US2998966A

US2998966A - Heat-treating apparatus

Info

Publication number: US2998966A
Application number: US632225A
Authority: US
Inventors: Philip L Knight
Original assignee: Midland Ross Corp
Current assignee: Midland Ross Corp
Priority date: 1957-01-02
Filing date: 1957-01-02
Publication date: 1961-09-05
Anticipated expiration: 1978-09-05

Description

Sept. 5, 1961 P. L, KNIGHT HEAT-HEATING APPARATUS 2 Sheets-Sheet 1 Filed Jan. 2, 1957 INVENTOR PHlLIP L. KN\6HT BYZd/z/ Sept. 5, 1961 P. L. KNIGHT HEAT-HEATING APPARATUS 2 Sheets-Sheet 2 Filed Jan. 2, 1957 Fmi- FIA-

INVENTOR. PH\L|P L. KN\6HT United States Patent O 2,998,966 HEAT-TREAIING APPARATUS Philip L. Knight, Toledo, Ohio, assignor, by mesne assignments, to Midland-Ross Corporation, Cleveland, Ohio, a corporation of Ohio Filed Jan. 2, 1951, ser. No. 632,225 4 Claims. (Cl. 263-3) This invention pertains to high thermal yhead furnaces and more particularly to a method of, and apparatus for, controlling temperature and protecting the work therein when the rates of advance of said work is slowed or stopped or its emissivity is changed.

High thermal head furnaces are becoming increasingly popular in the heat-treating industry. Higher production rates, particularly for a given amount or" floor space and capital investment required, are continually being sought. High thermal head furnaces produce higher heating rates than ordinary furnaces and thereby are capable of heating greater quantities of metal per unit area of floor space. They are thus especially suited to high production rate requirements.

These furnaces, in heating the work quickly, also subject the Work to elevated temperatures for a shorter period of time which reduces the amount of scale formed or the amount of discoloration of the work. In some cases, where-inert gas may be required for the heat- Brass and other non-ferrous strip may be heated in a similar manner but at flower temperatures.

Another type of high thermal head furnace, or high speed furnace as it is frequently called, has a cylindrical refractory wall with burners arranged to tire tangentially thereagainst. Such @a furnace generally has skid rails near the center on which the Work is supported as it is pushed therethrough. Where it is desired to heat steel billets to forging temperatures of 20002200 F., the walls of the furnace are heated to 2500-2600 F. This maintenance of a G-600 F. thermal head above the desired Work temperature enables a heating rate up to three minutes per inch so that a furnace 16 feet long with a 40 inner diameter is capable of heating 10,000 pounds per hour of 6" square billets.

In all high thermal head furnaces, however, there is an omnipresent problem. When production is slowed or stopped, the work in the furnace must be prevented from being overheated. Overheating may cause the billets to melt or the strip to pick up dirt from the rolls or to be marked thereby. Either situation involves considerabie loss of material and, in the former case, production time during the repair period in which the lmolten metal is removed from the furnace.

In strip furnaces, since the strip cannot be stopped Without damage, looping towers of consider-able height must be provided at both the charge and discharge ends of the furnace. These are necessary to permit continuous travel of the strip through the furnace when another coil of strip is to be stitched to the preceding one at the charge end, and when the strip is cut to wind a new ycoil at the discharge end. The present invention, as will be seen later, eliminates the need Ifor these looping towers which require large capital expenditures and considerable space.

Patented Sept. 5, 19.61

For any high thermal head furnace, where the work must be stopped, the usual methods to prevent overheating have been to empty the furnace or inactivate the heating source, although with strip furnaces, the raforementioned looping towers may be used to counteract temporary shut downs. Emptying the furnace results in extra time to unload and reload and is not feasible with strip furnaces where the entire strip would require removing and re-threading. When the heating source is shut off, the work continues heating as the furnace cools until equilibrium between the temperature of the work and the temperature of thefurnace walls is reached. This results in overheating of the Work which is close to final temperature. Also, the work will cool'only as fast yas the furnace does so that it remains at elevated temperatures for extended periods of time. This is suicient to cause considerable scaling or discoloration. A third method often used for temporary stoppages consists of throttling the burners to create in the furnace a temperature equal to the final temperature desired for the work yand allowing the work to soak at this temperature. An excessive amount of scale or discoloration occurs in this case, even for sho-rt periods of time. Also, the work tends to become overheated when production is resumed. Where prernix burners are employed, reduction of the firing rates may cause backfiring. Y

To overcome these problems without the usual disadvantages, apparatus has been developed for accurately controlling heat-treating temperatures of the workv and for protection of the work in case of stoppage.

Y For further consideration of what is novel and th invention, refer to the following portion of the specification, the drawing, and the appended claims.

In the drawing:

FIGURE l is a partial cross-sectional View on line 1-1 or" FIGURE 2 of a strip furnace embodying the invention with controls therefor,

FIGURE 2 is a cross-sectional transverse view on line 2 2 of FIGURE 1, I

FIGURE 3 is a cross-sectional view on line 3-3 of FIGURE 4 of a billet heater embodying the invention,

FIGURE 4 is 'a cross-sectional View on line -4-4 vof FIGURE 3,

FIGURE 5 is a View on line 5--5 of FIGURE 3.

