Increasing strength of steel through rolling



A 100% reduction in area? Like, "gone"?

Gak. I'll continue to look, but after looking at the first six links or so, the math exceeds me.

Any idea what the precent reduction was per pass? This will give me a rough idea I think...

While I've never done rolling myself, it seems the the load/ deformation is symetrical. I could see wear/sloppy manufacture being an issue, but assuming the mill is built with the intent of creating a high-quality finish/flatness specification, it seems that one would achieve good results. Obviously I can throw this idea out the window if the blank material was not correctly manufactured for this purpose... And, of course I could just be dreaming anyhow.
I was thinking of hardened/ground rollers several inches in diameter, a couple or more HP with significant gear reduction, and a frame that would (vastly) exceed requirements (no welded tubes!) so that nothing moves. Flex in the rollers would destroy any hope of flatness.
Anyway, thanks for the helpful info Ned. Certainly the type of help I was hoping for.
Regards,
Robin
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 2 Jun 2008 20:51:58 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

Well, almost gone. <g> If you take a 1/2" diameter rod and draw it down to .050 wire that's a 99% reduction in area.

Just looking at the formulas should give you an idea of what you're up against. To keep the forces low you want small diameter rolls; go too small and the rolls are too flexible. Small working rolls with larger support rolls backing them up is the usual solution to that problem.
A Sendzimir mill ("Z-mill") is the extreme case, and is the norm for rolling high tensile materials to tight tolerances and high finish. http://www.innse.com/colro/ne_activ.htm http://www.jfe-21st-cf.or.jp/chapter_4/4c_1_img.html http://www.ipmx.com/html/tour/zmill.html
You do have the advantage that your pieces are small, so you wouldn't need long rolls.

Around 15%.

I'm no expert, and there may be ways of controlling curl, but in the couple mills I've been around that were rolling discrete pieces rather than continuous sheet, distortion was an issue.

Thus the Z-mill.

No problem.
--
Ned Simmons

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Nice machines, and a good lesson in rolling mill design. I see what you're getting at. I certainly appriciate the links.
I had assumed that a larger working roller would increase torque requirements. I didn't even consider backup rolls.

That's not as much as I had hoped. Mind you, I also don't need hundreds of feet per minute feed (at least not yet). The real difficulty in this situation is that I can't really prototype rolling economically. If I really want to know, I'd have to pull the trigger and aquire a rolling mill (one way or the other). Expensive experiement.

Fair warning.
Regards,
Robin
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

That sounds like 2" sections of wide bandsaw blade. What material will it be cutting? You do realize that hardening or cold-working the steel won't make it any more resistant to deflection, right? Harder steel can bend further without taking a set, that's all.
I made some paint scraper blades out of a 10-for-a-buck blue hacksaw blade yesterday. It bent almost to a right angle before breaking, and the steel is so hard that it snapped like glass with no deformation at all. The blades stay sharp MUCH longer than the one that came with the scraper.
Today's project is making a 41" brake to bend aluminum to cover the window trim.
Jim Wilkins
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I remembered reading that when I was considering research for this application, and I read it again during that research on RCM :)
It's hard to fathom this idea. I'm not saying I don't believe it, it's just not intuitive. For this reason, I might as well just get some material and cut out a blank (Dremel and a hand drill) and start testing. Propane torch to harden the teeth.
Regards,
Robin
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 3 Jun 2008 16:49:56 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

Robin-What about buying a fine tooth bi-metal bandsaw blade and grinding your teeth into that? I know that in production quantities thin edges are heat treated using induction. The blade passes through the induction heater coils on a conveyor of sorts. Then depending on the material either air or fluid is used as a quench. Followed by another induction tempering coil if needed. I have seen film of this process. The HAZ is skinny and does not tend to warp the parts. Cheers, Eric
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Jun 3, 7:21pm, snipped-for-privacy@whidbey.com wrote:

I've done manual induction hardening using a hand-held unit (with a massive umbilical cord to a large machine) for hardening trim edges and form/draw rads on large stamping dies.
The problem in induction is the cost. The machines are bloody expensive. I'd very certainly investigate going with induction once I think I have something worth selling, but right now it's not worth the money/hassle.
Regards,
Robin
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Jun 3, 7:49pm, snipped-for-privacy@gmail.com wrote:

I know it isn't intuitive, that's why I mentioned it. An easy demo is to clamp two identical pieces of hardened steel in a vise with enough sticking out that you can easily bend them, then anneal one. I posted a demo recently using sheetrock screws, or you could try cheap (carbon steel) hacksaw blades. Heat one red to anneal it, let it cool, then see how they both bend as you slowly increase finger pressure.
In technical terms hardness raises the yield point but doesn't change the coefficient of elasticity. I think hardness restricts microscopic rearrangement of crystal boundaries or slippage planes.
You may have problems experimenting with hardening and tempering unless you have some way to measure the properties of your samples. The standard lab tests are hardness, usually measured as resistance to penetration, and elongation under load. The important number is the Yield Point or Elastic Limit, the force/area where the sample stretches permanently. There really aren't any simple, cheap, accurate ways to make these measurements at home. Common practice is to temper to a color appropriate to the tool's application. What are you cutting?
Jim Wilkins
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I'll take your word for it :)
I must say, however, that in my case the part runs significant risk of being forced beyond its elastic limit due to its thickness. In this case, strength does have a bearing on rigidity, so I'm not completely convinced that hardness is trivial. This will be a tool that people will abuse, and increasing strength/hardness will have an effect on the tool's usefulness.

