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Welding O-1


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I ordered a piece of O-1 drill rod to use in a machine I'm building. I'm not entirely sure but I think its coming not-hardened. My question is; can it be welded by conventional means? I plan to use MIG and I need to weld it into the end of a piece of mild steel pipe as part of an axle type shaft. I'm not worried about rehardening as the O-1 should be tough enough for this application anyway...I hope. Just wondering if I can get away with welding it to mild. I figure I would preheat it a little anyway.
Thanks in advance for input

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I have not welded 0-1 as you wish to do, However I have welded quite a few different tool steels of lesser carbon content to mild steel, I would tack the two together with a mig and heat to red, then weld all areas that need it. Heat the entire piece to red and into vermiculite overnite. Never had a problem with this method and If I needed to weld 0-1 to mild would try it this way.

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For the correct numbers check out the library or welding supply. Heck, call or visit the welding supply, they'll tell you what to use. There a couple things to be aware of. First mig wire is low carbon so the join will be weaker than the shaft. If you don't preheat the mild plate anyway, it'll chill the shaft quickly enough to cause embrittlement in the shaft at the joint.

If you have one I recommend stick welding with the correct rod over mig's mild steel wire. Another trick if the design allows is to drill the plate and plug weld the shaft on and fillet weld the other side.

Regardless, this is a GOOD place for a little book learnin and ciferin.

Best of luck. Frosty the Lucky.

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Thanks guys :)
Frosty, no plate involved. What I have is 1/2" black pipe with the drill rod that is 1/2" diameter. It is being telescoped into the black pipe an inch or so and welded in place. Sorry for no being more clear in my OP. I was in a hurry and blasted out the post ;)
Rich, Thanks for the tip on heating and burying in vermiculite! It may have dawned on in me in my former life as a welder, but probably not :D Most of what I welded was mild to mild and occasionally SS to mild. This is a bit exotic for my brain box LOL

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O-1 is shipped annealed, and it can be a PITA to anneal once it is hard. I usually have to cycle it a few times at work to get it to soften up some.

What about a mechanical connection, and forget the welding? I am thinking about a cross pin through both, or a roll pin. With a cross pin you could make that out of regular steel, then just weld that to the pipe, no chance of hardening that way.

It's waaaaay past my bedtime, if you want more info on annealing O-1 try Googling it, or I can look up the info at work in our book.

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Hey Dodge,

What I sometimes do in that application is grind a notch in the "hard" or high carbon steel and line it up with a hole in the low carbon "weldable" sleeve and then plug weld and grind smooth. Even if it hot cracks on the high carbon it probably still won't push/pull or rotate out of there. Just food for thought. Good luck with your project. Spears.

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The final piece will have twisting force applied to it. I'm thinking I might try a mechanical as well as welded joint.

BTW, I found this @ westyorkssteel.com

Due to the high risk of crack formation welding of O1 tool steel should be avoided, if possible. When, however welding is essential, the following serves as a guide:

A. Welding of soft annealed O1 tool steel.
· Preheat to 300 - 500°C
· Weld at 300 - 500°C
· Immediately stress relieve
Electrode: Cr-Mo alloy electrode for welding structural steel.

B. Welding in connection with hardening of soft annealed O1 tool steel.
· Heat to hardening temperature.
· Cool to approx. 500°C
· Weld at approx. 500°C
· Direct re-heating to hardening temperature whereafter hardening (quenching) is performed in the usual way.
Electrode: Hard facing electrode.

C. Repair welding of O1 tool steel in hardened and tempered condition.
· Preheat to the tempering temperature (min. 200°C) previously used.
· Weld at tempering temperature.
· Heat immediately to tempering temperature, but max. 300°C. Soaking time 2 hours.
Electrode: Hard facing electrode.

They call for hard facing electrode but I figure they are assuming a O1 to O1 joinery. As I'm welding to mild, I'm going to gamble that my mig with mild wire (don't have the specs handy, but equivalent to 7018) will work. One welding forum I found, a guy did what I want to do; he pre-heated and welded with mig and then normalized and said it worked fine. He was extending the tang on a hidden tang blade.

Thanks again guys. Hoping to receive the rod in the next day or so. I'll be sure to report my results. Ain't R&D fun!! :D


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Dodge, I hope you don't mind me throughing my 2 cents. If you are going to weld your piece what you need to keep in mind is not the welding process, MIG or type of wire E70S-6 but the type of transfer here, which would be short circut transfer. It is prone for lack of fusion and could lead at some point to the toe of your weld cracking out on the O1 side. If you have access to a TIG and use a 309s or 312s filler you will have better results and follow the welding procedure you posted.

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Most welding references deal mainly with the thermal stresses involved. These are mainly shrinkage issues. The weld goes in as a liquid, solidifies and cools. In doing so it shrinks. That can create stresses that cause warping, distortion and even cracking in very rigid joints. Preheat helps to minimize the stresses by allowing the material to heat even more and cool at a rate closer to that of the weld.

With alloys and tool steels we also need to consider the transformation stresses. When we weld on heat treatable materials we raise part of it (in the "heat-affected zone") to above it's critical temperature. If it then cools quickly enough, by the colder part "sucking" out the heat, it's just like an extreme quench. We are in effect heat-treating it. Even though it was not our "intent" or "desire" it will still be hardened or heat-treated.

If we apply what we know of heat-treating, we now need to temper it. Any temperature below the critical temperature is tempering, even a dull red. Pre-heating helps to reduce the transformation some by slowing the cooling rate. Slow cooling after welding by wrapping or putting the part in lime or ashes will not help a lot unless the whole thing is at or near critical temperature. It's the cooling rate from critical down to around 1000F that matters the most, from there on down matters little. At this point (as in any quenching) we need to allow the piece to cool to near room temperature before proceeding.

After cooling all the way down, we can proceed with any post-heating, whether tempering, normalizing or annealing to alleviate the hardened condition.

Welding might not be heat-treating, but it sure feels like it.

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I know that O1 can be forge welded, but that may be another ball game. On the other hand, I've forge welded 3/8" square MS that was tightly inserted a little ways into a a 1/2"OD tube. The tube had a 1/16" wall thickness, no scarf.

But with fusion welding, I think you always get a different crystal and grain structure than the parent stock has. And as Grant pointed out, there is the heat affected zone, etc. The weld puddle, upon freezing, has an outshooting of "pine-tree crystals" so called from the fancied resemblance. Nowadays, we call it dendritic. I believe that is one reason that fusion welded metal sometimes breaks when an attempt is made to hot forge the weld, whereas forge welds are forgable, because they are solid phase welds (no puddles).

O1 is odd, because it will harden in air from a red heat, but it is an unstable kind of hardness. Not recommended. I have a feeling as a smith (not being a metallurgist) that after fusion welding, I would heat the area slowly to annealing temperature, 1450ºF, bright cherry red, and slow cool (not in air). I would leave it at that.

http://www.turleyforge.com Granddaddy of Blacksmith Schools

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