GB/T 10561:2005

This standard specifies micro evaluation methods for evaluating non-metallic inclusions of rolled or forged steel products whose compression ratio is larger than or equal to 3 with standard diagrams. The method is comprehensively used for evaluation of the flexibility of purpose steel. However, owing to the impact of testing personnel, the test results are difficult to reappear even if adopting lots of samples. Therefore, great discretion is required while using this method.
Note: these standard diagrams mayn't be applicable to evaluate certain types of steels (like free-cutting steel).
This standard also provides graphical analysis methods for determining nonmetallic inclusions (see annex D).