CA1086194A

CA1086194A - Silicon steel and processing therefore

Info

Publication number: CA1086194A
Application number: CA280,688A
Authority: CA
Inventors: Clarence L. Miller, Jr.
Original assignee: Allegheny Ludlum Corp
Current assignee: Allegheny Ludlum Corp
Priority date: 1976-06-17
Filing date: 1977-06-16
Publication date: 1980-09-23
Also published as: PL114605B1; BE855834A; JPS52153825A; MX4371E; HU179103B; FR2355087A1; RO71136A; SE7707029L; CS218567B2; ZA773084B; ATA419877A; PL198882A1; BR7703865A; FR2355087B1; ES459890A1; YU151477A; AT363975B; DE2726013A1; AU2552377A; GB1565474A

Abstract

SILICON STEEL AND PROCESSING THEREFORE
ABSTRACT OF THE DISCLOSURE

A process for producing electromagnetic silicon steel having a cube-on-edge orientation and a permeability of at least 1870 (G/Oe) at 10 oersteds, The process includes the steps of: preparing a melt of silicon steel containing from 0.02 to 0.06% carbon, from 0.0006 to 0.0080% boron, up to 0.0100% nitrogen, no more than 0.008% aluminum and from 2.5 to 4.0%
silicon; casting said steel; hot rolling said steel; cold rolling said steel;
decarburizing said steel; applying a refractory oxide coating containing both boron and SiO2; and final texture annealing said steel.

Description

~86~4 1 The present invention relates to an improvement in the ~ ~.
manufacture of grain-oriented silicon steel.
United States Patent Nos. 3,873,381, 3,905,842, 3,905,843 and 3,957,546 describe processing for producing boron-inhibited grain oriented electromagnetic silic~n steel. Described therein are processes for producing steel of high magnetic quality from boron-bearing silicon steel melts. Through this invention, I now provide a process which improves upon those of f the cited patents~ Speaking broadly, I provide a process which improves llpon those of said patents by incorporating controlled amounts of both boron and SiO2 in the base coating, which is applied prior to the final texture anneal.
- It is accordingly an object of the present invention to provide an improvement in the manufacture of grain-oriented :. silicon steels.
. In accordance with the present invention a melt of silicon steel containing from 0.02 to 0.06~ carbon, from 0.0006 :.
to 0.0080~ boron, up to 0.0100% nitrogen, no more than 0.008%
: aluminum and from 2.5 to 4.0% silicon is subjected to the con-.~ 20 ventional steps of casting, hot rolling, one or more cold ;` rollings, an intermediate normalize when two or more cold rollings are employed, decarburizing, application of a refractory oxide coating and final texture annealing; and to the improvement comprising the steps o~ coating the surface of the steel with a refractory oxide coating consisting essentially of:
~a) 100 parts, by weight, of at least one substance from the group consisting o~ oxides, hydroxides, carbonates ; . and boron compounds of magnesium, calcium~ aluminum and ! .
:~ . titanium;
. 30 (b) up to 100 parts, by weight, of at least one other -- 1 .
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1 substance from the group consisting of boron and compounds thereof, said coating containing at least 0.1%, by weight of boron;
(c) from 0.5 to A0 parts, by weiyht, of SiO2;
~d) up to 20 parts, by weight, of inhibiting substances or compounds thereof; and (e) up to 10 parts, by weight, of fluxing agents;
and final texture annealing said steel with said coating thereon.

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For purposes of definition, "one part" equals the total weight lO of (a~ hereinabove, divided by 100. -~
Specific processing as to the convention steps, is not critical and can be in accordance with that specified in any - number of publications including United States Patent No.

2,867,557 and the other patents cited hereinabove. Moreover, the term casting is intended to include continuous casting processes. A hot rolled band heat treatment is also includable :, , within the scope of the present invention. It is howeyer, preferred to cold roll the steel to a thickness no greater than 0.020 inch, without an intermediate anneal between cold rolling passes; from a hot rolled band having a thickness of from about 0.050 to about 0.120 inch. Melts consisting essen~ially of, by weight, 0.02 to 0.06% carbon, 0.015 to 0.15% ~anganese, 0 01 to ! 0-05% of material from the group consisting o sul~ur and ~elenium, 0.0006 to 0.0080~ boron, up ~o 0.0100% nitrogen, ~.5 to 4.0% silicon, up to 1.0% copper, no more than 0.008% aluminum, balance iron, have proven to be particularly adaptable to ~he subject invention. Boron levels are usually in excess of 0.0008%.

