JP5228364B2 - Oriented electrical steel sheet - Google Patents

Description

The present invention is free of Cr, about the directional electromagnetic steel plate with a coating having excellent seizure resistance.

  Oriented electrical steel sheets have a crystal structure with (110) [001] as the main orientation and are frequently used as magnetic iron core materials. In particular, in order to reduce energy loss, a material with low iron loss is required. It has been. In response to such a request, it is known that an iron alloy containing iron and silicon is subjected to subdivision of magnetic domains when external tension is applied, and eddy current loss, which is a main element of iron loss, is reduced.

  Generally, in order to reduce the iron loss of grain-oriented electrical steel sheets containing 5% or less of silicon, it is effective to apply tension to the steel sheet, and this tension is usually applied by a coating formed on the surface. The

Conventionally, grain oriented electrical steel sheets are mainly composed of forsterite-based primary coatings, colloidal silica and phosphates, which are formed by the reaction of oxides on the steel sheet surface and the annealing separator in the final annealing process. The tension of about 1.0 kgf / mm ^{2 is applied} by the two-layer coating of the secondary coating generated by baking the coating liquid to be 0.23 mm.

  Such a coating is required to have various functions such as rust resistance, water resistance, slipperiness during processing, and seizure resistance during strain relief annealing as well as a tension imparting effect.

  Since the film composed only of phosphate and silica has a problem in seizure resistance and the like, the conventional technique solves the above problem by adding a Cr compound to the film as disclosed in Patent Document 1. Was. In this method, chromic acid is added to the coating solution, and during baking, all Cr is reduced to trivalent, and a compound with phosphorus is formed, thereby detoxifying the components in the film that adversely affect the seizure resistance. Is the method.

  The method of forming a film containing Cr is a technology that can realize excellent film characteristics by using trivalent Cr with less environmental load, but as a current technical trend, it is handled in the manufacturing process. Tensile coatings that do not use chromic acid requiring attention have been developed. For example, Patent Document 2 discloses a coating mainly composed of aluminum borate. However, the problem is that this film is inferior in water resistance. Patent Document 3 discloses a TiN coating technique, but there is a problem in cost due to the dry coating technique.

JP 48-39338 A JP-A-6-67574 JP 61-235514 A

  An object of this invention is to provide the grain-oriented electrical steel sheet which is excellent in seizure resistance, and has the coating film which does not contain Cr in the outermost surface, and its manufacturing method.

  According to the present invention, a tensile film containing phosphate and silica as constituent components includes a film containing at least any one compound of Ti, Zr, and Hf. This coating is obtained by applying a raw material liquid containing a compound of Ti, Zr and / or Hf, phosphate and silica onto a directional electrical steel sheet which has been subjected to finish annealing, and then drying and baking. It is what

  The gist of the present invention is as follows.

(1) the steel sheet outermost surface, Al, Mg, Ni, Mn , Co, Mo, Zr, phosphate containing at least one or more kinds of Sr, in addition to silica, a Hf oxide, in terms of metal element, the coating amount A grain-oriented electrical steel sheet having a Cr-free coating containing 3 to 10% by mass on the outermost surface .

The grain-oriented electrical steel sheet of the present invention has a coating containing phosphate and silica as main components and containing at least one or more of Ti compounds and Hf compounds as essential components. Therefore, the grain-oriented electrical steel sheet according to the present invention is a grain-oriented electrical steel sheet having good magnetic properties because it has a film excellent in various properties such as seizure resistance without containing Cr.

  The method for forming a film in the present invention is not particularly limited to a specific method, but the simplest method is to prepare a coating solution, apply and dry it, and then bake it. Moreover, in this invention, although the phosphate in a film can generally be used irrespective of the kind, it is 1 type or 2 types or more in Al, Mg, Ni, Mn, Co, Mo, Zr, Sr. If a phosphate containing a metal is selected, a particularly good coating such as smoothness can be obtained.

  When the phosphate is prepared as a solution, it becomes easy to prepare a coating solution. As the silica in the coating, a method using colloidal silica as a raw material is simple and highly effective.

The film, Ti compounds, the inclusion of one or two of Hf compounds, can improve the seizure resistance of the coating. The effect of the Ti compound and the Hf compound is particularly great when the content of Ti and Hf metal elements is 3% by mass or more of the coating amount in total. On the other hand, if the content is too large, film adhesion, rust resistance, and film tension are lowered, so the total content is preferably 10% by mass or less.

The Ti or Hf source, in particular, although the form thereof is not limited, in the case of preparing a coating solution, uniformly dispersed, and, in the case of baking the coating in a form without generating impurities is desirable.

  Therefore, it is preferable to use a compound that easily forms a water-soluble salt, a stable suspension or a colloid. As such a form, oxides can be used most easily, but including oxides, hydroxides, carbonates, silicates, nitrates or organic acid salts may be used alone or in combination. It doesn't matter.

  For example, for Ti, carbide TiC, nitride TiN, or alkoxide can be used as a Ti source. Examples of salts include titanium nitrate, titanium sulfate, and titanium chloride.

