JPH0770643A - Preparation of electrolytic iron sheet - Google Patents

Abstract

PURPOSE: To enable the formation of a cubic structure to a thick steel sheet at a low temp. and for a desirable time by annealing a half-finished iron product refined into a specific carbon content in a wet atmosphere and, finally annealing and working it at a specific temp. in dried hydrogen while avoiding the rising of the carbon and oxygen contents in the steel.

CONSTITUTION: In a method for the production of an electrical sheet having a cubic structure and containing 0.9-4.5 wt.% Si, molten iron having ordinary impurities is refined with oxygen to obtain the molten iron or a half-finished iron product which is decarburized to ≤20 wt.ppm C and then, this iron is annealed in a wet atmosphere. The obtd. molten block or the half-finished iron product is remelted under a better vacuum than 1.33 Pa as the case may be, during alloying the necessary Si or successively, to lower the oxygen content to ≤10 ppm. Finally, this silicon steel material is further worked to the electrical sheet with a ordinary steel sheet producing method by using the finally- annealing to be executed at 950-1200°C in dried hydrogen while avoiding the adsorption of impurities particularly, the rising of the carbon and the oxygen contents.

COPYRIGHT: (C)1995,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electric iron sheet having a cubic structure and having a silicon content of 0.9 to 4.5% by weight. This iron plate is used for the magnetic circuit of electrical equipment as a transformer iron plate with anisotropic magnetic properties in static applications and as a dynamo iron plate with sufficient isotropic properties in the iron plate plane for rotating applications. It is possible.

[0002]

BACKGROUND OF THE INVENTION A cubic, spatially centered S
Iron plate consisting of iron / silicon alloy with i 0.9-4.5% (in this case all or part of Al may be used instead of Si), iron plate thickness controlled, surface tension induced It is known that a cubic structure can be produced by secondary recrystallization carried out. In this structure, the iron plate particles have a cubic plane (Miller index (10
0)) is parallel to the plane of the iron plate or oriented such that it is inclined at a maximum of 7 ° with respect to this plane.

At that time, a so-called cubic structure (100)
In [001], the edges of the cube (= the direction in which the magnetization can be most easily magnetized) are directed in the rolling direction and the lateral direction,
Therefore, there are two magnetic preferential directions, and there is no magnetically disadvantageous (111) direction in any direction of the iron plate plane. Such iron plates are particularly suitable for use in transformers.

A so-called cubic planar structure ((100) [O
kl]) there is no favorable cubic edge orientation. The directions of the ridges of the cube are irregularly distributed in the plane of the iron plate, so there is no disadvantageous magnetic direction, and the plane of the iron plate has isotropic magnetic properties. This iron plate is particularly suitable for rotary applications (motors, generators).

The edge of the cube is approximately ± 26 with respect to the rolling direction.
8 (scattering in the (orientation (100) [012]) direction and therefore eight broadly scattered (± 10
°) Due to the structure in which the preferred direction exists, almost isotropic characteristics are achieved.

The avoidance of advantageous orientations or orientations (irregular dispersions) of the various types of cube edges has, as is well known, different cold deformations, usually different degrees of deformation (1
(Z.Metallku) performed by cold deformation (one or several times)
nde. 57 (1966) 751-754, D.Ganz, HG.Baer).

When the size of particles (microcrystals) is substantially larger than the thickness of the iron plate due to normal grain growth, that is, when there is only one grain in each cross section of the iron plate, and the plane of the intersection between the grain boundary and the surface. Surface tension-induced secondary recrystallization in which the thickness of the iron plate is controlled is carried out when the grooves of the grain block the movement of grain boundaries, and the difference in the surface tension of various oriented grains is Provides additional driving force for selective grain growth. Only if the cubic plane has the minimum surface tension of all crystallographic planes (temperature, atmospheric and alloy purity, remarkably low oxygen content or sulfur content) is the cubic plane parallel or maximum to the iron plate surface. Grains that are tilted by 7 ° grow and fully absorb all other oriented grains. A cubic structure is obtained (Acta Metallurg
ica7 (1959) 589〜598, K.Detert, J.Appl.Phys.31 (1960) 40
8, D.Kohler).

