yes steel ? or maybe nickel
the DIY people don't use 60v and don't use carbon rods
they use stiff wire heavy gauge solid 'wire' electrode
contact points are side by side
its not one weld point, their systems make (2) dots on the strip
where it welds to the battery
https://www.youtube.com/watch?v=o1NFbchHeM8&ytbChannel=nullupgraded version of welder same person(1) 12v battery , solenoid, push button monetary switch
https://www.google.com/search?q=spot+welding+18650+lithium+batteries&num=20&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjuy8aDl5jdAhXHc94KHQgxDW8Q_AUICygC&biw=1258&bih=530
