Fracture Analysis of White Cast Iron (As Cast, Tensile Test)

Analysis of Fracture in White Cast Iron by Tensile Test

White cast iron, also known as malleable cast iron, is an iron-carbon alloy that has been heat treated to increase its hardness and strength. It is commonly used in many manufacturing industries, such as automotive and heavy machinery, for its high tensile strength and excellent wear resistance. The tensile strength is a measure of how well a material can resist failure when it is stretched or pulled apart. It is a critical factor in determining the durability of parts, as well as other important characteristics such as strength and fatigue resistance.

In order to evaluate the quality of white cast iron, a tensile test is conducted which measures the forces required to break the material. The test result is usually expressed as a tensile strength and an elongation value. The tensile strength is the force required to break a unit area of the material, while the elongation is the amount of strain the material experiences until fracture. By examining the fracture surfaces of a part after tensile testing, it is possible to gain insight into the material’s behavior under loading.

The fracture surface of white cast iron can be divided into two distinct regions: the area of brittle fracture and the area of ductile fracture. In brittle fracture, the material breaks along a plane with little or no plastic deformation before breakage. On the other hand, in ductile fracture there is deformation, and the fracture surface is composed of several broken pieces and voids. This is caused by the material reaching its yield strength before breaking, resulting in plastic deformation.

The factors that influence the fracture behavior of white cast iron are mainly the chemical composition and grain size of the material. The amount of carbon and the amount of ferrite present in the material directly affect the materials strength. The grain size of the material is also important as it affects the materials yield strength.

In summary, white cast iron is a versatile material with excellent properties such as high tensile strength, excellent wear resistance, and toughness. By conducting a tensile test on a sample of the material, the fracture behavior can be determined and meaningful information can be obtained regarding the material’s properties. Knowing these properties is useful in determining the best part design, selection of materials, and production processes.

White mouth cast iron is a special alloy casting, with high hardness, good mechanical and chemical stability, which is widely used in engineering machinery, agricultural machinery and various automotive parts. In order to ensure its use performance, the tensile properties of the white mouth cast iron must be tested.

The tensile test of white mouth cast iron generally uses dumbbell-shaped specimens. Before the tensile test, the surface of the specimen must be polished to Ra 0.63μm and then the casting surface is observed and photographed by microscope. The statistical parameters are measured and taken into the analysis system of microstructure. During the tensile test, the specimen should be placed on the guide sleeve of the testing machine and the tensile force should be applied gradually. During the tensile process, mechanical parameters such as elongation and breaking force are captured until the specimen breaks. After the break, the fracture surface of the specimen was observed and photographed by microscope and analyzed for its type.

Generally speaking, the white mouth cast iron has the following fracture form: brittle rupture or cleavage fracture, generally because of micro-defect like shrinkage cavity or absence of dense material; micro-fold or fibrous fracture form due to repeated appropriate plastic deformation. Combination fracture formed by brittle rupture and plastic fracture.

According to the analysis of the fracture surface, the fracture of white mouth cast iron is mostly caused by brittle fracture. It turns out that white mouth cast iron has a tendency of brittleness and its failure performance is poor. During the tensile test, inspectors should pay attention to observe and guard against the brittleness while applying the force.