US2455632A - Silicon electrical steel - Google Patents

Description

Patented 7,

inivinm. 'wil isifis, Cleveland;

a -The American Steel andwin y; Jersewaperpetuation of New Nd-matin ripplicatid p Serial ria tasse l x 'il ii's invehtiiin relates to sil lie r rimbrtwe'd elettri'c'a-lsz, properties 1 and, Tparticularly, F imetali ogi aphici sandman ilpon icon steels having intemal neeessanyr io stich s'teels having lowlicore lossvaliieswhich are tricaluperrormancea'is:ipredlbated; wll a-ebuit in krimwriiigiflrilna i rblriisithe tfbfm of lldn in mbh l ricarbcn iswneaiiily 'isblubleiitoWorm *aiisttnitai in arbon present in"electriwhich dissolved condition, the carhunii tswts substantiitlly greater than avaiiiame'ao tneihxygenircr remomla fitmn dt if'elfy eats h e1'C- 2.ft7d'tiliitg ld0Wi1 ithvMttiae-i trainstcnnanmnpciat, t "r the carbon soi'ne. r fithat!icarbdn Which-Was msaowa sense in th steel-making whighervtenipertttwehmetormsl.iintolcamde' mwhe dii llcii'it to Merifllefitafter ther'omdizing ilfiiiiltimls ho.*Wr decarburi anon prevaih lahde isretair iedg 1. 'asfbeen worlred inte he .peem cusewea inatmummm, :whtin ear treating prac- ".-present .ih siliebnisteel's, tenas'wieweraheeems have heretofore iiperaltiliierlatir wliichtthe" been proposed; to giveeifect to this latter prinmspemesan thewmetai lre rermtt'ie ciple, but have, or the most part, until the advent [nevelmnnentbrmptinium eleetridal iii the-teaching drihr siar arpneati l invoived tac-iwliiie rads'ingtthertemberdtimetat whidh -thusiliedn such elaborate and lengthy t eatinents of the e 'sbel 'will de'veldb measteel as do -ren der Jthe,rpractice uneconomical, eawefiddt lofi thisg ittlt'efiemrw 'iwTthat-Wi't offering, little or no inducement over the dewhich, in the absence of aluminumfli woild 'be carbtiilzation of the metai iiiii ing the stee'lirialifig dissolved in ithelttbelhatii tune, iitaiys out "fifihge; i W awonsciiiticmuwwwttmimmrcmrmn m $2M- The mildly 'o xidizing atmosphere set forth in anic:roritcombmm cmmans-swa ms hove identified, co prising ltfromihe weltaisetal boir dxideigills; i.

' myitheiuse oimlnminunr tnisilicmr steeism crave 7 o tilde a'sythe bal 'cipally rriti't'e beensatileiiithereforewtdid'eveidp-"watt lbtt v'a'lfles at room temperature, has proved highly satis-ll:10 biteififl wattmbaandimdetiilniiihe saiheilm ef factory in abstracting carbon from throughout time, and at the same temperatuiidius flisele'sed the mass of silicon steel subjected thereto, at elein my prior application, or have achieved subvated temperatures. The temperatures selected stantially the same watt loss values, as therein for this treatment have not, necessarily, been set forth, in a fraction of the time at the same rties, by heattreaiti'iient .zsomevgainm'aii on atithesertemperolttire ceasefir as he'refwhich is eifec-1 Mrhi .thwsteel bfiilowel siliconaconteiitl- As W11 Senti'ali lmetaiiampaic those provident of the greatest rate of carbon 45 temperatures, or at lower temperaures for the removal, since other factors, such as grain'size same length of time.

upon recrystallization of the metal, and *strain Steels made in accordance herewith, will have removal, have to be considered for the obtention, an initial carbon content in the order of 0.05%, of optimum electrical properties. The high and a silicon content which may range from 1% temperatures necessary to satisfy these latter 50 to 5%,but with the preferred values falling within conditions, are accompanied by the risks of silicon the range 2.50% to 3.50% silicon, and with an impoverishment, and a less efiective response in aluminum content within the range of 0.10% to the removal of carbon. It is obvious that the 1.0%, with the preferred amounts being in the exposure oi such steel, even to the mildly oxidizorder of from 0.15% minimum to 0.60% maxi ing conditions here contemplated, ior thetime M mum.

'= around 0.010%. are. admissible.

