JPH03104802A - Method for manufacturing sintered product - Google Patents

Abstract

PURPOSE:To manufacture a sintered product improved in shaped-maintainability by magnetizing powder material at the time of removing binder in an injected green compact composed of the powdery material containing ferromagnetism material and organic binder. CONSTITUTION:The injected green compact 1 is formed with the powdery material containing at least one kind of alloy powder among iron, nickel, cobalt or these ferromagnetism material and at least one kind of ferromagnetism oxide powder having Fe2O3 as essential component and amorphous of magnetic material, and the organic binder. At the time of removing the binder in this green compact 1, the green compact 1 is laid on an alnico magnet plate 2 (about 1200-13500 gauss residual magnetic density, about 600-700 oersted coercive force, about 8mm thickness) and raised to about 500 deg.C under N2 atmosphere at about 10 deg.C/hr temp. raising speed and held for about 2hr. By this method, the sintered product improved in the shape-maintainability is obtd. from the injection green compact.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a process for removing the binder from an injection molded product made of a powdered material and an organic binder, and is used to produce a sintered product that improves the shape retention of the injection molded product. Regarding the method. (Prior art) Conventionally, when sintering powdered materials, a binder is added to the powdered materials, the material is shaped into a predetermined shape, and then sintered, but attempts have been made to form the material by injection molding. and some of them have been put into practical use. In this case, the molded product is injection molded into a predetermined shape by mixing a powdered material and a binder containing an organic substance, mainly resin, and utilizing the fluidity of the organic substance. The binder is removed, but in order to prevent the molded product from deforming during the temperature rising process, it is buried in powder such as alumina, or a jig is used to hold the shape. Most of the binder flows out or is decomposed and removed during this binder removal process, and then the binder-free molded product is sintered at a high temperature. [Conventional Example 1] Average particle size: 4 pm. Carbon content 0. Ol%, M elementary amount 0.
424.3g (9% by weight) of a binder whose main component is polyamide was added to 4290g of 2% spherical iron powder, kneaded in a pressurized kneader at 140°C for 2 hours, pulverized, and put into an injection molding machine. Injection temperature: 150℃, injection pressure: 1ton/c
The molded product shaped with a shaping pressure of 1.5 m'' was attached to the SUS304L!! jig (1l) as shown in Fig. 6(a), ) using a jig (12) that holds the entire interior of the molded product, with alumina powder (13) placed at the bottom of the molded product, was heated to 500°C at a rate of 10°C/hr in a N2 atmosphere. The temperature was raised, held for 2 hours, and then cooled in a furnace.As shown in Figure 7 <a), the binder-removed product using jig (1)) hardly retained its shape; (12), as shown in Figure 7(b), retained its original shape to a great extent, but suffered from significant deformation and cracking, and the shape could not be maintained sufficiently with support from a jig. [Conventional example] 2] A test was conducted using SUS410L powder with an average particle size of 10 μm as the metal powder, using alumina powder for the jig (1L), and using other conditions as in Conventional Example 1.The powder shape used was carbonyl. Compared to iron powder, it has a slightly angular block shape, so there is less deformation during binder removal due to the powder shape itself, but deformation and cracking were still observed when using a jig. (This is what the invention seeks to solve) rsB) However, in consideration of the appearance of powder injection molded products, 35-55% of the volume of the molded product is usually occupied by binder.Before sintering the molded product, it is desorbed at a relatively low temperature. A binder treatment is performed to decompose and remove 80 to 98% of the initial amount of binder input.However, during the heating process, the molded product must go through a weak state where it is highly susceptible to deformation because the binder is thermoplastic. .In particular, in the temperature range from -2O℃ to +100℃ beyond the softening point of the binder, the binder is not fully decomposed and removed, making it particularly susceptible to deformation.The main cause of deformation is that the molded product cannot support its own weight. The ease of deformation is listed as follows.

(1) Properties of the pinda itself.

(2) Amount of binder added (the larger the amount, the easier it is to deform). (3) Shape of the powder material used (the more spherical it is, the easier it is to deform). (4) Shape of molded product.

(5) Packing appearance when removing the binder. It is significantly affected by etc. In the production of sintered products, a major challenge is how to quickly remove multiple binders without causing defects in the molded product, and various methods have been tried to improve shape retention during binder removal. ing. (a) Part or all is embedded in powder such as alumina. (b) Reduce the amount of binder added. (c) Making the metal powder not spherical but lumpy or flaky in which the particles are difficult to move among themselves.

