Method for manufacturing high-hardness heat-resistant steel parts using metal powder injection molding and high-hardness heat-resistant steel parts manufactured by the same

Abstract

The present invention relates to a method for manufacturing high-hardness, high-heat-resistant steel parts using metal powder injection molding and high-hardness, high-heat-resistant steel parts manufactured by said method, and in particular, to a method for manufacturing turbocharger parts for gasoline engines using DIN 1.4957 (GX15CrNiCo21-20-20) powder, which is a high-heat-resistant steel material that can be used even in high-temperature environments of 1,000°C or higher, and high-hardness, high-heat-resistant steel parts manufactured by said method. The high-hardness, high-heat-resistant steel parts manufactured according to the present invention have surface hardness and core hardness of 220 HV1 or higher, and have excellent weldability with other turbocharger parts.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a high-hardness, high-heat-resistant steel part using metal powder injection molding and a high-hardness, high-heat-resistant steel part manufactured by said method, and in particular, to a method for manufacturing a high-hardness, high-heat-resistant steel part capable of being used in a high-temperature environment of 1,000°C or higher using a metal powder injection molding method and a high-hardness, high-heat-resistant steel part manufactured by said method.

[0002] More specifically, the present invention relates to a method for manufacturing a high-hardness turbocharger part using a metal powder injection molding method with a DIN 1.4957 (GX15CrNiCo21-20-20) powder that can be used in high-temperature environments by adding a large amount of cobalt in addition to nickel, and to a turbocharger part manufactured by said method. Background Technology

[0003] Globally, various eco-friendly vehicles such as electric vehicles and hydrogen fuel cell vehicles have been commercialized to prevent global warming and air pollution caused by automobile emissions, and new technologies for eco-friendly vehicles are being introduced.

[0004] However, considering that vehicles using internal combustion engines still account for the majority, technology regarding automotive superchargers that can reduce exhaust emissions and improve fuel efficiency remains important.

[0005] A turbocharger refers to a supercharger for an engine driven by exhaust gases. It is a device that combines a supercharger with a turbine to drive it, and is commonly referred to simply as a turbo. In other words, a turbocharger is a device that recovers energy from exhaust gases using a turbine, compresses external air with a compressor, and sends that compressed air to the engine. Because turbochargers have characteristics such as reducing exhaust emissions, improving engine specific power output, enhancing fuel efficiency, and increasing high-altitude performance, they are currently widely utilized in the automotive and aviation engine sectors.

[0006] Among them, the Variable Turbocharger Geometry (VTG) is increasingly being utilized as it improves the efficiency of the turbocharger at low RPMs by installing vanes whose angles change according to the exhaust gas flow rate, laying the vanes flat at low speeds and raising them at high speeds to induce the exhaust to flow quickly.

[0007] Since the supercharger uses the energy from the incoming exhaust gas, the surface of the component is naturally exposed to a high-temperature and high-pressure gas atmosphere, and the exhaust gas contains components that corrode metal materials, so the supercharger material was made of heat-resistant steel such as HK-30, which has excellent heat resistance and oxidation resistance.

[0008] Meanwhile, although superchargers were initially developed for diesel engines, recently, due to environmental regulations, the demand for diesel engines has decreased and they are being actively applied to gasoline engines instead. As a result, the operating environment for superchargers has become considerably harsher compared to the past.

[0009] In the case of diesel engines, since they are operated under an air-excess condition where the fuel-to-air supply ratio is about 1 to 20 or more, the exhaust gas temperature is up to about 850°C, and conventional heat-resistant steels such as HK-30 can be used.

[0010] On the other hand, in the case of gasoline engines, the theoretical fuel-to-air mixture ratio is about 1 to 14.5, which is higher than that of diesel engines, so the exhaust gas temperature reaches about 1,050°C. Due to this difference in operating environment, turbochargers for gasoline engines require high heat-resistant steel materials capable of operating in an environment of at least 1,000°C to cope with high exhaust gas temperatures.

