Abstract
Repair welding is an important remediation process for castings with slight defects. In this paper, the tensile behaviors of the QT400-18 nodular cast iron with different repair welding sizes were experimentally analyzed. Specimens with different diameters of the filler region were prepared by the same welding process. The fracture initiated in the filler region under uniaxial tensile loading. The modulus, strength, and ductility decreased with the weld diameter increase. The postyield hardening phenomenon was not observed in the repaired specimen. The repair region ratio was defined as the proportion of the repair welding area to the cross-sectional area of the structure. The effective modulus of the repaired specimens decreased with the repair region ratio increase, and the relationship between them was fitted by a negative exponential function. The repair welding region was treated as an inclusion in the matrix of castings, and the volume fraction of inclusion was applied to characterize the repair welding size. Based on the theories of Eshelby tensor and Mori–Tanaka equivalent method, a method for estimating macroscopic effective modulus of repair welding castings was established. The theoretical solutions were in good agreement with the experimental results. The method will be helpful in estimating the safe service limit of repair welded castings.
Highlights
Some foundry minor defects, such as gas pores, shrinkage porosity, and misrun, exist in large castings more or less [1,2,3]
Nascimento and Voorwald [19] carried out the fatigue crack growth tests in the base material, heat-affected zone, and filler metal of tungsten inert gas (TIG) repair welding, and the results indicated that the TIG method increased the fracture resistance in the weld metal but decreased it in the HAZ after repair and that microhardness and microstructural changes played important roles in the crack propagation of repair welded casting
The whole portion of shrinkage porosity was hollowed out from the base material manually, and the repair welding process was carried out to fill in the hollowed parts
Summary
Some foundry minor defects, such as gas pores, shrinkage porosity, and misrun, exist in large castings more or less [1,2,3]. E equivalent mechanical behaviors of repair welds have always been a research focus in foundry industry For some materials, such as cast Ti-6Al-4V and Titanium castings, minor weld repair was demonstrated acceptable for creep [7, 8], and fatigue cracks initiated from the base metal in the high-cycle fatigue load case [9, 10]. Nascimento and Voorwald [19] carried out the fatigue crack growth tests in the base material, heat-affected zone, and filler metal of tungsten inert gas (TIG) repair welding, and the results indicated that the TIG method increased the fracture resistance in the weld metal but decreased it in the HAZ after repair and that microhardness and microstructural changes played important roles in the crack propagation of repair welded casting. A prediction method of effective modulus for repair welded casting was proposed. is work is helpful to validate repair welded casting structures
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