Hardness is a characteristic of a material not a fundamental physical property. It is defined as the resistance to indentation and it is determined by measuring the permanent depth of the indentation. Indentation hardness value is obtained by measuring the depth or the area of the indentation. Non-uniform heating or cooling of the tube can result in serious anomalies in the hardness throughout the body of the pipe. In the case of a hard spot, the hardness level is considerable higher than that of the surrounding metal, usually as result of localized quenching. High hardness is oftenassociated with loss of ductility, which can lead to brittle fracture. The problem is more common with large diameter line pipe than with casting ortubing.