Well, we have found ourselves in similar situations. We would write an NCR up listing all the applicable joints where the 8018-B2 was used instead of 7018. After that, we would run a PQR for the use of 8018-B2. Basically since the "A" number is an essential variable, requalification is required.

Assuming the 8018-B2 PQR passed; we would clear the NCR based on the acceptable results (ie - accept the joints as welded).

In some situations you would be required to get the approval of an AI or your client's engineering representative for this practice.

In my experience, this mistake does not warrant cutting the joints apart and rewelding.

Charles