GB2109910A

GB2109910A - Furnace for heat treatment of metal articles

Info

Publication number: GB2109910A
Application number: GB08135169A
Authority: GB
Inventors: Edward Gething
Original assignee: SUNCOURT CONSTRUCTION Ltd
Current assignee: SUNCOURT CONSTRUCTION Ltd
Priority date: 1981-11-21
Filing date: 1981-11-21
Publication date: 1983-06-08

Abstract

The furnace has a chamber 24 with heating means and a lining of heat resistant material. The chamber is divisible into two compartments 34a, 34b by a partition 36 vertically movable by a pneumatic jack. Each compartment has a base conveyor 60a or 60b, a front loading door 46a or 46b, and a rear door 50a or 50b leading to vertically movable roller conveyor 69a or 69b over a quench tank. The furnace casing is formed of detachably mounted flat metal plates. <IMAGE>

Description

SPECIFICATION Furnace for heat treatment of metal articles This invention relates to a furnace for the heat treatment of metal articles.

For heat treatment of metal articles sealed quench furnaces are known comprising an outer casing shell formed by a one-piece casting of iron. Inside the shell is a furnace chamber provided with heating means and a furnace lining of heat resistant material. The chamber has a front or charging opening and a rear opening between which extends driven first conveyor means on which articles to be treated are loaded at the charging opening and carried into the chamber and after treatment are carried to the rear opening for discharge from the first conveyor means onto second conveyor means which may be driven and disposed in a housing over an oil bath.At least part of the second conveyor means is movable vertically by a jack device to submerge the articles on the second conveyor means in the bath and raise them again to permit their discharge from the housing through a discharge opening in line with other two. The charge, rear and discharge openings are provided with respective doors which are opened and closed by respective jack devices. The jack devices are operated by fluid pressure, for example compressed air. One or more electric motors are provided to drive the conveyor means. A circulating fan, driven by an electric motor, is usually provided in the chamber, and a propellor also driven by an electric motor is usually provided to circulate the oil in the bath. Usually a valve controlled conduit arrangement is provided to admit one or more gases into the furnace chamber for carrying out the heat treatment process therein.Normally some distance from the furance a control console or panel therefor is positioned from which the furnace chamber conditions and operation of various moving parts of the furnace can be controlled.

Such a known arrangement has a number of disadvantages.

(1) By forming the outer casing as a one-piece casting access to the furnace chamber interior can be difficult for inspection, maintainance or repair work, for example to replace the furnace lining, and may be restricted to access through the relatively small front or rear openings.

(2) The forming of the outer casing as a casting makes it relatively expensive. A form in the shape of the casing must be produced for use in making the mould which is only appropriate to one size of furnace and accordingly several forms of different sizes must be made each for'making a different sized casing corresponding to different sizes of furnaces required.

(3) The forming of the outer casing as a onepiece casting means the whole casing must be replaced should part of it become damage to the extent that operation of the furnace is impaired, and such replacement can be expensive and take a long time during which the costly furnace is not available for use.

(4) When production needs require different batches of metal articles to be simultaneously subjected to different heat treatments, a plurality of furnaces each with its attendant control panel, electric motors, gas supply piping and piping for pressurised fluid must be provided. Not only is it expensive to provide several furnaces but the space they occupy can be very large when passageways between them, clear areas to enable easy and efficient loading and unloading of the articles, and the sites for the control panels are taken into consideration, and the cost of providing the factory space can be considerable.

According to the invention 9 furnace for the heat treatment of metal articles comprises an outer casing within which is a furnace chamber having heating means and a lining of heat resistance material, movable partition means to divide the chamber into a plurality of compartments, and said outer casing comprising a plurality of metal plates.

The plates may be of steel.

The plates may be connected one to another. For example they may be directly connected one to another, or connected by attachment to supporting frame elements and/or by means of intermediate connection or coupling devices.

