JPH04165022A - Formation of insulating film for oriented electromagnetic steel plate excellent in iron core machinablity and anti-dusting performance - Google Patents

Abstract

PURPOSE:To form an insulating film having good lubricating property and excellent iron core machineability and anti-dusting performance by applying a coating material for which a noncolloidal solid is added to a conventional insulating film coating agent before and after imparting linear strain and then baking the coating film. CONSTITUTION:The insulating film coating material is prepared by the following procedure. Per 100 pts.wt. (in term of SiO2) colloidal silica of <=50nm particle diameter, 130-300 pts.wt. of one or more phosphates of Al, Mg, Ca and Zn, and 10-100 pts.wt. of one or more compds. selected from chromic aid anhydride, chromate and bichromate are mixed. Further to this mixture, one or more kinds of noncolloidal solid having 5-2000nm particle diameter composed of oxides, carbides, nitrides, sulfides, borides, hydroxides, silicates, carbonates, borates, nitrates or chlorides of Fe, Ca, Ba, Zn, Al, Ni, Sn, Cu, Cr, Cd, Nd, Mn, Mo, Si, Ti, W, Bi, Sr, and V are added by 0.5-25 pts.wt. to prepare the insulating film coating agent. This coating agent is applied to a steel plate before and/or after linear strain is imparted and then baked to form the insulating film.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for forming an insulating film on a grain-oriented electrical steel sheet that has excellent core workability and dust resistance.

(Prior art) A oriented electromagnetic copper plate is produced by hot rolling a silicon steel slab containing, for example, 2 to 4% St, annealing it, and then cold rolling it once or twice or more with intermediate annealing in between. The plate is made to the final thickness, then decarburized and annealed, coated with an annealing separator mainly composed of MgO, final annealed to develop secondary recrystallized grains with Goss orientation, and further impurities such as S and N are removed. While removing it, a glass film is formed, and then a coating liquid for an insulating film is applied, and a baking treatment is performed to form an insulating film to produce a product.

In addition, for the purpose of lowering iron loss, fine linear strain is applied at intervals to the surface of grain-oriented electrical steel sheets after or before final annealing to subdivide the magnetic domains ( For example, JP-A-53-137016, JP-A-56-51522).

If the linear strain is applied after the insulation film is formed, the film may be damaged, so the insulation film treatment is performed again for the purpose of rust prevention.

By the way, grain-oriented electrical steel sheets are mainly used as core materials for transformers and electrical equipment, but when manufacturing cores,
A hoop of grain-oriented electrical steel sheet slit to a predetermined width is continuously unwound and cut into a predetermined length and shape using a shearing machine, and then sequentially rolled or laminated using a core processing machine.
It is considered to be a wound core or a stacked core. In the case of wound cores, compression molding,
After strain relief annealing, a winding process called lacing is performed to create a transformer.

In the case of stacked iron cores, the cores are assembled manually and wound to form a transformer, but strain relief annealing is usually not performed.

In the manufacture of iron cores, for example, in the case of wound cores, the film must have good lubricity so that winding and forming operations can be performed smoothly, and the shape is excellent without causing unevenness on the steel plate end face or lap part after forming. In addition, in the case of stacked cores, the insulating film formed on the surface of the steel plate does not turn into dust when it comes into contact with conveyor rolls, etc. or when sheared, etc., and the film has appropriate slipperiness, making it easy to assemble the core. It is required that the process be carried out smoothly.

Furthermore, in the case of wound cores, there is no seizure between the surface films of the steel plates during strain relief annealing, and racing work can be performed smoothly, which is important from the viewpoint of improving core processing efficiency and preventing distortion caused by seizure and deterioration of film performance. It is important because These problems are greatly influenced by the properties of the insulating film of grain-oriented electrical steel sheets, so it is strongly desired to develop an insulating film with excellent properties.

As a means to improve the workability of transformer cores,
Improvements in coating agents for forming insulating films are being considered. For example, JP-A No. 61-4773 discloses ultrafine colloidal silica having a particle size of 8 μm or less as a primary phosphate as a coating agent.

A technique has been disclosed for improving the slipperiness of an insulating film by applying a mixture of one or more of chromic acid and chromate to a steel plate after finish annealing and baking it.

