There are many factors that affect the generation of pores when welding steel pipes (such as
LSAW straight seam pipes), such as the type and content of alloy components of electrodes and weldments, the season and job site conditions, the pH of electrode coatings, the cleanliness of weldments, and the baking of electrodes, the drying temperature of the electrode, the preheating temperature of the weldment and the cooling speed of the weld, the welding method and proficiency, the arc starting method with or without the arc starting plate and the arc receiving plate, the energy of the welding line, and the spatial position of the weld , even the thickness of the solder wave, the humidity of the air and other factors play an important role in the generation of pores, which are initially summarized 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 the 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 (silicon is a good deoxidizer). The deoxidation reaction in the molten pool can only be completed by carbon elements. Oxidation of carbon to carbon monoxide, 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.
Go here to learn more about " The Significance of Studying the Heat-Affected Zone of Welded Pipe Welding"
