Method And Machine For The Rapid Heating Of Tubes

Abstract

A method and machine for rapidly heating an open-ended tube in a furnace provides for placing the tube on a support inside a tunnel furnace and projecting the flame of a burner through one of the tube ends into the interior of the tube. The burner thus will act as an injector drawing the exhaust gases, that exit at the other tube end, around to return outside the tube and to reenter the tube at the one end.

Description

The invention relates to methods and machinery for the rapid heating of tubes or the like, such as drums, in a furnace. More particularly, the invention relates such method and machinery of the type that is used for quickly heating tube blooms which subsequently will be rolled in rolling mills.

Such tube blooms are rolled in tube-rolling mills, for instance in reduction rolling mills; before the rolling, however, the blooms will need to be heated to the necessary rolling temperature; and that rolling temperature varies with the composition of the material of the tube. Such heating is carried out rapidly in continuous heating furnaces. In the past, either gas burners have been provided in such continuous heating furnaces and the combustion gases of these burners been applied to the exterior of the tube, or the tube has been heated on the exterior electrically. During such heating, the tubes are moved longitudinally. Alternatively, there have been used in the past for this purpose roller-type heating furnaces which are traversed by the tubes. Where tubes of large diameter and particularly of great wall thickness are involved, the aforedescribed methods of the prior art can be carried out only with very large furnaces, in order to provide for a satisfactory uniform heating; these large furnaces are, of course, prohibitively costly. While the rolling in rolling mills of tubes with large diameter and thick walls has been solved satisfactorily, the economic heating of these tube blooms to the necessary rolling temperature has not been achieved heretofore.

The invention accordingly has among its principal objects to provide means and machinery for economically carrying out quick heating of tubes and tubelike structures such as forged or welded drums.

It is another object of the invention to provide such method and machinery for the quick heating of tubes of even large wall thickness and large diameters satisfactorily and economically.

Further objects and advantages of the invention will be set forth in part in the following specification and in part will be obvious therefrom without being specifically referred to, the same being realized and attained as pointed out in the claims hereof.

Broadly speaking, the instant invention provides for introducing the burner flame into one of the open ends of the tube to heat the tube from the inside thereby acting as an injector causing the exhaust gases that exit from the other end to turn around and to reenter the tube interior at the aforesaid one end through which the burner projects.

It has been found advantageous to move the tube during at least a part of the heating operation in opposite directions axially of the longitudinal axis of the tube, and, in accordance with a preferred embodiment to rotate the tube during at least a part of the heating operation in order to avoid the necessity for moving the burner during the operation.

During the heating operation, an amount of suitably cooled heating gases will be withdrawn through a chimney continuously, in accordance with the amount of combustion gases being produced during the respective time period.

In accordance with a preferred embodiment, the combustion gasses are introduced into the aforesaid longitudinal central axis of the tube, so that the tube itself will act as an injector nozzle and will cause the heating gas to turn around for subsequent reentry at the burner end, without need for any additional outside energy means for guiding the gasses.

In accordance with the instant invention, however, such guide means may be provided for aiding the turnaround of the exiting gases and for aiding their reentry.

It is possible to carry out the instant method with but a single burner, depending on the dimensions of the tube to be heated.

ADVANTAGES

It is among the advantages of the instant invention to utilize especially well the heat content of the exhaust gases, thereby heating the tube simultaneously on the inside and on the outside, and utilizing the heat convection of the gases during their rapid flow.

It is another of the invention to reduce the danger of the formation of cracks in the tube wall due to heating, which danger existed to a large extent during the prior art heating operation as it was confined to heating the tube only from the exterior. This danger to a large extent is avoided by the instant invention, in that the surface which obtains most of the heat is the internal surface which is under compressive stress.

Further advantages may be found in the low thermal stress that the furnace brickwork is being subjected to, owing to the shielding of the flame radiation, and the absorption thereof, by the tube wall, as the burner is applied to the inside surface of the tube; and there exists the possibility to position the burner in such a manner that the external surface of the tube is not impinged upon by the flame.