[0011] Therefore, there is a need to develop turbocharger components using DIN 1.4957 (GX15CrNiCo21-20-20) material as a raw material, which is one of the high heat-resistant steels capable of being used at temperatures above 1,000°C. However, DIN 1.4957 (GX15CrNiCo21-20-20) material has the problem that it is difficult to manufacture high-hardness components that are resistant to the operating environment of turbochargers through a general casting process.

[0012] Therefore, there is a need to develop turbocharger parts that have excellent heat resistance, such as DIN 1.4957 (GX15CrNiCo21-20-20) materials, high hardness suitable for turbocharger parts, and can be stably assembled and welded with other parts during assembly. The problem to be solved

[0013] The present invention relates to a method for manufacturing a high-hardness, high-heat-resistant steel part using metal powder injection molding and a high-hardness, high-heat-resistant steel part manufactured by the said method. In particular, the invention aims to provide a method for manufacturing a gasoline engine turbocharger part having a high hardness of 220 HV1 or higher using a DIN 1.4957 (GX15CrNiCo21-20-20) powder, which is a high-heat-resistant steel material capable of being used in high-temperature environments of 1,000°C or higher, but which is difficult to manufacture a high-hardness part capable of withstanding the operating environment of a turbocharger through a general casting process, by using metal powder injection molding and sintering technology, and to provide a gasoline engine turbocharger part manufactured by the said method that has excellent weldability. means of solving the problem

[0014] A method for manufacturing a high-hardness, high-heat-resistant steel component according to the present invention comprises: a step of preparing a feedstock by mixing high-heat-resistant steel metal powder with a binder; a step of preparing a green molded body by injection molding the prepared feedstock; a step of preparing a degreased body by degreasing the green molded body; and a step of sintering the degreased body under a nitrogen atmosphere.

[0015] There are no restrictions on the above high heat-resistant steel metal powder, but high heat-resistant steel materials such as DIN 1.4957 (GX15CrNiCo21-20-20) can be used.

[0016] The manufacturing method according to the present invention has the advantage of being able to provide high-hardness turbocharger parts for gasoline engines by using DIN 1.4957 (GX15CrNiCo21-20-20) material, which is one of the high-heat-resistant steels that can be used at temperatures of 1,000°C or higher, but is difficult to manufacture high-hardness parts through a general casting process.

[0017] The step of sintering the degreased body under a nitrogen atmosphere in the method for manufacturing a high-hardness, high-heat-resistant steel part according to the present invention may have a maximum sintering temperature of 1,230°C or higher, a sintering time of 3 hours or more, and a partial nitrogen pressure of 75 to 115 torr, and the step of sintering the degreased body under a nitrogen atmosphere may have a maximum sintering temperature of 1,240°C or higher, a sintering time of 1 hour or more, and a partial nitrogen pressure of 75 to 115 torr.

[0018] If the maximum sintering temperature is less than 1,230℃ and the sintering time is less than 3 hours, or if the maximum sintering temperature is less than 1,240℃ and the sintering time is less than 1 hour, many pores are formed inside the sintered body, resulting in low density and making it difficult for the core hardness of the sintered body to exceed 220HV1, so sufficient high heat resistance cannot be expected.

[0019] In addition, if the nitrogen partial pressure is less than 75 torr, sufficient nitride is not formed, so a high-hardness sintered body cannot be manufactured, and if the nitrogen partial pressure exceeds 115 torr, the weldability of the sintered body decreases.

[0020] The step of preparing a feedstock by mixing high-heat-resistant steel metal powder with a binder in the method for manufacturing a high-hardness high-heat-resistant steel part according to the present invention may include mixing 55 to 70 volume% of high-heat-resistant steel metal powder with 45 to 30 volume% of a binder.

[0021] The binder may comprise 40-60% by weight of wax, 10-30% by weight of polypropylene polymer, 10-30% by weight of polyethylene polymer, and 20-60% by weight of polyacetal polymer, and may comprise 40-60% by weight of wax, 1-10% by weight of stearic acid, 1-20% by weight of EVA polymer, 10-30% by weight of polypropylene polymer, 10-30% by weight of polyethylene polymer, and 20-60% by weight of polyacetal polymer.

