US2464508A

US2464508A - Salt bath furnace

Info

Publication number: US2464508A
Application number: US586649A
Authority: US
Inventors: Artemas F Holden
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-04-05
Filing date: 1945-04-05
Publication date: 1949-03-15
Anticipated expiration: 1966-03-15

Description

March 15, '1949'. A. F. HOLDEN SALT BATH FURNAGE Filed April 5, 1945 /ffegas F Ha/a'eh 2 Sheets-Sheet 1 INVENTOR .f ATTORNEY5 Maich l5, 1949. A. F. HOLDEN SALT BATH FURNACE 4 2 Sheets-Sheet, 2

Filed April 5, 1945 M d .w 4 MH M s E o VCI m. MM Wm L m l f mm Patented Mar. l5, 1949 UNITED STATES YPATENT OFFICE SALT BATH FURNACE Artemas F. Holden, New Haven, Conn.

Application April 5, 1945, Serial No. 586,649

The present invention comprises an improvement in salt bath furnaces of the character commonly used in heat treating of metals and which comprise a heat-insulated shell which supports and surrounds the side walls and bottom of a metal pot formed of suitable alloy to contain mlten salts at temperatures ranging up to 2250 F.

As the work, which is heat-treated in the molten salts within the 'potA is lifted from the pot, a small amount of the liquid salts will be dripped over the edge of the pot. These salts, in furnaces of the old well-known construction, tend to seep under the edge of the :pot and to travel .down-i ward on the outside of the pot between the pot and the heat-insulating material. This tends to cause erosion of the pot and thereby shortens the effective life of the pot container for the salts. The reason for this is due to the fact that heretofore in the art the upper portion of the pot is heated whereby the molten salts retain their fluidity and thus may escape beneath the rim of the pot, as specified.

The present invention overcomes the defects of the known prior art by providing a cooling area adjacent the mouth of the pot whereby any salts dripped over the edge of the pot are frozen, and thus their fluidity is destroyed and the seepage of the salt materials over the outside of the pot and between the pot and the heat-insulation is prevented. The preferred cooling arrangement comprises a hollow metal ring upon which the rim of the pot rests and through which hollow ring a cooling medium, such as air, water, steam, or other cooling medium, is circulated. The coolingmedium carries away the heat from the upper.

end of the pot and cools the same. Where air is used, the passage of the air through the hollow ring heats the air, and in a gas-red pot this air may be conducted to the gas burner, thereby sulpplying heatedair to the burner and consequently rendering the burner more eilicient in the heating of the pot.

Other and further objects of the present invention will in part be obvious and will in part be pointed out hereinafter in the descriptive matter following.

It is to be understood that the disclosure herewith is illustrative and is not to be interpreted in a limiting sense.

Fig. 1 is an illustration of a gas-red lfurnace in which the present invention is incorporated and wherein a portion of the furnace is shown in section.

Fig. 2 is a plan sectional view of the cooling ring taken on substantially line 2--2 of Fig. l and showing the ring detached from the furnace.

Fig. 3 is an elevational sectional View of the detail of the cooling ring taken substantially on y line 3-3 of Fig. 2 adjacent the partition in the ring.

Fig. 4 is a detail section illustrating thevmounting of a pot in the furnace adapted to be heated electrically and showing fire-proofing material substantially in contact with the pot.

Referring now more especially to Fig. 1 of the drawings which illustrates a gas-'red furnace in accordance with the present invention, a casing I supports heat-insulating material 2, which in a gas-fired furnace is spaced from the side walls ci a pot of suitable alloy metal in such manner as to tpovide a flame chamber 5 surrounding the po A melted salt bath 6 is contained Within the pot i and is the medium in which metallurgical articles are submerged for heat treatment. A burner 'I of the gas and air or oil and air type is mounted on the side of the casing i and a name opening 8 leads into the ilarne chamber The pot is supported upon a cooling member comprising a base plate 9, side walls lil and Il, and a top wall I2. These parts may be made of suitable metal and welded together to form a space I4. An inlet pipe I5 leads into the space I4 and an outlet pipe I6.

