I had two broken springs in my ‘63 seat that I was able to weld back together. The trick was getting the pieces lined up and also a good ground connection (flux wire feed welding). I removed the springs from the seat and worked them on my steel table using magnets to hold and align the pieces together. I stretched and compressed them a fair amount and the welds have held. I love a challenge, especially one where I have no clue whether it’s possible or not

, must have skipped that lesson in elementary school.
on edit: looks like at least one of those springs is missing a section, not just broken. If so that’ll have to be replaced. Google upholstery coil springs, there out there just need to match height, coil diameter and wire diameter as best as possible. Good luck.