[0022] The above wax may include one or more selected from paraffin wax or carnauba wax.

[0023] The present invention may provide a high-hardness, high-heat-resistant steel part manufactured according to the method for manufacturing the high-hardness, high-heat-resistant steel part, and the high-hardness, high-heat-resistant steel part may be a turbocharger part for a gasoline engine requiring welding, and preferably may be a vane or vane lever used in the turbocharger.

[0024] The above high-hardness, high-heat-resistant steel parts may have a surface hardness and core hardness of 220 HV1 or higher and a nitrogen content of less than 0.299 weight%, and the high-hardness, high-heat-resistant steel parts having the above characteristics can be used in turbochargers for gasoline engines operated in environments of 1,000°C or higher, and have excellent assembly and weldability with other turbocharger parts. Effects of the invention

[0025] The present invention relates to a method for manufacturing a high-hardness, high-heat-resistant steel part using metal powder injection molding and a high-hardness, high-heat-resistant steel part manufactured by said method. It provides a method for manufacturing a turbocharger part that has high hardness and high heat resistance suitable for use in a gasoline engine turbocharger, and is capable of assembly and welding with other turbocharger parts, by using DIN 1.4957 (GX15CrNiCo21-20-20) powder, which is a high-heat-resistant steel material capable of being used in a high-temperature environment of 1,000°C or higher, and can provide a turbocharger part manufactured according to said method. Brief explanation of the drawing

[0026] FIG. 1 is a photograph of a green molded body (a) and a sintered body (b) manufactured by the manufacturing method according to the present invention. Figure 2 is a micrograph of cross-sections of sintered bodies prepared at different sintering temperatures of 1,230℃ (a), 1,250℃ (b), and 1,270℃ (c). Figure 3 shows the welding condition of a sintered body, where (a) shows a case where the welding condition is poor and (b) shows a case where the welding condition is good. Specific details for implementing the invention

[0027] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the present invention, and the present invention is defined only by the scope of the claims.

[0028] The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the components mentioned.

[0029] Unless otherwise defined, all terms used herein (including technical and scientific terms) may be used in a meaning commonly understood by those skilled in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0031] The present invention relates to a method for manufacturing a high-hardness, high-heat-resistant steel part using metal powder injection molding and a high-hardness, high-heat-resistant steel part manufactured by said method.

[0032] A method for manufacturing a high-hardness, high-heat-resistant steel part using metal powder injection molding according to the present invention may include the steps of: mixing high-heat-resistant steel metal powder with a binder to produce a feedstock; injection molding the produced feedstock to produce a green molded body; degreasing the green molded body to produce a degreased body; and sintering the degreased body under a nitrogen atmosphere.

[0033] The high heat-resistant steel metal powder according to the present invention is not limited to any metal powder that can be used in an environment of 1,000°C or higher, but preferably, a DIN 1.4957 (GX15CrNiCo21-20-20) based material may be used.

[0034] The above DIN 1.4957 (GX15CrNiCo21-20-20) material is a high-heat-resistant steel material manufactured to be usable in high-temperature environments by adding a large amount of cobalt in addition to nickel, but it is difficult to manufacture high-hardness parts through a general casting process. However, by the method for manufacturing high-hardness high-heat-resistant steel parts using metal powder injection molding according to the present invention, it is possible to obtain a high hardness of 220 HV1 or higher that can be used in turbocharger parts for gasoline engines having a usage environment of about 1,000°C or higher.

[0035] The binder according to the present invention is not limited, but a binder comprising 40-60% by weight of wax, 10-30% by weight of polypropylene polymer, 10-30% by weight of polyethylene polymer, and 20-60% by weight of polyacetal polymer may be used, and preferably a binder comprising 40-60% by weight of wax, 1-10% by weight of stearic acid, 1-20% by weight of EVA polymer, 10-30% by weight of polypropylene polymer, 10-30% by weight of polyethylene polymer, and 20-60% by weight of polyacetal polymer may be used, and the wax may be paraffin wax or carnauba wax used alone or in combination.

