Acceptable weld integrity criteria vary greatly among manufacturers and world regions. Each AHSS user needs to establish their own weld acceptance criteria and the characteristics of AHSS resistance spot welds. AHSS spot weld strength is higher than that of the mild steel for a given button size (See figure in Process Simulation). It is important to note that partial buttons (plugs) or interfacial fractures do not necessarily characterize a failed spot weld in AHSS. Interfacial fractures may be typical of smaller weld sizes in Mild steel or in all weld sizes in AHSS. Reference is made to the new Specification AWS/ANSI D8.1 Weld Quality Acceptance (Figures 1 through 4).
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Figure 1: Load-bearing capacity of spot welds on various cold-rolled steelsL-2 (Steel type, grade, and any coatings are indicated on the bars.).
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Figure 2: Representative minimum shear tension strength values for Group 3 steels.A-13
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Figure 3: Representative minimum shear tension strength values for Group 4 steels.A-13
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Figure 4: Minimum Cross-Tension Strength (CTS) values for Group 2, 3, and 4 steels.A-13