JPS6248463A - Shot blasting method for silicon steel plate of non-directivity - Google Patents

Abstract

PURPOSE:To enable a steel plate to be shot blasted preventing its descale property from worsening further generating no fine crack on a surface of the steel plate after the base plate is annealed, by setting a temperature of the shot blasted base material to a specific range. CONSTITUTION:Shock absorbing energy of a steel plate is increased by heating its base plate, when it is shot blasted, to increase the temperature T( deg.C) to a predetermined value of T>=80XSi(%)-180, and the steel plate, increasing also a ductile fracture rate, enables a crack to be prevented from being generated in the plate when it is shot blasted. Further the invention is out of the subject for the steel plate, containing less than 2.5% Si, because its ductile fracture rate increases even in the normal temperature generating no crack on the surface. While the invention is out of the subject for the steel plate, containing Si exceeding 3.5%, because its cold rolling property is remarkably deteriorated.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention aims to improve the surface appearance of a non-oriented silicon steel sheet containing 2.5 to 3.5% Si by reducing the scale of a hot-rolled Iff sheet. This invention relates to a shot blasting method for peeling off a mother plate after annealing.

[Prior Art] When cold rolling a hot rolled sheet, descaling and trimming to remove hot scale and edge defects (ear cracks kg) are generally performed on a pickling line. It is.

In the case of silicon steel sheets as well, mother plate annealing to modify the hot-rolled structure is carried out in a box-shaped or continuous annealing chamber, and then the above-mentioned treatment is carried out in a bicking line.

Pickling is a common descaling treatment, but in the case of silicon steel sheets, the scale layer is thick and the pickling time is long, so a shot blasting method is used as a pretreatment.

Conventionally, in the shot blasting method in which scale is removed from a steel plate by colliding with centrifugally projected steel shot, in order to obtain a large impact energy of the shot, sea, -
The particle diameter is approximately 0.4 to 0.8 mmφ.

By the way, Si is 2.5 to 3.5%, An, Mn, etc. are added as required, AlO, 25 to 1.0%, Mn0.
Mother plate annealing is also carried out on non-oriented silicon steel sheets containing 1 to 1.0%. This is Slavic i! I! Columnar crystals are generated during casting, and even if L'T crystal annealing is performed after cold rolling, fine irregularities called ridging occur in the rolling direction, impairing product value. This is for annealing the mother plate.

However, when the RI plate is annealed, the ductility of the fl') plate is reduced and the crystal grains become coarse, which makes the L plate extremely brittle.

[Problem to be solved by the invention] Therefore, regarding non-oriented silicon steel sheets.

During shot blasting, there is a phenomenon in which fine racks are generated within grain boundaries that have become coarse due to annealing of the mother plate. This remains as a concave flaw after cold rolling, and when an insulating coating is applied to the silicon steel sheet, air is drawn into the concave portion, which then bursts during drying, causing defects in the insulating coating.

As a method for preventing bipedal concave defects, for example, as shown in Japanese Patent Application No. 59-248384, in order to reduce the impact energy of steel shot, the shot particle size should be made smaller (e.g. 0.3 !l+s+sφ) is also possible. However, reducing the shot particle size in this manner has the disadvantage that descaling performance is poor and the washing time is increased.

The present invention has the following advantages: without impairing descaling properties and without causing microcracks on the surface of the steel plate after annealing the plate.
The purpose is to make it possible to produce a non-oriented silicon steel plate that can be shot blasted and has an excellent appearance.

[Means for solving the problems] The present invention provides Si2.5 to 3.5% and other A as necessary.
In a shot blasting method in which the scale of a hot-rolled non-oriented silicon steel plate containing L, Mn, etc. is peeled off after annealing the base material, the temperature T (°C) of the base material to be shot blasted is , T≧80×Si(%)−180.

[Effect J] According to the present invention, by heating the base plate to a predetermined temperature during shot blasting, the impact absorption energy of the steel plate increases and the ductile wave front ratio also increases, which reduces the occurrence of cracks during shot blasting. Defense II- becomes possible.

Note that steel plates with a Si content of less than 2.5% are excluded from the scope of the present invention because they have a large ductile fracture ratio even at room temperature and do not cause surface cracks, and steel plates with a Si content of more than 3.5% are excluded from the scope of the present invention. 1F not developed due to significant deterioration of cold rolling properties
shall be excluded from the scope of

[Example] Hereinafter, the shot blasting method according to the present invention will be explained in detail based on experimental results.

Hot-rolled silicon steel plate with 2.5-3.5% Si +
o o o 'c, After annealing for 3 minutes, the temperature of the steel plate was variously changed, and the steel plate at each temperature had f uniform grains Pf:Q, f3
A shot of 5msφ was projected. Figure 1 shows the occurrence of cracks on the surface of the steel plate in this case. According to Figure 1, the mother plate temperature T (°C) during shot blasting is S
Depending on the i-form.

It is recognized that by increasing T≧5oxsi(%)−t8o (1), the occurrence of cracks can be prevented.

Next, a hot-rolled silicon steel plate with 3% Si was
Figure 2 shows the results of investigating the occurrence of cracks on the surface of the I+A plate after annealing the mother plate for 3 minutes and shot blasting by changing the shot particle size and mother plate temperature.
According to this Figure 2, if the shot particle size is less than 0.35 mφ, no cracks will occur even if the mother plate temperature decreases;
When the shot particle size is 0.4 to 0.8 mmφ, cracks are observed unless the fil plate temperature is lowered to 60° C. or higher.

FIG. 3 is a layout diagram showing a continuous annealing and pickling line to which the present invention is applied. 11 is a payoff reel, 12 is an annealing furnace (
12A is a heating and soaking zone, 12B is a cooling zone), 13 is a shot blasting device, 14 is a pickling tank, 15 is a trimming device, and 16 is a tension reel. In this continuous annealing and pickling line, by controlling the temperature of the 11 plates in the cooling zone 12B, it is possible to control the temperature of the mother plate before shot blasting. Furthermore, the base plate may be heated with steam, hot water, a burner, etc. before shot blasting.

[Shot 1! ! ] As described above, the present invention improves the scale of a hot-rolled RI material of a non-oriented silicon steel sheet containing 2.5 to 3.5% Si and optionally AM, Mn, etc. In the shot blasting method in which the 1+L material is peeled off after annealing, the temperature T (°C) of the Ill material to be shot blasted is set to T≧aoxsi(%)-180. Therefore, It becomes possible to perform shot blasting without impairing descaling properties and without producing microcracks on the surface of the steel sheet after annealing the mother plate, and it becomes possible to manufacture non-oriented silicon steel sheets with excellent appearance. .

[Brief explanation of drawings]

Figure 1 is a diagram showing the crack occurrence situation when the Si% of a non-oriented silicon steel plate and the base plate temperature during shot blasting are changed, and Figure 2 is a diagram showing the shot grain size and base plate in a 3% Si #4 plate. Figure 3 is a layout diagram showing the continuous annealing and pickling line. 12B... Cooling zone, 13... Shot blasting device. Agent Patent Attorney Osamu Shiokawa 1st Sj (%) Figure 2

Claims (1)

[Claims] (1) Si2.5-3.5%, other Al as required,
In a shot blasting method in which the scale of a hot-rolled base material of a non-oriented silicon steel sheet containing Mn etc. is peeled off after annealing the base material, the temperature T (°C) of the base material to be shot blasted is T≧ A method for shot blasting a non-oriented silicon steel plate, characterized in that the ratio is 80×Si(%)-180.