JPS5891121A - Production of high-tensile hot-rolled steel plate having high magnetic flux density - Google Patents

Abstract

PURPOSE:To produce a high-tensile hot-rolled steel plate having high magnetic flux density and high strength by subjecting a steel slab contg. specific ranges of C, Mn, Si, Al, S, N, Ti to heating, hot rolling and coiling under respectively specific conditions. CONSTITUTION:A steel slab contg., by weight, 0.02-0.06%C, 0.3-1.2% Mn, <=0.10% Si, <=0.10% Al, <=0.02% S, <=0.01% N, and 0.05-0.30% Ti and consisting of the balance Fe with unavoidable impurities is heated to >=1,200 deg.C. Thereafter, the heated slab is hot-rolled at finish rolling temps. higher than the Ar3 transformation point and <=900 deg.C, and the hot-rolled steel plate is coiled at a 500-650 deg.C range. Thus, the steel plate for magnetic poles which has about >=50kg.f/mm.<2> tensile strength as hot-rolled and has magnetization characteristics of about >=1.5% at B25 magnetic flux density, about >=1.7T at B50 and about >=1.8T at B100 is produced inexpensively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a high tensile strength hot rolled steel sheet having a high magnetic flux density.

Generally, steel plates for magnetic poles used in rotating electric machines are required to have high magnetic flux density and high strength. However, conventional steel sheets for magnetic poles often contain relatively large amounts of C, Mn, and Si to ensure strength; for example, Cjo, 10%
As mentioned above, Mn: 1.3% or more and Si: 0.2% or more were normal. Although this increases the strength, it also has the disadvantage that magnetic permeability decreases, making it difficult to improve the performance of rotating electrical machines.However, as the demand for energy conservation has increased in recent years, improvements in the efficiency of rotating electrical machines have been desired, and in response to this demand, In order to achieve this, there is a strong demand for smaller and lighter rotors and faster rotation speeds by increasing the strength of rotor materials. However, since the range of applications of rotating electric machines is extremely wide, it is impossible to increase the strength of materials by using expensive alloying elements except in special cases. Therefore, there has been a strong demand for the development of materials that do not contain expensive alloying elements and have high magnetic flux density and high strength.

In order to meet the above requirements, an object of the present invention is to have a tensile strength of 50 f/- or more as hot-rolled, and a magnetic flux density of B3. 1.5T or more in Bwa, 1.7T or more% in B
B. . The purpose of the present invention is to provide a steel plate for magnetic poles having a tensile strength of 1.8T or more at low cost.

The gist of the present invention is as follows.

That is, tf ratio: CiO: 02-0.06%, grain: 10°3-1.2%, Si: 0.10% or less, At:
0.10% or less, S: 0.02% or less, N+0.01
% or less, Ti: 0.05 to 0.30%, the remainder consisting of Fe and unavoidable impurities.
A step of heating the heated slab to a temperature of 0° C. or higher;
r.

A high magnetic flux density characterized by comprising the steps of: hot rolling at a finishing rolling temperature above the transformation point and below 990°C; and winding the hot rolled steel sheet at a temperature range of 500 to 650°C. A method for producing a high tensile strength hot-rolled sheet having the following steps.

Details and embodiments of the invention will now be described with reference to the accompanying drawings.

It is known that it is effective to reduce impurities in steel to make it closer to pure iron in order to obtain a high magnetic flux density, which is the object of the present invention, but this does not ensure high strength. Among the impurities, interstitial atoms such as C and N have the most negative effect on the magnetic flux density.

These penetrate into the crystal lattice of Fe, increase lattice strain, and impede movement of magnetic domains. Although substitutional atoms such as SI%Mn also distort the crystal lattice, the effect is less than that of interstitial atoms such as C and N.

On the other hand, Ti and Nb are known as precipitation strengthening elements.

It is believed that V and Zr precipitate in steel as fine carbides or nitrides and prevent the movement of dislocations and strengthen the steel, but do not hinder the movement of magnetic domains. These elements fix C as a carbide and strengthen -, so they are effective for the purpose of the present invention. In particular, the present invention focuses on Ti because it is inexpensive and can improve strength with a small amount.

