Phenomena that can reflect excessively low interpass temperature using indirect observation methods include difficulty in arc initiation, unstable arc, poor weld formation (such as lack of fusion or slag inclusions), and rapid cooling accompanied by a hissing sound. While these phenomena cannot provide precise temperature measurement, they can serve as preliminary early warning signals on-site.
Indirect Phenomena and Their Causes (for Reference)
|
Phenomenon |
Possible Cause |
Explanation |
|
Difficulty in Ignition |
Low temperature makes it difficult to stably ignite the arc |
When the base metal temperature is low, local heat conduction is rapid, and the arc energy is quickly absorbed. |
|
Fluctuating Arc, Poor Stiffness |
Large temperature gradient around the molten pool, uneven magnetic field distribution |
Dispersed arc column, affecting penetration and weld formation. |
|
Incomplete Fusion, Slag Inclusion |
Insufficient preheating of the base metal, poor fusion between the deposited metal and the base metal interface |
Especially prone to occur in thick plates or multi-layer welding. |
|
Rapid Cooling of Weld, Hissing Sound |
High-temperature welds rapidly contract when encountering cold base metal, hydrogen cannot escape in time |
A high-risk signal for cold cracking and delayed cracking. |
|
Increased Spatter, Unstable Droplet Transition |
Low local temperature leads to decreased dynamic stability of the arc |
May be accompanied by damp flux coating, doubly deteriorating weld quality. |
|
Important Reminder |
The above phenomena are affected by many factors such as welding machine condition, operating techniques, and ambient humidity |
They can only be used as warnings and cannot replace actual measurements. In Wuhan during the current rainy season (humidity often exceeds 70%), moisture condensation may exacerbate the cooling effect, increasing the risk of misjudgment. |
Practical advice: Upon observing the above phenomena, immediately use an infrared thermometer to verify the temperature of the base material, ensuring it is ≥80℃ (100–150℃ recommended) to avoid cold cracking or delayed cracking caused by excessively low temperatures.