F with the most magnetically favorable cubic structure
Technically large-scale experimental production for producing eSi sheet is controlled in an economical amount due to cost reasons and due to the difficulty in producing structural sheet (FEWerner, Ene
rgy Efficient Electrical Steels, Warrendale, Pa-TMS /
AIME, 1981, 1-31). The causes for this are in particular the following drawbacks of the conventional method: a) Since the structure formation during surface tension-induced secondary recrystallization with controlled iron plate thickness is carried out by two-dimensional grain growth, Normal grain growth must first produce a grain size greater than the iron plate thickness, which requires high grain boundary mobility and therefore high alloy purity to avoid high temperatures and long annealing times. is there. The same applies to the subsequent two-dimensional grain growth and secondary recrystallization, especially the driving force from the difference in surface tension is low. An impurity that particularly prevents grain boundary movement is carbon.

B) The thicker the iron plate is, the more difficult and slower the structure formation is, because the increased grain growth is necessary as the thickness of the iron plate increases, and in the two-dimensional grain growth. This is because the bending of the grain boundary in the cross section is reduced, and the driving force from the grain boundary stress is also reduced. Therefore, for example, the structure formation with an iron plate with a thickness of 0.05 mm is easier and more complete than with an iron plate with a thickness of 0.3 mm. However, thin iron sheets result in higher costs due to many operations, for example in rolling, stamping, laminating and due to the reduced packing density.

C) The premise for the cubic surface to have a minimum surface tension is a low oxygen concentration on the surface and thus a low oxygen concentration in the alloy in the annealing atmosphere and in the iron plate. However, the reduction of the carbon content, which particularly inhibits the movement of grain boundaries, is caused by the treatment with oxygen, the refining with oxygen or a gas containing oxygen in the molten state, to remove wet or H ₂ O on the iron plate. It is carried out by annealing in a gas which contains and thus supplies oxygen (for example H ₂ ). In doing so, the oxygen content of the alloy rises and thus the premise for the cubic structure formation is lost. The reduction of oxygen content by annealing in pure hydrogen requires high temperatures and long annealing times due to the low oxygen diffusivity. Carbon, on the other hand, is a normal steel inclusion because it reduces the iron ore.
Thus, simultaneous achievement of minimum C and O contents is largely eliminated in conventional electric iron sheet manufacturing processes.

D) Larger grain sizes (above about 10 mm) generally result due to the significant normal grain growth required to achieve the iron plate thickness dimension and the subsequent significant grain selectivity. This leads to an increase in the size of the magnetic elemental region and thus to an increased anomalous loss during magnetization.

[0012]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
It was an object of the invention to provide a process for the production of electric iron sheets which allows the formation of cubic structures on iron sheets thicker than 1 mm at temperatures up to 1200 ° C. in an economically favorable time, with grain sizes of about 1-5 mm.

[0013]

According to the present invention, the above-mentioned problems are as follows: a) First, an iron melt or an iron semi-finished product having usual impurities is decarburized to less than 20 ppm by weight of carbon, and therefore the iron melt is Refining with oxygen and annealing the iron semi-finished product in a moist atmosphere, b) the resulting molten block or the annealed iron semi-finished product is then subjected to oxygen content, optionally in or subsequently to the alloy with silicon. Remelting under a vacuum better than 1.33 Pa in order to reduce to less than 10 ppm by weight, and c) finally, the ferrosilicon material thus produced is subjected to the usual iron plate production method, but with the absorption of impurities. 950-12 in dry hydrogen for structure formation, avoiding, in particular, the elevated regulated carbon and oxygen contents of the material.
It is solved by further processing into electric iron plates using the final anneal to be carried out at 00 ° C.

The process according to the invention can be carried out as follows: In step a) the carbon content is reduced to a value below 10 ppm by weight, preferably below 5 ppm by weight.

Remelting is carried out in the electron beam melting furnace in order to reduce the oxygen content according to step b).

In step b), in interaction with the oxygen content of the material during the final annealing and the water content of the annealing atmosphere, all crystallographic planes (100) of (100)
The oxygen content is adjusted to 10 so that the crystal plane has the minimum surface tension.
Reduce to values below ppm by weight.

The melt produced in the result of step b) is cast in a crystallizer to a thickness in the range from 2 to 250 mm,
And the plate steel thus obtained is directly fed to another process corresponding to step c).

Through the sulfur content of the annealing atmosphere during the final annealing included in step c), the critical sulfur on the iron plate surface is such that the (100) crystal faces of all crystallographic planes have the minimum surface tension. Give rise to a concentration.

In the final anneal included in step c), dry hydrogen having a dew point below -60 ° C. is used and the anneal is carried out within 1 hour.

