I recently purchased a few varieties of nickel strip for my spot welder which is a 12v car battery with a simple mosfet circuit. One type of metal sparks when I hit it with the Dremel, which leads me to believe it is steel, while the other does not spark, leading me to believe it is nickel. It was my understanding that nickel would weld better than steel however, the nickel ribbon produces significantly worse (dirtier, burnt, weaker) welds and requires much more pulse time whereas the steel produces strong welds at a low pulse time. Why does steel strip weld better and at a lower pulse time than nickel strip?