are smaller and rounder compared to the larger interdendritic shrink porosity seen in the as-cast regions of the weld repaired specimens. T e available data does not explain the apparent increased fatigue life for the half-weld specimens. Repair welding with the process
Fig. 7. Fatigue data for three types of weld repair specimens of E357-T6 sand castings shows the effect of the type of weld repair on fatigue life.
structure of the weld metal shows no dendritic structure. Even though the microstructures are distinctly diff erent, there appears to be little or no eff ect on tensile properties. As indicated earlier, the three types of specimens appear to behave diff erently
in regard to fatigue behavior. Typically, the porosity in the cast portion of the weld repair specimens was interdendritic (Fig. 10). T e smaller radii of curvature in these shapes generally have a greater negative eff ect on fatigue life. As seen in Figs. 11-12, the pores in the weld metal
parameters used for this study has no detrimental eff ects on tensile or fatigue properties of E357-T6 sand castings. T e study appears to support the principle that proper welding is appropriate for repairing or joining sand cast compo- nents to one another, though additional research is necessary for other alloys.
T is article is based on a paper (13-1210) published in AFS Transactions 2013.
Fig. 10. This micrograph shows the typical shape of porosity in E357-T6 sand castings.
Fig. 8. This micrograph shows the typical microstructure in E357-T6 cast (original) metal in weld repair specimens.
Fig. 9. The micrograph shows the typical microstructures of weld metal in E357-T6 weld repair specimens.
Table 2. Comparison of Tensile Test Statistics Showing Effect of Type of Weld Repair Specimen
Data Set No Weld Statistic Mean
Std. Dev High Low
Half Weld Mean
Std. Dev High Low
Full Weld Mean
Std. Dev High Low
Ultimate
Strength MPa 340.2
5.0
350.3 329.6 340.3 4.3
346.1 326.1 340.2 7.1
348.2 315.1
0.2% Yield Strength MPa
306.9 4.0
317.2
299.9 307.1 3.7
313.0 299.2 308.4 3.3
313.7 302.0 Elongation %
1.94 0.62 3.62 1.16
2.00 0.52 3.47 0.98 1.92
0.55 2.94 0.69
Fig. 12. This micrograph shows a compari- son of pore size and shape in weld metal and cast metal in the full-weld specimen.
Nov/Dec 2013 | METAL CASTING DESIGN & PURCHASING | 47
Fig. 11. This micrograph shows the compar- ison of pore size and shape in weld metal and cast metal in partial weld specimen.
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