US2931636A

US2931636A - High temperature heat treatment of metals

Info

Publication number: US2931636A
Application number: US721724A
Authority: US
Inventors: William E Engelhard
Original assignee: Individual
Current assignee: Individual
Priority date: 1958-03-17
Filing date: 1958-03-17
Publication date: 1960-04-05
Anticipated expiration: 1977-04-05

Description

Aprxl 5, 1960 w. E. ENGELHARD HIGH TEMPERATURE HEAT TREATMENT OF METALS Filed March 17, 1958 2 Sheets-Sheet 1 di .'T p- ATTORNEY April 5, 1960 w. E. ENGELHARD 2,931,636

HIGH TEMPERATURE HEAT TREATMENT oF METALS Filed March 17. 1958 2 sheets-sheet 2' ATTORNEY man TEMPERATURE HEAT TREATMENT F METALS William E. Engelhard, Apalachn, N.Y.

Application March 17, 1958, Serial No. 721,724 lz claims.v (cl. zes- 41) This invention relates to the heat treatment of metals at high temperatures. One of the difficulties encountered in high temperature heating of parts in furnaces .is that there is a tendency for the atmosphere to filter through to the parts being heat treated, forming oxides and impurities thereon. Substantial seepage of the atmosphere into contact with the parts, frequently encountered in conventional high temperature heat treatment procedures, called a high dew point is a serious shortcoming.

Pursuant to this invention, the parts may be safely heat treated in a casing made of relatively inexpensive metals such as iron, the parts being swept by hydrogen gas under pressure which then passes outwardly and into the atmos-y phere so that the inner casing and the parts therein are maintained at all times in a gaseous bath which prevents seepage and flow of atmospheric air and maintains a low dew point condition in the casing containing the parts. Pursuant to the invention, the parts to be heat treated mayl thus be heated and brought to the desired temperature without contamination.

Examples of practical devices embodying the invention` are described below Vand in the accompanying drawings; the invention is not limited thereto, but covers all other forms coming within the scope or purview of the disclosure herein.

In the drawings:

Fig. 1 is a vertical longitudinal sectional, partly fragmentary view of ahigh temperature furnace for treating parts, embodying the invention, arrows showing the path of the gas sweeping the parts and thence passing over the outer-'wall of the inner casing and between said outer wall and the inner wall of the enclosing rst casing and thence into the atmosphere,

Fig. 2 is a vertical sectional view thereof, taken at line 2-2 of Fig. 1,

Fig. 3 is a partly fragmentary, elevational view, taken at line 3--3 of Fig. l,

Fig. 4 is a partly fragmentary view of a casing which may be used in carrying out the invention,

Fig. 5 is a fragmentary, sectional view of an inner casing used in carrying out the invention, and

Fig. 6 is a fragmentary, elevational view of a form of casings embodying the invention.

In Fig. 1 the invention is shown applied to a high temperature furnace 10 having a rear wall 11, and longitudinally elongated wall means 12 extending forwardly therefrom, in this instance comprising a top wall and bottom and side walls, but, which may be rectangular, circular or any other desired or convenient form cross sectionally, defining an elongated recess 13 open at the front 14 of the furnace and defining an open front face thereat. The furnace may be provided with electric heater elements 15 or any other desired or convenient source for heating the recess 13 and thereby heating the parts 16 positioned therein. A door 17 is adapted to be positioned against the open front 14 of the furnace, to close the same as shown in Fig. 1. Door 17 may be provided with a bracket 1 8 to which a cable 19 may be affixed for moving the door ji y ired States arent 'ige against and away from the front 14 of the furnace; counterbalance weights 20 may (Fig. 3) be secured tothe cable 19 entrained over pulleys (not shown).

Pursuant to the invention, a novel chamber apparatus is provided for insertion into the furnace recess 13 through the open front 14 of the furnace for holding the work p casing 24, in this instance also comprising a top wall 25 and bottom and side walls all longitudinally elongated, and a front end plate 26 rigidly secured thereto, as by welding at 27, providing a gas tight seal. The wall means of the second casing is slightly shorter than the top, bot-V tom and side wall means of the first casing so that (Figs. 4 and 6) said casings may be secured together with the front end of the irst casing secured to the end plate 26 of the second casing, the side Walls of the casings then defining therebetween a constricted, elongated passageway 32 (Fig. 1), the free end 33 of the second casing 24 then defining with the rear wall of the first casing a passageway for gases passing through the second casing 24 from a source 34 (presently described) and then through the elongated passageway 32, and, as noted by the arrows in Fig. l, between the door 17 and front end 14 of the furnace 10 and to the atmosphere. The outer casing preferably is made of a heat resistant alloy, such as Nichrome or Inconel, While the inner casing 24 may be made of iron.`

length 40 (Fig. l) substantially greater than its height 42- (Fig. 2) the

casings

21, 24 being so proportioned that the space between the side walls ofthe casing, indicated by the arrows 43, Fig. 2, is a fraction of the height of the inner casing so that gas pumped under pressure through the pipe 34 and thence through the second casing 24 (arrows Fig. 1) will blanket the parts 16 therein and pass intermediate the open rear end of second casing and the end of the first casing and thence at 32 intermediate the casing side walls and through the front end 14 of the furnace, rapidly discharging to the atmosphere and maintain ing a low dew point in the inner casing 24 containing the parts being treated. A slip coating 28 may (Fig. 5) be applied to the side wall member of the second casing 24 to prevent the work from adhering thereto.

