JPS6323241B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to high-purity iron powder of large particle size to which phosphorus-containing powder is added, and is particularly for producing parts that satisfy strong demands for soft magnetism by powder metallurgy. Powder metallurgy manufacturing techniques are characterized by multi-step production of parts with excellent dimensional accuracy; powder,
It begins by mixing the lubricant, along with powdered alloying elements if necessary. The powder mixture is compressed into a rough compact whose shape approximately or exactly corresponds to the shape of the final compact. The rough compact is then heated and maintained at a temperature at which final properties such as strength and malleability are obtained through sintering. In effect, the material produced by this method will have a different porosity than the material produced by fusion metallurgy. Parts that meet the requirements for superior soft magnetic materials are:
Usually manufactured from materials that have iron as their main component, the most common manufacturing method is that the parts are made of high-purity solid materials,
For example, it is made from Armco iron. However, due to material economy, dimensional accuracy, and ease of molding, powder metallurgy techniques can also be used to manufacture these parts. However, until now, it has not been possible to obtain the same excellent soft magnetic properties as solid materials of the same composition from materials made using powder metallurgy that contain iron as a main component. This difference is essentially due to the porosity of the material produced by powder metallurgy. According to the method of the invention, which is more precisely characterized in the claims, materials produced by powder metallurgy methods have a particle size distribution that is abnormally shifted towards coarse particles. It has been demonstrated that by using iron powder having the same properties as a starting material, it is possible to obtain soft magnetic properties almost the same as those of high-purity solid iron. In addition to the coarseness of the iron powder, it is also required that the content of impurities be extremely low. The high-purity iron powder to be produced preferably by the spraying method needs to have an iron content of 99.8% or more. Here, % means weight %, and the same applies hereinafter. The content of impurities known to degrade the magnetism of iron must be as low as possible in this iron powder, preferably C<0.01%,
It is desirable that total -O<0.1% and N<0.005%. To obtain the advantages of the present invention, the particle size of the main part of the particles must be between 35 and 100 Tyler mesh (417-147 μm).
Use powder. 35Tyler mesh (417μm)
the content of larger particles is not more than 5%;
The content of particles smaller than 100 Tyler mesh (147 μm) is 20%, preferably less than 10%. If 5% or more of the iron powder has a particle size of 35 mesh or more, the mechanical strength of the product will be significantly reduced, and if 20% or more of the iron powder has a particle size of 100 mesh or less, the magnetic properties will significantly deteriorate. The mechanical strength of products made from these high-purity coarse iron powders is extremely low due to the low content of particles below 100 mesh; therefore, when high strength is required, there is no solution other than increasing the content of particles below 100 mesh. The result was that the soft magnetic properties were impaired. A solution to this problem is to add powdered alloying components to this high purity iron powder. This is because this alloying component increases the strength of the material obtained during firing without impairing its soft magnetic properties. As is also known, for example, from the Swedish patent no. It is already known to do this. As is known from the examples below, by mixing powdered iron phosphorus with these high-purity coarse iron powders, the strength of the fired material is not only maintained but also strengthened. can be multiplied by 5 times. According to the invention, the total phosphorus content of the mixture should not exceed 1.5%, and the maximum strength increase is obtained with a phosphorus content of 0.3%.
Further, it is preferable that the phosphorus content is added as iron phosphorus. Compacted under conditions related to normal powder metallurgy production,
After sintering, this powder mixture produces parts with better mechanical properties and soft magnetic properties than comparable phosphorus-free materials. Depending on the phosphorus content, it provides soft magnetism superior to that of high-purity solid iron. Specific examples of the present invention and their surprising results are shown below. Example 1 Two types of steel powders were tested with different types of particle distributions created by spraying, drying, and sieving after reduction. As a result of chemical analysis, these two types of iron powder showed the following composition.
It was 0.047% O, 0.0004% N, 0.0003% S, <0.1% C and the balance Fe. The particle distributions of these iron powders A and B were as follows. Iron powder Sieved type Tyler mesh% ＞35 35−100 ＜100 A 1.3 97.4 1.3 B 0.0 3.6 96.4 These iron powders have a phosphorus content of 15% and
mixed with iron phosphorus with particle size smaller than 45μm,
The phosphorus content was determined to be 0.45%. In the following description,
Powder A with 0.45% phosphorous addition is designated as C;
Powder B with 0.45% phosphorus content is designated as D. Powders A-D were mixed with 0.8% zinc stearate and compressed at a pressure of 589NPa to form bars with dimensions of 55 x 10 x 10, and after phosphorizing the lubricant for 30 minutes at 400 °C in air, they were prepared for testing. Built into a bar. The bars were further sintered in a belt furnace at 1120 °C for 60 min in a hydrogen atmosphere. Since coercive force is a function of the soft magnetic properties of the material, it was measured using a so-called coercive meter. The four materials listed above showed the coercive meter shown below. Material A 1.02 Oe B 1.56 Oe C 0.89 Oe D 1.34 Oe The above results demonstrate the significant advantages obtained when coarse iron powder is mixed with phosphorus. The low coercive force of material C was almost the same as that of Armco iron, which was 0.9 Oe. At the same time, it was found that as the coercive force decreases, the resistance of the material decreases with the addition of phosphorous, which means a decrease in eddy current losses, and as a result the overall magnetic losses decrease. The density, tensile strength and elongation at break are evident from the table below.