Steel produced in accordance with the present invention has a permeability of at least 1870 tG/Oe) at 10 oersteds. Preferably, ' 30 the steel has a permeability of at least 1900 (G/Oe) at 10 ~;

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1 oersteds and a core loss o~ no more than 0.700 watts per pound at 17 kilogauss. ~ ~ ;
The specific mode of applying the coating of the subject invention is not critical thereto. It is just as much within the scope of the subject invention to mix the coating with water and apply it as a slurry, as it is to apply it electrolytically. Like-wise, the constituents which make up the coating can be applied together or as individual layers. It is, however, preferred to ;~
have at laast 0.2%, by weight, of boron and/or at least 3 parts, by weight, of SiO2, in the coating. Boron levels usually do not exceed 15%. They are generally, however, below 5%. Silica levels ' are generally not in excess of 20 parts by weight. The additional inhibiting substances includable with the coating are usually ~ from the group consisting of sulfur, sulfur compounds, nitrogen Z~ compounds, selenium and selenium compounds. Typical sources of Z~ boron are boric acid, fused boric acid (B203), ammonium penta-' ~ -borate and sodium borate. Typical fluxing agents include lithium Zl oxide, sodium oxide and other oxides known to those skilled in the art. Those skllled in the art are, of course, aware o various ways of adding silica. Colloidal silica is, however, preferred.
Also includable as part of the subject invention is the steel in its primary recrystallized state with the coating of the .. i, .
! subject invention adhered thereto. The primary recrystalliæed steel has a thickness no greater than 0.020 inch and is, in accordance with the present invention, suitable for processing into grain oriented silicon steel having a permeability of at least 1870 ~G/Oe) at 10 oersteds. Primary recrystallization takes Z~ place during the final normalize.
'~ ~ 30 The following examples are illustrative of several ., .

!~ aspects of the invention.

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Example _I
Samples from ~hree heats (Healts A, B and C) of silicon steel were cast and processed into silicon steel having a cube-on-edge orientation. The chemistry of the heats appears hereinbelow in Table I.
TABLE I
Com osition (wt. %) P
Heat C Mn S B N Si Cu Al Fe A0.031 0.0320.020 0.0011 0.0047 3.15 0.32 0.004 Bal.
lO B0.032 0.036 0.020 0.0013 0.0043 3.15 0.35 0.004 Bal.
C0.030 0.0350.020 0.0013 0.0046 3.15 0.34 0.004 Bal.
Processing for the samples involved soaking at an elevated temperature for several hours, hot rolling to a nominal gage o~ 0.080 inch, hot roll band normalizing at a temperature o approximately 1740F, cold rolling to final gage, decarburizing, coating as described hereinbelow in Table II, and final ~exture annealing at a maximum temperature of 2150F in hydrogen. As for Table II, and in particular the sample identification, the letter referes to the heat and the number -to the sample from that 20 heat. For example, Al refers to Heat A, Sample 1.

TABI,E II

MgO H3BO3 Sample ~Parts, by wt.) (Parts, by wt.) A~, Bl Cl ~ 100 o A2 B2 C2 L00 2.3 (o.496 B) A3 B3 C3 100 4.6 (0.8% B) The samples were tested Eor permeabllity and core loss.
The results of the tests appear hereinbelow in Table III.

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___ _ Permeability Core Loss ( P at 17 KB) Al 1882 0.736 A 1892 0.725 A32 1921 0.668 Bl 1903 0.708 B2 1902 0.708 B3 1927 0.677 Cl 1558 1.27 C2 1891 0.697 C3 1908 0.677 The benefit of boron in the coating is clearly evident j 10 from Table III. Improvement in both permeability and core loss can be attributed thereto. Moreover, Samples A3, B3 and C3, with more than 0.5% boron in the coating, each attained a permeability in excess of 1900 (G/Oe) at 10 oersteds and a core loss below 0.700 watts per pound at 17 kilogauss.
Example II
- Additional groups of samples ~Group 4 through 8) were processed as were Group 1 through 3 samples, with the exception of the coating. The coatings applied to the Group 4 through 8 samples appear hereinbelow in Table IV, along with that applied to the Group 2 and 3 samples.
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TABLE IV

I MgO H3BO3 SiO2 ; Sample (Parts, by wt.) (Parts, by wt .L (Parts, by wt.) A2 B2 C2 100 2.3 ~0.4~ B) 0 A4 B4 C4 100 2.3 1.8 A5 B5 C5 100 2.3 3.6 A3 B3 C3 100 4.6 (0.8% B) 0 ~6 B6 C6 100 4.6 1.8 A7 B7 C7 100 4.6 3.6 A8 B8 C8 100 4.6 7.3 The samples were tested for permeability and core loss.

The results of the tests appear hereinbelow in Table V.

