Rolling method capable of reducing hot-rolled hardness and curvature of 42CrMo

A curvature and hardness technology, applied in the field of rolling to reduce the hardness and curvature of 42CrMo in the hot-rolled state, can solve the problems of production organization and downstream users, easy formation of cracks, fractures, and large curvature in the hot-rolled state, etc. The effect of shortening the production cycle, improving the hardness of the hot-rolled state, and improving the bending degree

CN109013715AActive Publication Date: 2018-12-18NANJING IRON & STEEL CO LTD
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Publication Date
2018-12-18

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Abstract

The invention discloses a rolling method capable of reducing hot-rolled hardness and curvature of 42CrMo. The rolling method comprises the following steps of: (1) performing step type heating on blank; (2) rolling the blank; and (3), cooling the rolled steel. A metallographic microstructure of 42CrMo rolled by the method is ferrite, pearlite and bainite, and prevents a central area of the steel from generating a great deal of the needle-like martensite structure which is in blocky distribution, is high in strength and hardness, and is relatively poor in plasticity. The rolling method effectively improves the hot-rolled hardness of steel to be 240-300HB, and also solves the problem that curvature is worsened as a result of hardness reduction, so that the hot-rolled curvature of the steel is97.34% or higher within 0.4%. Hot-rolled direct delivery use is met, the hardness does not need to reduce by follow-up annealing, and the curvature does not need to improve by straightening. The production period is shortened, and production consumption is reduced.
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Description

technical field

[0001] The invention relates to a steel rolling process, in particular to a rolling method for reducing the hardness and curvature of 42CrMo in a hot-rolled state. Background technique

[0002] 42CrMo is a common steel used in mechanical engineering and has a wide range of uses. It is mainly used in the manufacture of bolts, gears, gear shafts, shafts, and other equipment parts. In the production process of this steel type, there are problems of large bending degree and high hardness in the hot-rolled state, resulting in difficulty in blanking. And it is easy to form defects such as cracking and fracture during cold shearing, rod shrinkage, drawing and other processing. Although it meets the requirements of "GB / T 702-2017 Hot Rolled Steel Bar Size, Shape, Weight and Allowable Deviation", it still causes great troubles to production organizations and downstream users. Contents of the invention

[0003] Purpose of the invention: In order to overcome the def...

Examples

Embodiment Construction

[0015] Below, the present invention will be described in further detail in conjunction with the accompanying drawings.

[0016] A rolling method that reduces 42CrMo hot-rolled state hardness and curvature, comprises the steps:

[0017] (1) Heating: The purpose of this step is to heat the billet to the temperature range of the austenite single-phase solid solution structure, and have enough time to homogenize and dissolve carbides, thereby improving the shaping of the steel, reducing deformation resistance, and improving the internal structure. and performance for easy rolling. The specific requirement is to carry out step-by-step heating on the blank, and the step-by-step heating includes a non-heating section, a preheating section, a heating section, a heating section, a soaking section, and a soaking section; The temperature of the heating section is 600-850°C, the heating rate is 0.180-0.254°C / s, the temperature of the preheating section is 800-1020°C, the heating rate is ...