Stihl crank case repair(welding)?!?!?!

[logdog]

Correcto on the brake cleaner being dangerous to the nervous system when heated.

I used to enjoy welding Volkswagen cases, magnesium wheels and things like that. Now it sounds like work.

Drill a small hole at the end of the crack then V out the rest of it. If possible, bake the part at about 350 to remove all oil residue. Place it on some hot fire bricks or anything that will help the part hold the heat while welding and cooling down.
If the part is mag, use AZ92A tig rod, argon gas and a low amp setting. Pulse weld with the foot pedal (on/off) and lightly peen each short weld including the parent metal on both sides of the weld. If you still experience light cracking, grind a small groove in the new weld and make another pass. Peen lightly. Cover the part in sand or anything that will allow the part to cool slowly.
That's it. Now, go fishing.

 

[Teddy.Scout]

Thanks guys!!!!

 

[volks-man]

Correcto on the brake cleaner being dangerous to the nervous system when heated.

I used to enjoy welding Volkswagen cases, magnesium wheels and things like that. Now it sounds like work.

Drill a small hole at the end of the crack then V out the rest of it. If possible, bake the part at about 350 to remove all oil residue. Place it on some hot fire bricks or anything that will help the part hold the heat while welding and cooling down.
If the part is mag, use AZ92A tig rod, argon gas and a low amp setting. Pulse weld with the foot pedal (on/off) and lightly peen each short weld including the parent metal on both sides of the weld. If you still experience light cracking, grind a small groove in the new weld and make another pass. Peen lightly. Cover the part in sand or anything that will allow the part to cool slowly.
That's it. Now, go fishing.

i have nothing to add. my arboristsite radar picked up on that word and i had to read the thread.

 

[bhyogy]

mag welding

I'm thinking about repairing an older stihl case, it has no cracks, only one of the top spike bumper mounting holes, it's broken peice is about 1 7/8" from the hole downward, I appreciate all of this input on the matter, Thanks :help:

 

[7oaks]

Interesting reading. I hadn't seen this thread before - or at least hadn't read it but this is exactly what I have been experimenting with recently. I'll try some of the suggestions.

 

[bhyogy]

Interesting reading. I hadn't seen this thread before - or at least hadn't read it but this is exactly what I have been experimenting with recently. I'll try some of the suggestions.

I am now watching some you tube videos on the matter:

Tig Welding Techniques and Welding Magnesium

also:

weldingtipsandtricks.com/welding-magnesium

 

[Bob Wright]

Here's an easy way to tell alum from magnesium just for thought. Put some solder flux on the part if it turns black its magnesium and it it stays clear its alum. I love fixing alum parts with my spoolgun but i can't do TIG for magnesium...Bob

 

[3000 FPS]

I know that alot of sanding disc and grinding disc are made with aluminum oxide. Aluminum oxide is what you are trying to get rid of by cleaning before welding. I always brush with a good stainless steel before welding.

 

[srcarr52]

IMHO mag is easier to weld then aluminum. Magnesium does not corrode like aluminum so you don't have the oxide film that makes it hard to see the weld pool or add filler. The keys to tig welding mag are the same as aluminum with a few extras.

Cleaning the material is key. I usually clean with a degreaser, bead blast and then ditch cut with a carbide or high speed steel burr. A little wd40 on the burr keeps it from loading up and doesn't cause a problem when welding as long as you preheat. I have said before that tig welding is 90% prep work.

Do not use a grinding wheel that has been previously used on steel because it will imbed tiny bits of steel into your material and show up when you start to weld. Use only stainless steel wire brushes because steal ones do shed tiny bits of material and rust into your weld surface.

Preheat, preheat, preheat... this is really key when you are welding to different material thicknesses, put more heat into the larger piece or when you first start your arc you'll melt the little piece before you get anything to stick to the large piece. I usually use a propane torch or a good heat gun and monitor the temp with a infrared thermometer.

As for filler rod, good luck with your local welding supplier. Most of mine don't even know that you can tig weld mag. This eBay seller is where I bought my last bit of rod through. eBay Mag Filler Rod 1 lb will last a long time.

Use all the standard setting on you welder that you would for aluminum. I prefer using gas lenses instead of collets because they have better gas dispersion. I also use a large diameter cup and make the gas flow after arc time as long as possible to cool the weld end and to make sure nothing sparks off because mag fires are dangerous.

Mag burns at a temp the splits water bonds on contact so it will turn water into fuel. The best way to put it out is to smother it, so have a bucket full of sand to dump on the part. I just weld it on a thick steal surface where if it does spark off I can just sit back and enjoy the fireworks but I haven't had one spark off yet.

 

[SkippyKtm]

IMHO mag is easier to weld then aluminum. Magnesium does not corrode like aluminum so you don't have the oxide film that makes it hard to see the weld pool or add filler. The keys to tig welding mag are the same as aluminum with a few extras.

Cleaning the material is key. I usually clean with a degreaser, bead blast and then ditch cut with a carbide or high speed steel burr. A little wd40 on the burr keeps it from loading up and doesn't cause a problem when welding as long as you preheat. I have said before that tig welding is 90% prep work.

