US1833723A - Alloy - Google Patents

Description

Patented Nov. 24, 1931 UNITED STATES PATENT OFFICE WILLIAM E. BUDER,

OF SCHENTECTADY, NEW YORK, ASSIG-NOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ALLOY No Drawing. Application filed June 7,

My invention relates to alloys and has for its object the provision of an alloy which is heat resisting or capable of withstanding .high temperatures in 'air without excessive oxidation.

More specifically my invention relates to electric resistance heating alloys and to alloys which may be cast to form various articles required to withstand high temperatures.

In carrying out my invention 1 provide an alloy having an iron, base and containing from 15 to 35f/ of chromium and from 5 to 12% of aluminum. Preferably I use 25% of chromium, and of aluminum,- the re- 15 mainder consisting substantially of iron.

For the purpose of improving the physi cal quality of the alloy, about 1% of a suit-1 able grain refining and purifying element may be added in making the alloy, such as titanium, zirconium, molybdenum, uranium,

all or a large portion of it may go off withvanadium or the like, although this is not absolutely necessary. The alloy mayand probably Will' not contain the percentage of grain refining element added to the mixture, since the slag.

This alloy may be forged or drawn into wire and has the other characteristics essential to a satisfactory resistance heating conductor such as durability or the property of withstanding high temperatureswithout ex ces'sive oxidation, sufficient resistivity to generate the required amount of heat when a current is passed through it, and a zero temperw caturecoefficient of resistance throughout its "ohms per mil foot, and the durability also increases, while the ductility becomes less. The temperature coeflicient of resistance is 1923. Serial No. 644,058.

practically zero throughout the ranges of the various elements given, and the alloy shows very little oxidation when run for long periods at temperatures above 1000 0.] The composition ofthe alloy actually used would therefore 'be determined by the relativeimportance of cost of the materials, resistivity, durability, and mechanical quality.

The metal forming the base of the alloy may be ordinary low carbon steel or even commercial iron. A steel containing .02% or less of carbon, .04% "or less of sulphur, or less of phosphorus and 0.15% or less of. silicon is satisfactory for my purpose.

In making the alloy it is preferable to use an electric furnace, since this furnace lends itself more readily to the cpntrolling of an alloy. The furnaceshould preferably have a basic lining since i an acid lining were used a certain amount of silicon in the lining would be reduced by'the aluminum and enter into the alloy. Even a small-percentage of silicon in the alloy is objectionable. When the aluminum is not added in the furnace but is added in the ladle, the basic lining becomes less important.

The iron and chromium are melted in the furnace and then tapped on to the aluminum, which has been preheated to a molten condition in the ladle. Care should be taken to have the iron and chromium.mi-xture thor-' oughly deoxidized before adding' it to the aluminum. It is preferable to have the carbon as low as possible in case thematerial used runs a little higher than approximately .01% in carbon, the carbon should be reduced in the furnace before making the alloy. This appliesalso to the elements phosphorus and sulphur.. None of the furnace slag should be allowed to come into contact with the alloy after the aluminum has been added. The molten aluminum and also the alloy after. the addition of. the aluminum should be kept covered with a special-slag of cryolite or a cryolite lime mixture to protect the-aluminum from oxidation. Cryolite is used because of its solubility for aluminum oxide. Care should be takento have the metal in the furnace just hot enough to pour cleanly from the ladle but not superheated. The cooler it is when cast the better the grain obtained. When castingthe alloy eve precaution should be taken to prevent oxi ation. This ay be done by filling the molds beforehand ith a non-oxidizing 'gassuch as nitrogen ',-:or carbon dioxide,- or bygdusting the molds lightly bug thoroughly ith cryolite to dissolve the oxide film forme between the ladle and the mold. This revents the formation of cold-shutsand-su sequent c'racks'dueito' them. The cryolite method'is' preferredto the gas method.

While'I have described a specific embodiment of my invention inaccordance with the provisions ofth patent statutes, it' should be gunderstood thatI do'not'limit my invention thereto, since various modificaions thereof will suggest themselves. to those skilled in the art without departing from the -,spirit of my invention, the scope of which is set forth in the annexed claims. What I claim asg-newvandidesire ,to secure by Letters Patent ojfthe United States'is 1. A heat resisting alloy containing ap- 1 proximately .of,chromium,,and 10% of aluminum, the'rem'ainder consisting of ironand not more than 1%ofa gram refining element. 7

2. A heat resisting alloy having an iron, aozbase and containing approximately 25% of chromium and 1 Q% 0f aluminum, there-2 mainder consisting of an appreciable amount but not more-than 1%,of a grain refining.

element.

= '35; 3. .A heat resisting alloy having an iron base and containing approximately 25% of {chromium and 10% of aluminum, the remainder consisting of-an appreciable amount but not' ;more than 1%;0fi-titanium; -v 1 4o 4.-A resistor containing about'25% chromium, about 10% aluminum and about 65% iron, said alloy having a substantially zero temperature'coeificient of resistance throughout its normal operating range.

5 3 In witness ,Whereof, I have hereunto set my hand this 6th day of June, 1923. p

' WILLIAM'E; RUDER.

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