KR101350944B1 - Ferrous-alloys for powder injection molding - Google Patents

Abstract

An iron-based alloy for powder injection molding is disclosed. Iron-based alloy for powder injection molding according to the present invention is iron (Fe) 52.59 ~ 78.15wt.%, Chromium (Cr) 16.45 ~ 37.34wt.%, Boron (B) 3.42 ~ 7.72 wt.%, Silicon (Si) 1.64 ~ 1.92wt.%, Sulfur (S) 0 ~ 0.21wt.%, Carbon (C) is characterized by consisting of 0.16 ~ 0.18wt.% And other unavoidable impurities.

Description

Ferrous alloy for powder injection molding {FERROUS-ALLOYS FOR POWDER INJECTION MOLDING}

The present invention relates to an iron-based alloy, and more particularly to an iron-based alloy for powder injection molding.

Powder injection molding (PIM) is a new powder metallurgy technology that combines powder metallurgy technology and injection molding, a technology for mass production of precise plastic parts.

The powder injection molding (PIM) process is a process in which a fine powder and a polymer binder that is the main agent of the fluid are mixed and injection molded into the mold, and then the binder is removed from the injection molded product, and only the powder is hot sintered to manufacture a part. Consists of.

The continuous R & D and application of the powder injection molding process is expanding, and the existing component designers and field users recognize the advantage that the degree of freedom in designing parts by the combination of materials and shapes used in the powder injection molding technology is great. This is because research centers and companies related to injection molding technology are developing processes with diversified application materials and economic feasibility.

That is, it is possible to manufacture three-dimensional precision parts using all powder materials such as metals, ceramics, cemented carbide, and intermetallic compounds, and high value-added parts as it is possible to mass-produce them with almost no post-processing even in difficult or non-castable materials. Powder injection molding technology is suitable for economical production.

Stainless steel, which occupies most of the metal powder injection molding market, is changing its chemical composition to meet the properties such as strength, hardness, wear resistance, and corrosion resistance required by the final powder injection molded parts.

Therefore, the stainless steel powder used in the powder injection molding is various, such as SUS304L, SUS316L, SUS430, SUS630, and in the case of martensitic stainless steel powder injection molding, an additional heat treatment process is required.

Therefore, while fully satisfying the physical properties of conventional powder injection molding parts, there is a need for the development of alloys that can be applied to various powder injection molding parts with economical and various microstructures and properties without the need for heat treatment.

An object of the present invention is to provide an iron alloy of low cost production cost and excellent hardness, wear resistance, corrosion resistance compared to the stainless steel used in conventional powder injection molding.

Iron-based alloy for powder injection molding according to a preferred embodiment of the present invention for achieving the above object is iron (Fe) 52.59 ~ 78.15 wt.%, Chromium (Cr) 16.45 ~ 37.34 wt.%, Boron (B) 3.42 ~ 7.72 wt.%, silicon (Si) 1.64 ~ 1.92wt.%, sulfur (S) 0 ~ 0.21 wt.%, carbon (C) is characterized by consisting of 0.16 ~ 0.18 wt.% and other unavoidable impurities.

The ratio of chromium (Cr) and boron (B) (X _Cr / X _B ) is characterized in that 1.0.

The sum (X _Cr + X _B ) of the composition of chromium (Cr) and boron ( _B ) is 0.30 to 0.60.

The sum of the composition of the iron (Fe), chromium (Cr) and boron (B) (X _Fe + X _Cr + X _B ) is characterized in that 0.9635.

The microstructure of the iron-based alloy for powder injection molding is characterized in that chromium boride (Cr ₂ B) is distributed in the form of a network in a ferrite matrix.

The volume fraction of the chromium boride (Cr ₂ B) is characterized in that 51% ~ 91%.

The hardness of the powder injection molding iron-based alloy is characterized in that 600 ~ 1600 VHN.

The injection molding method of the iron-based powder according to another preferred embodiment of the present invention provides a powder of the iron-based alloy for powder injection molding, mixing the powder and the binder of the iron-based alloy for powder injection molding to form a powder mixture Compressing the powder mixture, removing the binder by heating the powder mixture, and sintering the powder mixture from which the binder has been removed.

