[Fabitfast]

I would like to ask some help from you guys. Why same chemistry steel from different supplies of hot band , after it cold reduction with Q&T behaves differently , at times lead higher corrosion - any insight to this problem ( 75Ni8, 76Cr1 steel ). Any information will be much appreciated. Thanks.

[fizzissist]

same chemistry steel from different supplies of hot band , after it cold reduction with Q&T behaves differently , at times lead higher corrosion

????
How about some specifics

[keebler303]

Different impurities, different batches, different amounts of residual stress, etc.

Unless you are comparing certifications, "same" is bologna. Look at the elemental analysis and compare.

[fizzissist]

Different impurities, different batches, different amounts of residual stress, etc.

Unless you are comparing certifications, "same" is bologna. Look at the elemental analysis and compare.

Certs will give you some insight, but even they don't tell all. How the alloying elements are added, mixed, how the metal is processed.... and if it's from china, it could be anybody's guess...
I give you something as mundane as drywall, or dog food by example.

Years ago we were getting cheap free-machining cold rolled steel from Japan... it was crap. Went back to domestic and the troubles went away. Of course that was years ago, and now their QC is far better..but it shows that there is a difference in how material is milled.

[Fabitfast]

????
How about some specifics

I mean, metals with almost the same chemistry behaves differently when done under some processes, and an example of their different behavior is corrosion level.

[RICHARD ZASTROW]

"ALMOST the same chemistry"?????? Small differences can cause large effects in results.

Dick Z

[Fabitfast]

Okay, I get it. So, please provide some inputs. Thanks!

[fizzissist]

I mean, metals with almost the same chemistry behaves differently when done under some processes, and an example of their different behavior is corrosion level.

Well now... That's almost too specific!

Given the differences even between 304, 304L, and 304H... Me thinks you need to do some more reading.

[txcncman]

Wow. Wonder if he checked for answers here: Need insights - Home Model Engine Machinist

Chemical composition % of grade 75Ni8
C 0.72 - 0.78
Si 0.15 - 0.35
Mn 0.3 - 0.5
Ni 1.8 - 2.1
P max 0.025
S max 0.025
Cr max 0.15
Mo max 0.1

Chemical composition % of grade 75Cr1
C 0.7 - 0.8
Si 0.25 - 0.50
Mn 0.5 - 0.7
P max 0.035
S max 0.035
Cr 0.3 - 0.4

I do not see how the examples are the same.

[fizzissist]

Wow. Wonder if he checked for answers here: ...

Chemical composition % of grade 75Ni8
.....

Chemical composition % of grade 75Cr1
....

I do not see how the examples are the same.

I think he's looking not at a comparison between those two alloys, but giving those two as the kinds of steel in question. That's ok,,, but....

Making knives? What? What's the application that brings differences between two different batches of the same alloy into question? That's what I was asking, because as you know, some materials can be ordered in a variety of conditions. Those conditions can be different on very subtle levels, but be dramatically different in behavior.

We can't answer anything unless we're all talking about apples-apples.
Solution heat treated? Artificially aged? Nitrided? Normalized? Annealed? Pickled (either end user or material)?

[mfgbydesign]

When steel is cold formed and / or Quenched & Tempered essentially the same thing happens: the microstrucure is disrupted and if you could see it at the atomic level there is displacement within the crystals along the slip planes that puts the material at a higher energy state which if done within limits it makes the material stronger and harder.
Hardening has the side effect (beacuse of the higher energy state) of making the material less noble and therefore reduces corrosion resistance. I don't recall the chemistry behind this and would have to check my reference material at home if further explaination is necessary.