BRIEF DESCRIPTION OF THE DRAWING

The single view is a vertical sectional view of a furnace containing a tube, in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the drawing, the tube 1 is shown inside a tunnel furnace 2. The tube 1 is supported on a preferably movable support, such as a truck 3 that can be moved in axially opposite directions, as indicated by the straight arrows in the drawing. Furthermore, the tube can be rotated about its longitudinal axis, by means of conventional well-known rotating mechanisms.

One end side of the furnace 2 is formed as a movable door 4, through which the furnace 2 is charged. The opposite end side defines a chimney 5 through which the burner 6 projects into the chamber of the furnace 2. The combustion gasses are blown into the aforesaid longitudinal central axis of the tube 1. As shown in the drawing, the discharge nozzle of the burner 6 is positioned inside the tube 1 near its end side. In this manner, the burner acts as an injector and sucks in the exhaust gasses that exit at the far end (the right-hand side end of the drawing) of the tube 1 in order to provide for the reentry thereof at the end through which the burner 6 projects (the left-hand side end of the drawing), as shown by the U-shaped arrows in the drawing.

The turning about and subsequent reentry of the exhaust gasses may be aided by means of guide means, such as shaped elements 7. This heating on the interior combined with the guiding of the exhaust gasses will provide for a rapid and uniform heating of the wall of the tube 1. Continuously there will be withdrawn through the chimney 5 an amount of exhaust gases that corresponds to the amount of combustion gasses produced by the burner 6 and introduced by the burner into the interior of the tube 1.

Particularly useful for the instant method and machinery are high-speed burners, particularly oxygen fuel jet beam torches, as their closely concentrated beam that exits from the torch nozzle at a high impulse is particularly suitable for generating the desired aforesaid injector effect. These type burners or torches provide for the combustion of combustible gas and oxygen in almost any desired ratio, for instance almost stoichiometrically, and in ideal flame guidance. Therefore, they enable the control of scaling at the external surface of the tube, which can be kept very low or be eliminated altogether.

Various modifications from the foregoing principles are possible. For instance, several tubes 1 may be positioned parallel to each other and be heated simultaneously. Instead of placing them horizontally as shown in the drawing, they may be placed in other positions, for instance vertically.

I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

Claims

Having thus described the invention, what I claim as new and desire to be secured by Letters Patent, is as follows:

1. In a method of rapidly heating an open-ended tube, in a furnace and with the aid of at least one burner, the steps comprising, holding the burner flame in the tube interior adjacent one end of the tube, for heating the tube from inside, the exhaust gasses exiting at the other tube end, said burner acting as an injector sucking said exiting exhaust gasses to turn around and to reenter the tube through said one open end, and the step of returning said exhaust gasses prior to their reentry along the exterior of the tube.

2. In a method of rapidly heating an open-ended tube, in a furnace and with the aid of at least one burner, the steps comprising, holding the burner flame in the tube from inside, the exhaust gasses exiting at the other tube end, said burner acting as an injector sucking said exiting exhaust gasses to turn around and to reenter the tube through said one open end, and the steps of rotating said tube during at least a part of the heating operation, and oscillating it longitudinally.

3. A machine for rapidly heating an open-ended tube, comprising in combination a tunnel-shaped furnace including two end walls, one end wall being movable for the passage of said tube, and including a chimney near the other end wall, support means inside said furnace operable for supporting said tube, a burner including combustion gas discharge means inside said furnace positionable to project with its flame-discharging portion into the interior of said tube within said furnace through one of the open tube ends, and guide means for directing the exhaust gasses exiting from the other tube end to flow alongside the exterior of the tube for subsequent reentry of the exhaust gasses into the tube interior through said one end.

4. A machine for rapidly heating an open-ended tube, comprising in combination, a tunnel-shaped furnace including two end walls, one end wall being movable for the passage of said tube, and including a chimney near the other end wall, support means inside said furnace operable for supporting said tube, a burner including combustion gas discharge means inside said furnace positionable to project with its flame-discharging portion into the interior of said tube within said furnace through one of the open tube ends, and said support means including means operable for moving said tube along its longitudinal axis inside said furnace during at least a part of the heating operation.