Tuesday, March 30, 2010

Strong Magnetic Field Improves Mechanical Properties of Gray Iron Used in Engines by Changing Nanostructure

In U.S. Patent 7,686,895, Caterpillar Inc. (Peoria, IL) scientists reveal a manufacturing method that improves the mechanical properties of gray iron components by applying a substantially uniform magnetic field to change its nanostructure. The method also includes heat-treating the gray iron while the gray iron is within the magnetic field.

According to inventors Ashwin A. Hattiangadi,  Adrian Vasile Catalina, Leo Chuzhoy and Jun Cai experiments show that the microstructure of a ferrous material may be determined by phase transformations that occur when the material is cooled from a high temperature to a low temperature. Applying a magnetic field may facilitate such transformation, and thereby change the microstructure of the ferrous material. In particular, for gray iron, under a heat treatment in an ultra-high magnetic field, the nano-crystalline pearlite lamellar spacing may be changed. Thus, the mechanical properties of gray iron may be effectively changed and improved for engine use.

Gray iron containing about 2.1% to 4% by mass of carbon may be used to form a component or a part of an engine. The component may be initially formed with a conventional metalworking process such as sand casting. After the gray iron component is formed, the component may be heat-treated. Heat treatment provides an efficient way to manipulate the properties of the metal by controlling the cooling process. The heat treatment process may include annealing and/or quenching. Annealing is a process that produces equilibrium conditions by heating and maintaining at a suitable temperature, and then cooling very slowly. It is used to relieve internal stresses, refine the structure and improve mechanical properties of the metal. Quenching is a process in which the gray iron component may be heated to a high temperature and then quickly cooled to improve the hardness of the component.

According to Caterpillar’s disclosure, in one embodiment, superconducting magnets may be used to generate a magnetic field within which the gray iron component may be heat-treated. Superconducting magnets typically are electromagnets that are partially made from superconducting materials, such as niobium-titanium. With such superconducting material, the magnets can reach an ultra-high magnetic field intensity. Superconducting magnets can produce a substantially uniform magnetic field with essentially no energy consumption after being charged to a predetermined field strength. Superconducting magnets are now commercially available.

1 comment:

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