8D applies to repetitive or major quality issues:

D1 Form a team → D2 Describe the problem (batch, quantity, phenomenon, photos) → D3 Interim measures (segregation, screening) → D4 Root cause analysis (5Why, fishbone diagram) → D5 Permanent measures → D6 Verification → D7 Prevent recurrence (update standards/training) → D8 Summarize and recognize.

Common root causes in the steel industry: incoming materials, process parameters, equipment condition, inspection omissions.

For buyers: require suppliers to submit 8D reports and track the effectiveness of D5/D6 to avoid "paper-only rectification."