JP2637405B2 - Rust-proof electrical steel sheet with insulating coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a rust-preventive magnetic steel sheet having a steel sheet surface coated with an inorganic insulating film in order to improve the properties of a magnetic steel sheet that does not rust among oriented magnetic steel sheets. It is about.

(Prior Art) Electric devices such as transformers and electric motors have been required to have higher characteristics due to the recent development of the electric industry. By the way, the silicon steel sheet used as the above-mentioned iron core has a problem as described below because it is very easy to rust.

That is, the conventional silicon steel sheet has a disadvantage that the cut fracture surface is very easily rusted, and if rusted, the magnetic permeability deteriorates. Particularly recently, from the viewpoint of improving the efficiency of the motor, the gap between the stator and the rotor has become extremely small.However, if the laminated end face of the rotor and the stator rusts at this time, the gap is clogged, Due to the decrease in the magnetic permeability, the performance further deteriorated. As a solution to the above problem, it is conceivable to apply paint to the end face of the gap. However, when such a measure is taken, the gap could not be substantially reduced due to the paint application thickness.

In addition, rust prevention is also required for magnetic materials for submersible pumps and solenoid valves.

To meet such demands, Japanese Patent Publication No. 39-2064
No. 4 proposed a stainless steel electromagnetic steel sheet having excellent corrosion resistance, which is mainly composed of Cr and contains a small amount of a magnetic property improving element such as Si or Ti.

(Problems to be Solved by the Invention) However, the above-mentioned stainless steel-based electromagnetic steel sheet has an extremely low electrical resistivity as compared with a silicon steel sheet, and when used as a laminated core, the interlayer resistance of the steel sheet becomes equal to zero. There remains a problem that iron loss on actual equipment deteriorates.

As a solution to such a problem, it is conceivable to cover the surface of the steel sheet with an insulating coating. However, simply forming an insulating coating cannot avoid deterioration of magnetic properties, particularly iron loss properties.

The present invention advantageously solves the above-described problems, and has as its object to propose a rust-preventive electromagnetic steel sheet having improved electrical insulation properties without deteriorating magnetic properties.

(Means for Solving the Problems) According to the present invention, the surface roughness is 0.5 to 1.0 as a center line average roughness Ra.
This is a rust-preventive electromagnetic steel sheet having an insulating coating formed by providing a chromate-based or phosphate-based inorganic insulating coating on the surface of a μm-oriented Fe-Cr-based electromagnetic steel sheet.

The Fe-Cr-based magnetic steel sheet, which is a substrate of the steel sheet of the present invention, contains 13 to 20% by weight of Cr (hereinafter simply referred to as%) as an alloy component, and further contains 8 to 20% of Cr:
Al and Si up to 4% and P, Sn, Ti, V, M up to 3%
Those having a composition containing at least one selected from o, W, Zr, Nb, Hf and Ta are particularly advantageously suited.

Here, the reason why the preferable content of the alloy component is limited to the above range is as follows. In other words, Cr as the main component that should provide the expected improvement in corrosion resistance and electromagnetic properties
In general, when the amount is less than 8%, the corrosion resistance cannot be sufficiently improved, and when it exceeds 20%, it becomes uneconomical.

As already known, Cr forms a γ loop with Fe, but when the content of Cr is 13% or more of the above 8 to 20%, Cr does not form a γ phase and exists only as an α phase. Is less than 13%, a γ phase is generated. Therefore, the lower limit when only Cr is added is preferably 13%.

As described above, when the Cr content is less than 13%, it is necessary to reduce the ratio of the γ phase to stabilize the α phase.
By containing at least one α-phase stabilizing component selected from the group consisting of P, Sn, Ti, V, Mo, W, Zr, Nb, Hf, Ta
By expanding the Cr content range to 8 to 20%, the Fe-Cr-based α-phase stable composition can be obtained together with the case of Cr 13 to 20%. here
Al, Si and P, Sn, Ti, V, Mo, W, Zr, Nb, Hf and Ta have a Cr content of 8 to 20%, particularly 8 to 13%, in the above content range.
It is the same component that contributes to stabilization of α phase in Fe. The upper limit is set to 20% because the magnetic moment is significantly reduced and the magnetism is deteriorated when Cr is added in an amount of 20% or more.

Al, Si and P, Sn, Ti, V, Mo, W, Zr, Nb, Hf, Ta are less effective if less than 0.5%, respectively, while 4.0% Al, Si
If P, Sn, Ti, V, Mo, W, Zr, Nb, Hf, and Ta are contained in large amounts exceeding 3.0%, magnetic properties, workability and corrosion resistance are disadvantageously impaired.

(Operation) Hereinafter, a method for producing the steel sheet of the present invention will be described.

Now, the alloy slab adjusted to a suitable component composition is subjected to hot rolling and then cold rolling to obtain a cold-rolled sheet having a final thickness. In the present invention, the surface roughness of such a cold-rolled sheet is determined by the center line average roughness.
It is important that the Ra be 1.0 μm or less.