These improvements in insulating films have improved the iron loss, magnetostriction, and insulation properties of the grain-oriented electromagnetic copper plates, as well as the film lubricity, and have produced certain effects.

However, in grain-oriented electrical steel sheets that have been subjected to linear strain to reduce core loss and have an insulating film re-formed, in order to ensure linear strain,
It is not possible to raise the baking temperature of the insulating film sufficiently, so it is necessary to bake at a low temperature.

As a result, the film strength is insufficient, the insulation film is prone to scratches, and the film may occasionally become dusty.

Furthermore, although the magnetic properties of grain-oriented electrical steel sheets have been improved, it is important to further improve the core workability of the steel sheet insulation coating, as one of the requirements for making full use of these characteristics in manufactured transformers. be.

(Solution to be Solved by the Invention!ia) The present invention provides a grain-oriented electrical steel sheet that has been subjected to linear strain to reduce core loss. An object of the present invention is to provide a method for forming an insulating film that has good slip properties, excellent iron core workability, and does not turn into dust.

(Means for Solving the Problems) The gist of the present invention is to hot roll a silicon steel slab, annealing it if necessary, and cold rolling it once or twice or more with intermediate annealing in between. The steel plate is adjusted to the final thickness, decarburized and annealed, coated with an annealing separator, and then subjected to finish annealing. After the final annealing, an insulating film coating agent is applied to the steel plate and a baking treatment is performed to create fine linear strain on the steel plate surface at intervals. and then,
In the method of forming an insulating film by applying the insulating film coating agent again and baking it, 100 parts by weight of colloidal silica (S
ing), 130 to 300 parts by weight of one or more phosphates of AL Mg, Ca + Zn, and 10 parts by weight of one or more of chromic anhydride, chromate 1 dichromate. ~100 parts by weight, Fe+Ca,
Ba, Zn, AL Nt, Sn,
Cu+ Cr, Cd+ Nd+Mn+ Mo
, si, Ti, k, ei, Sr, V oxides, variations, nitrides, sulfides, borides, hydroxides, silicates, carbonates, borates, nitrates or chlorides, An insulating film coating agent prepared by adding 0.5 to 25 parts by weight of one or more non-colloidal solids having a particle size of 5 to 2000 nm is applied before or after applying the linear strain. A method for forming an insulating film on a grain-oriented electrical steel sheet with excellent core workability and dust resistance, characterized in that the insulating film is formed by applying the insulating film to the steel plate afterward or on both the front and the back, and baking to form an insulating film.

The present invention will be explained in detail below.

The present inventors applied linear strain to the surface of a steel sheet at intervals, applied an insulating film coating agent before and after applying the linear strain, and baked to form an insulating film. When non-colloidal solids with a diameter of 5 to 2000 nm are added, they are uniformly dispersed or small particles form aggregates, which create small rounded convexities on the formed insulating film, resulting in the formation of a double film. Combined, this results in an insulating film with extremely excellent slip properties, and a film that is hard to scratch and does not generate dust.

The present invention will be explained in detail based on experimental data.

A sample was cut out from a strip coil of grain-oriented electrical steel sheet that had been subjected to finish annealing using a known method, and then subjected to strain relief annealing for 83 hours.
After removing the coil set at 0°C for 5 hours, 2% B
! The sample was lightly pickled with 504 at 80°C for 8 seconds. As shown in Table 1, this sample was coated with an insulating film coating agent containing 234 parts by weight of M phosphate to 100 parts by weight of colloidal silica with a particle size of 10 nm. 2 parts by weight of non-colloidal SiO2 powder was added and blended, mixed with water, stirred, and applied to a steel plate as a coating liquid. After baking, it was applied to a concentration of 4.0 g/C under an N atmosphere. So 86
A baking treatment was performed at 0° C. for 30 seconds. Thereafter, fine linear strain was applied to the surface of the steel plate by laser irradiation at 10 mm intervals in the direction perpendicular to the rolling direction. After that, the insulating film coating liquid was applied again and baked at 400''C.

A sample was cut out from the obtained product board, and the sliding friction coefficient (FF value) of the insulating film was measured by the method shown in FIG. 1 (Method A). The measurement method is to hold the sample 2 between the sandwiching plates 1-1 and 1-2.
, apply a load N with the heavy bell 3, measure the force A to pull out the sample 2 with the spring scale 4, and calculate the sliding friction coefficient μ as μ(F
F) = A/N.

