Selection of welding rods for common steel materials

The weldability of carbon steel is closely related to the carbon content in the steel. The higher the carbon content, the worse the weldability of the steel. The carbon content of carbon steel used for welding does not exceed 0.9%. Almost all welding methods can be used for welding carbon steel structures, among which manual arc welding, submerged arc welding and CO2 gas shielded welding are the most widely used.

The weld strength of carbon steel electrodes is usually less than 540MPa (55kgf/mm2). At present, a large number of electrodes below 490MPa are used in welding.

Acid electrodes can be used for general welding structures, and alkaline electrodes can be used when bearing dynamic loads or complex thick-walled structures and low-temperature use.

When welding medium carbon steel (C=0.25%~0.60%) and high carbon steel (C＞0.60%), alkaline low-hydrogen electrodes with low impurity content and certain desulfurization ability should be used. In some cases, ilmenite or calcium-titanium electrodes can also be used, but strict process measures must be taken.

For medium carbon steel welding, due to the high carbon content of steel, the tendency of welding cracks increases. Low hydrogen type welding rods or welding rods with high plasticity and toughness of weld metal can be selected, and preheating and slow cooling treatment are required in most cases. For high carbon steel welding, strict preheating and post-heating measures must be taken to prevent welding cracks.

It is difficult to make the weld and the parent material have exactly the same performance when welding high carbon steel. The tensile strength of high carbon steel is mostly above 675MPa (69kgf/mm2). The selection of welding materials should be determined according to the product design requirements.