[Backyardmech]

I'm an Industrial mechanic at a plastics and fiberglass plant...lots of older machines and equipment. Well during one of my machine inspections today I found a badly cracked shaft...it's been repaired once. Not sure our miller 250 mig is the right welder for the repair? When I repaired it last fall I gouged the crack out and cleaned it up nice..this time it's way worse..cracked in 2 places almost all the way around..I think there were cracks on the inside I never seen? This pc of machinery makes man ways for water and septic tanks. Weighs about 1.5 tonnes.

[Coldman]

Any idea what the material specification is?
Also can you post a pic zoomed out a bit so we can see the whole thing?


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[Backyardmech]

Material is just reg. Carbon steel I believe. This winding machine is very old..I will get better pics tomorrow once I have it apart.

[Brettmm92]

From my experience, I would give the crack a nice, deep bevel, and spray-transfer over it. I'm no old timer but that seems to be a solid way to fix most mild carbon steel cracks. Hope all goes well!

[Arno]

As you grind out the part, do a spark-test on the clean base material at the same time to see if it's perhaps a high(er) carbon material.



Just so you're not fighting an uphill battle against a base material that gets hard and brittle and crack-prone after welding on it.

Bye, Arno.

[Poland308]

Even if it's mild steel it's very likely that that is a stress point that has caused the whole area around the crack to become work hardened and brittle. I would recommend a 250deg F pre heat and try to keep it above this temp even as you weld. Preheat at least 3-6 inches away from the weld as well. After you finish welding keep the temp up for at least 15 min before you let it cool.

[MarkL]

As you grind out the part, do a spark-test on the clean base material at the same time to see if it's perhaps a high(er) carbon material.

Arno, what book is that chart from?

[Backyardmech]

Here's some better pics...got part taken off today and cleaned and beveled the cracks..it worse then I though..
Thanks for the advice.

[LtBadd]

As you grind out the part, do a spark-test on the clean base material at the same time to see if it's perhaps a high(er) carbon material.

Arno, what book is that chart from?

Mark, google "spark test chart" or "spark test pdf" you'll have many results

[Coldman]

Whichever process you use, that crack is going to have to be bevelled out with root gap for full penetration weld with re-enforcement. The ends should be drilled to stop the crack.

It can be migged but you would need to be a solid mig welder to do it right with full fusion. Root pass downhill and fill/cap passes uphill.

Personally I think stick or tig would give a more reliable result.

[Poland308]

I would lean towards stick or tig as well.

[Arno]

As you grind out the part, do a spark-test on the clean base material at the same time to see if it's perhaps a high(er) carbon material.

Arno, what book is that chart from?

Very good question! It's a chart you see a lot online on blacksmith forums and such. The page does use kilograms and cubic metres. Perhaps a page from a US military training/reference book or Canadian/EU of origin. Don't find much other references though..

Bye, Arno.