Steel bar quenching furnace manufacturers: pre heat treatment before quenching
Before the surface quenching with steel bar quenching furnace, in order to organize the structure for the quenching, the post – forging billets should be properly pretreated, such as normalizing, annealing, quenching and tempering, and spheroidizing, in order to meet the needs of mechanical processing and prepare for the final heat treatment. For some parts with complex shape and high accuracy, stress annealing should be eliminated before rough or fine machining or before quenching.
For example, the rocker shaft made of steel S45C requires the hardness reach to HRC50~55 because of the serious internal stress of raw materials after cutting.So the rocker shaft will have crack at the corner after quenching. If improving the process such as we do 550-600℃ removing stress annealing, then the crack can be removed. For steel parts with large sharp angle, large cross-section and large residual internal stress before quenching, high temperature tempering or low temperature annealing before quenching can be used to prevent the quenching crack.
There is not only a larger internal stress but also a microcrack in the stamping process, which may lead to the quenching and cracking of the workpiece when the steel bar quenching furnace is quenched. If annealing or tempering is carried out before quenching, it is effective to prevent cracks.
For subeutectoid steel, the overheated Wechsler structure must be eliminated before quenching with steel bar quenching furnace, because the Wechsler structure is very harmful to mechanical properties and quenching cracking. Therefore, the steel plate used in the factory should be normalised or annealed after cutting by oxygen acetylene, so as to eliminate the overheated structure at the incision. In order to eliminate the superheated structure of medium carbon steel, it should be heated at a slightly higher temperature than normal annealing temperature, and then cooled down at a faster rate to prevent the precipitation of the ferrite net.
For high carbon steel workpiece, spheroidizing annealing is usually used before quenching to improve the microstructure.
For high chromium and high speed steel, the carbide segregation which is above grade 5 should be classified as one kind before quenching, and the quenching temperature should be reduced to avoid quenching crack.
Contact person: Hailee Ma
Phone: 0086-18932783253(whatsapp, wechat)
Specialist of induction billet heater is glad to be your partner in the field of induction heating.
Post time: 07-05-2018