GB1565474A

GB1565474A - Silcon steel and processing therefor

Info

Publication number: GB1565474A
Application number: GB24711/77A
Authority: GB
Original assignee: Allegheny Ludlum Industries Inc
Current assignee: Sunbeam Oster Co Inc
Priority date: 1976-06-17
Filing date: 1977-06-14
Publication date: 1980-04-23
Also published as: BR7703865A; AU511231B2; JPS52153825A; PL198882A1; IT1078912B; CA1086194A; AR217648A1; YU151477A; ES459890A1; ZA773084B; HU179103B; FR2355087A1; MX4371E; IN146549B; BE855834A; FR2355087B1; AU2552377A; RO71136A; CS218567B2; DE2726013A1

Description

(54) SILICON STEEL AND PROCESSING THEREFOR (71) We, ALLEGHENY LUDLUM INDUSTRIES, INC., a corporation organized under the laws of the Commonwealth of Pennsylvania, United States of America, of Two Oliver Plaza, Pittsburgh, Pennsylvania 15222, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to the manufacture of grain-oriented electromagnetic silicon steel, to the resulting steel and to primary recrystallized steel. Unless otherwise stated, percentages are by weight.

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 silicon steel. Described therein are processes for producing steel of high magnetic quality from boron-bearing silicon steel melts. Through this invention, there is provided a process which improves upon those of the cited patents; speaking broadly, the process improves upon 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.

The present invention provides a process for producing coated primary recrystallized silicon steel which process comprises preparing a melt of silicon steel containing from 0.02 to 0.06% carbon, from 0.0006 to 0.008% boron, up to 0.01% nitrogen, no more than 0.008% aluminum and from 2.5 to 4% silicon; casting said steel; hot rolling said steel; cold rolling said steel; decarburizing said steel; and applying to the surface of said steel a refractory oxide coating of: (a) 100 parts by weight, of at least one substance selected from 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 selected from boron and compounds thereof; (c) from 0.5 to 40 parts, by weight, of SiO2; (d) up to 20 parts by weight, of one or more grain growth inhibiting substances or compounds thereof; and (e) up to 10 parts, by weight, of one or more fluxing agents; said coating containing at least 0.1%, by weight, of boron. For purposes of definition, "one part" equals the total weight of (a) hereinabove, divided by 100.

It will be appreciated that constituents (b) (d), and (e) are optional; hence, only the upper limits of these constituents have been stated.

The present invention also provides primary recrystallized steel from a melt consisting of, by weight, 0.02 to 0.06% carbon, 0.015 to 0 15in manganese, 0.01 to 0.05% sulfur or selenium, 0.0006 to 0.008 //) boron, up to 0.01in nitrogen, 2.5 to 4% silicon, up to 1% copper, no more than 0.008% aluminum, balance iron and unavoidable impurities, said steel having adhered thereto a coating consisting of: (a) 100 parts, by weight, of at least one substance selected from 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 selected from boron and compounds thereof; (c) from 0.5 to 40 parts, by weight, of SiO2; (d) up to 20 parts, by weight, of one or more grain growth inhibiting substances or compounds thereof; and (e) up to 10 parts, by weight, of one or more fluxing agents; said coating containing at least 0.10/,, by weight, of boron.

Specific processing, as to the conventional 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 however, preferred to cold roll the steel to a thickness no greater than 0.02 inch, without an intermediate anneal between cold rolling passes; from a hot rolled band having a thickness of from about 0.05 to about 0.12 inch. Melts consisting 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 0.008% boron, up to 0.01% nitrogen, 2.5 to 4% silicon, up to 1% copper, no more than 0.008 aluminum, balance iron and unavoidable impurities have proven to be especially adaptable to the subject invention. Boron levels are preferably at least 0.0008%. Steel produced in accordance with the present invention has a permeability of at least 1870 (G/O,) at 10 oersteds. Preferably, the steel has a permeability of at least 1900 (G/Oe) at 10 oersteds and a core loss of no more than 0.7 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.

Likewise, the constituents which make up the coating can be applied together or as individual layers. It is, however, preferred at least 0.20/,, 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 grain growth inhibiting substances includable with the coating are usually from the group consisting of sulfur, sulfur compounds, nitrogen compounds, selenium and selenium compounds. Typical sources of boron are boric acid, fused boric acid (B2O3) ammonium pentaborate and sodium borate.

