US2638334A

US2638334A - Furnace for the heat treatment of materials

Info

Publication number: US2638334A
Application number: US173399A
Authority: US
Inventors: Jones John Frederick Robert
Original assignee: Individual
Current assignee: Individual
Priority date: 1948-01-29
Filing date: 1950-07-12
Publication date: 1953-05-12
Anticipated expiration: 1970-05-12

Description

May 12, 1953`- J. FXR. JoNEs 2,638,334

v FURNACE FOR THE HEAT TREATMENT OF MATERIALS Filed July 12, 1950 l 4 Shees-Sheet l llll i 'n .-l

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y I Afro/wr- May 12, 1953 J. F. R. JONES 2,638,334

FURNACE FOR THE HEAT TREATMENT OE MATEEIALS Filed July 12, 195o 4 sheets-sheet 2 FIGZ Ma'y '12, 1953 J. F. R. JONES FURNACE FOR THE HEAT TREATMENT OF MATERIALS Filed July 12, 195o 4 Sheets-Sheet 3 .//H T E.: o. n

FURNACE RoR THE HEAT TREATMENT 0F MATERIALS Filed July 12, 195o J. F. R. JONES May l2, 1953 4 Sheets-Sheet 4 ULT o elle.'

:l TNA Patented May .112, i953 FURNACE FOR THE HEAT TREATMENT OF MATERIALS John Frederick Robert Jones, Shotton, England Application July 12, 1950 vSerial No.,1'73,3`99 In Great Britain January 29, 1948 (Cl. 26S-40) 4 Claims. l

This invention has reference to furnaces for the heat treatment of materials and is more particularly concerned with those of the soaking pit or like type wherein metal ingots or other work pieces to be heat treated 'are inserted into a treatment chamber through a vcharging aperture in the top of the furnace on to the hearth of the lsai-d chamber, the charging aperture then being closed byva removable cover'. The principal object of the present invention is to enable the whole of any batch of work un dergoing treatment to be heated uniformly to a predetermined 'temperature in a minimumperiod of time by minimizing the` velocity of the ow of hot gases within the treatment chamber and rendering such flow uniform throughout the chamber. l

A further object of the invention, when ap plied to gaseous or liquid fuel ired furnaces, is to obviate burning the work by flame impingement, and to ensure that the fuel is completely combusted, so that all potential heat is converted intor sensible heat, before the hot combustion products reach the work.

In accordance with the said invention, an exhaust vchamber is formed within the furnace structure between the treatment ychamber and theinlet to a flue through which the waste gaseous products are discharged, one end, which is of generous cross-sectional dimensions, of the said exhaustchamber opening wholly and directly to the interior of the treatment chamber, whereas its opposite end is closed except for the said flue inlet, the arrangement being such that the rate of ilow of the hot gases within the work receiving zone of the treatment chamber is substantially equal tothek natural speed of `convection, and that no -local increases in thevelocity `of the hot gases are created within the said Zone under the iniluence of the suction Iexisting at theueinlet.

Preferably the vopen end ofthe exhaust chamber extends between-the opposite lsides of the treatment chamber and from the furnace hearth to a position substantially midway between the said hearth and the charging orice of the treatment chamber; the depth oi" the said exhaust chamber may be substantially uniform from its open end to its closed end, whereas its width may decrease gradually.

The work heating gases may be fed to and transversely of the treatment vchamber through an orifice formed in the treatment chamber wall directly above Athe open end of the Aexhaust fchambenthe said gas `orifice forming the vopen end of a combustion chamber in the opposite closed end of which burners are located. The said combustion chambermay be of substantially uniform area between its open and closed ends, which area 'may be equa-1 to the area of the `open end of the exhaust chamber.

In order that the invention may be more readily understood and carried into practice, reference will now be made to the accompanying drawings, wherein:

Figure l is a sectional elevation of a rectangular soaking pit, and

'Figures 2, 3, 4 and 5 are sections taken along the lines A-A, B-B, C--C and D-D, respectively, shown in Figure 1.

