The Works Of Messrs. Schneider And Co.

HARDENINGr PLANT. 65 placed in the works’ engineer’s office. This line reçoives, for each furnace, the current from a thermo-electric element (platinum, platinum rhodiumised), the hot soldering of which is in the inside of the floor of the cementing casing. The current to the switchboard is transferred, by the working of a commutator, to a mirror galvanometer, which indicates a simple relation between the electromotive force of the current and the heat of the furnace. The heat is thus regulated in such a way as to cause it to effect the maximum of cementation, there being no cause to fear surface melting of the plates. During the operation, the tuyeres become obstructed with carbon deposits, and they have to be cleaned every the water main leading from a reservoir, at such a level as to maintain a pressure of 3 kilogrammes per square centimetre (42.67 1b. per square inch.) Controlling valves are placed on the mains, in order to regulate the quantity of sprinkling water delivered. The second water-hardening device consists of two wrought-iron tanks 6 metres (19 ft. 9 in.) long; and 3 metres (9 ft. 10 in.) high, placed in a pit. These tanks are 1.500 metres (4 ft. 11 in.) apart. The two inside walls of the tanks are drilled with holes 37^- millimétrés (1^ in.) I apart over the whole of their surface, and the tanks are divided horizontally into five water-tight compartments, ! each. o£ which can be isolated by means of valves. By Fig. 149. 3,000-Ton Hydraulic Forging Press. (See page 61.) hour with a wire. The plates are cooled gradually while remaining in the furnace. Hardening Plant.—The horizontal hardening plant is placed approximately in the centre of the group of cement- ing furnaces just described, and in which the plates are heated. The pit containing the sprinkling jet apparatus is 8 metres (26 ft. 3 in.) long; 3.900 metres (12 ft. 10 in.) wide ; and 4.300 metres (14 ft. 1 in.) deep. The series of tubes through which the lower surface of the plate is sprinkled, is mounted on a movable frame, placed higher or lower in the pit, according to the shape of the plate. Those tubes that sprinkle the upper surface are mounted on wheels. When the plate is laid on the bottom frame, the top series of tubes is brought over it, and connected to this arrangement it is possible to use only the exact number of holes required for sprinkling any particular plate. Fürther régulation is obtained by closing any excess number of holes with wooden plugs. The plates are heated vertically in furnaces to be described further on. They are carried by a special frame suspended to the travelling crâne. The method of vertical hardening by means of water jets has many advantages. The plate being suspended during the operation, it can be brought nearer one or the other of the perforated walls, in order to vary the rate of cooling on the adjacent surface, or it can be shifted to-and- fro in such a manner as to place a part of the surface outside the action of the jets.