What are the factors that cause pores during steel pipe welding

There are many factors that affect the formation of porosity in steel pipe welding, for example, the type and content of the alloy composition of the electrode and the welding piece, the cleanliness of the electrode coating, the drying temperature of the electrode, the preheating temperature of the welding piece and the cooling speed of the welding seam, the skill and proficiency of the welding, the manner of welding and taming, whether there is the space location of the welding seam, even the thickness of the welding wave, the humidity of the air, etc. , the preliminary summary is as follows: 

(1) if the welding parts have oil, water, rust or other organic matter, and not thoroughly removed, welding will produce pores.

(2) the welding rod is not dried or the drying temperature is not enough or the constant temperature time is not enough, may appear the blowhole.

(3) if the morning frost or fog is heavier, the dry electrode is the most easy to absorb moisture, there will be pores.

(4) the weld cleaning width is too narrow or incomplete. 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, immerse in the poorly protected molten pool, and may cause hydrogen and carbon monoxide pores. 

(5) if welding current is too high, a lot of alloying element silicon will be burnt. The deoxidation reaction in the molten pool can only be done by carbon. (silicon is a good deoxidizer.) Carbon and oxygen produce carbon monoxide, which may form carbon monoxide pores. 

(6) when welding the molten pool is too big, the air immerses into the molten pool, and nitrogen holes are easy to appear. Blowhole is more likely to occur in horizontal welding than in vertical welding.