CARBON SPRING STEEL WIRE

It has high tensile strength, elastic limit, toughness and fatigue strength, and is resistant to impact and vibration. Ensuring strength and toughness indicators, especially preventing torsion cracks, is the key to producing spring steel wire. The intrinsic quality and surface quality of the wire rod directly affect the performance of the wire. Carbon spring steel wire is made of high-carbon high-quality carbon structural steel or carbon tool steel wire rod, and its chemical composition, gas content and non-metallic inclusions must be strictly controlled according to the purpose of the spring. In order to reduce surface defects and decarburization layer, the steel billet for producing wire rods must be surface ground and peeled if necessary. The wire rod must be normalized or sulphurized, and large specifications must be replaced by spheroidizing annealing. Sulphurization treatment is widely used in intermediate heat treatment, especially before the finished product is drawn. Decarburization should be prevented during heat treatment. After heat treatment, sulfuric acid or hydrochloric acid pickling is used to remove iron oxide scale. Coating (see lubricating carrier) can be lime dipped, phosphating, borax treatment or copper plating. The drawing process of the finished product drawing has a great influence on the product performance. Generally, a larger total reduction rate of about 90% (see area reduction rate) and a smaller pass reduction rate (about ≤23%) are used to ensure the toughness of the product. For high-strength spring steel wire, the outlet temperature of each pass of the steel wire should be controlled below 150℃ during drawing to prevent the steel wire from torsional cracks due to strain aging, which is the main defect causing the scrapping of the steel wire. For this reason, good lubrication and sufficient cooling must be provided during drawing. Using a smaller pass reduction rate and drawing speed will help reduce the temperature rise of the steel wire. After drawing, there is a large residual stress in the steel wire, which affects its performance. It can be eliminated by online straightening or low-temperature (180-370℃) heating.