Flaw in 5160, or something I did?

[BrianT]

Hi Ed

I have encountered a problem with a blade I forged and am looking for some help to figure out why.

I forged the blade from 5160 and as I was going over the blade with a 120 belt in prep for hardening, I noticed what I thought was a spot from a hammer mark that I missed with my previous grits. I could not believe that I had not seen it before, but it was small and should clean up easily. As I proceeded, the spot got longer and longer, turning into what appears to be a crack. This crack runs parallel to the blade and runs up into the blade toward the spine not across or through the blade. This crack looks exactly like a cold shut on a damascus blade.

My question is: Is this a flaw in the manufacturing process, or is it something that I did? I have forged many blades from 5160 using the same processes without any problems.

When I forged this blade, I did not use excessive heat, and gradually reduced the heat during the forging process. The blade was normalized and annealed twice each.

Any help in determining why this happened would be greatly appreciated.

Thanks
Brian

[Ed Caffrey]

Brian,

It's very likely that it's a flaw in the material. I had this happen enough times within the past couple of years to almost make me quit using 5160. I'm not 100% sure, but my belief is that these flaws come during the rolling process at the mill, when the rollers are allowed to either run out of cooling fluid, or the rollers are not kept clean, and the steel basically gets an inclusion in it. Then, becasue I believe it happens early in the rolling process, the successive trips through the rollers cover it up.
It always seems to become visible for me at about a 220 or 400 grit belt. Sometimes, which is the most frustrating, is that it doesn't appear until I'm hand finishing. The more I try to get it out, the larger it becomes! At that point about all you can do is start over.
It's just one more signal that in an attempt to make more money, the steel companies are slacking on quality control. Of course this type of defect doesn't seem to effect 5160 that is being used as springs (it's primary use), and we are such a small percentage of 5160 buyers that the steels companies could care less if we have complaints.

[BrianT]

Thanks for the info Ed. I was hoping that someone else had seen this before. I could not figure what I could have done to get a crack embedded within the blade.

I can understand your hesitation in wanting to use 5160. This is my first occurance like this, and I am considering not using it any more. The problem is that I still have quite a bit of it so I guess I will take my chances.

Thanks again
Brian

[Ed Caffrey]

Brian,

Taking chances is about all we can do.......unless we want to scrap our whole supply of 5160. Something that might help...... I've found that if you discover one of these voids/inclusions, it generally will run the entire length of the bar. I keep track of which bar the bad blade came off of, and try not to use that particular bar unless I have to.

[Jon Christensen]

Brian,
I've had the same problem before. Actually I started seeing it when I was working on my JS knives. I had ordered some extra 5160 and the new stock was the culprit. Took quite a few wasted blades before I realized it was the new steel and not something I'd done.

I now keep all my batches of steel separate. Don't want to go through that again.

Good luck,
Jon

[BrianT]

Ed

You are right, you have to take chances. I have made plenty of pieces of scrap steel, but it was always my fault. Having a flaw in the material is something that was completely unexpected. The bad news is that I do not keep close track of my steel (until now) -- Another lesson learned.

I will continue to use 5160 because it is the steel that I am most knowledgable with. I have done a lot of experimenting with 5160 and am very confident with my heat treating of this steel. I guess that you have to take the good with the bad.

Jon

Funny you should mention that 5160 flaws first showed up when making your JS knives. Guess what the intent of this knife was? I guess some other lucky blade will get to go to Atlanta in its place.

Brian

[mete]

Making mass produced springs of the material probably involves using a nondestructive test to find the problem. But of course that won't help the blade smith !!!

[Quenchcrack]

5160 has about 1% manganese and Mn has a real tendency to segregate toward the center of the slab or ingot. When this material is rolled into coils, the segregation is worst in the center of the coils. The master coils are slit into many narrower slits and cut up for stock. If you get a center slit, you might be looking at a segregation band. Sometime the segregate bands initiate cracks because they get very hard just air cooling from the rolling temperature. You might also be looking at a large non-metallic inclusion. Rolls used in rolling this material do not actually get dirty, they are usually steam blown regularly to remove the oxides that might stick. They do get fire cracked and worn however. If you are using junk yard scraps, remember that leaf springs are prone to fatigue cracking over the years of constant flexing. If you are using JY steel, you take your chances.

[fisk]

Acutally you are being punished for something bad you have done. I can remove this curse by having you send me $20.
One place I have not found the cracks in 5160 is in round bar. I finally just went to it and just whup it flat and go forth.
j

[BrianT]

Jerry

$20 would be worth it!! I found a similar flaw in the next blade that I was grinding. I assume that once the curse is lifted, the flaws in my blades will go away also.

Thanks for the advice. I will have to try some round.

Brian

[Josh Blount]

Where's a good place to buy 5160 round stock? Every time I find a source it seems to dry up before I can get there Thanks,

Josh

[C L Wilkins]

I think a lot of what we are seeing is a result from recycling.

Like everything else, there is a permissable amount of roach legs and mouse droppings.

Craig

[tonym]

The best place to find 5160 round is to get the biggist local phone book you can find and look for spring shops that make there own coil springs. They always have remnants, usually around 9'.

I get mine from these people,9 ft for $10.00
http://benzspring.com/

Tony

[anvilring]

"Then, becasue I believe it happens early in the rolling process, the successive trips through the rollers cover it up. "

Yes! and if you think about it, the more subsequent "rolls" or passes through rollers it recieves, the more ELONGATED it becomes!! That's why they appear as "cracks".
I've had this problem for the past number of years but only in the 1.25x .250 stuff... .now I've seen it in my 1.5 inch material I got from Security steel not three months ago!! Now, when I use old WWII jeep spring or anything "automotive" from a 60's or 70's car, I have no trouble whatsoever (is that a non-hyphenated word??). That leads me to think THE MILLS ARE CUTTING CORNERS AND DON'T GIVE A ####. Well... ya can't blame them. Those little problems that plague us are a non-issue for the auto industry. So allow me to recommend Merciedes (sp?) spring or older US stuff and use a plasma cutter to halve the material. Forge your cutting edge from the non-plasmaed edge and go with the programme.....


happy hammers to all....

mitch