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.
GB/T 13320-2007 The following standards are cited：
