A method of controlled rolling and controlled cooling of large-scale high-carbon chromium bearing steel

Abstract

The invention relates to the field of iron and steel manufacturing, and discloses a rolling and cooling control method of large-specification high-carbon chromium bearing steel. The rolling and cooling control method comprises the following steps that a plurality of large-specification high-carbon chromium bearing steel rolled pieces obtained after roughing are subject to air cooling at the same time; the rolled pieces obtained after air cooling are subject to finish rolling; and the rolled pieces obtained after finish rolling are subject to graded water cooling. The production process that air cooling of the multiple rolled pieces obtained before finish rolling and graded water cooling of single rolled pieces obtained after finish rolling are combined is adopted in the method. By means of the rolling and cooling control method, under the condition that the rolling rhythm is not influenced, the time of air cooling before finish rolling is controlled, and rolling temperature of large-specification bars within two-phase zone scope is achieved; graded water cooling after finish rolling is used in a combined manner, cooling speed after finish rolling is controlled, and therefore the effect of reducing network carbide grade of the large-specification bearing steel us achieved.

Description

technical field [0001] The invention relates to the field of iron and steel manufacturing, in particular to a controlled rolling and controlled cooling method for large-scale high-carbon chromium bearing steel. Background technique [0002] High-carbon chromium bearing steel is a type of bearing steel and is the most commonly used steel for manufacturing bearings and bearing parts. The most commonly used high carbon chromium bearing steels are GCr15 and GCr15SiMn. [0003] At present, the temperature-controlled rolling process of high-carbon chromium bearing steel bars is to use pre-water cooling to quickly cool the surface of the rolled piece before finishing rolling, and then apply a certain amount of rolling deformation after a certain period of time to equalize the temperature; after finishing rolling, use Water cooling cools the rolled piece to a certain temperature, so as to obtain the required structure and properties. [0004] This process is ideal for temperature-...

AI Technical Summary

Problems solved by technology

For bearing steel with a diameter greater than 80mm, the section of the blank used is generally 76000mm 2 (Equivalent to a square billet with a side length of 275mm), the specification of the pre-water-cooled rolled piece is about Φ115mm, and the temperature gradient of the core surface after cooling is too large, so it is difficult to achieve the effect of temperature-controlled rolling with pre-water cooling

[0006] 2) The heating temperature is higher

[0008] 4) The internal stress of the rolled piece is relatively large

Due to the large size of the billet and product and the high requirement for temperature drop, if water cooling with a faster cooling rate is adopted, the temperature difference and internal stress of the core surface of the rolled piece will be large, which will easily cause surface defects

[0009] 5) The average temperature distance is longer

Usually, it is difficult to realize due to the limitation of site conditions

[0010] Since there is no suitable controlled rolling and controlled cooling process for large-scale bearing steel bars at present, only conventional hot rolling process can be used, and the level of reticular carbide is high, which increases the heating or heat treatment cost of downstream processes

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