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Welding Question

Discussion in 'Motor Graders' started by Queenslander, Sep 8, 2015.

  1. MX45

    MX45 Well-Known Member

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    G'day,

    While you are planning. I never had any joy in welding cast but I am only a backyard self taught. Last advices (not yet tested by me) I read about were to use 'stainless' wire with MIG. Advice I read was based on stainless not creating a carbon rich bond like other Mig wire which does not apparently work with cast. Of at least equal importance as senior members have mentioned is to 'peen' the weld immediately after the weld to take the contraction out of it on cooling, ie to stretch it. While the advice here is to keep the heat in it the advice I read about was to do short welds so it did not get too hot?

    Sorry the information is somewhat contrary apparently but maybe the better informed can make sense of this before you start to get to the bottom of it.

    Hate for you to start and have it fall off?

    I would for sure be tempted to have a mechanical fix to the inside of the ball to take pressure off the weld? Rod drilled right through? Welded at the ends? High tensile bolt recessed?

    I could have muddied the waters but better you are not stuck there doing a job twice,

    Regards, MX45
     
  2. Nige

    Nige Senior Member

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    I think maybe we are confusing "cast" with "cast"........ Cat castings are generally cast steel rather than something even like SG iron and so are reasonably easy to weld something to, provided you do the correct preheat, stres relief and post heat.

    Getting into the tehcnicalities of it regarding temperature you have "preheat temperature" which is the temperature to which you heat the workpiece before starting to weld and "maximum interpass temperature" which is the maximum temperature which should not be exceeded just after you've stopped welding and are preparing to remove slag and needle peen. If the preheat temperature is 150 then the maximum interpass temperature would be something like 165-170. That's the reason to keep each weld short and to weld only 90 degrees of circumference at a time. TBH with the relatively small size of this component and the small volume of weld metal being deposited I would be more worried about the temperature dropping below the preheat value rather than exceeding the maximum interpass temperature. An infra-red thermometer is a vital tool in a procedure like this one.
     
  3. Queenslander

    Queenslander Senior Member

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    Well, got it stuck back on this afternoon, may not be the perfect welding job, but I feel a whole lot more comfortable with it than our previous attempt twelve months ago.
    Was impressed with the 18TCs, nice to work with and easier to restrike than the 16s
    welding 1.jpg
    Welding 2.jpg
    Welding3.jpg
    Welding4.jpg
     
  4. Nige

    Nige Senior Member

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    That looks very good indeed, and grinding all the welds smooth will improve fatigue resistance no end. I would however suggest that you go back and grind out a few of the imperfections that are visible in the photos, each one of them is a potential stress-riser and crack initiation site. I've ringed a couple of them in red. Also I'd suggest after doing that to lay another bead right around the ball at the junction between the existing welding and the machine frame then re-grind. That extra bead will help smooth the radius of the weld/frame transition even more.

    I think the fact that you are happier with this repair than the one you did a year ago is the best indication that it's a good job.

    Welding3.png
     
    Last edited: Sep 13, 2015
  5. Scrub Puller

    Scrub Puller Senior Member

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    Yair . . .

    Good one Queenslander. As suggested by Nige though another couple of hours dabbing and grinding would be time well spent.

    Ideally you should end up with a smooth radius with no surface marks or imperfections . . . not always possible or practical.

    I used to be a rough YOUNG b*****d and thought this smooth radiused weld caper was bull-****e.

    The first big rakes we built to go on eights were a poor design with the two inch thick Assab teeth butt welded to the ten inch by ten inch bottom member. Within about a month they started shedding teeth in stumpy going . . . weld them on and they'd fall off again.

    The boss had a CIG welding consultant come out and he spaced the tooth away from the bottom member (rake off tractor and upside down) with three pieces of sixteenth gas welding wire. After some preheat he had me weld about a twelve pass unwoven fillet around the tooth with Multi's then he radiused the weld with coarse and then fine stones run with a flexible drive on a Villiers engine . . . this was before the days of angle grinders.

    Well, as mentioned it seemed like bull****e but those teeth never came off. The welding wire apparently introduced a bit of "give" into the joint to help prevent initial cracking and smoothing the welds particularly around the front of the tooth prevented the stress risers occurring. As the rake accumulated hours the welds became polished and the teeth and bottom member appeared to be a casting with no visible weld.

    The problem was fixed on later rakes by profiling the teeth with a substantial "tab" which extended six inches or so up the front of the bottom member.

    Since that experience I have evolved into a rough OLD b*****d who (somewhat) understands the importance of eliminating stress risers in the welds of components subject to shock and intermittent loads. (big grin)

    Cheers
     
  6. Shimmy1

    Shimmy1 Senior Member

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    I'm a decent welder, my first impression was I would have thought the base metal would be way more discolored if kept at 150C for the duration. Looks great otherwise.
     
