The causes of longitudinal cracking of welded pipes are in various fields, including the elements of raw materials and the elements of manufacturing process. If the plastic deformation of the welded pipe itself is poor or the heat treatment is poor, the probability of longitudinal cracking will increase, but the fundamental reason is that the welded pipe after cold drawing has a high residual stress field.

From the concept of cracking theory and mechanics, the cracking of prefabricated components is the result of the transformation and propagation of internal micro-cracks. The longitudinal crack of the welded pipe is basically attributed to ductile cracking, and the crack appearance is an open type.

In general, the existence of large, medium and small cracks in metal composite materials is unavoidable, but in the case of the same raw material specifications, whether cracking will be caused depends on the tensile stress size of the expected effect on the prefabricated components. The expected effect of the tensile stress on the prefabricated member can thus be over-loaded, and it can also therefore exist in its own residual stress field.

There is a high residual stress field after cold drawing of welded pipe, especially after emptying. According to the above basic principles of tensile cracking, it can be seen that the axial residual stress field existing near the outer surface of the welded pipe has a particularly important expected effect on the longitudinal cracking of the welded pipe.

Tips: if the welded pipe is required to have a high degree of cleanliness, it should be cleaned with ultrasonic waves.

1) The basic concept of ultrasonic cleaning: The huge change in the sound intensity level of the ultrasonic wave of the welded pipe when it is dispersed in the liquid causes the liquid to cause a significant vapor situation, resulting in millions of tiny cavitation bubbles every second. Under the rapid and many causes, and the continuous obvious blasting project, resulting in strong impact and negative working pressure adsorption, enough to quickly get rid of the hard-to-eliminate dirt.

2) If the welded pipe is relatively long and there is a stainless steel water tank, you can buy an ultrasonic vibration plate and allocate the funds to the water for ultrasonic cleaning. If it is not too long, you can use an ultrasonic vibration rod, insert it into the pipeline for cleaning, and then clean it with running water. Ultrasound to get rid of waste.