(d) Use a metal or ceramic support jig to support the molded product. (e) Improve shape retention by improving the properties of the binder itself. However, regarding (a), it requires a lot of man-hours to embed the molded product in alumina powder and especially to remove the alumina powder after debinding, which increases the cost and also increases the cost of removing the binder as shown in Figure 9. The surface roughness of the sintered product deteriorates because the alumina powder remains on the surface, b) and c)
Since this inhibits the flowability of the compound itself (a mixture of powder material and binder), it has a significant negative effect on injection moldability. Regarding d), there are restrictions on the shape of the molded product, and the number of jigs equivalent to the number of debinding processes is required, so the cost is high. Regarding ee), a considerable effect can be seen. There are drawbacks such as the fact that there are significant restrictions on the shape of the molded product and the packaging, making it difficult to say it is sufficient.

(Means for Solving the Problem) The present invention has been made in order to solve the problems in the prior art, and the first invention is an injection molding material made of a powdery material containing a ferromagnetic material and an organic binder. A method for manufacturing a sintered product, characterized in that the shape of the injection molded product is maintained by magnetizing the powdered material containing the ferromagnetic material in the binder removal process of the molded product, the second invention The ferromagnetic material in the first invention is iron, nifkel, cobalt, or an alloy powder of at least one of these ferromagnetic materials. A third invention provides a method for producing a sintered product characterized by containing at least one of a ferrimagnetic oxide powder containing FetO as a main component or an amorphous magnetic material. In the invention, the injection molded product is made of a powdery material containing a ferromagnetic material.
65% by volume, with the remainder being an organic binder, and by applying a magnetic field to the injection molded product, the shape of the injection molded product is retained in the binder removal process by the blocking force between the magnetized powders. According to the method for producing a sintered product characterized by the above-mentioned third invention, a magnetic field is applied from above the injection molded product to pull the ferromagnetic material upward, so that the binder removal process is performed. A fifth invention provides a method for manufacturing a sintered product, characterized in that deformation due to its own weight is prevented. According to a sixth aspect of the present invention, an injection molded product is embedded in a powder made of a magnetic material, and the injection molded product is embedded in a powder made of a magnetic material, and the injection molded product is embedded in a powder made of a magnetic material, and the injection molded product is embedded in a powder made of a magnetic material, and the injection molded product is embedded in a powder made of a magnetic material. By magnetizing the powder made of the magnetic material before the step, the shape of the injection molded product is maintained in the binder removal step by the profking force between the magnetized powder pairs. The purpose was achieved by changing the method of manufacturing the product.

(Function) When using the above structure, pure iron, carbon steel, magnetic steel, silicon il
l, FeNi alloy. AI-Fe alloy. Si AI
Fe alloy. Iron. nickel. Among cobalt or at least one kind of alloy powder of these ferromagnetic materials, powder of ferrimagnetic oxide whose main component is Fe2O, or amorphous magnetic material,
If a magnetic field is applied to an injection molded product containing at least one type of ferromagnetic material during the binder removal process, or if a powdered material containing a ferromagnetic material is magnetized during the binder removal process, it will not be magnetized. The shape retention of the injection molded product during the de-pindering process can be improved by the profusing force between the powders. Furthermore, if a magnetic field is applied from above the injection molded product to pull the ferromagnetic material upward, deformation due to its own weight during the debinding process can be prevented and shape retention can be improved. In addition, if an injection molded product is embedded in powder made of a magnetic material and the powder made of magnetic material is magnetized, the injection molded product will retain its shape during the binder removal process due to the blocking force between the magnetized powder pairs. It is also possible to do so. (Examples) Examples of the invention will be described in detail below with reference to the attached drawings. (Example 1) The molded product (1) that was shaped under the same conditions as the conventional example was
As shown in Figure 1, the residual magnetic density is 12O00~1350.
0 Gauss, holding power 600-700 Elstenod 1 Thickness 8
It was placed on a 1.0 mm alnico magnet plate (2), heated to 500 °C at a rate of 10 °C/hr in a N2 atmosphere as in Conventional Example I, held for 2 hours, and then cooled in the furnace. As a result, as shown in Figure 2, there was no change due to its own weight. Note that alnico magnets do not lose their magnetic force even when heated to 500°C and can be reused. Needless to say, even if the magnetic force is lost, it can be used semi-permanently if remagnetized. An injection molded product containing at least one type of metal powder or alloy powder of ferromagnetic materials such as iron, nickel, and cobalt is composed of metal powder (5) and a binder (4) as shown in FIG. When this molded product is placed in a magnetic field, the independent metal powders (5) are easily magnetized, and the metal powders (5) that are close to each other are easily magnetized.
5) As a result of the force that attracts the two, a profking force acts to try to maintain the shape of the molded product as a whole.Therefore, when the binder is removed, the binder softens, which is the temperature at which the molded product becomes plastic. Temperatures from TM-20°C to TM+100°C (defined as TM°C), especially T
When a magnetic field is applied to a molded product in the temperature range of M-20℃ to TM+50℃, the powder that makes up the molded product becomes magnetized.
Because of the blocking force mentioned above, combined with the holding force of the binder itself, although weak, the shape before de-binding is maintained. The magnetic field can be applied by placing the molded product in direct contact with the permanent magnet, or by placing it a little apart, and the effect remains the same even if it is applied as an electromagnetic field. The temperature range for applying the magnetic field is from TM-20℃ to TM+10
If the magnetic field is applied reliably at 0°C, the effect will remain the same at other temperatures even if no magnetic field is applied.

