JPH0583602B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] Regarding a method for producing an iron-cobalt sintered alloy, the purpose is to obtain a sintered body with high dimensional accuracy. Annealing is performed at a temperature low enough to cause α/γ phase transformation, and then rapidly cooled to room temperature, followed by cold working to form a sintered body.

[Industrial Field of Application] The present invention relates to a method for manufacturing an iron-cobalt sintered alloy with high dimensional accuracy.

Due to the need to process large amounts of information at high speed, the semiconductor devices that make up the main body of information processing equipment have become commercialized as LSI and VLSI due to the miniaturization of unit elements, which has led to the miniaturization of information processing equipment. This miniaturization is being carried out not only for semiconductor devices but also for all used parts.

The present invention relates to a soft magnetic material that is often used in the iron core of electromagnets.

[Conventional technology]

In the past, pure iron and silicon steel were generally used as soft magnetic materials, but in response to the demand for smaller and lighter equipment, permendar (iron, 50% Cobalt alloys) began to be used.

Conventionally, products have been manufactured using the melting method.

However, Permenda has Hv (Bitzker's hardness)
Since it is extremely hard with a diameter of 250 mm, it is difficult to process it using a lathe, etc., and therefore there is a problem of poor dimensional accuracy.

In order to solve this problem, the inventor has proposed a manufacturing method using a sintering method as shown in FIG. 2 (Japanese Patent Application No. 60-281885, filed on December 17, 1985).

In other words, zinc stearate, for example, is added as a lubricant (hereinafter referred to as a binder) to an alloy powder of iron (Fe) and cobalt (Co) in the required composition ratio, and the mixture is then "mixed" and then "compacted". The molded body is then heated at a temperature of about 400°C to decompose the binder (debinding), and then the temperature is raised to 600-700°C for pre-sintering.

This treatment is to perform a "recompression" treatment to increase the density of the compact, and due to the heat treatment at this temperature, sintering progresses, albeit slightly.

Here, if you perform "sintering" at approximately 1400℃ immediately after "debinding" without performing "preliminary sintering" and "recompression" processing, sintering will be intense and a sintered body with good dimensional accuracy will be obtained. I can't.

The pre-sintered body with improved dimensional accuracy through “recompression” is then “sintered” at approximately 1400℃ to obtain a sintered body of permenda, which is then “processed” such as drilling holes as necessary. By doing so, products with good dimensional accuracy can be obtained.

However, as the use of soft magnetic materials has expanded and thinner permenders have become necessary, it has become necessary to perform a "sizing" process because this method tends to cause deformation such as warping.

That is, by pressurizing at a pressure of several tons/cm ² and then performing a "pressurization" treatment, a product with high dimensional accuracy could be obtained.

However, the problem was that cracks were likely to occur during this "processing".

[Problem that the invention seeks to solve]

As mentioned above, permenda has come to be used as a constituent material for the electromagnetic parts that make up information processing equipment, but due to its high hardness, it is difficult to process using conventional melting methods to create high-precision products. It's difficult.

As a solution to this problem, the inventor proposed a sintering method, but it became necessary to correct the deformation by a sizing process for thin products.

However, the problem is that it tends to crack during processing.

[Means for solving problems]

The above problem can be solved by the conventional process shown in Figure 2.
After "sintering" the Fe/Co alloy, as shown in Figure 1, "sizing" is performed to correct the deformation of the sintered body, and then the temperature is lower than the sintering temperature and α/γ phase transformation occurs. This problem can be solved by a method for manufacturing Fe/Co sintered alloys, which involves annealing at a temperature of , followed by rapid cooling to room temperature, followed by various types of processing such as drilling and grooving.

[Effect]

The reason why cracks occur when a sintered body is subjected to processing such as drilling holes is because the permenda sintered body is thin, but it is also because the sintering process causes distortion inside the sintered body, and because it is hard. be.

Therefore, the present invention eliminates the occurrence of cracks by removing the internal strain and processing the material into an irregular lattice state with as low hardness as possible.

The reason for this will be explained below.

FIG. 3 shows a phase diagram of the Fe.Co alloy, and FIG. 4 shows the relationship between the composition ratio and the saturation magnetic flux density of the Fe.Co alloy.

As is clear from Figure 4, the saturation magnetic flux density (Bs) of Fe/Co-based magnetic materials is 35 to 50% by atomic weight of Co.
It is maximum in the range of , and tends to decrease when the amount of Co deviates from this range.

