What are the general corrosion problems of erw steel pipes?

Posted by zora li on November 18th, 2022

What are the general corrosion problems of erw pipe?

(1) Basic functions of steel outer coating
There are two aspects:
1. Protect the surface of ERW steel pipe from electrochemical corrosion and bacterial corrosion of the basic physical medium of soil,
2. Resistance to creep stress of soil medium movement, static stress of basic mechanical protection methods, wear strength and structure, etc.

(2) Sources of topcoat evaluation
It is pointed out in the literature: "The surface condition of the seamless steel pipe is called the environment where the pipe can be coated and insulated for 4 weeks. The soil conditions on the surface of the pipe are different for 4 weeks. Therefore, the anti-corrosion layer of the pipe is an important barrier to prevent soil erosion." This is the evaluation of the outer coating. The basic starting point for performance. The British company Jordon discusses pipe coating systems from two different perspectives: the European perspective is to make it resistant to moisture and corrosion, and it is the "barrier" perspective. From this point of view, it has a "PE" protection layer approach. The North American view is to enable it to prevent corrosion with anti-oxidative, anti-chemical and anti-negative release properties, which is the "glue" view. From this point of view, the "FBE" method protective layer is produced.

Common defects of ERW steel pipe welding

The ERW steel pipe is fed into the forming machine and deformed into a cylindrical tube through an induction loop or contact weld fillet. The magnetic field current around the induction coil is induced by the edge of the strip, which is heated due to its electrical resistance to generate thermal resistance, and the heated extruded strip The edge of the material forms a roll extrusion weld. No high frequency welding metal is added, it is actually forge welding. With good production control, no molten surface of molten metal or oxide remains. The HAZ is shaped like a drum because of the high frequency current entering the strip at the edge of the strip, generating heat from the end and side parts of the strip edge. The HAZ color is slightly darker than the base metal because the edge of the welded carbon steel strip is heated to diffuse and the cooled weld carbon is absorbed by the edge of the strip.

Common defects of erw steel pipe welding
High-frequency tubes may have various welding defects. Each defect has many different names, and there is no accepted terminology. Defect names given below, another common name for defects in parentheses: ① Inclusions (burnt black oxide); ② Pre-arc (white burnt oxide); ③ Lack of fusion (grooving); ④ Edge unfused (wavy edge); ⑤ insufficient center fusion (cold welding center); ⑥ stick welding (cold welding); ⑦ cast welding (welding brittleness); ⑧ blow hole (pinhole); ⑨ skip welding. These defects are not only the most common high frequency welding defects.

Read more : seamless carbon steel pipe