JP2522255B2 - Rolling method for high silicon iron plate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for rolling a high silicon iron sheet.

[Conventional technology and its problems]

Conventionally, silicon iron plates with a Si content of less than 4 wt% are classified into directional silicon iron plates and non-oriented silicon iron plates by the manufacturing method, and are mainly used for laminated iron cores, wound iron cores or electric shield cases for various electromagnetic induction devices. Etc. are processed and molded and are put to practical use.

However, in recent years, there has been a strong demand for miniaturization and high efficiency of electromagnetic electronic components from the viewpoint of resource saving and energy saving, and materials having excellent soft magnetic characteristics, particularly iron loss characteristics, have been demanded. It is known that the soft magnetic properties of a silicon iron plate improve with the amount of Si added, show the highest magnetic permeability especially near 6.5 wt%, and have a high specific electric resistance, so that the iron loss is also small.

However, the workability of the silicon iron plate deteriorates sharply when the Si content exceeds 4.0 wt%, and thus it has been conventionally considered impossible to manufacture a high silicon iron plate on an industrial scale by the rolling method. .

In contrast to such a rolling method, a method called an ultra-rapid solidification method has been researched and developed in recent years. However, the high silicon foil strip produced by this method is inferior in surface properties and surface flatness, and has a large thickness and thickness. The plate width is limited, and in addition, productivity is inferior and production costs are high, and there are many problems in carrying out on an industrial scale.

In view of such a current situation, the present inventors
We have been studying the manufacturing method of high-silicon iron plates with a content of 4.0 wt% or more. As a result, it has been found that it is possible to manufacture a high silicon iron sheet by rolling by selecting the rolling conditions and the like.

By the way, in manufacturing by such a rolling method, when hot-rolling a high silicon iron alloy slab, it turned out to have the following problems.

Thermal stress cracking occurs in the lump slab or continuous cast slab of cold pieces due to the temperature difference between the slab surface and the inside during cooling.

If the rolling temperature is not properly selected, rolling cracks will occur due to workability deterioration.

If the coil winding temperature is not properly selected, the coil will break during coil winding, which will further promote grain growth due to recrystallization of the material after winding, making subsequent rolling impossible.

The present invention is intended to provide a rolling method capable of appropriately preventing such rolling cracks and thermal stress cracks of a slab during rolling of a high-silicon iron plate, and further breakage during coil winding. .

[Means for solving problems]

Therefore, the present invention, when producing a high-silicon iron plate containing Si 4.0 ~ 7.0 wt% by a rolling method, the lump slab or continuous cast slab, hot piece charging to the heating furnace, or direct hot piece feeding Due to its surface temperature Ttr (℃), Ttc (℃)
In the case of a lumped slab, Trt> 40 [Si] −10 In the case of continuous cast slab, Ttc> 80 [Si] +80 However, [Si]: Si content (wt%) is maintained in the subsequent rolling process. In the first pass of the rolling process, Tr ₁ t> 40 [Si] −10 for agglomerated slab Tr ₁ c> 80 [Si] +80 for continuous cast slab where [Si]: Si content Rolling at a rolling temperature Tr ₁ t (° C) or Tr ₁ c (° C) satisfying (wt%), and in the final pass, Tr ₂ > 20 [Si] -50, where [Si]: Si content ( The basic characteristic is to roll at a rolling temperature Tr ₂ (° C.) satisfying wt%) and then to wind at a coil winding temperature Tc (° C.) satisfying 20 [Si] −50 <Tc <1000. And

 Hereinafter, the details of the present invention will be described.

The present inventors investigated the rolling workability in rolling a high silicon iron alloy.

Specifically, the rolling workability of the high silicon iron alloy containing 6.5 wt% Si was evaluated by the taper rolling test method using the test piece shown in FIG. FIG. 2 shows the result, which allows the characteristics of the rolling workability of the material to be clearly known as follows.

1) In the material having a cast structure, the workability is extremely good in the high temperature range over 900 ° C, but it directly deteriorates at 900 ° C or lower, and almost no rolling is possible at approximately 600 ° C.

