Key points of heat input control in welding process

Welding heat input is a key factor affecting joint quality, calculated using the formula Q = UI/v (where Q is heat input, U is voltage, I is current, and v is welding speed). Properly controlling heat input can prevent problems such as overheating or incomplete penetration.

In practice, different welding methods have different heat input requirements:

SMAW (Shielded Metal Arc Welding): Suitable for pipe butt joints, requiring matching electrode diameter and current parameters to ensure full fusion of the weld pool.

GMAW (Gas Metal Arc Welding): Utilizing a mixed gas shield, heat input is relatively concentrated, suitable for plate butt joints for filling and covering, reducing deformation in the heat-affected zone.

Improper heat input can easily lead to defects: excessively high heat input results in coarse grains in the base metal, reducing weld toughness; insufficient heat input causes incomplete fusion or slag inclusions. For example, in stainless steel welding, a low current process can reduce the sensitized zone of the heat-affected zone, effectively preventing intergranular corrosion.