Color penetrant inspection of welds is one of the effective methods to inspect the surface defects of welded joints. It can effectively and quickly check for defects in the welding of erw steel pipes.Compared with magnetic particle inspection of welds, it has the advantage that it is not limited to ferromagnetic materials, and its application range can be extended to non-magnetic materials such as austenitic stainless steel and alloys.

Seamless line pipes are mainly used to transport high-pressure oil and gas near the wellhead. With the deepening of oil and natural gas exploitation, there are more and more oil and gas wells with complex exploitation conditions and in sulfur-containing environments, and the problem of hydrogen sulfide corrosion is becoming more and more serious. The development of sulfur-resistant seamless line pipes is imminent. The addition of Cu and Ni can improve the HIC performance of the seamless line pipe material, reduce the S content in the steel, and reduce the sensitivity of hydrogen bubbling by spraying silicon calcium powder.

Rectangular tube, also known as square tube or rectangular tube, is a kind of square steel with a hollow section. At present, there are two main forming processes for square tubes, which are the round-to-square and the direct-to-square.

Eddy current testing and magnetic flux leakage testing are both commonly used non-destructive testing methods for seamless steel pipes. The two mainly detect the surface and near-surface defects of steel pipes. Both have their own focus and limitations. Choose according to the situation.

Nitriding treatment refers to the chemical heat treatment process in which nitrogen atoms infiltrate the surface of the steel pipe in a certain medium at a certain temperature. The common ones include liquid nitriding, gas nitriding, and ion nitriding. The purpose is to improve the surface hardness and wear resistance of the steel pipe. Improve fatigue strength, corrosion resistance, etc.

The magnetism of the seamless tube is due to the magnetism of martensite or ferrite, and a small amount of martensite or ferrite will be formed during component segregation or improper heat treatment during movement. In this way, there will be weak magnetism in the seamless tube. At this time, it is necessary to demagnetize the seamless steel pipe.