Lesson in cast iron.

[shenion]

Above is the thread block from by 6" vice. The center bolt hole is stripped.

The block sits inside a 2.5" square tube. No way to fit a MIG gun in there.

I had just gotten the Airco working and some nice Fleetweld 7018 rods. So I decided, why not try these new 7018's I Vee'd the back edge. Not much I could do on the rest.

As there is only 3/4" clearance on each side, I had to have the rods near flat for most of the weld. As I got closer to the front the angle was better and I actually got some penetration/fusion. Did some real nice beads on the front third. Slag came off easily. Could have use a bit more power, but was undercutting the weld as is.

I welded the front first and the block had raised ever so slightly in the back. Made the vice real stiff as the threaded rod did not turn easily.

The back foot was accessible at a steep angle through the bottom. Looks like a bit of slag inclusion (shown at arrow.) Rod had to be done at near 90 deg from joint.

Lasted about 6 months of abuse. Pulled it out it and it is a perfect example of embrittlement. The weld is fully crystallized and looks like sand.

The back "foot" is the important part as that holds the main force.

I'll get a longer bolt to use more threads and weld the back edge with 309 MIG wire. I can get to that easily with some grinding of the hole. I might be able to do the front too. Hard part will be grinding off old weld, it is very hard.

Another option is to get my O/A refilled and braze it. But will also have to get more brazing rods.

Would not have had these problems if the block had fit better from the start and the bolt was longer (only had about 1/4" of thread into block.) Cheap vice, but don't have the $$ to drop on a real one.

 

[snowcat]

A proper nickel rod, would help shenion, a 314 dissimilar would have been a far better choice than the 7018, effectively you buttered it with your initial pass thus the reason why the welds were much better with each pass....

Forget everything you have learned about penetration, you effectively trying to create a soft weld, the more you penetrate the more you dilute the parent material, which in turn causes Haz cracking, (High Carbon deposits) preheat is another way of helping to prevent this....

Try a Nickle rod, buttered with a 314, on the root, I wouldn't do a complete fill with S/S though, if you cant V prep for 3 passes, use just the nickle cast rod, this will not over harden and leave a machinable finish....

they are available in hobby sized packs BTW

 

[shenion]

Was only a single pass weld.

Yes, as far as penetration. It did undercut the weld.

I used SS wire on my band saw. It worked great with no cracking. The weld was very fluid so doing it flat would be best. It was hard and not very machinable; I ruined 2 drill bits trying to rebore a 1/2" hole. It is the pivot for the head, has lots of stress. No cracks, looks stronger than original.

For stainless, the US suppliers seem to have 308, 309 and 316. I don't see any 314.

Best I can find from my fav supplier is $35 + shipping for 1 lb Ni MMA rods. A bit more than I want to spend for a single use. Did find some Ni gas brazing rods, but I already have some gas bronze rods.

I did a lot of Oxy/MAPP brazing, until I got the MIG, it was all I had. Have a few rods left but the flux is flaking off. May just scrape it off and try using it with TIG.

I may have found an ebay deal on some bronze rods. Will know in a day or so.

Did try to grind more off. Geez it is like trying to file ceramic . I do have a gouging tip for the plasma, will try that.

 

[snowcat]

Sorry shenion actualy meant a 309, must of left me head behind this morning.......

You could tig with a S/S filler, Its bad practice,(Iv had me knuckles raped before by an inspector on here for suggesting it) and will undoubtedly cause subtle HAZ cracks, but it will join the material fine.....If your careful, you can use the filler to start the pool then use the base material to fill with...... personally id do that....

 

[shenion]

Well, went to hardware store to get longer 8.8 bolt to replace stripped one. While there was hoping to find some brazing rods. They had "US Forge, Cast Iron Arc rods". ****-poor description, but I assume they are some Ni alloy. Cost only $4 Will try them out tonight. They are 1/8", seem a bit big but do say they only need 75-110 amps.

No way i can get the TIG in there unless I have the tungsten sticking out about 3/4". Then hard to get the filler rod in.

 

[shenion]

Final fix:

Settings:

US Forge Cast Iron rods, 1/8" (3.175mm)
DCEP
Approx 90A, 85V OCV
​

I used the plasma cutter to remove all the old weld and cut back farther to get past the diluted zone.

The rods worked well. Real nice arc, The first pic is the back. Almost blind welding as I cant get a decent angle to view weld pool.

I had nothing to practice on and the Airco has no current scale, just 0-10. Had it at about 7/10 on the 20-240A range. I have determined the range is non-linear I would estimate about 90A.

Thick coating on the rods but not much slag and it comes off easily. Used about 1/3 of a rod.

The bolt is supposed to hold it in. The foot never fit properly so the bolt always worked loose. Then the block would pull up and bend the bolt.

Should work well. The lead screw is still real tight as when the block moved before it bent slightly when I tightened it real hard doing some crimp-on #1 wire lugs.

I know now standard soft steel rods/wire is the worst to use. I read that last year just after I fixed it the first time.