US1924294A - Apparatus and method of extruding pipe - Google Patents

Description

1933- w. B. SHIRK ET AL APPARATUS AND METHOD OF EXTRUDING PIPE Filed June 12, 1930 INVENTORS VVI'I/iom B. 5hl'rk, PorferH. Brace and Newb/d C.

' ATTORNEY Patented Aug. 29, 1933 APPARATUS AND 1,924,294 METHOD OF EXTRUDING PIPE William B. Shirk and Porter H. Brace, Forest Hills, and Newbold C. Goin, Pittsburgh, Pa., assignors to Westinghouse Electric and Manufacturing Company, a Corporation of Pennsylvania Application June 12, 1930. Serial No. 460,554

4 Claims.

Our invention relates to an apparatus for, and a process of, extrudingmetal pipe and more particularly to an apparatus comprising a suitable die and mandrel composed of an alloy that is capable of maintaining its strength at comparatively high temperatures.

The principal object of our invention is to provide a process of extruding metal pipe which comprises forcing the metal, at a temperature only slightly below its solidification point, between a metal die and a suitable mandrel, both of which are composed of metals having a comparatively high strength at high temperatures.

Another object of our invention is to provide an apparatus for extruding metal, including means for maintaining the metal in a molten state, means for cooling a suitable die through which the metal is extruded and means for providing tension on the metal as it is extruded.

A further object of our invention is to provide a die which is especially adapted for use in extruding metals at high temperatures and which is composed of an alloy that has a high strength at such temperatures.

In producing seamless steel pipe, it has heretofore been the practice to form the metal into the shape of round billets. The billets were first heated and passed between two angularly disposed steel rolls which rotated in the same direction. When the billet enters the mill, the rolls grasp it at diametrically opposite points on its circumference, and, since the rolls rotate rapidly, these points are continuously changing. In this manner, a small hole is formed through the center of the billet which is rapidly enlarged.

As the billet is delivered from the rolls, it comes into contact with, and is forced over, a piercer v which is a mandrel or block attached to a water-cooled rod. The piercer is located slightly beyond the center of the rolls, so that the billet is forced entirely over the mandrel before it passes from between the rolls. The tube is then subjected to the usual rolling, reeling and sizing processes to produce hot finished tubes to which is added cold drawing to produce cold finished tubes. Such process, however, is comparatively slow and expensive and it is difiicult to obtain pipe having a smooth interior surface.

It has also been the practice to form seamless pipe from metals which have a comparatively low melting point, such as lead, bronze or zinc, by a process which consists in forcing the metal between a die and a mandrel. When attempts have been made to extrude a pipe composed of ferrous material, such as iron or steel, by such process, however, the results have not been entirely satisfactory, because, when the metal or alloy is heated to a temperature slightly below its melting point, it has the tendency to attack and deform thedies.

. We have, made the discovery that, when the lining of the vessel which contains the molten metal, the die and the mandrel are formed of a suitable alloy and, especially, if cooling means are provided for the die. seamless iron or steel pipes may be satisfactorily fabricated.

Our invention will be better understood by reference to the accompanying drawing in which:

Figure 1 is a vertical sectional view of our improved apparatus, and

Fig. 2 is a perspective view of the die, a portion of which is broken away.

Referring to Fig. l of the drawing, a furnace or container 1 is supported on a suitable framework 2. The body of the furnace is formed of a shell 3 formed of refractory material, such as zirconium silicate, a layer of insulating brick 4 andv an outer steel or cast-iron housing 5 which.

is bent inwardly at its lower portion to form a base for the refractory shell, the insulating brick and a die 6 which forms the bottom portion of the furnace or container. The die 6 is composed of a special alloy which is capable of maintaining its strength at comparatively high temperatures, and the shell 3 is provided with a lining 7 composed of a similar alloy.. The lining 7 is painted with a-refractory oxide, such as magnesium oxide or one of the alkaline-earth-metal oxides. designated by the numeral 8, and the die 6 is so situated with respect to the shell 3 and the lining 7 that its interior surface forms a continuation thereof, thereby providing a container 9 for the molten metal. A mandrel 10, which is preferably water cooled, is located centrally of the die 6, thus forming an annular opening 11 through which metal may be extruded.

In practicing our invention, the molten metal is either poured in the container 9 and maintained in a molten condition by inductive heating, orQif desired, the metal may be introduced into. the

furnace in the solid form, and sufficient heat applied to change it to the molten state. The heating may be effected by a conductor 12 em bedded in the refractory shell 3 from which suitable terminals 13 and 14 extend. The conductor 12 is preferably constructed in the form of a hollow tube through which a suitable cooling fluid may be circulated. The die 6 is also provided with a pipe or channel 15 through which a cooling liquid is circulated and is so arranged that it is closer to the surface of the die adjacent to the mandrel than at other portions. I

In practicing our invention, the metal, in a molten state, is forced downwardly by means of a piston 16 which is formed of insulating brick lined with a metal formed of a special alloy, which is also preferably coated with a refractory oxide, such as magnesium oxide or one of the alkaline-earth-metal oxides. The piston 16 is provided with an upwardly extending rack 17 which meshes with a gear 18 extending from the motor 19, thereby providing means for reciprocating the piston. As the molten metal is forced downwardly and approaches the mandrel 10, it comes into contact with the beveled surface of the die 6 and is cooled to a temperature below its freezing point. Upon continued application of pressure, the metal is extruded in a solid state between the die and the mandrel into a suitable pit 20. metal. a clamp, to which a rope or wire is attached, is fastened to the extruded pipe. The other end of the wire or rope is wound around an appropriate motor-operated receiving reel 21, and, as the clamp is pulled downwardly, it aids in the extrusion of the metal. In addition it will be observed that the force of gravity assists in the extrusion process and becomes increasingly effective as the tube being extruded becomes longer to pull the tube through the die 6.