(Example 2) A ferrite magnet of the same size as the alnico magnet was used below an injection molded product manufactured in the same manner as in Example 1. Ferrite magnets have a residual magnetic density of 3300 to 3700 Gauss. A plate material with a holding force of 2700 to 3200 Oersted was used.
De-binding was carried out under the same conditions as in Example 1, and a binder product with a completely sound shape was obtained, similar to the alnico magnet. However, in the case of ferrite magnets, heating up to 500°C will cause them to lose their magnetic force, so when reusing them, the temperature is generally considered to be 40°C, which causes changes in the ferrite material.
It may be used in the W1 range that does not exceed 0°C, or it may be subjected to resulfurization treatment.

(Example 3) Above the injection molded product shaped like Example 1, an alnico magnet plate (
3) was set. As a preliminary experiment, when a molded product was placed on a scale and an alnico magnet was brought closer from above, the apparent weight of the molded product became lighter as the magnet was brought closer. This is the apparent weight.

Although the binder was removed in the same manner as in Example 1, due to the effect of reducing the apparent weight due to the magnet and the pulling force generated due to the magnetization of the powder, the binder was removed in the same manner as in Example 1 and Example 2. 01 A binder-free product with a perfect shape was obtained.

(Example 4) A magnetic force was applied from below to an injection molded product manufactured in the same manner as in Conventional Example 2, and the binder was removed under the same conditions as in Conventional Example 2. As shown in Fig. 4, no deformation was observed. ．． (Example 5) After demagnetizing a commercially available cast alnico magnet, it was
13% by weight of binder whose main component is boryamide was added to alnico powder crushed to 0 μm or less, and the powder was mixed in a pressure kneader for 1
It was maintained at 40°C for 2 hours to perform injection molding. After that, the molded product was magnetized by applying a magnetic field of 3000 oersteds in a magnetizing device and heated to 500°C at 10°C/h in an N2 atmosphere.
The temperature was raised at a rate of r and then maintained for 2 hours, followed by cooling in the furnace. The molded product subjected to the binder removal treatment as described above retained its shape completely. For materials in which magnetism remains as described above, by magnetizing the molded article before the binder removal process, the same shape-retaining effect as applying a magnetic field during the binder removal process could be obtained.

(Example 6) The molded product in (Example 1) was placed on an electromagnetic magnet, and the electromagnetic magnet was energized for 25 minutes in the atmosphere.
The temperature was raised to 0°C at a rate of 10°C/hr, maintained for 2 hours, and then cooled in the furnace. The shape of the garment that had been de-pindered as described above was completely retained, and the same shape-retaining effect as with permanent magnets was obtained.

(Example 7) Using the kneaded material in (Example 1), two tensile test specimens each having a circular cross section were molded by injection molding.

With Alnico magnets 15 in contact with both ends of one of the tensile test pieces as shown in FIG. 10, and with no magnetic field applied to the other tensile test piece (as shown in Example When the binder was removed under the same conditions as in Figure 1), the tensile wiping specimen 14 without the magnetic field applied was deformed as shown in Figure 1), whereas the specimen with alnico magnets 15 in contact with both ends was deformed as shown in Figure 1). , a good shape-retaining effect as shown in FIG. 10 was obtained.

(Example 8) Using the kneaded material in (Example 1), the inner diameter φ7 and the outer diameter φ1
2. It was injected into a cylindrical shape with a length of 100 mm. As shown in FIG. 12, in order to apply a magnetic field uniformly inside the cylindrical molded body 16, a round 1417 made of ordinary steel (SS41) with a diameter of 6×1)0 is inserted, and the magnetic field is applied from below by an alnico magnet 18. I put it on. In this way, the blocking effect of the magnetic field can be spread to every corner of the cylindrical molded body 16. In this state, when the binder was removed, a good shape-retaining effect was obtained even in the binder removal process of a thin and long object as described above.

