Hardness testing tubulars
Hardness testing tubulars
(OP)
When hardness testing tubulars, I have read that there is a certain thickness-to-diameter ratio required to get an accurate Rockwell test. Where can I find guidance on that? We have tested this carburized tubular 1020 with the Rockwell 15N scale and still get low readings, but I am not sure if it is my hardness testing method or the heat treat process that is the problem. Unfortunately, I cannot section the part to take a microhardness.





RE: Hardness testing tubulars
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RE: Hardness testing tubulars
Are you sure you are getting them into the quench quickly enough? Years ago, I was heat treating some 1020 tubes that came out < 45 HRC on a mounted section. They were quenched from 1560F, which was standard for the shop for carburized parts. I raised the temperature to 1700F prior to quench and they jumped to >60 HRC. They were so small that just transferring from the furnace to the quench allowed them to cool below the Ar3.
And, you should be running a coupon with your parts if the parts cannot be sectioned, so you can section the coupon to verify the process.
rp
rp
RE: Hardness testing tubulars
Good idea about the coupon. I included that on the re-write of the instructions.
We checked a part by reaustenitizing for 10 min at 1550 F and then oil quenching and found that the hardness jumped from HRC 29 to HRC 36.
I suspect that we should have used ammonia. I am specifying 5% of the endo gas but no lower than 4% to avoid void formation.
RE: Hardness testing tubulars
What is the OD and wall for these parts?
Do you correct for the curvature of the parts? If they are large diameter it isn't a big deal. On sizes under 1.5" it has a noticeable effect. When you test on the OD of a tube or bar the portions of the intention to the sides are not fully supported and you get indentions that are a little too deep, showing lower hardness. It may only be 1 point. I had a correction table somewhere but I can't find it now.
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Plymouth Tube
RE: Hardness testing tubulars
RE: Hardness testing tubulars
RE: Hardness testing tubulars
RE: Hardness testing tubulars
I am taking into account the roundness correction.
RE: Hardness testing tubulars
You have to cut up some pieces so that you can test on the OD while supporting it with a ball end anvil. It is the only way to know that you are safe with your method.
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Plymouth Tube