US3725521A - Method of making steel powder particles of select electrical resistivity - Google Patents

Method of making steel powder particles of select electrical resistivity Download PDF

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US3725521A
US3725521A US00085240A US3725521DA US3725521A US 3725521 A US3725521 A US 3725521A US 00085240 A US00085240 A US 00085240A US 3725521D A US3725521D A US 3725521DA US 3725521 A US3725521 A US 3725521A
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resin
particles
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steel
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H Ebling
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/02—Making ferrous alloys by powder metallurgy
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material

Definitions

  • ABSTRACT A method of making a compressed steel powder article having high resistivity to be used as an electrical component.
  • Steel powder having a particle size finer than 28 mesh is treated with a non-aqueous solution of an organic thermosetting resin to coat the particles with the resin. After evaporation of the solvent and curing of the resin, the coated particles are compressed to form a non-sintered, compressed steel powder article having high electrical resistivity.
  • the compressed article can be subsequently heated to an elevated temperature to stress relieve the article and stabilize the resistivity.
  • This invention relates to a method of making a compressed steel powder article having a select electrical resistivity.
  • Rotors, stators, and other magenetic cores, for use in electrical equipment are usually not formed of single piece wrought materials due to high eddy current losses developed in the low resistivity wrought iron.
  • the conventional practice in forming rotors, stators and mag- 1 netic cores is to use a laminated structure formed from desired shape.
  • U.S. Pat. No. 3,245,841 describes a process of producing high electrical resistivity steel powder by treating the steel powder with a phosphoric acid and chromic acid aqueous solution to provide a surface coating on the steel particles, consisting principally of iron phosphate and chromium compounds.
  • any electrically insulating coating applied to the particles must be capable of withstanding stress relieving without decomposing or reacting with the steel, if the part is to be subjected to a stress relieving treatment.
  • the invention is directed to a method of making a compressed steel powder article having a select electrical resistivity which can be used in a wide variety of electrical components.
  • steel powder having a particle size finer than about 28 mesh is initially treated with a non-aqueous solution of an uncured organic thermosetting resin to coat the individual particles of steel powder. After evaporation of the solvent, the coated particles are compressed to form a non-sintered compressed powder article.
  • the cured resin should be capable of maintaining its high electrical resistivity without decomposing or reacting with the base metal at temperatures above 250F and up to l,200F.
  • the compressed article can be stress relieved at temperatures up to 1,200F.
  • the resulting heat treated, compressed steel powder part has a high stabilized resistivity and can be operated at elevated temperatures without substantial variation in resistivity.
  • the steel powder to be employed can be prepared by the method shown in the U.S. Pat. No. 3,325,277 to Huseby, in which a stream of molten steel is atomized by a sheet of high pressure water to form irregularly shaped particles which are subsequently heat treated to soften the particles and reduce the carbon and residual oxygen content.
  • the steel powder has a carbon content generally in the range of 0.001 to 0.1 percent and preferably less than 0.05 percent.
  • the steel may contain alloying additions such as nickel, silicon aluminum, and the like, up to about 5 percent by weight, depending upon the magnetic characteristics desired.
  • the size of the steel powder is not particularly critical and the powder generally has a size finer than about 28 mesh (590 microns). There is no limit to the fineness of the steel powder, but from a practical standpoint, if the particle size is finer than mesh, the cost of the powder and the mechanical strength of the article are diminished.
  • the steel particles are individually coated with an uncured organic thermosetting resin.
  • Silicone resins have proven very satisfactory as the coating material.
  • Polyorgano-siloxanes are characterized by a molecular backbone of alternate atoms of silicon and oxygen with organic groups attached to the silicon atoms. The type of organic groups and the extent of crosslinking determine whether the silicone will be fluid, elastomeric or resinous.
  • the basic polydimethylsiloxane structure is as where X is an integer of at least 5.
  • silicone resin More specifically, the following silicone resin can be employed:
  • n and m are integers having a value in the range of 200 to 500.
  • polyimide resins of the type described in U.S. Pat. Nos. 3,179,614 and 3,179,634 can also be utilized as the coating material.
  • the amount of the resin to be used is important in carrying out the invention, and generally, the resin is employed in an amount from 0.06 to 1.0 percent by weight of the steel powder, with approximately 0.25 to 0.50 percent being preferred.
  • the resin is applied in the uncured state to the individual dual steel particles by means of a non-aqueous treating solution.
