Welding SS to Mild steel - question

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I’m learning as I go here, I was just curious as to why this happenedI was trying to weld a ½” stainless steel bolt to some mild steel, I know you would normally need a different shielding gas than the 25/75 arg/co2 but I figured I wouldn’t need much strength for what I was doing.Using my simple 115 v mig set at a high setting and fast wire speed I gave it a zap to tack the bolt in place…it just about melted the bolt away.  Why would that happen? I thought SS was supposed to be stronger than mild steel?Thanks.
Reply:just how thick is this mild steel your attempting to weld the ss bolt to?hi setting?fast wire speed?try a lower setting and feed rate and go from the mild to the stainless..I gave it a zap to tack the bolt in place
Reply:Thanks ZAP, I'm welding it to 1/8" plate.I have a Lincoln weld pack 100 - 88amp @ 20% duty cycle, so I can't tell you too much about the settings. I don't get good penetration on 1/8" steel with out multiple passes and beveled edges.I was really just trying to tack the stainless steel bolt in place. I wasn't looking for any penetration, so I was surprised when the stainless melted.Bolts are from Home hardware, maybe it isn't stainless as advertised.I'm really just trying to learn more about metal. Should stainless melt at lower temps than mild steel, or is it that the bolt sucked is so small and sucked up all of the heat?Thanks.
Reply:Yes, the stainless will typically have a lower melting point.What makes this weld difficult at times is that the arc can be pulled towards the mild steel side, since it is more magnetic.  The arc may want to erode away the mild steel side and make it hard to avoid undercut on that side.
Reply:Sd try welding with 309L it is a flux core ss Wire and welds great with 75/25.