2) Material that has undergone slabbing or rough rolling by hot rolling and has been refined into a fine grain structure by recrystallization, or a material that has a grain structure in the thickness direction of these materials that has been narrowed to form a textured structure. In the above, the working limit is greatly expanded as compared with the cast structure material depending on the grain size or the grain boundary spacing in the material thickness direction. That is, in the case of rolled material with a grain size of 1 mm, at about 250 ° C,
Further, in the case of a rolled material having a grain size interval of 50 μm, the rolling workability is lost at about 80 ° C., respectively, but it is possible to carry out sufficiently ordinary rolling work in a temperature range higher than that. Usually, the grain size of the slab is 1 to 3 m, even considering the grain growth due to recrystallization in the heating furnace.
m, and the continuous cast slab is 1 after hot-rolling rough rolling.
The size is reduced to about mm. In any case, the grain boundary interval in the material thickness direction can be set to about 50 μm near the final hot rolling pass.

Based on such knowledge, Si
The rolling workability of a high silicon iron plate with a content of 4.0 to 7.0 wt% was evaluated.

FIG. 3 and FIG. 4 show the results, and FIG. 3 shows the case of using a slab of slab and FIG. 4 shows the case of using a continuous cast slab as a rolling material. As a result, it was found that the working temperature limit for rolling the high silicon iron plate can be expressed by the following equation.

(1) Rolling temperature that allows the 1st pass Tr ₁ r (℃), Tr ₁ c
(℃) In case of slab slab Tr ₁ r> 40 [Si] -10 …… (1) -a In case of continuous cast slab Tr ₁ c> 80 [Si] +80 …… (1) -b (2) Final Rolling temperature that allows a pass Tr ₂ (° C) Tr ₂ > 20 [Si] -50 (2) However, [Si]: Si content (wt%) Therefore, in the present invention, a lump slab or a continuous cast slab is used. Rolling is performed so as to satisfy the above formulas (1) -a or (1) -b and formula (2).

In the rolling of a high silicon iron plate, it is necessary to select the coil winding conditions as well as the above-mentioned rolling conditions. Recrystallization process of the high silicon iron, the temperature, and although its behavior is determined Te cowpea retention time, after the hot rolling (approximately 2 ^t m about the coil) is maintained for a predetermined time than 700 ° C. Re Grain growth due to crystals occurs. Depending on the degree of this grain growth, the structure may not be suitable for warm rolling in the next step at 1000 ° C. or higher, so the coil winding temperature Tc ₁ (° C.) must be satisfied by the following formula.

Tc ₁ <1000 On the other hand, when the coil surface is wound with a coiler, the maximum strain on the coil surface is ε _Tmax = t / 2R when the coiler radius is R and the coil thickness is t, but ε _Tmax when winding a high silicon iron plate is 1 Considering that it is about less than%, if the winding temperature Tc ₂ (° C.) satisfies the lower expression of the limit of causing plastic strain, winding can be performed without sufficient breakage.

Tc ₂ > 20 [Si] -50 However, from the above point of [Si]: Si content (wt%), the coil winding temperature Tc (° C) must satisfy the following formula (3). According to the invention, the coil is wound under such conditions.

20 [Si] -50 <Tc <1000 (3) Furthermore, in rolling high-silicon steel, there is a problem of thermal stress cracking during slab cooling. Therefore, the inventors of the present invention conducted a basic tensile test (FIG. 5) on the slab of Si content 4.0 to 7.0 wt% and the thermal stress cracking during cooling of the continuous casting slab. A cooling experiment was conducted in the atmosphere, and the results shown in FIG. 6 were obtained. According to this, when the surface temperature of the slab corresponding to the Si content falls below a certain value, the plastic deformability of the material deteriorates as shown in FIG. As a result, thermal stress cracking occurs. The critical temperature Tt (° C.) of the slab surface that does not cause such cracking differs between the agglomerated slab and the continuous cast slab and can be expressed by the following equations (4) -a and (4) -b.