In addition, as shown in Figure 1, the melting point of the Fe/Co system is the lowest at 1470°C in the case of FeCo composition with an atomic weight % of 1:1, and as it deviates from this, the melting point of Fe (1534°C) and Co approaches the melting point of (1495℃).

For these reasons, a 1:1 FeCo composition, that is, an Fe/50% Co alloy is called Permenda.

Now, permenda deformed by sintering is sized by pressurizing it with a pressure of several tons/cm ² , but it is effective to remove the strain caused by this in the temperature range of the γ phase shown in the phase diagram in Figure 3. It is known that this is done.

In other words, in the case of FeCo composition, the phase transition from α phase (Ferrite structure) to γ phase (Austenite structure) is 980
Although it is carried out at a temperature of .degree. C., strain removal is preferably carried out in a temperature range in which the .gamma. phase is obtained.

Figure 5 shows the results of annealing at 1200°C in a hydrogen (H ₂ ) atmosphere, showing changes in magnetic permeability (μ), magnetic flux density (B ₅₀ ), and coercive force (Hc) with respect to the annealing time of permenda. It can be seen that the magnetic permeability is saturated in about 4 hours, the magnetic flux density is saturated in 1 to 2 hours, and the coercive force is saturated in 1 to 2 hours.

From these results, annealing is performed at a temperature of 1 at the temperature of the γ phase.
It turns out that it only takes about 5 hours.

Next, when the temperature is lowered from the γ-phase temperature range to enter the α-phase, a regular lattice or an irregular lattice is produced depending on the cooling rate.

In other words, according to experiments, when cooling from the γ phase to the α phase with a gentle temperature gradient of 50°C/min or less,
Fe and Co form a well-ordered lattice and exhibit high hardness, but when rapidly cooled at 50 to 500°C/min,
Since the atoms do not have enough room to form a regular lattice, they are in an irregular lattice state, resulting in a decrease in hardness.

Therefore, in the present invention, permenda is rapidly cooled to form an irregular lattice, and holes are drilled in this state to eliminate the occurrence of cracks.

〔Example〕

As raw material powders, 80Fe/20Co alloy powder of 325 mesh or less, Co powder of 400 mesh or less, and Fe/50Co were weighed, and 0.75% by weight of zinc stearate was added and "mixed".

This mixed powder was ``powder compacted'' at a pressure of 392 MPa (4 tons/cm ^{2 )} to make a magnetic circuit (head) for a 24-pin wire dot printer.

This was heated at 400° C. for 1 hour to remove the binder from the molded body to perform “debinding,” and then “preliminary sintering” was performed at 850° C. for 1 hour in an H ₂ stream.

Next, this was "recompressed" at a pressure of 588 MPa (6 tons/cm ² ), then "sintered" at 1400°C for 1 hour in a H ₂ stream, and then placed in a sizing mold. After pressurizing at 392MPa and "sizing" to correct warping and other deformations, _the
"Annealing" was performed at ℃ for 1 hour.

Next, this sintered body was subjected to "processing" such as cutting grooves, drilling 3 mm diameter holes, and cutting M3 threads, but no defects such as cracks or chips occurred.

〔Effect of the invention〕

By implementing the present invention, magnetic circuits with high dimensional accuracy such as heads for wire dot printers, which require processing such as drilling, can be made with permender at a high yield, and the yield is higher than that of products that do not undergo annealing. It has become possible to improve this by about 3 times.

[Brief explanation of the drawing]

Fig. 1 is a manufacturing process diagram according to the present invention, Fig. 2 is a conventional manufacturing process diagram, and Fig. 3 is a phase diagram of Fe/Co alloy.
Figure 4 shows the relationship between the composition ratio and saturation magnetic flux density of the Fe/Co alloy, and Figures A, B, and C show the annealing time dependence of the Fe/Co sintered alloy.

Claims (1)

[Claims] 1. After adding iron-cobalt alloy powder or the alloy powder with either iron powder or cobalt powder and mixing to a required composition ratio, a lubricant is added to the powder and compacting is performed. In the manufacturing process, the molded body is subjected to delubrication treatment and temporary sintering, then recompressed to increase density, and then sintered to create a sintered body, which is further processed to become a product. , After performing sizing treatment after sintering, annealing is performed at a temperature lower than the sintering temperature and at a temperature higher than that at which α/γ phase transformation occurs, then quenching is carried out to room temperature, and then cold working is performed. Characteristic manufacturing method of iron-cobalt sintered alloy. 2 The above annealing time is 1 to 5 hours, and
The method for producing an iron-cobalt sintered alloy according to claim 1, characterized in that the cooling rate for rapid cooling after annealing is 50 to 500°C/min.