US1617359A - Heat-treating furnace - Google Patents

Description

Feb. 15, 1927. l 1,617,359

S. WESTBERG HEAT TREATING FURNAGE original Filed March 18, 1925 2 sheefsheet 1 21. 2| E? Q12?- E@ W25 I; A''TORNEY Feb. 15, 1927. 1,617,359

S. WESTBERG HEAT TREATING FURNACE Original Filed March 18, 1925 2 Sheetssheet 2 sealed, thereby reventing'the inflowl of air l Patentedleb. 1927s l UNITED STA SIGURD WESTBERG, OF PITTSBURGH,.PENNSYLVANIA.

HEAT-TREATING FURNACE.'

Application led March 18, 1925*, .Serial No. 16,404. RenewedJJuly 17, 1926.

My `invention` relates to heattreating means and particularly toelectrically heated heat-treating furnaces. i

Theobject of 1 ny invention is to provide an electric furnace that is substantially to the furnace c amber.

In practicing my invention, I provide al furnace chamber' having electric heating means associated therewith, which chamber is separatedv from an auxiliary chamber by a common wall member, the combination of the two chambers forming va unitary structure. The furnace chamber is subjected to the operation of a vacuum. pump to remove the air therefrom and produce a partial or a substantially complete vacuum therein.

' -The auxiliary chamber is subjected to the operation ofl a pressure pump that forces either an inert'or a reducing-gas int-o the chamber. -The auxiliary chamber effectively seals the furnace chamber, thereby7 providing a structure that may be used for treatingmetallic articles with heat without the undesirable oxidizing effect that occurs with furnaces having no means for excluding air.

In the drawings,

" Figure 1 is a View, ing-vertical section,

- through a furnace embodying my invention,l

Fig. 2 is a view, in vertical section, through a modified form of device embodyino` my invention, and' p i ig.- 3 is a view, 'in vertical section, through a stillfurther modification of the device embodying my invention.

Referring more particularly to Fig. 1 of the drawings, a furnace 11 com rises a container 12 that is preferably of metal and that may be of any suitable ordesiredshape in contour, although I prefer to employ a substantially circular container that is open at the top portion thereof.' T he container 12 is lined with a suitable refractory outer lining 13, of heat-insulating material, and an inner lining 14 of a high-temperature resist- -ng refractory material, the two linings being so arranged and disposed in the container 12 as to provide a furnace or chamber 15 therein.

A heat-insulating coverl member 16 encloses the lower portion of the furnace chamber that is designated more particularly by the numeral 15 and which is adapted to receive the material to be'heat treated therein. This materialis indicated generally as -valve member 32 bein a relatively large mass 17 of'solid material.

The member 16 is provided with suitable peripheral metallic portions 18 that serve. to strengthen the same and permit of easy and quiclnremoval and replacement thereof.

Electric heating means, comprising a luiality of resistor members '19, is located) in the furnace chamber, the ends of the resistor members being brought out through suitable bushings extending throu h the refractory linings and casing 12.l his construction is indicated generally only as an method known in the art maybe emplo e Wliilelliave indicated resistor mein rs as comprising the electric heating means, I

do notwish to be restricted thereto, as I may employ high frequency electric currents-traversing a suitable coil, or I may employA inductive heating at ordinary frequencies.

The furnace chamber proper is enclosed at the top thereof by a metal plate 21 that is of such shape as to conform to the general form of the casing 12, which at the upper portion thereof is provided with an annular flange portion 22 to provide a seatfor the plate 21. An 'external cover member comprising a metal plate 23, is provided to enclose an auxiliary chamber 211, the member 23 lbeing secured against the upper portion of the tial or asubstantially complete vacuum therein. The cover member 16 has an opening 30 therethrough to permit free 'communication between the port-ions of the chamber 15 above and below the cover member 16.

A force pump 29 is connected to the auxiliary chamber 24 by means of a pipe 31, a located in the pipe 31 to permit of regulating the amount of inert or of a reducing gas that is forced therein by the pump 29 from a source of supply (not shown). The force pump 29 effects a chamber 24, but also by the effect of the vacuum within the Work-receiving compartment or chamber 15.