leads away from the hollow space. A partition Il, see Figs. 2 and 3, is provided between the inlet pipe I5 and the outlet pipe ISso that the-cooling medium is compelled to flow the ull length of the hollow space I4 before it reaches the outlet pipe. The upper end of the pot Il is provided with a ilange I 8 which rests upon the top wall I2 of the cooling member and the base plate 9 restson heat-insulating material which surrounds the pot. Where air is used as the cooling medium, the air outlet pipe I 6 leads through a controlvalve I9 to the burner 'I which is supplied by gas or oil through the pipe 20 leading to the burner 'I so that when the furnace is operating, the air circulating through the hollow space I4 becomes heated as it takes away the heat from the upper end of the pot and this heated Iair comprises the air supply to the burner I so that the burner operates more eiliciently than when cold air is drawn in directly from atmosphere. There may be conditions where it is desirable to divert a portion or all of the heated air away from the burner 1, and to this end an outlet pipe 24 is provided adjacent to the valve I9, which valve is so constructed as to deliver the heated air proportionally through the pipe I 6 to the burner 'l and through the outlet pipe 24, or all the heated air either to the burner 7, or to the outlet pipe 24. Another valve 25 is provided to permit air to be supplied to the burner 7, when the heated air is cut off from the burner 1. These valves I9 and 25 may be operated in any manner well-known in the art.

Surrounding the upper end of the pot with a cool surface causes any salts which may be spilled over the edge or flange of the pot to fall on this surface and to be congealed and hardened so that this waste salt loses its fluidity and does not tend to iiow or creep down the outside of the pot.

Referring now to Fig. 2, it will be noted that the space I4 is interrupted by baiiles 2| which cause the cooling medium, such as compressed air, to take a tortuous path and thereby cause a turbulent circulation of the cooling medium which absorbs heat from the inner side wall I and from the upper end of the pot, thereby cooling the same for the purpose specified.r The baffles 2| and the partition Il extend from the base plate 9 to the top wall l2 in order to reinforce the top wall and prevent the crushing of the cooling member due to the weight of the pot 4 when filled with the salt bath 6, which weight is augmented by the weight of metal objects in the bath undergoing treatment.

Fig, 3 illustrates the inlet pipe I5 and the outlet pipe l5 leading through the top wall l2 on each side of the partition l1, and where a cooling medium other than compressed air is used the outlet pipe I6 leads to a proper disposal means for the outlet cooling medium and in this case the outlet is not connected with the burner '1.

Fig. 4 is a detail view showing a portion of the side wall of the furnace adjacent the pot in seotion and illustrates an electrically heated furnace in which electrodes 22 extend into the salt bath B and passage of the current from the electrodes through the salt heats the bath. In an electrical furnace there is no necessity for a flame chamber around the pot, and, therefore, the heat-insulation is in substantial contact with the side walls of the pot. This produces a condition where seepage of salts may interlock the pot and the heat-insulating material. Under these conditions, severe erosion may occur to the alloy metal pot, and the present invention, therefore, overcomes a decided disadvantage of the known prior art.

The present invention is illustrated as used with a pot which is circular in horizontal crosssection, but since the invention is not concerned with the shape of the salt container, it is equally adapted to pots having shapes in horizontal crosssection other than circular and the invention tending within said heat insulation, a hollow cooling member surrounding the upper end of and supporting said pot and adapted to form a conduit through which a cooling fluid may be circulated to cool the upper end of said pot and prevent creepage of salt around the exterior of said pot, and baffles within said hollow cooling member to cause the cooling medium to take a tortuous path through said hollow cooling member, and reinforce said member against crushing.

2. In a salt bath furnace, a shell.' heat insulation Within said shell, a. salt bath metallic pot extending within said heat insulation, a hollow cooling member surrounding the upper end of and supporting said pot and adapted to form a conduit through which a cooling fluid may be circulated to cool the upper end of said pot and prevent creepage of salt around the exterior of said pot, and baffles within said hollow cooling member extending from the bottom to the top wall thereof to reinforce said member against crushing and cause the cooling medium to take a tortuous path through said member.

3. In a salt bath furnace, a furnace shell, heat insulation within and supported by the shell, a

salt bath container mounted within said heat in-V tainer, and an annular cooling ring for supporting and cooling the rim of the container, said cooling ring having a passage for conducting a cooling fluid therethrough, having an extended horizontal base supported by said heat insulation, having a horizontal upper containerrim supporting surface and having a circumferential inner marginal flange projecting above the 'container-rim supporting surface and between the container-rim and the container.

ARTEMAS F. HOLDEN.

REFERENCES CITED The following references areof record in the file of this patent:

UNITED STATES PATENTS` Number Name Date 1,539,924 Waite June 2, 1925 1,705,714 Carpenter Mar. 19, 1929