KR101363024B1 - Sintered steel alloy for wear resistance at high temperatures and fabrication method of valve-seat using the same - Google Patents

Abstract

The high temperature wear-resistant iron-based sintered alloy according to the present invention is employed in an engine of an internal combustion engine and, when opening and closing an intake / exhaust valve, maintains airtightness with the valve to improve thermal efficiency in the combustion chamber. In the wear-based iron-based sintered alloy, a functional part includes a seat part and a non-functional part, a support part, wherein the seat part is a mixture of sorbite and bainite. The Co-based hard particles and MnS phase are uniformly dispersed in the matrix, the support part is a structure in which fine complex carbide is dispersed in the bainite matrix, and the sheet part is 0.5-2.0 wt of chromium (Cr). %, Molybdenum (Mo) 3.5 ~ 7.5wt%, Silicon (Si) 0.1 ~ 2.0wt%, Cobalt (Co) 11.0 ~ 18.0wt%, Nickel (Ni) 0.5 ~ 2.0wt%, Manganese (Mn) 0.3 ~ 1.65wt %, Sulfur (S) 0.15 ~ 0.95wt%, carbon (C) 0.6 ~ 1.0wt%, 2.0wt% or less It contains other components and the rest is composed of Fe, the support part, chromium (Cr) 2.0 ~ 4.0wt%, molybdenum (Mo) 0.2 ~ 0.4wt%, carbon (C) 0.7 ~ 1.1wt%, 2.0wt% It includes the following other components and the rest is characterized by consisting of Fe.

Description

Sintered steel alloy for wear resistance at high temperatures and fabrication method of valve-seat using the same}

The present invention provides a valve seat for intake / exhaust valves of various internal combustion engines that can be used in common in accordance with the use conditions of unleaded gasoline, diesel, and LPG fuels according to fuel conditions, displacements, and camshaft types (DOHC, SOHC). The present invention relates to a high temperature wear resistant iron-based sintered alloy having excellent wear resistance and heat resistance and a method of manufacturing a valve sheet using the same.

In general, the engine is provided with an intake valve for sucking the mixed gas into the combustion chamber and an exhaust valve for discharging the combustion gas to the outside. The valve seat is in close contact with the face of the intake and exhaust valve, so that the pressure in the combustion chamber is leaked. It is a component that keeps the airtightness by preventing it.

The valve seat is made of an iron-based sintered alloy having wear resistance and heat resistance corresponding to an increase in operating pressure and temperature as the internal combustion engine has become smaller and higher in power. In other words, it must have strong wear resistance that will not be damaged even if it repeatedly collides with the valve which accelerates during engine operation and also opens and closes several hundreds of thousands of times per hour, and must also have strong heat resistance at the same time as it must be exposed to high temperature gas in the combustion chamber for a long time. do.

For example, since the valve sheet is operated under high impact and high temperature gas, wear resistance and corrosion resistance at high temperatures up to about 900 ° C are very severe because the operating conditions that must withstand contact with the valve, friction, and exposure to exhaust gases are very harsh. Further, there is a need for further improvement in oxidation resistance and high temperature characteristics. In addition, in recent years, as an international product of automobiles, there is a demand for a sintered alloy for valve seats that can cope with a wide range of conditions that differ depending on the imported region.

In addition, conventional high temperature wear-resistant iron-based sintered alloys for valve seats have not been used particularly for engines for LPG and alcohol fuels with severe combustion conditions. Therefore, not only the material can be used for all fuels, but there is an increasing demand for a high temperature wear resistant iron-based sintered alloy for valve sheets that can be applied to an LPG fuel engine.

In addition, in the past, lead (Pb) was added to improve the processability of the iron-based sintered alloy for valve sheets, but recently, lead is classified as an environmental pollutant and is prohibited. Therefore, high-temperature wear-resistant iron-based iron for valve sheets does not contain lead. Development of sintered alloys has become necessary.

The present invention has been made to improve the above problems, and has high wear resistance and heat resistance that can cope with high engine output, and can be applied to lead-free gasoline or diesel fuel as well as LPG fuel and alcohol fuel. And the purpose is to provide a method for producing a valve sheet using the same. In addition, as lead (Pb) is recently classified as an environmental pollutant and prohibited from use, it is intended to provide a high temperature wear resistant iron-based sintered alloy for valve sheets containing no lead.

