JPS6218008A - Heat treatment for amorphous alloy core - Google Patents

Abstract

PURPOSE:To obtain a proper cooling rate and to give excellent magnetic characteristics to a core by a method wherein, after a heat treatment of the core using amorphous alloy, the core is taken out of the furnace, left to stand in the air, and is cooled. CONSTITUTION:In a heat treatment of the core obtainable by laminating or winding amorphous alloys, the temperature rise to the prescribed point and the holding at this temperature are executed in the furnace with an atmosphere of inert gas. In cooling, the core is taken out of the furnace, left to stand in the air, and is cooled. Even in the case of a large core, cooling is completed in a short time at the cooling rate set proper to allow the core to have good magnetic characteristics. By this way, the cooling is shortened in time to avoid adverse effects due to oxidation, thereby attaining an effective cooling rate. As a result, the magnetic characteristics of the core can be significantly improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a method of heat treating an amorphous alloy core used in electrical equipment.

[Prior art and its problems]

Amorphous alloy magnetic materials have extremely superior magnetic properties compared to conventional crystalline alloy magnetic materials, so when applied to transformer cores, for example, they have the advantage of greatly reducing no-load loss. In addition, amorphous alloys can be made into thin strips by blowing the molten metal onto high-speed rotating rolls and cooling them extremely quickly, so they cannot be made by conventional melting.

Compared to crystalline alloys manufactured by forging, rolling, etc., it requires significantly fewer manufacturing steps and is superior in terms of energy savings, and there are great expectations for its practical application by taking advantage of both the material properties and manufacturing method. It is being

When such an amorphous alloy is used in the core of a transformer, it is evaluated comprehensively by taking into account not only the high magnetic flux density and small iron loss, but also the magnetic properties such as mechanical properties and heat treatment conditions. For example, Fe-B-8i alloy is known as one of them, and among them, the composition ratio is 92% Fe -
:(%B-5%Si etc. are suitable. In order to impart good magnetic properties to this amorphous alloy,
The amorphous alloy obtained by ultra-quenching must be subjected to excessive heat treatment, and the heat treatment conditions are held at 400 ° C in a magnetic field for 2 hours in an inert gas atmosphere such as nitrogen gas or argon gas. Subsequent cooling is done in a furnace to prevent oxidation of the amorphous alloy, and the cooling rate is 5℃.
, 4 is a good idea.

However, this heat treatment condition is such that good magnetic properties can be obtained when the heat treatment is performed on a relatively small core made of an amorphous alloy with a weight of about 1 Kf or less, and the heat treatment is performed on a core made of a large number of laminated layers of amorphous alloy. Since this is normal, actual large transformer cores have a large heat capacity, and therefore the cooling rate will naturally be slower than that of the shed sample.

For example, Figure 2 shows the Xt ratio of 92%Fe-3%B-5%Si.
Cooling rate and AC 50Hz when heat treating a relatively small wound core sample using an amorphous alloy.

This is a diagram showing the relationship with iron loss at 1.3 Tesla (T). Other heat treatment conditions were a holding temperature of 400°C in a nitrogen gas atmosphere, a holding time of 2 hours, and an applied magnetic field of 800 A DC in the circumferential direction. /fn. It can be seen from Fig. 2 that the iron loss becomes significantly larger when the cooling rate is slower than 2''C4.For example, in a small core with a core weight of about 0.59, the cooling rate is 4%, and the iron loss W1. 3150 can obtain a value of 0.16 wA, whereas the core weight of 10 Kf has a large heat capacity, so in the cooling process, the center part cools more slowly than the surface part in the furnace cooling process.
Door', CIQ Iron loss W 1.315G Ha 0.25
It becomes wA. Although Figure 2 shows the case of iron loss as a magnetic property, the relationship between the cooling rate of the iron core and the excitation power and various DC magnetic properties as well as iron loss is similar to that of iron loss when the cooling rate is slow. It has been confirmed that it affects people. Moreover, the same can be said not only for this Fe-B-8i-based amorphous alloy but also for other alloy-based amorphous materials used in iron cores as magnetic materials.

As mentioned above, conventional heat treatment methods cannot fully demonstrate the material properties of relatively heavy iron cores made of amorphous alloys, and the advantages of amorphous alloys have not been effectively utilized. . Therefore, a heat treatment method for increasing the cooling rate and improving magnetic properties is required for large cores as well as for small cores.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and its purpose is to obtain an appropriate cooling rate regardless of the size of the core when heat treating a core made of laminated or wound amorphous alloy, and to provide an excellent method. An object of the present invention is to provide a heat treatment method capable of imparting magnetic properties to an iron core.

