US1464312A - Electrical-resistance element - Google Patents

Description

Patented hug, W, lddt H'NK A. IEAEIRENWALD, =E' CLEVELAND, OHM).

' ELECTRICAL-RESISTANCE ELEMENT.

Ea Drawing.

o all whom it may concern."

Be it known that I, FRANK A. Ferment?- want, a, citizen of the United States, reading at Cleveland, in the county of Cuyahoga t and State of Ohio, have invented a certain new and useful Improvement in Electricallltesistance Elements, of which the following is a full, clear, and exact description.

This application relates to electrical rem sistances and has for its especial object the provision of a new alloy for the same which shall possess a high and uniform coeflicient of resistance coupled with a high degree of resistivity to corrosion occasioned either b the high temperatures or'the chemical. e

fects produced by the electric current. Another object of the invention is the provision of an alloy which shall be readily fabricated into the necessary physical form, and which can be cheaply produced from materials of low intrinsic value; while further objects and advantages of the invention will become apparent as the description proceeds.

The basis of my improved electrical resistance alloy is a ferrous metal alloyed with not more than about twenty-five per cent of chromium and also with one or more metals from the titanium group of the periodic table of elements arranged according to Mendeleef, the last named metal or metals being present to an amount at least about one per cent and generally not more than five per cent of the whole. Carbon and silicon are preferably reduced to the lowest possible limits, particularly carbon, owing to its hardening and embrittling efl'ect and to the critical temperature conditions which accompany its use. For a ductile and malleable alloy, such as can be drawn into wire with ease and wound on forms readily the amount of carbon should constitute not over about 0.30% of the whole and it is better to lreep it below 0.10%, butfor casting use it can run higher, even to one or two per cent.

The alloy can be made in any one of a great number of ways, provided that care is exercised to keep the carbon content suficiently low. Thus ferrochrome of low carbon content can be diluted with low-carbon iron and the additional ingredients added in an electric furnace, or the chromium conltpplieation filed September 3t), 1921.

that zirconium possesses.

denial Etc. 5M/l39.

tent can be added thermochemically to a bath of molten iron in any kind of furnace, the additional ingredients being added either simultaneously or subsequently as convenient.

The additional ingredient which I prefer to use from the titanium group is titanium itself owing to the fact that it produces homogeneous ductile solid solution alloys with the other substances and to the fact that a given amount by weight will have twice the edect upon the specific electric resistance Both titanium and zirconium when alloyed with iron group metals have the property of producing when heated an impervious adherent refractory oxide coating which protects the metal beneath, and offers no tendency to combine with the oxides of iron or chromium to form a fusible slag. It is for this reason that l prefer to avoid the presence of silicon since this substance on heating forms an oxide which tends to combine with the oxides of chromium, iron, titanium, etc, with the formation of a comparatively fusible slag.

In case it is desired to increase the specific electric resistance yet further, it is preferable to do so by the addition of manganese, which may constitute up to about ten per cent of the whole. Its oxide is not so refractory as those of the other ingredients but has no objectionable action inside these limits.

By keeping the chromium content to the low limit mentioned the intrinsic value of the alloy is reduced, its ductility is increased, and its manufacture facilitated owing to the greater ease of keeping the carbon within bounds. The addition of a comparatively small quantity of titanium or zirconium has the same efiect in shielding from oxidation as a much greater quantity of chromium and without increasing the hardness or producing unstable surface conditions such as would be the case if other protective substances were employed.

While it do not restrict myself within the limits of the precedin description or of the following claims l will instance as a successful specimen formula the following: Tron, 78.9; chromium, l8; titanium, 2.5;,

Elm

manganese, .5; carbon, .10, it being understood that zirconium can be substituted for i the titanium if desired.

Having thus described my invention, what I claim is:

1. An electrical resistance element made of an alloy of iron with between ten and twenty-five per cent of chromium and from one to five per cent of one or more metals of the titanium group in the periodic table whose atomic weight is less than 100.

2. An electrical resistance element made of an alloy containing between ten and twenty-five per cent of chromlum, one to five per cent of a metal or metals in the titanium group of the Eeriodictable whose atomic weight is less t quantity of manganese.

3. An electrical resistance made of an al- 10y as specified in claim 1 hereof wherein the carbon content is less than 0.10%.

4. An electrical resistancev made of an alloy as specified in claim 2 hereof wherein the carbon content is less than 0.10%.

In testimony whereof, I hereunto aflix my signature.

FRANK A. FAHRENWALD.

an 100, and a small