Heat Treatment Defect And Its Prevention
Microstructure and properties of seamless steel pipe failed: after seamless austenitic, according to their different carbon contents and different cooling speeds, can get Pearlite, Bainite, martensite organizations. Thermal expansion process if not properly controlled may produce widmanstatten structure. Widmanstatten is a heat organization. Seamless integrated can have adverse effects (excellent in high temperature lasting performance of the Organization), will increase seamless steel tube strength, brittle at room temperature. Lighter widmanstatten structure can use appropriate temperature normalized to eliminate, and degree of widmanstatten structure can be eliminated with secondary fire. High temperature for the first time, the second is low temperature. Also play a role in grain.
Transition curves of undercooled austenite (TTT) and continuous cooling transformation curves of undercooled austenite (CCT) is an important basis for development of cooling rate in heat treatment.
Seamless steel tube off size
Seamless steel pipes after heat treatment, in some cases, its size will change significantly and there are variances, including seamless steel pipe diameter, ovality and curvature changes. When the quenching process occurred. Often added after tempering and sizing process. Seamless steel pipe ovality changes usually occur in seamless steel tube end, mainly because of large-diameter thin-wall seamless tubes in heat for a long time, for seamless tubes "burn down" caused.
In General, the of seamless steel pipe bending can be corrected through a straightener. When the curvature is large, resulting in seamless steel tubes in the transport difficulties, on straightening seamless steel pipe will generate a great deal of straightening and stress. Severe drop
Seamless steel tube collapse resistance and corrosion resistance and so on. Moreover, seamless steel tubes in the cracking or breaking correction correction occurs in the straightening process.
Seamless steel tubes for surface crack
Seamless steel tube heat treatment process, excessive thermal stress will make the seamless steel tubes for surface cracks. Seamless steel tubes crack is mainly due to heating or cooling caused by too fast. High-alloy thick-walled seamless pipe heating, furnace temperature is too high, encounter faster in seamless steel tubes into the furnace heats up quickly, easy to produce large temperature stress, tend to crack. In order to reduce the seamless steel tubes crack of heat treatment, on the one hand depending on the steel grade developed heating system, choose the appropriate medium. Should as soon as possible, on the other hand the quenching of seamless steel tubes for tempered or annealed to remove residual stresses.