US1661694A - Electric resistance furnace adapted for heating by nitrogenization - Google Patents

Description

A. FRY

March 6, 1928.

ELECTRIC RESISTANCE FURNACE ADAPTED FOR HEATING BY NITROGBNIZATION Filed Aug. 2, 1926 2 Sheets-Sheet l March s, 1928. A. m 1,6 1, 94.

ELECTRIC RESISTANCE FURNACE ADAPTED FOR HEATING BY' NITROGENIZATION Filed Aug. 2, 1926 2. Sheets-$heet 2 Fig.3.

@WM 1 Wij%% Patented Mar. 6, 1928.

UNITED STATES HEISSUED "661,694

PATENT OFF-ICE.

ADOLI FRY, ISBEN-ON-TEE-BUHR,

GERMANY, ASSIGNOB TO FRIED. KBUPP AKTIENGESELLSCHAFT, 0F ESSEN-ON-THE-BUHB, GERMANY.

Application filed August 2, 1926, Serial No.

The purpose of the invention is to provide an electrical resistance furnace for hardening by nitrogenization which is char-,

In order to allow 9f my invention to be more readil understood an example of embodiment -o the same Wlll now be described in detail with reference to the drawings which accompany and form part of this specification, this embodiment s owin sistance furnace o erated b ,means 0 three base current an designs to be used for ,15 ardening steel articles by nitrogenization.

In these drawings Fi 1 is a longitudinal section through the urnace,

Fig. 2 is a section on line 2-2 of Fig. 1, Fi 3 is the corresponding wirediagram. Re erring now first to Figs. 1 and 2, A denotes the brickwork of the furnace into the foundation .of which a plurality of pillar blocks B of refractory material are built in. These blocks B, form supports .for a box D of rectangular cross section which is open at its ends and rests on said blocks B by means of cross carriers G. The box D is made of a heatand corrosion-proof alloy, forinstance a chromium'nickel steel alloy and is provided which is su divided so as to form three phase-windin and consists of .chromiumnickel-iron wire. The ends'of these windings E, E, E, Fig. 3, are led out of the furnace through its. wall in a suitable manner (not shown) and so connected, by means of a four-pole throw-over switch F, Fig. 3, to a three-phase main G, thatin the switch osition denoted .by I, star connection and in position II series connection of said three phase-windings E, 'E, E is established.

By means of suitable screw bolts 1& the box D is suspended from cross carriers H which rest on the side wallsof the brickwork. The furnace is covered on the top by an iron cover plate J loosely resting on the brickwork A and after the removal of which the box D together with the carriers H may be removed as a whole. The hollowspaces existing between box D and brickwork A and cover J are. filled with kieselguhr, as shown in Fig. 2. w

are-- on its outer surface with insulators -'(not shown) car 'ng the heating resistance E 128,850, and in Germany September 4, 1925.

The box D is fitted with a track consisting M of three U-iron rails K, see Fig. 2, riveted to the floor of the box, and of guide ribs k. Similar tracks K and K projecting into box D through the front openings of the furnace form prolongations of track K, k at both ends of the box and are arranged outside the furnace in the manner shown in Flg. 1. A system of loose double rollers M 18 adapted to run on the rails K, K, K, said rollers being interconnected by axles m and lateral frame-plates 'm. so as to form a moving platform. The length of the whole roller s stem M m 'm is about double and a half te length of the furnace.

A receptacle P, designed to receive the articles to be nitrogenized, is resting, within the heating chamber formed by the box D,

through the intermediary of a bottom plate N, on the loose rollers M, an eye serving to attach a wire rope or the like being rovided on it. The receptacle P is closed in a gas-tight manner by a cover p and is made of a chromium-nickel-steel alloy having a particularly high resistance to heat and chemical-influences. The supply of the gas delivering nitrogen to the receptacle P takes place through a pipe passing through one of its front walls an reaching nearly up to the other front wall thereof. A ipe p passin through the same front wal serves to lea oif the gas. A second, similar receptacle R rests outside the furnace on that portion of the moving platform M m 'm which rests on the track portion denoted by K The heating chamber of the furnace is shut off from the outer space by loose walls Q which have to be removed before the rece tacle P is entered.

he operation of the described resistance furnace takes place as follows.

After the furnace, still empty but closed by the loose walls Q, has been heated up by connecting the resistances E E E to the three-phase main G with the throw over switch F in position I (star connection), the switch F is turned over into position II, in which the phase windings take only so much current as it is suflicient to maintain the temperature attained by the heating-up operation. The receptacle P which has been filled in the meantime with the articles to be hardened and closed in gas-tight man- The nitrogenous her, is then entered, after removal of the loose walls Q, into the heating chamber of the furnace. When this takes place, the moving glatform displaces itself with half the spec of the receptacle P. After the ipes p and p have been connected to a gottle containing the nitrogenous gas, the furnace is closed again by the loose walls Q.

as is thereupon supplied to the receptacle Plieated by means of the resistances E E E. Dunn this operation nitrogen enetrates the art cles-to be hardened and; ardens them. During the period of nitrogenization the second rece tacle, R, is put on the track portion K and lled with articles, to be hardened. As soon as a suflieient quantity of nitrogen has been supplied the articles containedin receptacle and receptacle R has been filled, the loose walls Q'are' removed. The receptacle P is thereupon shifted in the direction of arrow m,

Fig. 1.- This motion is taken part inrby the moving platform'with half the speed, and by the receptacle R with the speed of the recep; tacle P. When the receptacle R has reached the former position of rece tacle P, the latter which now is outside the urnace, is brought I to a standstill and the loose walls Q are enized and rece tacle P is emptied and re-' brou ht into positionagain. This done, the artic es containedin receptacle R are nitrogfilled with artic es to be hardened, so that it enters the furnace at the same time when res ceptacleR leaves it. From this time the described operations maybe repeated'as, often asdesired. Finally'the furnaceis thrown out of operation by interrupting the current su 1y. p l' he fact thatthe electric heating body D is capable of receiving a shiftable' receptacle enables a great number of articles to be treated at the. same time andin a very easy manner! In comparison withv receptacles running on wheels the arrangementof the receptacle P and R on the described roller system offers the very important advantage of the pulling in and out of the filled receptacles taking place in a very any manner.

By making the heating box and the receptacle of a chromium-nickel-steel alloy which has a high resistance to heat and chemical influences (and might be re laced by any other suitable metal or alloy not only the life of the heating box and of the is pre-heated up to the treating temperature comes into contact with the articles to be hardened.

The closure of the receptacles by means of a removable cover offers the advantage, in

comparison with the front wall closures hitherto used with resistance furnaces, that the articles to be treated may be more easily set in and out and may be carefully embedded.

' Withoutdeviating from the spirit of the invention, the furnace might be closed by sliding doors instead of by loose walls.

Furthermore, the described furnace is adapted to be used, instead of the described nitrogenization, for the cementation of steel oth'er'heat treatment, for instance I or for any for heating articles in aninert gas.-

I claim: 1 f

In an electric resistance furnace adapted for hardening metals by nitrogenization, a roller system, a nitrogenizing receptacle mounted thereon, and a removable electrically' heated casing surrounding said nitrogenizing receptacle and the portion of the roller system which lies within the furnace.

The U foregoing specification h signed at Cologne, Germany, this 10 day of July, 1926.

ADOLF FRY.

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