The powder mixture is formed by mixing the powder of the iron-based alloy for powder injection molding with paraffin wax, tungsten carbide balls and heptanes in a container, and then rotating the container.

Iron-based alloys for powder injection molding according to the present invention can greatly improve the hardness and wear resistance compared to conventional stainless steel by forming a hard Cr ₂ B boride in different volume fractions.

In addition, the iron-based alloys for powder injection molding according to the present invention lower the fraction of the alloying elements, the alloy price is cheaper than commercial stainless steel, it is excellent in price competitiveness by reducing the production cost by reducing the sintering temperature and time.

Figure 1 is a scanning electron microscope (SEM) photograph showing the microstructure of the powder injection molding iron-based alloy according to an embodiment of the present invention.
2 is an Fe-Cr-B ternary isothermal state diagram of the iron-based alloy designed by the present invention.
Figure 3 is a graph showing the results of calculating the precipitation driving force change of Cr2B according to each component composition of the element (Fe, Cr, B, Si, S, C) of the base alloy when designing the iron-based alloy according to the present invention.
Figure 4 is a graph showing the fraction of the equilibrium phase present at 1,000 ℃ according to the ratio of chromium and boron in the iron-based alloy according to the present invention.
5 to 7 are graphs showing equilibrium phase fractions according to temperature of alloy compositions of nine iron-based alloys designed by the present invention.
8 to 10 are scanning electron micrographs of the microstructure after casting and heat treatment of the iron-based alloys according to the present invention.
11 are X-ray diffraction results of the iron-based alloys according to the present invention.
12 is a graph showing the price of the alloying element according to the physical properties (hardness basis) required for the part.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims. Like reference numerals refer to like elements throughout the specification.

Hereinafter, an iron-based alloy for powder injection molding according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid unnecessarily obscuring the subject matter of the present invention.

Iron-based alloy for powder injection molding according to an embodiment of the present invention

Iron (Fe) 52.59 to 78.15 wt.%, Chromium (Cr) 16.45 to 37.34 wt.%, Boron (B) 3.42 to 7.72 wt.%, Silicon (Si) 1.64 to 1.92 wt.%, Sulfur (S) 0.21 wt .%, Carbon (C) 0.16 ~ 0.18 wt.% And other unavoidable impurities.

The microstructure of the iron-based alloy is characterized in that the chromium boride (Cr ₂ B) is distributed in the form of a network in the ferrite (ferrite) base.

Since the chromium boride (Cr ₂ B) phase according to the present invention is very hard, the shape and fraction distribution state of the precipitated chromium boride phase can directly affect the overall hardness and wear resistance of the specimen.

The chromium boride phase of the iron-based alloy has a network structure, the entire hardness distribution of the specimen is uniform according to the position, and the load applied even in abrasion environment is excellent in wear resistance properties.

In addition, the volume fraction of the chromium boride (Cr ₂ B) is characterized in that 51% ~ 91%.

The hardness of the alloy is characterized in that 600 ~ 1600 VHN.

In order to satisfy the high hardness and low cost conditions of the iron-based alloy required in the powder injection molding process, high hardness properties can be obtained by using chromium boride precipitation, which is a relatively inexpensive compound of Cr and B.

The composition ratio of chromium (Cr) and boron (B) may be fixed at 1: 1, and the sum of the composition ratios of chromium (Cr) and boron (B) (sum of molar ratios) may be adjusted from 0.30 to 0.60. In this case, the sum (combination of mole fractions) of the composition ratios of iron (Fe), chromium (Cr), and boron (B) as the main components may be fixed at 0.9634.

The chromium (Cr) is generally an alloy element added to increase the hardenability of the alloy during quenching and to improve corrosion resistance. In the present invention, the chromium (Cr) is an element that binds to boron (B) to control the chromium boride precipitation fraction.

The precipitation fraction of chromium boride must be 50 vol. It is formed in more than% to obtain a hardness of about 600VHN or more of the high hardness requirements required in the powder injection molding process.

