Nihonweld NT-AL 4043/NM-AL 4043 description: NT-AL4 (4043) is more commonly referred to as Al Si 5 as it is a 5% silicon aluminum filler metal that is available in spools or cut lengths for MIG or TIG processes. NT-AL4 (4043) has a melting range of 1065-1170F and a density of 0.097 lbs/cubic inch. The post anodizing color tint is gray.