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Brief Introduction To Welding Methods Of Steel Structure
May 01, 2018

(1) manual arc welding.

To choose the type of manual arc welding electrode, the welding rod series should be determined firstly according to the principle of the main metal strength, that is, the strength should be equal. When different strength of steel connection, adopt the welding rod series with low strength steel, can meet the requirements of the strength and so on and the economy. Then combine the steel plate number, the importance of the structure, the welding position and welding rod process performance and so on select the specific model. For general structure, usually when steel is Q235A•F, E4303. You can meet the requirements. The two electrode coated titanium calcium type, welding is easy to master, its good slag flow, easy to take off the slag, and the arc stability, penetration is moderate, less spatter and weld neat, apply all position welding, welding power source is ac or dc positive and reverse connection. For heavy duty crane beams, crane trusses or similar structures, E4315 or E4316 are commonly used when steel is Q235B, Q235C or Q235D. All of the above three types of welding rods are of low hydrogen type, suitable for all position welding, and welding power supply is suitable for dc reverse connection. The low hydrogen electrode can reduce the hydrogen content in the welding seam, so as to avoid the cold crack, so the weld metal's toughness is good, and its brittle transition temperature is close to the calm steel.

(2) automatic submerged arc welding.

Automatic submerged arc welding is better than manual welding due to the concentration of arc heat, so it is good to weld depth, uniform quality, less internal defects, plasticity and impact toughness. 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 speed, high production efficiency, low cost, good working conditions. However, their application is also limited by their own conditions, because the welder has to move along the guide rail of the welds, so there must be certain operating conditions. Therefore, automatic or semi-automatic submerged arc welding is especially suitable for assembling and producing welding seams of beams, columns and plates.

The welding wire and flux used in automatic or semi-automatic submerged arc welding shall be compatible with the main metal strength, that is, the strength of the deposited metal shall be the same as that of the main metal. Wire shall conform to the national standard "welding wire" (GB/T1300), flux, according to the need to press "carbon steel submerged arc welding with flux" (GB/T5293) and the low alloy steel submerged arc welding flux (GB/T12470) accordingly. In general, Q235 steel adopts H08 (welding 08) or H08A (welding 08 high) welding wire with manganese type HJ401 flux; 16Mn steel adopts H08A or H08MnA (welding 08. Manganese high) welding wire with high manganese type HJ402 flux; 15MnV steel USES H08MnA or H10Mn2 (welding 10 mn 2) welding wire with HJ402 flux.

(3) CO2 gas shielded welding.

CO2 gas shielded welding is a protective medium that emits CO2 gas from the spray gun as an arc, which insulates the molten metal from the air to keep the welding process stable. It is easy to observe the forming process of the welds because there is no slag generated by the flux during welding. However, in the operation, the wind shelter should be installed on the construction site.

Gas shielded welding arc heating concentration, fast welding speed and deep penetration, so the strength of the weld is higher than the manual welding, and the plastic and anti-corrosion are good, suitable for thick steel plate or extra thick steel plate (t>100mm) welding.

The welding wire used in CO2 gas shielded welding is high manganese type, i.e., Q235 steel adopts H08Mn2Si (welding 08 mn 2 silicon); 16Mn steel and 15MnV steel are H08Mn2Si or H10Mn2 (welding 10mn 2).