GB/T 13320-2007 in English

《GB/T 13320-2007钢质模锻件 金相组织评级图及评定方法》由TC74（全国锻压标准化技术委员会）归口，主管部门为中国机械工业联合会。
本标准规定了钢制模锻件的金相组织评级图及评级方法。

1 Scope

This standard specifies metallographic grading atlas (hereafter referred to as simply grading atlas) and assessing method for steel die forgings.
This standard is applicable to structural steel die forgings which have been subjected to treatments of quenching and tempering, normalization, isothermal normalization, control cooling after forging.
This standard is not applicable to assessment for structures of decarburization, overheating, overburning, etc. of forgings.

2 Terminologies and Definitions

For the purposes of this standard, the following terminologies and definitions apply.
2.1
Isothermal normalization
Heat treatment process with the following procedures: heat forgings to a certain temperature higher than Ac3 (or Ac1), keep for a certain period, control cooling to a certain temperature in phase change zone of pearlite and keep for a certain period to make austenite transform to pearlite type structure, then cool in the air.

Foreword i
1 Scope
2 Terminologies and Definitions
3 Grouping and Grading of Grading Atlas
4 Application of Grading Atlas
5 Selection and Preparation of Test Piece
6 Assessment of Metallographic Structure
Appendix A (Informative) Examples of Metallographic Grading Atlas for Forgings