Four Factors Affecting The Straightness Of Carbon Steel Square Tube

Straightness is an important indicator to measure the quality of a 3x3 steel square tube. There are four factors that affect straightness in production:

(1) Uneven strength of coil plate

The bending phenomenon of square and rectangular tubes is serious, and the bending direction is not in one direction. The solution is that the bending caused by uneven coil strength must be solved by the coil manufacturer by improving its rolling level. The strength difference between various parts of the rolled plate should be controlled within 30MPa.

(2) Insufficient sizing

The rectangular tube was straight before the hydrostatic test, but it bent after the hydrostatic test, and the bending direction was fixed. At this time, it is necessary to appropriately increase the sizing amount to reduce the excessive residual stress of the pipe and avoid the bending phenomenon. If the bending phenomenon is not eliminated after increasing the sizing amount, it is necessary to further adjust the molding pass pattern to give the plate An additional amount of deformation is added to compensate for the rebound after deformation, reduce residual stress, and ultimately solve the bending problem of this type of square and rectangular tube.

(3) Improper adjustment of the straightening frame

The square and rectangular pipes are bent after coming out of the sizing unit and are fixed in one direction. During pipe straightening, a Turkish head is used to adjust the straightness. Correctly adjusting the deflection of the Turkish head in reverse bending is the key to controlling the bending of 3 square tube steel. For bends caused by improper adjustment of the straightening frame, the operator should keep the Turkish head frame adjacent to the flying saw fixed, and make appropriate adjustments to the other Turkish head in the opposite direction according to the bending direction.

(4) Uneven temperatures on the upper and lower surfaces of the steel pipe

In production, the square rectangular tube is straight after being cut, but it bends when cooling on the finishing bench, and the overall bending direction of the tube is the same. To solve this problem, it is necessary to modify the water-cooling device to control the amount of cooling water on the upper surface and keep the temperature of the upper and lower surfaces of the pipe the same; for large-diameter pipes, when the amount of water-cooling cooling water is turned to the maximum, the upper surface temperature is still higher than that of the lower surface. Reduce the production line speed, or install a coolant water tower to speed up the cooling of the coolant; use the reverse adjustment method, that is, according to the direction and degree of bending of the rectangular tube above the finishing bench, reverse adjustment is made during sizing and straightening.