JPH07113129B2 - Method for manufacturing silicon steel sheet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a high silicon steel sheet having excellent soft magnetic properties, which is used for a magnetic core of a rotating machine, a generator, or the like.

[Conventional technology]

Silicon steel sheets have been used in large amounts as magnetic cores for electric power and materials for rotating machines because of their excellent soft magnetic properties, but in recent years, transformers and rotating machines have been used from the viewpoint of energy saving and resource saving. There is a strong demand for efficiency and miniaturization of the electric equipment, and accordingly, the soft magnetic properties and core loss properties of the silicon steel sheet, which is the material for the iron core, are being demanded.

The soft magnetic properties of this silicon steel sheet improve with the amount of silicon added, and show the highest magnetic permeability, especially near 6.5 wt%.
Furthermore, since the specific electric resistance is high, it is known that the iron loss is also small. However, the silicon content is 4
When the content exceeds%, the workability is rapidly deteriorated, and it has been considered extremely difficult to manufacture a thin plate on an industrial scale by the conventional rolling method.

As a result of various studies conducted by the present inventors in order to solve this problem, as a result of selecting appropriate rolling conditions even for the above-mentioned high silicon-containing steel of more than 4%, high cold workability is achieved. Knowing that silicon hot rolled steel sheets can be manufactured continuously,
The basic manufacturing method was presented in Japanese Patent Application No. 60-128323.

That is, this method achieves grain refinement by selecting appropriate rolling conditions when slab-rolling or rough-rolling an ingot or continuously cast slab, and continuously finishing hot rolling them at a relatively low temperature. However, it is characterized by imparting excellent cold rolling property by adjusting the average grain boundary spacing in the thickness direction of the hot-rolled sheet according to the amount of Si added.

[Problems to be solved by the invention]

However, as a result of further tests and studies, the following facts were found. That is, in order to adjust the grain size in the plate thickness direction to a critical value or less according to the amount of Si added by the above method in the continuous hot rolling process, the required cumulative rolling reduction estimated from the grain size before hot rolling That is, there is a case where a high silicon steel sheet excellent in cold workability cannot be stably manufactured even if strain corresponding to is added.

[Means for solving problems]

The inventors of the present invention to solve the above problems, as a result of extensive studies and researches thereafter, the structure in the thickness direction of the hot-rolled sheet becomes non-uniform unless strict control is applied during finishing hot-rolling,
To newly discover that it causes deterioration of cold rolling property and improve it, for the finishing hot rolling method in the above-mentioned high silicon steel sheet manufacturing method, using a hot lubricant during continuous finishing hot rolling, or In addition, by using a hot rolling mill with an appropriate roll diameter, a more uniform hot-rolled sheet structure can be obtained in the sheet thickness direction, and stable high-silicon hot-rolled steel sheet with excellent cold workability can be obtained. And it came to the conclusion that it can manufacture efficiently.

That is, the present invention is C: 1 wt% or less, Si: 4.0 ~ 7.0 wt%,
Mn: 0.5 wt% or less, Al: 2 wt% or less, the balance unavoidable impurities and iron alloys are melted and then cast by ingot casting or continuous casting, and then hot rolling after slabbing / rough rolling or after rough rolling. When manufacturing a silicon steel sheet by performing cold rolling and annealing after removing the surface oxide film, the basic characteristic is to use a hot lubricant during finish hot rolling. Is. Still another basic feature is that during the final hot rolling, rolling is performed using a hot lubricant and, in addition, rolling using a roll having a diameter 20 times or more the thickness of the charging plate.

The method of the present invention will be described in detail below.

First, the reasons for limiting the components will be described.

C is a harmful component that increases iron loss and causes magnetic aging. However, C is Fe
Since it is an element that expands the γ loop in the -Si system equilibrium diagram, an α-γ transformation point will appear during cooling when a fixed amount determined by the silicon content is added, and heat treatment using it will be possible. Therefore, it may be desirable to add C to some extent. In the present invention, C is 1 w from the viewpoint of workability.
Limited to t% or less.

Si is an element effective in increasing the specific electric resistance, reducing the eddy current loss, and reducing the iron loss. In the present invention, Si4.0wt
The target is a high silicon iron alloy containing at least%, and this is the lower limit. On the other hand, if the Si content exceeds 7.0 wt%, the manufacturing cost will increase and the magnetic properties, especially the maximum magnetic permeability will deteriorate, so this is the upper limit. For the above reasons, the limited range of Si is 4.0 to 7.0 wt%.

Mn is necessary to suppress hot embrittlement due to S, but if it exceeds 0.5 wt%, the workability deteriorates due to solid solution hardening, so the content is made 0.5 wt% or less.

Al effectively acts to fix N, which deteriorates the deoxidation and magnetic properties of steel, and, like Si, is a useful element for increasing the specific electrical resistance and reducing the iron loss. However, if added in a large amount, the cold rolling property deteriorates and the cost increases, so the upper limit is made 2 wt%.