Typical fluxing agents include lithium oxide, sodium oxide and other oxides known to those skilled in the art. Those skilled in the art are, of course, aware of various ways of adding silica. Colloidal silica is, however, preferred.

As indicated above, steel in its primary recrystallized state with the above defined coating adhered thereto is part of the present invention; it has a thickness no greater than 0.02 inch and, by final texture annealing, is suitable for processing into grain-oriented silicon steel having a permeability of at least 1870 (G/O8) at 10 oersteds. Primary recrystallization takes place during the final anneal. The steel undergoes secondary recrystallization during the final texture anneal, but, as is well known, coated primary recrystallized steel is at times shipped from mills to another party who final texture anneals it. It is pointed out, however, that the "final anneal" takes place before the oxide coating is applied, whereas the "final texture anneal" is affected with the coated steel.

The following example is illustrative of several aspects of the invention.

Example Samples from three heats (Heats 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 Composition (wt. %) Heat C Mn S B N Si Cu Al Fe A 0.031 0.032 0.020 0.0011 0.0047 3.15 0.32 0.004 Bal.

B 0.032 0.036 0.020 0.0013 0.0043 3.15 0.35 0.004 Bal.

C 0.030 0.035 0.020 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 of 0.08 inch, hot roll band annealing at a temperature of approximately 17400 F, cold rolling to final gage, decarburizing, coating as described hereinbelow in Table II, and final texture annealing at a maximum temperature of 21500F in hydrogen. In each Heat five samples were evaluated and these are indicated by numbered suffixes, e.g. sample At denotes sample I of Heat A.

TABLE II MgO H3BO3 SiO2 Sample (Parts, by wt.) (Parts, by wt.) (Parts, by wt.) A, B1 C, 100 2.3(0.4% B) 1.8 A2 B2 C2 100 2.3 3.6 A3 B3 C3 100 4.6(0.8% B) 1.8 A4 B4 C4 100 4.6 3.6 A5 Bs C5 100 4.6 7.3 The samples were tested for permeability and core loss. The results of the tests appear hereinbelow in Table III.

TABLE III Permeability Core Loss Sample (at 10 Os) (WPP at 17 KB) A1 1899 0.705 A2 1901 0.702 B, 1909 0.706 B2 1923 0.690 C, 1892 0.708 C2 1899 0.677 A3 1933 0.654 A4 1929 0.645 As 1925 0.654 B3 1936 0.651 B4 1934 0.655 B5 1928 0.653 C3 1914 0.660 C4 1901 0.649 C5 1908 0.655 From Table III, an improvement in magnetic properties is attributable to the addition of SiO3 to the base coating. SiO3 increases permeabilities and decreases core losses. Moreover, as notable from Table IV hereinbelow, SiO3 improves the insulating characteristic of the present base coating. Table IV lists the Franklin values at 900 psi for the C1 and C2 and C3, C4 and C5 samples; and as known to those skilled in the art, a perfect insulator has a Franklin value of 0, whereas a perfect conductor has a Franklin value of 1 ampere.

TABLE IV Franklin Value Sample (at 900 psi) C, 0.96 C3 0.90 C3 0.95 C4 0.90 C5 0.88 Note how the Franklin values decrease with increasing SiO2 additions. Most favourable results were obtained when the coating contained more than 3 parts SiO2.

It will be apparent to those skilled in the art that the novel principles of the invention disclosed herein in connection with the specific example thereof will suggest various other modifications and applications of the same. It is accordingly desired that in construing the breadth of the appended claims they shall not be limited to the specific example of the invention described herein.

WHAT WE CLAIM IS: 1. A process for producing coated primary recrystallized silicon steel, which process comprises preparing a melt of silicon steel containing from 0.02 to 0.06 -, carbon, from 0.0006 to 0.008% boron, up to 0.01% nitrogen, no more than 0.008% aluminum and from 2.5 to 4% silicon; casting said steel; hot rolling said steel; cold rolling said steel; decarburizing said steel; and applying to the surface of said steel a refractory oxide coating of: (a) 100 parts, by weight, of at least one substance selected from 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 selected from boron and compounds thereof; (c) from 0.5 to 40 parts, by weight, of SiO2; (d) up to 20 parts, by weight, of one or more grain growth inhibiting substances or compounds thereof; and (e) up to 10 parts, by weight, of one or more fluxing agents; said coating containing at least 0.1%, by weight, of boron.

