Technical

Softening annealing

To prevent cold cracks in steel during cold heading, it is essential to choose steel with good ductility. For medium-carbon steel and medium-carbon alloy steel, which are commonly used for high-strength fasteners, a process called spheroidizing annealing (softening) is performed before cold heading. This process produces a uniform, fine spheroidized microstructure, better meeting the requirements of actual production. For medium-carbon alloy steel wire, isothermal spheroidizing annealing is employed. After heating to AC1+(20-30%), the wire is furnace-cooled to just below Ar1 at approximately 700 degrees Celsius, held isothermally for a period, and then air-cooled to around 500 degrees Celsius. This transformation from coarse to fine microstructure significantly reduces the cold heading cracking rate.

Shelling and descaling

The purpose of descaling (or scale removal) is to eliminate the iron oxide (rust) from the surface of steel. Descaling methods include mechanical descaling and chemical pickling. Compared to chemical pickling, mechanical descaling not only enhances productivity but also reduces environmental pollution.

Cold Calling

The cold drawing process has two purposes: one is to change the size of the raw material; the other is to enable the fastener to obtain basic mechanical properties through deformation strengthening.

Cold forging

The bolt head is formed by cold forging plastic processing, and the required shape is formed by cold heading process, which can provide higher product strength and excellent mechanical properties than cutting processing.

Thread processing

The threads of the bolts are generally formed by cold working methods, using a thread rolling plate (die) to ensure that the plastic flow lines of the threaded part are not cut off, thereby increasing strength and improving quality uniformity.

Heat Treatment

After the thread processing is completed, our product has been initially formed. However, in order to improve the mechanical properties of the material, eliminate residual stress and improve the cutting processability of the metal, we need to heat treat the product. This process includes cleaning, high temperature carburizing and quenching.

Surface Treatment

Finally, based on customer requirements, we can choose whether to apply surface treatments. If requested, we can create protective layers on the product surface through methods such as electroplating, hot-dip galvanizing, or mechanical zinc plating.

Product Testing

After production is completed, our inspection personnel sample the products and conduct comprehensive inspections on aspects such as appearance, dimensions, threads, and mechanical performance. Qualified finished products are then transported to the packaging line and ultimately stored for sale. Of course, during the production process mentioned above, specialized employees also perform first-piece inspections, regular quality checks, and production supervisor inspections to ensure the quality of our products.