The reasons for limiting the above-mentioned steel components in the present invention are as follows.

C: C is the most effective element for obtaining high tensile strength and requires at least 0.02% for this purpose. However, as C increases, the magnetization characteristics deteriorate as shown in Figure 1.
．． It was limited to a range of 0.06%. -81: Sl is useful as a reinforcing element, but as shown in FIG. 2, it deteriorates the magnetization characteristics, so it is desirable to have less. However, in order to economically produce - as a reinforcing element with the minimum addition, it was decided to add 0.10% as an upper limit.

Mn: Mn is also an effective element for improving strength, but
As shown in the figure, the magnetization characteristics deteriorate. However, compared to Sl, the degree of deterioration is small, so at least 0.3% is required as a reinforcing element. However, if it exceeds 1.2%, the deterioration of the magnetization characteristics will be significant, so the upper limit is set at 1.2%.
It was limited to a range of 0.3 to 1.2%.

At: At is a necessary element for deoxidation, but if it exceeds 0.10%, it will cause coarsening of crystal grains and deteriorate the strength, as well as greatly deteriorating the magnetization characteristics, so it was limited to 0.10% or less. .

S: If S exceeds 0.02%, MnS-based inclusions increase and the magnetization characteristics deteriorate, so the upper limit was set at 0.02%.

N: N acts as an interstitial atom, distorting the crystal lattice and deteriorating the magnetization properties, and also combines with Ti, which is especially added in the present invention, to form TiN, which effectively increases the strength.
The upper limit was limited to 0.01% because the effect of

Ti: Ti is inexpensive, and when added in small amounts, it combines with C to form TiC and strengthens steel, so it is at least 0.05
% is required. Normally, in order to obtain sufficient strength for Cil, Ti is added in an amount more than four times the amount of C in terms of weight percent, but T
An increase in I causes surface flaws, and since the upper limit of C was set at 0.06%, the upper limit was set at 0.30%.

In addition to the above-mentioned components, the steel of the present invention consists of Fe and unavoidable impurities, and after melting this component steel, it is made into a slab through normal manufacturing processes such as continuous casting, ingot making, and blooming.

The slab is heated to 1,200°C or higher, either once it has been turned into a cold slab or as a hot slab. Usually 1200~
It is heated to a temperature range of 1400°C and then rolled. The reason why the heating temperature was set to 1200°C or higher was to promote the solid solution of T1, and this is because Ti is not sufficiently dissolved at a heating temperature of less than 1200°C. The upper limit is not particularly limited, but from the perspective of preventing scale loss and saving energy, it is 140
Heating to 0°C is unnecessary and uneconomical.

The above-mentioned slab heated to 1200°C or higher is hot rolled, and the finishing temperature is Ar, and the transformation temperature is set to 900°C or lower.

The finish rolling temperature was set to Ar and above the transformation point of TiC.
This is to ensure strength due to precipitation and to prevent deterioration of magnetic permeability due to residual strain, and this purpose cannot be achieved at a finish rolling temperature below the Arl transformation point.

Further, if the finish rolling temperature exceeds 900°C, the temperature is too high and the crystal grains of the steel sheet become coarse, making it impossible to obtain the necessary strength, so the upper limit of the finish rolling temperature was set at 900°C.

The hot-rolled plate according to the present invention after hot rolling is 500 to 6
Wind it into a coil at a temperature range of 50°C. Winding temperature 5
The reason why the temperature was set at 00 to 650°C is that the shape of the steel sheet tends to deteriorate at temperatures below 500°C (temperatures exceeding 650°C cause coarsening of the crystal grains of the steel sheet, and precipitation hardening due to Ti cannot be obtained). .

A high tensile strength hot rolled steel sheet with a high magnetic flux density could be obtained by such a manufacturing method.

