FIGURE 9.4 Strength near a weld.

D1.2 Structural Welding Code—Aluminum [21] and the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section IX [7]. They are based on the most common type of welding (gas-shielded arc, discussed next), and as long as a recommended filler alloy is used, they are independent of filler. Yield strengths for welded material are also given in the Aluminum Association's Aluminum Design Manual [2], but they must be multiplied by 0.75 to obtain the yield strength of the weld-affected metal because the association's yield strengths are based on a 10-in. (250-mm) long gage length, and only about 2 in. (50 mm) of that length is heat-affected metal.

Fillet weld shear strengths are a function of the filler used; minimum shear strengths for the popular filler alloys are given in Table 9.27. Fillet welds transverse (perpendicular) to the direction of force are generally stronger than fillet welds longitudinal (parallel) to the direction of force. This is because transverse welds are in a state of combined shear and tension and longitudinal welds are in shear, and tension strength is greater than shear strength.

Heat-treatable base metal alloys welded with heat-treatable fillers can be heat treated after welding to recover strength lost by heat of welding. This postweld heat treatment can be a solution heat treatment and aging or just aging (see While solution heat-treating and aging will recover more strength than aging alone, the rapid quenching required in solution heat-treating can cause distortion of the weldment because of the residual stresses that are introduced. Natural aging will also recover some of the strength; the period of time required is a function of the alloy. The fillet weld strengths for 4043 and 4643 in Table 9.27 are based on 2-3 months of natural aging.

TABLE 9.26 Minimum Strengths of Welded Aluminum Alloys


Tensile Yield

Thickness Ultimate Strength

Alloy Product (in.) Strength (ksi) (ksi)a

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