Various fasteners are usually made from cold tantalum steel. In terms of variety classification, the steel used for fasteners is stainless steel, high-temperature alloy steel, aluminum-magnesium alloy, monel, etc. in addition to ordinary carbon steel. Among them, stainless steel and non-ferrous metals account for about 5%-7% of the total consumption of consumables. The steel grades of cold-rolled steel wire rods and wire rods are generally low- and medium-carbon high-quality carbon structural steels and low-alloy steels. Low carbon cold heading steel is mainly used for cold heading nuts. The materials for bolts and screws are mainly medium carbon steel (ML35 and SWRCH35K), which are grade 8 and above after quenching and tempering treatment.
The fasteners can be made of steel, non-ferrous metals, stainless steel, titanium alloys or other engineering materials. The processing method can be hot processing or cutting, but more than 90% of them are processed by cold chilling agent, and the precision of the products manufactured by the process. High quality, good quality and high production efficiency, China's fastener industry has maintained a steady double-digit growth for three consecutive years. Although the proportion of non-ferrous metals and composites is increasing year by year, the role of steels used in high-strength fasteners is irreplaceable.
Cold heading is plastically formed using metal at normal temperature. Cold heading performance is one of the important properties of cold heading steel. Its performance is mainly characterized by good cold formability; it has the least possible resistance to deformation and possibly high deformation ability. Cold heading steel has good cold forming performance, and it is processed by cold drawing instead of hot rolling material cutting machine in the machining industry. The advantage of this process is that while saving a lot of man-hours, metal consumption can be reduced by 10%-30%, in line with clean production. The production of resource-saving enterprises is large, and the product has high dimensional accuracy, good surface finish and high production efficiency. It is an advanced machining process that is mainly promoted. Therefore, the use of cold heading process to manufacture fasteners is not only efficient, good quality, but also saves materials and costs.
The steel mills with Baosteel, Maanshan Iron and Steel, Xinggang, Xiangtan Iron and Steel and Hangzhou Steel, which have established cooperative relations with the fastener industry, have formed the industrial cluster of cold-rolled wire rods in China. The products are made up of low-carbon, ultra-low-carbon, medium-carbon (tempered and tempered), low-alloy alloy steel and surface carburizing and hardening steel. The specifications range from 5.5 to 42 mm, covering almost all the requirements for fastener steel. .
Although the development of domestic cold-rolled steel wire rods and wire rods started late, it has developed rapidly. Especially after the mid-1980s, high-speed wire rod production lines and wire rod continuous rolling production lines have been put into production, which are cold-rolled steel wire rods and wire rods. The production provides a guarantee of equipment. At the end of 2005, the production capacity of cold-rolled wire rods reached 6 million tons/year (about 10-12% of the total wire rod).
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