US2953363A

US2953363A - Skid rail apparatus for furnaces

Info

Publication number: US2953363A
Application number: US552770A
Authority: US
Inventors: John D Nesbitt
Original assignee: Midland Ross Corp
Current assignee: Midland Ross Corp
Priority date: 1955-12-13
Filing date: 1955-12-13
Publication date: 1960-09-20
Anticipated expiration: 1977-09-20

Description

9 3 3 7 V SKID RAIL APPARATUS FOR FURNACES John D. Nesbitt, Toledo, 0hio, assignor, by'n'iesne signments, to Midland-Ross Ohio, a corporation of Ohio Filed Dec. 1a, 1955, Set- No. ss zmo I '5 Claims. c1. 263 -6) Corporation, Cleveland,

This invention pertains to a rail structure which pro-v vides an even, insulated surface along which work is conveyed and has particular adaptability to heat treating furnaces.

A typical use of the invention is in connection with a furnace having a high thermal head and utilizing water cooled skid rails for supporting the work passing through the heat treating chamber. The advantage of this type of furnace is in bringing the temperature of the work rapidly to that desired to minimize the time the work is in the furnace and subject to scaling. A common use is in the heat treatment of billets to bring them to the proper temperature for forging. The scale formed on the heat treated billets may be a few thousandths of an inch compared to over one-twentieth of an inch for billets heat treated by conventional means. To heat treat with minimum scale, a thermal head of perhaps 400 F. to 500 F. is necessary which may involve temperatures of 2700 F. in the furnace chamber in order to rapidly heatthe billets to a forging temperature of 2200 F. The billets are thus brought up to temperature in a minimum of time and scale is likewise kept to a minimum.

The skid rails on which the billetsrest tend to produce uneven temperatures therein since the portion of the billets adjacent the water cooled rails will be cooler than other portions. To overcome this disadvantage, it is known'to transfer the billets from the water cooled rails to refractory supports in the latter portion of the furnace. The refractory supports are substantially uniformly. at the same temperature as that of the furnace chamber and thus allow the billets to attain a more even temperature beforev being discharged. The water cooled rails, at the point of transfer of the billets to the refractory supports, are generally bent downwardly and pass out of the bottom wall or portion of the furnace chamber. However, this tends to interfere with combustion, particularly when a cylin drical heating chamber is employed in which the flame tends to hug the inner wall surface thereof. Furthermore, these rails frequently need replacement which results in down time during the period of replacement. For the type of rail just discussed,.thejrequired replacement time is long, often being as much as four-days.

. which further acts as an insulator.

This invention allows the use of bare water cooled rails in the furnace chamber zones of fast heating and of insulated supports in the soaking zones substantially with out the aforementioned difficulties.

For further consideration of what is novel and my invention, refer to the accompanying drawing and following specification.

In the drawing:

Figure 1 is a longitudinal, sectional view on line 1-1 of Figure 2 of a furnace embodying the invention,

Figure 2 is a transverse, sectional view on line 22 of Figure 1,

Figure 3 is a detailed view of 1 and 2,

Figure 4 is a cross-sectional view on line 4-4 of Figure 3, and

, tion from this surface.

2,953,363 Patented Sept. 20, 1960 pipes 21 carry the mixture from manifolds 20 to burners 22 and then through ports 23 tangentially into chamber 14. This mixture is ignited and spun in the chamber, tending to hug the inner surface 24 of refractory wall 13 which is effectively heated thereby, the work passing through the chamber principally being heated by radia- The combusted mixture then travels helically toward flues 25 and 26 where it is expelled. The work W, which may be billets that are to be forged upon emerging from the furnace, is supported on Water cooled rails or pipes 27 which, in turn, are upheld by refractory members 29. Toward the discharge endof the furnace a soaking zone is maintained with alloy sleeves 28 placed about these portions of pipes 27. To

provide an even, continuous. surface, the pipes are offset sufficiently to assure that the surfaces of the alloy sleeves 28 are even with the bare port-ion of pipes 27, the amount of offset equaling the thickness of the tube or sleeve employed. This offset is made in a plane perpendicular to the surfaces of the work that the rails contact. If the surfaces are horizontal, the oifset will be made in a vertical plane or if the work is shaped and placed as shown in Figure 2, the oifset will be made in a plane at an angle of approximately forty-five degrees to the horizonal. A pusher mechanism 30 is employed to push the billets end to end through the furnace from which they slide into receptacle 31.

