JPH0256020B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a sheet-shaped steel member coated with an insulating phosphate. Magnetic cores used in generators, transformers, electric motors, etc. are preferably formed by laminated sheet-like stamped steel members with an insulating coating on each sheet. As is well known, this type of core is constructed from laminated material rather than solid steel to minimize undesirable swirling currents. Aluminum orthophosphate, also referred to as aluminum phosphate, is used in diluted form as an inorganic coating material to produce an interlayer insulation medium on stamped parts of iron sheets and strips. Aluminum phosphate is used to insulate between layers of laminated cores in motors, generators, transformers, etc., and to minimize eddy currents in these types of equipment. The paint solution before dilution consists of a mixture of phosphoric acid and alumina hydrate, approximately 33% by weight P ₂ O ₅ and 8% by weight
of Al ₂ O ₃ and 59% by weight of H ₂ O. This type of paint solution is, for example, "Alkofos"
It is commercially available under the trade name Alkophos and is widely used in the electrical equipment industry and applied to electrical steel by equipment manufacturers or electrical steel suppliers. The phosphate-aluminum solutions described above are usually further diluted with water prior to use. The suitable concentration for use depends on the desired resistivity and thickness and the applicator used to apply the coating, but is generally 0.5 to 4 parts by volume of the phosphate-aluminum solution to water.
Concentration is the sum of parts by volume. After applying this solution to the steel using a felt or rubberized roll applicator,
Cure vertically in the oven. This type of phosphate coating is well known in the art and is primarily used to coat hot rolled steel, as disclosed in U.S. Pat. No. 2,743,203 to Steinherz. , steel sheet temperature 135
Cure at temperatures between 500°C and 500°C to heat away the water and leave behind a thin phosphate coating that reacts with the ferrous metal surface of the sheet. The coating film thus obtained has a high insulation value and good surface properties. This coating has been shown to have the ability to resist various mechanical, thermal and chemical attacks encountered in electrical equipment or manufacturing processes. However, in current practice, where cold-rolled steel with a low reactivity surface is typically used, the temperature required for commercially available sheet steel to cure unmodified phosphate coatings is approximately 340°C. . To achieve the above temperatures for the sheet steel and the same temperature for the phosphate coating, temperatures are usually much higher than the above temperatures, depending on the furnace design, conveyor speed and layer thickness. , normally the temperature should be set between 425℃ and 650℃. These high curing temperatures result in high process costs due to the expensive natural gas or electricity used in the oven, and high labor costs due to slow application speeds when using non-denaturing materials. In addition to higher equipment maintenance costs, problems arise, such as increased heat returning to the coating roll and the risk of insufficient curing. Accordingly, there has long been a need for new coatings or improved coating methods that are simple, inexpensive, and yet provide interlayer coating, insulation, and space factor properties comparable to prior art coatings or coating methods. It was felt. Therefore, the present invention provides an aluminum phosphate aqueous solution.
This invention relates to a member made of ferrous sheet steel whose surface is coated with a hardened insulating phosphate coating obtained from an aqueous solution consisting of 100 parts by volume and 15 parts by volume of nitric acid. The phosphate coating used in the present invention preferably contains 0.5 to 4 parts by volume of phosphate-aluminum aqueous solution.
A solution containing part by volume of diluted water and diluted phosphoric acid.
3-12% by volume based on the volume of aluminum liquid
of nitric acid and a dilute phosphate solution. Surprisingly, by adding nitric acid as described above, the commercially available sheet necessary for curing phosphate coatings can be cured while retaining the coating properties, insulation properties and space factor properties of unmodified phosphate coatings. The temperature of the steel can be lowered by approximately 90℃. The ability to lower curing temperatures has the added benefit of reducing handling problems and reducing the amount of energy required. A variety of ferrous metal sheets can be treated according to the present invention. Silicon-iron sheets with a silicon content of up to 7% can be treated according to the invention. It is also possible to process nickel-iron magnetic sheets with a nickel content of up to 85%. Other magnetic sheets with high iron content and alloyed with one or more other metals can also be processed. in general,
Sheets of this type are continuously cold rolled. As used herein, the term "ferrous sheet steel" is intended to include all such materials. The cured phosphate coating according to the present invention comprises a diluted aqueous aluminum phosphate solution and 1 to 15% by volume, preferably 3 to 12% by volume, most preferably 3 to 8% by volume, based on the volume of the diluted aqueous aluminum phosphate solution. obtained from a mixture of _HNO3 . HNO ₃ is 1
If it is less than % by volume, no improvement in curing will be achieved.
If HNO ₃ exceeds 15% by volume, the coating solution becomes excessively corrosive. A dilute aqueous solution of aluminum orthophosphate contains 100 parts by volume of an aqueous aluminum phosphate solution. This aluminum phosphate composition is typically a mixture of phosphoric acid and alumina hydrate as the active ingredient.
It can be expressed as having P ₂ O ₅ and Al ₂ O ₃ . The aluminum phosphate composition contains 28-38% by weight, preferably 30-35% by weight of _P2O5 and 5-12% by weight of _P2O5 .
% by weight, preferably 7-10% by weight of Al ₂ O ₃ and 50
~70% water by weight, preferably 50-400 parts by volume,
Most preferably from 100 to 250 parts by volume of additional dilution water. If water is added for dilution or if the amount is less than 50 parts by volume, it will be difficult to apply the coating uniformly to electrical steel. If the amount of dilution water added exceeds 400 parts by volume, the film thickness will become too thin and the insulation performance will deteriorate. Therefore, the aqueous solution of the phosphoric acid-aluminum composition has a total solids content of P ₂ O ₅ and Al ₂ O ₃ of 33 to
55% and does not contain other substances such as zinc, zinc phosphate and nickel. However, the formula

