US2415493A

US2415493A - Salt bath furnace

Info

Publication number: US2415493A
Application number: US565291A
Authority: US
Inventors: Artemas F Holden
Original assignee: Individual
Current assignee: Individual
Priority date: 1944-11-27
Filing date: 1944-11-27
Publication date: 1947-02-11
Anticipated expiration: 1964-02-11

Description

Feb. 1,1, 1947. A, F, HOLDEN .2,415,493

SALT B ATH FURNACE Filed Nov. 27, 1944 INVENTOR s 14g@ vas FFO/den @4a-1.7L ATTORNEY Patented Feb. il, A1947 unirse STATES PATENT oli-'Fica 2,415,493 sAL'r BATH FUnNacs Artemas F. Holden, New Haven, Conn.

Application November 27, 1944, Serial No. 565,291

8 Claims. l

The present invention relates to improvements in salt bath furnaces and more especially to a salt bath furnace for heat treatment of metals wherein the saltbath is heated by electrodes immersed in the bath.

The present invention has to do primarily with the shape of the pot for containing the salt bath, which shape is constructed in such manner that the electrodes for heating the salt bath may be located outside of the workin-g area of the pot. This construction provides a maximum area in which metal parts may be heat treated without the parts coming too close to the'heating electrodes.

TIhe shape of the pot according to the present invention has to do more especially with the plan View thereof rather than with other portions of the pot.

Other and further advantages of the present invention will in part be obvious and will in part be pointed out hereinafter in the specification by reference to the accompanying drawing forming a part thereof.

`It is to be understood that the disclosure herewith presented is to be considered illustrative and is not to be construed in a limiting sense.

Fig. 1 illustrates a horizontal section comprising aplan view of an electrical furnace in accordance with the present invention;

Fig- 2 illustrates a horizontal section showing a plan view of a slightly different form of electrical furnace from that illustrated in Fig. l; and

Fig. 3 illustrates a horizontal sectional view in plan of an electrical furnace in accordance with the present invention and differing slightly from that illustrated in Figs. 1 and 2.

In melted salt baths for'the heat treating of metals, which baths are heated by electrodes vimmersed in the bath, it is desirable that there shall be an unobstructed zone in which the metal parts to be heat treated may be immersed in the bath, and to this end, the present invention (referring to Fig. l) comprises a pot A which, when viewed in plan on a horizontal section, comprises an end wall I,

side walls

2 and 4, and end walls 5 and 6,

which meet at the angle of 90, whereby the area from an imaginary plane indicated by the dot'- ted line 1, and completed by the end walls 5 and 6, comprises a right angle triangular area.

Electrodes

8, 9 and I0 are located within this triangular area and preferably the centers of the

electrodes

8, 9 and I0 are at the apices of a 60 triangle II. It will be observed that the area of the pot bounded by the end wall l, the side walls 2 and 3, and the dotted line 1, is a rectangular 1 area which is free from obstruction since the electrodes are located within the triangular area previously specified as comprising the area bounded by the end walls 5, 6 and the dotted line 1.

In this construction the liquid salts within the pot circulate by convection currents in such manner that the entire bath is retained at substantially uniform heat, so that the range of heat in various portions of the bath is not suillcient to impair proper operation of the bath for heat treatment of metal parts.

. Fig. 2 illustrates a pot B of a construction similar to that illustrated in Fig, l with the exception that the side Walls I2 and I4 meet at a 60 angle so that the area between the dotted line 1 and the side walls I2 and I4 comprises a 60 triangular area. Here again the

electrodes

8, 9 and I0 are preferably arranged on the apices of the 60 triangle so that the distances between all of these electrodes are equal and the distances from the electrodes to the end side Walls of the l tends beneath the bottoms of the pots and around Y on the apices of a 60 triangle in an area at thev end of the pot which is substantially triangular and is outside of the cylindrical unobstructed working area. The curved dotted line I9 lwhen joined with the side walls I1 and I8 which continue into the partially cylindrical surface I5 subscribes an area which ivs practically cylindrical .Y

whereby this zone is capable of use without interference of any electrodes.

In accordance with the present invention the pots A, B, and C, while preferably ceramic, may -be formed of metal or other I'material suitable for the purpose of holding melted salts comprising a liquid salt bath for heat treatment of metals. These pots A, B and C are surrounded by suitable heat insulating material 20 that may be held within av steel or other suitable material,

'shell 2| so as to properly sustain the pot and insulate the same against heat loss. It-is to be understood the heat insulating material 20 ex the several sides thereof, the pots being open at the top as is common in the art.

While the present invention is designed more i especially for high temperatures from 1700 to 2350*? it has also been found to operate satisfactorily on temperatures below 1700".