  • the solvent to be employed in the solution can be any volatile organic solvent, capable of dissolving the resin to be used.
  • solvents such as toluene, xylene, benzene, and the like, may be employed.
  • the particular nature of the solvent is not critical and any volatile readily available organic solvent may be employed.
  • the concentration of the treating solution is not critical and the solution can have any degree of dilution which will facilitate mixing with the steel powder. It has been found that a concentration in which 1 gram of the resin is dissolved in 160 to 240 ml of the solvent is satisfactory.
  • a finely divided inert filler can be incorporated with the resin.
  • the filler should have a substantially smaller particle size than the steel powder, and preferably has a particle size finer than microns.
  • the filler may take the form of quartz, diamotaceous earth, kaolin, talc, aluminum silicate, calcium carbonate, and the like.
  • the amount of filler, if used, is not critical and the resin may contain from 0.01 to 3 parts by weight of filler to one part resin. When a filler is utilized, the combined weight of the filler and resin should be from 0.06 to 1.0 percent by weight of the steel powder.
  • the particles of filler will be dispersed or suspended in the treating solution.
  • the resin and the filler will coat the steel particles.
  • the steel powder and the treating solution can be mixed together by use of conventional blending equipment such as a rotating drum. It is not necessary to heat the materials and the materials are generally mixed together at room temperature. During the mixing operation, the treating solution will tend to completely coat or encapsulate the individual steel particles.
  • the solvent is evaporated. While heating is not necessary for evaporation of the solvent, under normal conditions, heating is utilized in order to accelerate the evaporation.
  • the resin is cured. While the resin will crosslink or cure at room temperature, heat is preferred to accelerate the cure. In practice, it has been found that heating the coated particles to a temperature in the range of about 150 to 250F for a period of to 60 minutes will not only evaporate the solvent during the initial stage of the heating treatment, but will also cure the resin in the latter state of this heat treatment.
  • the thickness of the cured coating is not critical, but it is believed that the coating, in most cases, is continuous to virtually encapsulate the individual steel particles and is generally less than 1 micron in thickness. Due to the very thin nature of the coating, the particles after curing of the resin, will not adhere together, but the powder mass will still be flowable although the rate of flow will not be as great as the uncoated particles.
  • the coated particles are compressed into the shape of the desired component or article.
  • the compressing is preferably carried out at room temperature, although temperatures up to the decomposition temperature of the resin can be used.
  • the coated powder is compressed preferably with a pressure in excess of 50 tsi and generally in the range of about 30 to 100 tsi.
  • the coating will flow and squeeze between the particles.
  • the compression is normally done without heating there will be no sintering of the steel particles and the particles will be held together primarily by the mechanical interlock between the irregular particles and the adhesive nature of the coating.
  • the cured resin is characterized by the ability to maintain its high electrical resistance without decomposing or reacting with the steel when heated to a temperature in the range of 250 to 1,200F
  • the compressed part can be stress relieved by heating to a temperature in the range from about 500 to 1,200 F and below the decomposition temperature of the resin coating.
  • the heat treatment serves a multiple function in that it removes stress from the compressed part, stabilizes the resistivity so that the resistivity will be less likely to change during service, and increases the mechanical strength of the compressed part.
  • the resin to be used as the coating should have a decomposition temperature in the upper portion of the 250F to 1,200F so that the part can be heated to the stress relieving temperature without decomposition of the resin. If the part is not to be stress relieved, then a resin having a lower decomposition temperature can be used.
  • the part After stress relieving treatment the part is cooled to room temperature.
  • the compressed part has a density of at least percent of theoretical density of iron and generally the treated powder has a compressibility greater than 7.4 grams/cc at a compaction pressure of 60 tsi.
  • the compressed iron powder article of the method of the invention can be used for a wide variety of electrical components such as rotors, stators, transformer cores, chokes, and the like.
  • the electrical resistivity of the compressed part can vary between 15 to 100,000 microhm cm. with the particular resistivity depending on the ultimate function and use of the electrical component.
  • the use of the silicone resin as the coating material has the added advantage that it serves as a lubricant during the compression step. By using the silicone resin it is not necessary to lubricate the die with a separate lubricant during the compression step.
  • EXAMPLE I 908 grams of steel powder having a carbon content of 0.005 percent and having a particle size in the range of 28 to 100 mesh were mixed with 50 ml ofa 0.25 percent by weight toluene solution of silicone resin GE- RTV 102. After thorough mixing of the ingredients the resulting coated powder was heated in a circulating oven at a temperature of 250F to evaporate the toluene and cure the resin.