  In the case of a water-soluble salt, when a small amount is added, the uniformity of the coating solution is high and a high effect is easily obtained. However, when the amount added is increased, the film properties may be deteriorated. In such a case, mixing with a compound that easily forms a colloid is particularly effective.

  As for the solid content ratio of such a coating liquid, if it is low, the amount of water is too much, and a load on the process is applied at the time of drying, and if it is too high, the stability of the raw material liquid is impaired. There is a region and good results are obtained at 5-10% by weight.

In the present invention, in addition to phosphate and silica, at least one metal element of Ti 2 and Hf is an essential component of the coating film, but other components may be mixed in addition to this, even if other components are mixed. Absent. These components may be inevitably mixed from other components in the film, impurities, or the like, or may be intentionally added to the coating solution. Moreover, it does not ask | require whether the form of the structure which these components comprise is glassy or crystalline.

  When applying to a steel plate, the simplest method is to prepare a coating solution by dissolving or dispersing the aforementioned raw materials in the solution. The dispersion medium is most preferably water, but an organic solvent or a mixture thereof can be used if there is no particular problem in other steps.

  If the coating of the grain-oriented electrical steel sheet according to the present invention is too thick, the space factor decreases, so that it should be as thin as possible depending on the purpose, and the thickness is preferably 5% or less with respect to the steel sheet thickness. More preferably, it is 2% or less. Further, from the viewpoint of imparting tension, a sufficient effect cannot be obtained if the thickness is extremely thin, so the lower limit is preferably 0.1 μm.

  The obtained coating solution is applied to the surface of the grain-oriented electrical steel sheet that has been subjected to finish annealing by a conventionally known method such as a coater such as a roll coater, dipping method, spray spraying, or electrophoresis.

  The steel sheet that has been subjected to finish annealing here is (1) a steel sheet that has been subjected to finish annealing by a conventionally known method to form a forsterite primary coating on the surface, and (2) a primary coating and incidentally. A steel plate obtained by immersing and removing the generated internal oxide layer in acid, (3) a steel plate obtained by performing planarization annealing in hydrogen on the steel plate obtained in (2) above, or polishing such as chemical polishing electropolishing (4) Conditions for preventing the formation of a primary coating by applying a conventionally known annealing separator to which a small amount of an additive such as an alumina powder or a chloride which is inactive with respect to coating formation is added. Below, it refers to a steel plate that has been annealed.

  After apply | coating a coating liquid, a steel plate is dried, and an oxide film is formed in the steel plate surface by baking at 800-1000 degreeC after that. The atmosphere during baking is preferably an inert gas atmosphere such as nitrogen or a reducing atmosphere such as a nitrogen-hydrogen mixed atmosphere, and an atmosphere containing air or oxygen is not preferable because it may oxidize the steel sheet.

  There is no particular limitation on the dew point of the atmospheric gas. When the baking temperature is less than 800 ° C., there is a case where the solid content in the coating solution is not sufficiently densified, and since the baking temperature is low, there is a case where sufficient tension may not be exhibited. On the other hand, when the baking temperature exceeds 1000 ° C., the coating film is not preferable because it is not economical although there is no particular inconvenience.

  Hereinafter, the present invention will be described based on examples, but the present invention is not limited to such examples.

Example 1
When the additive is an oxide As shown in Table 1, a coating liquid comprising aluminum biphosphate having a solid content of 50%, colloidal silica having a solid content of 30%, and an additive was prepared. The mixing ratio of aluminum biphosphate and colloidal silica was set to 1: 1 by volume ratio. Such a coating solution is applied to a grain oriented electrical steel sheet (with a forsterite primary coating) having a thickness of 0.23 mm containing 3.2% by mass of Si and having a forsterite primary coating weight of 4 g / It was applied to m ² , dried, and baked at 850 ° C. for 30 seconds in an atmosphere containing 3% hydrogen to form an oxide film on the surface.

  Table 2 shows the measurement results of various properties of the coating. The adhesion was evaluated by wrapping around a cylinder having a diameter of 20 mm so that the angle was 180 degrees, and evaluating the peeled state.

For annealing resistance, a plurality of steel plates are overlapped, the four corners are tightened with a jig, and this is annealed in nitrogen at 850 ° C. for 4 hours with a dew point of 10 ° C., and then the peeling force is measured with a spring scale. The peel force was used as an index of annealing resistance. The smaller the peel force, the better the annealing resistance. From Table 2, an anneal resistance are Ti compound monomer other is improved when the addition of Hf compounds, in particular, that the addition amount in the case of 5 to 10 wt%, a large improvement is obtained I understand.

  Corrosion resistance was evaluated by holding the steel sheet in a finish annealing atmosphere at 50 ° C. and 91% for one week, and increasing the mass at that time and visually observing the surface state. Table 2 shows the tension applied to the steel sheet and the magnetic properties calculated from the bending of the sheet after removing the coating on one side. From the results in Table 2, it can be seen that in the examples within the range defined by the present invention, a grain-oriented electrical steel sheet having a good coating and low iron loss is obtained.

