1. Uneven heating of steel pipe causes bending
The steel pipe is heated unevenly, the temperature along the axial direction of the pipe is different, the structure transformation time is different during quenching, and the volume change time of the steel pipe is different, resulting in bending.
2. Steel pipe bends due to quenching
Quenching is the preferred heat treatment method for the production of high-strength casing and high-grade line pipe. The structural transformation occurs very rapidly during quenching, and the structural transformation of the steel pipe brings about volume changes. Due to the inconsistent cooling rate of various parts of the steel pipe, the structural transformation rate is inconsistent, and bending will also occur.
3. The tube blank causes bending
If the chemical composition of the steel pipe is segregated, even if the cooling conditions are exactly the same, it will bend during cooling.
4. Uneven cooling causes bending
After heat treatment of alloy steel pipes, the steel pipes are usually cooled naturally while rotating. At this time, the axial and circumferential cooling rates of the steel pipe are uneven and bending will occur. If the curvature of the steel pipe cannot meet the requirements, it will affect subsequent processing (such as transportation, straightening, etc.) and even affect its performance.
5. Bending occurs on the sizing machine
Alloy steel pipes, especially steel pipes with narrow outer diameter tolerances (such as line pipes and casings) generally require sizing after tempering. If the center lines of the sizing racks are inconsistent, the steel pipe will bend.