  • the coated particles were compressed at room temperature at 60 tsi into a part having the dimensions 1 A X k X /4 inches. Subsequently the compressed part was heated to a temperature of 800F for a period of 1 hour to stress relieve the part and stabilize the resistivity.
  • the resulting heat treated steel powder part had a density of 7.41 grams/cc.
  • the part had a resistivity of 15,000 microhm cm., as pressed, and a resistivity of 1,800 microhm cm. after stress relieving.
  • the compressed part had a transverse rupture strength of 4,830 psi, as pressed, and 8,590 psi after the stress relieving treatment.
  • the compressed part was then stress relieved at a temperature of 800F for a period of 1 hour.
  • the resulting stress relieved part had a density of 7.40 grams/cc, and a resistivity, as pressed, of 7,300 microhm cm. and a resistivity, after stress relieving, of 1,300 microhm cm.
  • EXAMPLE 111 A compressed steel powder part was prepared in a manner similar to that of Example 1, except the treating solution contained 0.06 percent of silicone resin GE RTV-l02.
  • the resulting compressed and stress relieved part had a density of 7.43 grams/cc and the compressed powder part had a resistivity of 16,500 microhm cm., as pressed, and a resistivity of 1,200 microhm cm. after stress relieving.
  • the compressed article had a transverse rupture strength of 5,800 psi, as pressed, and 10,000 psi after stress relieving.
  • a method of preparing a compressed steel powder article having a predetermined electrical resistivity to be used in electrical apparatus comprising the steps of: a. dissolving an uncured thermosetting resin in an organic non-aqueous solvent to provide a treating solution,
  • a method of preparing a compressed steel powder article having a predetermined electrical resistivity to be used in an electrical apparatus comprising the steps of:
  • said resin is selected from the group consisting of silicone resins and polyimide resins.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Soft Magnetic Materials (AREA)

Abstract

A method of making a compressed steel powder article having high resistivity to be used as an electrical component. Steel powder having a particle size finer than 28 mesh is treated with a nonaqueous solution of an organic thermosetting resin to coat the particles with the resin. After evaporation of the solvent and curing of the resin, the coated particles are compressed to form a non-sintered, compressed steel powder article having high electrical resistivity. The compressed article can be subsequently heated to an elevated temperature to stress relieve the article and stabilize the resistivity.

Description

United States Patent [191 Ebling' 51 Apr. 3, 1973 [54] METHOD OF MAKING STEEL POWDER PARTICLES OF SELECT ELECTRICAL RESISTIVITY [7S Inventor: Hilmer F. Ebling, Milwaukee, Wis.
v [73] Assignee: A. O. Smith Corporation, Milwaukee, Wis.
[22} Filed: Oct. 29, 1970 [21] Appl. No.: 85,240
52 Us. Cl "264/104, 264/111 [51] Int. Cl. ..B22f 9/00 [58] Field of Search ..264/1 1 l, 104
[56] References Cited 7 UNITED STATES PATENTS 3,166,615 1/1965 Farrell ..264/11l 3,216,074 11/1965 Harrison ..264/111 2,979,401 4/1961 Szymaszek 264/11 1 3,414,641 12/1968 Miller ..264/l04 Primary ExqminerRobert F. White Assistant ExaminerJ. R. Hall, Jr. Attorney-Andrus, Sceales, Starke & Sawall [5 7] ABSTRACT A method of making a compressed steel powder article having high resistivity to be used as an electrical component. Steel powder having a particle size finer than 28 mesh is treated with a non-aqueous solution of an organic thermosetting resin to coat the particles with the resin. After evaporation of the solvent and curing of the resin, the coated particles are compressed to form a non-sintered, compressed steel powder article having high electrical resistivity. The compressed article can be subsequently heated to an elevated temperature to stress relieve the article and stabilize the resistivity.
5 Claims, No Drawings METHOD OF MAKING STEEL POWDER PARTICLES OF SELECT ELECTRICAL RESISTIVITY BACKGROUND OF THE INVENTION This invention relates to a method of making a compressed steel powder article having a select electrical resistivity.
