EXPERIMENTAL RESEARCHES ON DRAWN STEEL. 
7 
rod as received from tlie rolling mill, and after some delay this set of samples was 
received. The wliole series comprised twelve stages in the manufacture of tijie ^vire 
as tblloA\"S 
4. (1) 'The Rolled Rod. —This is produced from a hillet of good Sheffield steel 
containing less than t per cent, of carbon. It is passed wliilst hot successively 
through a number of rolls until its diameter is about 0’5 centim. ; the liot rod is 
finally coiled in a heajD, and so cools quickly in the open air. 
(2) Rod Annealed. —The rod as received from the rolling mill is now annealed by 
enclosing it in pots from which air is excluded; these pots are heated in a furnace 
to a bright red heat, at wdrich jioint the firing is stayed and the fire is allowed to 
die out. This operation occupies 24 hours. 
(3) Rod Hcird Drawn. —-In this stage the annealed rod is forcibly drawn through 
a perforated plate, which at once reduces the sectional area by about 50 per cent. ; 
the rod now becomes hard. 
(4) Rod Tempered. —The process to which the rod is next submitted is sometimes 
called “ patenting” or “ improving.” It is carried out in different ways by different 
manufacturers, but in these wires it consisted in heating uniformly to a bright red 
heat in absence of air, and afterwards cooling slowly in a special chamber at a 
moderate temperature. 
(5) , (6), (7), (8) Wire Cold Drawn. —The tempered wire is drawn through smaller 
and smaller holes in tlie draw plate, the sectional area being reduced each time by 
about 40 per cent, of its [ireceding value; the diameter in tliese specimens is in this 
way diminished to 0T37 centim. at the 8th stage. 
(9), (10), (11), (12) The succeeding wires are now all drawn from No. 8 directly 
and do not pass thi'ough every intermediate hole ; thus No. 10 is not No. 9 drawn 
one hole smaller, ljut is No. 8 reduced at once by a single drawing, and similarly for 
the others, except, perhaps. No. 12, which probably passed through stage 9 or 10. 
These facts relating to the drawing of the last three stages are worthy of notice, 
as the results of a number of experiments on these wires show some irregularity in the 
progressive change of their physical properties in the final stages, and the method 
of drawing in these stages may in part account for the irregularity. 
5. The samples illustrating the twelve stages were not long enough to allow the 
thickest of them to Ije made more than 50 diameters long, and this fixed the 
dimension ratio for the whole series, but an additional series, from No. 5 upwards, 
was cut to a dimension ratio of 100. All the wires were magnetised in the same 
way between the poles of a powerful electromagnet, and then immediately examined 
for magnetic intensity, and its changes under variations of temperature, with the 
apparatus formerly described."^ The results, which are given in Table III., and 
plotted in Diagram III., disclose several interesting facts ; thus rolling hot and 
* ‘Roy. Soc. Proc.,’ vol. 62, p. 210. 
