What Are the Factors That Cause Porosity During Steel Pipe Welding?

Understanding of steel and pipe

Steel pipe is a very important building material in our daily life. They are used in various fields such as fluid and powder solid transportation, heat exchange, machinery parts and containers manufacturing, building structure framework, support and mechanical brackets, and even in furniture making. Steel pipes are popular for their unique product features and aesthetics. They are economical steel materials with various specifications and performance requirements.

Steel pipe can be used for fluid and powder solid transportation, heat exchange, machinery parts and container manufacturing. Building structure framework, support and mechanical bracket can be made by the steel pipe wholesale which can reduce weight, save 20%-40% of metal and achieve factory-based mechanical construction. Using the steel and pipe in the construction of highways and bridges can not only save steel materials and simplify the construction, but also greatly reduce the area of painted protective layers, saving investment and maintenance costs.

Factors that Produce Pores in Welded steel and pipe

Many factors can affect the formation of pores when welding the steel and pipe, such as the variety and content of alloy in welding rods and welding pieces, seasons and on-site conditions, acidity and alkalinity of the coating on the welding rods, cleanliness of the welding materials, baking and drying temperature of the welding rods, preheating temperature, cooling rate of the welded pieces and welds, welding method and proficiency, presence or absence of arc starter and stopper, weld energy, spatial position of the welds, and even the thickness and humidity of the wave welding.

  • If there is oil, water, rust or other organic matter on the welded piece and it is not completely removed, pores can develop during welding.

  • If the electrode is not dry or not heated enough or not heated for sufficient time, pores may occur.

  • When frost or heavy fog occurs in the morning, dry electrodes are more likely to absorb moisture and produce pores.

  • If the cleaning width of the welded seam of the steel and pipe is too narrow or incomplete, the high temperature of the welding arc may cause organic matter such as paint around the welded seam to burn, releasing steam or decomposing hydrocarbons, which will seep into the poorly protected molten pool, resulting in hydrogen and carbon monoxide pores.

  • Excessive welding current may burn off a large amount of silicon (silicon is a good deoxidizer) alloy elements. The deoxidation reaction in the molten pool can only be completed by carbon elements. Carbon oxide becomes carbon monoxide, which may result in carbon monoxide pores.

  • The large size of the molten pool during welding allows air to seep in, resulting in nitrogen pores. Horizontal welding is more prone to pores than vertical welding.

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