Common Welding Defects in Arc Welding and Systematic Prevention Methods

First, regarding undercut defects, the main manifestation is the excessive melting of the base metal at the weld edge, forming a groove-like depression. This type of defect is usually caused by excessive welding current, excessively long arc, or improper electrode manipulation. When the current is too high, the arc heat input is concentrated, leading to severe melting of the base metal edge, while the molten pool fails to fill in time, thus forming undercut. Furthermore, excessively fast electrode movement or improper angle control can also lead to uneven molten pool distribution. To address this issue, welding parameters should be optimized to control heat input, a reasonable current range should be selected, and the dwell time at the bevel edge should be appropriately extended to ensure sufficient molten pool filling. Simultaneously, the arc length should be controlled to avoid heat dispersion and unstable combustion due to an excessively long arc. Controlling undercut is particularly crucial in contact welding or precision conductive connection processes to avoid localized stress concentration.

Second, weld beads are another common defect, typically manifesting as localized metal accumulation or sagging on the weld surface. This phenomenon is often caused by excessive welding current, excessively slow welding speed, or excessive assembly gaps. Especially in vertical or overhead welding positions, the molten pool is more prone to uncontrolled flow due to gravity. Different control strategies should be adopted for different welding positions. For example, in overhead welding, the current can be appropriately reduced by about 15% to 20%, and the molten pool flow can be controlled by a "faster in the middle, slower on the sides" welding technique. During vertical welding, the molten pool temperature should be strictly controlled, and cooling should be achieved by interrupting or lifting the arc when necessary. Furthermore, properly controlling the bevel gap is also an important means of preventing weld beads. In processes involving Brazing Silver Contacts to Copper Bars or Silver to Copper Brazing, the stability of the molten pool directly affects the uniformity of the joint interface.

Slag inclusions mainly manifest as unmelted slag or oxides embedded within the weld, which can severely affect the weld's density and mechanical properties. Common causes include insufficient welding current, excessive welding speed, and failure to promptly remove slag during multi-layer welding. Insufficient current leads to insufficient molten pool temperature, preventing slag from fully floating to the surface; conversely, excessive welding speed causes slag to become trapped in the weld before it can be expelled. To address this, welding parameters should be adjusted appropriately to ensure sufficient heat input, and interpass cleaning procedures should be strictly followed during multi-pass welding. Furthermore, appropriately increasing the bevel angle helps improve molten pool flow conditions and promotes slag flotation. In the manufacturing process of Brazed Contacts or Brazed Electric Contacts, internal inclusions significantly reduce conductivity and therefore require close control.

Cracks are one of the most detrimental welding defects, often closely related to welding stress, material composition, and cooling rate. Common causes include excessively rapid arc termination, thermal stress concentration due to high-current welding, and high levels of harmful elements in the material. During welding, the molten pool metal solidifies and shrinks; if stress cannot be released, cracks will form. To effectively prevent cracks, both process and material aspects should be addressed. On the one hand, preheating the workpiece reduces the cooling rate and temperature gradient, thereby lowering thermal stress. On the other hand, using alkaline welding electrodes helps reduce the impact of harmful elements such as sulfur and phosphorus on weld performance. Furthermore, the weld shape should be optimized to avoid deep, narrow weld structures, thus reducing stress concentration. In high-reliability joining applications, such as Copper Bars Silver Contact Joining or Joining Silver Contacts with Copper Bars through Brazing, crack control is a core aspect of quality management.