Welding dipper and boom

Drilling a hole at each end of the crack is a must. Another thing that will help in off position is to weld reverse polarity. 7018 rod works well either way. In reverse polarity it will help suck the weld in a bit better than straight polarity.

I know I already posted but.....

normally my guy will take a torch gouge it out and then blow the crack completely throug the steel, you will be able to chase the crack when you do this, and then either seal up the back with a mig or 6011 and then pour the 1/16th" fluxcore in like candle wax at about 300 amp....Im sure someone will tell me its wrong but NONE of his welds have ever broke

Pj

Jam did a beautiful job welding up that stick. However I would like to point out something I learned in the Lincoln welding handbook, (an inexpensive book just full of practical welding advice that every welder should read). And I don't work for Lincoln, I have both red and blue welders in my shop.

In the book they tell about gooseneck type float trailers that were prone to cracking in the bend area. Owners took to welding gusset plates inside the web of the beam here to repair/prevent cracking. Over time manufacturers began doing the same due to customer demand, I am sure everyone has seen goosenecks reinforced this way.

Anyway an engineer analysed the problem and found that a small reinforcement on the bottom flange along the underside of the curve was all that was necessary, as the cracks were starting there and the web and top flange were in compression and not prone to cracking. The side gusset plates probably helped somewhat but did not completely eliminate the problem and added hundreds of pounds of extra weight to the trailer.

From the pictures it appears the crack started where the bushing was welded into the boom, probably cracked next to the weld. A small reinforcement on top of the bushing would probably prevent this from happening again as well or better than the gusset plates along the side of the boom.

Sorry, I misquoted Jams post, he posted a link to another site and a post by fchesser78 on welding web, he didn't weld it himself.

As for the welding rod question to weld a boom or dipper, 7018 is what you want. It needs to be kept in an oven at over 300 deg F IIRC. If it is exposed to the atmosphere and humidity once its sealed container is opened, it needs to be dried at higher temp before it is usable. Remove only enough rod so that it can be used before it cools.

All these procedures as well as pre-heat and post-heat apply to high carbon, high strength steels. If you are sure the steel is only mild steel then 7018 is not required. However all the welding on equipment I have seen or done has been with xx18 type rod and the above procedures. The reason is that hydrogen from the humidity in the air will be entrapped in the steel when the weld is made. This hydrogen causes the steel to be brittle and for cracks to form.

Just an aside, I find threads like that busted boom repair a great training tool. A picture is worth a thousand words when it comes to telling young operators to TAKE IT EASY, BE GENTLE, THE MACHINE IS NOT INDESTRUCTIBLE.

It really helps to get the point across.

v-weld

Use an air arc or grinder to create a V. Be sure to clean the area well with a wire wheel before you start welding. Make your first pass with 3/32" 7018. Use 1/8" 7018 for subsequent passes.Clean the weld between each pass & keep your heat up.

Scott
Fab Manger
Welders360.com