling method for reducing the carbide network level of high-carbon chromium bearing steel according to claim 1, characterized in that: The finishing rolling temperature is controlled at 820℃±10℃.

5. The rolling method for reducing the carbide network level of high-carbon chromium bearing steel according to claim 1, characterized in that: The intermediate material segmentation includes: segmenting the rolled piece using a segmented shear.

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