Rotors, stators, and other magenetic cores, for use in electrical equipment are usually not formed of single piece wrought materials due to high eddy current losses developed in the low resistivity wrought iron. The conventional practice in forming rotors, stators and mag- 1 netic cores is to use a laminated structure formed from desired shape. U.S. Pat. No. 3,245,841 describes a process of producing high electrical resistivity steel powder by treating the steel powder with a phosphoric acid and chromic acid aqueous solution to provide a surface coating on the steel particles, consisting principally of iron phosphate and chromium compounds.
It has been found that on a commercial scale the water used in the treating solution, such as that disclosed in the aforementioned patent, cannot be evaporated from a large mass of steel powder without oxidation of the steel due to the difficulty in aerating the powder mass. Oxidation of the steel particles results in a loss of mechanical properties in the compressed part and lowers the density of the compressed part.
It has also been found that when preparing electrical components from steel powder that some compressed parts should be stress relieved in order to obtain stability of resistivity under operating conditions, which can be up to 300F, although this may not be necessary in all applications. Thus, any electrically insulating coating applied to the particles must be capable of withstanding stress relieving without decomposing or reacting with the steel, if the part is to be subjected to a stress relieving treatment.
SUMMARY OF THE INVENTION The invention is directed to a method of making a compressed steel powder article having a select electrical resistivity which can be used in a wide variety of electrical components. In accordance with the invention, steel powder having a particle size finer than about 28 mesh is initially treated with a non-aqueous solution of an uncured organic thermosetting resin to coat the individual particles of steel powder. After evaporation of the solvent, the coated particles are compressed to form a non-sintered compressed powder article. In the compressed part, the cured resin should be capable of maintaining its high electrical resistivity without decomposing or reacting with the base metal at temperatures above 250F and up to l,200F. To stabilize the resistivity of the article at operation conditions, the compressed article can be stress relieved at temperatures up to 1,200F.
The resulting heat treated, compressed steel powder part has a high stabilized resistivity and can be operated at elevated temperatures without substantial variation in resistivity.
As the coating is applied to the steel particles by use of a non-aqueous solution, oxidation of the individual steel particles will be prevented during the treating operation. The insures that the mechanical properties of the compressed part will be maintained and provides improved uniformity from part-to-part.
DESCRIPTION OF THE PREFERRED EMBODIMENT The steel powder to be employed can be prepared by the method shown in the U.S. Pat. No. 3,325,277 to Huseby, in which a stream of molten steel is atomized by a sheet of high pressure water to form irregularly shaped particles which are subsequently heat treated to soften the particles and reduce the carbon and residual oxygen content.
The steel powder has a carbon content generally in the range of 0.001 to 0.1 percent and preferably less than 0.05 percent. In addition, the steel may contain alloying additions such as nickel, silicon aluminum, and the like, up to about 5 percent by weight, depending upon the magnetic characteristics desired.
The size of the steel powder is not particularly critical and the powder generally has a size finer than about 28 mesh (590 microns). There is no limit to the fineness of the steel powder, but from a practical standpoint, if the particle size is finer than mesh, the cost of the powder and the mechanical strength of the article are diminished.
The steel particles are individually coated with an uncured organic thermosetting resin. Silicone resins have proven very satisfactory as the coating material. Polyorgano-siloxanes are characterized by a molecular backbone of alternate atoms of silicon and oxygen with organic groups attached to the silicon atoms. The type of organic groups and the extent of crosslinking determine whether the silicone will be fluid, elastomeric or resinous. The basic polydimethylsiloxane structure is as where X is an integer of at least 5.
More specifically, the following silicone resin can be employed:
I CH2 where both n and m are integers having a value in the range of 200 to 500.
In addition, polyimide resins of the type described in U.S. Pat. Nos. 3,179,614 and 3,179,634 can also be utilized as the coating material.
The amount of the resin to be used is important in carrying out the invention, and generally, the resin is employed in an amount from 0.06 to 1.0 percent by weight of the steel powder, with approximately 0.25 to 0.50 percent being preferred.
The resin is applied in the uncured state to the individual dual steel particles by means of a non-aqueous treating solution. The solvent to be employed in the solution can be any volatile organic solvent, capable of dissolving the resin to be used. In general, solvents such as toluene, xylene, benzene, and the like, may be employed. As the solvent is subsequently evaporated and is not present in the final product, the particular nature of the solvent is not critical and any volatile readily available organic solvent may be employed.
The concentration of the treating solution is not critical and the solution can have any degree of dilution which will facilitate mixing with the steel powder. It has been found that a concentration in which 1 gram of the resin is dissolved in 160 to 240 ml of the solvent is satisfactory.
