US2817507A - Forge furnace - Google Patents

Description

2 Sheets-Sheet l c. o. KNIERIM FORGE FURNAGE Dec. 24, 1957 Filed Dec. 2, 195s CARL o. msnm ATTORNEYS Dec; 24, .1957

Filed Dec. 2, 1953 c. o. KNIERIM 2,817,507

FORGE FURNACE 2 Sheets-Sheet 2 INVENTOR. KNIERIM nited States Patent FORGE FURNACE Carl 0. Knierim, Cleveland Heights, Ohio, assignor to The Gas Machinery Company, Cleveland, Ohio, a corporation of Ohio Application December 2, 1953, Serial No. 395,808

s claims. (ci. 263-37) The present invention relates to furnaces for heating metal billets to forging temperatures, i. e., temperatures above about 2000 F. and more particularly to a furnace which provides substantially uniform heating of the billet and more efficient use of the heat supplied to the furnace.

In heating metal billets to forging temperatures, particularly where the billets are directly exposed to the combustion gases which heat the furnace, the surfaces of the billets become scaled due to oxidation. The scale represents a metal loss of from 3% to 5% of the billet and, if not removed before the forging operation, seriously reduces the life of the forging dies.

To reduce the disadvantages due to scaling, attempts have been made to heat the billets in an inert atmosphere, i. e., in direct contact with a non-oxidizing or reducing atmosphere, the billets being heated indirectly by the combustion gases.

The present invention provides an improved furnace for heating billets in an inert or non-oxidizing atmosphere.

According to this invention, the enclosed passage for the billets has an internal cross-section which conforms, in general, to the cross-section of the billet and is only slightly larger than the billet. By making the passageways only slightly larger than the billet and of the same general cross-sectional shape, a compactness is obtained which provides several advantages over the furnaces of the prior art. The number of passageways in a particular furnace may be increased to the maximum, thus increasing the output of the furnace. The volume of inert gas required in the passageways is reduced to a minimum, and the distance from the inner walls of the passageway to the billet being heated is short and substantially uniform, thus providing substantially uniform heating of the billet on all sides.

The fact that a film of carbon from the inert gas is de-v posited on the surface of the billet also protects the same from oxidation in transit from furnace to the press.

All of these advantages contribute to a far more ei cient operation than was possible heretofore, not only by increasing the overalloutput of the furnace, but also by more eflicient utilization of the heat and more uniform heating of the billets and by eliminating scaling. In addition, the required amount of non-oxidizing atmosphere is reduced to a minimum.

The present invention will be described with reference to the accompanying drawings, in which:

Figure l is a longitudinal vertical cross-section of a furnace according to the present invention taken along line 1-1 of Figure 2;

Figure 2 is a transverse vertical cross-section of the furnace shown in Figure 1, taken along line 2-2 thereof; and

Figures 3, 4 and S illustrate in vertical cross-section modifications of the passageways shown in Figure 2.

Referring to Figures 1 and 2, the furnace comprises a conventional steel framework which supports refractory walls 11, a refractory floor 12 and a refractory roof 13.

A plurality of burners 14, for supplying hot combustion gases, are provided in the walls 11. Flues 15 for venting the combustion gases from the furnace may be provided in one of the side Walls 11.

Along the length of the furnace are provided refractory supports 16 on which are mounted the enclosed passageways indicated generally at 17. Although six passageways have been shown, it will be understood that any number of such passageways may be provided depending upon the relative sizes thereof and of the furnace and the expected output of the furnace.

At the end of the furnace where the billets are discharged, there are provided downwardly sloping passages 18 associated with each enclosed passageway 17, through which the billets slide after having been heated to the desired temperature. The discharged billets drop onto a conveyor 19 to be transported to a forging press or other metal treating operation. At the lower ends of passages 18 are provided doors 20 which are normally closed but are automatically opened by the billets to permit them to be discharged as will be described more fully hereafter.

At the other and charging end of the furnace, and associated with each enclosed passageway 17, a plurality of hoppers or magazines 21 (only one being shown) are provided for containing a supply of billets to be heated. At the base of each of the hoppers 21 a pushing device or plunger 22 is provided for intermittently pushing the bottom billets from the magazine 21 into the associated passageway 17 for the heating operation. The billets progress intermittently through the passageway 17 as additional billets are introduced thereinto by the pushing device 22 until they reach the sloping passage 18 when they will slide down said passage and through the door 20 onto the conveyor 19.

The passageways 17 may take any of the illustrative forms shown in the cross-section in Figures 2, 3, 4 and 5 and may comprise refractory bases 23 Which rest on the supports 16 in spaced parallel arrangement. As will be seen in the various figures, the bases 23 may have different shapes for accommodating different types of covers or hoods 24 and different types of billets.

In Figure 2, each base 23 has a longitudinal raised center section 25, of somewhat greater width than the prismatic billet shown in Figures 1 and 2, and longitudinal shoulders 26 on which are disposed hoods 24. The crosssectional shape of the hoods 24 in Figure 2 'correspond in general to the cross-sectional shape of the billets 27, so that the billets are subjected to substantiaily uniform ra diant heat.

In Figure 3 the cover or hood 24 consists of a tube which is supported on the base 23 as shown. In the present case, the term hood or cover is intended to include a tube as shown in Figure 3 as Well as the covers shown in Figures 2, 4 and 5. As shown in Figure 3, the billet 21 has a cylindrical shape and is subjected to substantially uniform radiant heat as mentioned above.

Figure 4 illustrates another form of passageway which can be used with cylindrical billets. The hood 24 is similar to that shown in Figure 2, except that it has a curved top which conforms in general to the cross-section of the billet. The raised portion of the base 23 is provided with a curved surface to conform generally to the shape of the billet.

