Main quality defects of seamless steel pipe heat treatment
1 seamless performance and organizational issues
Performance and organizational issues, depending on the material composition and the original state and the level of rationality and control of heat treatment process, which is the core content of heat treatment quality control.
Heat treatment process for the formulation or implementation of good, seamless performance (such as yield, tensile, elongation) will exceed the requirements of the standard; Wei appears to the organization structure, Ribbon and other standards organizations are not allowed.
2 seamless steel pipe dimension problem
Mainly in the length direction (axial) bending and cross direction (radial) ovality and diameter of the variance.
2.1 reasons for bending of seamless steel tubes
2.1.1 seamless steel tube heating is not bend
Seamless steel tube heating unevenly along the axial direction of seamless steel pipe in different organizational changes at different times on quenching, seamless steel tube volume change at different times, bend.
2.1.2 bent seamless steel tube quenching
Hardening is a high strength seamless steel casing and the preferred treatment for high grade seamless line pipe production. Organizational change very quickly on quenching, seamless organizational change volume change. Because of the seamless steel pipe sections which lead to organizational change not cooling rate is not consistent, and also have a bent.
2.1.3 billets made crooked
Seamless chemical segregation exists, even if the cooling conditions are fully consistent, and cooling will bend.
2.1.4 uneven cooling bending
Alloy seamless steel pipes after heat treatment, usually to seamless steel tube side of the Rotary side to cool naturally. Seamless steel tubes for the axial and circumferential cooling rate is not uniform, bending. Seamless steel pipe bending does not meet requirements will affect subsequent processing (such as transport, straightening, etc), can even influence its performance.
2.1.5 on sizing machine bending
Alloy, especially a narrow range of tolerance for the outside diameter of the steel seamless pipe (such as line pipe, casing) General requirements after tempering and sizing. If the sizing machine center line is inconsistent, seamless steel pipe bending.
2.2 seamless steel tube outer diameter of the ellipse and the main reasons for variance
Quenching due to seamless steel tube parts organizations shift is inconsistent, seamless steel pipe ovality; due to the ellipticity, so most of the seamless steel tube required after quenching and tempering and sizing, sizing control technology is bad, outside diameter variances may occur.
3 bugs and cosmetic issues
3.1 seamless steel tube quenching crack
Seamless steel tube quenching temperature is too high, or takes too long to heat or temperature quench cracks caused by uneven heating. Chemical composition segregation of seamless steel tubes, seamless inclusion is also easily crack.
3.2 seamless steel tube overheating or burning
Seamless steel tube quenching of high temperature or heating time is too long, could easily lead to overheating or burning, severe, seamless steel pipe will collapse.
3.3 surface decarburization or serious oxidation of seamless steel tubes
Seamless steel tubes in the heating, surface severe oxidation of carbon or serious, as a result of heating temperature and time control or air-fuel ratio adjustment disorder.