The soaking pit consists of a treatment chamber I of rectangular cross section and having an open upper end which serves as' the charging and discharging orice for ingots '2 (indicated in chain dotted lines in Figure l) the floor orbed of the said chamber is covered with a layer 3 of coke breeze which serves as a removable hearth on which the ingots are seatedon end when charged into the furnace.

'When a batch' ofingots is undergoing heat treatment, the open upper end of the treatment chamber is closed by a 'hat removable cover Il which seats upon the rim of thel chamber orifice and is provided 'along the underside of its four edges, with a continuous depending ange or skirt `5 'which extends into a sand or liquid filled trough 5 in the furnace structure to proa vide a lgastight seal between the cover and furnace structure. y

Two superimposed chambers 1 and 8 open into thetreatment .chamber I at one end of the latter. I

The lower chamber l, at its open end, extends across the width of the treatment chamber between the side walls `9 and Hi, whereas, at 'its closed end, a flue l'l opens intothe said lower chamber through the floor thereof, the said flue communicating with `a stack, chimney or equivalent discharge outlet for waste gaseous products and being controlled by ail-adjustable damper l2. The chamber l thusl serves as an exhaust chamber.

The floor of the exhaust chamber is flush with the removable hearth 3 'and its :arched roof i3 is located at a position wich is more lor less midway between the saidhearth and the top or mouth of the treatment chamber. The exhaust chamber is-substantially uniform `in height from its open fend to its opposite closedend but its width gradually decreases from the said `operi end to the gas inlet end of the nue Il (see Figure 3) The open end of the upper chamber 8, hereinafter referred to as the `combustion chamber, has yan area equal to the area of the open end of the exhaust chamber; the said combustion chamber end also extends transversely of the treatment chamber between the side walls 9 and l0 and, therefore, its height is also .more or less equal to half the height of the treatment charnber l. However, the combustion chamber differs from the exhaust chamber in that it is of uniform area between its open and closed ends and in that the end wall I4 thereof is formed with three holes I5 through each of which a burner I6 res into the combustion chamber.

The height of the treatment chamber is conbe seen from Figure l, the dimensions of the three chambers are such that, when a charge of ingots is positioned upon the hearth 3, their up-` per extremities do not project above the roofv vI3 of the exhaust chamber. l

Hence, when a charge of ingots is being heated, a space of considerable ydepth exists between the tops of the ingots yand the underside of the cover 4; this `space and the interior of the com- Ibustion chamber 8 forms a single large combustion zone wherein com-plete combustion of the fuel takes place, and all potential heat available in the fuel is convertedinto sensible heat. In this manner, burning of the ingots by the direct impingement of flames, is prevented and, more over, when the h'ot products of combustion flow downwardly of the treatment chamber into the lower work containing zone of the said chamber, they are at their maximum temperature.

The cross sectional area of the .treatment chamber is such that the velocity of the downwardly moving combusted gases is substantially equal to the natural speed of convection, namely in the region of three to four feet per second. Also, the pro-vision of the exhaust chamber between the work containing zone of the treatment chamber and the inlet to the ue Il, ensures that the said downward gas flow is not influenced by the suction createdat the said flue inlet; therefore the hot products of combustion flow `at a uniform speed throughout lthe cross-sectional area of the treatment chamber and each and every portion of the exposed surfaces of the ingots is subjected to the same heat treatment since there is little or no tendency for the gaseous products to ow along other than a verticalv path. Further, due to the low velocity of the combustion products within the work containing zone of the treatment chamber, the ingot temperature is the principal factor which determines the direction of flow within the said zone; therefore, should any part of the charge of ingots (for example, that part which is furthest from the open end of the combustion chamber) become heated to a lesser degree than the remainder of the charge, this temperature difference causes more of the hot products to flow over the said cooler part.

