I wish I could weld

[k0ua]

I've never had trouble stick-welding metal "this clean" (no scale, and lots of bright metal). I can imagine a little trouble MIG welding it, the wire pushing back a little if you step ahead too far, or with low power. With a MIG, you'd want to stay within the bounds of your puddle for this metal. I would not even give it a 2nd thought with a stick (1/8 or bigger). Maybe with 3/32 stick....but I would never use that size cuz I have MIG. Plus I'd have hard time making a weld that nice with 3/32".

Shows up real good in this test-plate pic. Down in the bottom of a 3/8" groove there can't much heat left with a 120v machine. Didn't this problem appear when welding 3/8" thick material with a 120v machine as an exhibition, a full 50% thicker than the machine's recommended capacity? That's an example but not good example because a newbie shouldn't be welding 50% thicker than the machine's rating. That's for experienced welders.

If a newbie welder were to keep within the recommended capacity of the machine (3/16 - 1/4").......is "a pretty MIG weld that falls apart" a genuine concern that needs to be taught to the newbies (and oldies)? If it's genuine, someone should be able to replicate it, or show the forum an example.

Which amounts to be showing what NOT to do. Thats what this forum needs more than just writing about pretty welds failing. Can anybody show a pretty weld that failed (in real life)? STx do you have a pic of that pretty weld you pulled apart with your hands?

I saw one of a tooth welded to a toothbar on this forum. It was pretty, and when the tooth pulled off, you could see that there was hardly any penetration. This was a factory weld. It just wasn't hot enough. The weld metal was just laying on top of the toothbar, and only a couple of tiny spots that the parent metal was penetrated at all. I don't know that I could find the post though. It was a few years back.

 

[k0ua]

Look at post 12 for the lousy penetration pix.

http://www.tractorbynet.com/forums/kubota-owning-operating/200975-oh-oh-iowa-farms-flat-2.html

 

[Sodo]

I saw one of a tooth welded to a toothbar on this forum. It was pretty, and when the tooth pulled off, you could see that there was hardly any penetration. This was a factory weld. It just wasn't hot enough. The weld metal was just laying on top of the toothbar, and only a couple of tiny spots that the parent metal was penetrated at all. I don't know that I could find the post though. It was a few years back.

Look at post 12 for the lousy penetration pix.
http://www.tractorbynet.com/forums/kubota-owning-operating/200975-oh-oh-iowa-farms-flat-2.html

OK thx James here's the pic

My simple mind would call the cause of that failure as being 'the guy didn't wrap his corners'. You should never have a weld design such that the repeated loading is pulling the weld apart at weld start (or finish). When that tooth digs into the dirt, the cold-start of the weld feels the highest tear-apart loads, AND provides a great crack-start location. I would say a crack developed then propagated thru the weld.

That could be fixed by welding around a corner. And more than two ho-hum welds. I don't know what to say about higher heat except it could have help at the weld start, but you shouldn't count on such things at weld start. That tooth is a pretty extreme weld to receive such little forethought. Is this s a commercial unit or DIY teeth welded on? Looks to me like a 'failure to commit'. The guy didn't weld all the way around because he wanted to be able to cut/grind them off someday.

 

[chuck172]

You wish you could weld, I wish I never struck an arc. I was a Steam/fitter, pipe welder the last 40 years or so. I now have asbestosis, that's like having fishhooks laying in your lungs. Word has it that the old lincoln 6010 had asbestos and was quietly removed years ago. That rod was our bread and butter rod. All us old timers can remember when it ran smooth, then it didn't. The took out the asbestos.
Welding can hurt you if you do enough of it.

 

[Shield Arc]

Shows up real good in this test-plate pic. Down in the bottom of a 3/8" groove there can't much heat left with a 120v machine. Didn't this problem appear when welding 3/8" thick material with a 120v machine as an exhibition, a full 50% thicker than the machine's recommended capacity? That's an example but not good example because a newbie shouldn't be welding 50% thicker than the machine's rating. That's for experienced welders.

Sodo the plate is 3/8-inch thick. But the two plates were gapped, and even preheated a little. Without the backer plate it would be an open root weld. Basically no penetration at all. Now the picture I posted of the fillet weld, no bevel. That is just pure horse power to do that!

 

[aczlan]

OK thx James here's the pic

My simple mind would call the cause of that failure as being 'the guy didn't wrap his corners'. You should never have a weld design such that the repeated loading is pulling the weld apart at weld start (or finish). When that tooth digs into the dirt, the cold-start of the weld feels the highest tear-apart loads, AND provides a great crack-start location. I would say a crack developed then propagated thru the weld.