For agglomerated slabs Ttr> 40 [Si] -10 (4) -a For continuous cast slabs Ttc> 80 [Si] +80 (4) -b where [Si]: Si content (wt %) Therefore, in the present invention, the slab is formed from the above (4) -a, (4)-
It is sent to the subsequent rolling process while maintaining the surface temperature that satisfies the condition of b type, and the rolling in this rolling process is performed in the above (1) -a, (1).
It is performed so that the conditions of −b and the equation (2) are satisfied.

In order to roll the slab in the subsequent rolling process while keeping it at the above surface temperature, the slab obtained by slab rolling or continuous casting is charged into a heating furnace before the temperature falls below the above temperature and then rolled (HCR Method) and a method of directly sending hot strip to the subsequent rolling step before the temperature of the slab falls below the above temperature (HDR method).

Whichever method is used, the above (4) -a,
(4) In order to carry out the operation under the condition of formula (b), lump-blocking → rolling,
It goes without saying that the layout of continuous casting → rolling should be taken into consideration, but in order to prevent temperature drop during slab transportation, use a large slab thickness, use a heat insulating material, and install a heat retention furnace. It is effective to do so.

Further, when the slab is heated in a heating furnace, there are the following problems. That is, when the silicon iron plate is held at a temperature of a certain level or higher and heated, scale is generated, but when the temperature becomes higher than a certain level, FeO and SiO ₂ in the scale cause a eutectic reaction to melt (formation of ferrite). ) Do. For such a problem, the present inventors have conducted an experiment in which the oxygen content in the heating furnace was variously changed, and the heating temperature at which the Si content of 4.0 to 7.0 wt% of the high silicon iron alloy does not cause scale melting. The area was investigated. Fig. 7 shows the result, and in the heating furnace which is generally used at present, the oxygen concentration in the furnace is 2
It can be seen that the melting of the scale can be surely prevented by controlling the heating temperature to 1250 ° C. or lower by controlling the temperature up to about%. Therefore, in the present invention, it is preferable to heat the slab in the heating furnace at 1250 ° C or lower.

FIG. 8 shows an example of a production flow according to the method of the present invention, in which the slab from the slabbing process (1) or the continuous casting process (2) is charged into the heating furnace (3) with hot pieces. Alternatively, it is directly introduced into the subsequent rolling step (4) without passing through the heating furnace (direct heating piece feeding) and rolled. The slab is sequentially rolled by the rough rolling mill group and the finishing rolling mill group. In the figure, (5) is a material to be rolled, (6) is edge, and (7) is crop shear.

〔Example〕

A high silicon ingot having Si contents of 5.0 wt% and 6.5 wt% was melted and subjected to soaking one-minute lump rolling under the following conditions.

Soaking furnace charging temperature 700 ℃ (surface temperature) Soaking temperature 1150 ℃ Slab size 150mm thickness × 650mm width × 5000mm length Finishing temperature 900 ℃ (surface temperature) The obtained agglomerated slab is heated under the following conditions Rolled.

Heating furnace charging temperature 700 ℃ (Surface temperature) Heating temperature 1150 ℃ Rolling temperature 1st pass 1130 ℃ Final pass 830 ℃ Rough rolling outlet thickness 35mm Coil size 2mm ^t × 650mm ^w Coil winding temperature 600 ℃ Same as comparative example The following method was carried out for the slabs of slabs.

Comparative Example (1) After air-cooling the agglomerated slab to 150 ° C. at the surface temperature,
A method of charging in a heating furnace and performing hot rolling under the same heating conditions and rolling conditions as those of the above-mentioned examples of the present invention.

Comparative Example (2) A method in which the agglomerated slab is left to cool to room temperature in the atmosphere, charged into a heating furnace, heated to 1150 ° C., and then hot rolled.

Comparative Example (3) Agglomerated slab was charged into a heating furnace at 700 ° C (surface temperature) and
A method of heating to 300 ° C and then hot rolling.

