CPM Steel Clean Up Problems

flatgrinder

flatgrinder

Joined
Dec 20, 2005
Messages
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I purchased a piece of 3V and it took a lot of surface grinding to get rid of all the scale and pits.

I took it slow, taking off 0.0015" at a time ... by the time all the pits (some were larger than the size of full stops) were gone I had taken off approx. 0.020" total (0.010" from each side) from the bar stock. The steel was not hot at all, just warm, and when I released it from the magnetic chuck, the steel was significantly warped in at least two or three different directions. Makes me wonder if there are internal stresses setup from CPM's rolling procedure?

In comparison, ATS-34 seems so much cleaner? Less scale, quicker clean up. Less material waste.

Is it just me, or has anyone else noticed this? :confused:
 
S3V can be ,for some of us, A very difficult steel to deal with. On the other hand, CPM 154 can be a good way to go. Frank
 
Soaking the bar a day or two in ordinary white vinegar makes the scale much easier to grind off. I can't address the warpage thing because I haven't seen it yet in 3V or 154 (knock on wood).

I gladly pay extra for PG steel when I can get it. I seem to recall that Aldo will PG his steel for you, including CPM-154. I don't know of a source for PG CPM3V though.
 
I had Aldo grind me 2 bars of 3v recently and at least on the first one he had to take off .030 before the scale and pitting was gone. On the other hand I had a small piece from AKS that was just sandblasted from the mill, and it cleaned up pretty easily. I think a bar here had excess scaling during rolling, you can see marks on some bars where loose scale was pressed into the surface.
 
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I bought some last year and had the same problem..LUCKILY I got it thicker by accident and had room to get the icky out of it
 
Thanks for all the replies and advice! :thumbup:

I spoke to my supplier yesterday and it's considered normal to remove 0.015" to 0.020" to clean up CPM steels. (The warping is not normal).

It was a bit of a surprise as ATS-34 only requires about 0.005" removal to get to the good stuff (and Hitachi's stuff has been pretty consistent over the last couple of years).

I guess the moral of the story is to buy stock at least 0.020" thicker when working with CPM steels. Hope this info is helpful to other makers. :thumbup:
 
Flatgrinder: That amount of stock removal for clean-up is normal. As you found, a surface grinder without coolant (or with coolant, for that matter) is going to add a bunch of stress to the piece.

I like to de-bark on a 6 x 48 with a 60 grit belt, or two, or three, depending on the size of the stock.

You can probably anneal the piece again and it will copme back to flat. I know, it's a PITA.

RJ
 
I also think it was the surface grinding that warped it. You would be surprised how hot it gets under that wheel. If you drag and let the wheel sit in one place longer than others you'll notice that you take off more steel, the wheel isn't getting lower, the steel is expanding with heat.

If you grind after heat treating, you can just profile your blade, heat treat and plate quench and it will come out as flat as your quench plates.
 
Mr. Martin is correct. 3-V is a PITA. We have been Wide Belt Grinding all the CPM stocks before they go out the door. In most cases, if we mention it to our customers they have us grind the piece rather then do it themselves. I've been told by more then a few that has saved them hours in some cases.

3-V is particularly tough steel to roll, as is all the rest of the CPM steels. In most cases Niagara starts with 20 to 30 percent more material than what you end up with. There is that much loss in the rolling process. It's tough stuff even at rolling temps.

As for your mic readings across any particular piece you will always find a difference. Remember that Niagara is a Hand Rolling Mill. In spite of the size of the rollers they use there will always be a deflection. Usually thinner to the outside of the piece being rolled because in it plastic state the material wants to squeeze out left and right of the rollers.

Warping is an issue we have as well. We are able to keep it to a minimum because we have the ability to flip the pieces from side to side and remove the material evenly.This seems to help a great deal. Keeping it cool is a must!

Hope this helps
 
Aldo Bruno said:
In most cases, if we mention it to our customers they have us grind the piece rather then do it themselves. I've been told by more then a few that has saved them hours in some cases.
Click to expand...

When I start getting low on 3V and 154 I'll be in touch. I definitely feel buying ground stock is worthwhile in time and belts :thumbup:
 
Thanks for all the replies everyone. :thumbup:

Still not sure why it warped. During surface grinding, I did flip it by hand and picked it up afterwards, it wasn't hot at all -just warm.

I received a new piece of 3V from my supplier, and this one was a gem compared to the last. Only had to take off 0.004" total to clean it up. :)

I guess the hot rolled finish varies depending on the machine operator -maybe some employees are more skilled than others? Or the finish is cleaner when the rollers are clean?
 
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