1.1.1 This document covers general and dimensional data for various types of weld studs having one or more integrally formed projections under or on top of the head suitable for resistance welding.
1.1.2 The inclusion of dimensional data in this standard is not intended to imply that only the products described are commercially available. Consumers are requested to consult with manufacturers concerning other designs and sizes.
1.1.3 When a weld stud is welded to another material, the heat-affected zones are momentarily heated to a red heat. This momentary heating is above the transformation temperature of the steel, similar to when the material was hardened. The large mass of surrounding cold material is sufficient to cool the heated area quickly, as in quenching a part in oil or water. In steel of 1020 carbon content or higher, this can produce a very brittle area on the weld stud of untempered martensite, if the process is not properly controlled.
1.1.4 If the welded parts are placed in a container after welding, varying degrees of brittleness can be encountered. The first parts into the container cool quickly, and can become brittle. Subsequent parts are exposed to some heat from other parts already in the container. By the time the container is filled near capacity, the last parts in may experience sufficient heat enabling them to cool slower from the welding temperature. This could approach a normalized or even an annealed condition and would cause the last parts in the container to be more ductile than the first ones.
1.1.5 The higher the carbon content (1020 and above) in the steel, the greater the potential for brittle welds. High temperature stress relief up to 1500°F is recommended. If the weld stud must be heat treated, a hardness range of RC 24 to 34 is recommended with a minimum tempering temperature of 650°F. Most automotive specifications limit the material used for weld studs to SAE 1005, 1008, 1010 to 1018, 1020 or 1022 as found in SAE J403 or IFI-140 as 1022A or 1022B.