[0036] There are no limitations on the content of the high heat-resistant steel metal powder and binder constituting the feedstock according to the present invention, but 55 to 70 volume% of the metal powder and 45 to 30 volume% of the binder may be used, and preferably 60 to 65 volume% of the metal powder and 40 to 35 volume% of the binder may be used.

[0037] The sintering step according to the present invention may have a maximum sintering temperature of 1,230°C or higher and a sintering time of 3 hours or more at the maximum sintering temperature, a maximum sintering temperature of 1,240°C or higher and a sintering time of 1 hour or more at the maximum sintering temperature, preferably a maximum sintering temperature of 1,250 to 1,270°C, more preferably a maximum sintering temperature of 1,250 to 1,260°C and a sintering time of 1 to 3 hours at the maximum sintering temperature.

[0038] The above sintering step is preferably carried out under a nitrogen atmosphere, and in particular, the partial pressure of nitrogen may be 75 to 115 torr, preferably 80 to 110 torr, and more preferably 90 to 100 torr.

[0039] If the maximum sintering temperature is less than 1,230℃ and the sintering time is less than 3 hours, or if the maximum sintering temperature is less than 1,240℃ and the sintering time is less than 1 hour, many pores are formed inside the sintered body, resulting in low density and making it difficult for the core hardness of the sintered body to exceed 220HV1, so sufficient high heat resistance cannot be expected.

[0040] In addition, if the nitrogen partial pressure is less than 75 torr, sufficient nitride is not formed, so a high-hardness sintered body cannot be manufactured, and if the nitrogen partial pressure exceeds 115 torr, the weldability of the sintered body decreases.

[0041] In the above sintering step, the process of raising the temperature to the maximum sintering temperature can be carried out in 2.5±1 hours from room temperature to 600℃, 2.5±1 hours from 600℃ to 950℃, and 2±1 hours from 950℃ to 1,250℃, and preferably in 2.5 hours from room temperature to 600℃, 2.5 hours from 600℃ to 950℃, and 2 hours from 950℃ to 1,250℃, and nitrogen can be injected at a temperature of 600℃ or higher.

[0042] The high-hardness, high-heat-resistant steel part according to the present invention is not limited to any part that can be used in an environment of 1,000°C or higher, but preferably may be a turbocharger part for a gasoline engine, and in particular may be a vane or vane lever that is assembled with other parts by welding.

[0043] Hereinafter, embodiments of the present invention will be described in detail.

[0045] A metal powder binder mixture (feedstock) was prepared by mixing 60 volume% of DIN 1.4957 (GX15CrNiCo21-20-20) high heat-resistant steel raw material with an average particle size (D50) of 8㎛ and 40 volume% of binder using a mixer set to 165±5℃ for about 90 minutes.

[0046] The above DIN 1.4957 (GX15CrNiCo21-20-20) series high heat-resistant steel raw material may consist of 0.25~0.35 wt% carbon, 0.1~0.2 wt% nitrogen, 2.7~3.0 wt% tungsten, 20~22.5 wt% chromium, 19~21 wt% nickel, 0.75~1.25 wt% niobium, 1~2 wt% manganese, 18.5~21.0 wt% cobalt, 1.3~1.8 wt% silicon, 2.5~3.5 wt% molybdenum, and the remainder being iron.

[0047] As the binder above, a binder was used in which 30% by weight of paraffin wax, 5% by weight of carnauba wax, 10% by weight of EVA polymer, 15% by weight of polypropylene polymer, 15% by weight of polyethylene polymer, and 25% by weight of polyacetal polymer were mixed.

[0048] The above feedstock was crushed using a crusher and then injected into a mold that fits the vane shape of a turbocharger set to 45±5℃ using a 50-ton injection molding machine to produce a green molded body. The green molded body is shown in FIG. 1 (a).

[0049] A degreased body was prepared by raising the green molded body from room temperature to 620±20℃ and maintaining it, while simultaneously supplying nitrogen gas at a flow rate of 140±5L / min to remove all the binder. The degreasing process was carried out for approximately 24 hours from the raising of the temperature to the cooling.

