US1755913A - Process for producing composite metals - Google Patents

Description

Patented Apr. 22, 1 930 UNITED STATES PATENT OFFICE,

HENRY L. COLES, OF' HAMILTOLI, OHIO, ASSIGNOR TO GUARDIAN METALS COMPANY, OF HAMILTON, OHIO, A CORPORATION OF DELAWARE PROCESS FOR. PRODUCING COMPOSITE MET ALS No Drawing. Original application filed November 22, 1927, Serial No. 234,957. Divided and this application filed November 9, 1928.

This application is a division of my appli-- cation, Serial N 0. 234,957, filed November 22, 1927, for composite metals and process for producing the same. 5 This invention relates to an improved process for fabricating composite. metal plates and the like. In my application above referred to, there has been described a process for fabricating composite metal plates, and more particularly the improved product resulting from such process. In the present case, in order to secure intimatecontact between the metal of the core and of the sheath to' form a composite or compound metal plate, the core members are first subjected to a preliminary treatment.

In this treatment the metallic core is sandblasted or otherwisetreated to remove surface matter such as oxidesand the like, after 2 which it is sprayed with a concentrated solution of a nitrogenous material such as alkali nitrite, my preferred composition being sodium nitrite (NaNo The function of the sodium nitrite is to improve the wetting qualities of the core metal and adapt it to be wetted by the molten sheathing material or' metal such as copper or the like. Usually after spraying, heat is applied by a torch to dry the core, care being taken to restrict the an amount of heat to that necessary for drying, without effecting any substantial decomposi tion of the sodium nitrite. The result of this treatment is ametallic core intimately coated with a layer of the sodium nitrite. When molten metal, such as copper, is cast in and around such a core member, it decomposes the sodium nitrite, liberating quantities of gases such as nitrogen which serve to force out the air from the mold chamber and to 40 provide .substantially oxygen-free atmosphere therein. This freedom from oxygen prevents the formation of the noxious oxides of copper, and with these oxides absent, the unalloyed character .of a highly refined sheath metal may be preserved.

A particular example of the im roved results to be procured by the application of the present process is in the casting of com;

pound metal bodies for use in the manufac- 'ture of burglar-proof safes and vaults, as

Serial No. 318,313.

exemplified in my present application, above noted, in which a metallic core of drill-proof metal composition or alloy, of the types disclosed in my co-pending applications, Serial Nos. 730,194 and 86,034, (in which the compositions include preponderating amounts of tungsten with minor amounts of molybdenum, carbon or copper, or ferrous alloys having a high percentage of chromium and mangenese) is formed into any desired configuration, and intimately coated with a concentrated solution of sodium nitrite. These sotreated' bodies are then placed in a mold, or they may be preliminarily placed in a mold and the nitrite solution applied by spraying, after which a suitable sheathing metal such as copper is poured into the mold. During the casting operation the molten metal is preferably poured as slowly as is consistent with results to be obtained. The

primary consideration is that the molten metal shall contact with the core metal at such a rate of speed as will insure an adequate preheatin thereof without chilling the pour. This pre eating also serves to decompose the nitrite coating, setting free gaseous nitrogen and its oxides, which, as has already been pointed out, sweep out the air from above the surface of the advancing metal.

The alkali molecules set free by the decomposition of the nitrite unite with any siliceous impurities present, and form a freeflowing slag coating over the surface of the pour, thereby adding an additional protective agent to co-actwith the gaseous blanket previously described. The thorough cleaning which the surface of the core metal undergoes, as a result of this treatment, greatly enhances the wetting capacity of the molten metal by assuring an absolutely clean metal to metal surface. The advancing metal flows into and through the interstitial spaces between the slats of which the core is preferably formed, forming a substantially contin uous sheath therearound; and being in intimate contact therewith,the result is essentially a composite metal plate comprising a hard core of drill-resistant metal and an outer protecting sheath of ductile and comv solutionof the constituents of the several alloys proceeds under optimum conditions, and the core and sheath are joined in a substantial mono-metallic structure.

The processherein described is adapted for a wide variety of metallurgical purposes, and more particularly for the casting. of nonferrous metals generally, which are readily oxidized in their molten condition. The ease of decomposition of this material, sodium;

nitrite, is of particular i ortance in the present invention, as it afior s a ready means of providin a non-oxidizing atmosphere in casting mol and the like without involving the necessity of using gaseous nitrogen, or other non-oxidizing gases with the attendant trouble of the apparatus'required.

' By way of rsum it will be noted that by merel coating the'mold walls'with a concentrate solution of sodium' nitrite, or any other suitable compound, such as the other alkali nitrites, the molten metal in contact with the mold walls readily decomposes the alkali nitrites, -co ious volumes of nitrogen gas is set free an acts to sweep, or force out. any air present from the mold chamber; In addition, the alkali residues set free by the liberation ofthe nitrogen component react with any siliceous material present to form a freeflowing slag which covers the top of the advancing metal, thus co-operating with the non-oxldizing gaseous blanket to prevent any contact between the metal and the outside air. Where core members of non-ferrous metal are used, the cores are previously coated with the concentrated nitrite solution, and due to the vigorous chemical action between the con stitutents of the nitrite compound and any non-metallic impurities which may be present on the surface of the core under the influence of the molten metal, the core surface is thoroughly cleansed and presented to the advancing metal, not only in a condition wherein it is free from occluded oxygen and the like, but also in which it is particularl adapted to combine or alloy with the sheet metal, where such alloying is possible.

Itwill' now be appreciated that there has been provided an improved process for the 'productionof composite metal castingsythis process being characterized by the discovery that the presence of an alkali nitrite in the mold, or,applied to= a core member in a mold,

enables the ready preparation of diflicult castings without involving any great expense in special machinery required forgaseous deoxidants of like blanketing materials.

3. A- method of producing compound metallic plates, comprising coating an apertured core member with sodium nitrite and casting a sheath of metal in and around the core.

4. A method of producing compound metallic structures comprising coating an apertured core member with sodium nitrite, casting a sheath of metal around the core under determined conditions of temperature and rate of pour, whereby to assure optimum conditlons' of reaction. 1

5. A method of producing burglar-proof safes, comprising forming a drill-proof core member, spraying the core with sodium nitrite, and casting a heat-conductive metal in and around the core.

-6. A method of producing burglar-proof vault doors, comprising formmg a drillproof core member, spraying the core with an alkali nitrite, and casting a sheath of heatconductive metal in and around the core.

7. A method of producing compound metallic plates, comprising casting a sheath of metal around a metal core member in' the presence'of nitrogen liberated in situ.

8. A method of producing compound metallic plates, comprising casting a sheath of metal around a metal core member in the presence of nascent nitro en,

9. In the production of metallic compound plates having an inner core member and an external sheath cast therearound, the improvement which comprises simultaneously cleansing the surface of the core member and forming a non-oxidizing protective atmos-' phere about the said core by reacting the molten sheath metal with a compound adaptgd to liberate nitrogen gas and an alkali resi- 10. In the production of compound methe mold with a nitrogenous compound adapted .to liberate nitrogen gas and a slag-forming residue when strongly heated, and flowing a molten sheath of metal into said mold and around said core, whereby to form an atmosphere of nitrogen gas in the mold cham- 1 her and a free-flowing slag coating on the said flowing molten metal.

This specification signed this 8th day of November, 1928.

HENRY L. COLES.