Preferably one or more of the plates are demountably mounted in position by releasable or disconnectable connection means, for example, screws, bolts or clamping means which can be undone to allow removal of one or more of the plates. Because the plates or at least one or certain ones can be removed this leaves one or more openings in the outer casing through which access may be gained to the interor of the furnace chamber to facilitate maintainance or repair work. Also if the or any particular removable plate becomes damaged or worn it may be quickly replaced by a new plate without necessarily requiring replacement of any other part of the outer casing. Thus the furnace need not be out of use for long.

Preferably the plates are substantially flat, notwithstanding that one or more may have a turnedout lip.

By forming the outer casing from plates it is not necessary to use expensive metal casting processes to form each casing. The outer casing may be relatively easily and cheaply formed simply but cutting stock plate to appropriate shape and, for example, drilling it to receive screws or bolts, and then screwing or bolting the plates together. If the or certain ones of the plates are secured to elements of a supporting frame the elements may be formed from standard steel bar stock cut to appropriate size and drilled to receive the bolts or screws. To form outer casings of different sizes, it is merely necessary to cut standard plate (and if required standard bar stock) to the sizes appropriate to form the required plates (and frame elements).

If desired the plates or a portion of the casing formed from one or more plates may be mounted on a frame or support structure formed of cast metal, for example cast iron, accordingly the frame or support structure may be a one-piece casting.

The movable partition means comprises one or more partitions movable into the furnace chamber to divide it into a plurality of separate compartments and removable from the chamber to enable adjacent compartments to merge. The compartments extend side by side along the furnace chamber. In the case of a furnace in which articles being heat treated therein are progressed through each compartment, the respective paths which the articles follow through the respective compartments extend side by side.

The partition(s) may be vertically movable, and may be lowered to divide the chamber.

Preferably the arrangment is such that when a or the partition is dividing two adjacent compartments one from another those compartments can be in substantially gas tight isolation one from another.

Thus appropriate seals, for example of graphite, may be provided between the partition(s) and the furnace lining to maintain one compartment in substantially gas tight isolation from another.

The furnace chamber is iined with heat resistant material, for example asbestos or refractory material, and is provided with suitable heating means for example electrical heating elements in grooves in the lining. The or each partition may also comprise heat reistant material which may be on the exterior of the partition. If desired heating means may also be disposed on or along sides of the partition(s) and may by movable therewith.

The casing can be formed with separate charging doorways leading into each respective compartment. The casing may also be formed with separate rear doorways leading from each compartment.

Each compartment may also be provided with respective first conveyor means to carry articles through the respective compartment.

Beyond the rear doorways, a housing may be provided containing an oil bath or quench tank providing a common quenching facilityfor articles treated in all the compartments.

A plurality of respective second conveyor means may be provided to receive articles from the respective compartments. These second conveyor means are disposed in the housing and at least part of each of these conveyor means may be vertically movable to lower articles thereon into the quench tank. The second conveyor means can convey articles between the rear doorways and discharge doorways leading from the housing.

Doors at the charging and/or rear and/or discharging doorways may be/openable and closable under power means, for example by pneumatic or other fluid powered jacks. The doors can be a gas-tight fit when closed.

Respective inlets for gases may lead into each compartment, and the gas supply to each compartment may be regulated individually. Also the heating means associated with each compartment may be regulated separately from the heating means of any other, and each compartment may have its own temperature sensing and control means. Thus it is possible in a single furnace to maintain in the different compartments different temperatures and gaseous atmospheres corresponding to different treatment processes which can be carried out simultaneously on the different batches of articles in the respective compartments. Also treatments beginning or ending at different times can be carried out in the different compartments simultaneously, and a compartment can be loaded or unloaded through an open doorway without adversely affecting the temperature in any other compartment.

The temperatures attained in the compartments, the operation of doors and conveyor means and duration of heat treatment cycles in the different compartments may all be controlled from a common control panel or console.

It can take a relatively long time to raise the temperature in a given compartment from cold to the appropriate heat treatment temperature. This time may be reduced by moving the or a said partition to allow the hot atmosphere from a previously heated compartment to enter the adjacent compartment it is desired to bring into use.

If desired an additional doorway, closable by a door which can be a gas-tight fit, may be provided in a side of the casing to allow large articles to be placed into two more communicating compartments when the partition(s) therebetween is/are moved from the chamber. The temperature and or atmosphere in such communicating compartments can be maintained at appropriate condition for the desired treatment, for example for relieving stress in the articles.

