KR100768700B1 - Fabrication method of alloy parts by metal injection molding and the alloy parts - Google Patents

Abstract

A manufacturing method by metal injection molding and alloy parts manufactured by the same is provided to cut down manufacturing cost of high value-added precision parts having low sintering temperature and superior hardness and commercial production property. An alloy part manufacturing method comprising the following steps of: mixing a binder with an alloy powder having a composition comprising 40 to 75 wt.% of at least one component selected from the group consisting of Fe and a combination of Fe and Co, 20 wt.% or more of at least one component selected from the group consisting of W, Mo, Cr, Nb, V and Ni, 2 to 14 wt.% of at least one component selected from the group consisting of B, C, Cu, and Si, and the other inevitable impurities; injection molding the mixture to mold the mixture in the form of a part; separating the binder from the injection molded article; and sintering the binder-removed injection molded article, the alloy part is characterized in that the alloy powder has a composition comprising 20 to 35 wt.% of Cr, 1 to 2.5 wt.% of Si, 0.5 wt.% or less of C, 0.1 to 3 wt.% of Cu, 2 to 5 wt.% of B, 0.1 to 8 wt.% of Mo, 14 to 22 wt.% of Ni, and 4 to 15 wt.% of Co.

Description

Manufacturing method and alloy part of alloy part using metal injection molding method {FABRICATION METHOD OF ALLOY PARTS BY METAL INJECTION MOLDING AND THE ALLOY PARTS}

1 is a schematic view showing a manufacturing process according to the present invention.

2 is a photograph observing the densification degree of the metal parts manufactured according to an embodiment of the present invention with a scanning electron microscope.

3 is a photograph observing the densification degree of the metal parts manufactured according to another embodiment of the present invention with a scanning electron microscope.

The present invention relates to a metal injection molding (Metal Injection Molding) and a component manufactured by this method, and more particularly to a method of manufacturing a part using a metal injection molding method (Fe-Cr-based alloy powder) And it relates to the parts, and the metal injection molding method and the parts that can provide a part having a small physical properties of the constraints and the productivity is improved and excellent properties at a low cost compared to the conventional manufacturing method.

As a method for manufacturing precision parts having complex shapes used in automobiles, computers, electronic parts, industrial parts, medical devices, wear-resistant parts, and the like, cutting, die casting, precision casting, and powder metallurgy may be mentioned. However, these methods are difficult to apply due to the high manufacturing cost, lack of mass production, limited use of alloys to obtain desired properties, or the inability to manufacture complex three-dimensional shapes. There is a situation.

In order to solve such problems of formability, processability and mass production, metal injection molding, that is, a process of mixing powder and a binder, a process of injection molding a mixture, a process of removing a binder from an injection molded product, degreasing BACKGROUND ART There is known a method of manufacturing a product in a net shape that requires little post-processing through a process of sintering and molding an injection molded product.

Meanwhile, the parts manufactured by the metal injection molding method are mainly used for high value-added precision parts such as mobile phone hinges, which require corrosion resistance, high strength, high hardness, high quality mechanical and chemical properties, and require high durability. Or, it was prepared using a stainless steel powder.

By the way, in the case of iron, nickel or stainless steel powder, the sintering temperature of the final molding process is very high, about 1350 ℃, there was a problem that the power cost required for the sintering process and the equipment cost to enter the sintering equipment is very high. In addition, in the case of a conventional powder material, there is a problem that it is difficult to obtain sufficient physical properties to be applied depending on the application.

Accordingly, the so-called "micro-PIM method" has been attempted to reduce the sintering temperature and to make the powder very small in order to increase the molding accuracy. However, in this case, the sintering temperature is lower than the conventional one by reducing the powder size. Although it may be lowered by about 100 ℃, since the powder price is significantly increased compared to the conventional, there is a problem that it is difficult to expect a reduction in the manufacturing cost.

