Repairing cracked weld excavator blade

[sandfs]

Is it actually necessary to use a hardened steel edge for the replacement blade or would 1/2" mild steel suffice?

That's pretty subjective, it all depends on how much you are going to use it and long you want it to last. If you do go with mild steel I'd just stitch it on there to make it easier for the next round of replacement.

 

[searcyfarms]

are you using an AC arc or DC arc? just curious - cant go wrong with 6011 pretty versatile and great for rusty farm stuff - I like 7014 on my Lincoln 225 they lay a nicer bead but that seems to be machine driven not the fault of the stick my 225 wont even keep a 7018 AC rod lit, my 225 is OLD and does not have the DC option.

glad you got it fixed and if you ground it out good first and put some real heat to it/penetration it should hold well. Im just guessing but from the looks of that thickness you would have been in the 175amp range

 

[liberty2701]

I have an a/c welder. I preheated slightly and used 135 amps.

 

[MinnesotaDaveChalmers]

Your preheating question is actually a pretty complex subject largely depending on the type and thickness of the material as well as other variables.

But for normal daily at-home use it can be summarized by thickness.
The thicker the metal is, the more preheating it needs so that the weld can cool slower (table in D1.1).
Thick material is an excellent heat sink. So without preheat the weld can cool too quickly.

Preheat should extend out from the weld approximately 3" both sides.

Another rule of thumb, use at least "room temp" of about 70 degrees for the minimum even for thinner material.

After the rule of thumb type stuff, the remaining technical info is interesting and can be argued and reinterpreted for days

 

[searcyfarms]

wow I have never heard of preheating metal at all even in my welding class but it was only in h/s many many moons ago - never even crossed my mind actually - I did know that metal can be more brittle in the winter so I am more careful when doing things in that regard - as for my statement of welding I would say 90% of my welding occurs at or above 50 degrees up to 100+ went its sitting out in the hot sun in the summer - there are occasions when I break things and have to weld when its colder and have over the years but I have not noticed any ill effects or other abnormal breakages or failures of items I have welded being it 20 or 100 when I performed the weld. I guess I have been lucky!!!

I will say this, I tend to weld things hot and I also tend to add more support/bracing when something fails and it gets reengineered ;-)

 

[radios1]

hardface rod would be best for the blade, it'll wear longer, that's what it's made for.. I don't think there's a number for it, just various trade names, but it's designed for blades and other things that will get abraded.. regular rods are not very abrasion resistant at all, they are relatively soft.. you just need a bead along the cutting edge..

 

[Gary Fowler]

I really wouldn't waste my time putting on a mild steel "blade" since it will wear out really fast. If you really plan to keep that equipment a long time and use it frequently, then bite the bullet and buy a replacement blade to replace the one on it now. The hardened steel blade should be welded with not less than a 7018 and preferably with 80xx or 90xx grade electrode. I would never use 60xx rods on hardened steel due to possibility of weld cracking since the weld metal is so brittle. Also use a bit of preheat (150F) or so that if feels hot to the hand if you don't have way to measure the temperature.

 

[CincyFlyer]

Everyone is talking about "hardened" steel, when you want tough and abrasion resistant, rather than hard and brittle. I still have ten pounds of Stellite that I will weld on high-wear areas.

 

[liberty2701]

Could I just purchase a 1/2" snow plow blade which I believe are very hard and weld it on? They seem readily available here. Based on my pictures above, how far below should I drop the new blade below the old? Would stitch welding suffice or weld a full bead along the whole blade?

 

[chrismac]

Can you explain why 7018 and no preheat is required. I thought the weld needed some flexibility being it was hardened steel on the front of the blade. Thanks

I think, a bit of an educated guess that the material is not too think and does not warrant a preheat, by all means preheat if you like it will do no harm, it will make the rods run smoother while its hot but by time you get along that blade the temp will be well down unless you have someone else with the torch keeping it warm for you,