JP2001115241A - Steel for silicon steel wire excellent in wire drawability and producing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a stock for a silicon steel wire excellent in wire drawability, particularly cold wire drawability to an extra fine wire at a hot- rolled state and to provide a method for producing the same. SOLUTION: Steel having a composition containing 0.1 to 8.0% Si, in which the contents of C, N, O and S lie in the ranges limited by C+N+O+S<0.015%, and the balance Fe with inevitable impurities is heated at 850 to 1,300 deg.C and is subjected to hot rolling in which finish rolling temperature is <1,000 deg.C to control the ferrite grain size to <=50 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel material for an electromagnetic steel wire used for a high-frequency iron core or a reactor, and more particularly to a steel material for an electromagnetic steel wire having excellent drawability to a very fine wire in a cold state. It relates to the manufacturing method.

[0002]

2. Description of the Related Art Transformers and reactors are generally
It is manufactured by cold stamping a high Si electromagnetic steel sheet into a predetermined shape and laminating them. These transformers and reactors are required to reduce eddy current loss and reduce the amount of copper wire used in order to achieve higher efficiency. Recently, they have been designed to have an arbitrary shape in order to achieve further miniaturization. There has been a demand for electromagnetic steel materials capable of doing this.
In order to respond to such a request, the inventors have filed Japanese Patent Application No.
Japanese Patent Application No. -142777 and Japanese Patent Application No. 11-135966 propose an electromagnetic steel wire in which an electromagnetic steel material is ultra-fine to a diameter of about 0.1 to 0.5 mm. According to this proposal, the magnetic characteristics can be dramatically improved, and the degree of freedom in designing transformers and reactors can be ensured.

[0003] In order to manufacture such ultra-fine electromagnetic steel wires on an industrial scale, it is necessary that the wire material as a steel wire material or a steel material such as a steel bar has good wire drawing workability. Steel materials generally contain a large amount of Si or the like, and thus have poor wire drawing workability, and it is extremely difficult to work to ultrafine wires. Incidentally, with respect to the technology for manufacturing electromagnetic steel wires, see Japanese Patent Laid-Open No.
Discloses a method for manufacturing a wire for a soft magnetic material.

[0004]

However, as a result of examination by the inventors, even if the prior art disclosed in the above-mentioned publication is used, disconnection frequently occurs in the wire drawing (cold wire drawing) process, and 0.1%
It was found that it was difficult to wire-draw to an ultra-fine wire of ~ 0.5 mmφ. In addition, satisfactory magnetic properties, especially iron loss properties, could not be obtained with this disclosed technique.

Accordingly, the present invention is to solve the above-mentioned problems of the prior art, and to propose a steel material for an ultra-fine electromagnetic steel wire having good magnetic properties. An object of the present invention is to provide a steel material for an electromagnetic steel wire excellent in wire drawing workability to a wire and a method for manufacturing the same. Further, the present invention provides a steel material for an electromagnetic steel wire, which is advantageous in terms of manufacturing cost and which is hot-rolled (in a hot-rolled state without annealing) and has drawability, and a method for manufacturing the same. The purpose is to do.

[0006]

Means for Solving the Problems To achieve the above object, the present inventors pursued the causes of the difficult workability of a steel material for a magnetic steel wire having a high Si content and obtained the following knowledge. That is, Si
In a steel material to which is added, slip deformation is difficult, twin deformation is likely to occur at the time of wire drawing, brittle fracture occurs starting from the twin, and the wire breaks at the time of wire drawing. In order to suppress breakage due to brittle fracture caused by such a mechanism, it is effective to secure a material temperature of 260 ° C or more during wire drawing. However, wire drawing at such a high temperature is industrially required. It is difficult. Therefore, the inventors further focused on the fact that the brittle fracture of ferritic steel is affected by the crystal grain size, and adjusted the ferrite crystal grain size by changing the hot rolling conditions in various ways, and The relationship between the wire drawing property and the wire drawing workability was investigated in detail. As a result, it has been found that when the ferrite crystal grain size is reduced to a specific value or less (specifically, 50 μm or less), the wire drawing workability is greatly improved. It was also found that impurities (C, N, O and S) in the steel had a large effect on the drawability.

The present invention has been completed based on such findings, and the gist configuration thereof is as follows. (1) Si: 0.1 to 8.0%, the content of C, N, O and S is in a range limited by C + N + O + S <0.015%, and the balance is a steel composition comprising Fe and unavoidable impurities. And a ferrite crystal grain size of 50 μm or less.

(2) In the above (1), the steel composition further comprises C
A steel material for an electromagnetic steel wire having excellent drawability, characterized by having a composition containing 0.1 to 15.0% of r.

