The engineering properties of metals and alloys are related to their structures. The change in mechanical properties of the metals and alloys can be achieved by the process of heat treatment. Induction hardening is one such a process involves phase transformation by rapid heating and cooling of the outer surface. Induction hardening improves the outer surface hardness and wear resistant properties keeping the original toughness and ductility in the inner core. However past experiences shows that during heat treatment, parts have undergone dimensional changes due to thermal fluctuations and phase transformations. Dimensional changes can lead to excessive distortion in the component which always presented difficulties to the uses of many varieties of steels which can be hardened by induction hardening. The dimensional changes in components which have been induction hardened have for a long time proved costly and troublesome to manufacturers. These difficulties apply particularly in the automotive industry where the amount of distortion in rack and pinion assembly has been related to their noise level in operation and investigators have suggested a link between distortion and the initiation of fatigue failure. [1] Although the complete elimination of distortion would be an ideal aim, manufacturers are reconciled to the fact that a certain amount of distortion is an inherent part of the hardening process. However, if the amount of distortion is uniform and predictable, an allowance could be made in the initial machining operations. It was with these aims that investigations into the control of distortion in bright bar (EN 18D steel) used in rack application (Power steering assembly) have been carried out by parameter optimization study The engineering properties of metals and alloys are related to their structures. The change in mechanical properties of the metals and alloys can be achieved by the process of heat treatment. Induction hardening is one such a process involves phase transformation by rapid heating and cooling of the outer surface. Induction hardening improves the outer surface hardness and ductility in the inner core. However past experiences shows that during heat treatment, parts have undergone dimensional changes due to thermal fluctuations and phase transformations. lead to excessive distortion in the component which always presents difficult to the uses of many varieties of steels which can be hardened by induction hardening. The dimensional changes in components which have been induction hardened have for a long time proved costly and troublesome to manufacturers. These satisfied apply particularly in the a utomotive industry where the amount of distortion in rack and pinion assembly has been related to their noise level in operation and investigators have suggested a link between distortion and the initiation of fatigue failure. [1] Although the complete elimination of distortion would be a proper aim而且, 可以 用于 该 初次 加工 上面 的 方法. Manufacturers who reconciled to the fact that a certain amount of distortion is an inherent part of the hardening process. However, if the amount of distortion is uniform and predictable, an allowance could be made in the initial machining operations. that investigations into the control of distortion in bright bar (EN 18D steel) used in rack application (Power steering assembly) have been carried out by parameter optimization study