Example Steel according to the present invention having the chemical composition shown in Table 1 1゜2.3,
4 and Comparative Steels 45, 6, 7, 8, and 9.10 were each melted in a converter and made into slabs through commonly performed steps.

The slabs were heated as shown in Table 1 (after heating to 1200°C or higher, then hot rolled at a finish rolling temperature of 900°C or higher than the transformation point) and rolled in a temperature range of 500 to 650°C. 1 Winding plate 1 on the coil at the temperature listed in table 1!
Hot-rolled steel sheets of L2.6 to 4.0 were manufactured.

Table 1 also shows the results of measuring the magnetization properties and tensile strength of each test material of the manufactured hot-rolled steel sheets. Furthermore, the relationship between the tensile strength and magnetic flux density of these moxibustion test materials is shown in FIG.

As is clear from Table 1 and Figure 4, the steels of the present invention all have high strength and excellent magnetic flux density;
The comparative steel was far inferior to the present invention in both Blm w BSo 181 (111 and tensile strength) and could not achieve the object of the present invention.

In this comparative test, the comparative steel was also rolled under the rolling conditions according to the present invention, so the influence of magnetization properties and strength was mainly due to the copper component, and the limited composition of the present invention was not found in the comparative steel composition. Component values that are outside the range, as well as test results that are insufficient in magnetic flux density or strength, are underlined. That is, comparison-sample material A
5 has high strength due to high C content but poor magnetization properties,
The sample material 46 has an extremely low carbon content, so although it has excellent magnetization characteristics, its strength is extremely low. In addition, sample material A7 is 84
' is too high, the magnetization properties of B are inferior, and specimen material A8
Although the strength is high because Mn is too high, BSo
,B. . Sample material A9 has poor magnetization properties and strength of 8116 + 8160 due to its high N content, and sample material 410 has excellent magnetization properties because it does not contain Ti'. The result is that the strength of the material is significantly inferior. In contrast, the steel of the present invention has 5
Strength of 0 ki-f/vxJ or more and magnetic flux density of 8
1.5T or more at 0, 1.71JJ at B, o:, Blm
This indicates that the hot-rolled steel sheet has excellent magnetization characteristics of 1.8 T or more and high strength.

In addition, magnetic flux density measurement 4i in one comparison test, JISC
2550.

As is clear from the above examples, the present invention reduces C, Si, Mn, and N, which have an adverse effect on magnetization characteristics, and also reduces Ti l! - The tensile strength is increased by adding the
kg-f/d or more, and the magnetization property is 1.5T or more using the magnetic flux density formula, and 1.7T or more at f3m%B
It was possible to produce a high tensile strength hot-rolled steel sheet with a high magnetic flux density of 1.8 T or more at +611 at an extremely low cost.

[Brief explanation of drawings]

Figure 1 is a diagram showing the effect of C on the magnetic flux density of the invention steel and comparative steel, Figure 2 is a diagram showing the influence of Si on the invention steel and comparative steel on magnetic flux density, and Figure 3 is a diagram showing the effect of Si on the invention steel and comparative steel on magnetic flux density. FIG. 4 is a diagram showing the influence of Mn in the present invention steel and comparative steel on magnetic flux density. FIG. 4 is a diagram showing the relationship between magnetic flux density and tensile strength in the present invention steel and comparative steel. Agent Takeo Nakaji Figure 1 C ■ Figure 2 Figure 3 Mn (S

Claims (1)

[Claims] (1) C+ 0.02-0.06% by weight, M
n: 0.3 to 1.2%, Si: 0.10% or less, At:
0.10% or less, S: 0.02% or less, N: 0.01%
Hereinafter, a steel slab containing 0.05 to 0.30% of Ti and the remainder consisting of Fe and unavoidable impurities was heated to 1200%.
a step of heating the heated slab to a temperature of ℃ or higher;
. A high magnetic flux density characterized by comprising a step of hot rolling between finish rolling layers at a temperature above the transformation point and below 900°C, and a step of winding the hot rolled steel sheet in a temperature range of 500 to 650°C. A method for producing a high-tensile hot-rolled copper plate having the following steps.