If desired means may be provided to evacuate each or any of the compartments so as to establish at least a partial vacuum therein of a desired degree.

Although the furnace described above is primarily for the heat treatment of metal articles, it may also be used for the heattreatment of plastics articles for example to relieve stresses in moulded plastics, articles.

The invention will now be further described by way of example with reference to the accompanying drawings in which: Figure 1 is a diagrammatic and fragmentary perspective view of an embodiment of a sealedquench furnace formed according to the invention; Figure 2 is a diagrammatic and fragmentary horizontal cross-section through the chamber of the furnace in Figure 1; Figure 3 is a diagrammatic and fragmentary vertical cross-section through a compartment in the chamber of the furnace in Figure 1, and Figure 4 is a view similar to Figure 1 of a modification of the furnace in Figure 1.

In the drawings like references refer to like or corresponding parts.

Referring to Figures 1 to 3, the sealed-quench furnace 2 has an outer casing 4 formed by flat steel plates some of which are shown at 6,8,10,12 14 and 16 which are removably bolted in place by screws or bolts 20. The plates or at least some may be bolted to a supporting frame (not shown) inside the casing or to connecting elements, for example bars, and/or may be bolted one to another. For example, since the plate 8 overlaps end edges of the plates 6 and 10 tapped bores parailel to the main faces of plates 6 and 10 may be drilled into those end edges to receive the bolts passing through bores in the plate 8.

The aforesaid casing is detachably attached by screws or bolts to a base plate 22 or base plates of the furnace chamber 24, which base supports lower furnace lining 26a, 26b.

A base support for the furnace chamber may be formed by or include further plates such as shown at 28,30 and 32 (Figure 1) detachably secured in place.

The furnace chamber can be divided into two compartments 34a and 34b by a partition 36 raisable and lowerable into the chamber by a pneumatic jack 38 on a housing 40 which receives the raised partition, which housing can be detachably secured on the plate 6 and can itself by formed of plates detachably secured in place.

The partition 36 slides in grooves in front and rear furnace linings 42 and 44 and in lowered position sits in a slot between lower linings 26a, 26b. Suitable sealing means are provided to provide a seal about the periphery of the partition 36 such that when the partition is lowered compartments 34a and 34b are in substantially fluid tight isolation one from another.

Each compartment has a respective loading door 46a and 46b movable by pneumatic jacks 48a and 48b, and a rear door 50a or 50b movable by pneumatic jacks 52a or 52b on housing 54 which may be formed by plates detachably secured in place.

Sides of the compartments are lined by furnace linings 56a and 56b as are the ceilings such as shown at 58a.

In the base of each compartment is a chain conveyor 60a and 60b with its two side chains interconnected by bars and the chains passing around sprockets, for example at 62a and 62b in Figure 3, at least one of which is driven by a first electric motor (not shown).

Directly behind the compartments is a common quench tank 64 covered by a housing 66 each of which may be formed by demountably secured plates. Behind each conveyor 60a, 60b is a further conveyor 68a, 68b of rollers 69a or 69b which may be driven by an electric motor (not shown). Each conveyor 68a, 68b is lowerable into the tank 64 and raisable by a respective penumatic jack 70a, 70b.

The quench tank may contain a driven circulation propellor.

The housing 64 is equiped with discharge doors 72a, 72b movable by pneumatic jacks 74a and 74b.

Each compartment, as exemplified by compart ment 34a, can have a respective circulation fan (for example the fan 74a driven by electric motor 76a).

Also each compartment can have a respective gas supply conduit (as exemplified by conduit 78a to compartment 34a) provided with control valve means (not shown). A common gas supply may be available to each conduit.

A common air pressure line can be provided to distributor valve means controlling air supply to the pneumatic jacks.

A common electric motor can be provided to drive selectively operable transmissions powering both conveyors 60a and 60b.

A control panel (not shown) can be provided to control operation of the pneumatic jacks, the electric motors and the temperature in each compartment, and may control a pre-determined heat treatment cycle in each compartment or in the chamber when the partition is raised.