It is contemplated that a finely divided inert filler can be incorporated with the resin. The filler should have a substantially smaller particle size than the steel powder, and preferably has a particle size finer than microns. The filler may take the form of quartz, diamotaceous earth, kaolin, talc, aluminum silicate, calcium carbonate, and the like. The amount of filler, if used, is not critical and the resin may contain from 0.01 to 3 parts by weight of filler to one part resin. When a filler is utilized, the combined weight of the filler and resin should be from 0.06 to 1.0 percent by weight of the steel powder.
As the tiller will not be dissolved by the solvent, the particles of filler will be dispersed or suspended in the treating solution. In this case, when the treating solution is mixed with steel powder, the resin and the filler will coat the steel particles.
The steel powder and the treating solution can be mixed together by use of conventional blending equipment such as a rotating drum. It is not necessary to heat the materials and the materials are generally mixed together at room temperature. During the mixing operation, the treating solution will tend to completely coat or encapsulate the individual steel particles.
After the mixing operation, the solvent is evaporated. While heating is not necessary for evaporation of the solvent, under normal conditions, heating is utilized in order to accelerate the evaporation. Following evaporation of the solvent, the resin is cured. While the resin will crosslink or cure at room temperature, heat is preferred to accelerate the cure. In practice, it has been found that heating the coated particles to a temperature in the range of about 150 to 250F for a period of to 60 minutes will not only evaporate the solvent during the initial stage of the heating treatment, but will also cure the resin in the latter state of this heat treatment.
The thickness of the cured coating is not critical, but it is believed that the coating, in most cases, is continuous to virtually encapsulate the individual steel particles and is generally less than 1 micron in thickness. Due to the very thin nature of the coating, the particles after curing of the resin, will not adhere together, but the powder mass will still be flowable although the rate of flow will not be as great as the uncoated particles.
After curing of the coating, the coated particles are compressed into the shape of the desired component or article. The compressing is preferably carried out at room temperature, although temperatures up to the decomposition temperature of the resin can be used. The coated powder is compressed preferably with a pressure in excess of 50 tsi and generally in the range of about 30 to 100 tsi. During the compression, the coating will flow and squeeze between the particles. As the compression is normally done without heating there will be no sintering of the steel particles and the particles will be held together primarily by the mechanical interlock between the irregular particles and the adhesive nature of the coating.
In the compressed part, the cured resin is characterized by the ability to maintain its high electrical resistance without decomposing or reacting with the steel when heated to a temperature in the range of 250 to 1,200F
Following compression, the compressed part can be stress relieved by heating to a temperature in the range from about 500 to 1,200 F and below the decomposition temperature of the resin coating. The heat treatment serves a multiple function in that it removes stress from the compressed part, stabilizes the resistivity so that the resistivity will be less likely to change during service, and increases the mechanical strength of the compressed part. If the compressed part is to be stress relieved, the resin to be used as the coating should have a decomposition temperature in the upper portion of the 250F to 1,200F so that the part can be heated to the stress relieving temperature without decomposition of the resin. If the part is not to be stress relieved, then a resin having a lower decomposition temperature can be used.
After stress relieving treatment the part is cooled to room temperature.
It has been found that improved properties are obtained if the resin is fully cured prior to compression, rather than curing the resin during the stress relieving treatment and following compression. It is believed that fully curing the resin prior to compression volatizes all of the solvent, so that there is no residual solvent present in the particle mass which would adversely affect the compression.
The compressed part has a density of at least percent of theoretical density of iron and generally the treated powder has a compressibility greater than 7.4 grams/cc at a compaction pressure of 60 tsi.
The compressed iron powder article of the method of the invention can be used for a wide variety of electrical components such as rotors, stators, transformer cores, chokes, and the like. The electrical resistivity of the compressed part can vary between 15 to 100,000 microhm cm. with the particular resistivity depending on the ultimate function and use of the electrical component.
The use of the silicone resin as the coating material has the added advantage that it serves as a lubricant during the compression step. By using the silicone resin it is not necessary to lubricate the die with a separate lubricant during the compression step.
The following examples illustrate the process of the invention.
EXAMPLE I 908 grams of steel powder having a carbon content of 0.005 percent and having a particle size in the range of 28 to 100 mesh were mixed with 50 ml ofa 0.25 percent by weight toluene solution of silicone resin GE- RTV 102. After thorough mixing of the ingredients the resulting coated powder was heated in a circulating oven at a temperature of 250F to evaporate the toluene and cure the resin.
