What is the method of annealing stainless steel wire

The method of annealing stainless steel wire

        Stainless steel wire is a commonly used industrial material. It needs to be annealed during the drawing process. In order to reduce oxidation and enhance heat transfer capacity, a tubular heating and cooling structure is usually used to reduce the heat treatment space. The use of reducing and high thermal conductivity Hydrogen is filled into the tube as the annealing environment medium. In the current annealing process, the stainless steel wire goes through the pickling section, the water washing section, and the steel pipe in the annealing furnace into the wire take-up machine in order from the pay-off reel. The annealing furnace is composed of a blowing intervention heating section, a heating section and a cooling section to prevent residue on the surface Water stains enter the heating section, and high-speed airflow is used to forcefully sweep the surface of the steel wire in the blowing intervention hot section. Both the preheating section and the heating section adopt electric heating furnace structure. High-temperature stainless steel pipes, the stainless steel pipes filled with hydrogen are heated by radiation and convection heat transfer, and the high-temperature steel wires in the cooling section transfer heat to the outside through radiation and convection. The steel pipes are immersed in a water bath.

        Martensitic stainless steel wire is annealed. The purpose of annealing is to eliminate internal stress and prevent cracks; eliminate work hardening to facilitate continued processing. From the perspective of softening effect, complete annealing is the best, but the annealing temperature is higher, and the surface oxidation of the steel wire is relatively heavy. Therefore, the steel wire raw material and the intermediate softening treatment generally adopt the recrystallization annealing process; the raw material is annealed at about 800℃, and the furnace is cooled to below 650℃, and the heat treatment cycle is 6-7h; the semi-finished product is usually annealed between 750～800℃ and air-cooled after heat preservation The heat treatment cycle is about 5-6h. Martensitic steel cold working residual stress, if not eliminated in time, will often lead to steel cracking. For 1-4Cr13, the semi-finished steel wire after drawing must be heat treated in a 12h internal furnace for 1-4Cr13. Some nickel-containing martensitic steels are equal to 1Cr17Ni2. Due to the effect of nickel, it takes time for austenite to completely decompose into pearlite. Very long, it is difficult to achieve the purpose of softening through annealing, usually high temperature tempering is used to achieve softening. The Japanese JIS standard recommends using two-stage annealing to soften 1Cr17Ni2, the first time is 750°C, air cooling; the second time, 650°C, air cooling. Nevertheless, it cannot be softened below HB230. Ferritic stainless steel wire is annealed to eliminate strain and hardening caused by hot and cold working. After annealing, the tensile strength of the steel wire decreases, and the elongation and corrosion resistance can be improved. Annealing temperature is generally 750-850℃, and air cooling after heat preservation. In order to prevent the coarsening of crystal grains, high-chromium ferritic steel wires often use 650-750℃ low-temperature annealing process. The key to the heat treatment of ferritic steel wire is to prevent the excessive growth of grains caused by overheating, and the residence time in the brittle zone at 475°C is as short as possible. Continuous furnace processing ferritic steel wire, because the time in the furnace is very short, the furnace temperature can be increased to 830 ~ 850 ℃.