(Example 2)
Additives other than oxides As shown in Table 3, a coating liquid comprising aluminum biphosphate having a solid content of 50%, colloidal silica having a solid content of 30%, and additives was prepared. The mixing ratio of aluminum biphosphate and colloidal silica was set to 1: 1 by volume ratio. When the additives were mixed, the amount of addition was adjusted so that the amount of Ti contained in both additives was 1: 1.

Such a coating solution is applied to a grain-oriented electrical steel sheet (with a forsterite primary coating) having a thickness of 0.23 mm and containing 3.2% by mass of Si. It was applied to m ² , dried, and baked at 850 ° C. for 30 seconds in an atmosphere containing 3% hydrogen to form an oxide film on the surface.

  Table 4 shows the measurement results of various properties of the coating. In the adhesion test, the test was performed by winding the cylinder around a 20 mmφ cylinder so that the angle was 180 degrees, and the adhesion was evaluated from the peeled state. The annealing resistance was evaluated in the same manner as in Example 1.

From Table 4, the annealing resistance is improved when a Ti compound is added. In particular, when a Ti salt or a Ti alkoxide and a TiO ₂ sol are mixed, the effect of addition is higher than that in the case of addition alone. It can be seen that a large improvement effect is obtained even with a relatively low addition amount of 3 to 5%.

  Corrosion resistance was evaluated in a 50 ° C., 91% finish annealing atmosphere for 1 week, with an increase in mass and visual observation of the surface condition. Further, Table 4 shows the tension applied to the steel plate and the magnetic properties calculated from the bending of the plate after removing the coating on one side. From the results shown in Table 4, it can be seen that in the examples within the range defined by the present invention, a grain-oriented electrical steel sheet having a good film and having a low iron loss is obtained.

(Example 3)
Phosphate conditions As shown in Table 5, a coating solution comprising a simple substance or a mixture of heavy phosphate having a solid content of 50%, and an additive of colloidal silica and TiO ₂ having a solid content of 30% was prepared. The mixing ratio of phosphates was set to 1: 1 in volume ratio. Moreover, the mixing ratio of the mixture of phosphate and colloidal silica was set to 1: 1 by volume ratio.

Such a coating solution is applied to a grain-oriented electrical steel sheet (with a forsterite primary coating) having a thickness of 0.23 mm and containing 3.2% by mass of Si. It was applied to m ² , dried, and baked at 850 ° C. for 30 seconds in an atmosphere containing 3% hydrogen to form an oxide film on the surface.

Table 6 shows the measurement results of various properties of the coating. In the adhesion test, the test was performed by winding the cylinder around a 20 mmφ cylinder so that the angle was 180 degrees, and the adhesion was evaluated from the peeled state. A good film was obtained with any phosphate. The annealing resistance was evaluated in the same manner as in Example 1. From Table 6, it can be seen that the annealing resistance is improved when the TiO ₂ sol is added, and particularly when the addition amount is 5 to 10%, a large improvement effect is obtained.

  Corrosion resistance was evaluated in a 50 ° C., 91% finish annealing atmosphere for 1 week, with an increase in mass and visual observation of the surface condition. Further, Table 6 shows the tension applied to the steel plate and the magnetic properties calculated from the bending of the plate after removing the coating on one side. From Table 6, it can be seen that in the examples within the range defined by the present invention, a grain-oriented electrical steel sheet having a good film and having a low iron loss is obtained.

(Example 5)
Annealing temperature condition Aluminum phosphate having a solid content of 50% and colloidal silica having a solid content of 30% are mixed in a volume ratio of 1: 1, and TiO ₂ sol is mixed with 5% by mass of the coating in terms of Ti. The amount of addition was adjusted so that a coating solution was prepared.

This is 4 g / m ² in terms of coating mass after baking onto a grain oriented electrical steel sheet (with a forsterite primary coating) having a finish annealing of 0.23 mm thickness containing 3.2 mass% of Si. After coating and drying, an oxide film was formed on the surface by baking in an atmosphere containing 3% hydrogen at a temperature of 700 ° C. to 950 ° C. for 30 seconds.

  Table 9 shows the measurement results of various characteristics. In the adhesion test, the test was performed by winding the cylinder around a 20 mmφ cylinder so that the angle was 180 degrees, and the adhesion was evaluated from the peeled state. The annealing resistance was evaluated in the same manner as in Example 1. From Table 9, it can be seen that the annealing resistance is good in the case of the example baked at 800 ° C. or higher.

  Corrosion resistance was evaluated in a 50 ° C., 91% finish annealing atmosphere for 1 week, with an increase in mass and visual observation of the surface condition. Further, Table 9 shows the tension applied to the steel sheet and the magnetic properties calculated from the bending of the sheet after removing the coating on one side. From Table 9, it can be seen that in all the examples annealed at a temperature within the range specified by the present invention, a grain-oriented electrical steel sheet having a good coating and a low iron loss is obtained.

Claims (1)

The steel sheet outermost surface, Al, Mg, Ni, Mn , Co, Mo, Zr, phosphate containing at least one or more kinds of Sr, in addition to silica, a Hf oxide, in terms of metal elements, 3 of the coating amount A grain- oriented electrical steel sheet comprising a Cr-free coating containing 10% by mass on the outermost surface .