(3) Si: 0.1-8.0%
Content of C, N, O and S is C + N + O + S <0.015
%, With the balance consisting of Fe and unavoidable impurities heated to 850-1300 ° C and hot rolled at a finish rolling temperature of less than 1000 ° C. Method for producing steel for electromagnetic steel wire with excellent characteristics.

(4) The method for producing a steel material for an electromagnetic steel wire excellent in wire drawability according to the above (3), wherein the steel composition further contains 0.1 to 15.0% of Cr.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the reason why the composition of steel in the present invention is limited to the above range will be described. Si: 0.1 to 8.0% Si is an element necessary for an electromagnetic steel wire as a component for improving iron loss characteristics. However, if added less than 0.1%, good electromagnetic characteristics cannot be obtained. On the other hand, if it exceeds 8.0%, not only wire drawing in the cold, but also hot working becomes difficult.
%.

C + N + O + S <0.015% C, N, O and S are harmful elements that lower the magnetic properties and the wire drawing workability, and therefore need to be reduced as much as possible. Total content of these components C + N + O + S
When the content is 0.015% or more, the above-mentioned adverse effects are remarkably exhibited. Therefore, the total amount of these components is less than 0.015%.

Cr: 0.1 to 15.0% Cr is an element that improves magnetic properties, reduces the amount of C solid solution in ferrite, and improves drawability. It is added when further improvement is required. Such an effect is small when it is less than 0.1%, while if it exceeds 15.0%, it is saturated and no further effect is obtained. Therefore, when Cr is added, 0.1 to 15.0
Perform in the range of%.

Ferrite Crystal Particle Size If the ferrite crystal particle size is large, as described above, breakage due to brittle fracture is likely to occur, and it becomes difficult to draw a fine wire at room temperature. This tendency is observed when the crystal grain size is 50
If it exceeds μm, it rapidly increases, so in the present invention, the ferrite crystal grain size is limited to 50 μm or less. The shape and shape of ferrite grains in the hot-rolled steel for drawing
The distribution of the particle diameters is almost the same in the region from the surface to the 1/4 diameter, but is larger in the central part. In consideration of this distribution, the crystal grain size defined in the present invention refers to an average value measured at a 直径 diameter portion from the surface in the longitudinal section as it is hot rolled.

The steel material for an electromagnetic steel wire according to the present invention is obtained by continuously casting or ingot / sparging the molten steel adjusted to the above-mentioned composition.
After the bloom is formed, the billet is formed by billet rolling, and the billet is heated and then hot-rolled to a steel wire or a bar. If the cross-sectional dimension of the steel material for an electromagnetic steel wire obtained by hot rolling is usually in the range of 4.0 to 6.0 mmφ, it is preferable from the viewpoint of reducing the cold drawing amount in the subsequent step. In the above-described process of manufacturing the steel material for an electromagnetic steel wire, in order to control the ferrite crystal grains to the grain size specified in the present invention, it is particularly necessary to set the heating temperature and the finish rolling temperature in the following ranges.

Heating temperature: 850 to 1300 ° C. The heating temperature for rolling to a steel material for ultra-fine wire (steel wire or steel bar) is in the range of 850 to 1300 ° C. At temperatures below 850 ° C, deformation resistance is high and hot rolling becomes difficult, while at temperatures above 1300 ° C, the initial grain size becomes coarse, and finally the ferrite grain size of 50μm or less Is no longer possible.

Finish rolling temperature: less than 1000 ° C. The finish rolling temperature of hot rolling is also an important requirement of the present invention. At a finish rolling temperature of 1000 ° C or more, it becomes difficult to secure a ferrite crystal grain size of 50 μm or less.
Hot rolling at a finish rolling temperature of less than ° C. However, if the finish of the hot rolling is too low, the deformation resistance is increased and the dimensional accuracy of the rolled material is reduced.
Preferably, the temperature is set to 00 ° C.

By rolling under the above-mentioned conditions, a steel material for an electromagnetic steel wire having a ferrite crystal grain size of 50 μm or less as hot rolled can be manufactured. It is desirable to consider the temperature and the cooling rate after winding. In other words, the temperature range is set to 700 to 950 ° C. because it greatly affects the formation of the winding temperature structure. If the cooling rate is too high, the material is cracked by thermal stress, so the range is 10 ° C./sec or less. It is desirable.