The electrodes, which are of the usualltype,

' preferably are located at the apices of a 60 tri' angle. where three phase alternating current is used to supply the energy for heating the bath. These electrodes comprise rods of suitable material which are immersed in the salt in the bath.

' asians 5. An electrical furnace of the electrode type for heating salt baths for the treatment o! metal load and to properly heat the salt bath in the pot with this type of electrical current.

While the construction illustrated in Fig. .2, having the 60 end walls, is satisfactory for smailparts, comprising a ceramic pot with substantially vertical side walls and having a portion of s aid side walls extended outwardly from the main portion of the pot to provide a substantially triangular recess in horizontal cross-section forming a heating zone, three equispaced electrodes mounted in said heating zone whereby the reer type baths, the construction illustrated in Fig.

1, having the 90 end walls, seems slightly better adapted for a larger size pot, and the construction shown in Fig. 3 may be used for either the larger sizes or the smaller sizes. Furnaces in accordance with the present` invention have pots with substantially vertical walls and have been constructed and operated with the useable area varying from 280 square inches to about 45 square inches.

The electric energy supplied through the electrodes lhas varied from 125 kva. vfor the larger pots to 30 kva. for the smaller pots. A 7

The present invention has beeniound to increase the eifective operating free area of the furnace without substantially detracting from the `eillclency thereof or without substantially increasing heat losses. What I claim is:

1..In'an electrical furnace for heating salt baths for the heat treatment of metal, the commainder of said pot comprises an unobstructe working zone.

c 6. An electrical furnace of the resistance elec trode type for heating salts lto comprise a bathV for the heat treatment of metal parts, said pot having substantially vertical side walls with a substantially triangular area in horizontal crosssection extending outwardly from the main portion of the pot and thereby providingthe remainder of the pot as an' unobstructed working zone in which said metal parts may be immersed in the bath, and three equispaced electrodes arranged in triangular relation to each other withy in the substantially triangular area to heat said bination of a pot for containing the salt bath and wherein a portion of a side wall of said .pot extends loutwardly to forma zone 4in which electrodes may be located to provide a portion of said pot capable of receiving metal parts to be heat treated, and three electrodes located within said zone with' each electrode being equidistant from the other two electrodes to obtain a balanced three phase electrical load between electrodes.

within said recess whereby there is established a working zone free of electrodes and wherein said electrodes being equidistant one from another provides a balanced three phase electrical load.

' 3. An electrically heated furnace adapted for heat treatment of metal parts in a liquid salt bath, said furnace comprising a, pot adapted to hold the salt bath and having an outwardly extended portion inthe side wall of said pot to provide aheating zone, and three electrodes mounted within said heating zone on the apices of a 60 triangle, the remainder of said pot comprising bath.

7. An electrical furnace for heating salts for.

the heat treatment of metal parts, said furnace comprising a pot having a heating zone and a working zone, said heating zone being created by extending outwardly a portion of the walls of said pot to intersect at an angle not in substantial excess of 90 or substantially less than 60 to provide a recess of substantially triangular arca in horizontal crass section, and three electrodes in triangular relation symmetrically positioned within said recess whereby there is established a working zone free of electrodes and wherein said electrodes provide a substantially balanced three-phase electrical load.

8. An electrical furnace forheating salts for the heat treatment -of metal parts, said furnace comprising a pot having a heating zone and a working zone, said heating zone being created by extending outwardly a portion of the walls of said pot to intersect at anangle of substantially 60 to provide a recess df substantially triangular area in horizontal cross section, and three electrodes in triangular relation symmetrically positioned within said recess whereby there is es- I.. tablished a working zone free of electrodes and a working zone substantially free from any obstruction and with the walls of said pot being substantially vertical..

4. An electrical furnace4 ofthe electrode type f for heating salt baths for the treatment of metal parts, comprising a, ceramic pot with substanl tially vertical side walls and having a portion of said side walls extended outwardly from the main portion of the pot to provide a recess forming a heating zone, electrodes mounted onthe apices of a 60 triangle in said heating zone whereby the .wherein said electrodes provide a substantially REFERENCES crrnn The following references are of record ln the ille of this patent:

UNITED STATES PATENTS Number Name y Date s 1,782,482 Seifert et al. 1. Nov. 25, 1930 1,811,754 Hultgren Junev 23, 1931 2,234,476 Jessop Mar. 11, 1941V 1,373,615 Jacobs Apr. 5, '1921 1,792,674 Bellis Feb. 17, v1931 1,864,885 Bellis June 28, 193,2 1,985,623 Ross Dec. 25, 1934 V2,145,677 Adam, Jr. Jan. 31, 1939 2,336,412 Messinger Dec. 7, 1943 2,089,690 .Cornelius Aug. 10, 193'? .FOREIGN PATENTS Number Country x Date 422,868 British Jan. 21, 1935 215,009 Swiss Aug. 16, 1941