In powder injection molding, various materials such as metal, ceramic, cemented carbide, etc. are used, and the proportion of iron-based steel such as stainless steel accounts for more than 40% of all materials. Among them, STS316L has the most application, but as powder injection molding parts are gradually converted from shape-oriented parts to structural parts requiring mechanical properties such as aircraft, automobiles, medical devices, etc., STS630 (17-4PH) of high strength is increasingly used. have. STS630 is a martensitic precipitation hardening alloy and is one of the most corrosion resistant materials among high strength alloys. However, in the case of stainless steel, the production cost is very high because the sintering temperature is high.

The present invention has been made to solve the above problems of the prior art, it is a problem to provide a manufacturing method suitable for high value-added precision parts having a low sintering temperature, excellent hardness and excellent mass production at low cost.

In order to achieve the above object of the present invention, the present invention, the sum of one or more components selected from the group consisting of Fe, Fe and Co is 40 to 75% by weight, W, Mo, Cr, Nb, V, and The sum of one or more components selected from the group of Ni is 20% by weight or more, and the sum of one or more components selected from the group consisting of B, C, Cu, and Si is 2-14% by weight, and the composition includes other unavoidable impurities. Mixing the alloy powder and the binder; Injection molding the mixture into a shape of a part; Removing the binder from the injection molding; And it provides a method for producing an alloy component comprising the step of sintering the injection molding from which the binder is removed and the alloy component produced by the manufacturing method.

Further, for low hardness alloy parts, Cr: 20 to 35% by weight, Si: 1 to 2.5% by weight, C: 0.5% by weight or less, Cu: 0.1 to 3% by weight, and B: in the composition of the alloy powder. It is preferable that they are 2 to 5 weight%, Mo: 0.1 to 8 weight%, Ni: 14 to 22 weight%, and Co: 4 to 15 weight%.

In addition, for high hardness alloy parts, in the composition of the alloy powder, it is preferable that Cr: 40 to 50% by weight, Si: 1 to 2.5% by weight, C: 0.5% by weight or less, and B: 5.6 to 6.2% by weight. Do.

In addition, the step of sintering may be carried out in a vacuum, reducing gas or inert gas atmosphere at a temperature of 1100 ℃ ~ below the melting point of the alloy, or may be carried out at 1150 ℃ or more, or more than 1200 ℃, manufacturing costs and required Can be set differently depending on the physical properties. The sintering atmosphere may be any atmosphere that can remove oxides or the like present on the surface of the alloy powder during sintering, but is preferably performed under a high purity hydrogen atmosphere.

On the other hand, the sintering temperature is to perform the sintering in the range of about 1250 ℃ which is the melting point of the alloy powder at 1100 ℃. Accordingly, the sintering temperature may be set to about 100 to 250 ° C. lower than that of the sintering temperature of stainless steel powder, which is 1350 ° C., thereby significantly reducing energy costs such as power costs required for the sintering process.

In addition, the average particle diameter of the alloy powder is to be used 0.01 to 100㎛. If the average particle size is less than 0.01 μm, the cost of manufacturing the powder is significantly increased, which increases the unit cost of the product. If the average particle size is more than 100 μm, it is difficult to obtain sufficient precision and physical properties. Therefore, powder within the particle size range is used.

In addition, the step of removing the binder is performed by heating to a temperature range of 300 ~ 700 ℃ under a reducing gas atmosphere and maintained for 0.5 to 5 hours.

In addition, in the parts produced by the above production method, the porosity is preferably 7% or less by volume fraction, more preferably 5% or less. This is because when the porosity exceeds 7%, it is difficult to apply to parts due to poor physical properties such as hardness.

Hereinafter, the present invention will be described in more detail based on the embodiments of the present invention. However, the following examples are merely illustrative and should not be construed as limiting the invention.

EXAMPLE

The chemical composition of the alloy powder used in this example is as follows.

Chemical Composition of Alloy Powders element Cr Si C Cu S B Ni Mo Co Fe C 30-32 1.0-1.8 - 2.2-2.8 - 3.5-4.5 17-19 3.5-4.5 8.8-11 Bal. M 43-46 1.7-2.2 0.17 - 0.2 5.6-6.2 - - - Bal.

