CRACKS: Production/Heat Treatment/Raw material failure?

[NilayR]

We have faced heavy rejections in past couple of months in the Roll Milling Rolls that we manufacture(like Work Roll, Idler Roll, Back up roll, leveller roll) for some of the big market players in the world. In all the materials we are facing this issue, no matter how big the Raw Material supplier is. We make purchase AISI D2/D3, SAE52100, AISI H11.
Mainly the cracks are located on the Barrel dia, precisely at the end portions of the barrel length.
HRc: for SAE52100 ranges between 62-66 HRc; for D2 ranges between 61-63 HRc; for H 11 between 58-60HRc.

The Raw material is thoroughly inspected when it comes in Chemistry, UT, Micro and macro testing with 100x,500x zoom microscope. if found in limits they are accepted, otherwise rejected there itself and are not used for further process.

According to my view these are Grinding Cracks, I have to understand what are the different types of grinding cracks and how they are occured. Mainly because the production people apply heavy depth of cut and feed rates on the Hardened roll during the HARD TURNING PROCESS/Grinding Process.
Please help me to understand this. Thanks in advance...

BELOW IS THE LINK OF DRIVE FOR MORE PHOTOGRAPHS:
[

https://drive.google.com/open?id=1JFixsfgLBE6M1JYTnlizPTJkJBSpKBOt

]

 

[metengr]

I would suggest you send this to a competent metallurgical lab for proper analysis to determine if the cracks are from machining or other processing steps. Otherwise, your wasting your time guessing or assuming.

 

[NilayR]

Thanks for early reply.

The problem is that I am unable to find some suitable metallurgical lab for testing.

We are having lab in house only. But, they are also unable to locate what is the exact issue.
Kindly suggest if U can, some other way either.

 

[metengr]

You can send samples of the cracked material to a metallurgical lab well outside of your geographic location. This is done routinely. If your internal lab is not capable of performing this type of analysis, you should seek an outside, independent opinion.

 

[EdStainless]

If these are all near the ends I also would be suspicions of the heat treat, it is easier to get quench cracks on the ends.
You do need a good outside lab, even if means shipping samples to another country.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[weldstan]

Agree with Ed. They look like quench cracks on rolls from my very distant past experience.

 

[NilayR]

ALL THE PROCUCTS ARE HIGH ALLOY STEELS: HiCHiCr materials.
May be probable chances that in D2/D3 - Hi Cr% material, after tempering, straightening process is done. May be this leads to the cracking and all of these are straightening cracks.

Also probable chances of Quenching cracks.

 

[Dhurjati Sen]

Dear Nilay,

As a beginning, carry out a PMI analysis and take hardness of the rolls at your end.

Regards.

DHURJATI SEN

 

[EdStainless]

Proper lab work can tell you if the cracks happened during heat treatment or after.
Don't guess.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[WKTaylor]

NilayR...

1. I get the need for high surface hardness... but why full-depth hardness? This seems like an ideal situation for surface hardening processes [nitrogen or case] with a lower HT core thru to the ID.

2. None-the-less... for extreme high tensile/hardness steels are You following protocols identified in these [or similar process] documents...

SAE ARP1110 Minimizing Stress Corrosion Cracking in Wrought Forms of Steels and Corrosion Resistant Steels and Alloys

SAE ARP1631 Manufacturing Sequence for Fabrication of High-Strength Steel Parts 300M or 4340 Modified Low-Alloy Steels 270,000 psi (1860 MPa) Tensile Strength and Higher

3. Another obvious question to ask Yourself is: IF the HT process was stable/successful for years but suddenly has become unstable/unsuccessful... then what SMALL process detail(s) changed since then. A refined/careful process exam/comparison it vital on YOUR part. This includes going thru material procurement back to raw material melt.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]