Abstract
In the malleable iron foundry, it is generally believed that packing material is very important in annealing white cast iron to get a good malleable iron casting, but as the theory of annealing white iron has shown, the packing material is not necessary to make black heart malleable cast iron, although it is very important in obtaining white heart malleable which is manufactured by decarburizing castings. The author made a special installation and measured the decarburizing amount by the evolved gas during heating white iron castings at a high temperature; by this experiment it was possible for him to explain the mechanism of decarburization.
In addition, the author meassured the following effects:-
(1) The effect of the temperature on decarburization of castings when packing material is not used;
(2) The effect of the amount of iron oxide on decarburization at a constant temperature;
(3) The effect of the temperature on decarburization when packing material is used;
(4) The effect of various oxidizing materials on decarburization when they are added to iron oxides.
After these effects were thoroughly examined, the author annealed several test pieces of white cast iron of same material in a large furnace with and without packing material, and tested the annealed pieces in these two cases. The effect of decarburization upon the tensile strength and the tenacity was also studied.
Finally, the author measured the thermal conductivity of several packing materials and recommended an ideal process of annealing white iron castings for the production of black heart malleable iron.
