US3565410A

US3565410A - Vacuum furnace

Info

Publication number: US3565410A
Application number: US757850A
Authority: US
Inventors: George E Scherff
Original assignee: Midland Ross Corp
Current assignee: Midland Ross Corp
Priority date: 1968-09-06
Filing date: 1968-09-06
Publication date: 1971-02-23
Anticipated expiration: 1988-02-23
Also published as: GB1235964A

Abstract

This invention relates to a vacuum furnace of the type wherein a gas is circulated during the cooling portion of the heat treat cycle. The heat treat chamber of the furnace is provided with shields having reflective surfaces disposed within the passageways that allow ingress and egress of the cooling gas. The reflective shields are so disposed that heat is reflected back into the heating chamber during the heating portion of the cycle, but there is no obstruction of the circulation of the furnace atmosphere during the cooling portion of the cycle.

Description

United States Patent 3,565,4 l0 [72] Inventor George E. Seherfl 5 References cited BMmg Ohm UNITED STATES PATENTS [21] Appl. No. 757,850

- 3,163,694 12/1964 Ipsen 266/5 [22] Flled Sept. 6,1968

Patented Feb Glenn 219 331 11/1965 Ipsen 266/5 [73] Assignee Midland-Ross Corporation Toledo, Ohio Primary Examiner-Gerald A. Dost Attorneys-Peter Vrahotes and Harold F. Mensing ABSTRACT: This invention relates to a vacuum furnace of the type wherein a gas is circulated during the cooling portion of the heat treat cycle. The heat treat chamber of the furnace [54] E. is provided with shields having reflective surfaces disposed alms rawmg within the passageways that allow ingress and egress of the [52] US. Cl 266/5, cooling gas. The reflective shields are so disposed that heat is 263/40 reflected back into the heating chamber during the heating [51] Int. Cl. C2ld 1/00 portion of the cycle, but there is no obstruction of the circula- [50] Field of Search 266/1, 2, 5, tion of the furnace atmosphere during the cooling portion of 56; 263/40 the cycle.

PATENTEUFYEBQSIHYYI I 1 0 INVENTOR. 366 E. 50152- cle.

1 VACUUM FURNACE With the increased demands placed upon materials in the metallurgical field, the vacuum furnace has increased in usage. One type of vacuum furnace which has particular utility in the heat treating of metals is cold walled vacuum furnace havingmeans for circulating a gas atmosphere across the work- Vacuurn furnaces of the type underdiscussion normally have wall means defining a heat -treating enclosure that completely encloses a space eitcept for a pair of opposed openings within the walls through which gas is allowed ingress and egress. A cover is placed across,'or' in close proximity of,

these openings so that a large quantity of heat will not pass therethrough, but will be reflected back. into the heat treating enclosure by the covers. If the covers are too close to the openings, the gas flow will be too restricted; whereas, if a cover is placed a relatively large distance away from the opening to allow free gas flow, too much heat is lost. Usually a compromise position is chosen and, like most compromises, is not the best solution. An attempt has also been made to overcome the two-fold problem by having a movable cover; however, at the temperatures at which the fumace is operated, the mechanisms used to move the cover are expensive and subject to need of frequent maintenance. In order to overcome these problems, it has been found that placing a plurality of reflective shields within the opening of the heat treating enclosure will allow a large amount of heat to be'reflected back into the heat treating area without interfering with the flow of cooling gas. I. t 1

In the drawings: v

FIG. 1 is a partially cross-sectional view of a vacuum furnace incorporating the features of the instant invention.

FIG. 2 is a detailed 'view of an opening of the heating enclosure showing an alternative embodiment.

Referring now to the drawing, a cold walled heat treating vacuum furnace is shown generally at and has a metal case- 12 supported by legs 13. The case l2 has an interior jacket 14 and an exterior jacket 16 which define a channel through which water is passed during theoperation of the furnace in order to keep the case cool. The metal case 12 has a plurality .of openings including an upper opening 18 and a lower open- .the lower opening 39. Each of the

covers

40 and 42 has a reflective surface 41 facing the enclosure which surface is backed by an insulating material 43'. The heating elements 26 and 28 extend into the enclosure-30 at the upper and lower portions thereof, respectively. Disposed within each of the compartment openings 36 and 38 is-a plurality of reflective shields 44. e

Mounted on top of the case 12 is a motor 46 that drives a fan 48 located within the case 12 through a shaft 50 which sealingly extends through the case. Located intermediate the fan 48 and the top of the enclosure 30 is a shroud 52 which from the diffusion pump 60 is'a line 62 that communicates with a mechanical pump 64. A gas line 65 is attached to the duct 58 so that cooling gas may be supplied to the case 12.

