US2482899A - Corrosion-resisting composite metal - Google Patents

Description

Sept. 27, 1949. P. G. CHACE 7 2,482,899

coanos xou-nssxs'rms COMPOSITE METAL Original Filed June 25, 1941 Patented Sept. 27, 1949 I UNITED STATES PATENT "OFFICE 2,482,899

Paul G. Chace, Attleboro Falls, Mam, assignor to Metals and Controls Corporation, Attleboro, Mass., a corporation of Massachusetts Original application June 23, 1941, Serial No.

399,398, now Patent No. 2,366,178, dated January 2, 1945. Divided and this application November 11, 1944, Serial No. 563,015

Claims. (CL, 29-1955) application, Serial No. 399,398, filed June 23,1941,

Patent 2,366,178.

Among the several objects of the present invention are the provision of a composite thermostatic metal which is corrosion-resisting, which has an improved bond, and which has a long life when operating in corrosion-promoting atmos pheres and mediums; the provision of composite thermostatic metal of the class described which has both good hot-rolling and good cold-rolling properties; and the provision of composite thermostatic metal of the type indicated which is relatively simple and economical to manufacture. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the ingredients and combinations of ingredients, the proportions thereof, and features of composition, which will be exemplified in the products hereinafter described, and the scope of th application of which will be indicated in the following claims.

In the accompanying drawing in which is 111115? trated one of various possible embodiments of the invention, the single figure is a representation of a bimetallic element showing a strip of iron chromium alloy fused throughout its length to a similar strip of copper silicon alloy.

Many of the thermostatic elements commonly in-use are subject to corrosion when used in the presence of moisture in places such as steam radiators, or water mixing valves, or in other installations where corrosion-promoting fluids or atmospheres come in contact with the thermo-.'

static metal. As a result, such elements frequently need replacing, and inasmuch as corrosion tends to reduce their activity and life, such corrosion may set up, unknown to the user, dangerous conditions which might result in loss of life or injury. To avoid this corrosion of the composite metal element, it has sometimes been customary in the past to treat the thermostatic metal surface to make it less subject to corrosion, as by plating it with a corrosion-resisting material, such as cadmium, tin, zinc, lead, or chromium. This, however, has the disadvantage that the plating increases the cost materially and does not assure satisfactory life for the thermostatic element. Furthermore, such plating is not entirely satisfactory since an electro-voltaic potential may be set up which produces pitting and eating away of the protective metal.

It has sometimes been the practice in the past to make a composite metallic element from an iron alloy having a high chromium content, and a metal alloy having a higher coefficient of expansion. The metal used for the high coefficient of expansion side has been one of the brasses. The mechanical properties of these brasses have presented manufacturing difficulties, which in many instances have prevented the manufacture of an adequate and satisfactory composite metal. For example, the cold-working properties of brass are so different from those of the chromium iron alloy that it has been diflicult to satisfactorily cold-work the metal afterv it has been put together to form a thermostatic bimetal. Moreover, it is highly advantageous in the manufacture of bimetal to hot-roll the material down from its thick ingot size to an intermediate stage. The brasses are not adapted to this, since their hot-rolling temperatures differ too much from that of the chromium iron alloy. The manufacture of the brass-chrome iron bimetals has therefore been a relatively expensive process compared to the manufacture of bimetal in accordance with the present invention. The ingot size of the brass-chrome iron bimetals must be kept small because of the aforementioned difliculties and properties.

Where other constituents have been proposed for corrosion-resisting bimetals, it has been found relatively impossible to directly bond the metals together. For this reason, an intermediate solder layer has been used which has led to two serious disadvantages. First, the use of the solder layer decreases the corrosion-resisting property of the thermostatic metal due to inferior bonding, and second, the solder layer decreases the strength of the metal at elevated temperatures, since the solder bond is relatively weak. Also, solderbonded material is diflicult to hot-roll satisfactorily.