The steel of such analysis is worked into sheet and strip form by the usual hot mill methods, or hot and cold mill methods, to a gauge usually in the order of .014". The final gauge is not critical.

The sheets and strip are then normalized for strain removal Land recrystallization in -a continuousfum'ace containing an atmosphere of 002' of from 8 to 15%, water vapor of from 1 to 3.5% (or suificient to saturate the total atmosphereat temperatures from 50 F. to 85 F), and the balance, by difference, principally of nitrogen, with a usual total impurity content intheheighborhood of 3%, mainly of carbon monoxide, hy- 1 drogen, and methane. This atmosphere corresponds to that disclosed in my prior application referred to above, and is efiective at temperature to provide mildly oxidizing conditions in the furnace. a r I I have discovered that when silicon electrical steels arealuminized to such an extent as to contain from -.10% to -1,..00%'= aluminum; the desired extent of'recrystalliaation and grain growth may beobtained at temperatures of from 1500 F. to '1750fwF.,the time -.factor varying inversely with the temperature: Forithegreatest time/temperature: economy,. I have found that a temperature in .the neighborhood of.1750 F. will develop electrical properties of watt loss ranging. from'0.60 -watt/lb.-.for.a timein' the furnace of 1 minutes,

down 'to' lessthan 0.50 watt/lb. for a time in the furnace of-6 minutesc In accordance with the method. of the present. invention, a steel containing 3.51 siliconaandabdut 0.30% aluminum, having a watt eloss .valueas low. as 0.450 watt/1b., I has beenlma'de by heating in the neighborhood of 1750 F. .for 6 minutesin the atmosphere here prescribed.

- It .will be appreciated. that these exceptional electrical properties, are stabilized by. annealing, afterv theheat treatment above described, at a .temperaturemuallyaround 1425. F. for a few hours.- -The" stabilizing anneal is susceptible of considerable variation as-to time and temperature, having been successfully applied at temperatures of from 1300 F. up to1600 F., and for periodslof; time ranging between one-half to six "hours." This. stabilization anneal isaccompanied by. a further lowering of the watt loss values, and

:has yielded a' product having .9. watt loss rating of substantially .40-.watt/lb.- All of the values herein cited are for aninduction'of 10,000 gausses at 60 cycles.

Itfwill be. understood that the steels contemplated for treatment-hereby. may, in addition to; the silicon, aluminum, and carbon contentsprescribed, contain usual amounts of other elements common in steels ofv the type, such as, manganese up to 0.40%, and phosphorus andisulphur each small amountsof other elements.

Similarly, the sheets and strip may be hot worked or cold worked to gauge, or both, the

usual practice being to roll hot strip continuously to around .062" gauge, and, then, cold reduce it continuously in strip form to gauges ranging between .014" and .022". The final thickness will determinethe rapidity of response ofthe material to heat treatmenti and prescribe the manner of heat treatment as between continuous and batch methods. Beyond this, however, the ultivmate gauge thickness, and the form of the heat treatment, are not critical.

This application. is a continuation of my copending application bearing Serial No. 460,001,

-now-abandoned, which was filed September 28,

1942, and which was a continuation-in-part of "the application which matured into Patent No.

2,304,518, and is also a continuation of my patent application Serial No. 584,257, now abandoned, filed March 22, 1945.

. While I have shown and described certain"specific embodiments of the; presenteinventiomait willibe readily understood by those. skilled in the artthat I do not wish to be limited exactly thereto,-since various'modifications maybe made;with- ,out departingfrom the scope .of the. inventio as defined in the appended claim. .i t;

. Iclaimt. J .w

A method of making aluminized silicon;- steel electrical strip. or sheet; said method; comprising the steps of producing an aluminized: silicon steel .with a composition suitable for,said,product and containing from 1% to 5% ,si1icon,i fr,om 1 0% .to 1.00% aluminum and substantially,1 more than about .02%'. carbon; working, said steel ,to; strip or Y sheet, and continuously annealing s a .icl, strip,;or sheet in a decarburizingatmosphere at temperatures of from 1500 F. to 1750,F. to reduce the caricon to less than .02 said atmosphere being oxidizing, to adegree regulated to cause the formation of a thin, :tightly adherent oxide film oln s aid strip orsheet without the production of a heavy,

'Name a at; Williams 'Dec. ,1942 QTI-lER. REFERENCES Number Alloys of Iron and SifieonTfGriener etaah,

pages 385 and 386, McGraw-Hill Beckv 00., N. Y.,