Features of Structure and Solidification of Lengthened Double Ingots for Hollow Forgings. Part II*

Resumo

Comparison of mathematical modeling data with results of studying ingot structure show that a higher temperature in a narrow axial part of an actual ingot slows down solidification. This leads to an increase in dendrite parameter, a reduction in dendrite structure density, an increase in porosity, an increase in the amount of readily-melting sulfide and nonmetallic inclusions, and the formation of secondary shrinkage cavities. This location of shrinkage and liquation defects facilitates their removal during ingot forging and makes it possible to prepare hollow forgings from them. There is a fourfold reduction in chemical inhomogeneity and an increase in mechanical property stability over the length in test ingots. Use of lengthened double ingots for preparing hollow ingots makes it possible to increase satisfactory metal output in a forging by 8%.