Following the heating the coated particles were compressed at room temperature at 60 tsi into a part having the dimensions 1 A X k X /4 inches. Subsequently the compressed part was heated to a temperature of 800F for a period of 1 hour to stress relieve the part and stabilize the resistivity.
The resulting heat treated steel powder part had a density of 7.41 grams/cc. The part had a resistivity of 15,000 microhm cm., as pressed, and a resistivity of 1,800 microhm cm. after stress relieving.
The compressed part had a transverse rupture strength of 4,830 psi, as pressed, and 8,590 psi after the stress relieving treatment.
EXAMPLE II into an article having the dimensions 1 V4 X k X A inches.
The compressed part was then stress relieved at a temperature of 800F for a period of 1 hour.
The resulting stress relieved part had a density of 7.40 grams/cc, and a resistivity, as pressed, of 7,300 microhm cm. and a resistivity, after stress relieving, of 1,300 microhm cm.
EXAMPLE 111 A compressed steel powder part was prepared in a manner similar to that of Example 1, except the treating solution contained 0.06 percent of silicone resin GE RTV-l02.
The resulting compressed and stress relieved part had a density of 7.43 grams/cc and the compressed powder part had a resistivity of 16,500 microhm cm., as pressed, and a resistivity of 1,200 microhm cm. after stress relieving.
The compressed article had a transverse rupture strength of 5,800 psi, as pressed, and 10,000 psi after stress relieving.
Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.
1 claim: 1. A method of preparing a compressed steel powder article having a predetermined electrical resistivity to be used in electrical apparatus, comprising the steps of: a. dissolving an uncured thermosetting resin in an organic non-aqueous solvent to provide a treating solution,
. blending the solution with a quantity of steel particles having a particle size finer than 28 mesh and a carbon content in the range of 0.001 to 0.10 percent by weight to coat said particles, said resin on a solids basis being present in an amount of 0.06 to 1.0 percent by weight of the steel particles,
0. evaporating the solvent,
d. curing the resin to provide a flowable mass of coated particles, and
e. compressing the coated particles at a pressure in the range of 30 to 100 tsi to mechanically interlock the steel particles and form a compressed steel article having a density greater than percent of the theoretical density of pure iron and having an electrical resistivity in the range of 15 to 100,000 microhm cm.
2. The method of claim 1, wherein the compressing is done at a temperature below the sintering temperature of the steel particles.
3. The method of claim 1, wherein the compressing is done at room temperature.
4. A method of preparing a compressed steel powder article having a predetermined electrical resistivity to be used in an electrical apparatus comprising the steps of:
a. dissolving an uncured thermosetting resin having a decomposition temperature in the range of 500 to 1,200F in an organic non-aqueous solvent to provide a treating solution,
. blending the solution with a quantity of steel particles having a particle size finer than 28 mesh and a carbon content in the range of 0.001 to 0.10 percent by weight to coat said particles, said resin on a solids basis being present in an amount of 0.06 to 1.0 percent by weight of the steel particles,
c. evaporating the solvent,
. curing said resin to provide a flowable mass of coated particles,
e. compressing the coated particles at a pressure in I the range of 30 to tsi to mechanically interlock the steel particles and form a compressed steel article having a density g greater than 90 percent of the theoretical density of pure iron and having an electrical resistivity in the range of 15 to 100,000
microhm cm., and
f. heating the compressed article to a temperature in the range of 500 to 1,200F and below the decomposition temperature of the resin to stress relieve the article and stabilize the resistivity.
5. The method of claim 4, wherein said resin is selected from the group consisting of silicone resins and polyimide resins.

Claims (4)

  1. 2. The method of claim 1, wherein the compressing is done at a temperature below the sintering temperature of the steel particles.
  2. 3. The method of claim 1, wherein the compressing is done at room temperature.
