US2359781A - Electrical resistance alloy - Google Patents

Description

Patented Oct. 10, 1944 RESISTANCE ALLOY announcer.

Theobald H. Noll, Washington, I). C.

No Drawing. Application December 21, 1942,

Serial No. 469,673

2 Claims. ((175-124) This invention relates to alloys from which a durable electrical resistance having the desired properties can be made.

The main object of the invention is to reduce the amount of expensive and less readily obtainable metals contained in the alloy and still vpreserve qualities desired in electrical resistance devices made from such alloys.

Other and ancillary objects of the invention will appear hereinafter.

An alloy largely of nickel andchromium has been found to produce an electrical resistance having many valuable properties. However, nickel and chromium are relatively high-priced and are not readily obtainable especially under presentconditions. I have discovered that an alloy providing thequalities desirable in a resistor may be formed it the amounts of nickel and chromium are greatly reduced and the greater part of the alloy is formed of iron which is relatively low-priced and available. However, iron has a tendency to introduce undesirable properties into the alloy, for instance lack of resistance to corrosion and reduction of specific electrical resistance. These undesirable conditions occasioned by the use of the large proportion of iron may be substantially, if not wholly, removed by the addition of aluminum which increases the specific electrical resistance and also improves the resistance to corrosion. The addition of the aluminum, however, tends to promote undesirable crystal or grain-growth in the alloy. When, however, the aluminum is used in a small percentage.

in the alloy, not exceeding 5%, this undesirable crystal or grain growth does not take place to any materially deleterious extent.

I have found that an alloy having the desirable characteristics as referred to and also other desirable properties may be made up of (the percentages being by weight)- Per cent Nickel 4 Chromium 14,3 Aluminum 2.6 And the balance iron.

The whole is formed-by fusing the iron, nickel ing the same. Into this fused bath is introduced an ingot or lump of aluminum which fuses therein and the whole is thoroughly mixed. A small amount of silicon may be added to the fused bath as a reducing agent as is well understood in such operations. A slag forms on top of the bath and the fused metal is poured oil into aningot, leaving the slag behind, the poured metal being substantially a pure alloy of nickel, aluminum, chromium and iron as above specified, although there may be inconsequential traces of other metals or materials which do not materially affect the desired properties of the alloy. This alloy may then i be drawn into a wire or shapedin other desired and chromium in a crucible and thoroughly mixforms. This alloy has the highly desirable characteristic's for an electric resistance, namely:

High specific resistance,

Low temperature co-efilcient of resistance, Ductility,

High melting point,

It may operate at high temperatures,

Has a low co-emcient of thermal expansion, Is corrosion resistant, and Has no material crystal or grain-growth.

This alloy has the desirable capability of being drawn to wire of extremely small diameter.

It is to be-understood, however, that the proportions of the ingredients, namely, nickel, a1u- 14.3% chromium and the remainder iron, the

proportions being by weight.

2. An electrical resistance alloy consisting substantially entirely of not less than 1.8% nor more than 7.2% of nickel, not less than 1.5% nor more than 5% of aluminum, not less than 12% nor more than 16% of chromium and the remainder of iron, the proportions being by weight.

THEOBALDH. NOLL.