Ok all you metalurgists...

C

Crocker Knives

Joined
Jul 24, 2005
Messages
29
I have a friend who has a tool manufacturing company. He ran a 1000 lb load of pliers made from 1055 at 25 degrees f over critical for one hour in a 70% atmosphere. He oil quenched and tempered at 825 degrees f. The pliers came out in the low to mid RC40's. I observed the hardness test myself. They break like glass!!!! Upon observing a fracture, the grain structure looks very fine. The steel supply company assured him that the alloy is 1055. A spark test looks like the carbon is higher than .55% to me. With an acid etch of a fracture there is a clear ring a few thousandths in.

This one has confused me. My first recommendation was to have a lab verify the alloy. Any ideas or thoughts?
 
It's spelled metallurgist ! 70% atmosphere ? carburizing ? Anything at HRc 40s should not 'break like glass'.
 
Doesn't sound like 1055 to me, at that low of carbon and high of temper, it should have bent 90% with out breaking.
 
Yeah Mete, I know how to spell metallurgist, but I don't know how to edit headings, and I type like a monkey. He was using city gas that is processed to be a carburizing atmosphere. It's a large industrial heat treat furnace with a self housed quench. I agree with both of you, but I watched him hardness test a blade I made of 6150 at RC58 (which is right what I was trying for), and then use the same hardness tester on a pair of pliers that showed RC43. He then tapped the pliers handle and it broke like it was 1095 as quenched. I've never seen anything like it and had no explanation for him. My only suggestion was an alloy analysis. I was hoping there was something going on above my knowledge that one of you formally educated metallurgists might be aware of.
 
It would seem that there's something grossly wrong there.Was it tempered ? Sometimes a part or parts 'escape' tempering.Contaminated gas .Temperature way off .though you'd see that in the grain size.Wrong alloy , though at 800 temper even that shouldn't cause brittleness. ????
 
what about " blue brittleness"... thought i read somewhere that some steel can become brittle after tempered at high heat ?

or maybe not... ??
 
You said "With an acid etch of a fracture there is a clear ring a few thousandths in. "
Maybe the ring is decarb, which might give you a bad RC reading.
But 1055 should definitely not break like that. 1045 I've used took a lot of effort to break, even right after the quench, with no tempering.
 
I would think at 825 they would almost be annealed. I'd try bending a pair that hasn't been heat treated and see what happens.
 
I ground one down and checked the core and it was RC38. Tap it with a hammer and the pieces fly. It just doesn't add up. I should have the lab results on the alloy Monday. We took a piece of the steel and heated it to 1450f and quenched it in 180f, 14 second oil. It was as-quenched at RC62. Critical for 1055 should be closer to around 1475-1500f. This steel doesn't act or spark like 1055 as I know it. We will see. Thanks for the ideas.
 
The lab test came back and the material is 1095 not 1055. If nothing else at least I know my eye for the spark test is still calibrated. Fixing it will be easy now. Thanks all.
 
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