Introduction to common welding methods for steel structures

(1) Manual arc welding
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To select the model of manual arc welding electrode, the electrode series should first be determined according to the principle of being compatible with the strength of the main metal, that is, the strength of the two should be equal. When steels of different strengths are connected, using a series of welding rods that are compatible with low-strength steels can meet the strength and other requirements and is more economical. Then select the specific model based on the grade of steel, the importance of the structure, the welding position and the process performance of the welding rod. For general structures, usually when the steel material is b, the use of type B can meet the requirements. The coatings of these two electrodes are titanium-calcium type, which is easy to master during welding. The slag has good fluidity and is easy to remove. The arc is stable, the penetration is moderate, the spatter is less, and the welding wave is neat. It is suitable for all-position welding. The power supply is AC or DC forward or reverse connected. For heavy-duty working crane beams, crane trusses or similar structures, usually when the steel is B, or or when the above three types of welding electrode coatings are used, they are all low-hydrogen types and are suitable for all-position welding. The welding power supply should be reverse-connected to DC. Low-hydrogen welding rods can reduce the hydrogen content in the weld to avoid cold cracks, so the weld metal has good toughness and its brittle transition temperature is close to that of killed steel.
(2) Automatic submerged arc welding
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Due to the concentration of arc heat, automatic submerged arc welding has large penetration depth, uniform weld quality, few internal defects, and good plasticity and impact toughness. , so it is better than manual welding. The quality of semi-automatic submerged arc welding is between automatic submerged arc welding and manual welding. In addition, automatic or semi-automatic submerged arc welding has fast welding speed, high production efficiency, low cost and good working conditions. However, their application is also limited by their own conditions. Since the welding machine must move along the guide rail along the weld seam, certain operating conditions are required. Therefore, automatic or semi-automatic submerged arc welding is particularly suitable for mass assembly and welding of beams, columns, plates, etc.
(3)

Gas shielded welding

Gas shielded welding uses a spray gun to eject gas as an arc Protective medium to isolate the molten metal from the air to keep the welding process stable. Since there is no slag produced by the flux during welding, it is easy to observe the forming process of the weld. However, the operation must be done in an indoor shelter from the wind, and a windproof shed must be erected at the construction site.
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