The chill zone and the original columnar structure have been reduced and even eliminated when the intensity of the magnetic field was increased; the coarse columnar structure is transformed into the equiaxed. The thermal fatigue of non-ferrous metal die-casting dies becomes more severe at higher operating service temperatures, reducing die life significantly. Get solutions 2. Casting Defects - Sand Mold, Metal Casting. The grain macrostructure in ingots and most castings have three distinct regions or zones: the chill zone, columnar zone, and equiaxed zone. Concentrations of impurities and alloying elements are different in different parts of the casting. The MHD equipment is essentially superimposed on the mature direct chill casting technology. These are the common sand casting defects on the surface and inside of cast iron and cast steel parts. It consists of directionally oriented crystals approx. High casting speeds decrease the thickness of the chill zone, which can break in extreme conditions. The image below depicts these zones. A casting usually begins with rapid nucleation and growth against the cold mold walls. Due to the combined effects of alloy segregation during freezing, slow diffusion and shallow 1. Small equiaxed grains (chill crystals) form at this stage. ... (1.5 to 6 in.) 11.3 Casting Terminology Pattern- approximate duplicate of the part to be cast Molding material- material that is packed around the pattern to provide the mold cavity Flask- rigid frame that holds the molding aggregate Cope- top half of the pattern Drag- bottom half of the pattern Core- … This shell of solid metal grows into the remaining liquid as solidification continues. Casting Materials. High casting temperatures (higher super heat) increase the surface temperatures of the strand. This produces a thin chill zone of tiny grains at the casting surface. – Chill zone • Rapid nucleation that occurs when the molten metal comes into contact with the cold walls of the mold • Forms a narrow band of randomly oriented crystals on the surface of a casting – Columnar zone • Rapid growth perpendicular to the casting surface • Long and thin • Highly directional – Equiaxed zone The chill zone is named so because it occurs at the walls of the mold where the wall chills the material. perpendicular to the mould surface, Equiaxed zone – this Introducing various metal casting defects with many pictures by Dandong Foundry in China. Degarmo's Materials and Processes in Manufacturing (11th Edition) Edit edition. in diameter. Figure 2. Development of the macrostructure of a casting during solidification: (a) Nucleation begins, (b) the chill zone forms, (c) preferred growth produces the columnar zone, and (d) additional nucleation creates the equiaxed zone. Blowhole and Pinhole This is a kind of cavities defect, which is also divided into pinhole and subsurface blowhole. Formation of the grain zones of an ingot is presented in the figure. Typically, in centrifugal casting, the following structure or zones may occur, Chill Zone – This layer is of fine equiaxed structure which forms almost instantaneously at the mould wall, Columnar Zone – This is next to chill zone. Problem 24RQ from Chapter 11: What is the chill zone of a casting, and why does it form? The weakening of the chill zone is also supported by the presence of coarse non metallic particles and oscillation marks.