  7. Queenslander

    Queenslander Senior Member

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    Certainly appreciate the advice fellas.
    The job only received minimal finish grinding because I was running out of daylight.
    Seems I didn't anticipate how much time I would spend walking from side to side around the grader to get access over the circle, must have covered a mile and a half.
    We do have a temp gun and we're able to keep it at 120+ for most of the time.
    I gave it a rub with a sanding disc, hence the shiny appearance.
    Cheers, Greg
     
  8. Nige

    Nige Senior Member

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    After you got it preheated did it stay at 120+ just with the heat of the welding or did you have to occasionally keep heating it in order to keep the temperature up..? My vote's on the latter due to the volume of weld being so small.

    Obviously if you ran out of daylight then that explains a lot. When you go back to start again you need to remember that you're now heating a lot more volume of metal because of the volume of weld you put in there so it will take longer to get the temperature up and if you're "dabbing & grinding" as Scrub puts it you'll put even less heat into the workpiece therefore your heating torch will become even more important.
     
  9. Queenslander

    Queenslander Senior Member

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    We had to put the torch on it half a dozen times.
    Kept my offsider hopping as well, swapping sides with the needle gun.
     
  10. Nige

    Nige Senior Member

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    Did it surprise you just how much you can pockmark a recently laid-down weld with a needle gun..?

    I'm pleased it went so well after you were obviously having second thoughts about the job part way through this discussion.
     
  11. Queenslander

    Queenslander Senior Member

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    Yes it did a little, turns a nice smooth weld into something that appears, on the surface, to be a little ordinary.
    Sure beats a chipping hammer for removing slag.
     
  12. Nige

    Nige Senior Member

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    That pockmarked look means it's done its job. That's why you grind the weld and smooth everything off afterwards, and not just to make it look pretty.

    I can't see why anyone would want to use a chipping hammer if you have a needle peening gun available, and the best part it is performing a two-fold function by removing the slag and stress-relieving at the same time.
     
  13. castirondude

    castirondude Member

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    I'm not a professional welder but I welded two of the cast steel ears on the boom of my Cat 235 excavator. It was 100+ outside and I gauged the metal about 1" deep with my plasma cutter so it was scorching hot. Then welded it with my MIG, going back and forth between the two sides to create a good bond. I used the 300A setting with 0.045 wire. This was about 8 years ago and it's still holding. So it is possible to weld cast steel with a MIG.
     
  14. ETMF 58 White

    ETMF 58 White Well-Known Member

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    About 25 years ago, we broke the ball off our old Cat No. 12 grader. This was about an early 60's model. My dad bought a replacement ball from Cat and while we were scratching our heads trying to figure out how to weld it, I noticed that there was an unused ball on the other side of the tilt mechanism. So we just unbolted the arm, swapped it to the other side, and have been using it ever since. (On the farm, not commercially.) I still have that brand new ball that Daddy bought. I wonder how much that Cat ball cost back then, and what the money that it cost would have grown to by now had it been invested wisely. On the other hand, the old grader is probably still worth what he paid for it used back in the early 70s. I could be wrong on that, though, I don't guess I've seen one of these sell in a long while.
     
  15. Nige

    Nige Senior Member

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    Queenslander, any update. How's the weld repair holding up..?
     
  16. Queenslander

    Queenslander Senior Member

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    It's holding up fine Nige.
    I went back and tidied it up as you suggested and it looks,almost, a professional job.
    I guess though, given that the original factory weld failed after twenty years, it will have a finite lifespan.
     
  17. Nige

    Nige Senior Member

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    Come on then, we need photos......!!

    The thing is that a lot of posters are coming to HEF these days with questions about repair welding and it's nice to be able to direct them to case studies showing how it should be done. Saves re-inventing the wheel.
     
  18. SidewinderGlenn

    SidewinderGlenn Well-Known Member

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    Welding question for ya Nige.
    Thinking about welding a little "C Hook" w/safety on to the H Link on my little KX 121-3 Kubota Excavator for lifting crap around the farm.
    Do I need to pre-heat the cast steel "H Link" & all the peening & such ... or can I just buzz it on there with some 7014 ?
    I don't really want to burn up the rubber dirt seals on the pins. If I need to pre-heat .. then I think I'll just weld the hook to a bucket.
    Thanks ~Glenn
     
  19. Nige

    Nige Senior Member

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    Best thing to do is start your own thread and post some pictures of the parts in question so that we don't get all messed up on this thread. You'll find on here that opinions are like a$$holes, everyone's got their own .......
     
  20. SidewinderGlenn

    SidewinderGlenn Well-Known Member

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    Sorry ... I'll get some pix & start a new thread.
    g