Causes of crater cracks and preventive measures

I. Causes of arc pits The formation of arc pits is mainly related to the following factors: 1. An excessively short arc extinction time at the end of welding. When welding is completed and the power supply is suddenly cut off, the welding electrode quickly moves away from the molten pool, preventing the metal in the center of the pool from filling the gaps at the end of the weld, thus forming a crater. 2. The welding current is too high or too low. If the welding current is too high, it will cause the molten pool to become too deep; as welding comes to an end, the metal slides downward, resulting in a crater. If the welding current is too low, the molten pool will be too shallow, resulting in insufficient metal at the end of welding and also causing arc pits. 3. The welding speed is too fast or too slow. If the welding speed is too fast, the molten pool becomes too small, resulting in insufficient metal at the end of welding and the formation of a crater. If the welding speed is too slow, the molten pool will become too large; as welding comes to an end, the metal will slide downward, which can also result in arc pits. 4. Improper welding method. If, at the end of welding, the electrode is not held in place for a short period or moved in circular motions several times, but is instead lifted or dragged away immediately, the metal at the end of the weld area will not be filled, resulting in a crater. If the angle or direction of the welding rod is not appropriate at the end of welding, it will cause uneven metal flow at that area, leading to the formation of crater defects.

II. Methods for preventing and controlling arc pits. In light of the causes of arc pit formation, the following preventive measures can be taken: 1) Select an appropriate welding current and welding speed. Depending on the thickness of the welding material, the welding position, and the welding method, select an appropriate welding current and welding speed so that the size and shape of the molten pool are suitable for completing the weld. 2) Use the correct arc-closing method. At the end of welding, the electrode should be held in place for a short period or moved in circular motions several times; the arc should not be stopped suddenly, so as to ensure sufficient metal is poured into the weld pool. At the same time, the angle and direction of the welding rod should be adjusted to ensure uniform metal flow at the end, thereby preventing the formation of arc pits. 3) Use an arc-stopping current or an arc-stopping plate. For welding machines equipped with an arc-closing current setting, this current (60% less than the welding current) can be used to remain in the crater for a certain period of time, allowing the wire to fill the crater and prevent crater defects from forming. For welding machines that do not have an arc-closing current setting, an ignition plate can be placed on the base material to guide the arc out of the weld area, thereby preventing arc pits from remaining on the weld. 4) Repair the resulting arc pits. If crater defects are found on the weld, they should be promptly removed by using an electric grinder or other tools, in order to eliminate the craters and any defects in their surrounding area. The area can then be refilled with welding rod to ensure the weld’s integrity and smoothness.