JPH0615705B2 - High silicon iron plate with excellent workability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high silicon iron plate having excellent workability.

[Conventional technology]

Conventionally, an iron plate containing less than 4.0 wt% of Si is called a directional silicon steel plate or a non-oriented silicon steel plate depending on its manufacturing method, and is mainly used for laminated iron cores, wound iron cores, or electromagnetic shields for various electromagnetic induction devices. It is processed and molded into a case for use and is put to practical use.

In recent years, miniaturization and high efficiency of electromagnetic electronic parts have been strongly demanded from the viewpoint of resource saving and energy saving, and materials having excellent soft magnetic properties, especially iron loss properties have been demanded. In the Si-Fe alloy system, iron loss decreases as the amount of Si added increases.
It is known that around 6.5 wt%, the magnetic permeability becomes maximum and the magnetostriction becomes zero, resulting in excellent soft magnetic properties.

However, if the amount of Si added is 4 wt% or more, the workability is significantly deteriorated, and thus it is conventionally difficult to industrially manufacture by a rolling method that is a combination of hot rolling and cold rolling. The manufacturing method thereof is, for example, JP-A-59.
Only the ultra-rapid solidification method as disclosed in Japanese Patent Publication No. 38328 is disclosed. However, the high silicon foil strip produced by this ultra-rapid solidification method has inferior surface properties and surface flatness compared to rolled products, and it is difficult to produce thick materials. There are many problems in putting it to practical use.

Therefore, the inventors of the present invention have repeatedly studied the rollability of high silicon steel, and as a result, by optimizing the hot rolling conditions, cold rolling on an industrial scale, which has been considered impossible until now, is possible. We found that rolling is possible, and proposed this as Japanese Patent Application No. 60-5951 (Japanese Patent Publication No. 3-65001). Since the high silicon iron plate produced by this rolling method has excellent surface properties, it has a high space factor when producing a wound iron core or a laminated iron core, and a thick material can be easily produced. In addition to the magnetic properties, it has extremely advantageous features such as the fact that the assembly process of can be greatly simplified.

[Problems to be solved by the invention]

However, it has been found that when the high silicon iron plate manufactured by the rolling method in this manner is processed into concrete parts, there are the following major problems. Generally, conventional silicon steel sheets containing less than 4.0 wt% of Si are supplied to customers in a state of being coated with an inorganic or organic / inorganic insulating film after being given predetermined magnetic properties by recrystallization annealing. Or is subjected to recrystallization annealing at a relatively low temperature for the purpose of improving the grain growth property of the final annealing magnet performed by the customer, and then subjected to skin pass and supplied to the customer. The former is called a full-process material, and consumers are working to form those steel plates, and then strain-relieving annealing as necessary to obtain electromagnetic electronic components. On the other hand, the latter is called a semi-processed material, and the grain coarsening annealing and work forming are performed by the consumer.

However, in the high silicon iron plate containing Si: 4.0 wt% or more produced by the rolling method, if the crystal grains are coarsened by the recrystallization annealing for imparting predetermined magnetic properties, the workability is significantly deteriorated. It has been found that it is difficult to manufacture the electromagnetic electronic component by the conventional manufacturing process. That is, in the above-described work forming, the defect rate becomes high even if special consideration is given to strictly control the clearance of the mold in press-extrusion processing. If the radius of curvature of becomes smaller, cracking occurs, making it impossible to process.

[Means for solving problems]

The present invention has been made to solve the problems of the high silicon iron plate manufactured by such a rolling method, and the basic feature thereof is that Si manufactured by the rolling method is
It is a high silicon iron plate containing ˜7.0 wt%, and the plate thickness t and the average crystal grain size d in the plate thickness direction satisfy the following formula according to the Si content.

t-0.8 × [Si] +7.2 (mm) d78 × [Si] ² −1500 × [Si] +6752 (μm) where [Si] is the Si content in wt%. explain.