Do not use a grinding wheel that has been previously used on steel because it will imbed tiny bits of steel into your material and show up when you start to weld. Use only stainless steel wire brushes because steal ones do shed tiny bits of material and rust into your weld surface.

Preheat, preheat, preheat... this is really key when you are welding to different material thicknesses, put more heat into the larger piece or when you first start your arc you'll melt the little piece before you get anything to stick to the large piece. I usually use a propane torch or a good heat gun and monitor the temp with a infrared thermometer.

As for filler rod, good luck with your local welding supplier. Most of mine don't even know that you can tig weld mag. This eBay seller is where I bought my last bit of rod through. eBay Mag Filler Rod 1 lb will last a long time.

Use all the standard setting on you welder that you would for aluminum. I prefer using gas lenses instead of collets because they have better gas dispersion. I also use a large diameter cup and make the gas flow after arc time as long as possible to cool the weld end and to make sure nothing sparks off because mag fires are dangerous.

Mag burns at a temp the splits water bonds on contact so it will turn water into fuel. The best way to put it out is to smother it, so have a bucket full of sand to dump on the part. I just weld it on a thick steal surface where if it does spark off I can just sit back and enjoy the fireworks but I haven't had one spark off yet.

Great post srcarr!
I started a thread where I was just starting to weld magnesium for the first time, and my first attempts weren't too pretty. I've come a long way since then, but I had to learn most of this the hard way. I bought a blast cabinet and that was a very good investment towards getting the cleanliness needed to TIG weld magnesium. BTW, I also use the same eBay seller to get my mag rods. Just in case anyone is considering this: you cannot use rods meant for aluminum, the weld will crack as it cools and you'll have a bigger mess than what you started with. Scarr is right in saying that having a successful weld in magnesium is 90% preparation, once you get that nailed down right, welding mag is almost fun.

 

[Beaver eager]

I was taught in Air Force Tech School to TIG weld magnesium by actually putting the tip of the Tungsten right into to pool of molten Mag. It does not stick like it would aluminum and actually does work. Ive done several old bow risers this way and so far so good. Mag runs real cloudy and has a powder over the top when done but thats fine. Mag will burn when you get it hot enough but with TIG welding you shield it with an inert gas preventing ignition.

 

[SkippyKtm]

I was taught in Air Force Tech School to TIG weld magnesium by actually putting the tip of the Tungsten right into to pool of molten Mag. It does not stick like it would aluminum and actually does work. Ive done several old bow risers this way and so far so good. Mag runs real cloudy and has a powder over the top when done but thats fine. Mag will burn when you get it hot enough but with TIG welding you shield it with an inert gas preventing ignition.

Here's a video that helped me:
<iframe width="560" height="315" src="http://www.youtube.com/embed/weqTWwaaL0g" frameborder="0" allowfullscreen></iframe>

 

[Beaver eager]

Gotta love video verification! It's been a while since I've done mag but it's like riding a bike. That and welding every day helps too. I'm spoiled these days with brand new materials going together and mostly stainless steel. I miss running titanium the most though. I just love a good titanium bead even though it had to be done in a chamber.

 

[Ward870]

I have welded many very thin racing cylinder head ports. I do not pre heat and I weld on DC POSITIVE very high frequency and high amperage in short bursts. When my head gets to hot to hold with my bare hands I stop welding and start to peen welds. I have a short piece of bicycle chain welded to the end of a 1/4 rod about 6" long and I run it at low speeds in my grinder against the welds to relax them. I know some people will say aluminum on AC voltage only and I used to be the same way until an old timer schooled me. The DC process has less warp and less time involved with out heat treats. Also less failures due to cracks at or near welds. I have done very little with mag and most with massive failures. Although I have seen it done by the hand of another in the same manner that I use for cast aluminum.

 

[benmyers]

I have had good luck repairing quite a few magnesium chainsaw cases. I assume you have magnesium filler rod? I have used aluminum on mag cases but it doesn't work very well.

To answer a few questions I've seen here:

1. Preheating helps but isn't really necessary since the application is so thin.
2. Use a good clean burr grinder of some kind to clean it up. Don't take it too thin though.
3. I found very high frequencies to work best. Some machines will do this, some won't.
4. Brake cleaner that is chlorinated is what typically causes major problems to the nervous and other systems when used to clean for welding. Phosgene gas is produced, which is deadly.

As Ward stated, it is very similar to welding cast aluminum- maybe a bit easier.

 

[3000 FPS]

Srcarr52 has done a lot of welding on chainsaws and I myself have done a great deal also. The advice that Srcarr52 has given is right on. The only thing I might do different is I do not always preheat.
I have many pictures of what can be done if you are interested. To the OP, just keep trying you get the hang of it.

 

[dl5205]

... Brake cleaner... is what typically causes major problems to the nervous and other systems when used to clean for welding. Phosgene gas is produced, which is deadly...

Worth Repeating.

 

[nmurph]

Clean, clean, clean.

 

[srcarr52]

Srcarr52 has done a lot of welding on chainsaws and I myself have done a great deal also. The advice that Srcarr52 has given is right on. The only thing I might do different is I do not always preheat.
I have many pictures of what can be done if you are interested. To the OP, just keep trying you get the hang of it.

I preheat cylinders and larger items. Cases and thin materials don't require it.