  3. 4. A method of preparing a compressed steel powder article having a predetermined electrical resistivity to be used in an electrical apparatus comprising the steps of: a. dissolving an uncured thermosetting resin having a decomposition temperature in the range of 500* to 1,200*F in an organic non-aqueous solvent to provide a treating solution, b. blending the solution with a quantity of steel particles having a particle size finer than 28 mesh and a carbon content in the range of 0.001 to 0.10 percent by weight to coat said particles, said resin on a solids basis being present in an amount of 0.06 to 1.0 percent by weight of the steel particles, c. evaporating the solvent, d. curing said resin to provide a flowable mass of coated particles, e. compressing the coated particles at a pressure in the range of 30 to 100 tsi to mechanically interlock the steel particles and form a compressed steel article having a density g greater than 90 percent of the theoretical density of pure iron and having an electrical resistivity in the range of 15 to 100,000 microhm cm., and f. heating the compressed article to a temperature in the range of 500* to 1,200*F and below the decomposition temperature of the resin to stress relieve the article and stabilize the resistivity.
  4. 5. The method of claim 4, wherein said resin is selected from the group consisting of silicone resins and polyimide resins.
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Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5334612A (en) * 1976-09-14 1978-03-31 Komatsu Mfg Co Ltd Method of producing industrial raw material out of powder
US4601753A (en) * 1983-05-05 1986-07-22 General Electric Company Powdered iron core magnetic devices
US4601765A (en) * 1983-05-05 1986-07-22 General Electric Company Powdered iron core magnetic devices
US4675143A (en) * 1984-12-28 1987-06-23 Ube Industries, Ltd. Process for producing a shaped electroconductive thermoplastic resin composition article
US4810524A (en) * 1982-06-18 1989-03-07 Tdk Corporation Inorganic powders with improved dispersibility
EP0375627A1 (en) * 1988-10-28 1990-06-27 NUOVA MERISINTER S.p.A. A process for pre-treating powders with a solid lubricant and heat in preparation for compacting operations
US4977386A (en) * 1987-10-13 1990-12-11 Leda Logarithmic Electrical Devices For Automation S.R.L. Electric resistor producible in a wide range of specific resistance values, and relative manufacturing process
JPH0831383B2 (en) 1985-03-28 1996-03-27 株式会社東芝 Large current reactor
US5567746A (en) * 1994-12-16 1996-10-22 General Motors Corporation Moldable ferromagnetic particles and method
US5595609A (en) * 1993-04-09 1997-01-21 General Motors Corporation Annealed polymer-bonded soft magnetic body
US5629092A (en) * 1994-12-16 1997-05-13 General Motors Corporation Lubricous encapsulated ferromagnetic particles
US20030077448A1 (en) * 2001-03-27 2003-04-24 Kawasaki Steel Corporation Ferromagnetic-metal-based powder, powder core using the same, and manufacturing method for ferromagnetic-metal-based powder
US6635122B2 (en) * 1998-11-23 2003-10-21 Hoeganaes Corporation Methods of making and using annealable insulated metal-based powder particles
US20030232196A1 (en) * 2002-06-14 2003-12-18 Krishnamurthy Anand Coated ferromagnetic particles and composite magnetic articles thereof
US20050016658A1 (en) * 2003-07-24 2005-01-27 Thangavelu Asokan Composite coatings for ground wall insulation in motors, method of manufacture thereof and articles derived therefrom
US20050019558A1 (en) * 2003-07-24 2005-01-27 Amitabh Verma Coated ferromagnetic particles, method of manufacturing and composite magnetic articles derived therefrom
US20050142349A1 (en) * 2003-12-29 2005-06-30 Irwin Patricia C. Composite coatings for groundwall insulation, method of manufacture thereof and articles derived therefrom
US20070243400A1 (en) * 2003-10-31 2007-10-18 Mitsubishi Materials Pmg Corporation Method for Producing Composite Soft Magnetic Material Exhibiting Excellent Magnetic Characteristics, High Strength and Low Core Loss
US20080199039A1 (en) * 2007-02-15 2008-08-21 Wisdom Audio Corp. Induction motor for loudspeaker
US20100276832A1 (en) * 2005-10-11 2010-11-04 Canon Kabushiki Kaisha Composite metal molding and method for manufacturing thereof
DE102010017973A1 (en) * 2010-04-23 2011-10-27 Thomas Magnete Gmbh Transverse magnetic flux electricmotor i.e. outer runner motor, has permanent magnets provided on rotor, and two stator components made of iron metal sheet and iron powder composite material, respectively
