No, spelter is not magnetic. Spelter is simply a synonym for zinc and is similar to copper or brass as well.

Composition of Spelter is - Copper- 90%, Zinc- 10%

Spelter, sometimes known as zinc, is used to fuse metals with a higher melting point. The actual melting point of spelter is 787.15 degrees Fahrenheit.

ZnO + C gives Zn ( impure spelter)+ CO

Zinc oxide(Zincite is reduced by carbon which takes away Oxide from to give impure Spelter(Zn) and CO.

with solder