In order to achieve the above object, the high-temperature wear-resistant iron-based sintered alloy according to the present invention is employed in an engine of an internal combustion engine, and is an engine valve for improving heat efficiency in a combustion chamber by maintaining airtightness with the valve when opening and closing an intake / exhaust valve. In the high temperature wear-resistant iron-based sintered alloy applied to the sheet,

A seat part, which is a functional part, and a support part, which is a non-functional part,

The sheet part is a structure in which Co-based hard particles and MnS phase are uniformly dispersed in a matrix structure in which sorbite and bainite are mixed.

The support part is a structure in which fine complex carbide is dispersed in the bainite matrix,

The sheet part,

Chromium (Cr) 0.5 ~ 2.0 wt%, molybdenum (Mo) 3.5 ~ 7.5wt%, silicon (Si) 0.1 ~ 2.0wt%, cobalt (Co) 11.0 ~ 18.0wt%, nickel (Ni) 0.5 ~ 2.0wt%, Manganese (Mn) 0.3 ~ 1.65wt%, sulfur (S) 0.15 ~ 0.95wt%, carbon (C) 0.6 ~ 1.0wt%, 2.0wt% or less and other components, the rest is composed of Fe,

The support part,

It contains 2.0 ~ 4.0wt% of chromium (Cr), 0.2 ~ 0.4wt% of molybdenum (Mo), 0.7 ~ 1.1wt% of carbon (C), 2.0wt% and others, and the rest is composed of Fe .

In the method for producing the alloy,

Raw material mixing step (S1) of uniformly mixing the alloy component in the mixer to have the alloy component;

A molding step of forming a molded body by compression molding the composition mixed in the raw material mixing step (S2);

A pre-sintering step (S3) of sintering and strengthening the molded body formed in the molding step in an atmosphere in which nitrogen gas (N ₂ ) and hydrogen gas (H ₂ ) are mixed at a temperature at which carbon is not diffused;

A cold forging step (S4) of charging the pre-sintered body formed in the pre-sintering step into a mold and applying a pressure of 10 to 15 ton / cm 2 to increase the density of the pre-sintered body to compactly form a matrix;

The forging body formed in the cold forging step is sintered in a mixed atmosphere of nitrogen gas (N ₂ ) and hydrogen gas (H ₂ ) at a temperature below the melting point, whereby Co-based hard particles (B) are uniformly diffused and joined to the base. And the base B forms a sorbite and bainite, and a secondary sintering step S5 for uniformly distributing the MnS phase C in a part of the pores; And

After the second sintering step, the machining and the post-process step (S6) of obtaining the finished product of the valve sheet by going through the barrel process of removing the burrs after the machining (S6), characterized in that it includes.

The high temperature wear-resistant iron-based sintered alloy and the valve sheet manufacturing method using the sintered alloy according to the present invention do not contain lead and thus do not cause environmental pollution, and have excellent wear resistance and heat resistance. This has the effect of providing valve seats that can be shared in harsh conditions such as in an engine.

1 is a microscopic structure photograph of a 200 times magnification of a structure of a sheet part of a high temperature wear resistant iron-based sintered alloy according to the present invention.
Figure 2 is a microscopic micrograph showing the structure of the support part of the high temperature wear-resistant iron-based sintered alloy according to the present invention 200 times.
3 is a process chart of a method for manufacturing a valve sheet using a high temperature wear-resistant iron-based sintered alloy according to the present invention.
4 is a diagram schematically showing the structure of a valve sheet made of a high temperature wear resistant iron-based sintered alloy according to the present invention.
5 is an experimental result showing the physical properties of the valve sheet made of a high temperature wear-resistant iron-based sintered alloy according to the present invention.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a microscopic structure photograph of a 200 times magnification of a structure of a sheet part of a high temperature wear resistant iron-based sintered alloy according to the present invention. Figure 2 is a microscopic micrograph showing the structure of the support part of the high temperature wear-resistant iron-based sintered alloy according to the present invention 200 times. 3 is a process chart of a method for manufacturing a valve sheet using a high temperature wear-resistant iron-based sintered alloy according to the present invention. 4 is a diagram schematically showing the structure of a valve sheet made of a high temperature wear resistant iron-based sintered alloy according to the present invention. 5 is an experimental result showing the physical properties of the valve sheet made of a high temperature wear-resistant iron-based sintered alloy according to the present invention.

