US2131062A - Treatment of metal - Google Patents

Description

Sept. 27, 1938.

S. R. M BRIDE TREATMENT OF METAL Filed Feb. 11, 1936 I INVENTOR.

ATTORNEYfi,

52 awa q, 52

Patented Sept. 27, 1938 V PATENT OFFICE 2,131,062 TREATMENT or METAL Samuel Ross McBride, Ravenna,;hio, assignor to H. L. F. Company, Los Angeles, Cali1'., a corporation of California Application February 11, 1936, Serial No. 63,385

' 1 Claim. (Cl. 22-212) In the preparation of metals for certain uses it has been customary to mechanically work the. metal, such as by rolling, which for example is the particularly feasible large scale commercial method. This has been necessary by reason of the fact that metal as cast is essentially crystalline and of poor and irregular texture, and being deficient in tensile strength. Chill-casting, while providing a particular surface-hardness has aggravated the difliculties in other directions. In

accordance with the present invention however, it now becomes possible to treat metal to attain mechanical properties of peculiarly advantageous character, and in a manner readily applicable.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described, and particularly pointed out in the claim, the following description and the annexed drawing setting forth in detail certain illustrative embodiments of the invention, these being indicative however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawing: Fig. 1 is a perspective view of apparatus contemplated in the invention; Fig. 2 isa similar view of further detail; and Fig. 3' is a fragmentary sectional view of mold-wall structure.

In working metal by rolling, the structure is in effect compressed in one direction and the grain structure is correspondingly elongated. On the other hand, in casting as customarily practiced,

the grain structure or crystalline detail takes its position promiscuously, and generally within the body of the mass the crystalline size reaches con- I siderable magnitude. Where. the metal is chillcast, the growth of large crystalline structure at the surface is prevented, but the mass of the metal internally is irregular. In accordance with the present invention, metal is subjected to what is in effect the molecularly drawing of the metal progressively by changing it from the liquid to solid state by an advancing front through the mass treated. Formation of macro-crystalline structure is thus impossible, and compression or drawing action is applied progressively and regularly in situ. 'In this, whereas in rolling for instance, compression is applied in one dimensional direction, by the present procedure the com-, pressional action is simultaneously efiected in both dimensional directions for any given section plane. The metal thus treated by controlled progressive molecular drawing action is characterized by properties none .of which have been known to cast products, and some of which have not been heretofore attained by any known procedure. It thus becomes possible to produce structures of unique properties, and where longknown' alloys are treated, metal products with 5 newly adapted, utilities may be had. For instance aluminum alloys as prevalently cast into cylinder heads for internal combustion engines, which have heretofore been characterized by theutmost unevenness of texture, exaggerated grain and ir- 10 regular brittleness, when formed into similar shapes by the present invention are characterized by an outstanding evenness of texture and great toughness. Similarly, brass and bronze alloys in accordance herewith yield products having en- 15 hanced tensile strength and evenness of texture. With all of these also, the Brinell hardness may be controlled to particularly advantageous degree.

The casting molds here employed have a wall 20 structure which is not capable of storingsubstantial amounts of heat. Physically, the mold walls are in general quite thin, and the heat-control is efiected by temperature change progressively applied. Asillustrated in Fig. 1, there is shown 25.

a mold 2 of very thin wall structure, this being mounted on a suitable support 3; and there being suitable sprue access 4 to the mold cavity. While.- a progressing cooling zone may be provided by progressively relatively raising a water level about 30 the mold, I prefer a traveling temperature-control means comprising a jetting device 5, in suitable form, for instance an annular hollow tube with multi-perforations directed radially inwardly toward the mold, and having a flexible tubular 3 connection 6 to a suitable source of cooling fluid,

the traveling evice being mounted to slide on a guide I and eing propelled advancingly by a driving meansr as for instance a screw-stem 8 which is drive through bevel gearing 9 and re- 40 duction gearin Ill by amotorl I.

The molten etalis poured into the mold 2, and the tempo ature control device 5 is set inmotion by the otor I I, and progressively travels from the bottom to the top, jetting the cooling fluid against the walls of'the mold, and correspondingly'abstracting the heat therewithin and setting the metals in a gradually progressing manner. The cooling fluid will depend somewhat upon .the particular metal being :treated.

While for quite low meltingpoint alloys jets of cold air are suitable, in general water or some aqueous solutionds suppliedthrough the cooling ring 5. Where itis desired, the progressive cooling action may be 'applied to a part of the mold instead of its entirety, and in general the action The latter, depending upon the thickness of section of metal to be cast may beof greater or less section. Thus, with the casting of moderate size ingots. a painted-on coating about 1?; inch thick, of refractory material, such as magnesium oxide with a binder is satisfactory. A particularly advantageous lining material is a composition of zirconium oxide and magnesium oxide, the latter being predominant, and this is satisfactory for large scale ingot casting, a coating of lining inch thick being advantageous as sufficient protection for the metal shell. The magnesia and the like may be made up with phosphoric acid or other binders such as sodium silicate etc. Other refractory materials, as sillimanite, bauxite, kaolin. etc., may be used, alone or in mixture. The metal shell for heavy ingot casting may be of thickness about. inch advantageously.

