US3681152A - Method of siliconizing - Google Patents
Method of siliconizing Download PDFInfo
- Publication number
- US3681152A US3681152A US128161A US3681152DA US3681152A US 3681152 A US3681152 A US 3681152A US 128161 A US128161 A US 128161A US 3681152D A US3681152D A US 3681152DA US 3681152 A US3681152 A US 3681152A
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- US
- United States
- Prior art keywords
- silicon
- steel
- temperature
- gage
- core loss
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D3/00—Diffusion processes for extraction of non-metals; Furnaces therefor
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F1/00—Etching metallic material by chemical means
Definitions
- a method of treating grain oriented silicon steel which comprises the steps of: heating grain oriented silicon steel at a temperature of from about 1900 F. to about 2300 F.; subjecting the steel to an acidic atmosphere which preferentially removes iron, thus enriching the member with silicon, for a period of time suflicient to increase the total proportion of silicon in the steel by about 0.4 to 4 wt. percent; and homogenizing the steel at a temperature and for a time suflicient for the silicon to disperse itself substantially uniformly therein.
- the present invention relates to a method for improving the properties of grain oriented silicon steel.
- Silicon steels are widely used in electrical equipment because of their superior electrical and magnetic properties. These properties are dependent upon the percentage of silicon contained therein. As the silicon content is increased, resistivity increases, magnetostriction decreases, magnetic anisotropy decreases, and core loss decreases. At approximately 6.25% silicon, the magnetostriction is essentially zero. This is of primary importance in the design of power transformers as magnetostriction is considered to be the source of audible noise which must be controlled. If noise is not below acceptable limits, it must be dampened by a process which is both costly and inconvenient. From the increased resistivity results lower eddy current losses in alternating magnetic fields and from the decreased magnetic anisotropy comes a lessening of the difierence in efi'ort necessary to magnetize a hard and soft direction in textured steel.
- siliconizing is concerned with silicon enrichment of the steel strip at final gage rather than by alloying in the melt.
- a method of siliconizing is described in Pat. No. 3,423,253, issued Ian. 21, 1969, in the names of Stuart L. Ames and William R. Bitler. It is a gaseous siliconizing process and involves a reaction between a heated strip and a siliconizing atmosphere which contains a nonreactive gas and a thermally decomposable silicon compound such as silicon tetrachloride.
- FIG. 1 is a plot showing an electron microprobe trace of the silicon content of grain oriented silicon steel treated according to this invention, prior to homogenization;
- FIG. 2 is a plot of core loss versus silicon content for homogenized grain oriented silicon steel.
- grain oriented silicon steel is heated at a temperature between about 1900 F. and about 2300 F., preferably between about 2050 F. and 2150 F., and subjected to an acidic atmosphere, preferably an atmosphere comprising hydrogen chloride vapor, which preferentially removes iron thus enriching the steel with silicon, i.e., increasing the proportion of silicon, while simultaneously reducing its gage.
- an acidic atmosphere preferably an atmosphere comprising hydrogen chloride vapor, which preferentially removes iron thus enriching the steel with silicon, i.e., increasing the proportion of silicon, while simultaneously reducing its gage.
- Subjection to the acidic atmosphere is for a period of time sufficient to increase the total proportion of silicon in the steel by about 0.4 to 4 wt. percent. No specific range can be set for the time period as it varies with such interrelated variables as the temperature at which the steel is heated and the concentration of acidic vapors within the acidic atmosphere.
- the steel can be heated while it is within the siliconizing chamber or prior to its entry therein.
- a minimum temperature of about 1900 F. is employed. At temperatures below about 1900 F. the diffusion of silicon into the steel does not proceed fast enough so as to preclude the buildup of excessive silicon at the surface and the inherent formation of severe compositional gradients. Such buildup and gradient formation is detrimental as it can destroy the soundness of the steels microstructure and result in undesirable magnetic properties, i.e., the microstructure becomes porous and/or cracked.
- a maximum temperature of about 2300 F. is observed because surface melting becomes a problem at higher temperatures.
- the acidic atmosphere must contain acidic vapors which preferentially remove iron rather than silicon.
- An exemplary group of acidic materials are hydrogen chloride, hydrogen bromide and hydrogen iodide, with hydrogen chloride being preferred.
- the vapors can be used straight or mixed with non-oxidizing gases. Suitable nonoxidizing gases include inert gases such as nitrogen and argon and reducing gases such as hydrogen. Nitrogen is a preferred non-oxidizing gas for dilution.
- the atmosphere can be static or flowing. When a flowing atmosphere is employed it is preferred that flow be in a direction counter to strip movement although it can be in the same direction.
- FIG. 1 shows the silicon gradient of grain oriented silicon steel treated in accordance with a preferred embodiment of the invention. Since it is necessary to achieve a chemically homogenous product the steel must be subjected to a homogenizing treatment. This homogenizing treatment can be accomplished immediately after the silicon content is increased to the desired level or at some subsequent time. It can even be performed after delivery of the steel to a purchaser.