The mandrel 10 is provided with a cooling chamber 23 and is mounted on the upper end of a support member 24 which is provided with tubular openings 25 and 26 that enter into the cooling chamber 23 to provide for circulating the cooling medium therethrough. The support member 24 is mounted on a suitable base 27 which is located on the floor of the pit 20. An intake pipe 28 and an exhaust pipe 29 are provided for supplying the cooling medium to and removing it from the base 27 which may be provided with any suitable connections to the openings 25 and 26. It will be observed that the support member 24 and the base 27 are centrally loeated relative to the die 6, thereby serving to maintain the mandrel 10 centrally located and the annular opening 11 of uniform thickness.

It is necessary for the successful operation of the process that the die and the mandrel shall all be formed of metal having a high thermal conductivity, a high resistance to abrasive action and a high strength, especially at high temperatures. An alloy which meets the above re quirements is fully described and claimed in the copending application of Erwin S. Lowry, Serial No. 403,664, filed on October 30, 1928, which is assigned to the Westinghouse Electric and Manufacturing Company. This alloy comprises nickel and cobalt and, in its preferred form, contains iron and titanium. The cobalt-plus-nickel content ranges from 70% to 95% of the alloy, and the iron constitutes approximately threefourths of the remainder. Alloys of this type are characterized by having a nickel-cobalt base and contain one or more ingredients which are In order to aid in the extrusion of themolten metal.

elfective in increasing their strength at high temperatures, such as chromium, titanium, molybdenum and vanadium. An alloy of this type, which we have found to be especially suitable, is composedof the following ingredients in the proportions indicated:

Per cent Nickel 51 Cobalt 29 Iron 7.5 Titanium 2.5 Molybdenum 10 An alloy having the desired characteristics may also be obtained by substituting chromium for the titanium and molybdenum, as illustrated in the following example:

Per cent Nickel 47 Cobalt r- 29 Chromium 16 Iron 6.5 Silicon Manganese 2 Aluminum We have also found that other alloys, especially those having a tungsten or a tungsten-carbide base, are suitable for our purpose. For example, an alloy containing approximately to 95 U0 powdered tungsten may be bonded together. under heat and pressure, with from 5% to 25% of an alloy containing a nickel-cobalt base, such as those mentioned specifically above or those described in the copending application of Lowry, and a final product will be obtained having comparatively high strength at high temperatures, or, if desired, tungsten or tungsten-carbide particles may be bonded together by means of copper, chromium nickel or cobalt alone. In general, it may be stated that alloys having a nickelcobalt or a tungsten or a tungsten-carbide base are satisfactory. The essential requirements of the alloy are that it shall have a high thermal conductivity, a high resistance to abrasive action and high tensile strength, especially at high tem-' It will be noted that the lining, the dies and the mandrel and the facing of the piston are all composed of one of the special alloys. In practice, we prefer to coat the lining for the wall and piston with magnesium oxide because it has the tendency to adhere tov the surface of the lining and minimizes the destructive action of the The cooling coils in the die are also arranged in such manner that they are closer to the surface of the die at a position adjacent to the mandrel than at other portions. The cooling fluid also enters the die at its lower portion andpasses out at the upper portion so that more heat is extracted from the metal at a point adjacent to the mandrel.

By utilizing an apparatus having a die, a cylindrieal lining and amandrel composed of an alloy having relatively high-temperature-resistance characteristics, various metals, such as iron or steel tubes, pipes or cylinders may be successfully extruded.

While we have described our invention in considerable detail and have given specific examples, it will be understood that the examples are to be construed as illustrative and not by way of limitation. For example, we do not desire to limit the invention to the extrusion of pipes or cylinders as it may obviously be employed for the extrusion of rods or other shapes. The process and apparatus may also be employed for the extrusion of pipes or cylinders from metals having a lower melting point, in which event, the operation may be materially expedited.

Other modifications of our invention will become apparent to those skilled in the art. We desire, therefore, that only such limitations shall be imposed as are required by the prior art and the appended claims.

We claim as our invention:

1. Apparatus for forming an extruded metal article comprising, in combination, a reservoir for molten metal terminating in an elongate and generally conical forming throat, said throat being provided with cooling means extending along its forming surface to solidify the metal gradually as it progresses through the throat, and means to force molten metal under pressure from the reservoir through the cooled forming throat and to extrude plastic, solidified metal.

2. Apparatus for forming an extruded metal article comprising, in combination, a reservoir for molten metal terminating in an elongate and generally conical forming throat, said throat beits forming surface to solidify the metal gradually as it progresses through the throat, and means to force molten metal under pressure from the reservoir through the cooled forming throat and to extrude plastic, solidified metal, said last named means comprising means at the throatoutlet to apply tension to the article to assist in'the extrusion process.

3. A process of forming an extruded metal article comprising maintaining a body of metal in molten condition, forcing a portion thereof to flow downwardly under pressure in a relatively small stream and by gravity flow from the body of molten metal maintaining a supply of molten metal to the stream, progressively cooling the exterior of the stream of metal until the stream becomes solid throughout and plastic, and immediately extruding the solid metal while it is plastic.

4. A process of forming an extruded metal article comprising maintaining a body of metal in molten condition, forcing aportion thereof to flow downwardly underpressure ina relatively small stream and by gravity flow from thebody of molten metal maintaining a supply of molten metal to the stream, progressively cooling the exterior of the stream of metal until the stream becomes solid throughoutand plastic, and immediately extruding the solid metal while it is plastie and applying tension to the metal as soon as it is extruded. j

' WILLIAM B. SHIRK.

PORTER H. BRACE.

- NEW'BOLD C. GOIN.

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