Causes Of Porosity In Steel Pipe Welding

Changsha China
Categories: Manufacturing Engineering / China Tags:
seamless pipes
welded tubes

There are many factors that affect the generation of pores during welding of seamless pipes and welded tubes. Such as the type and content of the alloy composition of the electrode and the weldment, the pH of the electrode coating, the cleanliness of the weldment, the season and the job site conditions. The drying temperature of the welding rod, the preheating temperature of the weldment and the cooling rate of the weld seam, the welding technique and proficiency. Whether there is an arc-starting plate and an arc-receiving plate, the energy of the welding line, the spatial position of the weld, and even the thickness of the welding wave, the humidity of the air and other factors play an important role in the generation of pores. The preliminary summary is as follows:

(1) If there is oil, water, rust or other organic matter on the weldment and it is not completely removed, pores will occur during welding.

(2) If the electrode is not dried or the drying temperature is not enough or the constant temperature time is not enough, pores may appear.

(3) If the frost or fog is heavy in the morning, the dry electrode is most likely to absorb moisture, and pores will appear.

(4) The width of weld seam cleaning is too narrow or not thorough. The high temperature of the welding arc may cause organic matter such as paint around the weld to burn, release water vapor or decompose hydrocarbons, and immerse into a poorly protected molten pool, which may cause hydrogen and carbon monoxide pores.

(5) Excessive welding current will burn out a large amount of alloying element silicon. The deoxidation reaction in the molten pool can only be completed by carbon elements. (Silicon is a good deoxidizer) Carbon and oxygen generate carbon monoxide, and carbon monoxide pores may appear.

(6) The molten pool is too large during welding, and air is immersed in the molten pool, which is prone to nitrogen holes. Horizontal welding is more prone to porosity than vertical welding.