Straightness is an important indicator of the quality of HFW (high frequency welding) steel pipes. The higher the straightness, the easier it is to ensure the thread quality of the oil well pipe. It also provides convenience for subsequent processing and inspection. There are several reasons why the straightness of HFW steel pipes is exceeded during production:
1. Improper adjustment of the straightening frame 1) Bending phenomenon HFW steel pipe is bent out of the sizing unit and is bent in one direction.
2) Remedial measures In HFW straightening, the Turkish head is used to adjust straightness. The correct adjustment of the deflection of the reverse bending of the Turkish head is the key to control the bending of the HFW steel pipe. For bending caused by misalignment of the straightening frame, the operator should keep the Turkish head frame adjacent to the flying saw stationary, and adjust the other Turkish head in an opposite direction according to the bending direction.
2. Inconsistent strength of the coil plate 1) Bending phenomenon The bending phenomenon of the steel pipe is more serious, and the bending direction of the steel pipe is not one direction.
2) Resolving measures The bending caused by uneven strength of the coil must be solved by the coil manufacturer by increasing its rolling level. The difference in strength between the coils should be controlled within 30 MPa.
3. Uneven temperature on the upper and lower surfaces of the steel pipe 1) Bending phenomenon The steel pipe is straight after cutting in production, but it bends when cooling on the finishing bench, and the overall bending direction of the steel pipe is the same.
2) Resolve measures Change the water cooling device so that the amount of cooling water on the upper surface can be controlled to maintain the same temperature on the upper and lower surface of the steel pipe; for large diameter steel pipes, when the amount of water cooled cooling water is maximized and the temperature on the upper surface is still higher than the lower surface, appropriate Reducing the speed of the production line, or installing a cooling water tower to accelerate the cooling of the cooling liquid; using the reverse adjustment method, that is, according to the direction and degree of bending of the steel pipe on the finishing bench, reverse adjustment is performed during the sizing and straightening.
4. Insufficient sizing: 1) Bending phenomenon Before the hydrostatic test, the steel pipe is straight, but after the hydrostatic test, the bending phenomenon occurs and the bending direction is fixed.
2) Solution measures By appropriately increasing the sizing volume and reducing the excessive residual stress of the HFW steel pipe, the occurrence of the bending phenomenon can be avoided. If the sizing amount is increased, the bending phenomenon is still not eliminated, and further adjustment of the shaping hole type is required. An additional amount of deformation is added to the sheet to compensate for the rebound after deformation, to reduce the residual stress, and ultimately to solve the problem of bending of such steel tubes.
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