If the content of chromium exceeds 37.34 wt.%, Excessive chromium boride precipitates and the toughness is inhibited, so the content is limited to 16.45 to 37.34 wt.%.

And depending on the chromium (Cr) content, the content of B is determined to be 3.42 ~ 7.72 wt.% Boron (B).

Boron is an element added to improve the hardenability, in the present invention is an element that is combined with chromium to control the chromium boride precipitation fraction. The boron content should not be less than 3.42 wt.% So that the precipitation fraction of chromium boride is 50 vol. It is formed in more than% to obtain a hardness of about 600VHN or more of the high hardness requirements required in the powder injection molding process.

If the content of boron exceeds 7.76 wt.%, Excessive chromium boride precipitates and inhibits toughness, so the content is limited to 3.42 to 7.76 wt.%. And depending on the content of such boron, the content of chromium is determined to be 16.45 ~ 37.34 wt.%.

In the present invention, silicon (Si) is an element that serves to stabilize the base with ferrite in the sintering process during the powder injection molding process and to increase the hardenability through solid solution strengthening. If the content of silicon is less than 1.64 wt.%, The solid solution strengthening and ferrite stabilization effect is insignificant. If it is added more than 1.92 wt.%, The solid solution strengthening effect does not increase proportionally and the content is increased to 1.64 ~ 1.92wt.%. Restrict.

Sulfur is generally controlled to be as low as possible to form a non-metallic inclusion to lower the properties of the alloy, but in the present invention was added to the extent that the sulfide (FeS) is not formed to achieve the matrix and chromium boride stabilizing effect. Therefore, it is preferable to set the upper limit to 0.21 wt.%.

Carbon is an element that can effectively improve the hardenability of the alloy, and the content of carbon should be 0.16 wt.% Or more in order to satisfy the intended hardness of the present invention. Is limited to 0.16 to 0.18 wt.%.

Injection molding method of the iron-based powder according to another preferred embodiment of the present invention provides a powder of the iron-based alloy for powder injection molding, mixing the powder and the binder of the iron-based alloy for powder injection molding to form a powder mixture, Compression molding the powder mixture, heating the powder mixture to remove the binder, and sintering the powder mixture from which the binder has been removed.

The powder mixture may be formed by mixing the powder of the iron-based alloy for powder injection molding with paraffin wax, tungsten carbide balls and heptanes in a container, and then rotating the container.

Compression molding of the powder mixture may be performed by using a press at a pressure of 100 kgf / cm ² or more after charging the powder mixture into a mold.

The binder may be removed by raising the compression-molded powder mixture to 500 ° C. at an elevated temperature rate of 2 ° C./min or more and then maintaining the mixture for 1 hour.

The sintering may be performed by charging the powder mixture in which the binder is removed to a heat treatment furnace and heating it to 1,175 ° C. at a temperature increase rate of 3 ° C./min or more in a hydrogen atmosphere, and then maintaining the mixture for 1 hour.

The present invention is based on the Fe-43Cr-5.6B-1.8Si-0.2S-0.17C (wt.%) Alloy, by reducing the ratio of alloying elements and by changing the ratio of chromium (Cr) and boron (B) Different volume fractions of chromium boride (Cr ₂ B) are formed on the ferrite matrix to provide a high hardness, low cost iron alloy for powder injection molding that can exhibit a variety of physical properties.

In addition, the microstructure of the alloys according to the present invention may have a structure in which other crystalline particles are dispersed in addition to the chromium boride (Cr ₂ B) and the ferrite matrix.

Hereinafter, the present invention will be described in more detail with reference to preferred examples and comparative examples. However, the following examples are merely examples to help the understanding of the present invention, whereby the scope of the present invention should not be reduced or limited.

≪ Example 1 >

Table 1 below is a table showing the composition of the base alloy as a reference when designing the iron-based alloy for powder injection molding according to the present invention.

