By eliminating the work hardening of the stainless steel tube, satisfactory metallographic structure can be obtained, and the process equipment is bright annealing furnace, which is mainly used for heat treatment of the finished stainless steel products under the protective atmosphere. When the stainless steel pipe performance requirements are different, the requirements of the microstructure after bright annealing are different, so the process of bright heat treatment will also be different.
The typical heat treatment process of 300 series austenitic stainless steel tube is solution treatment. In the heating process of the carbide into austenitic stainless steel is heated to 1050 to 1150 DEG C, the thermal insulation for a short time, can put all the carbides dissolved in austenite, and then rapidly cooled to 350 DEG C, can obtain the supersaturated solid solution of unidirectional austenite body is uniform. The key point of this heat treatment process is to rapidly cool down, that is, the cooling rate should be 55 /s, and then the temperature zone (550~850 C) will be rapidly removed after the solid solution of carbide. In addition, the stainless steel tube insulation time should be as short as possible, otherwise it will make coarse grain, affecting the surface finish.
The heating temperature of 400 series ferritic stainless steel is relatively low (about 900 degrees), and to a large extent slow cooling is used to obtain annealed softening structure. The annealing method used for martensitic stainless steel can also be treated by sectional quenching and re tempering.
From the above introduction, we can know that the 300 series and 400 series are different in the heat treatment processing technology, and in order to get the qualified metallographic structure, it is necessary to adjust the cooling section equipment of the bright annealing furnace. Therefore, the advanced light annealing furnace usually adopts the strong convection cooling in its cooling section, and sets three cooling sections, which can adjust the air volume independently. The strip width is divided into three sections along the width direction of the strip, and the cooling speed of the strip width direction is adjusted by the air flow diversion, and the plate shape is controlled.
There is an important problem in the heat treatment of cold rolled strip for stainless steel tube, that is to say, the whole strip is uniform in width and length. Muffle type bright annealing furnace with large size muffle tube from the muffle tube evenly heating air flow organization external spiral around over the strip, uniform heating. In order to ensure the uniform organization of the strip along the length, the linear speed of the stainless steel strip in the reheating furnace must be kept unchanged. Therefore, the adjustable roller tension adjustment device is equipped before and after the advanced vertical bright heat treatment furnace. It should not only make the steel import and export speed to meet the speed requirements of heat treatment, should not affect the amount of empty or full sets of sets of sets, but also according to the situation of the establishment and precision plate strip small tension adjusting strip, stainless steel plate to meet the requirements of.
Source: China Stainless Steel Tube Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)