By the present invention, it is possible to accomplish a direct bond between the metals, and they may be hot-rolled or cold-rolled in the desired manner. Their manufactur is accordingly economical, and a highly corrosion-resisting thermostatic metal is obtained.

According to the present invention a thermostatic element is provided which is corrosionresisting per se, particularly to air, water and water vapor, thus eliminating the need for surface plating. In addition, the present invention provides a thermostatic element made of composite thermostatic metal of the corrosion-resisting type which has a direct bond between the layers thereof.

The thermostatic metal or the present inven- Per cent Manganese 0.2-0.6 Carbon 0.01-0.2 Chromium 12-20 Silicon -1.5 Copper 0-1.5 Iron Remainder For the high expansion material an'alloy of copper and silicon is employed. The composi-.

tion of this alloy may be as follows:

Per cent Copper 96-99 Silicon 0.5-4 Manganese 0-1 Tin 0-2.5

The composite thermostatic metal of which bimetal will be described as an illustrative embodiment may be formed in any of the customary manners. It is preferably formed in one of the ways described in my co-pending application, Serial No. 399,398, filed June 23, 1941, Patent 2,366,178, reference to which is hereby made.

Referring now to the drawing, the single figure illustrates a bimetallic element composed of the two alloys discussed above. Numeral l represents the copper silicon alloy while 3 is the iron chromium alloy.

The tensile strength and other mechanical properties of the copper silicon alloys described are sumciently near to the same properties of the chrome-iron alloys that the two metals work well together and may be easily cold-worked. This makes the manufacture thereof more economical; As a result of obtaining a direct bond between the metals comprising the present invention, a thermostatic metal having a higher strength, greater activity, wider usable temperature range, longer life and better corrosion-resisting properties than the corrosion-resisting bimetals hitherto known, is obtained. Former metals allegedly designed to have these desirable properties have instead been relatively weak, corrode relatively easily, are more diflicult to manufacture, and in general are not satisfactory.

As specific examples of alloys which may be advantageously employed in the present invention, the followingexamples are given. They are illustrative only:

Chrome-iron alloy Attention is directed to my copending applications, Serial Nos. 563,013, 563,014 and 563,016, all filed November 11, 1944.

In view of the above. it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above alloys without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A corrosion-resisting thermostatic metal of an alloy having essentially the following composition:

Per cent Manganese 0.4

Carbon 0.05

Chromium 16-20 Iron Balance and an alloy having essentially the following composition:

Per cent Copper 97 Silicon 3 composed of'an alloy having essentially the following composition:

Per cent Manganese 0.4 Carbon 0.05 Chromium 16-20 Iron Balance and an alloy having essentially the following composition:

Per cent Copper 96-98 Silicon 2-4 the surfaces of said alloys being fused together at the junction.

4. A corrosion-resisting thermostatic metal composed of an alloy having essentially the following composition:

Per cent Manganese 0.2-0.6 Carbon 0.01-0.2 Chromium 12-20 Iron Balance and an alloy having essentially the following com- Per cent position: Manganese 0.4 Per cent Carbon 0.05 Copper 9 Chromium 16-20 5 Silicon 3 Imn Balance the surfaces of said alloys being fused together Copper-silicon alloy N0. 1 at the junction- Per cent 5. A corrosion-resisting thermostatic metal Copper 96 98 composed of an alloy having essentially the fol- Sflicon lowing composition:

. Per cent Copper-silicon alloy N0. 2 Manganese 0.2-0.6 Per cent Carbon 0.0l-0.2 Copper 97 Chromium 12-20 Silicon 3 7 Iron Balance 5 I and an alloy having essentially the following the junction.

. PAUL G. CHACE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Matthews Nov. 29, 1927 Scott Oct. 10, 1933 Matthews Feb. 20, 1934 Wohrman Feb. 19,1935 Bassett Mar. 30, 1937 OTHER REFERENCES Pp. 10001002 of The Making, Shaping, and Treating of Steel, 5th ed., 1940, pub. by Camegie- Illinois steel Corp., Pittsburgh, Pa.

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