US20230348751A1 (en) * 2020-08-28 2023-11-02 Chugoku Marine Paints, Ltd. Coating composition, coating film, substrate with coating film, and method for producing the same

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US3216074A (en) * 1964-02-26 1965-11-09 Edward N Harrison Method for making shaped foundry articles
US3414641A (en) * 1965-07-30 1968-12-03 Ibm Method of fabricating resistor compositions

Cited By (27)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5334612A (en) * 1976-09-14 1978-03-31 Komatsu Mfg Co Ltd Method of producing industrial raw material out of powder
US4810524A (en) * 1982-06-18 1989-03-07 Tdk Corporation Inorganic powders with improved dispersibility
US4601753A (en) * 1983-05-05 1986-07-22 General Electric Company Powdered iron core magnetic devices
US4601765A (en) * 1983-05-05 1986-07-22 General Electric Company Powdered iron core magnetic devices
US4675143A (en) * 1984-12-28 1987-06-23 Ube Industries, Ltd. Process for producing a shaped electroconductive thermoplastic resin composition article
JPH0831383B2 (en) 1985-03-28 1996-03-27 株式会社東芝 Large current reactor
US4977386A (en) * 1987-10-13 1990-12-11 Leda Logarithmic Electrical Devices For Automation S.R.L. Electric resistor producible in a wide range of specific resistance values, and relative manufacturing process
EP0375627A1 (en) * 1988-10-28 1990-06-27 NUOVA MERISINTER S.p.A. A process for pre-treating powders with a solid lubricant and heat in preparation for compacting operations
US5595609A (en) * 1993-04-09 1997-01-21 General Motors Corporation Annealed polymer-bonded soft magnetic body
US5567746A (en) * 1994-12-16 1996-10-22 General Motors Corporation Moldable ferromagnetic particles and method
US5629092A (en) * 1994-12-16 1997-05-13 General Motors Corporation Lubricous encapsulated ferromagnetic particles
US5637402A (en) * 1994-12-16 1997-06-10 General Motors Corporation Moldable ferromagnetic particles and method
US6635122B2 (en) * 1998-11-23 2003-10-21 Hoeganaes Corporation Methods of making and using annealable insulated metal-based powder particles
US20030077448A1 (en) * 2001-03-27 2003-04-24 Kawasaki Steel Corporation Ferromagnetic-metal-based powder, powder core using the same, and manufacturing method for ferromagnetic-metal-based powder
US6808807B2 (en) 2002-06-14 2004-10-26 General Electric Company Coated ferromagnetic particles and composite magnetic articles thereof
US20030232196A1 (en) * 2002-06-14 2003-12-18 Krishnamurthy Anand Coated ferromagnetic particles and composite magnetic articles thereof
US20050016658A1 (en) * 2003-07-24 2005-01-27 Thangavelu Asokan Composite coatings for ground wall insulation in motors, method of manufacture thereof and articles derived therefrom
US20050019558A1 (en) * 2003-07-24 2005-01-27 Amitabh Verma Coated ferromagnetic particles, method of manufacturing and composite magnetic articles derived therefrom
US20070243400A1 (en) * 2003-10-31 2007-10-18 Mitsubishi Materials Pmg Corporation Method for Producing Composite Soft Magnetic Material Exhibiting Excellent Magnetic Characteristics, High Strength and Low Core Loss
US20050142349A1 (en) * 2003-12-29 2005-06-30 Irwin Patricia C. Composite coatings for groundwall insulation, method of manufacture thereof and articles derived therefrom
US7803457B2 (en) 2003-12-29 2010-09-28 General Electric Company Composite coatings for groundwall insulation, method of manufacture thereof and articles derived therefrom
US8075838B2 (en) * 2005-10-11 2011-12-13 Canon Denshi Kabushiki Kaisha Composite metal molding and method for manufacturing thereof
US20100276832A1 (en) * 2005-10-11 2010-11-04 Canon Kabushiki Kaisha Composite metal molding and method for manufacturing thereof
US20080199039A1 (en) * 2007-02-15 2008-08-21 Wisdom Audio Corp. Induction motor for loudspeaker
US8009857B2 (en) 2007-02-15 2011-08-30 Wisdom Audio Corp. Induction motor for loudspeaker
DE102010017973A1 (en) * 2010-04-23 2011-10-27 Thomas Magnete Gmbh Transverse magnetic flux electricmotor i.e. outer runner motor, has permanent magnets provided on rotor, and two stator components made of iron metal sheet and iron powder composite material, respectively
US20230348751A1 (en) * 2020-08-28 2023-11-02 Chugoku Marine Paints, Ltd. Coating composition, coating film, substrate with coating film, and method for producing the same

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