Quenching and Hardness Testings

[snowJT]

Lets say I quenched two bars of steel, both 1040 steel, one was quenched in water, other in oil. How will that affect the hardness testing on the Rockwell scale, as well as impact tests?

And the higher the hardness of the steel the less it'll perform on the impact test right? Because it'll be more brittle the more martensitic it is.

 

[Astronuc]

Fully hardened 1040 steel can achieve a hardness of 57 HRC (Hardness Rockwell C) quenched rapidly in water. 1040 steel may not harden at all when quenched in oil.

from Heat Treatment/Thermal Processes, Sinclair Community College

Generally, the harder the steel, the more brittle it will be and would fracture at a lower energy in the Charpy (impact) test.

One might find this of interest
http://www.osti.gov/bridge/servlets/purl/836878-AegKFa/836878.PDF
HEAT TREATMENT PROCEDURE QUALIFICATION

Metallurgy of Steel for Bladesmiths & Others Who Heat Treat and Forge Steel
http://mse.iastate.edu/fileadmin/www.mse.iastate.edu/static/files/verhoeven/7-5.pdf

 

[snowJT]

very astounding pages... just incredable... one thing it doesn't talk about is the comaprison from oil to water quenching..

would that really be that oil can quench slower causing less deformation than water, but oil won't fully harden as much as water quenching would?

but the amount of information found in this is just incredible... the diagrams and detailed explanations are pretty good, I'm impressed.

Thanks

 

[Gokul43201]

very astounding pages... just incredable... one thing it doesn't talk about is the comaprison from oil to water quenching..

would that really be that oil can quench slower causing less deformation than water, but oil won't fully harden as much as water quenching would?

1. What do you know about the cooling rates produced by using water and oil as quenchants?

2. What do you know about TTT diagrams and the critical cooling rate? How the the cooling rate affect the % of martensite in the final microstructure? And how does this correlate with the final hardness?

PS: What is this for?

 

[snowJT]

I know a bit about cooling rates, and in terms of TTT diagrams, I know what most should look like for different metals, and what they should look like if there's an interrupted quench or if something is quenched longer, or if something is quenched to martin site, then brought back up.

I'm going to be quenching a few things tomorrow, and I'd just like to know some theory behind it, in case something goes wrong, such as now I know not to quench 1040 in oil...

 

[snowJT]

and 1040 steel obviously would have a higher Rockwell scale number than 1020 steel correct? but the 1020 would require more energy to break it?

 

[Astronuc]

These articles might also be of use - http://www.key-to-steel.com/default.aspx?ID=Articles#p2

Anyway, one would have to determine the impact toughness of 1020 and 1040. 1020 is a low carbon steel (0.2% C), whereas 1040 is a medium carbon steel (0.4% C). Given similar thermomechanical processing, i.e. similar working and heat treatment - I would expect the impact toughness of 1020 to be higher.

See - http://www.engineersedge.com/steel.htm - for some descriptions of use.

Also this - http://www.me.unm.edu/~zleseman/Lecture4.pdf


Physical Metallurgy of Steel
http://www.tech.plym.ac.uk/sme/Inte...rcarriage_Leg/Steel_Metallurgy_Ohio-State.pdf


Mechanical Properties of Structural
Steels (Draft)
http://wtc.nist.gov/pubs/NISTNCSTAR1-3DDraft.pdf

 

[Dr Game]

I take it you are or where a metallurgist? You have found some pretty impressive resources, usually it's hard to find such descriptive things on the Internet... it compares quite well with the books I have on it

 

[FredGarvin]

When it comes to materials information, the net has a lot of resources. You'll find most of the manufacturers have great information on their products. You just have to spend a little time searching. The info is out there.

 

[Astronuc]

I take it you are or where a metallurgist? You have found some pretty impressive resources, usually it's hard to find such descriptive things on the Internet... it compares quite well with the books I have on it

If referring to me, I do a lot of performance modeling/simulation of material systems which requires a knowledge of materials - metals and ceramics. My background is primarily nuclear engineering with a materials background. In addition, I've had the opportunity to watch those materials and products I simulate being manufactured. This enables me to relate the performance with the product and the product with the process. How one makes the material has a profound influence on how it performs in its intended (actual) environment.

I am also a member of ASTM, TMS, ASM International, and ANS MSTD (Material Science & Technology Division).