US 2757138 A
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United States Patent METAL EXTRUSION LUBRICATING COMPOSITION No Drawing. pplication June 16, 1952, Serial No. 293,849
Claims priority, application France June 18, 1951 14 Claims. (Cl. 252-12.6)
This invention relates to the extrusion of metals and alloys, more particularly though not exclusively stainless and other alloy steels. 1
In the extrusion of such steels, a billet or ingot of steel heated to an appropriate temperature is inserted into a cylindrical extrusion chamber or container having one end thereof defined by a die plate provided at its centre with an extrusion orifice, and the metal is then expelled out of the container through the die orifice in the form of a bar or tube for example, by applying suitable pressure to the end of the billet remote from the die.
It is essential if the extruding operation is to proceed successfully, that the metal should not be subjected to an excessive temperature drop as it issues through the die, since otherwise the die orifice would be obstructed by a plug of solid or near-solid metal soon preventing further extrusion. At the same time, it is necessary to prevent excessive heating of the die. With the purpose of meeting both these requirements, it has been proposed thereof defined by the die plate, a glass disc adapted to serve as a thermal insulation between the front end surface of the steeljbillet and the die plate, and thereby prevent both excessive cooling of the metal and heating of the die. On application of the extruding pressure to the rear end of the billet, the glass insulating disc is perforated at its centre and thus enables the metal to pass through the die.
The method just described, however, does not yield wholly satisfactory results, and its use is not without its drawbacks. In the. first place, fragments of broken glass are carried to various points of the extruding apparatus and result in premature wear therein due to their abrasive action. Moreover, the lubricating effect exerted in this method by the molten glass gradually diminishes as the temperature of the billet falls, owing to the fact that the increasing pressure expcls the molten glass from between the adjacent surfaces of the billet and the die plate.
Our present invention overcomes these and other drawbacks.
It is an object of the invention to provide an improved method of extruding metals and alloys, particularly though not exclusively alloy steels, whereby selected adjacent surfaces of the body of metal to be extruded and of the extruding chamber or die therefor, may be effectively thermally insulated from one another, Without incurring wear and abrasion in the extruding assembly.
Another object is to improve the extrusion process of difiicultly extrudable metals, including alloy steels, by simultaneously providing for a heat insulation of selected adjacent surfaces of the extruded metal and an extruding chamber and/or die therefor, and for a lubrication of said surfaces, both provisions being effected by means of a common and simple step.
A further object is to provide such an improvement whereby the lubricating effect will increase as the extruding pressure is itself increased.
A further object is to decrease the temperature drop to insert into the extrusion chamber, against the end wall in the extruded metal and the correlative temperature rise in an adjacent part of an extruding chamber and/or die therefor, such object being attained simultaneously with any one or more of the precedingly specified objects.
Further objects include the provision of an improved heat-insulating composition for use in the extrusion of metals for the purpose described; the provision of such a composition which will simultaneously exert a beneficial lubricating action, and one which will exert an increasing lubricating action as the extruding pressure increases; and the provision of such a composition which is adapted to evolve heat spontaneously during at least an initial stage of the extruding operation to substantially compensate for the temperature drop in the metal being extruded.
Yet further objects relate to the provision of selfsupporting shaped elements made from such compositions and usable in attaining the first mentioned objects specified above.
According to the invention, there is essentially provided a heat-insulating element adapted to be interposed between at least one surface of a body or billet of metal to be extruded and an adjacent surface of an extrusion chamber or die therefor, which element is characterized in that it is made of an agglomerated, porous, heatinsulating material free of any abrasive constituents therein. The invention contemplates including among the constituents of the material or composition from which the element is made, in addition to a heat-insulating constituent, a lubricant constituent in the form of a suitable lamellar or flaked solid adapted to withstand the high extruding temperatures, such as flaked graphite.
A heat-insulating and/ or lubricating element according to the invention is preferably provided in the form of a self-supporting cake, disc or slab, shaped for insertion between the front end of a billet to be extruded and the adjacent surface of the die plate. Such an element may, however, be further inserted between the rear end of the steel billet and the adjacent surface of the pressure applying member, such as a presser ram. Alternatively or in addition to the above locations, an element according to the invention may be slipped around an axial die core member in connection with the extrusion of tubular products. In such case, the element would of course be shaped as a tubular sheath rather than a disc.
In 'a preferred form of the invention, the composition from which the heat-insulating element is made includes constituents adapted to react exothermically with one another at the extrusion temperature. The heat evolved by this reaction will serve to compensate for the drop in temperature occurring on the end of the billet and thus greatly facilitate the initial stage of the extruding operation.
The lubricant constituent which, as stated, is preferably included in the composition of the heat-insulating element, is a lamellar solid capable of resisting the high temperatures used, and preferably comprises graphite. Provision of this solid lubricant greatly promotes the flow of metal through the die. The use, as a lubricant, of a solid possessing a lamellar structure is particularly advantageous in that the relative displacement of the flakes or lamellae, which displacement is responsible for the lubricating effect, is precisely produced by the application of pressure, and hence increases with the pressure; thus the lubrication increases with the pressure.
