Abstract
In the present experiments gas welding of nodular graphite cast iron (3 kinds of Cu-Mg, Fe-Si-Mg and Ca-Fe-Si-Mg system by casting methods) was mainly carried out supplementarily with remelting and casting experimentations of the same samples.
Concerning gps welding:
1) In order to take full advantage of the high toughness of this cast iron, the structure of welded parts was made as near as possible to the nodular graphite structure of mother plate.
This was accomplished by using welding core of same material and other cast iron and adding some Mg alloy to welding flux.
2) Welding was done by heat treatment so as to avoid the chilling and marternsite tendency of welded parts.
3) Mg alloy addition to the flux was found useful in developing graphite spheroids.
4) The results were compared with the data obtained from operations with other than the above non-castiron welding cores.
Concerning remelting-casting experiments:
1) Tendency of disappearance or fine-graining of graphite grain under heating temperature, of this cast iron and tendency of chilling effect with varying cooling velocity were observed to know roughly the cooling-speed effect on appearnce of spheroid graphite and chilling in welding.
2) Under the heating temperature of gas welding, some of the graphite grains become finer, but others remain to grow during the cooling process.
3) At the cooling speeds of weld metals, around 6°C/sec or less, (temperature range of melting point-A1 point), chilling did not occur.
