Production method of round steel for high-strength bolt capable of resisting impact at -40 DEG C

Abstract

A production method of round steel for a 10.9-grade high-strength bolt capable of resisting impact at -40 DEG C comprises the following steps: (1) smelting molten iron and scrap steel, which are adopted as raw materials, by using an ultrahigh-power eccentric bottom type electric furnace; (2) refining the materials through an LF refining furnace; (3) degassing through a VD vacuum furnace, and feeding in a cored wire and B iron; (4) performing continuous casting treatment through an arc-shaped continuous casting machine; (5) heating steel billets by a walking beam furnace; (6) rolling steel; (7) controlling cooling; (8) slowly cooling; and (9) performing heat treatment. Compared with 42CrMoA, the production cost can be reduced by 330 yuan / ton at least when the steel for the wind power bolt with the diameter being smaller than or equal to 30 mm is produced.

Description

technical field [0001] The invention relates to the technical field of round steel production, in particular to a method for producing round steel for low-cost, small-sized, -40° C. impact-resistant 10.9-grade high-strength bolts for free annealing and cold drawing. Background technique [0002] In recent years, with the rapid development of various industries such as wind power, machinery, construction, and light industry in China, higher requirements have been placed on the materials used in the manufacture of various fasteners (such as bolts, nuts, etc.). Higher strength and better impact toughness are required. At present, it has been widely used to produce 10.9 grade bolts after heat treatment and tempering of CrMo steel. The inventor has also applied for the production method of round steel for ultra-high strength bolts, in order to produce tensile strength requirements > 1400MPa, used in 14.9 grade ultra-high-strength bolts. Round steel on high-strength bolts; how...

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Problems solved by technology

[0005] Specifically, the technical problem to be solved by the present invention is: to provide a low-cost small-size 10.9-grade -40°C impact-resistant high-strength round steel production method for cold-drawn anneal-free bolts to solve the problem of poor hardenability of the product, and 40Cr It is not resistant to low temperature impact, so the composition of the product is redesigned to adopt the smelting composition design of adding 0.0008-0.0035% B by mass fraction to the traditional medium carbon chromium steel

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