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Reflooring dump bed

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  • Reflooring dump bed

    Hey guys I’m new here and need some advice. I have a customer ordering some ar-450 3/16” plate to lay in his dump truck floor and wants me to weld it in. I’d like some tips if there are any should I just stitch weld or try to weld solid? Does it need a preheat being only 3/16”? I’ve never welded hardened plate I’ve got a pipe and some structural background thanks in advance for any replies

  • #2
    I’ve been doing a good bit of work for a dump truck outfit here, but most of their stuff is aluminum. I’ll say this for sure, the truck he has that don’t have the seams welded in full end up in terrible shape. Dirt, water and muck get between the old floor and the new one and it makes a heck of a mess. In fact, he bought a couple used trucks a few months ago and that was the exact issue we ran into. Had a lot to cut out of those two. That goes for the plastic liners as well. Those that don’t have the hold downs welded the full length have become a thorn in my side. Takes a good few hours to get the junk out and pulled flat enough to weld it up. Their last mechanic tried stitch welding and then filling the gaps with silicone. That probably looked good for about a week. Now it’s just more I have to remove before I make the repairs.


    • #3
      Try calling Associated Steel, they sell AR plate and can probably answer your questions.
      West coast of Florida


      • #4
        Something low hydrogen, E7018 as an example would work. Preheating maybe if it's cold out and your worry is rapid cooling causing contraction cracking and brittleness, using GMAW solid wire for instance.
        As for welding all seams, yup, for the reasons mentioned. Give some thought to your welding sequence, stop starts and intersections.


        • #5
          Weld it up solid!
          A FEW OF MY TOYS !!!

          MX Linux

          Miller Roughneck 2E
          Lincoln Weldpak 100
          Gianttech Arc 200
          Victor O/A


          • #6
            I would strongly consider dual shield. That will zip it up in no time.


            • #7
              I've done a lot of those with dual shield esab wire...solid weld...pre peen...usually the prep is the only hard part....good answers so far


              • #8
                This is a Put it on paper job.
                Customer must be advised in writing that AR 450 is very likely to crack and fail in his aplication, and weld cracking is expected. Customer don't sign off, let somebody else weld it because when it fails the truck owner will be badmouthing you all over town.

                Drilling, Machining, Punching Impact AR450 plate is more challenging to drill, machine, and punch compared to as-rolled steels (grade 50-80K) due to higher hardness levels, but can be successfully accomplished with appropriate tools. Carbide tipped tools are recommended, but high speed steel tools can be used. Slightly lower speeds and higher pressures compared to as-rolled grades are recommended for proper chip formation. Bending Free bending should be performed utilizing maximum allowable bend radius to prevent cracking. Impact AR450 plates 0.313” (7.96 mm) thick and less can be bent using miniumum radius of 4T. Larger bend radius is recommended for thicker plates.

                Post-Delivery Heating Impact AR450 plate achieves its properties through quenching and tempering processes.

                Heating in fabrication (such as post-weld stress relieving) or in service must not exceed 400 Fahrenheit without risk of lowering the strength and hardness of the material.

                Welding Impact AR450 can be welded by conventional processes such as SMAW, SAW and GMAW provided that the weld procedures used are suitable for this grade and design of the welded structure.
                Proper weld procedures should include the following:
                1. Low Hydrogen conditions must be used.
                2. Excessive preheating (>350 F) should be avoided to prevent softening.
                3. Slow cooling rates should be avoided to prevent low toughness in the HAZ.


                • #9
                  All of what Franz said and better put spreaders in if doing a complete overlay of the floor.


                  • #10
                    All of that above is a direct cut and paste from commercial metals’ website:


                    Check it out for yourself.

                    Anyone with a Lincoln “metals and how to weld them” book handy? Be interested in what that book says about this grade of steel.

                    Any particular reason AR450 is spec’d out for this job?


                    • #11
                      Never mind, five second search reveals it’s a common grade for this application.

                      Just one link to look at if you’re interested:


                      How much you figure a dump box made out of
                      Hastalloy X would cost? About half the total amount of rice in China?


                      • #12
                        And one more link, Zig, I think you’ll find helpful:



                        • #13
                          Thanks for the replies I can definitely see why it should be welded solid. I’ll be using 7018 and I was thinking about preheat to slow the cooling rate but looking at what Franz posted it says to avoid slow cooling rates


                          • #14
                            It's been a while since I dabbled in this, but from what I recall, this is some where between adding a layer of harder material to resist deformation/puncture from dropped boulders and rock, as it is adding material thickness to absorb the force of them dropping?
                            After re-reading my advice and some that followed, I took note of a couple points in Franz's reply.
                            design of the welded structure
                            Slow cooling rates should be avoided to prevent low toughness in the HAZ
                            With consideration to how this is to be accomplished, Is it a new box or one beat up with surface issues? Are the joints be staggered or aligned? What process is to be used, what prep is to be done, what condition is the box presently in?

                            Do you think it's necessary to tag the top sheet from the bottom? Random plug welds for instance? Slot and fillet? Or just leave it free underneigth?
                            The cooling rate thing. Any material quenched and tempered will change when subjected to heating. I found the statement to be some what miss leading in it's boldness. Is it suggesting no excessive current possibly? Excessive voltages? Or off handedly saying use short circuit GMAW because it going to cool the quickest?

                            Ryan's post say's different? Who do you believe just from what's written unless you do your homework too understand what occurs and why?
                            Also what if any concern is you might have regarding cold weather impact properties and how that fits into the mix?

                            Welding AR plate to itself or any structure with dissimilar and softer or lower-strength steel poses particular challenges, the biggest of which is preventing cracking in the weld metal or heat-affected zone (HAZ) of the AR plate.
                            Rapid cooling
                            , highly restrained joints, and/or excessive hydrogen in the weld metal or filler metals are among the biggest culprits of cracking. To help, below are seven tips to help maximize quality when welding AR plates."

                            Read lots and remember to think.


                            • #15
                              It’s a dump truck box, so it won’t be one solid piece anyway, but that’s a good consideration the plug welding idea. By all accounts, this exact thing is done all the time, so it’s probably nothing to over think. I have welded in new bottoms in garbage trucks on a few occasions. Honestly I don’t know what the material was as it was a direct replacement tub bottom direct from the manufacturer. The requirement was to plug weld within certain distances from the edges and from each bend, but they also had to hit crossmembers of the frame. Those tubs were also 3/16” at least, might have been 1/4”. Those garbage trucks take a serious beating. Anyway, the plug holes could be either cut, drilled or burned. There was nothing in the engineering specs about pre or post heating. The preferred alloy was 7018, but they allowed any LH rod to be used.

                              So if you’re overlaying an old bottom, maybe consider plug welding a few spots to help keep it flat-ish. That was one big difference between this and the garbage truck bottoms, which were a cut out and remove the old one and replace it with a new one.

                              Welding on garbage trucks is one of my least favorite things to weld on, in case anyone was wondering.