JPH01173595A - Heating material for high frequency induction electromagnetic cooker excellent in heating efficiency - Google Patents

Abstract

PURPOSE:To improve heating efficiency by using a material which has a secondary crystal structure of Fe base in which total content of Pi, P, Al, Sn, Mn, V and Cr is less than 0.2wt.% and the average crystal granule diameter is more than 3mm. CONSTITUTION:Eddy current flowing in a magnetic substance material depends greatly on a crystal granule diameter and electric resistivity. A material which has a secondary recrystal structure of Fe base in which the total content of Si, P, Al, Sn, Mn, V, Cr is less than 0.2wt.% and the average crystal granule diameter is more than 3mm is cast into a slab and is annealed at need after usual hot rolling and then is formed into the final plate thickness through the usual cold rolling and annealed for decarbonization at need and next is annealed for recrystalization. Hereby, a material excellent in heating efficiency can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a magnetic heat generating material with excellent heat generation efficiency for use in an electromagnetic cooker equipped with a high frequency induction heating device.

<Prior art> An electromagnetic cooker generally has a heat-generating material made of a magnetic material placed on a top plate at the bottom of the cooking container, and causes the cooking container to generate heat by passing an eddy current through it due to electromagnetic induction. There is. The electromagnetic induction effect of a cooking appliance is normally generated by rectifying a commercial frequency alternating current, converting it to a high frequency through an inverter, and flowing it through a predetermined coil to generate a high frequency magnetic field.

In addition to being highly safe and clean, electromagnetic cooking is also economical because it generates heat directly, and is expected to further increase in demand.

By the way, in order to improve thermal efficiency, it is only necessary to increase the heat generation amount of the magnetic heat generating material, and in order to do this, it is necessary to allow more eddy current generated by current induction to flow through the magnetic heat generating material within the range of the rated capacity. good.

However, conventionally, ordinary iron and stainless steel have been used as magnetic heat generating materials, and this has caused problems in terms of thermal efficiency.

<Problems to be Solved by the Invention> The present invention provides a heat generating material for a high frequency induction heating electromagnetic cooker that has excellent eddy current heat generation efficiency.

Means for solving problems〉 The present invention provides Si+P, /V, Sn, Mn,
It is characterized by having an Fe-based secondary recrystallized structure with a total content of V and Cr of 0.2wt% or less and an average crystal grain size of 3ffIIIl or more.
High frequency 111M1ill is a heat generating material for medical equipment.

As mentioned above, in order to improve the heating effect caused by the eddy current of an electric ift cooker, it is sufficient to allow a large amount of eddy current to flow through the magnetic material. After conducting research on magnetic materials that generate a large amount of heat due to eddy currents, we discovered that the eddy currents flowing through magnetic materials are largely dependent on the crystal grain size and electrical resistivity.

The present invention will be specifically explained below based on experimental results.

In Figure 1, C: 0.03%, Si: 0.04%
, p: o, ot%, Mn: 0.05%, s: o,
Molten steel consisting of o2% and other unavoidable impurities and Fe is made into a slab by continuous casting, and is then rolled to 2.3a by normal hot rolling.
The hot-rolled steel strip was made into a hot-rolled steel strip with a thickness of m, then annealed at 1000°C for 30 seconds, and then decarburized and primary recrystallized at 820°C for 2 minutes to a cold-rolled plate finished to a thickness of 0.35an by one cold rolling. The material after being subjected to continuous annealing that also serves as
This figure shows the iron loss at a high frequency of 20 kHz for a material that was annealed at 80°C for 30 hours and obtained a secondary recrystallized structure by using fine MnS precipitates.

As is clear from this figure, at any magnetizing force (H), the core loss value of the material with the secondary recrystallized structure is higher than that of the conventional material with the primary recrystallized structure. It can be said that the higher the iron loss value, the better the heat generation efficiency of the material.

The average crystal grain size of this material having a secondary recrystallized structure is 7 rm'? ! The material with primary recrystallization MwR is 0.05 an. From these, by secondary recrystallization,
It can be seen that the coarser the crystal grains, the higher the iron loss value, making it suitable as a heat-generating material. The core loss value increases as the crystal grains become coarser because the movement speed of domain walls during magnetization increases as the magnetic domain width increases, which increases eddy currents. Also, since this eddy current increases in proportion to the square of the frequency, it
When used at high frequencies near z, coarsening the crystal grain size is effective as a means of increasing heat generation efficiency. suitable 2
Since the secondary recrystallized grain size is an average grain size of 3IIll1 or more,
In the present invention, the average grain size of secondary recrystallization is limited to 3 mm1 or more.

Next, the reason for limiting the component composition will be described. The smaller the electrical resistivity of the eddy current flowing through the magnetic material, the better (current,
As a result, Sl, P, kl, and Sn have a large effect of increasing electrical resistivity because their calorific value increases.

It is preferable that the elements Mn, V, and Cr be as small as possible. Therefore, the total amount of these seven elements is limited to 0.2 wt% or less.

In addition, nitrides of /V, B, Ti, and Nb have inhibitor functions to easily cause secondary recrystallization.

V, Cr carbonitride, MnS, MnSe and Sb,
27 containing about 0.1 to 0.01 wt% of one or more of PbnSn+Bi, As, Te, etc. can be produced.

Although the heat generating material of the present invention is an Fe-based magnetic material, it may also contain Ni+Co, which is an iron group element and is ferromagnetic.

The general manufacturing method for the material of the present invention is to adjust the molten steel composition to a predetermined composition, then cast it into a slab, perform normal hot rolling, annealing if necessary, and then perform normal cold rolling to achieve the final plate thickness. year,
Decarburization annealing is performed if necessary, followed by primary recrystallization annealing preferably at 550°C or higher for 15 seconds or more, followed by secondary recrystallization annealing preferably at 800°C or higher and below the A3 transformation point for 10 minutes or more. It is intended to provide

Normally, materials with secondary recrystallization tend to exhibit a texture with a specific orientation, but when used as a product, local temperature unevenness occurs on the heating surface, so in order to generate heat uniformly, it is necessary to is preferably random.

<Example> A sea bream having the composition shown in Table 1 was made into a hot rolled steel strip with a thickness of 2.3 mm by normal hot rolling, then annealed at 1100°C for 30 seconds, and then cold rolled once. The material was finished to a thickness of 0.35 an, then subjected to continuous annealing at 820°C for 2 minutes, which also served as decarburization and primary recrystallization, and then annealed at the temperature and time shown in the table to reduce the grain size of secondary recrystallization. It was adjusted. The iron loss at 20kHz is also shown.

It can be seen that the material of the present invention has a higher core loss value at high frequencies than the comparative materials, and has excellent heat generation efficiency due to overcurrent.

<Effects of the Invention> As stated above, this invention allows electricity to be increased by 1ffil! It is possible to obtain magnetic heat generating materials with excellent heat generation efficiency for medical equipment.

[Brief explanation of the drawing]

FIG. 1 shows the iron loss at 20 kHz of a material having a primary recrystallized structure and a material having a secondary recrystallized structure. Figure 1

Claims (1)

[Claims] A heat generating device characterized by having an Fe-based secondary recrystallized structure with a total content of Si, P, Al, Sn, Mn, V, and Cr of 0.2 wt% or less and an average crystal grain size of 3 mm or more. High-efficiency heat-generating material for high-frequency induction heating electromagnetic cookers.