In addition, we repeatedly slid a steel ball under a certain load on the insulation coating, and continuously measured the resistance that the steel ball received from the insulation coating.We also investigated the occurrence of flaws in the insulation coating (lubrication gender, B method).

Furthermore, separately cut 33X4C1 samples were stacked,
Tighten this to 90kg/cm" by binding it with pressure.
Strain relief annealing was performed at 860°C for 3 hours in an atmosphere as shown in Figure 2 (
The peeling load of the steel plate was measured and the sticking property was investigated using the method shown in b). The results are shown in Table 1.

As shown in Table 1, those coated with an insulating film coating agent containing 2 parts by weight of non-colloidal SiO□ with a particle size of 20 to 1200 nm and baked have a low FF value and excellent lubricity. , there is no occurrence of defects, the dust resistance is high, and the staking resistance during strain relief annealing is also good.

Next, a method for forming an insulating film according to the present invention will be described.

The composition of the coating agent for forming an insulating film is 100 parts by weight of colloidal silica of 50 nm or less (Si (as h)) and 130 to 300 parts by weight of one or more phosphates of AIr, Mg, Ca, and Zn. and one or more of chromic anhydride, chromate, and dichromate.
It is blended in an amount of 0 to 100 parts by weight.

The colloidal silica needs to have fine particles of 50 nm or less in order to reduce iron loss and magnetostriction, and to improve the slipperiness of the film.

A7. Phosphates of Mg, Ca, and Zn have the effect of preventing stickiness of the film and improving slipperiness, and furthermore, when forming the insulating film again as the subject of the present invention, they have the effect of preventing the film from turning into dust. In order to achieve this effect, 1 part by weight of colloidal silica must be added.
30 parts by weight or more is required.

On the other hand, if the amount is too large, the coating becomes soft and scratches are likely to occur on the coating, so the amount should be 300 parts by weight or less. Also, A
The phosphates of Ir ng, Ca, and Zn are selectively blended, and one or more of them are blended.

One or more of chromic anhydride, chromate, and dichromate are blended to stabilize film formation, but if this amount is less than 10 parts by weight, the film will become sticky.
It needs to be 10 parts by weight or more. On the other hand, if this amount is too large, free chromic acid becomes excessive and the coating becomes sticky even when recoating and forming a film at a low temperature, so the amount should be 100 parts by weight or less.

Pe+ Ca, Ba, Zn+ AIr Nil S
n, Cu+Cr, cd, Nd+Mn, ? 'l
OI Sll Tll 'li+ Bt, Sr, V oxide, carbide, nitride, sulfide, boride, hydroxide,
Non-colloidal solids of silicates, carbonates, borates, nitrates or chlorides are incorporated. The solid substance has a particle size of 5n- or more in order to form fine convex spheres dispersed on the surface of the coating to improve slipperiness and to prevent the coating from turning into dust. On the other hand, as the particle size increases, the space factor of the film decreases, so the particle size is set to 2000 nm or less. When the particle size is about 5 to 1100 nm, the solids aggregate to form the convex spherical shape on the surface of the film.

In addition, if the amount of the non-colloidal solid is small, the effect of improving slipperiness cannot be obtained, and in order to avoid this and improve slipperiness, colloidal silica
It is necessary to add 0.5 parts by weight or more to 00 parts by weight. On the other hand, if the amount increases, the space factor of the film decreases, so the upper limit is set at 25 parts by weight.

The insulating film coating agent having the above composition is in the form of an aqueous solution, and is applied to the steel plate and baked to form an insulating film, but before it is applied to the steel plate to form linear strain that subdivides the magnetic domains and reduces iron loss. It is used to form an insulating film on either side later. Further, similar effects can be obtained by applying the insulating film coating agent according to the present invention both before and after applying linear strain.

Next, examples will be described.

