Method for manufacturing spheroidizing-free high-quality high-strength cold forging steel

Abstract

The invention relates to a method for manufacturing steel, in particular to a method for manufacturing spheroidizing-free high-quality high-strength cold forging steel. The cold forging steel comprises the following components in percentage by weight: 0.25 to 0.40 percent of C, 0.45 to 0.85 percent of Mn, 0.05 to 0.35 percent of Si, 0.70 to 1.45 percent of Cr, 0.03 to 0.45 percent of Mo, 0.015 to 0.030 percent of Alt and the balance of Fe and inevitable impurity elements. In a rolling process, after a casting blank is heated, the billet discharging temperature is 900-1,120DEG C, the finish rolling temperature is 720-850DEG C, and the spinning temperature is 800-860DEG C; and in a Stelmor air cooling line controlled cooling process, the steel is cooled to the temperature of between 650 and 800DEG C at a rate of 3-8DEG C / s, enters a hood, and is cooled in the hood at a rate of 0.2-0.7DEG C / s. The conventional controlled rolling and controlled cooling process is reasonably set, the function of the controlled rolling and controlled cooling process in the structure control aspect is fully exerted, ideal structures are controlled, the problem of cold heading cracking is greatly reduced, the yield of finished standardized part products is improved, the production cost is reduced and the economic benefit is improved.

Description

technical field [0001] The invention relates to a method for manufacturing steel, in particular to a method for manufacturing high-quality high-strength cold heading steel without spheroidizing annealing. Background technique [0002] During the "Twelfth Five-Year Plan" period, the my country Association of Automobile Manufacturers predicted that the development speed of complete vehicles is much faster than that of automotive fasteners. The next few years will be a period of rapid development of automotive fasteners and a great opportunity to expand the production of fasteners. Due to the advantages of imported materials such as good hardenability, high purity and stable assembly, the high-grade fastener market has long been occupied by foreign products. [0003] In domestic steel enterprises, in the production of wire rods with ferrite and pearlite as the main structure, due to reasons such as unreasonable control of the temperature of the hood and the cooling rate in the ...

AI Technical Summary

Problems solved by technology

[0003] In domestic steel enterprises, in the production of wire rods with ferrite plus pearlite as the main structure, due to reasons such as unreasonable control of the temperature in the hood and the cooling rate in the hood, it is easy to cause uneven distribution of ferrite structure and uneven grain size. Uniformity, overall coarse grains, etc., will lead to a decrease in cold heading performance

At the same time, the wire rod undergoes spheroidizing annealing, which increases production costs and easily causes surface decarburization and other phenomena.

In this way, the microstructure and mechanical properties of the wire rod are not uniform, resulting in problems such as cracking in cold heading processing and low processing rate, which brings great inconvenience to the processing and use of downstream customers.

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