- the homogenization is a solid state diffusion process wherein the silicon disperses itself substantially uniformly throughout the steel. It is time and temperature dependent as are other diffusion processes. As the temperature is increased the time is shortened and as the temperature is decreased the time is extended. A suitable, but not limiting time period is from about 0.25 hour to 24 hours with the temperature within the range of from about 1800 F. to about 2300 F. Preferred conditions are a time period of from about 1 hour to about 16 hours with the temperature within the range of from about 2050 F. to about 2200 F.
- Silicon steel members were heated to a temperature of 2100 F. and passed through a 12 inch long siliconizing chamber having an acidic atmosphere.
- the members originally had a silicon content of 3.2%, a gage of 0.0121 and a core loss of 0.606 W.P.P. at 15 kb.
- the acidic atmosphere employed was 2N :l HCl. It was delivered to the siliconizing chamber at a flow rate of /2 cubic foot per hour.
- the exposure time was determined by the line speed which was varied between 0.5 inch per minute and 2.4 inches per minute. The line speed for each member can be found in Table I along with other given data.
- the members After passing through the siliconizing chamber the members were homogenized by holding at a temperature of 2100 F. for a period of 16 hours.
- the homogenized members were found to have a final silicon content ranging from 3.6 to 4.2% silicon and a final gage ranging from 0.0114 to 0.0093 inch. Those with the higher silicon content and lower gage were processed at a slower line speed and hence had longer exposure times. They also had a lower core loss due to the fact that core loss as stated earlier decreases with increasing silicon and with decreasing gage. Since the decrease in core loss was attributable to both these factors, a column is provided in Table II wherein the core loss corrected to initial gage is given. The values were adjusted using a 0.025 W.P.P. correction factor for each mil change in gage. This conversion factor has been derived from statistics on minor gage variations in 0.011 inch production silicon steel.
- the corresponding correction factor for 0.014 inch production silicon steel is 0.035 W.P.P. per mil.
- a method of treating grain oriented silicon steel which comprises the steps of: heating grain oriented silicon steel at a temperature of from about 1900 F. to about 2300 F1; subjecting said silicon steel to an acidic atmosphere which preferentially removes iron, for a period of time sufficient to increase the total proportion of silicon in said steel by about 0.4 to 4 wt. percent; and homogenizing said steel at a temperature and for a time sufficient for the silicon to disperse itself substantially uniformly therein.
- said acidic atmosphere comprises acidic vapor from the group consisting of hydrogen chloride vapor, hydrogen bromide vapor, and hydrogen iodide vapor.
- said acidic atmosphere comprises a mixture of non-oxidizing gas and acidic vapor from the group consisting of hydrogen chloride vapor, hydrogen bromide vapor, and hydrogen iodide vapor.
- said acidic atmosphere comprises a mixture of hydrogen chloride vapor and non-oxidizing gas.
- a method according to claim 1 wherein said homogenizing is performed at a temperature of from about 1800 F. to about 2300 F. for a period of time of from about 0.25 hour to about 24 hours.
- a method according to claim 1 wherein said homogenizing is performed at a temperature of from about 2050 F. to about 2200 F. for a period of time of from about 1 hour to about 16 hours.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
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- Soft Magnetic Materials (AREA)
Abstract
Description
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12816171A | 1971-03-25 | 1971-03-25 |
Publications (1)
Publication Number | Publication Date |
---|---|
US3681152A true US3681152A (en) | 1972-08-01 |
Family
ID=22433937
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US128161A Expired - Lifetime US3681152A (en) | 1971-03-25 | 1971-03-25 | Method of siliconizing |
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US (1) | US3681152A (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3902930A (en) * | 1972-03-13 | 1975-09-02 | Nippon Musical Instruments Mfg | Method of manufacturing iron-silicon-aluminum alloy particularly suitable for magnetic head core |
US4173502A (en) * | 1976-12-09 | 1979-11-06 | General Electric Company | Method of producing silicon-iron sheet material with boron addition, and product |
-
1971
- 1971-03-25 US US128161A patent/US3681152A/en not_active Expired - Lifetime
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3902930A (en) * | 1972-03-13 | 1975-09-02 | Nippon Musical Instruments Mfg | Method of manufacturing iron-silicon-aluminum alloy particularly suitable for magnetic head core |
US4173502A (en) * | 1976-12-09 | 1979-11-06 | General Electric Company | Method of producing silicon-iron sheet material with boron addition, and product |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: ALLEGHENY LUDLUM CORPORATION Free format text: CHANGE OF NAME;ASSIGNOR:ALLEGHENY LUDLUM STEEL CORPORATION;REEL/FRAME:004779/0642 Effective date: 19860805 |
|
AS | Assignment |
Owner name: PITTSBURGH NATIONAL BANK Free format text: SECURITY INTEREST;ASSIGNOR:ALLEGHENY LUDLUM CORPORATION;REEL/FRAME:004855/0400 Effective date: 19861226 |
|
AS | Assignment |
Owner name: PITTSBURGH NATIONAL BANK Free format text: ASSIGNMENT OF ASSIGNORS INTEREST. RECORDED ON REEL 4855 FRAME 0400;ASSIGNOR:PITTSBURGH NATIONAL BANK;REEL/FRAME:005018/0050 Effective date: 19881129 |