|Title of Invention||
AN AMORPHOUS ALLOY STEEL COMPOSITION
|Abstract||This invention relates to an amorphous alloy steel composition for manufacturing amorphous alloy steel with high induction and low electromaganetic loss,said composition comprising a mixture of iron,born and silicon with additives of phosphorous and nickel in the following atomic percentages: a) 7.5 to 11.5 of boron; b) 7.0 to 10.5 of silicon; c)1.0 to 4.0 of phosphorous;d) 0 to 1.5 of nickel ;and e) balance amount of iron.|
|Full Text||The invention relates to an amorphous alloy steel composition for manufacturing an amorphous alloy steel with high induction and low electromagnetic loss. The amorphous alloy according to the invention is excellent for making magnetic core material of electrical appliances such as transformers, motors, chokes etc. The amorphous alloy steel according to the invention can be used for making magnetic core material in the form of ribbons and wound to form magnetic core. These wound magnetic cores after annealing under magnetic field are excellent magnetic cores for use in the above mentioned applications. They have relatively low loss and high induction at low operating frequencies such as 50 Hz.
Use of wound cores from tape made of amorphous alloy steel instead of the conventional cold rolled grain oriented (CRGO) silicon steel, considerably reduces the magnetic loss in the core to about 75%. The no-load loss or core loss in distribution transformers are significant. It is estimated that if all the existing cores of CRGO silicon steel in distribution transformers presently used in India are replaced with cores made of amorphous alloy steel, the generation capacity will be enhanced by 370 Mega Watts. Though such a replacement is not practical new use of such transformers in new installation will result m substantial energy saving.
Various types of amorphous alloy steels are known commercially and some of the best known types are 2605-S2 of /U.S.A.. Vitrovac 7505 of Germany, 2HSB and 7411 of Russia. For manufacturing wound cores, the amorphous alloy steel is melted, homogenised at an elevated temperature and then cast into a thin ribbon at a lower temperature than the homogenising temperature. This ribbon is wound to form the magnetic core. They are annealed at an elevated temperature of about 45°C. The parameters which are of important in the manufacture of amorphous alloy steel are critical thickness of ribbon, solidification temperature of alloy (Tc), homogenization temperature and fluidity of the melt at a particular temperature.
The critical thickness of ribbon is the maximum thickness which can be obtained from the melt during casting of ribbon. It is desirable to have a higher critical thickness of ribbon, lower homogenization temperature and lower casting temperature for the amorphous alloy steel.
The amorphous alloy steel compositions known in the art contain substantial amount of carbon. This causes excessive diffusing mobility and formation of chemically strong carbides with high melting temperature. This will result in segregating heterogeneity during production of ribbon and inadequate reproducibility of physical and magnetic properties.
Accordingly, the present invention provides a method of manufacturing a novel amorphous alloy steel comprising melting a mixture of iron, boron and silicon with additives of phosphorous and nickel in the following atomic percentages: a) 7.5 to 11.5 of boron; b) 7.0 to 10.5 of sihcon; c) 1.0 to 4.0 of phosphorous; d) 0 to 1.5 of nickel; and e) balance amount of iron; under known alloy making conditions fo obtain the amorphous alloy steel with high induction and low electromagnetic loss.
The amorphous alloy steel made according to the invention has a composition containing 7.5 to 11.5 atomic percentage of boron; 7.0 to 10.5 atomic percentage of silicon; 1.0 to 4.0 atomic percentage of Phosphorous; 0 to 1.5 atomic percentage of nickel and balance amount of iron. The solidification temperature of the amorphous alloy steel having the abovementioned composition was found to be equal to or more than 515"C. It is possible to obtain a maximum ribbon thickness (which is also known as critical thickness) of 35 to 40 micrometer by using this amorphous alloy steel composition.
The honogenizing tenperature of 1400°C is adequate and the easting tenperature is 1300°C. The fluidity of the alloy made according to the invention ia better than the conventional alloys, resulting in better ribbon production due to less nunber of brakes due to freezing of nelt in the nozzle slit during casting. The quantity proportion specified in respect of -each eieBents in the anorphous alloy steel made according to the invention assure an optinal conbination of desired ribbon production parameters and magnetic properties. The ribbon produced from the alloy made according to the invention had a magnetic loss of not iiore than 0.20 Hatts/kg at 50 Hz and 1.45 Tesla induction.
It is preferable to keep the sum total of atomic percentage of phosphorous, silicon and boron in the range of 19.5 to 22 in the melt and the sun total of atomic percentages of boron and phosphorous in the range of 11.0 to 13.5.
A prefered amorphous alloy steel composition comprises 2.6 to 4 atomic percent of phosphorous, 7.5 to 9.0 atomic percent of boron, 8.0 to 10.5 atomic percent of silicon, 0 to 0.02 atomic percent of nickel and the balance iron.
Various samples of the alloy composition in the specified ranges were prepared. Ribbon was cast using these alloy steels. The results of these experimental samples are given below substantiating the improved results.
