Cold heading technology of high strength bolt

During the cold heading process of high strength bolt, the original microstructure will directly affect the formability of cold heading. The stud manufacturer's stud is a kind of fastener with high strength and rigidity. The stud is the abbreviation of cheese head studies for arc stud welding. The specification of the stud is nominal diameter of Ф 10 ~ Ф 25mm, and the total length before welding is 40 ~ 300 mm. The welding pin has the head top surface, and the manufacturer's identification mark is made by convex characters, so the welding pin is widely used. High strength bolts are made of high strength steel or need to be applied with large pre tightening force.
In the process of cold heading, the plastic deformation of local area can reach 60% - 80%, so the steel must have good plasticity. When the chemical composition of the steel is determined, the metallographic structure is
It is generally considered that coarse pearlite is not conducive to cold forming, and fine spherical pearlite can significantly improve the plastic deformation ability of steel.
Medium carbon steel, medium carbon alloy steel, high strength bolts, spheroidizing annealing before cold rolling, obtaining uniform and fine spheroidized pearlite, better filling
Meet the actual production needs. If the heating temperature of softened annealed carbon steel wire rod is selected at the critical point where many steels keep downward, the heating temperature is generally not too high, otherwise three green carburizing precipitate along the grain boundary, resulting in cracking and cold heading, and for the wire rod used for isothermal annealing of carbon steel ball, the furnace is heated and cooled to just below 0

For a period of time, the temperature is about 700 degrees Celsius, and then the furnace is cooled to about 500 degrees Celsius for air cooling.
The microstructure of high strength bolt steel changes from coarse to fine, from sheet to spherical, and the cracking rate of cold heading will be greatly reduced. The softening annealing temperature of 3545ml35swrch35k steel is usually 715-735 ℃.
The company's main business: high strength bolt, high strength nut, steel structure bolt, steel structure nut, grid sealing plate, grid bolt, etc.