As shown in Table 1, in the metal injection molding method according to the present invention, an alloy composition represented by "C", in which Cr, Ni, Co, and the like is included in Fe, and Cr, B in Fe The powder of the alloy composition represented by "M" containing was used. By containing 20 to 50% by weight or more of Cr in Fe as described above, the sintering temperature can be drastically lowered. As can be seen from the following test results, mechanical properties are equally or significantly superior to those of conventional stainless steel powder injection molded products. It becomes possible to manufacture.

Figure 1 shows the manufacturing process of the metal injection molding method according to an embodiment of the present invention. As shown, metal injection molding is a net shape component through a process of mixing a powder and a binder, an injection molding process of a mixture, a degreasing process of removing the binder from the injected molding by pyrolysis, and a process of sintering the degreased molding. To prepare.

In the mixing process, the shape of the alloy powder is preferably closer to the spherical shape, the average particle diameter of the powder is preferably 100㎛ or less for high sintered density and numerical accuracy, in the embodiment of the present invention using particles of 40㎛ or less It was.

In addition, one of the most important operations in the mixing process is the selection of a suitable binder, which should be easy to mix and injection molding, and to obtain a material of desired physical properties when the binder used after injection molding is removed. Binders are used in combination of about 2 to 5 types of binders (lubricants), lubricants, plasticizers, and surfactants. If the moldability during injection molding is ensured, the total binder amount is preferably small in terms of preventing deformation during degreasing. For example, a volume ratio of 50-30% is appropriate.

In the embodiment of the present invention, the binder used was a mixture of 20 wt% ethylene vinyl acetate and 80 wt% paraffin wax. In the mixing process of the alloy powder and the binder, the alloy powder was mixed with the binder at a predetermined ratio and then mixed in a sigma blade type mixer in a temperature range of 130 to 160 ° C. for 2 hours.

The injection process of the mixture was carried out by charging the powder mixture into a 27 ton metal injection molding machine, and then injecting the powder mixture into a metal mold having a predetermined shape at a pressure of 450 bar and a temperature of 120 ° C.

In the degreasing process for removing the binder from the injection molding, the molding is charged into a tube furnace, heated to 300 ° C. at a rate of 2 ° C./min in a high-purity hydrogen atmosphere, and maintained for 1 hour, and held at 3 ° C. / After the temperature was raised to 500 ° C. at a rate of min and maintained for 1 hour, the temperature was increased to 700 ° C. at a rate of 3 ° C./min and maintained for 1 hour. Through such a process, complete binder removal was possible.

After measuring the liquid phase transition temperature through differential thermal analysis (DTA) for each alloy powder having the composition shown in Table 1, the sintering process is a temperature range of 1150 ℃ ~ less than the liquid phase transition temperature range in Table 2 Sintering was performed under the same conditions.

Sintering Condition Exam conditions Specimen Type Sintering temperature and holding time One C1 1100 ℃ / 30mim 2 C2, M2 1150 ℃ / 30mim 3 C3, M3 1200 ℃ / 30mim 4 M4 1250 ℃ / 30mim

Specimen types C1, C2 and C3 shown in Table 2 differ only in sintering temperature in the same composition, and M1, M2 and M3 are also the same. Sintering was used to maintain the temperature in a high purity hydrogen atmosphere for 30 minutes after heating up at a rate of 5 ° C / min to the target temperature of 1100 ° C, 1150 ° C, 1200 ° C, 1250 ° C shown in Table 2 above . By sintering in a reducing gas atmosphere in this manner, the oxide layer formed on the surface of the alloy powder is removed, and the interparticle bonding progresses by diffusion.

2 and 3 are photographs of the microstructure of the metal parts manufactured according to the sintering temperature through a scanning electron microscope (SEM). As shown, as the sintering temperature increases, the volume fraction of the pores formed in the grain boundary also decreases and the size tends to decrease. In addition, as a result of measuring the porosity and relative density, that is, the density of the parts were as shown in Table 3.