In Figure 5, the base member 23 is provided with a pair of steel tubes 28 which extend longitudinally along the base and are spaced apart to provide a pair of skids for either prismatic billets or cylindrical billets, both shapes being shown in phantom outline. The tubes 28 are water-cooled so as to prevent any damage thereto by the high temperatures used in forge furnaces. Since the tubes essentially provide only line contact with the billets, it will be seen that the cooling effect of these tubes on the billet will be negligible. The hood 24, in this modification, is curved, as shown in Figure 5, and While the prismatic billets are subjected to radiant heat which is not quite so uniform as when cylindrical billets arc heated, they are, nevertheless, very uniformly heated. This moditication has the advantage of being suitable for use with either type of billet, while the passageways shown in Figures 2, 3 and 4 are generally only suitable for use with one type of billet, as shown.

It will, of course, be understood that any furnace may be provided with a plurality of the same type or different types of passageways, depending on requirements.

Referring now to Figure 1, an inlet 29 is provided near the. discharge end of sloping passageway 18 for the introduction of non-oxidizing or reducing gas. The gas moves through the passageway, counter-current to the movement of the billets and is vented through exit pipe 30, which communicates with the inlet end of the passagewayy 17. A conventional spring-mounted closure 31 is provided at the end of the passageway to permit expansion thereof when being heated up.

lf desired, the gas may ow concurrently through the passageway 17 instead of counter-currently. In such a case, of course, an inlet similar to inlet 29 would be provided in the passageway 17 adjacent exit pipe 30, and an exit pipe similar to pipe 30 would communicate with passage .1S adjacent the door 20.

Passageway 17 has a co-linear extension 32, which terminates at the door 33 to facilitate cleaning of the passageway when necessary.

The inert gas in the passageways 17 is maintained at a pressure slightly above that of the combustion gases so as to prevent any leakage of the latter into the passageways.

Even though the sections of the hoods 24 and bases 23 usually only abut one another, the abutting surfaces have such smoothness that a very ecient gas seal is obtained. Furthermore, the spring closure 31 tends to keep the sections of the hoods and bases under compression.

Various types of atmosphere may be used within the passageways, but it has been found that hydrocarbons may be used satisfactorily, such as raw propane. Other non-oxidizing gases are Well-known in the art.

Although the present invention has been described with particular reference to the apparatus shown in the drawings, it will be understood that various modifications of the present furnace will occur to those skilled in the art, and it is intended that such modifications as come within the scope of the appended claims be covered thereby.

What I claim is:

1. A furnace for heating elongated billets to forging emperatures while pushing them one after another in endto-end relationship through a heating zone of the furnace, said furnace comprising refractory side wall, end wall, roof, and floor portions dening a combustion chamber, at least one generally tubular assembly of small exterior cross-section relative to that of said combustion chamber and longitudinally uniform interior cross-section, said assembly extending substantially horizontally and longitudinally through the furnace between the end wall portions thereof intermediate and spaced from said roof and floor portions, said assembly, within said combustion chamber, enclosing an elongated passageway constituting said heating zone to exclude therefrom gases present in said combustion chamber, exterior openings axially into the ends of said assembly, means operative for intermittently introducing billets through one of said openings into said assembly for movement axially therethrough and through said heating zone, means normally closing the opposite end of said assembly and operable to permit withdrawal of heated billets intermittently as they arrive adjacent said opposite end, and means for introducing and burning a combustible fuel in said combustion chamber about said assembly, each such assembly comprising a plurality of separable, elongated, refractory base members disposed in end-toend co-linear engagement from one end of the assembly to the other, a substantially co-extensive plurality of similarly disposed, separable, elongated, refractory cover sections4 resting on said base sections and defining said uniform interior cross-section of said tubular assembly above said base members, whereby the interior cross-section of said tubular assembly may be adapted to closely surround and generally conform to any given crosssection of a series of billets to be pushed therethrough merely by selecting cover sections of appropriate crosssectional size and configuration, each such tubular assembly being abutted endwise against an adjacent end wall portion of the furnace and the opposite end of the assembly projecting into an opening in an opposite end wall portion of the furnace, and said furnace additionally comprising means for applying a yielding force against said opposite end of each such assembly to hold the separable sections thereof in end-wise compression between one another and the end Wall portion abutted by one end of the assembly, whereby gas pervious gaps between the separable sections are minimized, and means for introducing a desired non-oxidizing gas under pressure into one end of said assembly and exhausting it from the opposite end thereof to maintain a pressure of said gas in the assembly above the gas pressure in said combustion chamber about the assembly for preventing leakage of combustion products from the combustion chamber into said heating zone.

2. A furnace according to claim 1 in which said base members are provided with longitudinally extending raised center sections for directly supporting billets and longitudinally extending shoulders on opposite sides of said center sections for supporting said cover sections.

3. A furnace according to claim 1 including a pair of spaced, parallel, skids supported on said base members and extending longitudinally thereof to support billets moving through the furnace.

4. A furnace accordingto claim 1 in which said cover sections are substantially semi-circular in transverse crosssection.

5. A furnace according to claim l in which said cover sections are substantially U-shaped in transverse crosssection.

References Cited in the file of this patent UNITED STATES PATENTS 1,508,135 Blount et al. Sept. 9, 1924 1,692,614 Bissell Nov. 20, 1928 1,710,870 Forse Apr. 30, 1929 1,756,584 Cope Apr. 29, 1930 2,022,649 C orriston Dec. 3, 1935 2,103,234 Clauss et al Dec. 28, 1937 2,472,497 Stookey June 7, 1949 2,485,782 Schweitzer Oct. 25, 1949

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