Filler Metal for Unknown Tool Steel?

I reckon it's the safest option :)

Careful if you're trying TIG. If the unknown rods contain zinc, they'll just explode and make a mess! Found this out when I went to try, thinking "great, I've got some brazing rods". Made a horrid mess. After getting the right rods, I was surprised how easy it was despite my inexperience with TIG. Move fast, short arc, don't be afraid to pull not push, it's actually much easier to feed the rod onto the hot metal while the torch is heating the next spot than running into the rod. Flies in the face of all TIG welding wisdom, but it is a different process, after all!
 
That doesn't look like decent penetration on that pin. There are good options on welding or brazing but if it were me i would get a chunk of 4140 and make new. Then chamfer the pin and the plate (30 degrees each) and weld with something softer like 309 L or 316 L. JMHO

I think those marks on the underside are grind or file marks from someone trying to down a proud weld.
 
I'm starting to reconsider the brazing. I watched Jodi's vid posted above by @rwm and there's possibility of cracking if some base metal gets melted in with the brass. Also since my part requires a butt joint, it's not ideal for brazing. Braze seems best suited for fillets and laps.
 
I agree with Old Mud- there is poor penetration with almost no penetration of the pin. Then they ground down the weld until the actual joint was very thin. Technically that is not a butt joint. It would braze fine with proper flux and heat and there would be no risk of distortion. If a small amount of warp would be critical to that part then gas brazing is the way to go.
Robert
 
Silver solder might also be a good way to go as it'll wick right through the joint. Agreed that the original method of popping a weld bead over it then grinding most of it off was not great. I'd heavily V it if welding or brazing it.
 
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I will chamfer the hole a good bit and bevel the pin.

rwm said:
If a small amount of warp would be critical to that part then gas brazing is the way to go.
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You think using a torch will result in less distortion? Distortion is a concern on this machined part.

Lo-Fi said:
Silver solder might also be a good way to go as it'll wick right through the joint.
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Will silver solder wick into a tight press fit?
 
My vote is on TIG welding the dissimilar steels with SS. I think you should be able to heat sink the base well enough that you could complete the TIG joint with less time and less total heat input than brazing. A SS join on dissimilar steel is a very strong joint.
 
Did some prep on the part. I beveled the pin no problem but when countersinking the hole my single flute c-sink cut a little then just started rubbing.

I got some of the weld out but not all. I was still able to file the old weld so it's not super hard.

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A little bit of the old weld is still there on the left side of the hole.

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Looks like penetration should be adequate. The V groove is almost half the thickness of the plate. If the countersink was able to cut I'd probably go a little further.
 
ericc said:
That base looks suspiciously like cast iron.
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Now that's a scary thought. But if you look at the first pair of pictures, you'll see ballies stuck to the base piece near the mating of the two parts in question that probably got there when they welded them together in the first place. It could be a friction weld, a resistance weld, or a plug weld, I don't know, but I'm betting that this is not cast iron and can be welded normally.
 
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