Different types of spring steel wire have different production methods, and the common characteristics are that they require certain strength, high toughness and good coil spring performance.
The process for making various spring steel wires is as follows:
The process of drawing spring steel wire: (steel) wire rod - surface treatment - drawing (mattress wire can be used this method)
Lead quench spring steel wire: lead bath hardening in the middle specification of wire rod size or cold drawing, then surface treatment and wire drawing.
Galvanized spring steel wire: usually in the finished size of hot plating or electroplating, but also with wire rod pickling, hot dip after cold drawing to the specified size.
Oil tempered spring steel wire: according to the need of the use of carbon steel or alloy steel, surface treatment and drawing to the finished size after quenching and tempering treatment, this process in the steel wire with more automobile suspension spring and valve spring, of course, can also use ordinary spring.
Surface treatment: generally use acid washing phosphating, removal of oxide sheet, forming phosphating film; also a small number of mechanical methods used to deal with. The purpose is to meet the requirements of cold drawing process and obtain smooth surface. The spring wire requires high fatigue life, such as valve spring wire, wire rod for coping descaling treatment, reduce surface defects, if the steel can be grinding in the billet, but also beneficial to reduce defects.
Drawing: the great influence of drawing process of finished drawing process on the performance of the product, generally use the surface total reduction rate of about 90% of the larger (see area reduction rate) channel and smaller reduction rate (about 10%-20%), in order to ensure the toughness of products. For high strength spring steel wire, it is necessary to control the exit temperature of each steel wire below 150 degrees during the drawing process, so as to prevent the steel wire from reverse torsion due to strain aging, which is the main defect of steel wire scrap. Therefore, it is necessary to have good lubrication and sufficient cooling during drawing, and reducing the temperature rise of steel wire by adopting smaller pass reducing rate and drawing speed.
Heat treatment: spring steel wire commonly used lead bath quenching process of carbon steel, can obtain very fine pearlite (sorbite), are beneficial to improve the deep drawing performance and the performance of a spring, alternative process of fluidized bed lead bath is not promotion, only in some small diameter on the application. The alloy steel wire is usually treated by annealing, so that the microstructure is suitable for drawing deformation. The heat treatment of stainless steel wire is treated by solid solution, and the purpose is to improve the structure to meet the needs of drawing. The oil quenching process is used on the finished steel wire. The induction heating or gas and fuel heating furnace is adopted to heat the steel wire to the austenitizing temperature for a period of time and then a medium temperature tempering after quenching. Although nominally called oil quenching, water quenching is basically used or water quenching with polymer materials is used.