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Permeability Core Loss Sample (at 10 O ) (WPP at 17 KB) e A~ 1892 0.725 .
A4 1899 Q.705 A5 1901 0.702 B2 1902 0.708 : B4 1909 0.706 B5 1923 0.690 C2 1891 0.697 A3 1921 0.668 A6 1933 0.654 A7 1929 0.645 A8 1925 0.654 B3 1927 0.677 B6 1936 0.651 B7 1934 0.655 B8 1928 0.653 C3 1908 0.677 C 191~ 0.660 6 1901 0.649 C781908 0.655 :'', ' ~ 20 ., , ,~ .
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From Table V, a further improvement in magne',:ic properties i9 attributable to the additlon of SiO~ to the base coating~ SiOz increases permeabilities and decreases core losses. Moreover, as notable from Table VI, hereinbelow SiO2 improves the insulating characteristic of the subject base coating, Table VI lists the Franklin values at 900 psi for the C2, C4 and Cs and C3, C6, C7 and C8 samples; and as known to those skilled in the art, a perfect insulator has a Fr~klin value of 0~ whereas a perfect conductor has a Franklin value of 1 ampere.
' :; . TABLE VI
. Franklin Value - Sample .(at 900 psi) C2 . 0,97 C4 0,96 , . C~ 0, 90 1 5 . , (::3 ~ 93 ~i C6 0,95 C7 0, 90 C8 0,88 `, ~ ` , ` ., .
Note how the Franklin values decrease with increasing SiO2 addition~. Most favorable results were obtained when the coating contained mor e than 3, O parts SiC)~, .1 .
~j It will be apparent to tho9e 9killed in tha art that the novel principles of the invention disclosed hereis~ in connection wîth specific , . ~
examples thereof will suggest variou9 other modification9 and applications of the same, It is accordingly desired th~t in construing the breadth of the ~j appended claims they shall not be limited to the specific examples of the " .
invention described herein, .

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a process for producing electromagnetic silicon steel having a cube-on-edge orientation and a permeability of at least 1870 (G/Oe) at 10 oersteds, which process includes the steps of: preparing a melt of silicon steel containing from 0.02 to 0.06% carbon, from 0.0006 to 0.0080% boron, up to 0.0100%
nitrogen, no more than 0.008% aluminum and from 2.5 to 4.0%
silicon; casting said steel; hot rolling said steel; cold rolling said steel; decarburizing said steel; applying a refractory oxide coating to said steel; and final texture annealing said steel; the improvement comprising the steps of coating the surface of said steel with a refractory oxide coating con-sisting essentially of;
(a) 100 parts, by weight, of at least one substance from the group consisting of oxides, hydroxides, carbonates and boron compounds of magnesium, calcium, aluminum and titanium;
(b) up to 100 parts, by weight, of at least one other substance from the group consisting of boron and compounds thereof, said coating containing at least 0.1%, by weight, of boron;
(c) from 0.5 to 40 parts, by weight, of SiO2;
(d) up to 20 parts, by weight, of inhibiting substances or compounds thereof; and (e) up to 10 parts, by weight, of fluxing agents;
and final texture annealing said steel with said coating thereon.

2. A process according to claim 1, wherein said melt has at least 0.0008% boron.

3. A process according to claim 2, wherein said coating has at least 0 2% by weight, of boron.

4. A process according to claim 2, wherein said coating has at least 3 parts, by weight, of SiO2.

5. A process according to claim 2, wherein said inhibiting substances or compounds thereof are from the group consisting of sulfur, sulfur compounds, nitrogen compounds, selenium and selenium compounds.

6. A process according to claim 2, wherein said hot rolled steel has a thickness of from 0.050 at about 0.120 inch and wherein said hot rolled steel is cold rolled to a thickness of no more than 0.020 inch without an intermediate anneal between cold rolling passes.

7. A process according to claim 1, wherein said melt con-sists essentially of, by weight, 0.02 to 0.06% carbon, 0.015 to 0.15% manganese, 0.01 to 0.05% of material from the group con-sisting of sulfur and selenium, 0.0006 to 0.0080% boron, up to 0.0100% nitrogen, 2.5 to 4.0% silicon, up to 1.0% copper, no more than 0.008% aluminum, balance iron.

8. A process according to claim 7, wherein said melt has at least 0.0008% boron.

9. A process according to claim 1, wherein said steel has a permeability of at least 1900 (G/Oe) at 10 oersteds and a core loss of no more than 0.700 watts per pound at 17 kilogauss.

10. Primary recrystallized steel from a melt consisting essentially of, by weight, 0.02 to 0.06% carbon, 0.015 to 0.15%
manganese, 0.01 to 0.05% of material from the group consisting of sulfur and selenium, 0.0006 to 0.0080% boron, up to 0.0100%
nitrogen, 2.5 to 4.0% silicon, up to 1.0% copper, no more than 0.008% aluminum, balance iron; and having adhered thereto, a coating consisting essentially of:

Claim 10 continued...

(a) 100 parts, by weight, of at least one substance from the group consisting of oxides, hydroxides, carbonates and boron compounds of magnesium, calcium, aluminum and titanium;
(b) up to 100 parts, by weight, of at least one other substance from the group consisting of boron and compounds thereof, said coating containing at least 0.1%, by weight, of boron;
(c) from 0.5 to 40 parts, by weight, of SiO2;
(d) up to 20 parts, by weight, of inhibiting substances or compounds thereof; and (e) up to 10 parts, by weight, of fluxing agents.

11. Primary recrystallized steel according to claim 10, having at least 0.0008% boron.