This process is composed of a hardening, subzero treatment and tempering. Hardening: Hardening is done to achieve a high delicacy in its structure without decarburization. Subzero treatment; Putting needles into a deep cooling treatment at a temperature of minus 100°C to stabilize their microstructure. Tempering; By tempering needles get the best elasticity and durability suitable for high speed sewing work.