Method for reducing strip carbide width and carbide particle size of high-carbon-chromium bearing steel

Abstract

The invention discloses a method for reducing strip carbide width and carbide particle size of high-carbon-chromium bearing steel, which comprises the following steps: continuous casting: producing a high-quality casting blank, and reducing segregation of the original casting blank; casting blank classification: the original casting blank is subjected to acid pickling treatment and carbon segregation detection, and the high-quality casting blank for rolling is selected according to the acid pickling low-power rating result and the carbon segregation index of the casting blank; heating: the selected casting blank is heated, the temperature of a high-temperature section of the casting blank ranges from 1,200 DEG C to 1,240 DEG C, the heating time of a center high-temperature section of the casting blank ranges from 2 h to 5 h, and after the requirement for high-temperature diffusion time is met, the temperature of a soaking section of the casting blank is reduced in a period before tapping, so that the temperature difference between the inside and the outside of the casting blank is formed; rolling: deformation permeates into a core part through the temperature difference between the inside and the outside in the thickness direction of the casting blank, and the final rolling temperature of the last pass is controlled to be 920-980 DEG C; and controlled cooling: quick cooling is carried out after a finish rolling unit. According to the method, the strip carbide width of the high-carbon-chromium bearing steel is reduced, and the carbide particle size is refined.

Description

technical field [0001] The invention belongs to the technical field of metallurgical technology of bearing steel, and more specifically relates to a method for reducing the width of strip-shaped carbides and the particle size of carbides in high-carbon chromium bearing steel. Background technique [0002] High carbon chromium bearing steel is the most commonly used bearing steel in bearing manufacturing, such as commonly used GCr15 and GCr15SiMn. Since high-carbon chromium bearing steel belongs to hypereutectoid steel, element segregation will be formed due to dendrite growth in the steel during continuous casting and solidification, and carbide-enriched bands will be formed when they are extended during hot rolling deformation. The width of carbides and the size of carbide particles significantly affect the fatigue life of bearing steels. [0003] Although measures such as low superheat casting, electromagnetic stirring, and light reduction at the end of solidification can...

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Problems solved by technology

[0003] Although measures such as low superheat casting, electromagnetic stirring, and light reduction at the end of solidification can improve the segregation of high-carbon chromium bearing steel slabs, the subsequent heat treatment, rolling, and cooling are also beneficial to reduce segregation and achieve uniformity. There are some methods to reduce banded carbides in the prior art, but they cannot effectively control the banded carbide width and carbide particle size in high carbon chromium bearing steel

For example, in patent CN108823385B, it is proposed to match the corresponding heating time according to the test results of the slab density to reduce the bearing steel banding, but it does not mention the segregation that has an important impact on the banding, and adjust the previous process according to the feedback of the slab inspection results. The process of continuous casting process has hysteresis

Patent CN107385175B discloses a deformation method for reducing the level of GCr15 bearing steel strip carbides. On the one hand, the specified rolling temperature of 780-820°C is relatively low, which requires high capacity of rolling equipment, and under conventional rolling conditions , the pass design of each pass has determined the deformation of the blank, and it is not easy to adjust flexibly. On the other hand, this method mainly relies on the final low-temperature deformation to reduce the width of the ribbon-shaped carbides, but it does not eliminate the phenomenon of large-grained carbides.

Patent CN112662934A relies on the large reduction of the first few passes of continuous casting and rough rolling, and prolongs the heating time to reduce the band structure of 100Cr6 carbide in bearing steel, without comprehensively considering the influence of subsequent rolling on band carbide

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