Fe Cr B Si S C atom% Bal. (38.15) 35.79 22.40 2.77 0.27 0.61 weight% Bal. (49.23) 43 5.6 1.8 0.2 0.17

Table 2 below is a table showing the composition of the alloy designed by the thermodynamic calculation of the iron-based alloy for powder injection molding according to the present invention.

alloy ratio Fe Cr B Si S C Example 1 atom% 66.34 15.00 15.00 2.77 0.27 0.61 weight% 78.15 16.45 3.42 1.64 0.18 0.16 Example 2 atom% 51.34 22.50 22.50 2.77 0.27 0.61 weight% 65.54 26.75 5.56 1.78 0.20 0.17 Example 3 atom% 38.15 29.10 29.10 2.77 0.27 0.61 weight% 52.59 37.34 7.76 1.92 0.21 0.18 Example 4 atom% 66.34 18.46 11.54 2.77 0.27 0.61 weight% 75.86 19.66 2.55 1.59 0.18 0.15 Example 5 atom% 51.34 27.70 17.31 2.77 0.27 0.61 weight% 62.49 31.39 4.08 1.70 0.19 0.16 Example 6 atom% 38.15 35.81 22.38 2.77 0.27 0.61 weight% 49.22 43.02 5.59 1.80 0.20 0.17 Example 7 atom% 66.34 20.63 9.38 2.77 0.27 0.61 weight% 74.50 21.57 2.04 1.57 0.17 0.15 Example 8 atom% 51.34 30.94 14.06 2.77 0.27 0.61 weight% 60.72 34.07 3.22 1.65 0.18 0.16 Example 9 atom% 38.15 40.01 18.19 2.77 0.27 0.61 weight% 47.33 46.22 4.37 1.73 0.19 0.16

The iron-based alloy for powder injection molding was arc-dissolved under argon (Ar) atmosphere in accordance with the composition of Table 2. The alloys used for arc melting were high purity Fe (99.9 wt%), Si (99.99 wt%), C (99 wt%) and prealloyed FeB (99.2 wt%), FeS (98.5 wt%) and FeCr (98.6 wt %) It is a pre-alloy, and dissolves repeatedly by inverting 4 to 5 times to homogenize the master alloy component.

A 5 mm thick rod-shaped specimen was cast by suction casting of the master alloy prepared by arc melting. Unlike the powder injection molding process, the cast alloy is not homogenized due to sufficient diffusion, and thus, the alloy is annealed after heat treatment under conditions similar to the sintering conditions of the powder injection molding process (maintained for 30 minutes at 1200 ^° C.).

The cast and heat-treated alloys were etched with Viella solution (45 ml Glycerol, 15 ml HNO 3, 30 ml HCl) and observed by scanning electron microscopy (SEM).

Phases present in the alloy were analyzed by X-ray diffraction test, and the volume fraction of chromium boride (Cr ₂ B) was measured by an image analyzer.

The overall hardness of the alloy was measured under a load of 300 g with a Vickers hardness tester.

<Example 2>

The iron alloy for powder injection molding was melted according to the alloy compositions of Table 2 in a vacuum induction of 30 kg capacity to prepare a master alloy ingot.

The alloys used were high purity Fe (99.9 wt%), Si (99.99 wt%), C (99 wt%) and prealloyed FeB (99.2 wt%), FeS (98.5 wt%) and FeCr (98.6 wt%) It is an alloy (pre-alloy).

The ingot was again 1,550 in argon (Ar) atmosphere. ^o Spherical powder was prepared by melting with C and N ₂ gas atomization at a spray pressure of 20 bar.

This powder was classified and a powder having a size of 25 μm or less was used for powder injection molding.

In the present invention, paraffin wax was used as a binder to facilitate mixing and reduce volume expansion. 97 g of iron-based powder and 3 g of binder were mixed together with 20 ml of tungsten carbide ball and charged into a 300 ml high-density polyethylene (HDPE) container, and then heptanes up to 250 ml. I filled it up.

Mixing was carried out by rotating the vessel at 45 rpm and rotating for 24 hours. The powder mixture was dried on a 55 ^° C. hot plate and charged into a circular mold with a diameter of 13 mm and then compacted and molded using a press at room temperature at a pressure of 100 kgf / cm ² .

