Heat Treating and UTS Graphs

[amtconi]

Hi everybody!

Looking for some help. I'm trying to compare and ultimately duplicate a 4130 tubing graph after UTS testing of two similar materials.

In graph 1, this is the material I currently have. The graph shows that it is very resilient up to the yield point and very linear (and typical of the UTS graphs I see from past testing).

In graph 2, this the material I want to duplicate. On the graph it is much more pliable and progressive all the way to yield on to max tensile.

Could this be a post welding heat treat that changes the material in graph 2 to act this way? Both materials are extremely similar in yield, UTS and elongation. They are also the same heat treat finish GBK (+A), and they also are extremely similar on the chemical analysis. I'm really at a loss to explain the large difference in the graph shape and what can be done to the material I have to make it behave in a similar fashion.

 

[EdStainless]

I would re-heat treat a few samples of each using slightly different tempering temperatures and see what you get.


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P.E. Metallurgy, Plymouth Tube

 

[amtconi]

What do you think it would take to produce such a unique graph as in graph #2? I do not typically see UTS graphs that look that shape.

 

[EdStainless]

Are you really sure that it wasn't the test?
Have you looked at micros?

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P.E. Metallurgy, Plymouth Tube

 

[amtconi]

Metallographic analysis was done on both samples. Structure description and decarb numbers were almost identical. I've had the samples tested more than once.

 

[Compositepro]

That looks like a testing anomaly, such as slippage in the grips. What is the specimen geometry and grip style?

 

[amtconi]

I had to have a lab make the tensile strength tests but considering all the tests on the #2 graph look like that graph I can't believe they made a mistake 3 more times.

I'm really at a loss to explain the graph shape. Seems like everyone I talk to can't explain how to get 4130 tubing to look copy the graph either.

I'd love to see a UTS graph for stainless steel tubing. I am wondering if it could possibly look similar.