The Works Of Messrs. Schneider And Co.

64 MESSES. SCHNEIDER AND CO.’S WORKS. covering which extends from the furnace wall to the plates. Thus protected they withstand tlie high, temperature, and require but slight repair. Since 1894, when Messrs. Schneider and Co. beg-an to work this process on a large scale, none of the nozzles have worn out. Eacli furnace is fitted with a gas meter and pressure regulator. Cementing Process.—The following are the leading particulars of the cementing process : The plates, when arranged as above described, ax-e raised as uniformly as possible to a dark red heat. When this has been done, gas is admitted through the tuyeres on one side for half an Gas admission is stoppeel when the operation has been continued long enough, for a certain time, during which cementation gains in depth, the lower surfaces taking carbon from the top ones which become saturated under the action of the gas. Gas is then admitted for another half-hour, through the pipes by which the waste gas has escaped during the first part of the operation. The poor hydro-carburets escape through the opposite pipes, and are burnt outsicle the furnace. Another stoppage, of equal duration to the first one, now takes place. Thus the process goes on, gas being admitted first on one side, Fig. 148. 3,000-Ton Hydraulic Forging Press. (See page 61.) hour. The gas is distributed in the space between the plates ; the hydro-carburets separate owing to the heat ; and a powerful cementing action sets in owing to the carbon which is liberated. Part of the carbon pénétrâtes the steel of the plates in a combined state, the remainder being deposited mechanically on the surfaces of the casing, or escaping with hydrogen through the series of pipes on the opposite side. In these pipes a certain re-formation of hydro-carburets, less rieh in carbon, takes place, and this gas escapes through the fourth brandi mentioned above. The escaping gas is ignited and the progress of the cementing operation is ascertained by the appearance of the flame. then on the other, the alternation insuring an even depth j of cementation over the whole surface of the plates. The quantity of gas used is in proportion to the area of the plates ; the amount passed eacli time is regulated by meters, and the pressure is maintained uniform by ineans of special regulators. The thickness of the plates, and the conditions stipu- ated for the firing tests, détermine the time the operation is to last, and the maximum temperature which has to be maintained. The temperature is kept under complété control. This is secured by the following arrangement : Each cementing furnace is connectée! by an electric wire, the total résistance of which is constant, to a switchboard