(Example 9) As shown in FIG. 13, the molded product l6 of (Example 8)
was placed in a SS41) box-shaped container 19, further filled with atomized iron powder 2O having an average particle size of 75 μm, and subjected to binder removal treatment on a ferrite magnet plate 21. In the conventional method of producing a molded body from alumina powder, etc.,
Although the alumina powder inevitably moves, the shaped body remains slightly deformed, but according to this example, an extremely strong banking force was exerted, so that a good shape-retaining effect was obtained.

(Example 10) Austenitic stainless steel SOS30, which is a non-magnetic material
10% by weight of Carboni N1 powder, which is a ferromagnetic material, was added to 4L powder (average particle size 9 μm), and after mixing (Example 1)
When the binder removal process was carried out in the same manner as above, a good shape-retaining effect was obtained due to the ferromagnetic material added that acts between the carbonyl Ni powders. As mentioned above, even if the main powder is non-magnetic, by blending a ferromagnetic material, magnetic force can be exerted to improve shape retention. However, the usual amount of ferromagnetic material added is 5 to 40% by weight; less than 5% by weight will have little shape-retaining effect, and if it exceeds 40% by weight, the properties will deviate greatly from the original material. Otherwise, it may become economically disadvantageous. (Effects of the Invention) Since the present invention is structured as described above, there is no need to embed the molded product in alumina powder, remove the alumina powder after debinding, and no need for a support jig. Furthermore, there are no restrictions on the shape of the metal particles, resulting in cost reduction. In addition, the surface roughness is improved, and there are no restrictions on the shape of the molded product, making it possible to expand the range of common parts.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional side view of a molded product according to an embodiment of the present invention before removing the binder with an alnico magnet plate placed below the molded product, Fig. 2 is a perspective view from diagonally above after removing the binder of Fig. 1, and Fig. 3 Figure 1 is a vertical cross-sectional side view of the alnico magnet plate shown above the molded product, and Figure 4 shows SUS401L metal powder with an average particle size of 10 μm.
Figure 5 is an explanatory diagram showing the relationship between metal powder and binder, Figure 6 is a perspective view from diagonally above after binder removal using
Figure (a) is a cross-sectional side view using a conventional jig, (b) is a cross-sectional side view before debinding using a conventional jig and alumina powder, and Figure 7 (
a) and (b) are perspective views from diagonally above after removing the binder in Fig. 6 (aHb), and Fig. 8 is a 10 μm metal powder as a metal powder.
Both (a) and (b) are perspective views from above after debinding using alumina powder, and Figure 9 shows the alumina powder depression remaining on the surface of the debinding product when alumina powder is used. Figure 10 shows the seventh embodiment of the present invention; Figure 1) shows a comparative example of the seventh embodiment of the cough; Figure 12 shows the eighth embodiment of the present invention. 13 are diagrams showing a ninth embodiment of the present invention. ■・・・
... Molded product 2 , 3 , 4 , 5 , 1) l 3 , 1 4 , 15.18 1 6 , l 7 , 1 9 , 2 0 , 21 12 Magnetic plate/binder...metal powder・Jig・Alumina powder・Tensile test type・Alnico magnet・Cylindrical body・9 Rod・Box type container・Atomized iron powder・Ferrite magnet plate

Claims (6)

[Claims] (1) In the binder removal process of an injection molded product made of a powdery material containing a ferromagnetic material and an organic binder, the shape of the injection molded product is maintained by magnetizing the powdery material containing the ferromagnetic material. A method for producing a sintered product characterized by: (2) The ferromagnetic material in claim (1) is iron, nickel, cobalt, or an alloy powder of at least one of these ferromagnetic materials, a ferrimagnetic oxide powder containing Fe_2O_3 as a main component, or A method for producing a sintered product, the method comprising at least one type of amorphous magnetic material. (3) The injection molded product according to claim (1) or (2) contains 40 to 65% of the powdered material containing the ferromagnetic material.
% by volume, with the remainder being an organic binder, and a magnetic field is applied to the injection molded product so that the shape of the injection molded product is retained in the binder removal process by the blocking force between the magnetized powders. A method for manufacturing a sintered product. (4) In claim (3), a magnetic field is applied from above the injection molded product to pull the ferromagnetic material upward to prevent deformation due to its own weight during the binder removal process. A method for manufacturing a sintered product. (5) In claim (1) or (2),
A method for manufacturing a sintered product, characterized in that a powdered material containing a ferromagnetic material is magnetized before a binder removal step. (6) Blocking between magnetized powder pairs by embedding the injection molded product in powder made of a magnetic material and magnetizing the powder made of the magnetic material during or before the binder removal process A method for manufacturing a sintered product, characterized in that the shape of the injection molded product is maintained in the binder removal step by force.