1 to 5, a high temperature wear-resistant iron-based sintered alloy according to the present invention and a method of manufacturing a valve sheet using the sintered alloy will be described in detail.

The high temperature wear-resistant iron-based sintered alloy according to the present invention is an alloy which is employed in an engine of an internal combustion engine and is applied to an engine valve sheet for maintaining the airtightness with the valve and improving thermal efficiency in the combustion chamber when the intake / exhaust valve is opened or closed. .

The high temperature wear-resistant iron-based sintered alloy according to the present invention includes a seat part which is a functional part and a support part which is a non-functional part.

The sheet part is a structure in which Co-based hard particles and MnS phase are uniformly dispersed in a matrix structure in which sorbite and bainite are mixed.

The support part is a structure in which fine composite carbide is dispersed in the bainite matrix.

The sheet part is 0.5 to 2.0 wt% chromium (Cr), molybdenum (Mo) 3.5 to 7.5 wt%, silicon (Si) 0.1 to 2.0 wt%, cobalt (Co) 11.0 to 18.0 wt%, nickel (Ni) 0.5 ~ 2.0wt%, Manganese (Mn) 0.3 ~ 1.65wt%, Sulfur (S) 0.15 ~ 0.95wt%, Carbon (C) 0.6 ~ 1.0wt%, Other components below 2.0wt% and others are composed of Fe It is.

The support part includes chromium (Cr) 2.0 to 4.0 wt%, molybdenum (Mo) 0.2 to 0.4 wt%, carbon (C) 0.7 to 1.1 wt%, and other components of 2.0 wt% or less, and the rest is composed of Fe. It is.

The reason why the valve sheet is made of a two-layer sintered alloy of the seat part and the support part is that the seat part, which is a functional part in contact with the valve for cost reduction, is used for expensive high temperature wear resistance that meets demands for high temperature wear resistance, corrosion resistance, and oxidation resistance. It is made of iron-based sintered alloy. Since the support part only serves to support the seat part, the support part is made of a low temperature, high temperature wear resistant iron-based sintered alloy compared to the seat part.

The sheet part is a structure in which cobalt-based hard particles and MnS particles are uniformly dispersed in a mixed structure of sorbite and bainite.

The support part is a structure in which fine composite carbides of several micrometers are dispersed in the martensite matrix. The complex carbide may be, for example, (FeCrMo) C.

The reason why the alloy component of the high temperature wear-resistant iron-based sintered alloy according to the present invention is limited as in claim 1 is as follows.

The high temperature wear-resistant iron-based sintered alloy according to the present invention is composed of a sheet part which is a functional part and a two-layer material that is a support part which is a non-functional part as described above.

As shown in FIG. 1, Co-based hard particles are uniformly dispersed in the mixed structure A of sorbite and bainite, and MnS is dispersed in a part of pores.

The matrix structure A of the sheet part is prepared by the addition of an alloy powder of Fe, Co, Mo, and Ni of 180 mu m or less and carbon powder of 12 mu m or less in size.

The valve sheet made of the high temperature wear-resistant iron-based sintered alloy has a surface hardness of Hv30 220-320 and a surface hardness of the support part Hv30 270-370. In addition, the valve seat has a density of 7.0 ~ 7.5g / cc. The valve sheet has a microhardness value of about 250 to 450 mHv (100 g).

On the other hand, the microstructure of the sheet part, which is a functional site, has a CoH having a fine hardness of 600-900 mHv (100 g) in the mixed matrix structure (A) of sorbite and bainite having a fine hardness of 350-450 mHv (100g). It has a structure in which the hard particle phase (B) and MnS (C) serving as processability and solid lubricant are uniformly dispersed. MnS dispersed in the pores is excellent in self-lubrication of the product itself, and it has excellent abrasion resistance, heat resistance, corrosion resistance, oxidation resistance and high temperature characteristics against the harsh conditions of use that must withstand contact with the valve, friction, and exposure to exhaust gas. Is improved.

