4130 Steel Buildup 1

[KLENO]

Hello All,

I'm having a problem with some 4130 steel accumulating on a high-carbon, high-chrome, high-nickel (don't know exact concentration) stainless steel guide foot during rolling. The stainless steel is at about 300 F (due to ambient temperature) and the 4130 steel is at about 2250 F. The whole system is being sprayed with water. Not sure why this buildup happens with the 4130, as it doesn't happen with any other compositions.

Any help with possible reasons why this is happening or possible explanations for the problem would be really appreciated.

 

[metengr]

If this metal to metal repeated rolling contact is exposed to air and the 4130 is indeed at 2250 deg F you are oxidizing the 4130 steel surface and simply peeling this metal oxide layer off unto the softer stainless steel substrate. 4130 will agressively oxidize at 2250 deg F.

 

[KLENO]

Thanks for the help, and I think that's a pretty viable explanation, but I'm still struggling with why this would be an issue for ONLY 4130, and not any other grades.

 

[metengr]

What other grades are you referring to and at what process temperature? Are you sure about your observations?

For carbon and low alloy steel grades, exposure to air at metal temperatures in excess of even 1600 deg F will result in surface oxidation. Throw in water spray and surface oxides can spall or peel from the hot metal surface. Now you roll this metal oxide layer on a cooler substrate metal surface and it becomes enbedded.

 

[KLENO]

I've talked more with the rolling operator, and it seems the build up we're struggling with happens occasionally on other grades of steel, but almost always on 4130, which is why they associate 4130 with the problem. This speaks to your explanation pretty well.

However, x-ray compositional analysis of the buildup on several of the feet after use reveals that the buildup contains much more 4130 steel than oxide, so there's something more going on than just oxidation being removed from the surface, as the oxidized layer would have to be pulling quite a bit of the steel with it as it was being peeled from the surface.

 

[Metalhead97]

KLENO,

Is 4130 more or less scaley coming out of the furnace than the other alloys you process? Are you seeing any un-oxidized 4130 debris in the build-up? Sounds like there is still a lot of info that needs to be obtained.

Metalhead

 

[KLENO]

The 4130 doesn't appear much different at all from the other alloys. The composition of the build up is primarily un-oxidized 4130. I'm working on compiling all the data I have and looking at all possible parameters.

I'm really just looking for a direction to head with my research on this issue if there's anything you can think of off the top of your head.

 

[redpicker]

What other alloys are you processing?
Is there a difference in the temperatures used for the different alloys?
is there a difference in the sizes processed?

rp

 

[CoryPad]

Any chance the 4130 has high sulfur concentration and you are experiencing a hot shortness problem?

 

[mcguire]

Steels with chromium oxidize much more readily at high temperatures. Paradoxically, perhaps, but logically, chromium is the culprit. It has a very high affinity to oxygen and will really cause more oxide formation than a non-chromium bearing steel. At these temperatures you will get even sub-surface oxidation, because the oxygen can readily diffuse into the steel to get the chromium.

Minimize the soak time and suffer the unavoidable consequences of heating alloy steels to high temperatures. In fact, 2250 is way too high for alloy steel hot rolling. Are you letting the operators decide the process? It would appear so. They will always overheat to get more tons through with minimum mill loads. Time to retake control.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/