That could be fixed by welding around a corner. And more than two ho-hum welds. I don't know what to say about higher heat except it could have help at the weld start, but you shouldn't count on such things at weld start. That tooth is a pretty extreme weld to receive such little forethought. Is this s a commercial unit or DIY teeth welded on? Looks to me like a 'failure to commit'. The guy didn't weld all the way around because he wanted to be able to cut/grind them off someday.

More like not enough heat. As was mentioned in that thread, those welds should have left craters when they ripped out, not left a little discoloration on the bar.
Looking at:

If you're referring to fillet welds made with 70 series electrodes, the maximum allowable stress on the weld would obviously depend on the weld size, and can be calculated using a .928 multiplier. For example, to calculate the maximum stress for a 3/16 fillet weld, multiply 3 x .928, which equals 2.784 kips per inch. So, a 3/16 fillet is good for 2,784# per inch. If the weld is 8" long, the weld is good for 22.272 kips, or 22,272#. A 1/4 fillet is good for 3.712 kips per inch (4 x .928), a 5/16 fillet is good for 4.64 kips per inch (5 x .928), and so on. To answer part of your question, I don't think the method of inspection would change that. The weld may be subjected to tension, compression, bending, shear, or torsion forces, which would also factor in determining the allowable stresses on the welds, and would help determine the fillet size, or whether partial or complete penetration welds would be required to support the design criteria.

A pair of 1.5" 1/4" welds should hold up to over 10,000# of stress.

Here is a thread of someone doing a similar repair on a backhoe bucket:
Bucket teeth.

Aaron Z

 

[Sodo]

More like not enough heat. As was mentioned in that thread, those welds should have left craters when they ripped out, not left a little discoloration on the bar.

I kinda disagree that they "ripped out". My assessment is that the repeated stressing from the tooth digging in - cracked the weld at the weld "end", a few molecules at a time, starting at the rear (note where the crack had rusted for awhile). If it was a simple cold lap all the way, how did it survive long enough to get rust on the start of the crack. Plus that's a pretty darn "even" cold lap, a weld that might require a decently skilled welder. That tooth survived on there for awhile.

Are bucket "cutting edges" a harder carbon steel? If yes there could be some issues welding to it and a need for better weld planning than leaving a stressed weld start.

I didn't read the WW post, and I will (reading on phone now). Of course I could be wrong!

 

[aczlan]

I kinda disagree that they "ripped out". My assessment is that the repeated stressing from the tooth digging in - cracked the weld at the weld "end", a few molecules at a time, starting at the rear (note where the crack had rusted for awhile). If it was a simple cold lap all the way, how did it survive long enough to get rust on the start of the crack. Plus that's a pretty darn "even" cold lap, a weld that might require a decently skilled welder. That tooth survived on there for awhile.

From his threads on the subject (Cutting edge arrival on 25 Feb and teeth ripped off on the weekend of 26 Mar), the toothbar was just over a month old when the tooth ripped off. Not exactly what I would call "awhile" (probbaly one of the reasons WRLong sent him a new one out without much hassle).

Are bucket "cutting edges" a harder carbon steel? If yes there could be some issues welding to it and a need for better weld planning than leaving a stressed weld start.

Depends on the manufacturer. Some are a hardened steel, others are mild steel. The WRLong site for the Flat Bottom Toothbar ( Tooth Bars TB, STB, and ITB ) does not say what kind of steel they use for the "cutting edge" part of the toothbar.
They do specify that their "Wear Blade" ( Wear Blades WB and IWB ) is made from high carbon steel.

I didn't read the WW post, and I will (reading on phone now). Of course I could be wrong!

The gist of the thread was that a tooth came apart from the backhoe bucket (it had been abused unlike this one), and it was re-welded with a fillet weld (one bead down each side of the tooth, no wrap around the ends). Two years later, it was still holding strong.

Aaron Z

 

[Eric Salop]

You wish you could weld, I wish I never struck an arc. I was a Steam/fitter, pipe welder the last 40 years or so. I now have asbestosis, that's like having fishhooks laying in your lungs. Word has it that the old lincoln 6010 had asbestos and was quietly removed years ago. That rod was our bread and butter rod. All us old timers can remember when it ran smooth, then it didn't. The took out the asbestos.
Welding can hurt you if you do enough of it.

Real sorry to hear that. My first job, was with electrical switchgear. We used a lot of blue asbestos, drilling holes and blowing the dust out without masks. I have often wondered if I will stay lucky, or if it will catch up with me one day.

 

[Eric Salop]

Had a go at corner joints today. Not pretty, I think I may have been running it a little too hot and then loosing control when I then tried to move fast enough to prevent the pool running away. Rain put an end to my fun before I got anything like a decent joint. Time for me to watch the Steve Bliele tutorial again.