Bending 304 stainless steel

If you use heat, 300 series ss is easy to bend and can be bent in *very* tight radiuses without using a bender. (Please note the twistwork in the hook of this hoofpick ) IME, the forging/bending window is rather narrow: 300 series bends easiest at a bright red going yellow; it starts falling apart at a bright yellow and won't move much at a dull red.

Sorry, I cannot get it red hot, all I have is propane torches with $2 propane bottles.

i

Igor, I think one of the compact HF bench benders might work well for this application. I bought one recently, after all the discounts & coupons I was out the door for $42. I could probably easily and quickly resell it for $30, so if you owned it a year it would be about a buck a month ..

GWE

OK, $42 is not bad, I will look into it on their website.

i

No heat, you'll have to use brute force with a bender. And brute force gets you bends in the straight sections you didn't want, and might even cause cracking at the bend.

You just might have to break down and get yourself an Oxy-Acetylene rig for a heat source, Iggy... A Rosebud tip would be exactly the 'hot ticket' you need to warm that bar stock right up.

And if you scrounge, it can be done cheap. (He says with a straight face to the guy with the four Mil-surplus Diesels in his side yard...)

Rosebuds and big cutting tips usually call for the big bottles. You could use a "medium sized" 'B' Acetylene/50CF O2 rig, but you would need to stop and wait an hour between heating each bend because of the

1/7 per hour rate-of-draw limit on the Acetylene bottle.

Forget about a "MC"/20CF "Porta-Torch" kit, you'll get one good "Poof!" and that'll be about it from that set of bottles. They are meant for brazing AC Lines in tight spaces, and that's about it.

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Bruce, thanks a lot... You see... I did buy a O/A set for $50 two years ago. But I was afraid of acetylene and had no space, so I sold it for the same amount to my mechanical genius friend. Who is very happy with it, his weldor buddy says they do not even make them like that anymore, but unfortunately he is 3 hours away.

I could cut the steel and simply tig weld it, but that would make sharp corners, which, I think, would not look as good, but that could be fine with me.

i

Yes. Just before they snap like dry twigs.

304 is NOT the best choice for this sort of thing...

Gunner

"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences."

- Proverbs 22:3

Iggy..time to buy a O/A rig..or scrounge one up. You are long past the stage where you need one.

Gunner

"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences."

- Proverbs 22:3

Gunner, do you mean that 304 is bad for bending? If so, I could just cut them and weld them to shape, right?

i

Tom, I've never heat-formed 300-series metal, but I heard that it loses it's corrosion resistance when heated beyond a certain point.

Does this happen in this method? If so, how does one either avoid it, or restore the metal to its original corrosion-resistant properties?

LLoyd

Just bend it cold and don't worry about it. Elongation to fracture for T304 is about 70%; for comparison elongation in A36 is 20%. IOW, you can stretch T304 over 3x as much as common hot rolled steel before it'll break.

You can bend 3/16 x 1-1/2 easily in a sturdy vise. Pound on the back side of the bend with a BFH as you're bending if you want a relatively sharp bend. If you want a larger radius, clamp a couple pieces of heavy flat bar on either side of the SS an inch or so from the vise jaws. This will limit the bend to the unsupported section of SS between the heavy bars and the vise jaws.

Ned Simmons

That's cool.

Thanks Ned.

i

Ignoramus29180 wrote in news: snipped-for-privacy@news.alt.net:

For simple heating/cutting (not welding) why not use Propane instead of Acetyline?

Short answer: I have no idea. (g) Some of my hoofpicks forged from 316 have been in daily use for five or six years without losing their corrosion resistance to barnyard chemicals, but that might have more to do with the polishing than the forging - at any rate, none of 'em have rusted.

The issue is carbide precipitation, whereby small amounts of carbon in the alloy combine with chrome along the grain boundaries, leading to intergranular corrosion. This happens in a range known as the sensitization temperature.

The most common ways around it are:

-Use L (low carbon) grade stainless steels (304L, 316L).

-Use a SS alloy that has constituents that have a higher affinity for carbon than chrome's (columbium in type 347, e.g.).

-Redissolve the carbides by heating above the sensitization temperature and quench so that the carbides don't have time to reform.

Ned Simmons

After heat bending or welding you can restore the corrosion resistance by passivating in dilute nitric acid. You can also buy passivating pastes at most welding supply shops. I think it eats away the free iron and carbon that separate during the heating process so that the chromium skin can reform. I passivate with Citrisurf before polishing my welded fittings.

304 and 316 tend to be a bit brittle when cold formed. Bent. You WILL need heat.

Now on the other hand..you have a nice beefy TIG machine..right? TIG machines get things so hot they melt together..right?

Why not simply heat the bend area with the TIG until its a nice red heat and then bend? It takes considerably less time than you would think. I would use as big an electrode as you can..ball end it to give you a "rosebud" effect. Ive used TIG many times to do bends where using my torch would be way over kill.

Gunner

"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences."

- Proverbs 22:3

Or you can google for "reil burner" and build something with off the shelf parts and hand tools . I built two (slightly more sophistocated , since I have more tools than some) for under twenty bucks . Twenty or so more for a used regulator , a couple of firebricks and the propane bottle from your grill , and you're in business .

I've heard lots of complaints about 304 and 316, but never that they're brittle. The elongation to break, a measure of ductility, of the austenitic (300 series) stainless steels is as high or higher than any other ferrous metals. One consequence of this, familiar to anyone who's struggled with it, is the tough stringy chips generated when turning

304/316.

Ned Simmons