In practice, the inner diameter of sleeve 28 may be somewhat larger than the outer diameter of the pipe. This allows an air space to be formed between the two In cases where there is substantially no difference between the two diameters, the sleeve will nevertheless expand more than the pipe since it is hotter, and an air space will thus be created anyway. v I

As previously stated, the billets, travelling on the water cooled rails, develop cold spots in the portions adjacent the rails. This uneven temperature distribution tends to cause eccentricity in the final, forged product, which may result in the work being scrapped. To allow the temperature within the billet to become more uniform, the alloy sleeves 28 are placed about the water cooled rail 27. In a furnace chamber of 2700 F., these sleeves have a temperature of more than 1600" F. compared with a temperature of bare rails 27 of 150400? F, This temperature increase isgenerally sufiicient to pre& vent excessive eccentricity in the final product. In short furnaces for heating billets, alloy sleeves 28 may be placed over the entire length of rails 27. However, such use increases friction between the billets and the support and thus requires a heavier pushing mechanism 30 or results in the buckling of the billets at the charge end of the furnace. For these reasons, the alloy shields are generally employed only in the soaking or discharge zone which is a latter zone of the furnace whose chief function is to create temperature uniformity in the treated work. Although termed such, this zone is not actually a soaking zone in high thermal head furnaces since the temperature therein is maintained approximately equal to that in the heating zone; thus, in this zone, the heat not only is distributed in the billet, but additional heat is absorbed by it.

quently affords greater temperature uniformity. Rails employing a wear strip may also be used with this type of furnace, if desired.

In the construction of these covered rails, sleeve 28, with or Without sleeve 32, is anchored at offset portion 33 of the pipe by means of weld 34 which also fills in the space between the end of sleeve 28 and offset 33. This method of attaching the sleeve allows free expansion toward the discharge end, thus eliminating buckling or bowing. The weld at this portion of the sleeve also tends to prevent it being damaged by a billet catching and tearing it loose. The sleeves may be made of a continuous tube which is then passed over one end of the pipe, or may be made in two halves which are then welded together. The offset will equal the thickness of the tube or sleeve employed.

The bare, water cooled rails and the soaking zone hearth are one unit with this method of construction and the rails may thus be extended straight through the charge and discharge openings without having to be bent and passed through a furnace wall as previously necessary. Also, this integral unit can be replaced in a few hours as compared to several days for the previous method.

In furnaces employing a high thermal head, it is essential that an alloy sleeve be utilized since the use of a refractory sleeve at temperatures above 2400-2500 F. is unsatisfactory. Slag from the billets tends to stick to the sleeves as the billets pass over them and the temperature of this slag eventually becomes approximately equal to that of the furnace chamber. When that temperature is in excess of 2400-2500 F. as in this case when 2700" F. temperatures are frequently used, the slag tends to destroy the refractory and seriously shortens its life.

The foregoing discloses the best mode known to the inventor of carrying out the invention, the scope of which is limited only by the appended claims.

I claim:

1. In a high thermal head billet heating furnace having heating and soak zones, means for supporting work passed through the furnace comprising: metallic internally cooled rail means extending through the furnace, said rail means being bare in the heating zone; a first alloy sleeve of substantially uniform thickness disposed about the portion of the rail means within the soak zone; and a second alloy sleeve of substantially uniform thickness surrounding the first sleeve, said portion of the rail means within the soak zone being offset equal to the wall thicknesses of the two alloy sleeves whereby the work contacting segment of the second sleeve forms an even continuous surface with a corresponding adjacent work contacting surface of the rail means.

2. Apparatus according to claim 1 characterized by the alloy sleeves being affixed to the rail means adjacent the start of the offset portion by means of a weld, the weld metal being sufiicient to fill the gap between the work contacting segment of the second alloy sleeve and the corresponding adjacent work contacting surface of the rail means.

3. In a high thermal head billet heating furnace having heating and soak zones, means for supporting work passed through, the furnace comprising: metallic internally cooled rail means extending through the furnace, said rail means being bare inthe heating zone; a plurality of alloy sleeves of successively larger inside diameters, the larger diameter sleeves encircling the smaller diameter sleeves, and all being circumposed about the portion of the rail means within the soak zone, said portion of the rail means within the soak zone being offset equal to the combined wall thicknesses of the alloy sleeves and the rail means and sleeves being in line contact with each other whereby the work contacting segment of the outermost sleeve forms an even continuous surface with the corresponding adjacent work contacting surface of the rail means.

4. Apparatus according to claim 3 characterized by the alloy sleeves being affixed to the rail means adjacent the start of the offset portion by means of a weld, the weld being sufficient to fill the gap between the work contacting segment of the outermost alloy sleeve and the corresponding adjacent work contacting surface of the rail means.

5 In a high thermal head billet heating furnace having heating and soak zones, means for supporting work passed through the furnace comprising: metallic internally cooled pipe means extending through the furnace, said pipe means being bare in the heating zone; and an alloy tube of substantially uniform thickness having an internal diameter larger than the external diameter of said pipe and being disposed about the portion of the pipe means within the soak zone, said portion of the pipe means within the soak zone being offset equal to the thickness of said tube and the internal diameter of the tube being in line contact with the external diameter of said pipe means, and said alloy tube being affixed to the pipe means at a single point by means of a weld which is adjacent to the start of the offset portion, the weld metal being sufficient to fill the gap between the work contacting segment of the alloy tube and the corresponding adjacent work contacting surface of the pipe means to form an even continuous surface therewith.

References Cited in the file of this patent UNITED STATES PATENTS nu. s uts