TABLE The strength properties shown in this example represent very significantly lower figures for material A, which is produced from a low content of iron powder with a particle size of less than 147 μm. From this result, it was also known that the addition of phosphorus to this powder increases the tensile strength approximately five times. Example 2 Iron powder A shown in Example 1 was mixed with iron phosphorus having a phosphorus content of 15% and a particle size of less than 45 μm, and the phosphorus content was 0.3 to 0.3 μm.
It was set at 1.5%. 0.8% zinc stearate was added to these mixtures. The test bar is Example 1
It was compressed and sintered in the same manner as in . The results were as follows.

Table 1 These results show that the tensile strength of the sintered bars with iron powder A as the base material is substantially increased by the addition of phosphorus. The fact that a substantial increase in tensile strength due to the addition of these phosphorus contents is obtained together with an improvement in soft magnetic properties is known from Figures 1 and 2, which show that the tensile strength and coercive force increase with increasing phosphorus content. This indicates that it is a function. Material Coercive force Oe A+0.30%P 0.95 A+0.45%P 0.89 A+0.60%P 0.82 A+1.00%P 0.73 A+1.50%P 0.85 A+0%Pacc. to example 1.02 These coercive forces are extremely low; These materials have been shown to be suitable for parts requiring excellent soft magnetic properties.

[Brief explanation of drawings]

Figure 1 shows the relationship between the particle content of 100 mesh or less and the coercive force of the parts obtained by the present invention, and Figure 2 shows the relationship between the particle content of 100 mesh or less and the tensile strength of the obtained sintered parts. Shown, 3rd
The figure shows the relationship between the particle content of 100 mesh or less and the degree of burst elongation of the obtained sintered parts of the present invention.
Figure 4 shows the relationship between the tensile strength of sintered parts when the phosphorus content is varied from 0.2 to 1.6% by weight, and Figure 5 shows the relationship between sintered parts when the phosphorus content is varied from 0.2 to 1.6% by weight. This shows the relationship between the coercive force of the connected parts.

Claims (1)

[Scope of Claims] 1. The main part of the powder made of high-purity iron powder of 99.8% or more has a particle size of 35 to 100 Tyler mesh (417 to 147 μm), and the powder has a particle size of more than 35 Tyler mesh (417 μm). Less than 5%, 20% powder with particle size smaller than 100Tyler mesh (147μm)
Powder for powder metallurgy for producing soft magnetic parts, characterized in that the powder contains 0.15 to 1.0% phosphorus as an alloying additive, preferably less than 10%. 2. The phosphorus content is added in the form of powdered iron phosphorus, preferably having a phosphorus content of about 15% and a particle size of less than 45 μm. Powder as described.