Stabilizer pad 580se material

anybody know what metal the stabilizer pads on a 580se are? Mine had a crack, so I mig welded the crack after cutting a groove along the crack. The weld looks awful and without ANY sort of use, it cracked right through the middle again. My usual welds look a lot better and don’t crack after sitting outside for two days
I did not preheat or let it cool slowly.
Thanks in advance

Stabilizer pad 580se material