According to FIGURE l, a strip furnace 21 comprises heating chamber 22 defined by refractory wall 23 and heated by a plurality of radiant tubes 24 placed transversally therein. The strip 25 to be heat-treated travels longitudinally through the chamber and through projections or sleeves 26 which project through the end walls of the furnace. The sleeve at the charge end is in its outer position and the sleeve yat the discharge end is shown in its inner position. Each sleeve consists'ofa 'watercooled space 27 surrounded by insulation 28 Vand metal casing 30. Insulation 32 forms an inner opening in each sleeve 26 land a plate 31 forms -an outer opening in each sleeve. Also, each sleeve is provided with one or more work supporting rollers 33. Each water-cooled wall has two

adjacent openings

34 and 35 which serve as an inlet and -an outlet for flexible water conduits. Space 27 has a iirst partition 36 extending longitudinally throughout its llength and a second partition 37 extending from the outer end of wall 27 partially toward the inner end thereof. With these partitions, the water must pass around space 27 and toward the inner end of it in flowing from the inlet to the outlet.

Where the speed of strip 25 is varied according to production requirements or the like, a thermocouple .or other temperature measuring means 38 may be provided at the discharge end of furnace 21 adjacent strip 25 to measure the ytemperature of the heated strip. The thermo- ,to retract from the chamber. t through either of

lines

43 or 50, current is also supplied 1a cylindrical, tangentially tired, billet heater.

.couple is connected to a commercially `available control instrument 40 which may be used to control the position of either of the sleeves, or both if desired. Controls for only one sleeve are shown to Ysimplify the drawing. VEither sleeve may be operated` by a ,hydraulic piston 41 4which is controlled by control box 40 to move thesleeve inward or outward according to the temperature of the strip Rather than the pistons as `a moving meansfor the sleeves, other means, such as a motor and gear arsrangement, as a rack and pinion, may be employed'depending on the characteristics of the installation. The .sleeves are slidable `by means of rollers 54 and slides 55 which coact with troughs 56. These are also placed Aon :the top and sides of the sleeves to assure proper align- `ment as well as proper support thereof. Roller frames,

trolleys, or other suitable means may be substituted.

The piston 41 for either sleeve is controlled by controller 40 through a hydraulic system and an electrically `operated four-way valve 42. When the temperature of the work is above that desired, current through line 43 will cause valve 42 to pass oil from pump 44 to the blind end of piston 41 through line 4S. Oil from the rod end of piston 41 then passes through line 46 back through valve 42 and return line 47 to reservoir 4S. This causes sleeve 26 to extend into chamber 22. Similarly, with the temperature below that desired, current will be supplied through line 50 which causes valve 42 tobe positioned in a manner to pass oil from pump 44 through line 46 to the rod end of the piston and cause the sleeve When current flows through

line

53 or 59 to a normally open by-pass valve 51 in by-pass line 52. This causes the valve 51 to close .and prevents oil from pump 44 from by-passing valve 42.

When the temperature of the strip is correct, valve 5 1 remains open, thus lay-passing the ,oil and allowing the piston to remain stationary.

.In operation, a rise in strip temperature will betrans- `rnitted to the control instrument which will cause one or both of the sleeves to move inwardly,.thus shielding Aa u portion of the strip from heat ,and thereby maintaining lower temperatures. Or, if the temperature of the strip is too low, the sleeve or sleeves will be moved outwardly ,to expose a greaterportion of the strip in the furnace and Athus raise its temperature. The controls may be set to extend both sleeves to their full length into the furnace to shield the strip completely, if the temperature of the strip should rise a predetermined amount, for instance 100 F. above the desired temperature, as will occur if Athe strip is stopped. Where the sleeves are used only as protective means during slow downs or stoppages,

vmanual operation is satisfactory.

As an alternate to measuring .the temperature, the strip 4may be tested after being passed through the furnace `by a hardness tester or the like. The sleeves will then .be manually positioned to vary the temperature according to results of the test.

The high thermal head furnace of FIGURES 3-5 is This furnace 81 has a thick, cylindrical refractory wall 82 which is heated to elevated temperatures by burners 83. Bil- ,lets 84 are pushed through the center of the cylindrical heating chamber 85 upon skid rails S6 supported by piers 87.

Projections or sleeves S3 are located at both ends .or either end of the furnace, being shown only at the discharge end, and are of sufficient length to totally enclose the work when fully extended into the furnace. This type of furnace is usually employed in forging where .the production rate frequently is varied and temporary shut downs, as Well as longer ones, are common. The sleeves thus have particular importance to prevent overheating in such furnaces. Where the production rate is decreased, one or both sleeves will be partially inserted into charnber 85. When temporary shut downs occur, the sleeves may Abe fully inserted to enclose the billets, leaving the burners at their normal tiring rates. For some installations, a sleeve inserted approximately half way into the chamber from the discharge end is sufficient to prevent damage to the billets for temporary shut downs. In such cases, .billets at the .charge end have :not attained high enough temperature to be subjected to overheating or excessive scalingand may thus be left temporarily unprotected. For longer periodsof shut down, the sleeves are extended completely to protect all billets and the burners are either throttled or turned off completely. rThe sleeves may have an inertgas admitted to them through flexible conduits 90, shown only in FIGURE 3, to prevent scaling of the billets by excluding air.

