Effect of Temperature on Hardness Testing

Carterwhopkins · Feb 10, 2019

I would assume for the highest level of accuracy and consistency that any testing of metal should be performed at the same overall conditions. My shop is not climate controlled and I was wondering what differences in results might be expected when testing one day at 35f and a few days later at 65f. I am using the Grizzly G9645 tester.

Ken H> · Feb 10, 2019

Could be a good bit of difference. At 35°F the oil is going to be really thick, while at 65°F the oil is thinner. Seems I read the temp "should" be in the 72°F range for best testing.

Larrin · Feb 10, 2019

Here is a small study:

http://annals.fih.upt.ro/pdf-full/2012/ANNALS-2012-3-66.pdf

Ken H> · Feb 10, 2019

Looks like they did a really good study - on a VERY narrow temperature spread, only from ≈55°F to ≈82°F. The OP was looking at 35F to ≈65°F, which is still ≈305°F spread, so maybe there's not all that much effect there? BUT - I'd suspect the low ≈35°F would affect the measurement more than the low ≈55°F would. I'd like to see something tested in the ≈35°F to ≈95°F range to see how much effect that would be. I suspect that range would be more inline with typical unheated shop temps.

Ken H>

Carterwhopkins · Feb 10, 2019

Thanks Ken and Larrin.

Ken, hope to meet you some time, I live in Hendersonville and have been looking at the Haywood class listing.

Larrin, appreciate the study and look forward to reading it.....though it kind of seems like a homework assignment.

I did check a test block and it read spot on....With all the talk of W2 this past week, I was testing some coupons from Aldo 1460f, 10-12 min soak, 65f Parks 50 - avg 67, temper 375f 1x2hr - avg 63, doing a 2nd temper and would expect to remain at 63.

Larrin · Feb 10, 2019

Carterwhopkins said:
Larrin, appreciate the study and look forward to reading it.....though it kind of seems like a homework assignment.

It costs extra for me to read and interpret the article for you.

Carterwhopkins · Feb 10, 2019

Would be $$ well spent...you will need to draw pictures also.

LCoop · Feb 10, 2019

I always loved the saying " xplain it to me like I'm a 6 year old!" I've learned a ton from Larrin's post and web site. Cant' believe someone with that much knowledge shares so freely to everyone.

I was talking to a OLD extremely knowledgeable HVAC tech the other day. I told him I'd love to just know what you have forgotten. After a pause his reply was " Yeah me too!"