In practice, the furnace 10 is preferably disposed horizontally as, for example, indicated in Figs. 1 and 2 by the horizontal surface 44, and the parts 16 are positioned in the second casing 24 and then the first casing 21 secured to the end plate 26 of the second casing, as for example, by the use of bridge members such as shown in Fig. 6 at 45 and in Fig. 4 at 45', said bridge member being welded at opposite ends to the end plate 26 of the second casing and to the first casing, with a substantial portion of the bridge member extending therebetween (Fig. 6) or being formed as bolts passed through extensions or plates on the end plate 26 and first casing 21 (Fig. 4). The parts 16 are positioned in the second casing and then the casings secured together and inserted into the furnace recess 13;

the parts are maintained in the blanket of gas supplied through the source 34, while being treated.

In the drawings (Fig. 1), the second casing is shown provided with protuberances 46 at the bottom thereof which serve to space the bottoms of the first and

second casings

21, 24 maintaining the constricted elongated gas passageway 32 completely around the second casing 24. The parts 16 and the outer face of the second casing 24 will be continuously washed with gas during the heating operation and any ambient gas which sought to breathe through or permeate the casings would be swept out of the furnace by the gas from source 34 pumped into the second casing 24 under pressure. The door 17 is positioned against the front end 14 of the furnace 10 as shown in Fig. l and, although in practice the fit may be an accurate one, gas from source 34 sweeping over parts 16 and thence more rapidly through the constricted space 32 between the casings will escape (arrows, Fig. 1-) between the front 14 of the furnace 10 and the door 17 and into the atmosphere.

After the parts have been heat treated to a sufficient degree in the furnace, the casings may be withdrawn and the bridge members such as 45, 45' cut to separate the casings. The bridge members 45, 4S may be dispensed with by otherwise connecting or directly welding the first casing to the second casing but the provision of bridge members or their equivalent provides a convenient means for readily separating the casings. If desired, a heat insulating gasket 47 may (Fig. 5 be positioned on the inner face of the end plate 26 of the second casing.

If` in use the free end of the first casing becomes separated to an appreciable degree from the end plate 26 of` the second casing, a gasket 48 (Fig. 6) may be stuffed between the front of the first casing and the end plate of the second casing.

Gaskets

47, 48 may be made of any suitable or desired material such as silicon carbide wool.

The door 17 may be provided with a recess 49 (Figs. 1v and 3) to permit the door to be slid down over the pipe 34, or a two part door may be provided to close around said pipe. The pipe 34 may be connected to a source 50 (Fig. 3) of another gas such as CO2, argon, nitrogen or other desired gas for flushing the interior of the second casing 24, connected to the T 37 through a valve 51.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. An elongated high temperature heat treating furnace to be horizontally positioned on a supporting surface in parallel relation thereto comprising a rear wall and longitudinally elongated wall means extending forwardly therefrom, defining an elongated tubular recess in, and terminating in a free edge defining an open front face of, the furnace, said recess extending from the open front face to the rear wall interiorly thereof, an elongated first casing having an end wall slightly smaller than the furv nace wall in dimensions transverse to the furnace, and first casing tubular wall means extending forwardly therefrom and of less length than the furnace'recess, said first casing to be inserted into the furnace recess with the free end of its wall means substantially in the plane of the front face of the furnace, and a second casing comprising an end plate as large as the open front face of the first casing and second casing tubular wall means secured to the end plate and of slightly less length and cross sectional dimensions than the first casing, the lower portion of said last-mentioned wall means to support the partsvto be heat treated in the furnace, the free edge of the first' casing being slightly spaced from and secured to the end plate of the second casing, a gas pipe secured to said end plate in registry with an aperture provided in said plate, for passage of gas under pressure into the second casing and thus over the parts therein and through the restricted, long passage defined by the wall means of the casings and thence laterally past the front face of the furnace, a door positioned against the front face of the furnace and against the end plate of the second casing, and slotted to clear the pipe and allow the door to slidably move laterally relative to the front face of the furnace.

2. In a furnace as set forth in claim 1, said first casing being made of heat-resistant material, and a bridge member fixed to the end plate of the second casing and to the wall means of the lfirst casing adjacent the free end thereof, holding said end plate andfirst casing in abutting relation.

References Cited in the file of` this patent UNITED STATES PATENTS 446,947 Land Feb. 24, 1891 1,333,225 Stewart Mar. 9, 1920 1,997,680 De Coriolis et al Apr. 16, 1935 2,124,764 Comstock July 26, 1938 2,480,293 Hulme Aug. 30, 1949 2,744,745 Engelhard May 8, 1956 FOREIGN PATENTS 666,965 Germany Feb. 24, 1891