The production process of hex bolt is divided into 7 steps, namely annealing, pickling, wire drawing, forming, grinding, and heat treatment grade surface treatment.
Annealing process: The first treated product is put into the furnace and then closed with the furnace cover. One furnace can handle 8.4 tons at the same time. Then slowly raise the temperature to the specified temperature, this step takes 3-4 hours. Then slowly bring the temperature to 550 degrees, which will take 3-4 hours, and let the product cool down to room temperature naturally. This process can adjust the crystal structure, reduce the hardness, and improve the workability of the wire at room temperature.
Pickling process: The purpose of pickling is to remove the oxide film of the wire. Now the entire disc is invaded into three hydrochloric acid tanks with a concentration of 20-35 at room temperature for a few minutes. Then use clean water to clear the hydrochloric acid corrosion on the surface of the wire. In order to make the film produced by the next process more compact, oxalic acid is used to increase the activity of the metal. When the disc is infiltrated into the phosphate, the surface of the steel is brought into contact with the chemical treatment liquid, and the treatment liquid and the steel are dissolved to form a compound, which is attached to the surface of the screw to form a film. Remove the residue on the surface with clean water. Then use lubricating oil to increase its lubricity.
Wire drawing process: Use the above-mentioned fine drawing and rough drawing for some products to cold draw the plate element to the required wire diameter. This process is suitable for wires used for large screws, nuts, and tooth bars.
Forming process: There are two types of forming of hexagonal bolts: one is four-die four-punch or three-die three-punch, but three-die three-punch. The screws are one die and two punches. Then heat beat, which is divided into three steps. The first step is to put the product into the heating equipment and set the heating time and temperature according to the product specification. In the second step, after heating, the product is moved to a molding machine for molding. Then squeeze it with a rod machine.
Teeth grinding process: The formed semi-finished product can be rolled or tapped to achieve the required thread.
Heat treatment process: In order to improve the mechanical properties of the material, eliminate the residual stress and improve the machinability of the metal, the product needs to be heat treated. According to the needs of the product, there are two methods of preparatory heat treatment and final treatment.
Surface treatment process: Through electroplating, hot dip galvanizing, and mechanical galvanizing, a covering layer is formed on the surface of the product, so that the surface of the product is beautiful and anti-corrosion effect.
