Pooh & A Welding Review

 

From Here

If that's the path you choose, and since all of us don't have a dozer around the house, maybe pick up an old Suburban as your starting point. 

Maybe do a Craig's List or eBay search for one of these from Napco, Industries. I looked them up to see if they were still in business, and sure enough they are and they do some serious work on serious machines. The computer told me the website wasn't secure, which I found surprising from a security company doing business with the military. So beware if you decide to check out the site.

While I'm not interested in building a killdozer, I'm more of a bunker guy myself, the Pooh cartoon got me thinking about some welding metallurgy. The above video deals with the subject of failures, primarily as a result of material not suited for the job. There have been numerous failures as a result of poor weld quality as well, both of which could lead to catastrophic failure on your killdozer. It's not too tough to acquire decent steel plate, A36 for example. Basically, it's steel which is similar to 1020 plain carbon steel. Most of the time any electrode or common process is acceptable as long as the electrode is in the 70,000 tensile range. I've never welded on any armor plate but I have welded on a lot of abrasion resistant plate, as well as some high carbon stuff. So then, if you're doing your plate shopping at the scrapyard and doesn't come with certs, how do you know what it is that you've got, and what should your weld procedure be?

There are several sophisticated ways of accurately determining what the material is, but what about the guy working in a repair shop or in the garage at home? One of the first things you need to look at is how the part is used? If it's used as part of a lifting device or where part failure could mean death or destruction, the answer is always "Sorry, I can't help you." Same answer for pressure vessels. That's why weld shops always have trouble buying liability insurance. Having a welding machine doesn't automatically make you a qualified welder. Likewise, reading the rest of this is not necessarily going to make you qualified to make some metallurgical decisions that should best be left up to a welding technician or engineer. Consider yourself warned. 

The first step to determine weldability for the average Joe, is a spark test. An internet search will come up with lots of info and color pictures that will help you determine if it's steel, rather than some form of iron, as well as the carbon content. Guys who are really good at spark testing are out there. I'm not one of them, however. But I'm good enough at it to give me a decent idea of the material - I can at least recognize a high carbon sprig when I see one.

If I determine that it's a medium or high carbon steel and I'm going to stick weld it, I know that I have to use a low hydrogen type electrode such as a E-7018. The low hydrogen group will run up to the 120,000 pound tensile range. It's rare that you come across the need for an E-12018, and if you do, you damn sure better know what you're doing because if you don't, I can guarantee the weld will crack. Sometimes you can even see the crack following along behind the puddle while you're welding. No bueno!

Next step is to determine if it needs to be preheated, post heated or both. One of the ways to determine if preheat is needed is a clip test. That's done by welding a small piece of the material to the base plate on one side only. You then whack the clip towards the unwelded side. If the piece comes off through the middle of the weld, you're probably good to go. If the weld peels out of the base metal, preheat is necessary. How much? Experience helps here, but that's no guarantee.

Welding repair work can be pretty tricky and it's hard to find a place to learn all of what's required. I was lucky to work in a couple of shops that did a variety of work, so I was able to learn a few things along the way. One of the hardest things I had to learn was when to bail out before I got in over my head - still have a little trouble with that. If you're a little short on experience, you might want to consider a course or two at your local community college before welding panels and mixing cement.