style="font-size:16px;">1. Annealing
Heat the wire rod to an appropriate temperature, maintain it for a certain period, and then cool it slowly to adjust the crystalline structure, reduce hardness, and improve the room-temperature processability of the wire rod.
Purpose: Remove the oxide film on the surface of the wire rod and form a phosphate film on the metal surface to reduce scratches on tools and dies during wire drawing, cold heading, forming, and other processing steps.
Cut the wire rod and head it into a screw blank, forming the head, creating cross recesses (or other head types), thread blank diameter, shank length, under-head fillets, etc.
Roll or tap the formed semi-finished product to achieve the required threads. Practically, this process is called "thread rolling" for bolts (screws) and threaded rods, and "tapping" for nuts.
Enhance the strength, hardness, and toughness of the screw. A good screw must not be too hard—otherwise, it may break during tightening—nor too soft—otherwise, it may easily strip and fail to fasten tightly. Therefore, heat treatment is necessary to give the screw the property of being hard on the outside and tough on the inside.
Surface treatment refers to the process of forming a coating on the workpiece surface through specific methods. Its purpose is to impart an attractive appearance and corrosion resistance to the product.
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JIALI FASTENER