Abstract
Porosities are often found in the center of forging ingot together with “V” segregation. For the production of sound ingot, therefore, it is essential to develop a method to estimate the size and the location of the porosity. For this purpose, four forging ingots were examined by ultrasonic testing to evaluate the size and location of the porosity. Computer calculation of solidification was also carried out on these ingots to study factors influencing the formation of the porosity.
As a result, it was found that the size of porosity was not determined by such parameters as temperature gradient and solidification rate but by a new parameter L/D, where L and D are height and width, respectively, of semi-solid region formed during solidification in the center of ingot. The parameter L/D is a function of solidification condition and the grade of steel. By calculating the distribution of L/D along the axis of ingot by computer, porosity zone can be predicted for each porosity size.
