Indian Welding Journal

K. N. Rao ¹, G. J. Guru Raja ¹

Affiliations
1 Central Mechanical Engineering Research Institute, Durgapur, IN

Abstract

Plasma arc cutting of metals is of recent origin and is widely employed in the cutting of stainless steels, special steels, non-ferrous metals and their alloys, thick sections of steel and even C.I. In oxygen cutting, the metal burns reacting with oxygen. Therefore, the speed of cutting of carbon steels for which it is widely used is limited by the speed of the chemical reaction of oxygen with iron and the speed with which the molten metal is blown away from the reaction zone.

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K. N. Rao ¹

Affiliations
1 Central Mechanical Engineering Research Institute, Durgapur 9, IN

Abstract

Residual stresses may be defined as those stresses which exist in a material free of external load, generally resulting from nonhomogeneous plastic deformation which may be introduced in many ways such as fabrication process, flame cutting, welding etc. During the flame cutting process, there is a rapid change in temperature, resulting in non uniform heating and cooling which not only introduces residual stresses but also causes changes in chemical composition of the material in the region of the edges of cut. When the heat is conducted to the surrounding parent material, rapid rates of cooling are encountered. In addition, the varying degree of affinity of iron and the various alloying elements in steel to oxygen gives rise to changes in the chemical composition of the material in the neighbourhood of the cutting area.

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