[0050] The above degreasing body was placed in a sintering furnace and heated to the set maximum sintering temperature through a heating process of 7 hours from room temperature, and sintering was carried out under vacuum with nitrogen gas controlled to a low partial pressure.

[0051] The above heating process was carried out in 2.5 hours from room temperature to 600℃, 2.5 hours from 600℃ to 950℃, and 2 hours from 950℃ to 1,250℃, and nitrogen was injected at a temperature of 600℃ or higher.

[0053] Table 1 shows the results of evaluating the surface hardness, core hardness, density, porosity, and grain size of sintered bodies (see Fig. 1 (b)) prepared at different maximum sintering temperatures and sintering times at maximum sintering temperatures under a nitrogen partial pressure of 170 torr.

[0054] Maximum sintering temperature (°C) Sintering time (hr) Density (g / cc) Porosity (%) Hardness (HV1) Crystal grain size Grain size (㎛) surface Deep Example 1 1,230 0 7.07 12.1 209 183 12.7 4.85 Example 2 1 7.50 8.7 223 218 11.9 5.18 Example 3 2 7.71 5.2 236 216 10.8 7.58 Example 4 3 7.78 3.6 245 232 10.4 8.70 Example 5 1,250 0 7.28 9.5 221 200 10.0 9.94 Example 6 1 7.86 3.5 242 245 9.8 10.71 Example 7 2 7.91 2.9 242 242 10.0 10.00 Example 8 3 7.93 2.8 250 242 9.5 11.89 Example 9 1,270 0 7.79 3.2 236 217 8.7 15.85 Example 10 1 7.98 3.2 251 225 7.7 22.19 Example 11 2 7.97 2.2 235 223 5.5 47.56 Example 12 3 8.00 2.2 241 226 5.2 52.7

[0055] As shown in Table 1, as the maximum sintering temperature increased and the sintering time at the maximum sintering temperature increased, the density of the sintered body increased, the porosity decreased, the crystal grain size decreased, and the crystal grain size increased.

[0056] However, regarding hardness, in Examples 1 to 8, where the sintering temperatures were set to 1,230°C and 1,250°C, surface hardness and core hardness gradually increased as the sintering time increased. On the other hand, when the sintering temperature was 1,270°C, surface hardness tended to increase and then decrease as the sintering time increased, while core hardness did not show significant changes. (Refer to Examples 9 to 12)

[0057] And it was confirmed that the difference between the surface hardness and core hardness of the sintered body sintered at 1,250°C (see Examples 6-8) was small compared to the case where the maximum sintering temperature was 1,230°C and 1,270°C.

[0058] In FIG. 2, microscopic cross-sectional views of the sintered bodies of Examples 3, 7, and 11 are shown in (a), (b), and (c), respectively.

[0059] It can be observed that at a sintering temperature of 1,230℃, many pores are formed, resulting in low density, and at 1,270℃, the carbides formed inside the grains are unevenly distributed. When sintered at 1,250℃, it can be observed that the carbides inside the grains are refined and evenly distributed.

[0060] It is known that the fine and uniform distribution of carbides hinders grain growth and refines the grains, thereby improving the mechanical strength of the sintered body. Due to this effect, it is determined that the sintered body sintered at 1,250°C (see Examples 6-8) has a high hardness value while having a small difference between surface hardness and core hardness.

[0061] From the results of Table 1 above, it can be seen that in order to stably manufacture a sintered body suitable for the operating environment of a turbocharger for a gasoline engine with surface hardness and core hardness of 220 HV1 or higher, sintering at 1,230°C for 3 hours or more is required, and sintering at a maximum sintering temperature of 1,250°C or higher for 1 hour or more is required.

[0063] Table 2 shows the results of evaluating the physical properties and weldability of sintered bodies according to nitrogen partial pressure at the maximum sintering temperature and sintering time capable of producing sintered bodies with surface hardness and core hardness of 220 HV1 or higher among Examples 1 to 12.