The inert or reducing vgas in the auxiliary chamber 24 effectively seals the furnace Y a reducing gas to fiow into the Work-receiv--` chamber 14, whereby air is prevented from entering the furnace chamber, `and oxidization of metal or other materials enclosed therein for the purpose of heat treating the same, vis substantially prevented. Bright metallic articles, such as members of sheet steel, may be successfully subjected to heat Without danger of oxidizing, tarnishing or otherwise dimming their luster and reducing the thickness of the sheet.

It may be desirable to permit an inert or ing compartment 15 duringthe operation of heat treatment of a mass of metal 17, and to this end` I provide a conduit 33 that has a pressure-reducing valve 34 located therein and which is connected to a suitable source of supply of an inert or a reducing gas as may be required. The conduit 33 has its inner end so located relatively to the mass of material 17 being heat treated, and to the exit conduit 27, that substantially all of the external surface of the material 17 will be bathed in t-he inert or reducing gas. The pressure-reducing valve 34 is provided in order that the effect of the incoming gas entering through the conduit 33 will not seriously disturb the vacuum condition effected by the vacuum pump 26.

In order to prevent in so far as may be possible, the inrush of air when removing the .material, I provide a short conduit 35 having a valve 36 therein, that has its outer end connected to the conduit 31. During the operation of the furnace, the valve 36 is tightly closed, thereby preventing the entrance of any inert or reducing gas to the Work-receiving compartment 15.

When it is desired to remove the mass 17 after heat treating, the valve 32 may be closed either partially or totally, andthe valve 36 opened, whereby inert or reducing gas will ow into the furnace chamber 15, whereby a pressure will be built up Within the container 12 and the entrance of a relativelyl large quantity of air when the cover members are removed is prevented.

Referring more particularly to Fig. 2, I have there illustrated a modification of the furnace shown in Fig.' 1 and applicable more particularl to a method of electric heating, wherein the mass of material constitut- `ducing gas (not shown).

ing the resistor, and the current is led into and from the mass of material by electrodes.

The construction illustrated in Fig. 2 ma y also be employed where the electric heating means is constituted by-an electric arc.

A casing 41 of metal, such as steel. is provided with an upper annular flange portion 42, upon b'hich is mounted a removable cover plate 43 that is secured to the container or casing 4l, by a plurality ofI bolts 44. An outer lining 45,' of refractory heatinsulating material, and an inner casing or lining 46, of a refractory high-temperature resisting material, is located Within the container 41. A furnace chamber 47, is provided Within the lower portion of the container 41 within the refractory linings." A removable cover member 48, of suitable refractory material, is `provided and is normally in operative engagement with the linings 45 and 46. Al suction pump 49 is connected by means of a conduit 51, having the valve 52 therein, to the furnace chamber 47 to remove the air and other gases therefrom.

A pair of elongated electrodes 53 and 54 extend into the furnace chamber in diametral relation to each other, suitable openings being provided in the container 41 and the refractory linings to permit of the electrodes projecting into the chamber 47. A plate 55, of electric-insulating material, is located against the outer surface of the container 41 adjacent to the openings therein, and is so dimensioned thatit operatively engages the electrodes extending therethrough in order to reduce the amount of gas flowing' into vthe furnace chamber along the electrodes,

to the minimum possible amount.

An open-ended annular easing 56 is-provided at each side' of| the container surrounding a portion of' the lengths of the are suitably mounted against and insulated from the metal container 41. A cooperating outer openended casing 5T is provided for each of the tWo casings 56, having an outer portion that,fits closely around the electrodes 53 and 54, respectively, and that telescopes with the rasings 56.

Suitable current connections, not. shown, are provided to the electrodes 53 and 54. A force pump 58 is connected. through a conduit 59 having a valve 61 therein to the two auxiliary chambers 62 and 63 that are formed by the cooperating telescoping casings 56 and 57. The pump 58 is connected to a source of supply of an inert or a re- A mass of material 66 is located within the lower portion of the furnace chamber 47, and is operatively engaged by the inner ends of the electrodes 53 and 54, if the material 66 is electrically-conducting. If the material 66 is not electric-conducting or if it is not de- 'electrodes 53 and '54, and these containersA llll lili) sired to permit the l current to traverse the same, it Will be located below the op:

posing electrodes which are then brought *mediate cover member 48 effectively pre- Y heatin lplurahty of electric resistors, are adapted to vent the-inflow of any oxidizing agent, such as air into the furnace chamber, but such gaseous fluid may flow into the furnace chamber through the openings in the menibers 55 and along the electrodes. The action of the force pump 58 in filling the ` chambers 62 and 63 `with an inert or reducing gas under pressure effectively prevents, therefore, the inflow of'any oxidizing agent ,into 4these auxiliary vchambers and from there into the work-receiving cham ber 47.