Projection or Ysleeve S8 is of similar construction to sleeve 26 and has water-cooled space 91, insulation92. and metal casing 93.

Walls

94 and 95 are provided at each end of the sleeve to form openings therein. Each sleeve has a waterinlet 96 and outlet 97 with a partition 98 at the upper portion of the space extending from the back of it toward the front to direct the llow of water around the space and toward the front of it. Since the sleeve may not extend around the bottom portion of the work due to piers. 87, a separate projection 100 is employed therebetween. This projection is cooled by pipe 101 supplying water to the inner end with a drain port 102provided at the outer end.

Sleeve 88 is supported by rail 103 connected to the furnace casing by plate 104 and supported at its other end by legs 105. The sleeve has an L-shaped projection 106 rotatably supporting

rollers

107 and 108. The forward portion of the sleeve is supported by one or more rollers 110. In its outer position, roller 107 `bears againstrail 103 and inA its inner position, roller 103 bears against the rail. The sleeve is powered by means such as piston 111.

A pushermechanism 99 is used at the charge end to push billets end to end through the furnace onto rails 86. The mechanism isdisplaced a. sutcient distance from the charge end to alloy/.room for the sleeve when employed there, with railsSextended accordingly.

The projections of FIGURES 3-5 are Amanually operatedin mostcases since their infrequent use, only during work stoppages, does .not warrant automatic operation, normally. However, they may be automatically operated in the same manner that the projections for the strip furnaces are, ifdesired.

Many other configurations and adaptations of the projections Will be evident. The basic invention as set forth is a retractable, cooled projection that is adaptable-.for insertion in a chamber containing work which is subjected to high thermal heads and may he injured by excessive temperaturesV in the event of slow downs. or stoppages.

.The above has been intended to serve in an illustrative and not a limiting sense, thescope of the invention being `limited only bythe .depending claims.

I claim:

1..In a strip heatingfurnace, a sleeve adapted for encompassing the str ip adjacent that portion passing through a wall of the furnace, said sleeve comprising wall means defining an annular space adapted for surrounding the strip; an inlet and an outlet communicating with said space; meansfor supplying a coolant to said inlet; tracks coacting with said wall means to guide and slideably support it;.means for moving said wall means into and out of said chamber in a direction adapted to be parallel to the path of the strip; rollers within the central portion of said wall means, arranged transversely to the path of said strip, and for supporting said strip; temperature measuring means for measuring the temperature of the str ip leaving the furnace; and control means for actuating the moving means in response to the measuring means.

2. A high thermal head furnace comprising: refractory means defining a chamber; heating means in said chamber for creating a temperature therein substantiallyabove the nal temperature desired for the work; openings in opposite Walls of said chamber; a plurality of rails extending through said openings and said chamber; vertical support means in said chamber for supporting said rails; wall means defining an arcuate shaped space extending from adjacent the support means and adapted to extend around the upper portion of the work; second Wall means defining a second arcuate shaped space extending from adjacent the support means and adapted to extend around a lower portion of the Work; a first inlet and a first outlet for supplying coolant through the first space; a second inlet and a second outlet for supplying coolant through the second space; a track located outside said chamber, above said first and second Wall means, and adapted to be parallel to the direction of travel of the Work; rollers connected to said first Wall means and adapted to contact said track; and means for moving said first and second Wall means into and out of said chamber.

3. A high thermal head furnace comprising: refractory means defining a chamber; heating means in said chamber for creating a temperature therein substantially above the final temperature desired for the work; openings in opposite walls of said chamber; a plurality of rails extending through said openings and said chamber; vertical support means in said chamber for supporting said rails; wall means defining an arcuate shaped space extending from adjacent the support means and adapted to 6 extend around the upper portion of the Work; a first inlet and a irst outlet for supplying coolant through said space; and means for moving said wall means into and out of said chamber through one of said openings.

4. Apparatus according to claim 3 characterized by second wall means dening a second arcuate shaped space, said second Wall means and space being substantially identical to the first Wall means and space, said first and second Wall means being of sufficient length to he adapted to totally enclose the work in the chamber when fully extended thereinto; and means for moving said second Wall means into and out of said chamber through the other of said openings.

References Cited in the file of this patent UNITED STATES PATENTS 967,876 Arthur Aug. 23, 1910 1,694,684 Cope Dec. 1l, 1928 2,629,162 Peck Feb. 24, 1953 2,656,449 Elgar Oct. 20, 1953 2,664,282 Mann Dec. 29, 1953 2,666,994 Dungler Ian. 26, 1954 2,805,054 Hill Sept. 3, 1957 FOREIGN PATENTS 767,338 France Jan. 20, 1934