I Have a Case Case 680 T/L/B with a crack in the saddle that the boom hoist cylinder rod eye attaches to. I need advise as to how to do the repair properly. I have a Hobart Stickmate ac/dc welder. I have done a lot of stick welding through the years but, never on a backhoe boom that is exposed to the stresses that they are put through.The previous owner had done a really nasty looking repair to it that was doomed to fail which it did. I have partially ground off some of the old weld to give a better view of the crack. It doesn't appear to have extended all the way to each end of the old repair. Should I grind all the old weld off completely to the parent metal and vee it out properly ? In regards to the welding procedure should I preheat the weld area to drive out any moisture and if so how hot ? I have an infrared thermometer. 7018 for the root pass and the entire weld ? Should I peen each pass with a chipping hammer to relieve stress ? The third photo on the right is the vertical part of the old repair.
Sounds to me like you have it figured out just fine. 7018 for all equipment welds unless there is some kind of special metal or application.
I'd grind it down smooth, then follow the crack, with a plasma cutter, and cut it out that way, and then weld it with 7018...
The good part is you caught it while it's just cracked & not spread open or busted clean off . Yeah , gouge out as needed buy whatever means , torch , grinder , etc . Pre heat casting boss & boom a little with the torch & then go at it with the 7018's On the pre heat I do it about the same as cooking a turkey in the oven . Around 425 F or to where it feels damn uncomfortable to lay hand on it . Had a similar deal on a dozer blade . Crack beside a pin boss , not a big deal we just don't want it to get any bigger . http://www.heavytruckforums.com/showthread.php?51-Fwd-Trucks&p=2352&viewfull=1#post2352 Good luck with the repair .
Is this not ductile iron? I believe many Case booms are labeled ductile, do not weld. Willie
99% sure it's ductile iron. Welding is similar to cast iron requiring high nickel electrodes, pre and post heating, and maybe some praying. Depending on how it was welded before it may start cracking on the edges heat affected zone after you repair it. Considering the cost of a replacement casting, there's no harm in trying, but it's not just preheat and burn some 7018 either.
This boom isn't cast, only the "fitting". It could be cast steel, not cast or ductile iron.
Yair . . . Actually I thought the few inches of vertical up shown in the O/P's #1 post displayed reasonable technique. It's hard to tell from the pictures but I find it odd the crack has appeared through what is probably a cast steel fitting rather than through the weld which attaches it to the boom. The material appears very weldable and, in the first instance I would vee it out and re-weld with some over build (reinforce) trying to eliminate any undercut at the ends of the weave. Grind it smooth leaving a build up in the area of the crack and then polish with (say) a 120 grit pad eliminating any imperfections along the line of the crack and sides of the weave. Put it back into service and watch it. If I cracks again it will be necessary to vee out and re-weld flush, make some patterns and plate it with 1/2". Cheers.
I welded a cracked boom on an old 1088 Case excavator. Not the plate steel but the fitting. I was warned against welding it but it was junk without trying. It was welded at the factory so why not. I gouged out the entire length and depth of the crack, added a little heat and welded with 7018. It was all overhead. That has to be over 10 years and 3000 hours ago. it's still good to go.
As usual on HEF I have received a lot of awesome advice and encouragement. Hopefully sometime this week I will put that information to use. My thanks to all that responded.
Since it's a stress point I'd peen each pass well with an air chipping hammer or needle gun to relieve HAZ(heat affected zone) stress. Mike
I was going to use a plain ole chipping hammer but your suggestion will save me a lot work. Thanks