Section 5 of ASTM B344 covers the physical requirements for nickel-chromium and nickel-chromium-iron alloy wire for electrical heating elements. The material must be thoroughly and uniformly annealed.
Wire of size 0.0035 inch (No. 39 AWG) and larger must meet a minimum elongation of 20% in a 10-inch gauge length. Wire from 0.0031 inch to 0.002 inch (Nos. 40 to 44 AWG) must meet 10% minimum elongation.
These elongation requirements ensure the heating element wire has adequate ductility for coiling and forming during manufacture of heating elements.