[Key points of the invention]

The present invention focuses on the fact that when heat treating an iron core using an amorphous alloy, the effect of oxidation is small even if the iron core in a high temperature state is exposed to the atmosphere for a short period of time during the cooling process after heating and holding. The temperature is raised to a predetermined temperature and maintained at that temperature in a furnace with an inert gas atmosphere.When cooling, the core is taken out and left to cool in the atmosphere.Even large cores can be cooled in a short time. The cooling process was completed to achieve an appropriate cooling rate and to provide the core with good magnetic properties.

[Embodiments of the invention]

The present invention will be explained below based on examples.

2i amount ratio of amorphous alloy is 92%Fe −: (%1
Using the 3-5%5io) thin ribbon, a wound core with a weight of about 10K9 was prepared and heat treated. The common points with the conventional heat treatment conditions are that the temperature was raised to 400°C in a nitrogen gas atmosphere and held for 2 hours, and the applied magnetic field was 800 A/fn. It's photogenic. That is, in the present invention, after the iron core is heated and maintained, it is taken out from the furnace and left to cool in the atmosphere. In this way, the cooling rate of the iron core is much faster (compared to cooling in a furnace), and the magnetic properties are also improved.

The results are shown in Table 1, which also includes the amorphous alloy cores of 0.5 to 4 and 10 K9 weight 31 of the conventional method described above for comparison.

Table 1 Tooth 1 in Table 1 is the present example, and tooth 2. Ryu 3 is the conventional one, and when comparing these three methods, the method of the present invention is comparable to the cooling rate of the conventional small core, and the iron loss W1.315G is almost the same value, and appropriate heat treatment is not required. I can see what is being done. In the present invention, after heating, the material is allowed to cool in the atmosphere, but since the cooling rate If is 4''4, the temperature range up to 300°C where the cooling rate has the greatest effect on magnetic properties is small. It only takes 5 minutes, and within this amount of time, even if the core is exposed to the atmosphere, only the surface of the laminated core will be oxidized. Therefore, the inside of the core will not be oxidized and will remain healthy. gender is maintained,
The magnetic properties of the entire core can be sufficiently affected by heat treatment. On the other hand, when heating at elevated temperatures, the larger the iron core becomes, the more difficult it becomes to maintain rapid heating for a short period of time, and it takes a long time.At this time, oxidation of the iron core progresses in the atmosphere, degrading the magnetic properties. To prevent this, the iron core must be placed in an inert atmosphere when the temperature is raised. The present invention utilizes the fact that the influence of oxidation can be ignored even if the iron core is left in the atmosphere only during cooling.

Although FIG. 1 shows the core loss curve of the Nn2 core heat-treated according to the present invention in Table 1, %3 according to the conventional method in Table 1 is also shown for comparison. Figure 1 shows the relationship between the magnetic flux density of the iron core and the iron loss at 50Hz4, where curve A is 1'! The iron core 1 curve opening of No. 11 shows the characteristics of the iron core No. 2.

From the comparison between curve A and curve A, it can be seen that the iron core of the present invention has much smaller iron loss and that the heat treatment method is appropriately performed.

The above is true for laminated cores made by stacking many thin plates of amorphous alloy, which have exactly the same effect as wound cores, and also for small cores with a thickness of less than 1 in. It may also be carried out by leaving it for a while, in which case the cooling rate may be a little too fast and the iron loss may increase very slightly, but this is within a range that does not cause any problem in practice.

In this example, Fe-B-8i-based amorphous alloy was described, but it goes without saying that the method of the present invention is effective for other alloy-based amorphous materials that can be used as cores of electrical equipment. .

〔Effect of the invention〕

Amorphous alloys, which are effective as magnetic materials, still have insufficient magnetic properties as manufactured, so when amorphous alloys are used as cores for electrical equipment, they are usually subjected to further heat treatment after being formed into cores. Conventionally, this heat treatment was performed by placing the core in a heating furnace with an inert gas atmosphere while applying a DC magnetic field, maintaining it at a predetermined temperature, and then cooling it in the furnace. (On the other hand, in the present invention, the iron core was taken out of the furnace only during the cooling process in the above series of heat treatment processes and left to cool in the atmosphere. The cooling process can be completed in a short time, without the negative effects of oxidation, and by achieving a cooling rate that is effective in reducing iron loss, it has succeeded in significantly improving the magnetic properties of the iron core. .

[Brief explanation of drawings]

Claims (1)

[Claims] 1) When performing heat treatment in which an amorphous alloy iron core to which a DC magnetic field has been applied is heated to a predetermined temperature in a heating furnace in an inert gas atmosphere, held for a predetermined time, and then cooled, the iron core is taken out of the furnace and left in the atmosphere. A method for heat treatment of an amorphous alloy core, characterized by cooling the core.