I'm actually a tool and die maker by trade, so I have a certain amout of experience with heat treat and dealing with hardened versus soft materials.
I'm at a very early stage, so I'm not too concerned with the exact numbers involved. I'd get a hardness tester of some description, likely before I start building the tooling.

Wood, and at not very high surface speeds.
Thanks for the thoughts. It's very useful to go through the thought processes and try to be cirtical of all these issues.
Regards,
Robin
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Jun 3, 9:52pm, snipped-for-privacy@gmail.com wrote:

Sawmill bandsaw blade stock might be practical, then. Perhaps you could find some free dull blades to experiment with. Unlike some metal- cutting blades the set doesn't extend to the bottom of the gullet so if you remove the teeth you have flat material. The set on metal cutting blades is a nuisance to remove because the thin steel doesn't stick to the magnetic chuck of a surface grinder very well. In my limited experience these blades are tempered enough to yield a little rather than shattering dangerously when overstressed.
Jim Wilkins
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

I'll take your word for it :)
I must say, however, that in my case the part runs significant risk of being forced beyond its elastic limit due to its thickness. In this case, strength does have a bearing on rigidity, so I'm not completely convinced that hardness is trivial. This will be a tool that people will abuse, and increasing strength/hardness will have an effect on the tool's usefulness.

I'm actually a tool and die maker by trade, so I have a certain amout of experience with heat treat and dealing with hardened versus soft materials.
I'm at a very early stage, so I'm not too concerned with the exact numbers involved. I'd get a hardness tester of some description, likely before I start building the tooling.

Wood, and at not very high surface speeds.
Thanks for the thoughts. It's very useful to go through the thought processes and try to be cirtical of all these issues.
Regards,
Robin
Robin, The fact the modulus of elasticity, which determines stiffness is virtually the same for all grades of steel, and also for all grades of aluminum, brought me one of my greatest teaching moments. I had a young engineer working with me and we had an aluminum clamp frame in a packaging machine that was deflecting too much. He suggested using high strength aluminum and I agreed that he should check it out. The next day he came in and said "You knew didn't you! Why didn't you just tell me?" I said that it was engineering 101 and he apparently didn't learn it in school, but he'd remember it for the rest of his life now!
Sadly, I was right again. About 2 years later he committed suicide. No, he wasn't working with me at the time!
Gary H. Lucas
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Gary H. Lucas wrote:

Gary:
    Nothing like a story with a happy ending to cheer up the troops.
--
BottleBob
http://home.earthlink.net/~bottlbob
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I believe that H1 nitrogen steel is hardened into the 50's through work hardening. This is a rust proof steel used in cutlery.
I've heard that razor blades are hardened stacked together for HT. Obviously a deep hardening steel would be helpful (alloyed with manganese I believe?)
One cause of warping of hardened steel is that martensite (hard steel) is less dense than pearlite and other softer forms of steel. So hardening just the edge could possibly cause a warping issue. You'd certainly want to keep it very localized, perhaps laser? Many steels won't harden well with a quick heat (O1, A2, D2, M2 etc) because of carbon tied up in carbides, which require a longer soak at temp for the carbon to diffuse. Try 1095.
Some steels (D2 for example) are designed to retain austenite after quench to offset dimensional changes after HT.
One approach people take is to fixture the part and anneal it followed by sub critical anneals before quenching it. The part is heated and quenched bound between plates. This may not scale up well into production.
Another approach might be to fabricate most of the part from mild steel and braze or possibly just spot weld a cutting edge to it. Or perhaps like they assemble the teeth to bimetal bandsaw blades.
Just my .02
Nathan
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

1095 seems to be a fairly common alloy. Indeed, McMaster-Carr sells it in .025 thickness at C44-C51 hardness for not too much bucks. Certainly a possibility.

Yeah. Trying to keep the cost of each part low.

I looked into that type of work. Bimetal blades are electron-beam welded or laser welded. Both beyond my means at this point, although that doesn't mean I couldn't get someone else to make the coil for me. Shouldn't be too expensive if I'm willing to invest in a large (!) order.
Thanks for your thoughts. Helpful suggestions.
Regards,
Robin
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.