In order to produce the iron plate according to step c), the intermediate annealing and the refining annealing are avoided and the ferrosilicon material is transferred to the final annealing of the iron plate at the final thickness. Advantageously, the forging process is also avoided, and the final annealing is carried out for structure formation only by hot-rolling and cold-rolling the ferro-silicon material to the final iron plate thickness.

Due to another variant of the iron plate production according to step c), the iron-silicon material is advantageously cold-rolled only by cold-rolling to the final iron-plate thickness, avoiding the forging method and hot-rolling. Only the process moves to final annealing for structure formation.

In the case of the two-step cold rolling, the annealing is performed only once, at which time the annealing is performed as an intermediate annealing for recrystallization.

The method according to the invention has a series of significant advantages compared to the state of the art.

The relative ease and reliability of the method according to the invention and the quality characteristics of the electric iron sheet which can be produced by this method are particularly excellent. 950-12 in dry hydrogen
A perfect cubic structure is obtained when the final annealing is carried out in a temperature range of 00 ° C. for less than 1 hour. The particle size is about 1-5 mm, averaging 3 mm. Refining anneals at elevated temperatures after structure formation to improve magnetic properties (eg to avoid aging) are not required for alloy purity.

[0025]

The present invention will be described in detail with reference to the following examples.

Example 1 An iron melt was refined in a Siemens furnace, cast in a mold without sedation and then remelted in an arc furnace with electrodes of the same material. It cast in a mold and forged a bar of 30 mmφ at 1000 ° C. As a result, iron is carbon 14
Weight ppm, oxygen 850 weight ppm, sulfur 271 weight p
pm, nitrogen 30 ppm by weight and other main impurities Cr
About 600 ppm by weight, Ni520 ppm by weight, Cu45
It had a content of 0 ppm by weight, 400 ppm by weight of As and 79 ppm by weight of Mo (measured by mass spectrometry).

This iron was melted together with the purest silicon into a copper shell in an electron beam melting furnace, and 4 × 10 ² Pa
Was maintained at 18 min melt liquid at vacuum (3 × 10 ~ ⁴ Torr). After solidification, the alloy was turned inside out, melted at 4 × 10 to ² Pa for 10 minutes, and then poured into a copper mold. The alloy thereby had 3.27 wt% Si, 16 wtppm C, 5 wtppm O, 5 wtppm S2 and 2 wtppm N2.

The melt blocks were forged to a thickness of 15 mm at 1000 ° C. or cut into plates with a thickness of 15 mm.
It was hot rolled from 15 mm to 2.5 mm, washed with acid for descaling and then cold rolled to a final thickness of 0.25 mm. Further, the iron plates were chemically polished and finally annealed at 1150 ° C. for 1 hour between iron plates made of Inconel alloy in dry hydrogen (dew point less than −60 ° C.).

As a result, 90% or more of this iron plate has a cube plane parallel to the iron plate surface or inclined at a maximum of 7 ° and eight overlapping ridges of the iron plate plane of ± 22.5 ° with respect to the rolling direction. Had particles. The size of the particles was 1-5 mm in diameter.

Example 2 An electrolytic iron plate having a thickness of about 3 mm was annealed in moist hydrogen. As a result, this iron plate has C13 weight ppm, O121
It had ppm by weight, S6 ppm by weight and N3 ppm by weight. This iron plate was melted together with the purest silicon into a copper shell in an electron beam melting furnace, melted in a vacuum of 4 × 10 to ² Pa for 15 minutes, turned over after solidification, and kept liquid for 10 minutes. . This was poured into a Cu mold. The alloy thereby had 3.38 wt.% Si, 10 wt. Ppm C, O5 wt. Ppm, less than S1 wt. Ppm and N2 wt. Ppm. The fused block is forged at 1000 ° C. to a thickness of 15 mm or separated into plates with a thickness of 15 mm.
It was hot rolled to 2.5 mm at 0 ° C. Then, the iron plate was pickled and cold-rolled to 0.3 mm. The iron plates were then finally annealed in dry hydrogen (dew point below -60 ° C) between Inconel iron plates (coated) at 1100 ° C for 1 hour. As a result, more than 95% of this iron plate has a cubic plane inclined by a maximum of 7 ° with respect to the surface of the iron plate and eight overlapping cubic edges of ± 22.5 ° with respect to the rolling direction, 0.8 to 4 mm. It consisted of particles the size of.

