I took the opportunity to measure the amp draw of a 200 amp welder, on a 50 Amp 240 volt circuit, set at the proper welding setting, while a seasoned welder used 1/8" stick and joined 1/4" steel , and got 18 amps.
Based on 50 amps at 120 volts or 50 amps at 240 volts, I suggest #2 aluminum will work fine.
This can be 3-#2 Al with XHHW insulation and 1-#6 AL XHHW Green.
Min conduit will be 1-1/4". I suggest 2" PVC Sch 40 for this length.
The panel in the garage will need a main breaker, ground rod connected to the equipment ground bar for bare or green grounds only, and do not bond the neutral bar to ground.