Seamless steel tube hot-expanding process into the overall thermal expansion, thermal expansion of the surface treatment and chemical treatment. Seamless pipe thermal expansion thermal expansion of general use of the whole process. Are essential processes such as heating, insulation, cooling, these are likely to have defects in the process.
Seamless steel pipe heat treatment defects include unqualified, size steel microstructure and properties over cracks, scratches, and surface severe oxidation, decarburization, heating, burning, etc.
Thermal expansion process for seamless steel tube features:
First process is heating up: Ac1 and Ac3 is a critical point of heat; the other is Ac1 and Ac3 above the critical point of the heating. First major is the stabilisation of seamless steel pipe, and elimination of residual stress of seamless steel tubes, the second is mainly of austenitic steel.
The next step is thermal insulation: the aim is to even heating temperature of the seamless steel tubes to get reasonable heat organization.
Third step is cooling: cooling is a key process of seamless steel pipe heat treatment, he decided to microstructure and mechanical property of seamless steel tubes in cooling. Used in the actual production of a variety of seamless steel pipe cooling. Often used cooling methods of furnace cooling or air cooling, water cooling, oil cooling, polymer.
Depending on the heating temperature of seamless steel tubes, seamless steel tubes for different cooling speeds, into normalizing, annealing, tempering, quenching and other processes.
Normalizing: refining austenite grain, uniform internal organization and the residual stress and improve the performance of seamless steel tubes. Reduce seamless steel tube in deformation process in the by formed of band organization and mixed crystal (but cannot elimination for steel in the of partial analysis and inclusion real, caused of band organization); elimination had eutectoid steel in the of mesh carbide real, conducive to ball of annealing; as carbon steel and the alloy structure seamless steel tube quenching Qian of pretreatment, to refinement grain makes organization uniform, reduced quenching process by produced of seamless steel tube defects; for low carbon steel and low alloy steel seamless steel tube to alternative annealing, improved seamless steel tube of cutting performance ; Or as a requirement of final heat treatment of ordinary seamless steel tubes.