[0019]

The present invention will be specifically described below with reference to examples.
Steel consisting of the chemical components shown in Table 1 and the balance substantially consisting of Fe was smelted in a converter, passed through continuous casting and billet rolling,
It was rolled into a billet of φ. This billet was heated and hot rolled under the conditions shown in Table 2 to obtain a 5.5 mmφ steel wire. The thus obtained steel material for an electromagnetic steel wire having a diameter of 5.5 mm was tested for ferrite crystal grain size and drawability, and iron loss was measured for a coil formed by using an ultrafine wire after drawing. Each test method is described below.

[0020]

[Table 1]

Ferrite crystal grain size A sample for an optical microscope is collected from a steel wire rod, and a 直径 G05 position is measured at a quarter diameter position from the surface of the longitudinal section.
The measurement was performed according to the cutting method according to No. 52. -Wire drawing workability After a pickling lubrication treatment and a lubrication treatment were applied to a steel wire rod, cold drawing was performed in the following order (1) to (3) using a continuous drawing machine. (1) Wire drawing to 1.0mmφ using a carbide die (lubricant is powdered metal soap, wire drawing reduction rate per pass is 15 to 25)
% / Pass, final drawing speed is 300 m / min) (2) Further lubrication treatment is applied, and wet continuous drawing is performed to 0.56 mmφ using a diamond die (drawing reduction rate per pass is 15 to 20). % / Pass, final drawing speed 100 m / min
(3) Perform lubrication again and use diamond dies.
Wet wire continuous drawing up to 0.10mmφ (drawing reduction rate per pass is 15-20% / pass, final drawing speed is 100m / min). The drawing limit was determined from the drawing strain ε. here,
ε = 2ln (D ₀ / D). However, D is the diameter of the wire at the time of break occurrence, D ₀ is the initial diameter of the wire (5.5 mm [phi]).・ The ultra-fine wire that could be drawn to a core loss of 0.10mmφ was annealed at 700 ° C × 5min, then an insulating coating was applied, and 0.10mmφ × 1m
An ultrafine wire having a length was formed into a coil having a diameter of 20 mm. This coil was measured for iron loss at a frequency of 10 kHz and a maximum magnetic flux density of 0.1 T by a method based on JIS C 2552.

The results obtained are summarized in Table 2. Table 2
From, the component composition is in the range of the invention, and the ferrite crystal grain size obtained by hot rolling under appropriate conditions was 50 μm or less, all of the steel wire rods of the invention example could be drawn to 0.10 mmφ without any problem . In addition, the core formed after drawing had low iron loss and showed good results. It can also be seen that steels B and C, which have high amounts of Cr and Si added, have better iron loss than A. On the other hand, even in the case where the component composition was within the range of the invention, in Comparative Examples in which the conditions of hot rolling were not appropriate and the ferrite crystal grain size was outside the range of the invention, the wire was broken at 4.60 to 5.20 mmφ. In steels D and E whose component compositions are out of the range of the invention, even if the ferrite crystal grain size is 50 μm or less, wire breakage occurs and wire drawing workability is poor. The loss was high and defective.

[0023]

[Table 2]

[0024]

As described above, according to the present invention,
It is possible to provide a steel material for an electromagnetic steel wire that can be easily drawn in the cold state to a wire drawing workability in the cold state, particularly to an ultra-fine wire of 0.1 to 0.5 mmφ. Can be manufactured. Further, according to the present invention, since such excellent wire drawing property is maintained as it is during hot rolling, it is not necessary to perform annealing before wire drawing, thereby improving production efficiency and production cost. Greatly contributes to the reduction of Therefore, according to the present invention, it is possible to provide a new electromagnetic steel wire suitable for a particularly small iron core such as a transformer or a reactor at low cost.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Atsuto Honda 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. 1-chome (without address) Mizushima Works, Kawasaki Steel Corporation F-term (reference) 5E041 AA02 AA19 CA02 HB07 NN01 NN06 NN18

Claims (4)

[Claims] (1) Si: containing 0.1 to 8.0%;
The content of S, O and N is in a range limited by C + N + O + S <0.015%, and the balance is a steel composition comprising Fe and unavoidable impurities, and a ferrite crystal grain size of 50 μm.
A steel material for an electromagnetic steel wire excellent in wire drawing work, characterized by the following. 2. The steel according to claim 1, wherein the steel composition further comprises Cr
Characterized by having a composition containing 0.1 to 15.0%. 3. Si: 0.1 to 8.0%, and C,
The contents of S, O and N are limited by C + N + O + S <0.015%, and the balance is made of steel consisting of Fe and unavoidable impurities. A method for producing a steel material for an electromagnetic steel wire having excellent drawability, characterized by cold rolling. 4. The method according to claim 3, wherein the steel composition further comprises:
A method for producing a steel material for an electromagnetic steel wire having excellent drawability, characterized by containing 0.1 to 15.0% of Cr.