The essential heat-insulating constituent of the material used according to the invention may comprise any suitable non-abrasive combustible organic substance, in a high state of division, such as sawdust, pulverized cork or straw, or the like, which substance is mixed with a highly divided carbon constituent, such as carbon black, and with a super-oxygenated substance adapted to react exothermically with the carbon at high temperature, for example a suitable metal oxide such as pyrolusite, lead dioxide or bismuth tetroxide.
The above constituents, preferably including the graphite, are agglomerated with the use of a suitable binder, suchas a natural or synthetic resin, pitch, or an agglomerant vegetable oil, particularly linseed oil.
One typical example of a composition which has been found suitable for use according'to the invention is the following:
Percent by weight Sawdust about Flaked graphite 60 Carbon black 23v Pyrolusite 3 Linseed oil 4 The above constituents aremixed in any suitable mixer and are then moulded manually or mechanically in a suitably shaped mold under moderate pressure in order to preserve in the final agglomerate a substantial degree of porosity enhancing the heat-insulating characteristics thereof. The molded product is then subjected to a baking operation at a temperature selected in accordance with the nature of the binder used.
In the manufacture of extruded tubular products, the axial core member or mandrel of the die serving to produce the tube may desirably be surrounded by material; similar in nature to that described hereinabove. In this case, the material may either be applied as a coating, spread around the periphery of the core, or as a selfsupporting tube or sheath prepared in advance, to be slipped about the core or mandrel.
While the invention is particularly applicable to theextrusion of stainless and other alloy steels, it is equally applicable in the case of other metals and alloys and makes it possible readily to extrude metals which it was heretofore considered difficult to work in this manner.
It will be understood that any ingredients and proportions specified herein are given primarily by way of: illustration and should not be taken as restricting the scope of the invention, the limits of which are defined in the claims.
What we claim is:
1. A solid, infusible heat-insulating and lubricating. composition adapted for interposition between one surface of a metal body to be extruded and. an adjacent surface of an extruding assembly therefor, consisting mainly of a heat-insulating, porous, non-abrasive organic substance in a finely divided state, flaked higher metal oxide selected from the group consisting of pyrolusite (manganese dioxide), lead dioxide and bismuth tetroxide, and finely divided carbon black, said materials being present in suflicient amounts to produce an: exothermic reaction at the extrusion temperature, and a combustible binder selected from the group consisting of natural and synthetic resins, pitch and agglomerating. vegetable oils.
2. The method of preparing a solid, self-supporting, infusible, heat-insulating and lubricating element adapted graphite, a
to be inserted between one surface of a metal body to be extruded and an adjacent surface of an extruding assembly therefor, which comprises preparing a mixture consisting mainly of a heat-insulating, porous, combustiole non-abrasive organic substance in a divided state, flaked graphite, a higher metal oxide selected from the group consisting of pyrolusite (manganese dioxide), lead dioxide and bismuth tetroxide, and finely divided carbon black, said materials being present in sufiicient amount to produce an exothermic reaction at the extrusion temperature, and a combustible binder selected from the group consisting of natural and synthetic resins, pitch and agglomerating vegetable oils for agglomerating the said materials, feeding the said mixture to a mold and molding same under moderate pressure to retain substantial porosity in the molded element, and finally baking said molded composition at a temperature selected in accordance with the nature of the binder.
3. A solid, infusible, heat-insulating and lubricating composition adapted for interposition between one surface of a metal body to be extruded and an adjacent surface of an extruding assembly therefor, consisting of, by weight, about 10% of a heat-insulating, porous, nonabrasive, combustible organic substance, about of flaked graphite, about 23% of carbon black, about 3% of a higher metal oxide selected from the group consisting of pyrolusite (manganese dioxide), lead dioxide and bismuth tetroxide, and about 4% of a combustible binder selected from the group consisting of natural and synthetic resins, pitch and agglomerating vegetable oils.
4. A solid, infusible, heat insulating and lubricating composition adapted for interposition between one surface of a metal body to be extruded and an adjacent surface of an extruding assembly therefor consisting of:
Percent by weight Sawdust about 10 Flaked graphite about 60 Carbon. black about 23 Pyrolusite about 3 Linseed oil about 4 References Cited in the file of this patent UNITED STATES PATENTS 494,156 Newell Mar. 28, 1893 494,433 Newell Mar. 28, 1893 621,797 Curtis Mar. 28, 1899 2,038,215 Gillis Apr. 21, 1936 2,466,642 Larsen Apr. 5, 1949 2,538,917 Sejournet et al Jan. 23, 1951 2,588,418 Sehaller Mar. 11, 1952 FOREIGN PATENTS 220,633 Great Britain May 21, 1925 712,007 Great Britain July 14, 1954 234,397 Switzerland I an. 16, 1945 OTHER REFERENCES Bastian: Metalworking Lubricants, McGraw-Hill Book C0,, Inc., New York, 1951. (Copy in Div. 64.)