Example 3 In this example, bar scrap consisting of a 1 mm thick iron plate was produced from carbonyl iron, decarburized and annealed and used as the starting material. Rod scraps are C8 weight ppm, O50 weight ppm, N
It had 1 ppm by weight and S1 ppm by weight. Rod scrap was melted with the purest silicon in an electron beam melting furnace, held in the melt for up to 12 minutes and cast into a Cu mold.
The iron thereby had Si 2 wt.%, C 6 wt. Ppm, O 9 wt. Ppm.

The resulting melt block was further processed by the method described in Example 1 to a final annealed iron plate.
It had the same structure and texture as the iron plate produced in Example 1.

Example 4 Pig iron was refined to 20 ppm by weight of C in an LD converter and alloyed with Si in a pot. This alloy contains 3.2 wt% Si and 50 O
It had ppm by weight and C15 ppm by weight. A molten bar of this alloy was remelted in an electron beam furnace. Solidification was carried out continuously in a crystallizer. The alloy thereby had a C content of 14 ppm by weight and an O content of 10 ppm by weight.
This block was forged into a plate steel piece having a thickness of 150 mm at 1130 to 900 ° C., planed, hot-rolled at 1200 ° C. to 3 mm, then continuously corroded, and cold-rolled to 0.15 mm. The iron plate was wrapped and final annealed in dry hydrogen (dew point below -60 ° C) with an annealed separator of Al ₂ O ₃ that was fired in a hood furnace with a coil. Thereby it had a cubic structure greater than 85%.

Claims (10)

[Claims] 1. A cubic structure and a silicon content of 0.9.
In the method for producing an electric iron plate having ˜4.5% by weight, a) first, an iron melt or an iron semi-finished product having usual impurities is decarburized to less than 20 ppm by weight of carbon, for which purpose the iron melt is oxygenated. Refining and annealing the iron semi-finished product in a moist atmosphere, b) the resulting molten block or the annealed iron semi-finished product is then optionally mixed with or in the alloy with silicon to obtain the oxygen content of 10 Remelt under a vacuum better than 1.33 Pa to reduce the value to less than ppm by weight, and c) Finally, the ferrosilicon material thus produced is subjected to the usual iron plate production method, but avoiding the absorption of impurities. 950-12 in dry hydrogen for structure formation, especially avoiding elevated regulated carbon and oxygen contents in the material.
A method for producing an electric iron plate, characterized by further processing into an electric iron plate using the final annealing to be carried out at 00 ° C. 2. A process according to claim 1, wherein in step a) the carbon content is reduced to a value below 10 ppm by weight. 3. The method according to claim 1, wherein remelting is carried out in an electron beam melting furnace for the reduction of oxygen content according to step b). 4. In step b), in interaction with the oxygen content of the material during the final annealing and the water content of the annealing atmosphere, all (100) crystal faces of the crystal faces have a minimum surface tension. Oxygen content 10 p
The method of claim 1, wherein the value is reduced to below pm. 5. The melt produced as a result of step b) is cast in a crystallizer to a thickness in the range of 2-250 mm, and the plate steel thus obtained corresponds directly to step c). The method according to claim 1, wherein the method is supplied to another processing to be performed. 6. In the final annealing included in step c), a critical sulfur concentration is set on the iron plate surface so that the (100) crystal faces of all the crystal faces have a minimum surface tension via the sulfur content of the annealing atmosphere. The method of claim 1, wherein the method is generated. 7. The method according to claim 1, wherein in the final anneal included in step c), dry hydrogen having a dew point of less than −60 ° C. is used and the anneal is carried out within 1 hour. 8. An intermediate annealing and a refining annealing are avoided for the production of the iron plate according to step c) and the ferrosilicon material is transferred to the final annealing at the final thickness of the iron plate, or the intermediate annealing and the refining annealing are avoided and forged. 2. The method of claim 1 wherein the ferrous silicon material is bypassed to final anneal only by hot and cold rolling to the final thickness of the iron sheet. 9. The method according to claim 1, wherein the forging method and the hot rolling are avoided to produce the iron plate according to step c), and the final annealing is performed only by cold rolling the iron silicon material to the final thickness of the iron plate. Method. 10. During cold rolling, the ferro-silicon material is transferred to the final thickness of the iron plate in a single step or in two steps, in which case 2
The method according to claim 9, wherein in the case of cold rolling in the step, annealing is carried out only once at the final thickness of the iron plate, and annealing is carried out as an intermediate annealing for recrystallization.