Located within the enclosure 30 are support members 66 that are adapted to support work 68 which is to be heat treated. l

In operation, work 68 is placed upon the supports 66 of the enclosure 30 and a vacuum is pulled within the case 12 through the use of the mechanical pump 64 and a difiusion pump 62. After a sufficiently high vacuum is pulled, the heating elements 26 and 28 are activated and the work is heated to the desirable temperature for the particular heat treating cycle. ln furnaces of this type, the work'68 may be heated to temperatures ranging from 500to 2,500 F. After the heating cycle is complete, the heating elements 26 and 28 are turned off and the vacuum pumps 60 and64 are inactivated. An atmosphere is introduced into the case through the line 65, and, after a sufficiently high pressure is obtained within the case 12, usually ambient, the fan 48 is activated. The cooling gas may be nitrogen, argon, or any other suitable gas. Simultaneously with this, water is passed through the cooling coils 54 so that as the cooling gas is circulated, it flows past the cooling coils. The cooling gas flows through the fan between the walls of the case 12 and the enclosure 30, through the opening 38, across the work 66, through the opening 36, and past the fan 48, where the cycle is repeated.

Having the shields 44 located within the openings 36 and 38 allows a large amount of the radiant heat within the heating enclosure 30 to be reflected back into the enclosure during the heat treating portion of the cycle. The shields are made of a high temperature metal such as stainless steel or molybdenum and the surfaces are kept clean. The presence of these shields allows the

cover

40 and 42 to be placed at a distance relatively great from the openings without the loss of too large an amount of heat. The radiation that is leaving the enclosure through the openings 36 and 38 in a vertical direction will be reflected back into the enclosure by the reflective surfaces 41 of the

covers

40 and 42. The bulk of the radiant heat that tends to pass through the openings 36 and 38 at an angle will be reflected back into the enclosure 30 by the shields 44. After the heat treating cycle is completeJhe shields do not interfere with the flow of cooling gas since they occupy such a small area, and the interference by the covers is reduced because of the increased distance from the openings 36 and 38.

The shields 44 may be placed in a vertical position, as shown in FIG. 1, or in any other suitable angle that would conform to the geometry of the enclosure. An alternative embodiment is shown in HQ 2 wherein the shields 44A are placed at a slight angle relative to the vertical. This alternate arrangement would be advantageous in use with an enclosure 30 having greater width than height.

lclaim:

1. In a vacuum furnace, the combination comprising: first wall means defining a chamber, second wall means disposed within said'chamber and defining an enclosure, said second wall means having a pair of openings therein, means for selectively' supplying heat to said enclosure, means for selectively creating a vacuum in said chamber, means for selectively providing a gaseous atmosphere to said chamber, a cover disposed within said chamber and spaced relative to each of provides a passageway between the opening 36 and the fan 48.

Located within and about the shroud are a plurality of cooling coils 54. The cooling coils are made of ahigh temperature am material and are adapted to receive watertherethrough after the heat treating portion of the cycle.

said openings, at least one reflective shield disposed in the vicinity of each of said openings, and means for directing the atmosphere through said openings of said chamber.

2. The vacuum furnace of claim 1 wherein said openings have a plurality of reflective shields therein, said shields being aligned in a generally outwardly direction from said enclosure.

3. The vacuum furnace of claim 2 wherein said shields are at a slight angle relative said outwardly direction.

Claims

1. In a vacuum furnace, the combination comprising: first wall means defining a chamber, second wall means disposed within said chamber and defining an enclosure, said second wall means having a pair of openings therein, means for selectively supplying heat to said enclosure, means for selectively creating a vacuum in said chamber, means for selectively providing a gaseous atmosphere to said chamber, a cover disposed within said chamber and spaced relative to each of said openings, at least one reflective shield disposed in the vicinity of each of said openings, and means for directing the atmosphere through said openings of said chamber.