The operation of this formof device embodying my invention is, therefore, substantially the same as that hereinbefore set forth in connection with Fig. l of the drawing.

Fig. 3- illustrates a still further modifica- -tion of my invention and comprises a furnace of theinverted type wherein the cover member is removable from a base plate.

A base plate 71, that may be preferably of steel or iron, has located thereon a block. or plate 72 of a suitable refractory material that is adapted to support a mass 73 of metal to be heat treated. Acover 'member 74, having an open bottom, has located therein an outer lining 75 of a suitable refractory heat-insulating material, and an inner lining 76 of suitable ,high-temperature .resisting refractory material. The two linin are so disposed and arranged as to provi a furnace chamber 77 adapted to receive the mass of material 73. The electric means 78, here illustrated as a be traversed by current. While I have illustrated the heating means as comprising resistor members, I do not wish to be restricted thereto, as an arc-producing heating means, or inductive heating may be employed if desired.

An annular member 79 is located on the base 71 and is provided with an upstanding flan 81 that is adapted to fit closely around the ower portion of the container 74.` The member -79 providesan auxiliary chamber 82 of a substantially annular form around the lower portion of the casing 74.

A suitable suction pump (not shown) of the same type hereinbefore described in connection with Figs. 1 and 2 is provided and has a flexible connection with a conduit 83 extending into the chamber 77 to permit of removing an oxidizing gaseous fluid therefrom. A force pump 84 is connected, through a conduit 85, having a regulating valve 86 therein, to the auxiliary chamber 82, whereby the furnace chamber is` effectively sealed against the introduction of an oxidizin agent into the chamber.

A con uit 87 is provided that will permit ofthe introduction of a reducing or an ncrt gas into the furnace chamber, as was hereinbefore described in connection with Fig. l and fojr the same purpose.

Various modifications and changes may be made without departing from the spirit and scope of the invention, and I desire, therefore, that only such limitations shall be placed thereon, as are imposed by the prior art.

Y each of said chambers.

2. In an electric furnace, the combination with an electrically heated furnace chamber, and means for maintaining the chamber at a pressure relatively lower than atmospheric pressure, of means for subjecting said chamber to a sealing medium containing an inert gas.

3. In an electric furnace, the combination with an electrically heated furnace chamber, of an auxiliary chamber associated therewith and containing an inert gas maintained at a relati'velyl higher pressure than the pressure within the furnace chamber. i

4. In an electric furnace, the combination with a' furnace chamber having electric heating means associated therewith, a cover member for said chamber, an auxiliary chamber enclosed by said cover member, and means for separating said auxiliary chamber from said furnaceI chamber, of means for supplying an inert gasI to said auxiliary chamber. 5. In an'electric furnace, the combination with a furnace wall enclosing a plurality of chambers, of a common closure member for the chambers, electric heating means located in one chamber, and means for maintaining the chambers at relativelydifferent pressures.

6. An electric furnace comprising a plurality of chambers maintained at relatively different pressures, an inert gas in one of the chambers, and an electric heating means in another of said chambers.

7. An electric furnace comprising a refractory wall enclosing an electrically heated furnace chamber, a closure member therefor, said closure member substantially forming a wall of an auxiliary chamber associated in operative relation with said furnace chamber, means for maintaining the furnace tainer, a refractory lining therefor, an electrically heated chamber partially enclosed b sal'd lining, a closure member for saifl chamber, said closure member substantially forming a wall of an auxiliary chamber partially enclosed by an extension of said container, another closure member for said auxiliary chamber, and means for maintainmg an lnert gas therein at a pressure relatively higher than thepressure in said fur-y nacechamber. n

9.- In an electric furnace, the combmatlon with an electrically heated furnace chamber, of an 'auxiliary chamber associated animano therewith and containin than the pressure within the rnace chamber.

10. A11 electric furnace com rising a plurality of chambers maintained) at relatively diierent pressures, a reducing gas in one of the chambers, and an electric heating means in another of said chambers.

Intestimony whereof,i I have hereunto subscribed my name this 2nd day of March, 25

SIGURD WESTBERG.

a reducing 1l maintained at a relative y hi her pressure

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