Abstract
This article examines the weldability of ductile cast iron when the root weld is applied with a tungsten inert gas (TIG) welding process employing an Inconel 625 source rod, and when the filler welds are applied with electrodes coated with 97.6% Ni. The welds were performed on ductile cast iron specimen test plates sized 300 mm × 90 mm × 10 mm with edges tapered at angles of 60°. The plates were subjected to two heat treatments. This article analyzes the influence on weldability of the various types of electrodes and the effect of preheat treatments. Finally, a microstructure analysis is made of the material next to the weld in the metal-weld interface and in the weld itself. The microstructure produced is correlated with the strength of the welds. We treat an alloy with 97.6% Ni, which prevents the formation of carbides. With a heat treatment at 900 °C and 97.6% Ni, there is a dissolution of all carbides, forming nodules in ferritic matrix graphite.
Highlights
Castings such as steel are basically alloys of iron, carbon, and silicon that favor the formation of graphite, and carbon content may vary between 2% and 6.67%
This study examined the weldability of ductile cast iron when the root weld is applied with a tungsten inert gas (TIG) welding process employing an Inconel 625 source rod, and when the filler welds are applied with electrodes coated with 97.6% Ni
Graphite appears as nodules in ductile cast iron because of the presence of small amounts of magnesium [1] retained by the iron and distributed evenly throughout the matrix
Summary
Castings such as steel are basically alloys of iron, carbon, and silicon that favor the formation of graphite, and carbon content may vary between 2% and 6.67%. Carbon percentages of up to about 4% are often used commercially because a large percentage of carbon may affect brittleness. Alloys obtained in casting processes are generally neither ductile nor malleable. The EN 1563 normative defines ductile cast iron as a “casted material based on iron, carbon and silicon, and in which carbon is primarily in the form of spheroidal particles”. Classification depends on the metallographic structure and the percentages of carbon, alloy elements, and impurities. The poor mechanical properties of some castings are due to the presence of graphite flakes [1] that produce discontinuities in the matrix and so lead to the presence of stress concentrators
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