The molten steel whose composition has been adjusted as described above is made into a slab by the ingot-bulk rolling method or the continuous casting method (in some cases, continuous casting-bulk rolling), and the slab is recrystallized to refine the structure. While performing rough hot rolling, then finish hot rolling to a predetermined plate thickness according to the present invention. In the present invention, a hot lubricant is used for this hot rolling. The hot lubricant is used here because of the non-reinforcing structure in the sheet thickness direction, which is likely to be caused by the hot rolling under high pressure rolling, preferably at 1100 to 500 ° C in the non-recrystallization temperature range according to the grain size before hot rolling. This is to improve uniformity. According to this method of the present invention, it is possible to uniformly apply strain according to the cumulative reduction in the temperature range in the plate thickness direction, so that it is easy to form a hot-rolled sheet structure having excellent cold workability. Therefore, the cold-rolling property of the obtained hot-rolled sheet also becomes extremely good.

For hot lubricants, paraffinic mineral oils, naphthenic mineral oils, aromatic oils, fats, fatty acids, synthetics, as long as viscosity characteristics of about 10 to 10000 Poise are exhibited in the temperature range of 500 to 1100 ° C. Organic substances such as esters, amine-amide complexes, meta and pyrophosphates, glassy systems,
No limitation is imposed on the chemical composition, the shape, the material, etc. of the inorganic material, and the limitation of the raw material, mixing, and dilution. Further, it may be applied at the time of rolling or may be applied in advance, and there is no difference in action and effect depending on the use or non-use of rolls, steel materials and cooling water.

Further, if rolling is carried out using a roll having a diameter 20 times or more the thickness of the charged sheet (sheet thickness before hot rolling for finishing), the effect of efficient homogenization is expected as with the above hot lubricant. Charge plate thickness of 20
In finish hot rolling using a roll having a diameter less than twice, the strain distribution in the plate thickness direction becomes non-uniform, so that the structure in the plate thickness direction of the hot-rolled plate becomes non-uniform and the cold rolling property also deteriorates. Therefore,
From this point of view, in the second invention, the hot lubricant is used, and the finish hot rolling is performed using the roll having the diameter of 20 times or more the thickness of the charging plate. As a result, the control of the hot-rolled sheet structure having a good cold rolling property can be performed more efficiently. That is, in order to manufacture a thin sheet of high silicon steel by cold rolling, if a finish hot-rolling is performed by the method of the present invention and the hot-rolled sheet structure has a uniform structure in the plate thickness direction, a very good cold Ductility can be imparted.

〔Example〕

Example 1. A continuously cast slab having a thickness of 150 mm and consisting of the chemical components shown in Table 1 was heated at 1250 ° C. for 3 hours and immediately rough-rolled to a thickness of 30 mm, and then two-stage hot rolling with a roll diameter of 480 mm. Using a machine, during hot rolling for finishing, hot rolling was performed in 6 passes using 4 types of hot lubricants as shown in Table 2 to a thickness of 2 mm. At this time, the finishing inlet temperature was 1100 ° C and the outlet temperature was 850 ° C.

As a comparative example, hot rolling was performed in the same manner as in the above pass schedule without using a hot lubricant.

The obtained hot rolled sheet was pickled and then cold rolled to 0.35 mm,
The cold rolling property (cold rolling property by 5-point evaluation) was determined. The results are shown in Table 3. According to this, it is clear that when any of the hot lubricants is used, they exhibit extremely excellent cold rolling property.

Example 2. Using a slab of slab having the same chemical composition as in Table 1 and having a thickness of 150 mm, after heating, roughly rolling to a thickness of 30 mm, and then rolls having roll diameters of 300 mm, 480 mm, 600 mm, and 820 mm, respectively. Using the glassy powder shown in Table 2, a hot rolled finish coil (finishing outlet side temperature: 810 ° C.) was used to obtain a hot rolled coil having a thickness of 2 mm. After pickling, it was cold rolled to a thickness of 0.35 mm and its cold ductility (similar to Example 1) was evaluated. The results are shown in Fig. 1. According to this, the cold rolling property when using a roll diameter 20 times or more of the charging plate thickness (plate thickness before hot rolling) and using a hot lubricant is better than that without lubrication. It can be seen that it exhibits more excellent cold workability.

Example 3 C, Al, Mn, and P were added to an iron alloy containing Si at 6.5 wt% (target value), and the total amount of impurity elements other than Fe, Si, C, Mn, P, and Al was determined.
An ingot with 0.05 wt% or less was prepared. This was put into a soaking pit in a hot mass, soaked at 1100 to 1250 ℃, and slabbing with a rolling reduction of 60 to 80%. After this rolling, hot pieces were charged into a heating furnace, heated to 1100 to 1250 ° C., and roughly rolled at a rolling reduction of 60 to 90% to obtain a plate having a thickness of 30 mm. And the plate temperature is 1100 ~
Finishing hot rolling was started at 900 ° C, and a 2 mm hot rolled sheet was finished. This finishing hot rolling is performed by using a roll having a roll diameter of 300 to 1800 mm, using the glassy powder of type (1) in Table 2 as a hot lubricant, and using a similar roll for comparison. Rolling was carried out without using a lubricant. After descaling the hot-rolled sheet, cold rolling was performed at a reduction rate of 75%, and the cold rollability was evaluated according to the same criteria as in Example (1).
The cold rolling was performed at a plate temperature of 20 to 250 ° C.