Slightly different effects may beattained, depending upon whether ,the progressive temperature controlling action be started immediately or after allowing the molten metal to stand for a short time. This would depend also upon the particular metal or alloy being cast. By advancing the cooling zone such that the in-pouring metal raises its level in advance of the traveling cooling zone, such lead of temperature differential allows all gases to escape, and the cooling area or section is at all times amply supplied with filling-metal, and a fine even texture free from porosity and piping is had, while the hardness of the casting is approximately the same through its entire cross'section. In some cases, it is advantageous to apply a heating means 15 to the top portion of thev mold, so as to maintain a highly fluent condition of the metal continuously at this point while the progressing wave of setting up traverses the body. Preliminary heating of the entire mold or heating the mold progressively before the rising level of the incoming metal is in fact advantageous in certain cases.

Where a core is required, as for instance core l2, Fig. 2, it may be held below in a support it and above by adjusting screws I4.

As illustrating the niceties of gradation of properties here possible, a bronze alloy of for instance 70 per cent copper, 8 per cent tin, and 22 per cent lead, where cast into bearing pieces of cylindrical or semi-cylindrical contour, with the cooling wave started immediately from the bottom of the mold progressively to the top, yields a product in which the cellular wall structure of the copper-tin matrix is very thin. While, 11' the same alloy is allowed to stand in the mold one-half aminu te before the temperature-control device is started on its travel up the mold, the cellular walls of the copper-tin matrix are heavier and the lead is not so finely dispersed. This difference in structure effects a diiferenoe in the wearing qualities of the bearing bronze. The hearing which is immediately treated as above noted, will wear more rapidly than the bearing with the delay-treatment, but will cause less wear of. the shaft which is supported. Such difierences in wearing life are advantageous in some usages, and a successful manner of attaining precisely conrolled results is thus very important.

With some shapes of desired metal products,- the controlled progressive cooling of the metal may be best effected from the interior. Thus, a hollow body may be arranged with traveling cooling-head in the core.

As illustrative of products attainable, a few instances may be noted. An alloy of 70 per cent copper, 8 per cent tin, and 22 per cent lead when thus cast has a Brinell hardness 65-70, tensile strength 29,000-31,000, and compression 26,000-29,000. This same alloy when cast in sand by conventional practice has Brinell hardness 48-52, tensile strength 23,000-24,500, and compression 14,000-16,000. An alloy of 88 per cent copper, 8 per cent tin," and 4 per cent lead when cast in a sand mold by ordinary procedure, has a Brinell hardness 60-65, elastic limit 18,000-21,000,.

ultimate 28,000-32,000, and elongation in 2 inches 18-20. But, the same alloy when treated in accordance with the present invention has a Brinell hardness 93-98, elastic limit 22,000-25,000, ultimate 41,000-43,000, elongation in 2 inches 15-16. Again, a brass (66 per cent copper and 34 per cent zinc) when produced by the old methods, as casting and then hard rolling, has an elongation 4-5, tensile strength 56,000-61,000, and Brinell hardness 71-75. The same brass alloy when treated in accordance with the present invention has an elongation 7-8, tensile strength 54,000-59,000, and Brinell hardness 75-78, thus representing a combination of properties not attainable by hard rolling, and having however tensile strength which is comparable. A gear bronze alloy (89 per cent copper and 11 per cent tin), when treated by my process has an elastic limit 30,000-31,000, ultimate 50,000-52,000, elongation 9-1-10, reduction of area 7-8, and Brinell hardness 100-102. Again, electrolytic copper where ingot-cast in accordance with ordinary practice is of very uneven texture and low tensile strength, but when treated in accordance with the present invention has a tensile strength of 37,000-39,000, elongation 36-39, and reduction of area 47-52. Gray iron (silicon 2.80, total carbon 3.25, and manganese 0.60) when formed-in cylindrical shapes in accordance with the present invention for pump liners has a Brinell hardness 210-212, and compression 115,000-118,000. It is notable also that it is hereby possible to use even quite poor grades of metaland still get good texture products. customarily for instance there is great particularity in the choosing of metal free from phosphorus and the like, in order to prevnt excessively poor structure.

The refinement of texture now attainable how- F., or as low as possible, in order to keep the lead segregating. The products have had Brinell hardness of 60-65. Such alloys could not from be handled in chill molds at all. on account of scaling and blistering. With the present procedure, I can pour these alloys at 2350" F., and the texture is outstandingly better. Thus, such a high lead alloy per cent lead, 5 per cent tin, 70 per cent copper) yields a Brinell hardness of 15-80. Again, if a hard bushing alloy (88 per cent copper) be cast in sand at 2000-2050 F. as

in the old practice, the product has Brinell hardness 60-66. Treated however by the present process, and poured at a temperature of 2350" .F.,

the product has a Brinell hardness of 100. The wearing life'of such a bushing is 3-4 times longer than that of the former. a

The specific gravity of products of the present" procedure is notably higher than that of products of sand molding or chilled molding. With bronze bushings for instance, this is an 8 per cent increase. The increase in specific gravity is the result of the higher density due to the compression-action impressed upon the metal by the progressive setting-up wave in its controlled course. Such compression here however is further bi-dimensionally exerted progressively on the metal section, instead of mono-dimensionally as in the rolling process. Thus it is, that not withstanding the greater simplicity of treatment, products compare favorably as to tensile strength with rolled products as heretofore had, and. besides aflord additional characteristics not attainable in rolled products.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in the following claim, or the equivalent of such, be employed.

I1 therefore, particularly point out and distinctly claim as my invention:

A device for treating metals, which comprises a ring member comprising a plurality of jets for fluid arranged in a common plane, a movable carrier therefor, flexible connections from a source of fluid-supply to said Jets, acylindrical mold with a wall having substantially no inherent capacity for-chilling molten metal in contact with it, said mold being exposed to said jets, and means for controllably moving said ring of jets progressively along the wall of said mold coordinated with the pouring or the metal into the

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