1918.] The N.Z. Journal of Science and Technology. 
81 
molten metal in the ladle per ton of finished castings (taking 60 per cent, 
as the foundry 44 load-factor ”) at pre-war prices would vary from £7 with 
the poorer-quality castings to probably £10 with the best quality melted 
from all cold in the converter by the Stock process. 
(3.) Crucible furnace : This type of furnace may be considered out of 
date for New Zealand conditions. It is virtually impossible to turn out 
castings containing under 0-25 per cent, carbon with this process, and with 
graphite pots the carbon percentage will be over 0*5. This steel will require 
annealing, and is therefore undesirable. Further, the charge must be care¬ 
fully selected, as all the impurities increase in the process and finally the 
process is much more costly to work than either the converter or the—- 
(4.) Electric furnace : The tremendous advances made in this process 
during the last five years prove conclusively that it is no longer restricted 
by cost considerations to the manufacture of high-priced steel. The report 
of F. W. Harbord to the South African Government (about 1911) unhesitat¬ 
ingly recommended the use of electric furnaces in that country for steel 
castings, and it is clear from the report that the conditions he was con¬ 
sidering closely approximate those current in New Zealand in normal times. 
Here we have to bear in mind the following factors :— 
(1.) Pig iron is high in cost, and our distance from the blast furnaces 
renders control of analysis very difficult. Thus quite unsuitable 
pig may be fovwarded and the time element prohibits its being 
returned. 
(2.) Mild-steel scrap is fairly plentiful and cheap, but the phosphorus 
and sulphur content is highly irregular, often in the neighbour¬ 
hood of 0*1 per cent. 
(3.) Metallurgical coke is costly and highly sulphurous in quality. 
(4.) Firebrick and lining-material are costly, and expert labour in this 
direction is scarce. 
The electric furnace surmounts all these obstacles in its stride. 
Moderate quantities of both phosphorus and sulphur can be simply and 
cheaply refined from the molten metal; a charge of all mild-steel scrap 
can be used ; irregular charges can be conveniently dealt with, as refining 
of any degree is practicable ; there is little wear-and-tear on the lining, 
as the metal is not greatly agitated and the slag-line can be kept at a 
constant level. The type of electric furnace should be chosen for its 
mechanical qualities rather than for its electric. It is extremely doubtful 
whether any advantage whatever exists in any electric furnace over any 
other save in so far as the general considerations have been followed of 
simplicity, reliability, strength, and heat-resisting and heat - retaining 
qualities which govern the design of all high-temperature furnaces. Of 
course, the metallurgical qualities only are here referred to; naturally, the 
form of electric power available will affect the question of whether a 
furnace using direct or alternating current should be chosen. Thus in New 
Zealand, where the power will usually be derived from three-phase supply, 
a furnace using alternating current will be found most suitable. Whether 
that current is one, two, or three phase is immaterial. The single-phase 
furnace will require a dearer type of transforming apparatus, but this is 
compensated for by the cheaper arrangement of the furnace itself. Induc¬ 
tion furnaces are not so well suited for refining purposes as the arc type, 
because it is impossible to pour off all the slag; nor are they so convenient 
for general foundry use. The tilting furnaces of the arc-resistance type 
are certainly preferable from the foundry point of view, and the' makes 
personally preferred are the Snyder and the Electro-Metals. The Snyder 
is an American-built furnace of simple, rugged construction, using single¬ 
phase current through a single vertical electrode, and this results in the 
6—Science. 