In order to remove the binder from the molded product, the temperature was raised to 500 ^° C. at a heating rate of 2 ^° C./min. In order to densify the degreased molded body, it was charged to a heat treatment furnace, raised to 1175 ^° C at a temperature increase rate of 3 ^° C / min. In a hydrogen atmosphere, and sintered for 1 hour.

Example 3 High Temperature Phase Equilibrium Analysis by Thermodynamic Calculation

In order to design the alloy composition changed from the basic composition of the alloy, the determination of physical properties of the alloy is identified, and the properties of the alloy (particularly hardness) are closely related to the precipitation of chromium boride (Cr ₂ B).

Accordingly, thermodynamic calculation was performed to predict the amount of chromium boride (Cr ₂ B) formation. The software used for the calculation was ThermoCalc, a commercial thermodynamic calculation program, and the thermodynamic database used an upgraded version based on TCFE2000.

2 is a Fe-Cr-B ternary isothermal state diagram prepared using this database.

Figure 3 calculates the change in the precipitation driving force of Cr ₂ B according to the composition of each component constituent (Fe, Cr, B, Si, S, C) of the base alloy at 1250 ^o C (pink) and 1000 ^o C (lime green) One result.

The precipitation driving force is calculated from the amount of the component to be adjusted in the range from 0 to twice the original amount with the ratio between the other components fixed.

It can be seen from FIG. 3 that the precipitation driving force of chromium boride (Cr ₂ B) greatly changes when the amounts of iron (Fe), chromium (Cr), and boron (B), which are the main constituents of the base alloy, are changed. Therefore, iron, chromium and boron were the main variables in the selection of the base alloy for alloy design.

When the base alloy is used for PIM, it can be considered that the sintered microstructure has reached equilibrium because it is sintered at 1,200 ^o C for a long time during the powder injection process.

The equilibrium phase fraction was calculated by adjusting the composition of iron, chromium and boron at 1,000 ^o C, which is considered to be cooling after reaching equilibrium.

The composition is based on the base alloy of Table 1 as a reference, and the sum of the molar fractions of the main components (X _Fe + X _Cr + X _B ) is maintained at 0.9634, and the ratio of Cr and B (X _Cr / X _B ) is maintained. X _Fe and (X _Cr + X _B ) were adjusted in three cases: 1.0 (increase B ratio), 1.6 (base ratio) and 2.2 (increase Cr ratio).

4 shows the fraction of equilibrium phases present at 1,000 ^° C. for three cases. As the boron ratio increases, and as the value of X _Cr + X _B increases, the equilibrium fraction of chromium boride (Cr ₂ B) increases.

In the three composition ratios, three cases of X _Cr + X _B = 0.30, 0.45, and 0.5819 were selected again to derive all nine alloy compositions, which are shown in Table 2.

First, the case where the sum of X _Cr + X _B is 0.30, 0.45, and 0.5819 was divided into Examples 1-9 based on the composition whose X _Cr / X _B ratio is 1.0, 1.6, and 2.2.

Here, Example 6 of X _Cr / X _B = 1.6, X _Cr + X _B = 0.55819 is the same as the alloy of Table 1 as the reference composition.

5 to 7 are graphs showing equilibrium phase fractions with temperatures of nine alloy compositions. This gives the thermodynamic calculation of the equilibrium fraction of chromium boride (Cr ₂ B) at various temperatures.

For example, the Cr ₂ B fraction at 1000 ^° C. in Example 1 (X _Cr / X _B = 1.0, X _Cr + X _B = 0.30) alloy composition was 43 vol. % And the rest are BCC α-Fe (ferrite) and FCC γ-Fe (austenite). When the temperature is lowered to room temperature, the fraction of Cr ₂ B is maintained and γ-Fe is transformed into α-Fe so that the room temperature microstructure is 43 vol. % Cr ₂ B and 57 vol. It can be expected to consist of% α-Fe.

< Example  4 : Fe Microstructure of Alloys>

PIM parts reach a sufficient equilibrium with prolonged sintering at high temperatures, but cast alloys may not reach equilibrium due to relatively rapid solidification by cooling after melting.