The silicon iron plate of the present invention contains Si produced by the rolling method 4.
It is a high silicon iron plate containing 0 to 7.0 wt%. As described above, Si is an element effective in increasing the specific electrical resistance, reducing the eddy current loss, and reducing the iron loss. When Si is less than 4.0 wt%, there is no problem in workability and formability of the plate after recrystallization annealing. On the other hand, when Si exceeds 7.0 wt%, the magnetic properties such as increase in magnetostriction, decrease in saturation magnetic flux density and maximum magnetic permeability are deteriorated, and the workability is deteriorated.

In the iron plate of the present invention, in the composition as described above, the plate thickness t and the average particle size d in the plate thickness direction are t−0.8 × [Si] +7.2 (mm) d78 × [Si] ²⁻ depending on the Si content. 1500 × [Si] +6752 (μm) However, [Si] should satisfy the Si content in wt%.

FIGS. 1 (a) and 1 (b) show a 6.5% silicon iron plate having a plate thickness of 2.0 mm, which was subjected to bending and punching tests after heat treatment to examine the annealing temperature dependence of workability. Of these, Figure (a) shows a three-point bending test at room temperature (punch diameter: 1 mm, span:
75 mm), and the minimum bendable radius of curvature of the bent part after unloading is plotted. On the other hand, (b) is a punching test result, and after punching a disk-shaped sample having a diameter of 10 mm (clearance: about 50 microns), the occurrence of burrs and the cracking of the sample were observed to evaluate the defect rate. The result. According to this, while the sample annealed at a temperature of 600 ° C. or less which is a rolled structure and the 600 to 700 ° C. annealed material which is a partially recrystallized state have excellent bending workability and punchability, In the sample annealed at a temperature of 800 ° C. or higher in which the whole is in a recrystallized state and grain growth occurs, bending is almost impossible and the punchability is deteriorated.
From such a fact, it has been clarified that the structure of the work material has an important meaning in performing the work forming of the high silicon iron plate. Therefore, using a 6.5% silicon iron hot-rolled sheet with a plate thickness of 3.0 mm as the material, the structure was changed by rolling and various heat treatments, and bending workability was obtained when the plate thickness was 2 mm (constant). The effect of the average grain size in the sheet thickness direction (indicated by the average grain boundary spacing in the sheet thickness direction for the rolled structure and the average grain size for the recrystallized structure) was investigated. The results are shown in FIG. From this figure, the bending workability depends on the average grain size in the plate thickness direction, and when the average grain size in the plate thickness direction is about 300 microns or less, the bending workability is excellent regardless of the recrystallized structure or rolled structure. It became clear. In FIG. 1, the sample in the partially recrystallized state shows good bending workability, which was also confirmed to be an effect of the average grain size in the plate thickness direction. Next, the dependency of the average grain size d _{0 in} the critical plate thickness direction in which such bending is possible on the Si content was examined.
As a result, as shown in FIG. 3, the average grain size d in the plate thickness direction
Is less than the limit area d ₀ determined by the silicon content Si, bending is possible, and as a result of regression analysis by the least square method, dd ₀ = 78 × [Si] ² ] −1500 × [Si] +6752
It was found that bending can be performed by satisfying the condition (μm). FIG. 4 shows an average crystal grain size in the plate thickness direction of 28
It shows the influence of the plate thickness on the bending workability of a high silicon iron plate of 0 micron. From this figure, it can be seen that the bending workability deteriorates as the plate thickness increases. High-silicon iron plates have a high susceptibility to cracking especially under tensile stress, and it is considered that the maximum tensile strain that acts on the plate surface dominates bendability, and when they exceed a certain value, cracking rapidly occurs. To be In general, when a plate sample is bent, the thicker the plate, the greater the amount of strain on the plate surface when bent to the same radius of curvature. Therefore, the bending workability of the high silicon iron plate is affected by the plate thickness, and the thicker the plate, the more easily it breaks. Next, FIG. 5 shows the result of investigation on the silicon content dependency of the limit plate thickness t _{0 that} enables bending work.
Here, the limiting plate thickness is obtained by a bending test of a sample having an average crystal grain size in the plate thickness direction of about 280 microns (constant). From the figure, it is understood that the limit plate thickness t ₀ depends on the silicon content, and when the result of the regression analysis satisfies t = t ₀ = −0.8Si + 7.2, bending is possible.

