This arm broke and I'm trying to figure out how to replace the part. But it seems like the bar above is welded in and can't be removed. Is there any way to replace this or will I have to get it welded? Seems strange to have such an integral part of the mower be impossible to replace without such drastic measures.
Looks like poor weld fusion progressively failed until the final big failure. Notice how almost all of that pretty weld bead is on the arm? The bar is a YUGE heat sink so all the heat went into the arm, not the bar. I'd just have it welded by someone who knows how to weld. A proper repair will probably last a very long time. Use some remnants of the old joint to locate the arm so your deck isnt wonky after the repair. But where the new weld structure will go I'd notch a generous "V" for the new weld bead. If you find a good welder he'll know this. The hardest part of your repair will be finding a competent welder who will take the job.
Now if I was doing this repair, I would make up a pair of brace plates to go front & back
Naturally the back one can only have a slot cut to fit over lifting rod
Tack the original back in place then grind out the welds to a deep V all the way round
Weld a full circle , trying not to overheat the end of the shaft
Put the two brace plates over the lift arm and weld them full length on their edges so you now have a lift arm 2 to 3 times as thick
Finally weld the outer to the end of the shaft
Last bit is apply a generous coating of cold gal paint by brush
It is of course a lot easier if the other end unbolts so the shaft can be pushed out
And I use old blades to make stuff like this from because they are a particularly strong grade of steel .
it's not always but often related to mowing with the deck riding the ground, e.g., mowing too low, rough terrain, getting up against fences/curbs/sidewalks, sometimes worn out/unbalance blades cause vibration which then contributes as well
often people blame the weld and even properly welded, there is always going to be a heat affected zone, where the material is weakened a little near the weld. This is even apparent on the factory setup. They do what they can within the constraints of manufacturing to minimize the HAZ but they can't totally eliminate it short of heat treatment-which adds significant $$$ to the cost of the mower, which then makes it more expensive than the Kubota or Deere counterparts, of which they were competing with.