JP3437487B2 - Manufacturing method of clad material for induction heating - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a temperature-sensitive magnetic material and Cu.
The present invention relates to a method for producing a clad material for induction heating, which is obtained by clad with a good heat conductive metal material containing as a main component.

[0002]

2. Description of the Related Art For example, Japanese Patent Application Laid-Open No. 4-220990 and Japanese Patent Application Laid-Open No. 4-220990 disclose heating / heat-retaining plates, pots, inner pots, and containers used in induction cookers, heaters, and the like that utilize induction heating.
As described in Japanese Patent No. 242093, it is formed of a clad material for induction heating in which a temperature-sensitive magnetic material whose magnetic permeability changes with temperature and a metal material such as aluminum having good thermal conductivity are joined. The clad material was manufactured by cold pressure welding at a reduction rate of 70% or more.

The magnetic permeability of the temperature-sensitive magnetic material changes rapidly near the Curie point, becomes non-magnetic at a temperature sufficiently above the Curie point, and eddy current loss due to the alternating magnetic field from the induction heating coil is reduced. Since the heating output is reduced, self-temperature control is possible and it is a suitable material for this kind of heating member. However, since the temperature-sensitive magnetic material itself has a low thermal conductivity, the temperature distribution will be uneven when used alone.Therefore, the temperature-sensitive magnetic material is clad with a metal material such as aluminum, which has excellent thermal conductivity. It is a translation. By the way, 38wt
The thermal conductivity of the temperature-sensitive magnetic material formed of the% Ni-8 wt% Cr-Fe alloy is about 0.03 cal / cm · s · ° C, while the thermal conductivity of aluminum is 0.56 cal / cm · s ·. It is about ℃.

[0004]

As described above, in order to ensure the uniform heating of the induction heating member, it is not possible to use the temperature-sensitive magnetic material alone, and it is essential to clad a good heat-conducting metal material to this. However, in the process of investigating the quality of the clad material for induction heating, the present inventor found that the temperature-sensitive magnetic material after clad drastically deteriorated in temperature controllability as compared with that before clad material. . From the viewpoint of magnetic properties, the cause of the decrease in temperature controllability was described, and it was found that the temperature change rate dμ / dT of the magnetic permeability at the Curie point was drastically decreased by the cladding.

That is, FIGS. 3 (A) and 3 (B) are graphs showing the measurement results of the magnetic permeability with respect to the temperature of the temperature-sensitive magnetic material before and after the cladding, but as shown in FIG. 3 (A), before the cladding. Temperature change rate of magnetic permeability μ at Curie point dμ /
Even if the dT is large, the dμ / dT sharply decreases after the cladding, as shown in FIG.
For example, in the case of a temperature-sensitive magnetic material composed of 38 wt% Ni-8 wt% Cr-Fe alloy, dμ / curie point of the temperature-sensitive magnetic material that is magnetically annealed before the cladding to remove processing strain.
Although the dT is 10 or more, the dμ / dT at the Curie point of the temperature-sensitive magnetic material forming the clad material pressed at the conventional reduction rate is reduced to about 6. However, the value of dμ / dT is a value with respect to relative magnetic permeability when the maximum value of magnetic permeability before and after the Curie point is 100 and the minimum value is 1.

As described above, in the temperature-sensitive magnetic material after clad, the dμ / dT at the Curie point is drastically decreased, and the temperature controllability of the temperature-sensitive magnetic material with respect to the temperature change is remarkably deteriorated. Have been forced to use at the expense of.

The present invention has been made in view of the above problems, and is a method for producing a clad material for induction heating having excellent temperature controllability, which can effectively utilize the magnetic characteristics originally possessed by the temperature-sensitive magnetic material. Is provided.

[0008]

DISCLOSURE OF THE INVENTION According to the present invention, as a result of an intensive study on the relationship between the rolling reduction rate and the dμ / dT at the Curie point when the temperature-sensitive magnetic material and the good thermal conductive metal material are pressure-welded, At the reduction rate, d due to processing strain associated with the reduction
It was found that μ / dT deteriorates sharply. The present invention has been completed based on such findings. That is, in the method for producing the clad material for induction heating according to the present invention as set forth in claim 1, after the temperature sensitive magnetic material whose magnetic permeability changes with temperature and the good heat conductive metal material are pressed together, the temperature sensitive magnetic material The magnetic annealing is performed by heating at a temperature not lower than the recrystallization temperature and lower than the melting point of the good thermal conductive metal material so as to remove processing strain existing in the temperature-sensitive magnetic material.

