Reason why more than 2 repairs are not allowed for the same weld

Consider the issue of the heat-affected zone. Multiple welding passes cause the surrounding area to be continuously heated and cooled. It destroys the metallographic structure and grain structure.

According to the explanation in 4709, it is a problem related to the welder’s skill level and inadequate quality control measures; it has no impact on the properties of the material

This is a specific requirement of our country’s standards. The main reason for the phenomenon of multiple repairs being carried out on the same weld area in our country is the lax enforcement of welding procedures. There were concerns in the past that repeated repairs to the same weld area could lead to grain growth due to repeated heating, thereby affecting the safe operation of the container. However, numerous tests have shown that there is no significant tendency for grain growth as a result of multiple repairs, and such growth does not pose a threat to the safe operation of the container. Therefore, it is unfounded to declare a weld defective when the number of repairs to the same weld area exceeds 2 times. For these reasons, the standard in our country does not impose a mandatory limit on the number of repairs to the same weld area; instead, it uses the phrase “should not exceed 2 times”

It is better to ensure that the weld is qualified in one attempt; for example, with austenitic stainless steel welds, multiple repairs result in multiple heating cycles, which causes the weld fusion zone and heat-affected zone to undergo repeated \"sensitization\", leading to a decrease in corrosion resistance.

Multiple repairs to the weld do not have a significant impact on the properties of the base material, and they do not pose a threat to the safe operation of the container. It’s just a set of management and control regulations

It should not exceed 2 times; this is mainly based on management considerations rather than technical ones, as new defects may arise during rework.

Weld repair is commonly referred to as \"rework\" in workshops. In actual production, when welding repairs are necessary, if the weld fails on the first attempt, a more skilled person must be brought in to carry out the rework. As mentioned above, doesn’t each round of rework and inspection cost money? If it still fails after two attempts, it indicates a problem with the welder or the welding process. I’ve encountered cases where repairs had to be done up to three times; reworking welds requires proper technical procedures to ensure success. It’s not a simple process of cutting open and then welding.

But after our factory’s product was repaired twice, there was a noticeable difference in color around the welds