Iclaim:

1, In Ia soaking pit furnace or the like for the heat treatment of ingots and `other work pieces, in combination, a treatment chamber having a hearth, an exhaust chamber contiguous to said treatment chamber 'and having 'an open end opening directly into said treatment chamber along one side thereof, said open end extending upward1y,.from.:adjacent said hearth to a height generally as great normally as the height of the Work-receiving portion of said treatment chamber, said open end further extending substantially across the full width of said side, a ue connected to the other end of said exhaust chamber, said open end having an `area greater than the area of said flue, said exhaust chamber further decreasing in cross-sectional Iarea in a direction toward said flue such that the velocity of the waste gases passing through said exhaust chamber is increased Within said exhaust chamber, and means for combusting and reducing the velocity of the gases for heating said furnace substantially above said Work-receiving portion.

2. In a soaking pit furnace or the like for the heat treatment of ingots and other work pieces, in combination, a treatment chamber having a hearth, an exhaust passage contiguous to said treatment chamber and having lan open end opening directly into said treatment chamber along one sidethereof, said open end extending -upwardly from adjacent said hearth to a height generally midway of the height of said treatment chamber, said open end further extending substantially across the full width of said side, a flue connected to the other end of said exhaust passage for waste gases from said treatment chamber, said open end having an area greater than the area of said flue, said exhaust passage being reduced in cross-sectional area toward said flue as required for said connection with said nue, said reduction vin cross-sectional area being a distance laway from said open end such that the velocity of the waste gases passing through said exhaust passage is increased Within said exhaust passage, and a chamber opening directly into said treatment Ichamber above the top of said exhaust passage to supply at least partially combusted heating gases transversely into said treatment chamber above the normal level of the tops of the ingots and other work pieces to be heated in said furnace.

3. A method for heat treating Work pieces in a furnace having a flue, comprising, in combination, placing Work pieces to be heated `on a hearth in the lower part of a treatment zone, feeding Icombustible heating gases transversely into the upper part of said treatment zone through an area on a side thereof, substantially completing the combustion of said heating gases so fed within the upper part of said treatment zone above said work pieces, withdrawing waste gases from said treatment zone over an area substantially extending across the full width of a side of said treatment zone and generally upwardly Ifrom said hearth to the level of the bottom of the area over which said heating gases are fed into said treatment zone, and reducing the cross-sectional area of the iiow of said waste gases so withdrawn after they are outside of said treatment zone, whereby relatively uniform generally slow descent an-d movement of fully combusted heating gases past said work pieces are obtained without localized velocity effects 'in said treatment zone due to the suction influence of said flue.

4. A method for heat treating work pieces in a furnace having a flue, comprising, in combination, placing work pieces to be heated on a hearth in the lower part of a treatment zone, feeding combustible heating gases transversely into the upper part of said treatment zone substantially across the Width of a side thereof, beginning the combustion of sai-d heating gases so fed outside of said treatment zone, substantially completing the combustion of said heating gases within the upper part oi said treatment zone above said work pieces, withdrawing waste gases from said treatment zone substantially across the width of said side over an area extending substantially upwardly from said hearth to the normal level of the tops of said work pieces and across the full width Iof said side of said treatment zone, and reducing the cross-sectional area of the flow of said waste gases so withdrawn in 'a gradual manner when said waste gases are outside said treatment zone, whereby relatively uniform generally slow descent and movement of fully combusted heating gases past said work pieces are obtained without localized Velocity effects in said treatment zone due to the suction inuence of said ue.

JOHN FREDERICK ROBERT JONES.

6 References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,363,188 Muckle Dec. 21, 1920 1,732,138 Naismith et al Oct. 15, 1929 1,777,125 McDermott Sept. 30, 1930 1,824,876 Culbertson Sept. 29, 1931 2,085,811 Loftus July 6, 1937 2,504,320 Gamble ----1 Apr. 18, 1950 OTHER REFERENCES Pages 354 and 355 of Trinks Industrial Furnaces, vol. I, 3rd ed., 1934. This text is'rpublished by John Wiley and Sons, New York, N. Y.