According to the present invention, the temperature-sensitive magnetic material is present in the temperature-sensitive magnetic material after being pressed into contact with the good heat-conductive metal material and then heated at a temperature not lower than the recrystallization temperature and lower than the melting point of the good heat-conductive metal material. Since the magnetic annealing is performed to remove the processing strain, the deterioration of the temperature change rate dμ / dT of the magnetic permeability at the Curie point due to the processing strain introduced during the pressure welding is eliminated, and the feeling of forming the clad material is eliminated. When the maximum value of the magnetic permeability before and after the Curie point of the warm magnetic material is 100 and the minimum value is 1, the temperature change rate of relative magnetic permeability dCu / dT at the Curie point of the temperature sensitive magnetic material is 10 or more, It is preferably 15 or more, and more preferably 20 or more, and a clad material having good temperature controllability that effectively utilizes the magnetic characteristics originally possessed by the temperature-sensitive magnetic material can be easily manufactured.

As a pressure welding method used in the present invention, roll pressure welding in which pressure is applied by passing a superposed material between a pair of rolls is preferable because it is easy to carry out and is excellent in productivity. Cold welding, warm welding, 1 × 1
Any method of vacuum pressure contacting in a vacuum atmosphere of 0 ^-1 Torr or less may be used. Further, the rolling reduction may be set so that the joining force is improved during the magnetic annealing, so that the joining force between the temperature-sensitive magnetic material and the good thermal conductive metal material can be carried. Since a certain degree of bonding force is required when press-molding the clad material, it is held for several minutes at a temperature lower than the lower melting point of the temperature-sensitive magnetic material or the good thermal conductive metal material after pressure welding. Magnetic annealing may be performed after diffusion annealing is performed to improve the bonding strength and press forming is performed. Diffusion annealing may be carried out in a tunnel furnace provided in the transfer line as usual.

The thickness of the temperature-sensitive magnetic material and the heat-conductive metal material before the pressure welding is preferably 0.03 to the thickness after the pressure welding so as to secure the penetration depth of the magnetic flux in the temperature-sensitive magnetic material. 0.5
mm, and for a good heat conductive metal material, 0.3 to 6.0 mm in order to ensure good temperature uniformity,
The material thickness may be set in consideration of the reduction rate.

The dμ / dT is a value for the relative magnetic permeability when the maximum value of the magnetic permeability before and after the Curie point is 100 and the minimum value is 1, and the minimum value indicates a non-magnetic state. , The relative magnetic permeability is 1. The reason why dμ / dT is determined with respect to the relative value of the magnetic permeability is that the magnetic permeability greatly differs depending on the components of the temperature-sensitive magnetic material and the measurement conditions, and in the present invention, the absolute value of the magnetic permeability does not matter. Since the change with temperature is a problem, dμ / dT is defined with respect to the relative value of magnetic permeability. The maximum and minimum values of permeability are usually
(Curie point −100) ° C. to (Curie point +50) ° C.
Since it appears in this temperature range, it is practically possible to measure in this temperature range.

In the method for producing the clad material for induction heating according to the second aspect, the temperature-sensitive magnetic material is a temperature-sensitive magnetic metal having a Curie point of 40 to 600 ° C., and the good heat-conductive metal material is Cu. It is formed of a Cu-based metal as a main component.

According to the present invention, since the Curie point of 40 to 600 ° C. is used as the temperature-sensitive magnetic material, it is possible to realize temperature control within a temperature range suitable as a cooking temperature. An example of the temperature-sensitive magnetic material having such a Curie point is a Fe—Ni alloy (preferably Ni ≧ 30).
wt%), Fe-Ni-Cr alloy (preferably Ni: 30)
~ 65 wt%, preferably Cr≤20 wt%), Ni-Cu
Alloy (preferably Cu ≧ 35 wt% or more) or pure Ni
Can be raised.

On the other hand, the Cu-based metal whose main component is Cu is
It is supplied to the market in large quantities, has excellent thermal conductivity at low cost, and its melting point is higher than the recrystallization temperature of the temperature-sensitive magnetic material having a Curie point of 40 to 600 ° C, facilitating magnetic annealing after pressure welding. It can be carried out. Therefore, by using the Cu-based metal as the good heat conductive metal material, it is possible to easily obtain a low-cost clad material having excellent temperature controllability and temperature uniformity. As the Cu-based metal, in addition to pure Cu, preferably various Cu containing 90 wt% or more of Cu.
Alloys can be used.

The above Fe-Ni alloy, Fe-Ni-
In the case of Cr alloy, Ni—Cu alloy or pure Ni, the recrystallization temperature is 700 ° C. or higher, and the melting point of the Cu-based metal is generally higher than 1000 ° C., so the lower limit of magnetic annealing is 700 ° C.
The temperature is preferably 850 ° C., and the upper limit is 1000 ° C., preferably 900 ° C. The heating time may be set so as to obtain a recrystallized structure from which the processing strain is removed, and is preferably 10 minutes or longer, more preferably 15 minutes or longer. Further, from the viewpoint of improving productivity, it is preferably within 4 hours, more preferably within 3 hours.

