Cold heading process for high-strength bolts

Cold heading process for high-strength bolts

The original structure of high-strength bolt cold heading process in the production of steel will directly affect the cold heading formability. The welding nail manufacturer's welding nail belongs to a type of high-strength and rigid connection fastener. The welding nail is the abbreviation of Cheese head studies for arc stud welding, and the specification of the welding nail is the nominal diameter Ф 10~ Ф 25mm, with a total length of 40-300 mm before welding. Welding nails have the identification mark of the manufacturer made of raised characters on the top surface of the head, and the use of welding nails is very extensive. High strength bolts made of high-strength steel or requiring significant pre tightening force can be referred to as high-strength bolts.

During the cold heading process, the plastic deformation in local areas 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 believed that coarse plate pearlite is not conducive to cold forming, while fine spherical pearlite can significantly improve the plastic deformation ability of steel.

Medium carbon steel, medium carbon alloy steel, high-strength bolts, spheroidized annealing before cold rolling, obtaining uniform and fine spheroidized pearlite for better filling

Meet the actual production needs. Carbon steel wire rods for softening and annealing are selected at a critical point where multiple steels are kept downward. The heating temperature is generally not too high, otherwise three green carbides will precipitate along the grain boundaries, leading to cracking and cold heading. For wire rods used for isothermal annealing of carbon steel balls, the furnace is heated and cooled to just below AC1+(20-30%)

For a period of time, the temperature is approximately 700 degrees Celsius, and then the furnace is cooled to around 500 degrees Celsius for air cooling.

The microstructure of high-strength bolt steel changes from coarse to fine, from sheet to spherical, and the cold heading cracking rate will be greatly reduced. The softening annealing temperature of 3545ML35SWRCH35K steel is usually in the range of 715-735 degrees Celsius.

The company's main products include high-strength bolts, high-strength nuts, steel structural bolts, steel structural nuts, grid sealing plates, grid bolts, etc.