An effective amount, usually up to 1.5% by volume, of a nonionic steel wetting agent consisting of a substance containing an alkyl group of an appropriate chain length bonded to a group represented by the formula (R is a water-soluble group) is preferably used. can also be used at 0.5 to 1.2% by volume. If the amount of wetting agent is less than 0.5% by volume, it will not be possible to wet the steel and deposit the phosphate coating. The typical composition of nitric acid modified low temperature phosphate paints is:
_{P2O5 33wt} %, _{Al2O3 8.6wt} % and _H2O58.4wt %
10 liters of an aluminum phosphate solution consisting of;
It consists of 20 liters of H ₂ O for additional dilution, about 0.3 liters of nonionic wetting agent, and 1.5 liters of HNO ₃ , or about 5% by volume of HNO ₃ based on the above component composition. The term "nitric acid" as specified herein is _HNO3 at a concentration of 65% or greater, ie, 69-71% of _the reagent equivalent. The nitric acid-modified phosphate coating compositions of the present invention are typically applied to various types of cold rolled electrical steel by roll coating techniques utilizing grooved rubber or felt applicator rolls. After applying this composition to the surface of the substrate sheet steel, heating the sheet steel and phosphate coating to a sheet steel temperature of about 90°C to about 130°C for a sufficient period of time to drive off most of the water will remove the applied coating. The film cures and adheres to the substrate and becomes integral. When the sheet layers are stacked and used in an electromagnetic device, the deposited coating provides good interlayer resistance to the substrate and improves eddy current losses. Nitric acid modified phosphate coatings can also be used in the form of multi-layer coatings and can be overcoated over other basecoat phosphate coatings.
Here, "sheet steel temperature" means the temperature of the steel and coating as measured by a thermocouple or the like, and not the temperature of the oven, which is usually much higher. The cured density of the nitric acid-modified phosphate coating of the present invention is about 1-1.5 g/cm ³ . After curing, the coating film is
According to the Franklin test specified in ASTM standard A-717, at least 2ohm・cm ² /1am,
It shows a high resistance value of 640ohm・cm ² /1am. As used herein, the term "cured" means that the phosphate coating has become a non-tacky solid.
It is thought that HNO ₃ increases the activity of the iron surface during curing, accelerates the reaction between the iron-containing sheet steel and the paint film, generates iron phosphate, etc., and causes the deposition of aluminum phosphate. Next, the present invention will be explained with reference to Examples. Example 33.1% by weight of P ₂ O ₅ and 8.6% by weight of Al ₂ O ₃ ;
It consists of 58.4% by weight of H ₂ O and has a viscosity at 25°C of approx.
40 centipoise, specific gravity is 1.47 and molecular weight is approx.
A phosphoric acid-aluminum solution of 318 (trade name Alkophos C) was manufactured by Monsanto Chemical Corporation.
Co., Ltd.], 20 parts by volume of _H2O for addition dilution, and 5% by volume of 71% concentrated _HNO3 , i.e.
A nitric acid modified phosphate coating composition was prepared consisting of a mixture with 0.05 x 30 parts by volume = 1.5 parts by volume of _HNO3 . In preparing the above composition, the acid was the last component and mixed at 25°C. Approximately 1% by volume of a nonionic phosphorus-containing medium chain length alkyl group wetting agent (available from Victor Chemical Co. under the trade name Victawet #12).
Co., Ltd.] was added to the phosphate coating composition. For comparison, an unmodified phosphate coating composition was created, but containing the same components in the same amounts, except that HNO ₃ was removed. Both coating compositions were roll coated onto cold rolled electrical steel, heated and cured, and then the insulation properties were measured. Both compositions were also applied to armature stamped parts and tested for interlayer resistance. The results are shown in Tables 1 and 2.

[Table] *Note: Comparative sample

[Table] *Note: Comparative sample As can be seen from the table, the insulation properties and space factor properties of the HNO ₃ modified phosphate coating maintain the original values, and the curing temperature is the same as that of the standard non-modified phosphate coating. This is approximately 250°C lower than the curing temperature of the film.

Claims (1)

[Scope of Claims] 1. A ferrous sheet steel member coated with a hardened insulating phosphate coating, the coating comprising 100 parts by volume of aqueous aluminum phosphate and 1 to 15 parts by volume of nitric acid. A member characterized in that it is a coating film formed from an aqueous solution. 2. The member according to claim 1, wherein the aqueous aluminum phosphate is a mixture of phosphoric acid, hydrated aluminum, and water. 3. The member according to claim 1 or 2, wherein 3 to 8 parts by volume of nitric acid is used. 4 Aqueous aluminum phosphate is 28-38% by weight
_{P2O5 ,} 5-12 wt% _{Al2O3 ,} 50-70 wt%
The member according to claim 1, 2 or 3, characterized in that the member is made of water. 5 Aqueous aluminum phosphate is 30-35% by weight
The member according to claim 4, characterized in that it contains _P2O5 and 7 to ₁₀ % by weight _{of Al2O3} . 6. Claim 6, characterized in that the aqueous solution contains 50 to 400 parts by volume of additional dilution water and 3 to 12% by volume of nitric acid, based on the total volume of aqueous aluminum phosphate and additional dilution water. The member according to any one of Items 1 to 5. 7. The member according to claim 6, characterized in that 3 to 8% by volume of nitric acid is used. 8. A component according to claim 6 or 7, characterized in that the aqueous solution contains at most 1.5% by volume of wetting agent. 9 Claims 6, 7, or 8, characterized in that 100 to 250 parts by volume of dilution water are used.
Components listed in section.