[0064] Table 2 shows the results of evaluating the density, surface hardness, core hardness, nitrogen content, and weldability of sintered bodies prepared by setting the maximum sintering temperature and maximum sintering temperature to 1,230℃ for 3 hours and 1,250℃ and 1,270℃ for 2 hours, respectively, and varying the partial pressure of nitrogen in the sintering process.

[0065] Weldability was determined by whether the sintered vane-shaped sintered body could be welded well with the vane lever among the turbocharger parts, and '×' indicates poor weldability, such as sparks occurring during welding and a poor weld surface (see Fig. 3 (a)), and '○' indicates good weldability (see Fig. 3 (b)).

[0066] Maximum sintering temperature (°C) Sintering time (hr) Nitrogen partial pressure (torr) Density (g / cc) Hardness (HV1) Nitrogen content (weight%) weldability surface Deep Example 13 1,230 3 130 7.78 239 230 0.343 × Example 14 110 7.81 237 229 0.236 ○ Example 15 80 7.79 228 223 0.172 ○ Example 16 50 7.77 219 208 0.162 ○ Example 7 1,250 2 170 7.91 242 242 0.386 × Example 17 130 7.79 241 233 0.347 × Example 18 120 7.89 240 230 0.299 × Example 19 110 7.85 238 230 0.241 ○ Example 20 100 7.81 237 230 0.210 ○ Example 21 90 7.84 234 229 0.181 ○ Example 22 80 7.83 230 225 0.179 ○ Example 23 50 7.80 220 210 0.174 ○ Example 24 30 7.81 185 180 0.131 ○ Example 25 2~5 7.81 180 177 0.099 ○ Example 26 1,270 2 130 7.95 233 224 0.354 × Example 27 110 7.93 230 224 0.243 ○ Example 28 80 7.97 229 222 0.182 ○ Example 29 50 7.95 222 213 0.175 ○ Comparative example Argon 2~5 7.81 176 176 0.010 ○

[0067] As shown in Table 2, when the nitrogen partial pressure is very low (see Comparative Example, Example 25), it can be seen that almost no nitrides are formed in the sintered body and the sintered body does not possess sufficient hardness. As the nitrogen partial pressure increases to 30 torr or higher, the nitrogen content within the sintered body increases, and both surface hardness and core hardness also increase; this is because nitrogen is introduced to the grain surface to form nitrides. However, it can be seen that the change in density with increasing nitrogen partial pressure is not very significant (see Examples 7, 17–24).

[0068] From Table 2, it can be seen that a partial nitrogen pressure of 80 torr or higher is required to stably manufacture a sintered body with surface hardness and core hardness of 220 HV1 or higher. (See Examples 15, 22, and 28)

[0069] However, as the nitrogen partial pressure increases, if the nitrogen content of the sintered body increases to 0.299 wt% or more (see Examples 7, 13, 17, 18, and 26), sparks occur during welding, and as shown in FIG. 3 (a), problems arise in which the vane lever and the weld surface are not formed cleanly. Therefore, in order for the sintered body to have good weldability (see FIG. 3 (b)), the nitrogen content of the sintered body must be less than 0.299 wt%, so the nitrogen partial pressure during sintering also needs to be set to less than 120 torr.

[0071] As can be seen from the above examples, in order to produce a turbocharger component capable of operating at 1,000°C or higher using a high heat-resistant steel of the DIN 1.4957 (GX15CrNiCo21-20-20) system by metal powder injection molding, it is required that the maximum sintering temperature be 1,230°C or higher and the sintering time at the maximum sintering temperature be 3 hours or more, or at a maximum sintering temperature of 1,240°C or higher, preferably 1,250 to 1,270°C, more preferably 1,250 to 1,260°C, the sintering time be 1 hour or more, preferably 1 to 3 hours, more preferably 2 to 3 hours, and sintering be required under a nitrogen partial pressure of 75 to 115 torr, preferably 80 to 110 torr, more preferably 90 to 100 torr.

