US2482898A - Corrosion-resisting composite metal - Google Patents

Description

Sept. 27, 1949. P. e. CHACE 2,482,898

CORROSION-RESISTING COMPOSITE METAL Original Filed June 23, 1941 Patented Sept. 27, 1949 Paul G. chm, Attleboro Falls, Masa, assumito Metals and Controls Corporation, Attleboro, Mass, a corporation of Massachusetts Original application June 23, 1941, Serial No.

399,398, now Patent No. 2,368,178, dated January 2, 1945.

Divided and this application November, 11, 1944, Serial No. 563,014

7 Claims. (Cl. 29-1955) This invention relates to composite metal elements and particularly to bimetallic elements which are corrosion-resisting.

This application is a division of my co-pendmg 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 thermost-ating metal which is corrosion-resisting, which has an improved bond, and which has a long life when operating in corrosion-promoting atmospheres 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 the. application of which will be indicated in the following claims.

In the accompanying drawing in which is illustrated 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 subjectto 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 thermostatic 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 materiallyand does not assure satisfactory life for the thermostatic element. Furthermore, such plating is not entirely satisfactory since an electrovoltaic 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 ametal alloy having a higher coefllcient of expansion. The metal used for the high coeflicient of expansion side has been one of the brasses. The mechanical properties of these brasses have presented manufacturing diffiulties, 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 coldwork the metal after 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 brasschrome iron bimetals must be kept small because of the aforementioned difficulties 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 difficult 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 manufacture 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 gether over their entire areas by a direct bond,

One of the layers, in the present invention, comprises a corrosion-resisting metal having a low coefficient of expansion. The other layer comprises a second corrosion-resisting metal having a relatively high coeillcient of expansion.

For the metal having a low coefllcient of expansion a high chromium content stainless iron is employed. The composition of this alloy may be as follows:

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 composition of this alloy may be as follows:

Per cent Copper 96-99 Silicon 0.5-4 Manganese 0-1 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-pencling application, Serial No. 399,398, filed June 23, 1941, Patent 2,366,178, referencev 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 i 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 sufiiciently 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 dificult to manufacture, and in general are not satisfactory.

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

Chrome-iron Alloy N0. 1

Per cent Manganese 0.2-0.6 Carbon 0.01-0.2 Chromium 12-20 Silicon .2-1.5 Copper .5-1.5 Iron Remainder Chrome-iron Alloy No. 2

Per cent Manganese 0.4 Carbon 0.05 Chromium 16 Silicon 1 Copper 1 Iron Balance Attention is directed to my copending applications, Serial Nos. 563,013, 563,015 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 alimiting.' sense.

I claim:

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

Percent Manganese l 0.2-0.6 Carbon 1 0.01-02 Chromium 12-20 Silicon .2-1.5 Copper 5-1.5 Iron Remainder 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.

2. A corrosion-resisting thermostatic metal composed of an iron alloy containing: manganese approximately 02-06%, carbon approximately 0.01-0.2%, chromium approximately 12-20%, silicon approximately 0.2-1.5% copper approximately 0.1-1.5%, and the balance iron; and a copper alloy containing: silicon approximately 0.54%, and the balance copper; the surfaces of said alloys being fused together at the junction.

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

Per cent Manganese 0.4 Carbon 0.05 Chromium 16 Silicon 1 Copper 1 Iron Remainder and an alloy having essentially the following composition:

Percent Copper 96-98 Silicon 2-4 the surfaces oi 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 0.4 Carbon 0.05 Chromium 12-16 Silicon 1 Copper 1 Iron Remainder and an alloy having essentially the following composition:

Per cent Copp r 98-98 Silicon 2-4 the surfaces of said alloys being fused together at the Junction.

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

the surfaces of said alloys being fused together at the junction.

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

Per cent Manganese 0:4 Carbon 0.05 Chromium 16 Silicon 1 Copper 1 Iron Remainder 6 and an alloy having essentially the following composition:

- Per cent Copper 9'? Silicon 3 the surfaces of said alloys being fused together at the junction.

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

Per cent Manganese 0.4 Carbon 0.05 Chromium 12-16 Silicon 1 Copper r 1 Iron Remainder and an alloy having essentially the following composition:

Per cent Copper 97 Silicon. 3

the surfaces of said alloys being fused together at the junction.

PAUL G. CHACE.

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

UNITED STATES PATENTS Number Name Date 1,650,951 Matthews Nov. 29, 1927 1,948,121 Matthews Feb. 20, 1934 1,991,438 Wohrman Feb. 19, 1935 2,075,014 Bassett Mar. 30, 1937 2,087,431 Felld July 20, 1937 OTHER REFERENCES Pages 1000-1002 of The Making, Shaping, and Treating of Steel, 5th ed., 1940, pub. by Carnegie- Ill. Steel Corp., Pittsburgh, Pa.

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