2. A process according to Claim 1, wherein said melt contains at least 0.0008 < boron.

3. A process according to Claim 1 or 2, wherein said coating contains at least 0.2 > by weight, of boron.

4. A process according to Claim 1, 2 or 3, wherein said coating contains at least 3 parts, by weight, of SiO2.

5. A process according to any one of the preceding claims, wherein said constituent (d) is selected from sulfur, sulfur compounds, nitrogen compounds, selenium and selenium compounds.

6. A process according to any one of the preceding claims, wherein said hot rolled steel has a thickness of from 0.05 to 0.12 inch and wherein said hot rolled steel is cold rolled to a thickness of no more than 0.02 inch without an intermediate anneal between cold rolling passes.

7. A process according to any one of the preceding claims, wherein said melt consists of, by weight, 0.02 to 0.06% carbon, 0.015 to 0.15% manganese, 0.01 to 0.05 ,'n sulfur or selenium, 0.0006 to 0.008% boron, up to 0.01% nitrogen, 2.5 to 4% silicon, up to 1% copper, no more than 0.008% aluminum, balance iron and unavoidable impurities.

8. A process for producing coated primary recrystallized steel substantially as herein described with reference to the Example.

9. Coated primary recrystallized steel whenever produced in accordance with the process claimed in any one of the preceding claims.

10. A process for producing secondary recrystallized electromagnetic steel having cube-on-edge orientation which comprises final texture annealing the coated steel claimed in Claim 9.

11. A process for producing grain-oriented electromagnetic silicon steel substantially as herein described with reference to the Example.

12. Primary recrystallized steel from a melt consisting of, by weight, 0.02 to 0.06 carbon, 0.015 to 0.15% manganese, 0.01 to 0.05% sulfur or selenium, 0.0006 to 0.008 ' boron, up to 0.01% nitrogen, 2.5 to 4 , silicon, up to 1% copper, no more than 0.008 ' aluminum, balance iron and unavoidable impurities, said steel having adhered thereto a coating consisting of: (a) 100 parts, by weight, of at least one substance selected from 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 selected from boron and compounds thereof; (c) from 0.5 to 40 parts, by weight, of Six3;

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Note how the Franklin values decrease with increasing SiO2 additions. Most favourable results were obtained when the coating contained more than 3 parts SiO2. It will be apparent to those skilled in the art that the novel principles of the invention disclosed herein in connection with the specific example thereof will suggest various other modifications and applications of the same. It is accordingly desired that in construing the breadth of the appended claims they shall not be limited to the specific example of the invention described herein. WHAT WE CLAIM IS:

1. A process for producing coated primary recrystallized silicon steel, which process comprises preparing a melt of silicon steel containing from 0.02 to 0.06 -, carbon, from 0.0006 to 0.008% boron, up to 0.01% nitrogen, no more than 0.008% aluminum and from 2.5 to 4% silicon; casting said steel; hot rolling said steel; cold rolling said steel; decarburizing said steel; and applying to the surface of said steel a refractory oxide coating of: (a) 100 parts, by weight, of at least one substance selected from 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 selected from boron and compounds thereof; (c) from 0.5 to 40 parts, by weight, of SiO2; (d) up to 20 parts, by weight, of one or more grain growth inhibiting substances or compounds thereof; and (e) up to 10 parts, by weight, of one or more fluxing agents; said coating containing at least 0.1%, by weight, of boron.

12. Primary recrystallized steel from a melt consisting of, by weight, 0.02 to 0.06 carbon, 0.015 to 0.15% manganese, 0.01 to 0.05% sulfur or selenium, 0.0006 to 0.008 ' boron, up to 0.01% nitrogen, 2.5 to 4 ,Ó silicon, up to 1% copper, no more than 0.008 ' aluminum, balance iron and unavoidable impurities, said steel having adhered thereto a coating consisting of: (a) 100 parts, by weight, of at least one substance selected from 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 selected from boron and compounds thereof; (c) from 0.5 to 40 parts, by weight, of Six3;

(d) up to 20 parts, by weight, of one or more grain growth inhibiting substances or compounds thereof; and (e) up to 10 parts by weight, of one or more fluxing agents; said coating containing at least 0.1%, by weight, of boron.

13. Steel according to Claim 12, having at least 0.0008% boron.

14. Primary recrystallized steel having a coating thereon substantially as herein described with reference to any one of the Samples shown in the Example.