II. Fastener Manufacturing Process (2)

2.2.3 Pickling, Phosphating, and Soaping

• Equipment: Pickling tank, water rinsing tank, phosphating tank, soaping tank.

• Purpose of Pickling: To remove the oxide layer and rust from the surface of the wire rod.

• Purpose of Phosphating: To form a phosphate coating on the metal surface, which reduces friction and abrasion on tools and dies during subsequent processes like wire drawing, cold heading, or forming, providing lubrication. It also offers some rust prevention.

• Purpose of Soaping: To provide lubrication.

• Purpose of Water Rinsing: To prevent carry-over of acid solution into the next tank.

• Inspection of Surface Condition: Phosphate coating, abrasions, scratches, scale.

2.2.4 Wire Drawing

• Equipment: Wire drawing machine, wire drawing die.

• Purpose of Wire Drawing: To provide wire rod of the required specifications for cold heading production.

• Process Description: Wire drawing is a metal forming process where the wire坯 (billet) is plastically deformed by being pulled through a die orifice under tension, reducing its cross-sectional area and increasing its length.

2.2.5 Cold Heading

• Equipment: Cold heading machine, cold heading dies.

• Process Description: Cold heading is a forging method that uses dies to upset and form metal rods at room temperature. It is commonly used to manufacture screws, bolts, rivets, nuts, etc., and can reduce or replace machining processes.

• Material Utilization: The material utilization rate in cold heading can reach 80–90%.

Production Characteristics: Cold heading is typically performed on specialized cold heading machines, facilitating continuous, multi-station, and automated production. These machines can sequentially perform operations such as cutting off, heading, gathering, forming, chamfering, thread rolling, reducing, and trimming. This results in high production efficiency. The bar stock is automatically fed a specific length by a feeding mechanism, a cutting mechanism severs it into blanks, and then a transfer mechanism sequentially moves them to stations for gathering, forming, and piercing for cold heading formation.