As is clear from the above description, the workability is most excellent in the case of a rolled structure, but if the plate thickness direction average crystal grain size satisfies the above relational expression, a partial recrystallized structure, or recrystallization It is also possible to process and mold the tissue.

〔Example〕

Example (I) A high silicon iron hot-rolled sheet (sheet thickness 2.0 mm) having a composition of 0.0033 wt% C-6.48 wt% Si-0.15 wt% Mn was cold-rolled into a 0.5 mm cold-rolled sheet. At this time, the average crystal grain size in the plate thickness direction was about 20 microns. Then, (A) a high-silicon iron cold-rolled sheet in the state of the rolled structure (B) the cold-rolled sheet was annealed at 650 ° C. for 1 hour to form a partially recrystallized structure having a grain size in the thickness direction of about 25 μm. (C) The above cold-rolled sheet was annealed at 1000 ° C for 1 hour, and a ring-shaped sample with an outer diameter of 20 mm and an inner diameter of 10 mm was punched from a recrystallized structure having a grain size in the thickness direction of about 600 microns. The punchability was evaluated by the presence or absence of. Next, they were annealed in a vacuum at 1200 ° C. for 1 hour, and after the winding was loaded, DC and AC magnetic measurements were performed.

The punchability and the magnetic measurement results are shown in Table 1. The measurement was carried out for each of 10 samples, and the average value is shown in the table.

As shown in Table 1, in the comparative material (C), cracking during punching was impossible due to pressure contact, whereas in the material of the present invention, the grain size in the plate thickness direction was less than the limit value d _0. The high-silicon iron plate having the rolled structure (A) and the partially recrystallized structure (B) of No. 2 was easy to punch and showed excellent magnetic properties.

Example (II) The same high-silicon iron hot-rolled sheet (sheet thickness 2.0 mm) as in Example (I) was temperature-rolled under the condition that the sheet temperature on the inlet side was 300 ° C. to obtain a 0.1 mm thin sheet. Then, (A) the high silicon thin plate in the state of the rolled structure (the average grain size in the plate thickness direction: 10 μm or less) (B) the thin plate is annealed at 700 ° C. for 3 minutes to obtain an average grain size in the plate thickness direction of about 40 micron recrystallized state (C) The thin plate was annealed at 1000 ° C for 1 hour, and the recrystallized structure having an average crystal grain size in the plate thickness direction of about 450 micron was wound to obtain an outer diameter. 15mm, inner diameter 12mm, thickness 3
It was formed into a wound iron core of mm and the formability at that time was investigated. Next, the molded product was impregnated with an inorganic insulating film, annealed in vacuum at 1200 ° C. for 1 hour, and direct current and alternating current magnetic measurements were performed. The results are shown in Table 2.

As shown in Table 2, in the comparative material (C), cracking occurred in the winding molding and the workability was impossible, whereas the average grain size in the plate thickness direction of the material of the present invention was the limit value d. The high silicon iron plate having a rolled structure (A) and a recrystallized structure (B) of ₀ or less had good toroidal coil winding properties and exhibited excellent magnetic properties.

[Brief description of drawings]

FIGS. 1 (a) and 1 (b) show the annealing temperature dependence of the workability of a 6.5% silicon iron plate. FIG. 1 (a) is a three-point bending test, and FIG. 1 (b) is The results of the punching test are shown. FIG. 2 shows the influence of the average grain size in the plate thickness direction on the bending workability of a high silicon iron plate. FIG. 3 shows the dependency of the average grain size d _{0 in} the critical plate thickness direction on the Si content, which enables bending of a high silicon iron plate. FIG. 4 shows the influence of the plate thickness on the bending workability of a high silicon iron plate. FIG. 5 shows the Si content dependency of the limit plate thickness t _{0 that} enables bending work.

Claims (1)

[Claims] 1. Si produced by a rolling method is 4.0 to 7.0 wt.
%, A high silicon iron plate having a high workability, characterized in that the plate thickness t and the average crystal grain size d in the plate thickness direction satisfy the following formula in accordance with the Si content. t ≦ −0.8 × [Si] +7.2 (mm) d ≦ 78 × [Si] ² −1500 × [Si] +6752 (μm) where [Si] is the Si content in wt%