FIG. 2 shows a ratio (cold hot-rolling roll diameter / plate thickness) at which the cold rolling property (cold rolling property based on the 5-point evaluation in FIG. 1) becomes “rating 5”. According to this, as the content of each of Al, C, Mn, and P increases, the roll diameter necessary for obtaining good cold rolling tends to increase, but a hot lubricant is used for finish rolling according to the present invention. Further, it can be seen that good cold rolling property can be obtained by setting the ratio of (roll diameter / plate thickness) to 20 or more.

Example 4 An iron-silicon alloy having the composition range shown in Table 4 was melted. At this time, the component values of Fe, Si, C, Mn, P, and Al are analyzed to analyze other impurity elements (mainly, Cr, Ti, W, Mo, Co, Cu,
The total amount of (S, B, As) was obtained, and the total amount was varied to make various ingots with different total amounts of impurity elements. This ingot was charged into a soaking pit with hot mass and soaked at 1100 to 1250 ℃,
Slab rolling with a reduction of ~ 80% was performed. After the rolling, the heating piece was charged into a heating furnace and heated to 1100 to 1250 ° C., and rough rolling was performed at a reduction rate of 60 to 90% to obtain a plate thickness of 30 mm. And the plate temperature is 11
Finish hot rolling was started at the stage of 00 to 900 ° C to obtain a 2 mm hot rolled sheet. This finishing hot rolling was performed using a roll with a diameter of 700 mm, using the glassy powder of type (1) in Table 2 as the hot lubricant, and using a similar roll for comparison for comparison. Rolled without doing.

FIG. 3 shows the relationship between the total amount of impurity elements in the alloy and the cold workability (cold rollability based on a 5-point evaluation). The cold ductility tends to deteriorate slightly as the total amount of impurity elements increases, According to the present invention, a hot lubricant is used and (roll diameter / plate thickness)
It has been shown that by setting the ratio to 20 or more, good cold workability can be obtained.

[Advantages of the Invention] As described above, according to the present invention, it is possible to easily control the hot rolling structure during finish hot rolling, and to stably and efficiently manufacture a high silicon steel sheet having dramatically excellent cold workability.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between (roll diameter / charging plate thickness) ratio and cold rollability. Fig. 2 shows the relationship between the concentration of each additive element in the alloy and the cold rollability (roll diameter / charging plate thickness) ratio with and without the use of hot lubricant in finish rolling. It shows the relationship. FIG. 3 shows the relationship between the total amount of impurities in the alloy and the cold rollability with and without the use of a hot lubricant for finish rolling.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Inagaki 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. Nihon Steel Tube Co., Ltd. (72) Inventor Hironori Ninomiya 1-2 1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Tube Co., Ltd.

Claims (6)

[Claims] 1. C: 1 wt% or less, Si: 4.0-7.0 wt%, Mn: 0.5 wt
% Or less, Al: 2 wt% or less, the balance consisting of iron and unavoidable impurities, and then cast by ingot casting or continuous casting,
After slabbing / rough rolling or after rough rolling, hot rolling is performed to remove the surface oxide film, and then cold rolling and annealing are performed to produce a silicon steel sheet. A method for manufacturing a silicon steel sheet, which is characterized by being used. 2. A method for producing a silicon steel sheet according to claim 1, wherein the hot lubricant is used in a temperature range of 500 to 1100 ° C. 3. A method for producing a silicon steel sheet according to claim 2, wherein a hot lubricant having a viscosity of 10 to 10,000 poise in a temperature range of 500 to 1100 ° C. is used. 4. C: 1 wt% or less, Si: 4.0-7.0 wt%, Mn: 0.5 wt
% Or less, Al: 2 wt% or less, the balance consisting of iron and unavoidable impurities, and then cast by ingot casting or continuous casting,
After slabbing / rough rolling or after rough rolling, hot rolling is performed to remove the surface oxide film, and then cold rolling and annealing are performed to produce a silicon steel sheet. And a rolling method using a roll having a diameter 20 times or more the thickness of the charging plate, and a method for manufacturing a silicon steel sheet. 5. The method for producing a silicon steel sheet according to claim 4, wherein the hot lubricant is used in the temperature range of 500 to 1100 ° C. 6. The method for producing a silicon steel sheet according to claim 5, wherein a hot lubricant having a viscosity of 10 to 10000 poise in a temperature range of 500 to 1100 ° C. is used.