As a result, while the slab could be produced without any problem by the method of the present invention, in Comparative Example (1), thermal stress cracking occurred in the slab and further expanded by hot rolling, and after rough rolling,
I had no choice but to stop rolling. Further, in Comparative Example (2), heating-hot rolling could not be performed because thermal stress cracking of the slab was significant. Further, in Comparative Example (3), scale melting occurred in the heating furnace, the surface damage of the slab was severe, and rolling could not be performed.

Incidentally, the present invention example, the plate thickness direction particle size interval of the hot rolled material: 5
Hot rolling was performed with the target of 0 μm. On the other hand, as another example, after hot rolling under the same conditions as above, coil winding was performed at a winding temperature of 800 ° C. The crystal grain size of this hot rolled material became about 100 to 200 μm due to the recrystallized grain growth. In such a hot rolled material, the warm rolling temperature in the next step shifts to the high temperature side, and the allowable temperature range of the warm rolling is reduced, but the rolling is sufficiently possible.

〔The invention's effect〕

According to the present invention described above, it is possible to roll a high-silicon iron sheet while reliably preventing rolling cracks, coil breaks, slab cracks, and the like.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a taper rolling test piece in the taper rolling test method. Figure 2 shows the taper rolling test method6.
The rolling workability of an iron plate containing 5 wt% Si is shown by the relationship between the rolling temperature and the critical rolling reduction per pass. FIG. 3 shows the rolling limit of the high silicon material when the lump slab is used as the rolling material, by the relationship between the Si content and the rolling limit temperature. FIG. 4 shows the rolling limit of the high-silicon material when the continuous cast slab is used as the rolling material, by the relationship between the Si content and the rolling limit temperature. FIG. 5 shows the relationship between the tensile test temperature and the elongation of 6.5 wt% Si-containing slabs (agglomerated slabs and continuous cast slabs). FIG. 6 shows the thermal stress cracking limit temperature of high silicon iron alloy slabs (agglomerated slabs and continuous cast slabs) in relation to the Si content. FIG. 7 shows the allowable scale melting temperature of the high silicon iron alloy material in relation to the oxygen content in the heating atmosphere. FIG. 8 is an explanatory view showing an example of the manufacturing flow of the method of the present invention.

Front Page Continuation (72) Inventor ▲ Taka ▼ Yoshikazu Marunouchi 1-2-2, Marunouchi, Chiyoda-ku, Tokyo Japan Steel Tube Co., Ltd. (72) Masahiko Yoshino 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Japan Steel Pipe Co., Ltd. (72) Inventor Yasuyuki Miyai 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Steel Pipe Co., Ltd. (56) Reference JP 61-166923 (JP, A) JP 52-95096 ( JP, A)

Claims (2)

(57) [Claims] 1. When manufacturing a high-silicon iron plate containing Si: 4.0 to 7.0 wt% by a rolling method, a lump slab or a continuous cast slab is charged into a heating furnace by hot piece charging or directly sent. The surface temperature Ttr (℃) and Ttc (℃) can be calculated by Trt> 40 [Si] −10 in case of agglomerated slab and Ttc> 80 [Si] +80 in case of continuous cast slab, where [Si]: Si content (Wt%) and then charged into the subsequent rolling process. In the first pass of the rolling process, Tr ₁ r> 40 [Si] -10 continuous cast slab Tr ₁ c> 80 [Si] + 80 However, [Si]: rolling at a rolling temperature Tr ₁ r (℃) or Tr ₁ c (℃) that satisfies the Si content (wt%), and in the final pass Tr ₂ > 20 [ Si] -50 However, rolling at a rolling temperature Tr ₂ (° C) that satisfies the [Si]: Si content (wt%), and then coil winding that satisfies 20 [Si] -50 <Tc <1000 Winding at temperature Tc (℃) Rolling method of the high silicon steel plates, characterized. 2. The method for rolling a high silicon iron plate according to claim 1, wherein the heating temperature of the slab in the heating furnace is 1250 ° C. or lower.