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Manufacturing process of high-strength bolts
Added:2021-06-28     Views:    

The process of high-strength bolts is: hot-rolled wire rod-(cold drawing)-spheroidizing (softening) annealing-mechanical descaling-pickling-cold drawing-cold forging forming-thread processing-heat treatment-inspection

Cold heading steel is a high-strength bolt steel with high interchangeability produced by cold heading forming process. Because it is formed by metal plastic processing at room temperature, the deformation of each part is large, and the deformation speed it withstands is also high. Therefore, the performance requirements of the cold heading steel raw materials are very strict.

 For medium-carbon steel and medium-carbon alloy steel with a large amount of high-strength bolts, spheroidizing (softening) annealing is carried out before cold heading in order to obtain uniform and fine spheroidized pearlite to better meet the actual production needs.

The process of removing iron oxide plate from cold heading steel wire rod is stripping and descaling. There are two methods: mechanical descaling and chemical pickling. Using mechanical descaling to replace the chemical pickling process of wire rods not only improves productivity, but also reduces environmental pollution.

High-strength bolt drawing process

The drawing process has two purposes. One is to change the size of the raw material; the other is to obtain basic mechanical properties of the fastener through deformation strengthening. For medium carbon steel and medium carbon alloy steel, there is another purpose, that is, to make wire rod The flake cementite obtained after controlled cooling is cracked as much as possible during the drawing process to prepare for the subsequent spheroidizing (softening) annealing to obtain granular cementite. However, some manufacturers arbitrarily reduce the drawing in order to reduce the cost. For passes, the excessive reduction in surface area increases the work hardening tendency of the wire rod wire and directly affects the cold heading performance of the wire rod wire.

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