The experinental samples of alloys were nade in the forn of 10 nn wide ribbon by tenpering on a 360mm copper drun, at 30 neters per second rotating speed. The chenical oonposition of the samples are given in Table 1. The starting solidification temperature of amorphous alloys were determined by the method of differential thermal analysis, at the heating rate of 30° per minute. The ribbon thickness were varied. to find out its critical dimensions, by changing the nozzle slit. The homogenization and casting temperatures of alloys of different grades are shown in table 2. Their fluidity were determined experimentally, while streamlining the ribbon production process. Viscosity was determined by the torsinal vibrations method. As the phosphorous content was increased from 0 to 3.7 atomic percent, viscosity at 1400°C decreased from 1.5xl0"6 m2 per second at a phophorous content of 0.5 atomic percent to 0.5x10 6 B^ per second at a phosphorous content of 3.7 atomic percent.
The ribbon thus made was used for fabricating toroidal cores having 16 to 20 gms in weight and 23 to 25 mm of average diameter. The cores were heat trated at 410 to 420°C during 30 ninutes. The samples made of ribbons 10 and 11 wore annealed in nitrogen. The sample 10 was additionally annealed in normal air. For the sake of comparison, cores were fabricated from commercial alloys 2605-S2 of USA and 2NSR and 7411 of Russia and Vitrovao 7505 of Germany-
The magnetic properties of the cores at direct current were deternined by particular and ultiamte hystoresic cycle (quasistatic Magnetization code) in 0.1 to 30 oersted fields as shown in table 3.
The dynanic characteristics (reversal magnetization loss, W/kg) were deternined in "H-sine" node, at 1 to 1,55 Tesla induction and 50 Hz frequency as shown in table 4.
Table 1 :
Impact of the chenical compoaition upon the critical thickness of the ribbon.
The solidifying temperature (Tcr) and critical thickness obtained under sinilar conditions for the alloys 2NSR of Rusia and 2805-S2 of USA are given below.
2HSR : Tcr = 540°C and critical thickness 30 UM. 2605-32 : Tcr = 540°C and critical thickness 25 an.
Table 2 :
Table 3 :
Alloys magnetic properties (quasi-static) of chemical conpositions as per Table I.
Studies conducted under sinilar conditions on 2NSR alloy of Russia and 2605-S2 alloy of USA gave the following results :
2HSR Induction 15.0 Kiloguass; Coercive force 0.050
to 0.08 oersted and Squareness ratio 0.59.
2605-S2 : Induction 15.6 Kiloguass; Coercive force 0,050
oersted and Squareness ratio 0.53.
* Alloy 10 was heat treated in the longitudinal field. BM is the nagnetic flux density and T is unit Teala.
The cost of the starting material for the alloy according to the invention is lower than that for commercially available alloys 2605-S2 and 2NSR.
The parameters of the amorphous alloy steel such as critical thickness of ribbon, alloys solidification temperature, homogenization temperature, fluidity, are superior to those of the commercial alloy steel known. The loss in cores made of the proposed alloy steel will not exceed 0.25 W/kg at induction values of Bm = l. 55Tesla. In the case of alloy steels known in the art the working induction maximum would not exceed 1.4Tesla.
The amorphous alloy steel made according to this invention can be effectively used to Bake magnetic cores with excellent characteristics which can be used in electrical appliances such as transformers, motors etc.
It will be obvious to persons skilled in the art that numerous variations and modifications are possible without departing from the basic inventive concept. All such modifications and variations are to be considered within the scope of this invention.
1. An amorphous alloy steel composition for manufacturing amorphous alloy
steel with high induction and low electromagnetic loss, said composition
comprising a mixture of iron, boron and silicon with additives of phosphorous
and nickel in the following atomic percentages:
a) 7.5 to 11.5 of boron;
b) 7.0 to 10.5 of silicon;
c) 1.0 to 4.0 of phosphorous;
d) 0 to 1.5 of nickel; and
e) balance amount of iron.
2. The composition as claimed in claim 1, wherein the sum total of the atomic percentage of phosphorous, silicon and boron is kept from 19.5 to 22 and the sum total ofatomic percentage of the boron and phosphorous is kept from ll.Oto 13.5.
3. The composition as claimed in claim 1 or 2, wherein the melt contains 0.4 to 0.6 atomic percentage of nickel and 1.5 and 2.5 atomic percentage of phosphorous.
4. The composition as claimed in any one of the preceding claims, wherein the
melt contains 2.6 to 4.0 atomic percentage of phosphorous, 7.5 to 9.0 atomic
percentage of boron, 8.0 to 10.5 atomic percentage of silicon and not more than 0.02
atomic percentage of nickel,
|Indian Patent Application Number||555/MAS/1999|
|PG Journal Number||13/2008|
|Date of Filing||13-May-1999|
|Name of Patentee||TOTEM CO LTD|
|Applicant Address||3RD MYTISCHINSKAYA STREET, 16, BLOCK 60,6TH FLOOR, POB 62, MOSCOW 129626,|
|PCT International Classification Number||H01F 41/02|
|PCT International Application Number||N/A|
|PCT International Filing date|