Seamless rectangular tube heat treatment has three advantages

   In order to improve the surface hardness and wear resistance of the rectangular tube, seamless square rectangular tube manufacturers can carry out some surface treatment, that is, flame surface quenching, high and medium frequency surface quenching and some chemical heat treatment. Generally speaking, high and medium frequency surface quenching is mostly, and its heating temperature is 850-950 ℃. Considering its poor thermal conductivity, the heating speed cannot be too fast, otherwise it will produce defects of melting and some quenching cracks. High-frequency quenching requires seamless square tube after normalizing the matrix tissue is mainly pearlite. Cooling water spray or spray polyvinyl alcohol aqueous solution, tempering temperature in the range of 200-400 ℃, hardness in the 40-50HRC, can ensure the hardness and wear resistance of the surface of the seamless rectangular tube.



In addition, seamless rectangular tube heat treatment also has the following three advantages:


(I) Dimensional Stability For high-precision seamless rectangular tubes, it requires high precision, so dimensional stability must be maintained. Due to the slow cooling speed of straightening in the air, it has the effect of stabilization and will increase the number of residual seamless rectangular tubes in the organization, so cold treatment must be carried out;


(II) Reduce Quenching Deformation Because seamless rectangular tubes are slender, they are easy to deform during quenching, so their deformation must be strictly controlled. Heat treatment is a very critical process. In the quenching and cooling process, cold plasticity is used for timely correction, which is the key step to ensure the improvement of the qualified rate. Therefore, thermal bath quenching or cooling in oil for a certain period of time should be carried out for thermal correction.


At the same time, hanging heating should be carried out during heating to reduce the deformation of quenching. For high-precision guide rails, gas nitriding or ion nitriding should be carried out to reduce the deformation;


(III) high hardness seamless square rectangular tube mainly bear contact fatigue load, it must have high hardness, so it should be quenched, or surface quenching or chemical heat treatment, followed by low temperature tempering treatment.