[0017]

EXAMPLE Temperature-sensitive magnetic metal (38 wt% Ni-8 wt% Cr-
Fe alloy, Curie point 172 ℃) hoop material, 99.
The 9% pure Cu hoop material was overlaid, the rolls were pressure welded with the bonding method and the rolling reduction shown in Table 1 below, and then magnetic annealing was performed in a batch type annealing furnace under the conditions shown in the table. As shown in, the induction heating clad material 1 in which the good thermal conductive metal material 3 made of pure Cu is bonded to the temperature-sensitive magnetic material 2 was manufactured. The thickness of the temperature-sensitive magnetic material 2 of sample No. 1 is 0.1 mm, good heat
The conductive metal material 3 had a thickness of 1.0 mm.

Width 20 mm, length 30 mm from each clad material 1
Cut off the strip of material, attach a measuring coil (primary coil, secondary coil) around it, and install it in the heating furnace.
Gradually raise the temperature from room temperature to Curie point + 50 ° C. 1
The voltage induced in the secondary coil when a reference current is applied to the secondary coil is measured at each temperature, and the magnetic permeability is calculated based on this voltage. The maximum value is 100 and the minimum value is 1, and the Curie point is set. Relative temperature change rate of magnetic permeability dμ / dT
I asked.

Further, the clad material 1 was cut into a size of 200 mm, and a temperature control test was carried out using the cut material in the following manner. As shown in FIG. 2, a heating and heat insulating plate made of the clad material 1 was placed on the high frequency coil 11, and a non-magnetic container (stainless steel container) 12 was placed thereon. The container 12 was filled with edible oil 13, an inverter power source with a frequency of 30 kHz and a maximum electric power of 1200 W was connected to the coil 11, and the temperature of the edible oil 13 in the container 12 was measured. Immediately after the voltage is applied, the temperature of the edible oil 13 rises rapidly, but eventually it reaches a constant temperature near the Curie point. The temperature control range in this steady state is measured and ± 5
When the temperature was controlled within 0 ° C, it was rated as excellent, when it was controlled within ± 10 ° C, it was rated as good, and when it was out of ± 10 ° C, it was rated as bad. The results of these measurements are also shown in Table 1.

[0020]

[Table 1]

From Table 1, in the clad materials of the invention examples, dμ / dT at the Curie point is 15 or more, and good temperature controllability is obtained. In particular, in Sample Nos. 4 and 5 in which magnetic annealing was performed at 850 ° C. or higher, excellent temperature controllability was obtained despite cold welding at a high pressure reduction rate of 70%.

On the other hand, in No. 6 of the comparative example, the rolling reduction is 70
%, And the relative magnetic permeability dCu / dT at the Curie point is 6 because the magnetic annealing is not performed, and the temperature controllability is also significantly reduced.

[0023]

According to the method for manufacturing the clad material for induction heating of the present invention, since the temperature-sensitive magnetic material and the good heat-conducting metal material are magnetically annealed after being pressed, the temperature-sensitive magnetic material is produced regardless of the reduction rate. The relative magnetic permeability dμ / dT at the Curie point of is 1
It can be set to 0 or more, the original magnetic characteristics of the temperature-sensitive magnetic material can be effectively used, and a clad having good temperature controllability can be easily manufactured, which improves mass productivity and productivity. Is also excellent.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a clad material for induction heating according to the present invention.

FIG. 2 is an explanatory diagram of an implementation point of a temperature control test of a clad material for induction heating performed in an example.

FIG. 3 is a graph (A) illustrating the effect of temperature on the magnetic permeability of the temperature-sensitive magnetic material before clad, and the effect of temperature on the magnetic permeability of the temperature-sensitive magnetic material that constitutes the conventional induction heating clad material. Graph (B).

[Explanation of symbols]

1 Clad material 2 Temperature-sensitive magnetic material 3 Good heat conductive metal material

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI B23K 103: 22 B23K 103: 22 (56) References JP-A-9-237677 (JP, A) JP-A-9-129362 (JP , A) JP-A-9-108851 (JP, A) JP-A-9-103360 (JP, A) JP-A-8-309561 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) B23K 20/00-20/26

Claims (2)

(57) [Claims] 1. A temperature not lower than a recrystallization temperature of the temperature-sensitive magnetic material and lower than a melting point of the good heat-conductive metal material after pressure-contacting the temperature-sensitive magnetic material whose magnetic permeability changes with temperature and the good heat-conductive metal material. A method for producing a clad material for induction heating, which comprises magnetic annealing for heating to remove processing strain existing in a temperature-sensitive magnetic material. 2. The temperature-sensitive magnetic material is a temperature-sensitive magnetic metal having a Curie point of 40 to 600 ° C., and the good heat conductive metal material is Cu.
The method for producing a clad material for induction heating according to claim 1, wherein the clad material is formed of a Cu-based metal containing as a main component.