77 
1918.] The N.Z. Journal of Science and Technology. 
STEEL-CASTING FURNACES UNDER NEW ZEALAND 
CONDITIONS. 
By S. H. Jenkinson. 
The use of steel castings is only advisable where cast iron is too weak 
for the stresses involved and where the conditions preclude the use of 
die forgings or stampings. Although this province imposes restrictions 
on output, it provides wide limits as to cost, and therefore the main 
consideration is that of quality, and especially that of uniformity and 
reliability. This is specially true under the conditions existing in New 
Zealand, where the only opening is for a jobbing foundry working on a 
wide range of light shapes. In such a foundry the cost of producing 
molten steel in the ladle is only about one-third of the final cost of the 
castings, and the moulding difficulties form the crux of the situation. 
These difficulties are much greater in steel-casting than in iron-casting, 
and are, of course, particularly accentuated in light thin work and in 
work where only a few castings are required off each pattern, since in 
this work the inevitable lost casting forms a high percentage of the total 
and the job is not big enough to stand any experimenting with risers, 
gates, &c. Nevertheless, there are now steel-foundries in New Zealand 
that have virtually overcome their moulding difficulties, and their success 
will certainly encourage the designer to specify steel castings much more 
largely in future. After the war a good demand is certain to arise for 
this product, but those foundries desiring to satisfy it can only achieve 
success by pouring, molten metal of uniform reliable quality at correct 
moulding-temperatures, which will allow uniform practice on the moulding- 
floor and will not require the castings to be annealed. 
Such metal must first conform to a rigid chemical analysis, and the 
influence of the more usual metalloids must be understood. 
Carbon tends to increase the tensile strength and fluidity of the metal 
and also lowers its melting-point. It renders steel hard and brittle, and 
decreases greatly the ductility. The higher the carbon the more irregular 
and difficult the metal becomes on the moulding-floor and the greater the 
necessity for subsequent annealing, so that steel of above 1 per cent, carbon 
is wild and practically unmanageable. Carbon, then, should be kept as 
low as possible in New Zealand jobbing foundries, having regard to the 
proper melting of the steel and the proper filling of the mould. Annealing 
is a costly, slow, and delicate process under jobbing conditions, and the 
difficulty of heating many small castings of varied shape and volume 
to a uniform closely regulated temperature of 900° C. (1,650° F.) and 
allowing each to cool slowly and uniformly is almost prohibitive in 
ordinary work. Now, annealing may be safely neglected if the carbon 
content of the steel is under 0*25 per cent, (of course, heating to a visible 
red heat may be necessary to relieve shrinkage stresses), and this is the 
maximum to be worked to. 
Silicon increases the shrinkage (which is particularly troublesome in 
steel castings) and decreases the fluidity. It certainly does not increase 
the strength or ductility, and therefore should be kept below 0-5 per cent. 
A little silicon (up to about 0-2 per cent.) makes for sound castings, 
acting as a deoxidizer. 
Phosphorus is possibly beneficial up to 0*05 per cent., but if present 
in larger quantities seriously affects the ductility and toughness : 0-08 per 
cent, is the maximum allowable. 