(Example 1) C: 0.083%, Si: 3.23%, Mn in weight%
: 0.068%, S: 0.024%, sol,
A silicon steel slab consisting of Al: 0.029%, the balance being iron and unavoidable impurities was hot rolled by a known method, annealed and then cold rolled to a final thickness of 0.220%, followed by decarburization annealing. After applying an annealing separator, final annealing was performed at 1200° C. for 20 hours to form a glass film. Next, excess annealing separation agent was removed by water washing, and after light pickling, an insulating coating agent with adjusted particle size and phosphate of colloidal silica as shown in Table 2 was added to a weight of 4.5 g after baking. /s" and baked at 850°C for 30 seconds in a N atmosphere. Thereafter, linear strain was applied to the steel plate at intervals of 10 cm in the direction perpendicular to the rolling axis by laser irradiation. After that, ,
An insulating film coating agent having the composition shown in floor 11 of Table 2 was applied by a known method to a total weight of 4.5 g/m'' after baking, and then baked at 400°C for 30 seconds in a N! atmosphere. processed.

Samples were cut out from the obtained steel plate, and the FF value, lubricity,
The presence or absence of flaws and staining resistance were investigated. The results are shown in Table 2.

Table 2 [*: Present invention, **: (Method A)] (Example 2) C: 0.083%, Si: 3.23%, Mn in weight%
: 0.068%, S: 0.024%, sol,
A silicon steel slab consisting of Al: 0.029%, the balance being iron and unavoidable impurities was hot rolled by a known method, annealed and then cold rolled to a final thickness of 0.220%, followed by decarburization annealing. After applying the annealing separator, final annealing was performed at 1200° C. for 20 hours to form a glass film.Then, the excess annealing separator was removed by water washing, and after light pickling, the annealing method shown in Table 3 was performed using a known method. An insulating film coating agent having the composition shown in Koji 10 was applied so that the weight after baking was 4.0 g/ys", and baking treatment was performed at 850°C for 30 seconds in a N! atmosphere. Thereafter, laser irradiation was performed. Linear strain is applied to the steel plate at intervals of 10 wheels in the direction perpendicular to the rolling axis, and an insulating film coating agent with the particle size of colloidal silica and phosphate adjusted as shown in Table 3 is applied to the steel plate by a total weight of 4 .5g
/s'', and then baked at 400° C. for 30 seconds in an N2 atmosphere.

Samples were cut out from the obtained steel plate, and the FF value, lubricity,
The presence or absence of flaws and staining resistance were investigated. The results are shown in Table 3.

Table 3 (*-Invention, **: (Method A)) (Effects of the invention) According to the invention, the steel plate has good slip properties and heat resistance, and the coating surface is less prone to scratches and has dust resistance. It is possible to obtain a grain-oriented electrical steel sheet having an insulating coating that is excellent in processability of iron cores in transformer manufacturing.

[Brief explanation of the drawing]

Figure 1 shows a means for measuring the sliding friction coefficient of an insulating film (A
Figures 2(a) and 2(a) are diagrams showing a method for investigating the sticking property during strain relief annealing after processing an electrical steel sheet into an iron core. A diagram showing the laminated state of a strain-relieving annealed sample during the sticking property investigation, and (c) a diagram showing an aspect when measuring the interlayer seizure state after the strain-relieving annealing is completed. Figure 1(b)

Claims (1)

[Claims] A silicon steel slab is hot-rolled, annealed if necessary, cold-rolled once or twice or more with intermediate annealing in between to achieve the final thickness, decarburized annealed, and annealed and separated. After applying the agent, finish annealing is performed, and after the final annealing, an insulating film coating agent is applied to the steel plate and baking treatment is performed to impart fine linear strain to the steel plate surface at intervals, and then the insulating film coating is applied again. In the method of forming an insulating film by applying a baking agent, 100 parts by weight of colloidal silica (S
iO_2), 130 to 300 parts by weight of one or more phosphates of Al, Mg, Ca, and Zn;
10 to 100 parts by weight of one or more of chromic anhydride, chromate, dichromate, and Fe, Ca, Ba,
Zn, Al, Ni, Sn, Cu, Cr, Cd, Nd, M
oxides of n, Mo, Si, Ti, W, Bi, Sr, V,
carbides, nitrides, sulfides, borides, hydroxides, silicates,
Insulation made by adding 0.5 to 25 parts by weight of one or more types of non-colloidal solids such as carbonates, borates, nitrates, or chlorides with a particle size of 5 to 2000 nm. A grain-oriented electrical steel sheet with excellent core workability and dust resistance, characterized in that a film coating agent is applied to the steel sheet before or after applying the linear strain, or both before and after the linear strain is applied to form an insulating film by baking. Insulating film forming method.