Method of testing for and preventing the possibility of cracking, spalling or like defects in rolling mill rolls by determining the rate of change in hardness

A method of testing for and at least reducing the possibility of the occurrence of cracking, spalling or like defects in the exterior cylindrical surface of a cylindrical steel rolling mill roll, the method including the steps of:

• a. determining the rate of change of hardness along a reference direction for at least a part of the roll surface to find locations therealong having rates of change greater than a predetermined maximum value known to foreshadow the possibility of the occurrence of defects for the roll and the conditions to which it is subjected in operation, and
• b. when the rate of change of hardness along the reference direction exceeds the said maximum value heat-treating the roll,
• c. determining the rate of change along the reference direction on the heat-treated roll, and
• d. repeating the steps b and c as necessary until the rate of change is below another predetermined maximum value.

A method of testing for and at least reducing the possibility of the occurrence of cracking, spalling or like defects in the exterior cylindrical surface of a cylindrical steel rolling mill roll, the method including the steps of:

• a. determining by means of an eddy current detector the rate of change of magnetic conductivity along a reference direction for at least a part of the roll surface to find locations therealong having rates of change greater than a predetermined maximum value known to foreshadow the possibility of the occurrence of defects for the roll and the conditions to which it is subjected in operation, and
• b. when the rate of change along the reference direction exceeds the said maximum value heat-treating the roll,
• c. determining the rate of change along the reference direction on the heat-treated roll, and
• d. repeating the steps b and c as necessary until the rate of change is below another predetermined maximum value.