[0072] The high-hardness, high-heat-resistant steel part manufactured according to the present invention has a surface hardness and core hardness of 220 HV1 or higher, and a nitrogen content of less than 0.299 weight%, and has excellent weldability with other turbocharger parts.

Claims

Claim 1 A method for manufacturing a high-hardness, high-heat-resistant steel part using metal powder injection molding, comprising: a step of preparing a feedstock by mixing high-heat-resistant steel metal powder of DIN 1.4957 (GX15CrNiCo21-20-20) system material with a binder; a step of preparing a green molded body by injection molding the prepared feedstock; a step of preparing a degreased body by degreasing the green molded body; and a step of sintering the degreased body under a nitrogen atmosphere; wherein the step of sintering the degreased body under a nitrogen atmosphere is characterized in that the maximum sintering temperature is 1,230°C or higher, the sintering time at the maximum sintering temperature is 3 hours or higher, the partial pressure of nitrogen is 75 to 115 torr, and the high-hardness, high-heat-resistant steel part has a surface hardness and core hardness of 220 HV1 or higher and a nitrogen content of less than 0.299 wt%. Claim 2 A method for manufacturing a high-hardness, high-heat-resistant steel part using metal powder injection molding, comprising: a step of preparing a feedstock by mixing high-heat-resistant steel metal powder of DIN 1.4957 (GX15CrNiCo21-20-20) system material with a binder; a step of preparing a green molded body by injection molding the prepared feedstock; a step of preparing a degreased body by degreasing the green molded body; and a step of sintering the degreased body under a nitrogen atmosphere; wherein the step of sintering the degreased body under a nitrogen atmosphere is characterized in that the maximum sintering temperature is 1,240°C or higher, the sintering time at the maximum sintering temperature is 1 hour or higher, the partial pressure of nitrogen is 75 to 115 torr, and the high-hardness, high-heat-resistant steel part has a surface hardness and core hardness of 220 HV1 or higher and a nitrogen content of less than 0.299 wt%. Claim 3 A method for manufacturing a high-hardness, high-heat-resistant steel part using metal powder injection molding, wherein, in claim 1 or 2, the step of mixing the high-heat-resistant steel metal powder with a binder to produce a feedstock is characterized by mixing 55 to 70 volume% of the high-heat-resistant steel metal powder with 45 to 30 volume% of the binder. Claim 4 A method for manufacturing a high-hardness, high-heat-resistant steel part using metal powder injection molding according to claim 3, wherein the binder comprises 40-60% by weight of wax, 10-30% by weight of polypropylene polymer, 10-30% by weight of polyethylene polymer, and 20-60% by weight of polyacetal polymer. Claim 5 A method for manufacturing a high-hardness, high-heat-resistant steel part using metal powder injection molding according to claim 4, wherein the binder comprises 40-60% by weight of wax, 1-10% by weight of stearic acid, 1-20% by weight of EVA polymer, 10-30% by weight of polypropylene polymer, 10-30% by weight of polyethylene polymer, and 20-60% by weight of polyacetal polymer. Claim 6 A method for manufacturing a high-hardness, high-heat-resistant steel part using metal powder injection molding according to claim 4, wherein the wax comprises one or more selected from paraffin wax or carnauba wax. Claim 7 High-hardness, high-heat-resistant steel part using metal powder injection molding manufactured by the manufacturing method according to claim 1 or 2. Claim 8 A high-hardness, high-heat-resistant steel part according to claim 7, characterized in that the high-hardness, high-heat-resistant steel part is a turbocharger part for a gasoline engine. Claim 9 A high-hardness, high-heat-resistant steel part according to claim 8, characterized in that the turbocharger part for a gasoline engine is a vane or a vane lever. Claim 10 delete Claim 11 A high-hardness, high-heat-resistant steel part manufactured by molding high-heat-resistant steel metal powder of DIN 1.4957 (GX15CrNiCo21-20-20) system material using a metal powder injection molding method, followed by degreasing and sintering, wherein the high-hardness, high-heat-resistant steel part is characterized by having a surface hardness and core hardness of 220 HV1 or higher and a nitrogen content of less than 0.299 wt%.

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