In addition to the advantages mentioned previously it should be noted that the furnace described above takes up less floor space than a plurality of known furnaces. Only one motor need be provided to drive two conveyors 60a and 60b. Less piping leading compressed air and other gases is needed to one furnace with a number of compartments than when several known furnaces are used, and the same is true for the amount of electric cable providing the electric supply to a single furnace as described or transmitting electric signals therefrom to a control panel. And although when the partition is lowered, the furnace described can act as two furnaces, only one quench tank is needed.

The furnace in Figure 4 has in the side of the casing an additional doorway covered by a door 80 movable buy a pneumatic jack 82 enabling large articles to be placed in the furnace chamber when the partition is raised.

Claims

1. A furnace for the heat treatment of metal articles comprising an outer casing within which is a furnace chamber having heating means and a lining of heat resistant material, movable partition means to divide the chamber into a plurality of compartments, and said outer casing comprising a plurality of metal plates.

2. Afurnace as claimed in Claim 1, in which there is at least one partition movable between first and second positions such that in the first position the partition divides at least a portion of the volume of the furnace chamber into adjacent compartments disposed side by side separated by said partition, and with the partition in the second position said adjacent compartments are open one to another through a region which is occupied by the partition when in the first position, a plurality of openings is formed in the same side of the casing, each opening leading to a respective said compartment and each opening is openable and closable by a respective movable door.

3. Afurnace as claimed in Claim 2, in which the first mentioned openings are in a front side of the casing and are changing openings through which articles to be treated can be loaded into the respective compartments, a plurality of second openings is formed in an opposite rear side of the casing, each second opening leads from a respective said compartment such that articles treated in said compartment can be unloaded therefrom through the corresponding second opening, and each second opening is openable and closable by å respective movable door.

4. Afurnace as claimed in Claim 2 or 3, in which each compartment is provided with respective conveyor means movable to convey said articles in the compartment.

5. A furnace as claimed in any one of Claims 2 to 4, further comprising a quench tank common to more than one of said compartments whereby articles previously heat treated in at least two compartments can be immersed in said common tank.

6. Afurnace as claimed in any one of Claims 2 to 5, in which an additional opening formed in a side of the casing leads into a said compartment such that articles to be heat treated can be loaded into or unloaded from the interior of said furnace through said additional opening in a direction transversely to the direction of loading or discharging through said previously mentioned openings, and said additional opening is openable and closable by a movable door.

7. Afurnace as claimed in Claim 3 and Claim 6 in which said additional opening is formed in a side of the casing extending between said front and rear sides.

8. Afurnace as claimed in Claim 1, in which the partition means is vertically movable.

9. Afurnace as claimed in anyone of claims 2 to 7 in which the partition is vertically movable.

10. Afurnace as claimed in any one preceeding claim, in which one or more of said metal plates is/are removable from its/their mounted position(s) on the furnace.

11. A furnace as claimed in Claim 10, in which a said removable plate is mounted in position using releasable clamping means.

12. Afurnace as claimed in Claim 8, in which a said removable plate is mounted in position using releasable screws or bolts.

13. Afurnace as claimed in Claim 10, in which at least one removable plate is releasably screwed to another removable plate.

14. Afurnace as claimed in Claim 10, in which the removable plates are mounted on a frame.

15. Afurnace as claimed in Claim 10, in which the removable plates are mounted on a support of cast metal.

16. Afurnace as claimed in any one of the preceding claims, in which a plurality of said plates are substantially flat.

17. Afurnace as claimed in any one of the preceding claims, in which each compartment is provided with respective temperature control means to control the temperature in that compartment.

18. Afurnace as claimed in any one of the preceding claims, in which each compartment is provided with respective gas supply means whereby a gas or gases to form a metal treatment atmosphere in said compartment can be supplied thereto.

19. Afurnace as claimed in any one of the preceding claims, in which a common control panel is provided to control heat treatment processes performed using any of the compartments.

20. A furnace for the heat treatment of metal articles substantially as hereinbefore described with reference to Figures 1 to 3 or Figures 1 to 4 of the accompanying drawings.