FIG. 1 shows that an alloy slab having a composition of Cr ₁₃ Al ₂ Si ₁ -Fe is heated to form a 30 mm-thick sheet bar, and then hot-rolled to form a 2.0-mm-thick hot roll. mm
The relationship between the surface roughness of a steel sheet and its magnetic properties when the cold-rolled sheet is cold-rolled to a thickness and the roughness of the cold-rolled sheet surface is adjusted to various roughnesses by chemical polishing and pickling. The result of examining is shown.

As is clear from the figure, when the surface of the steel sheet has a center line average roughness Ra of more than 1.0 μm, a sharp deterioration in iron loss yieldability is caused.

Therefore, in the present invention, the surface roughness of the base steel sheet is limited to a centerline average roughness Ra of 1.0 μm or less.

As a method for adjusting the surface roughness, in addition to the above-described chemical treatment methods, surface roughness processing of a work roll during cold rolling, paper polishing, and the like are advantageously adapted.

FIG. 1 also shows the results of a survey on the relationship between the roughness of the plate surface and the adhesion of the insulating film.
If the surface roughness is too small, the coating adhesion tends to deteriorate, so the lower limit of Ra was set to 0.5 μm.

Subsequently, a chromate-based or phosphate-based inorganic insulating film is formed on the steel sheet subjected to the surface smoothing treatment as described above.

Typical treatment liquids for forming such an insulating film are: chromate-based: magnesium chromate and colloidal silica with boric acid added thereto; phosphate-based: phosphoric acid A solution obtained by adding aluminum nitrate, chromic acid, or the like to a solution of magnesium and colloidal silica, etc., is particularly suitable.

If the thickness of the insulating film is less than 0.05 μm, there is a disadvantage that the insulating property of the film becomes insufficient, while 5.0 μm
If the thickness exceeds the above range, there is a disadvantage that the adhesiveness is deteriorated.

(Example) Example 1 Cr: 17.5% and Si: 1.0%, the balance being substantially Fe
The alloy slab having the following composition is subjected to hot rolling and then cold rolling to obtain a final sheet thickness: a cold-rolled sheet having a thickness of 0.35 mm.The surface is then immersed in aqua regia for 20 seconds, and the center line average roughness is Ra. Finished to a smooth surface of 0.6 μm.

After annealing at 1150 ° C. for 10 minutes, an aqueous treatment solution containing magnesium phosphate: 35% and colloidal silica: 20% was applied at a rate of 2.0 g / m ² at 750 ° C.
By baking for 2 seconds, a phosphate-based inorganic insulating film having a thickness of 1.00 μm was formed.

The rust-proof electrical steel sheet with the insulating coating obtained in this way is
After cutting into strips according to the Epstein method, 30 sheets were piled up, and when various surface loads shown in Table 1 were applied, the iron loss W _10/50 at a frequency of 50 Hz and a magnetic flux density of _{10 kG} was measured.

Table 1 shows the obtained measured values. Table 1 also shows, for comparison, the measurement results for those having no insulating film on the surface.

As is clear from the results shown in Table 1, the iron loss characteristics of the comparative example were significantly deteriorated as the surface load increased, whereas the iron loss characteristics of the steel sheet of the present invention hardly deteriorated even when the surface load increased. Did not.

(Effects of the Invention) Thus, according to the present invention, it is possible to obtain a rust-preventive electromagnetic steel sheet having not only corrosion resistance but also excellent magnetic properties and coating adhesion.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the surface roughness of a Cr—Fe-based magnetic steel sheet, iron loss and film adhesion.

Continuation of front page (56) References JP-A-59-104481 (JP, A) JP-A-61-183480 (JP, A) JP-A-61-183481 (JP, A) JP-A-54-134043 (JP, A) JP-A-62-182250 (JP, A) JP-A-63-93843 (JP, A) JP-A-63-45350 (JP, A) JP-A-62-196358 (JP, A) 60-5852 (JP, A) JP-B 51-1646 (JP, B2)

Claims (3)

(57) [Claims] The surface roughness is 0.5 to 1.0 μm in center line average roughness Ra.
A rust-preventive electromagnetic steel sheet having an insulating coating, comprising a chromate-based or phosphate-based inorganic insulating coating on the surface of a m-oriented Fe-Cr-based electrical steel sheet. 2. The rust-preventive magnetic steel sheet according to claim 1, wherein the Fe-Cr-based magnetic steel sheet contains 13 to 20% by weight of Cr as a main component. 3. The Fe—Cr-based magnetic steel sheet contains 8 to 20% by weight of Cr as a main component and 4% by weight or less of Al and Si and 3% by weight.
2. The rust-proof magnetic steel sheet according to claim 1, wherein the steel sheet contains at least one selected from the group consisting of P, Sn, Ti, V, Mo, W, Zr, Nb, Hf, and Ta at wt% or less.