Therefore, the heat treatment corresponding to the sintering process of PIM was applied to the cast alloy in order to obtain a microstructure that reached a sufficient equilibrium state.

8 to 10 are scanning electron microscope (SEM) microstructures of alloys heat-treated after casting. Since the diffusion occurs after the heat treatment, the microstructure is significantly different from that of the cast alloy.

After prolonged storage at high temperature, martensite changes to tempered martensite, ie, ferrite, from which fine carbides are precipitated, and Cr ₂ B also changes from acicular or rod to spherical or elliptical.

As in the cast alloy, the amount of Cr ₂ B tends to increase as (X _Cr + X _B ) increases. The microstructure (Fig. 9 (f)) of the alloy of Example 6 having the same composition as the alloy of the reference composition is similar to the microstructure of the powder injection molded parts of the base alloy powder of FIG. From this, it can be expected that the microstructure of the alloy heat-treated after casting will be similar to the microstructure of the parts that have been powdered and then subjected to the PIM process.

11 is an X-ray diffraction analysis of the heat-treated alloys. Since all alloys show peaks of α-Fe (ferrite) and Cr ₂ B, it can be seen that Cr ₂ B is distributed in the ferrite matrix. The precipitated Cr ₂ B fractions were measured and shown in Table 3, and compared with the Cr ₂ B fractions obtained from Figs.

< Example  5: Fe Hardness of Alloys>

The hardness of the cast alloy and the heat-treated alloys are measured and shown in Table 3. In the same chemical composition, the hardness of the cast alloy and the heat-treated alloy is different because the microstructure of the cast alloy composed of Cr ₂ B and martensite is changed after heat treatment.

alloy Volume fraction of chromium boride (vol.%) Vickers Hardness (VHN) Calculated value After heat treatment After casting After heat treatment Example 1 48 51 1107.5 (± 60.8) 595.4 (± 37.8) Example 2 71 76 1200.5 (± 7.6) 1144.6 (± 123.7) Example 3 89 91 1649.6 (± 105.1) 1624.7 (± 125.2) Example 4 40 46 837.4 (± 52.8) 404.4 (± 14.6) Example 5 57 59 735.3 (± 14.0) 648.9 (± 170.7) Example 6 71 80 759.5 (± 33.4) 1260.5 (± 55.5) Example 7 34 42 658.0 (± 89.2) 325.7 (± 17.7) Example 8 47 47 482.8 (± 18.3) 537.0 (± 58.2) Example 9 60 66 617.6 (± 6.2) 962.5 (± 149.2)

In cast alloys, martensite changes to ferrite after heat treatment, and Cr ₂ B increases its hardness and fraction as Cr ₂ B reaches equilibrium due to the diffusion effect of high temperature heat treatment. After the heat treatment, the hardness decreases as the martensite changes to ferrite, and the hardness increases as the hardness and fraction of Cr ₂ B increases, and according to the competition between the two, the hardness of the cast alloy increases or decreases after heat treatment. Done.

That is, Cr in the high alloy composition ₂ B fraction of martensite-transformation to ferrite increases the cursor hardness after heat-treatment effect of the Cr ₂ B hardness and fraction than the hardness decreases by. On the other hand, in the alloy composition with a high ferrite fraction, the hardness reduction effect due to the martensite-ferrite transformation is greater than the increase effect of Cr ₂ B hardness and fraction, and thus tends to decrease the hardness after heat treatment.

Considering the microstructure of the alloy of Example 6 (FIG. 9 (f)) and similar to the microstructure of the component PIM with the base alloy powder (FIG. 1), the Fe-based alloys prepared in the present study were Cr ₂ B fraction and Depending on the hardness, it can be used to manufacture PIM parts.

In general, as the Cr ₂ B fraction increases, the hardness increases, but the probability of brittle fracture increases. Therefore, since high Cr ₂ B fraction and hardness are not necessarily required when applied to PIM components, it is desirable to effectively select an alloy having physical properties suitable for the physical properties required for the component.

For example, if the hardness condition required for the PIM part is 500 to 600 VHN, suitable alloys, for example, the alloys of Examples 1, 5 and 8 may be applied. In this case, brittleness may be reduced and toughness may be increased, compared to an alloy having a high hardness.

