How to conduct metallographic inspection after quenching in induction heating furnace?
Metallographic examination of pearlite ductile iron parts after induction heating furnace quenching shall be carried out in accordance with JB/T 9205-2008 “Induction heating furnace quenching metallographic examination of pearlite ductile iron parts”
1) After the pearlitic ductile iron castings are quenched in high- and intermediate-frequency induction heating furnaces and low-temperature tempering (W200T), metallographic samples shall be taken in the middle of the induction quenching zone or at the location specified by the technical conditions.
2) After grinding, the metallographic sample is etched with an alcohol solution containing 2% to 5% nitric acid by volume until a clear hardened layer is displayed.
3) According to the microstructure classification instructions shown in Table 6.2 and the microstructure classification chart in JB/T 9205-2008, perform the metallographic evaluation. Among them, grades 3 to 6 are qualified; when there are special requirements, they shall be implemented in accordance with the relevant technical documents.
Table 6-2 Description of microstructure classification of pearlite ductile iron castings after quenching in induction heating furnace
|1||Coarse martensite, large retained austenite, ledeburite, spheroidal graphite|
|2||Coarse martensite, large retained austenite, spheroidal graphite|
|3||Martensite, massive retained austenite, spherical graphite|
|4||Martensite, a small amount of retained austenite, spheroidal graphite|
|5||Fine martensite, spherical graphite|
|6||Fine martensite, a small amount of undissolved ferrite, spheroidal graphite|
|7||Fine martensite, a small amount of undissolved pearlite, undissolved ferrite, spherical graphite|
|8||Fine martensite, a large amount of undissolved pearlite, undissolved ferrite, spherical graphite|