Martempering only produces martensite. This again has to be tempered. The advantage of martempering to produce martensite is the avoidance of residual stress and quench cracks.
by cooling very fast(less than 1 second) up to a temperature just above martensite starting temperature and then holding at that temperature and slowly cooling
@@professorprotv there are many curves where you can read the hardness in each piont or temperature, btw in books of heat treatmts or physical metallurgy u cant find them
Hello Sir. Hope you are fine. I have a doubt in this lecture. At the time when temperature of the outside surface will be just above Ms, the temperature of inside will be quite higher (somewhere around nose or above nose). If the quenching of specimen is interrupted here and temp is kept constant, the curve of outside will definitely follow the non-transforming region, but the curve of inside will cross the transformation region and hence may transform into pearlite. Sir it's a request to clear this doubt because I am preparing for my exams.
It will completely convert to martensite if the final temperature is below Mf. If the final temperature is between Ms and Mf then some austenite will be retained.
Well, there is a transformation involved from austenite (CCP) to martensite (BCT). But the same crystal structure change is involved in normal quenching also. Thus from a crystal structure point of view, the extra time available in comparison to normal quenching gives nothing new.
Thank you for this explanation . The previous reading I have done did not explain the 1 second/550° gap as clearly.
sir, which is advantageous:(i) martemperting or (ii) tempering followed by quenching and why do we have both the techniques???
Martempering only produces martensite. This again has to be tempered. The advantage of martempering to produce martensite is the avoidance of residual stress and quench cracks.
Sir u are genius
Sir,Which one has higher hardness Tempered martensite or Martensite obtained from Martquenching or Martempering???
How can we interrupt the process within one second and shifting to another rate
by cooling very fast(less than 1 second) up to a temperature just above martensite starting temperature and then holding at that temperature and slowly cooling
By taking quenching liquid with temperature just a bit higher than martensite start temp.
@@shailendradeota6701 excellent idea man . which college are you from .I think u r mechanical 2-1
@@shailendradeota6701 studied long ago . currently no use,,😁
Sir what will be the effects on hardness on heat treated parts?
I guess we will be able to achieve 55-60HRC
@@professorprotv there are many curves where you can read the hardness in each piont or temperature, btw in books of heat treatmts or physical metallurgy u cant find them
Thanks
Hello Sir. Hope you are fine. I have a doubt in this lecture. At the time when temperature of the outside surface will be just above Ms, the temperature of inside will be quite higher (somewhere around nose or above nose). If the quenching of specimen is interrupted here and temp is kept constant, the curve of outside will definitely follow the non-transforming region, but the curve of inside will cross the transformation region and hence may transform into pearlite. Sir it's a request to clear this doubt because I am preparing for my exams.
What you have described is reasonable and possible.
Sir what will be the structure after martempering.
Martensite,
Sir, the complete structure converted into martensite after martempering or some austenite formed there?
It will completely convert to martensite if the final temperature is below Mf. If the final temperature is between Ms and Mf then some austenite will be retained.
Sir will there be change in crystal structure as more time is available here?
Well, there is a transformation involved from austenite (CCP) to martensite (BCT). But the same crystal structure change is involved in normal quenching also. Thus from a crystal structure point of view, the extra time available in comparison to normal quenching gives nothing new.