Evaluation of porosity and relative density of parts Specimen Type Porosity (%) Relative Density (%) C1 4.3 95.68 C2 3.5 96.47 C3 0.01 99.99 M2 0.61 99.39 M3 0.21 99.79 M4 0.05 99.95

As shown in Table 3, in the case of C1 sintered at 1100 ° C., the density was relatively high as 95.68%, and as the sintering temperature was increased, the density was higher than 99%.

As a result of measuring the hardness of the component according to the embodiment, the results shown in Table 4 were obtained.

Hardness evaluation result of parts Specimen Type Hardness (VHN) Remarks C1 94 Example C2 115 Example C3 319 Example M2 353 Example M3 747 Example M4 1059 Example STS316L 97 Comparative example STS630 275 Comparative example STS440C 543 Comparative example

As shown in Table 4, in the case of C1 according to the embodiment of the present invention, the sintering at a very low sintering temperature compared to STS316L, the hardness is almost similar, C2 is somewhat superior and C3 and M2 is 3 compared to STS316L It can be seen that it is about twice as high and exhibits hardness equal to or higher than that of STS630.
That is, since parts having high physical properties can be manufactured at low cost compared to stainless steel powder injection molded articles, the embodiments of the present invention can replace the conventional STS316L and STS630.

In addition, M3 and M4 of the present invention, while the sintering temperature is lower than that of the stainless steel powder, the Vickers hardness of 747 and 1059 can be seen to be superior to the stainless steel powder injection molded article.

As described above, the metal parts manufactured by the metal injection molding method according to the present invention are less constrained in size due to the characteristics of the manufacturing method and are capable of continuous production, and in particular, equivalent to those of metal injection molded products using conventional stainless alloy powder While showing the above hardness, the sintering temperature can be significantly lowered. That is, since high-quality, high value-added parts can be manufactured at a competitive price, they can be usefully used in all industries such as automobiles, computers, electronic parts, industrial parts, medical devices, and wear-resistant parts.

In addition, according to the metal injection molding method according to the present invention, it is possible to manufacture a net shape product having excellent density by minimizing pores.

Claims (11)

delete delete delete delete delete delete delete delete 40 to 75% by weight of one or more components selected from the group consisting of a combination of Fe, Fe and Co, and 20% by weight of one or more components selected from the group of W, Mo, Cr, Nb, V, and Ni Mixing the binder and the alloy powder having a composition of 2 to 14% by weight and comprising other unavoidable impurities, wherein the sum of at least one component selected from the group consisting of B, C, Cu, and Si; Injection molding the mixture into a shape of a part; Removing the binder from the injection molding; And an alloy part manufactured by sintering the injection molding from which the binder is removed. In the composition of the alloy powder, Cr: 20 to 35% by weight, Si: 1 to 2.5% by weight, C: 0.5% by weight or less, Cu: 0.1 to 3% by weight, B: 2 to 5% by weight, Mo: 0.1 Alloy parts, characterized in that ~ 8% by weight, Ni: 14-22% by weight, and Co: 4-15% by weight. 40 to 75% by weight of one or more components selected from the group consisting of a combination of Fe, Fe and Co, and 20% by weight of one or more components selected from the group of W, Mo, Cr, Nb, V, and Ni Mixing the binder and the alloy powder having a composition of 2 to 14% by weight and comprising other unavoidable impurities, wherein the sum of at least one component selected from the group consisting of B, C, Cu, and Si; Injection molding the mixture into a shape of a part; Removing the binder from the injection molding; And an alloy part manufactured by sintering the injection molding from which the binder is removed. In the composition of the alloy powder, Cr: 40-50% by weight, Si: 1-2.5% by weight, C: 0.5% by weight or less, and B: 5.6-6.2% by weight. The alloy part according to claim 9 or 10, wherein the porosity of the alloy part is 7% or less by volume fraction.

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