THE MAKING OF ARMOUR

Pukekohe & Waiuku Times, Volume 6, Issue 253, 23 February 1917, Page 2 (Supplement)

THE MAKING OF ARMOUR

SOME INTERESTING ¥1 1 ho steel 'for armour plates i in furnaces fired by gas, each will melt 40 tons in about 12 h is drawn off into ladles, transp electric cranes capable of lif tons, and poured into maw moulds, some of which weigh without the steel. Some of tl weigh 00 tons and are 36 inch They are re-heated and rolle an immense mill. (Jne of thes< Messrs. Yickers' works (s " ximes" Engineering Supplem lolls 30 inches in diameter an< in length . An ingot 36 incl can be rolled down to six incht an hour. The thickness after equal, but the edges are rougl regular. At this stage the firy ol tho cementing process is pe 'Tho plates are Laid one on to other in specially constructed I Powdered charcoal is sprinkled the opposed surfaces, and the j main in the furnaces from ] days, the temperature being r by pyrometers. During that p charcoal is absorbed by the pi creasing the quantity of carbo near the surfaces. This does no the surface of the plate, but it i: for the subsequent hardenii is done at a later stage, after t ing in the case of Cfiose plato have to Ik> curved, and after t ing off of the rough edges in th all plates. Both operations ini use of much massive machin careful handling.

BENDING AND PLANT The binding is done in 1 presses. Messrs. A'ickers hav< *,l)00 tons power, which w plates 'ip to 21 feet long and wide. The pressure exerted ton i to each square inch of t Each weighs 6<X) tons. The lie tlie thickest plates cinder the persuasion of these prc&sen is « quickly accomplished. In the n< the surfaces are planed on 1 which will carry a plate weij tons on a moving table, <wei| much, and will reciprocate it u cutting tool's, which cut in bo tion.s. The plate moves at a about 11 feet'a minute. In otl of machines the plate is fixed below and the cutting to traversed over it. It is nece plane the surfaces of the plates ly, for, although they hare be and are smooth, the tluckne not .so uniform as they should 1 a jio them to Iks fitted perfectly places. Afterwards the verv ro irregular edges are planed "in i of a totally different design, platen must have their edges and provision is made for deal these by means of hinged tool When a large quantity of met: lie removed the edges "are cut o with circular saws. Even i edges occasion on difficultly i dealt with in a machine provi A movable tool saddle, the toe controlled by a templet of the si lino as the edge to be planed guido pin working over the Sometimes also such edges are Afterwards the holes have to I in the faces, and screw thread them; all this work must be a before the plates are harden tho hardening would damt smooth hoka and the deJiea threads, these are plugged * during the hardening process holes at tho back to receive 1 by which tho armour plates are to tho hull of the ship are dri screwed subsequently to hardei cans© hardening does not aff backs of theoe plates.

HARDENING.

The hardening process tempi stages—the moderate hardenin plate right through, which i more correctly termed temper the intense hardening of the ou Ine first is done with oil, thi with water. In the first stage I is reheated in a furnace to i temperature and dropped sudd« a bath of cotton seed oil, largt to temper the entire plate wit coming iteelf sensibly overheat' result is that the plate is han toughened throughout withou rendered brittle. It is both and tougher than it was lie 1 moision, but it would not resis em soft-nosed shell. .* 'terws surfac.?. which lias been satura carbon to a depth of from 2J dies, is rendered of excessive by a chilling process. A series ( cold water are directed under against the highly carbonised the plate having been heated fi us continued during two or tnr« by which time the surface to a far as the car!>on has penetrj become of glasslike hardness. process were continued until t had become intensely hard fa tiro thickness it would be « crack under the impact of the & with the hard suriace hacked much greater thickness of r tough and soft material, the identical with that obtained f though much less efficiently, compound plates of wrought ir with stcd. To secure the bes large volumes of water are reqn otherwise tho internal heat thick plate would be transmits surface and cause some softenii plate 12 inches thick from 40(K tans arc discharged over the fa pressure, too, must be sufficien vent steam from forming on tl which would reduce the cliiUir

FITTING. It is well known that when heen suh.ic.teid to a hardenini it liecumes distorted fiom its shape, and dimensions, and a hardened steel cannot be shaj n;ttin<j took. As. therefore, t, alter hardening do not retain t shapes which they possessed b the nceessary corrections are by grinding wheels. Ihe-eals sot to anv an.nle in order to 0 the hovelled edges. After all t ha>, U'i u done on the plates not scut to the shipyard to lie p. sit on. They are first fitted edge to edge in the shops, w! eorrec tions that may be requin made more read'lv than on tin