case carburising
case carburising
(OP)
hello all,
i have written this query before but due to technical problem with login i couldn't view the opinions.
so here it is again
This is specific to case hardening of 16MnCr5, what could be the probable reasons for getting retained austenite and carbide networks in the case. the required depth is 0.3 to 0.7 and hardness is 58-63HRC.
what is the effect of Retained Austenite?
what is the effect of presence of carbides?
i have written this query before but due to technical problem with login i couldn't view the opinions.
so here it is again
This is specific to case hardening of 16MnCr5, what could be the probable reasons for getting retained austenite and carbide networks in the case. the required depth is 0.3 to 0.7 and hardness is 58-63HRC.
what is the effect of Retained Austenite?
what is the effect of presence of carbides?
RE: case carburising
RE: case carburising
C: 0.14 to 0.19
Si: 0.40 max
Mn: 1.00 to 1.30
Cr: 0.80 to 1.10
Retained austenite is always present in significant amounts in the cases of carburized steels that are quenched to room temperature. This is due to the increased carbon content which significantly lowers the Ms (martensite start) temperatures and depresses the entire temperature range for martensitic transformation to below room temperature.
The carbides that form upon reheating (tempering) are another common feature of carburizing. As the steel is heated, the carbon content of the austenite is reduced, Ms is increased, and the resulting structure has a reduced amount of retained austenite.
You need to determine if the amount of retained austenite is excessive and if the carbides are "massive". If the amount of retained austenite is greater than 50%, then the resulting hardness will be significantly lower, as will the fatigue strength. The most common cause for this is too high a surface carbon concentration. This is also the cause of massive carbides-- these carbides form during the high temperature stages of carburizing or when the temperature of the part is lowered to ~ 845 C just before quenching.
You should consult some references on the heat treating of steel for some background on the case hardening process (carburizing). I highly recommend ASM HANDBOOK Volume 4 Heat Treating. There are several articles on the various processes (gas carburizing, pack carburizing, etc.) and the resulting microstructures and properties. You can obtain this book from ASM International at http://www.asminternational.org . They will also have other references on heat treating, that may be of use to you.
RE: case carburising
Leonard
Jesus is the WAY
RE: case carburising
the heat treatment given was 920deg C 2hrs 30 mins, 840 deg 45 minutes, oil quench!!
i have retained austenite > 50% till 0.3mm depth and carbide network till 0.1mm,
what could be done to reduce the retained austenite and carbide networks... any suggestions in the process!!
RE: case carburising
RE: case carburising
i would like to know today what are the methods and instruments available to measure carbon concentration and the set points.
please tell me the expensive as well as non expensive ones? suitable for which kind of furnace(s)?
what is generally being used in the heat treatment industries very commonly? and to what extent can we fetch information?
RE: case carburising
Heat treating equipment is outside of my area of expertise. I recommend you consult with someone more familiar with this topic. The first place to look for more information is at the website of the ASM Heat Treating Society (http://www.asminternational.org/hts/Index.htm). The monthly magazine they publish is called Heat Treating Progress, and it is the best source of information on suppliers in the heat treating industry.
As an example, there is an article in the April 2002 issue of HTP that is directly related to this topic:
"Atmosphere Monitoring & Control" authored by
Robert T. Oesterreich, Shahab Kazi, Richard F. Speaker, and John E. Buonassisi of Air Liquide America. A summary of the article reads, "This basic guide to instruments for atmosphere analysis explains how each is used to help optimize heat treating processes. The various levels of control also are discussed."
The magazine also has a Internet Directory with which you can search for companies involved in heat treating. Follow the link below, and then select "Heat Treating Equipment and Supplies" on the Companies involved in tab, and select "Commercial sites" on the website type tab.
http://www.asminternational.org/Template.cfm?Section=InternetDirectory&NavMenuID=662
RE: case carburising