Rebuilding flat edges after heavy abrasive wear - using copper for build up

[treemuncher]

I have not seen anyone else post this welding trick that I learned many years ago. I should pass it on so maybe it will help someone else. When trying to rebuild a fine edge or build up a flat edge, a piece of heavy copper flat is indespensible when using a build-up weld to repair a worn part. The new weld material will NOT weld to the copper but it can be flowed across the copper to build up a flat edge. Without the copper, you end up with a rounded edge IF you can get the rod or wire to hold onto the edge. With the weld flowing over the copper, you can build up flat edges even to very thin dimensions for cutting edges if needed.

In this particular case, I've let my side tooth holders wear too much from heavy abrasive wear on a Seppi cutterhead. These teeth wear away from abrasive action with rocks and sand. The outer edge tooth holders and teeth take the worst abuse and have the fastest wear rates compared to any of the holders towards the interior. They need attention every so often otherwise, I'll have to remove the drum in order to replace the outer tooth holders. Maintenance is cheaper than repairs.

Here is an idea of the amount of abrasive wear that goes on with this machine. The worn tooth was replaced with a new tooth (just the two outermost teeth) because the amount of wear was causing an imbalance AND allowing abrasive wear to affect the tooth holder because so much of the tool metal was washed away. Note that about 20% of the bolt head has washed away because so much of the tooth has washed away from abrasive wear. This tooth came off of the right side and you can see how most of the wash is on the right side.

The new replacement tooth - note how much more steel is on the new tooth. These teeth set into the tool holder that will be rebuilt.


The tooth holder is missing over 1/2" depth of material from abrasive wear. I need to rebuild the side closest to the housing as that's were the most metal is missing. I've clamped a pure copper buss bar to the side of the edge that I need to rebuild. You can see what's left of the hardfacing material on the tooth holder (shiny area) from previous build-ups.


Here I have started the rebuild. I'm using Washington Alloy 700HT 0.045" mig wire for my harfacing & build up filler. You can see where I weld and drag the puddle right up to the copper bar. No worries - it won't stick but it will dam the weld puddle and hold the edge. The only prep that I do to the copper is to brush it clean and hit it with a coating of anti-spatter spray or aerosol cooking spray (cheap Pam substitute - about the same as antispatter). I make numerous passes to bring the tooth holder back up to original dimensions.

 

[treemuncher]

You can see on this pic that I've rebuilt the majority of the edge. The resultant rebuild has a flat profile with a sharp edge....until I put it back into service.


The finished rebuild with a nice, flat profile.


For those not familiar with a Seppi cutterhead, this is what it looks like: a 10k lb attachment that dishes out pure punishment to anything in it's path. However, according to Newton's 3rd law of physics - For Every Action There Is An Equal And Opposite Reaction - this machine takes in just as much abuse as it delivers.

 

[materthegreater]

Very interesting, thanks for sharing

 

[materthegreater]

How do you like the Washington alloy wire by the way?

 

[treemuncher]

How do you like the Washington alloy wire by the way?

I've used several different compositions of the WA wire, both for hardfacing and general use. I really like it. Once I get the settings right on the MIG, it transfers smooth & fast and leaves a good looking bead. It's a fair amount cheaper than other name brands but still holds very good welds. If I can't find a composition that I like for cheap on Ebay (name brand stuff), I go to the WA for a new spool.

 

[John C.]

I've used both copper and carbon rod for repairing wallowed out bolt holes for things like cutting edge mounting holes on dozers and graders.

Real nice post and good looking work!

 

[Tones]

I have a tip for you treemuncher. Prior to fitting new teeth remove the tungsten tiles (they are brazed on) and with your trick with the copper plate cover the area where the tiles sit and spray tungsten on the areas of the tooth that wash out and refit that tiles. Doing that can double the tooth life. I used to buy teeth that came like that so have experience of comparison.

 

[terex herder]

For those of you unfamiliar with the heat transfer properties of copper, let me assure you the heat transfer is dam near instantaneous. Nothing like steel where one end can be red hot and a 12" piece can be held on the other end with a bare hand.

If you know a machine shop with a sinker edm machine, the used carbon electrodes can be used just like copper. The carbon can actually be easily ground or carved if you need to create a special shape or profile. Just do the work on the carbon outside, away from doors, and while wearing dirty clothes.

Tones, you have experience with brazing tungsten carbide that isn't readily available. Brazing large carbide blanks that will be rotated at speed should be approached with caution.

 

[Tones]

All forestry mulchers that run tungsten carbide teeth have the tiles brazed on, so do stumpgrinders . Its the way there are manufactured https://www.kingkong-tools.com/en/forestry/forestry-mulchers/prinoth--ahwi

 

[terex herder]

I realize that is the way the factory parts are made. What I was attempting to point out is the brazing of large pieces of carbide to large pieces of steel is a non-trivial exercise. The fact you can do it successfully puts you in a small minority. Even heat without overheating using an O/A torch is an art. Factory parts are induction heated for brazing.

 

[treemuncher]

I have a tip for you treemuncher. Prior to fitting new teeth remove the tungsten tiles (they are brazed on) and with your trick with the copper plate cover the area where the tiles sit and spray tungsten on the areas of the tooth that wash out and refit that tiles. Doing that can double the tooth life. I used to buy teeth that came like that so have experience of comparison.

Thanks for the info, Tones. I used to rebuild the edges of my swing hammers on my first head..but that was long ago before I got over the hump. That was when I learned the copper trick so that I could feather out a new leading edge with hard rods. I even had a jig built to hold the hammers in the correct angle to speed up the process and get the metal to flow just right.

These days, time is money and it's cheaper for me to just bolt on a new set of teeth and get on with the work. I used to purchase the spackled teeth with the extra carbide but they stopped offering them. I've just adjusted my pricing to compensate for the faster tooth wear and get on with the work. It's better for my health if I'm not doing so much hardfacing anyways.

 

[daveyclimber]

Nice tip, thank you.

 

[Welder Dave]

I know this is an old thread but it should be noted that most true hardfacing is limited to 2 layers. To build up badly worn components you should use a special "build up" filler metal that is medium hardness but has good mechanical and strength properties. It won't mushroom like a mild steel filler will and won't spall like hardfacing can. Do the last 1 or 2 layers with the high hardness hardfacing. I'm not familiar enough with the wire treemuncher used as far as if it's a medium hardness that can be used for multiple layers or if it's a higher hardness that should be limited to 2 layers. It is common on some applications to just build them up back to size with a medium hardness filler. This is a great thread. I just wanted to caution that you need to read the labels of the hardfacing you intend to use to see how many layers it is recommended for. It would suck to build up a part with say 4 layers of 60 rockwell hardness wire only to have it break off in chunks(spall). The copper casting method is a great way to bring parts back to original size. Sometimes you can even cool the copper on the back side so it doesn't get too hot.

 

[1693TA]

I have several sections of copper buss bar material saved from electrical apparatus installs for welding shoulders, or backer purposes and is used a lot.

Dave is right on the correct filler for buildup and hardfacing over the top. That is what I did often starting out. Used a lot of Stoody 35, and Stoody 31 filler for the hardfacing, and a Hobart Brothers filler for buildup on cutting edges and such. This was all stick and a lot of air arcing out of teeth and cracks to repair etc.

 

[Welder Dave]

Kind of late but an air arc is a lifesaver when dealing with hardfacing. With a little experience you can tell just when the hardfacing is removed. Hardfacing usually has a very slight green tinge when gouging it off.