In addition, if the Cr ₂ B fraction is increased, the amount of alloying elements increases accordingly, and therefore, it is desirable to consider both the physical properties required for the PIM part as well as the economics including the price of the alloying elements.

12 is a graph showing the price of the alloying element according to the physical properties (hardness basis) required for the part. The price criteria of alloying elements were based on LME dailiy price (as of July 27, 2010).

The price of alloy element in the alloy produced in this study is low in base alloy, and the alloy element price decreases with decreasing hardness.

In addition, the price of alloying elements is higher than that of ferritic or martensitic SUS630 stainless steel (composition: Fe-17Cr-4Ni-4Cu-0.35Nb-0.07C (wt.%), Hardness: 360 VHN), which is widely used for PIM. Low replacement is possible enough.

Therefore, considering the physical properties and economics required for PIM parts, the alloy of this study can be applied to PIM parts under various conditions, and has excellent physical properties and advantageous economics.

As described above, by controlling the Cr ₂ B fraction from the present invention, which designed an alloy for PIM in which hard Cr ₂ B was distributed in a ferrite matrix, alloys having various physical properties could be successfully manufactured.

In particular, Cr ₂ B fraction and hardness were predicted from the calculation results of the high temperature equilibrium phase fraction by thermodynamic calculation, and Fe-based alloys having various Cr ₂ B fractions and hardness were prepared.

These alloys contain a lot of Cr ₂ B, which is stable at high temperatures and has excellent corrosion resistance. Therefore, the alloys are expected to be superior in temperature hardness, high temperature properties, abrasion resistance, and corrosion resistance to conventional stainless steel PIM parts. To show new possibilities.

Example 3 Since the alloy has a hardness of 1600 VHN or more, it can be sufficiently applied not only to stainless steel but also to PIM parts of cemented carbide.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

Claims (9)

In the iron-based alloy for powder injection molding,
Iron (Fe) 52.59 ~ 78.15 wt.%, Chromium (Cr) 16.45 ~ 37.34 wt.%, Boron (B) 3.42 ~ 7.76 wt.%, Silicon (Si) 1.64 ~ 1.92wt.%, Sulfur (S) 0 ~ An iron-based alloy for powder injection molding, comprising 0.21 wt.%, Carbon (C) 0.16 to 0.18 wt.%, And other unavoidable impurities. The method of claim 1,
The ratio (X _Cr / X _B ) of the chromium (Cr) and boron (B) is 1.0 for powder injection molding iron alloy. 3. The method of claim 2,
The sum (X _Cr + X _B ) of the mole fraction of chromium (Cr) and boron (B) is 0.30 to 0.60. The method of claim 3, wherein
The sum of the mole fractions of iron (Fe), chromium (Cr) and boron (B) (X _Fe + X _Cr + X _B ) is 0.9635, the iron-based alloy for powder injection molding. 5. The method of claim 4,
The microstructure of the iron-based alloy for powder injection molding is a powder injection molding iron-based alloy, characterized in that chromium boride (Cr ₂ B) is distributed in the form of a network in the ferrite (ferrite) base. The method of claim 5, wherein
The volume fraction of the chromium boride (Cr ₂ B) is 51% to 91% powder injection molding iron alloy, characterized in that. The method according to claim 6,
The powder injection molding iron-based alloy hardness of the powder injection molding iron alloy, characterized in that 600 ~ 1600 VHN. Providing a powder of the iron-based alloy for powder injection molding according to any one of claims 1 to 7;
Mixing a powder of the iron-based alloy for powder injection molding and a binder to form a powder mixture;
Compression molding the powder mixture;
Heating the powder mixture to remove the binder; And
Injection molding method of the iron-based powder comprising the step of sintering the powder mixture is the binder is removed. The method of claim 8,
The powder mixture is formed by mixing the powder of the iron-based alloy for powder injection molding according to any one of claims 1 to 7 with paraffin wax, tungsten carbide balls and heptanes in a container, and then rotating the container. Injection molding method of iron-based powder, characterized in that.

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