US1460048A - Electrical heating element - Google Patents

Description

June 26, 1923.

A I 1,460,,8 'OFFIC PERCY A. E. ARMSTRONG, OF LOUDONVILLE, AND RALBH 1". DE VRIES, OF NEWTON- VILLE, NEW YORK; SAID DE VRIES ASSIGNOB TO SAID ARMSTRONG.

ELECTRICAL HEATING ELEMENT.

We Drawing.

To all whom it may concern Be it known that we, PERCY A. E. ARM- STRONG, a subject of the King of Great Britain, and a resident of Loudonville, county of Albany and State of New York, and RALPH P. DE VRIEs, a citizen of the United States, and a resident of Newtonville, county of A1 bany, and State of New York, have invented certain new and useful Improvements in Electrical Heating Elements, of which the following is a specification.

- Our invention relates to elements for electrical heating purposes, which may be either mechanically worked as by hot or cold rolling, wire drawing or the like, or may be in the form of cast grids or the like. Electrical heating elements in accordance with our invention are made of alloy steel containing iron, chromium, silicon, a high melting point metal or metals other than chromium of the sixth, group of Mendelefis table preferably tungsten, .and carbon; and may contain chromium from about to about silicon from about .5% to about 3.5% or 4% for mechanically worked material, and up to about 6% silicon for east material, tungsten from about 2% to about 5% for readily mechanically worked material and up to about 10% where the consequent red hardness is" not objectionable, carbon from about .05 to about 1%, and the principal part of the remainder is made up of the iron base. The material may contain more or less sulfur or other metalloids, but the proportion of metalloids other than silicon is preferably kept low. Manganese may also be present in the usual proportions encountered in steel making, say up to about 1%. Higher percentages are not-desirable, and the manganese may be dispensed with, if desired. Molybdenum or uranium may be substituted for the tungsten or part thereof if desired, with nearly if not'quite so good results as with the tungsten.

We have obtained very good results, for example, from electrical heating elements run at about 1700 to 1900 F., and made from alloy steel containing carbon about .20

to 30%, chromium about 17 to 20%, silicon about 2.40 to 3%, tungsten about 2.5 to 3%,

manganese about .20 to .40%, and the principal part of the remainder iron, one of several melts being ofv the following analysis: carbon about 25%, chromium about Application filed m 29,

1921. Serial No. 488,471.

18%, silicon about 3%, manganese about 7 40%, tungsten about 3%, and the principal part of the remainder iron.' This material when put into use as an electrical heatingv element, run up to about the temperatures referred to, shows a smooth whitish surface formation which may be referred to as a frosting or an excessively thin scale, and is subject to practically no progressive deterioration or scale formation in use, so that the body of the metal is not called upon to give up additional metal to form an oxide,'and the material stands up extremely well in use over long periods. To obtain this result with a whitish frosting or scale, we have found that at least 2% of silicon should be present and preferably about 2.4%. This whitish frosting appears to some extent with 3% of silicon as used in the foregoing example when as little as 2% of tungsten is used, and with 3% of tungsten as in the foregoing example the whitish frosting effect is obtained to substantially a maximum extent; It appears essential to produce the whitish scale or frosting, which is apparently non-porous and serves as a protection against deterioration of the metal when run at high temperatures, that a considerable body of silicon should be present together with the tungsten. For electrical resistance material as an electrical heating element, but while carbon above aboutv.4% is not recommended for heating elements, same may be higher up to about 1%, particularly for electrical resistance elements which are used at comparatively low temperatures. The proportions given herein are by weight.

The alloy of the present invention is resistant to rusting and to the action of acids and other corroding agents and may be made use of where these characteristics are of advantage as, for example, it is well adapted for such uses as heating of liquids by means of .bare electrical heating ele ments submerged inand brou ht into direct contact with the liquid to e heated.

The specific resistance of elements in accordance withrthis invention is comparatively hi h use of elements of relatively small crosssection. For example, elements containing,

carbon .1 to 4%, s1l1con 2.4 to 3.5%, tungstenu25 to 5%, manganese under 1%, and' the principal part of the remainder-except for chromium-iron, we'find that with chromium 17 to 20%, ,the material. has .a specific resistance of about 100 microhms per cubic -c. cs; with the same material except that the chromium" is from 20 'to25%,' the specific resistance is about 105 microhms per cubic 'c. 0.; and with 25 to of chromi um, the specific resistance" is'about 110'.

microhms per cubic c. c.

We claim: 1. An electrical heating element made of alloy steel containing 'carbon about .05v to 1%, chromium more than, 10% and less than 30%, silicon about 2 to 6%, a high melting point metal or metals other-than chromium of the sixth. group of Mendelefis table about .20 to about: 10%, and the principal part of the remainder iron.

2. An electrical heating element inade of alloy steel containing carbon about .05 to 1%, chromium more than 10% and less than 30%, siliconabout 2 to 6%,"tungsten. about .20 to 10%, and the principal part of the remainder iron. l L

'3. Amchanically worked electrical heating element made of alloj steel containing carbon about .05 to .4%, chromium about 17 to 25%, silicon about 2 to "3.5%, tungsten about .20to 5%,and the principal part of the remainder 'irbn. i

4. An electrical "heating element made' of so that -it is possible to make alloy steel containing carbon about .1 to

.-4%, chromium about 17 .to 25%, silicon alloysteel containing carbon about -.1 to" .4%, chromium about 18%,, siliconabout.

3%, tungsten about 3%, manganese under 1%, and the principal part of the remainder,;iron-.-

.7 electrical heating element made of alloy steel. containin :carbon, chromium, silicon, tungsten an 0 iron, with; v at least as much SillOOD. as tungsten and exhibiting a whitish frosting or scale of excessive thin;

ness when; subjected to electrical heating at about'l'ZOO to 1900 F.

8.;An electrical resistance element made of alloy steel containing carbon about .05 to 1%, chromium about 10.to 30%, tungsten about ,20'to. 1 0%, siliconlabout .5 to 6%,

and-"the principal part of the remainder 11011- 9, An electrical resistance element madeof alloy steel containing carbon about .05

to 1%,chromium "about 17 25%, silicon about .5 tojl3.'5%, tungsten about 2 t0 5%. manganese" under' 1%, and the principal part of the remainderv iron.

, In testimonythat'we claim the foregoing,

we have s'ignedourn'ames hereto.

PERCY A. ARMSTRONG, RALPHRDE VRIEs. a