Co added to the matrix structure (A) of the sheet part contributes abrasion resistance by partially dispersing (Fe, Co, Mo) C, which is a complex carbide together with Fe, Mo, and C, and uniformly dispersed in the matrix metal. Is employed at the base and contributes significantly to the heat resistance. If the amount of Co added to the base is less than 6.0wt%, there is a problem in that the precipitated particles and the solid solution of the base are less abrasion resistance and heat resistance, if the Co content exceeds 7.0wt% due to the precipitated particles There is a problem that excessively vulnerable to deteriorate machinability. In addition, Co-based hard particles exist in the form of an intermetallic compound, which is a Rave phase (LAVE's PHASE), and its composition is Co (rest) -Mo (27.0-30.0wt%)-Cr (7.5-8.5wt%)-Si ( 2.3 ~ 2.8wt%), the amount is regulated from 10% to 20%. Therefore, the total amount of Co is preferably maintained at 11 to 18 wt%, including Co contained in the matrix (B) and Co contained in the Co-based hard particles (B).

Mo added to the sheet part matrix forms a composite carbide together with Fe, Co, and Cr to provide excellent wear resistance and heat resistance, and diffuses in the matrix to contribute to high temperature stability. If the content of Mo is less than 1.0wt%, there is less precipitated particles, which lowers the wear resistance. If the content of Mo is more than 2.0wt%, the base metal is vulnerable and the machinability is lowered. have. Co-based hard particles exist in the form of an intermetallic compound, which is a LAVE's PHASE, and its composition is Co (rest) -Mo (27.0-30.0wt%)-Cr (7.5 ~ 8.5wt%)-Si (2.3 ~ 2.8wt%), the amount is regulated from 10% to 20%. Therefore, the total amount of Mo is preferably maintained at 3.5 to 7.5wt%, including Mo contained in the matrix (B) and Mo contained in the Co-based hard particles (B).

Ni added to the matrix of the sheet part diffuses into the matrix metal to improve heat resistance and high temperature characteristics. If the content of Ni is less than 0.5wt, the effect of improving heat resistance and high temperature characteristics is insignificant. On the other hand, when the content of Ni exceeds 2.0wt%, the matrix structure is changed to martensite and Ni-rich austenite, resulting in unstable structure, greater hardness than necessary, and poor machinability. have.

C added to the sheet part forms a composite carbide with Co, Mo, and Ni elements added to the base and diffuses to the base, thereby improving the strength and hardness of the material to improve wear resistance, and C employed in the Fe base It works to improve strength. If the content of C is less than 0.6wt%, ferrite is excessively formed in the base metal together with the ferrite, so that the base is softened, thereby reducing the strength and wear resistance. When the content of C exceeds 1.0wt%, it is necessary to form a pearlite and the remaining C forms a cementite having a network structure, thereby making the base metal vulnerable.

MnS of 12 μm or less (part labeled C in FIG. 1) added to the matrix of the sheet part and dispersed in the pores is composed of Mn of 62.5 wt% to 54 wt% and S of 33.5 wt% to 36.5 wt% Compound. MnS does not decompose as a compound even at high temperatures and is stable, and thus remains in the pores of the sintered body in the form of MnS even after sintering. MnS provides the effect of lowering the coefficient of friction of the bite during machining to obtain a sintered body with good machinability. MnS acts as a solid lubricant to reduce the impact and friction between metals. If the content of MnS is less than 0.5wt%, its role is weak, and if the content exceeds 2.5wt%, there is a problem that the strength of the matrix is weakened and the valve sheet is destroyed when the valve sheet is pressed into the head.

Co-based hard particles (B) having a hardness of 150 μm or less added to the seat part have a value of fine hardness mHv (100 g) of 600 to 900, and do not soften even at high temperatures, and thus have excellent room temperature and high temperature wear resistance. It spreads the load under the load. The composition of the Co-based hard particle (B) is Mo 27-30 wt%, Cr 7.5-8.5 wt%, Si 2.3-2.8 wt%, C 0.03 wt% or less, and the remainder is made of Co. Cr is regulated by the amount of Cr contained only in the Co-based hard particles (B).

The amount of Co-based hard particles added is preferably 10 wt% to 20 wt%. Therefore, the content of total Cr is regulated by the amount contained only in the Co-based hard particles (B) to regulate 0.5wt% to 2.0wt%.

Si is regulated by the amount of Si contained in the Co-based hard particles (B). Therefore, the total amount of Si becomes 0.1 to 2.0 wt% contained in the Co-based hard particulate phase (B).

Other components of 2.0 wt% or less are constituted by adding a small amount of impurities to the base materials and the raw materials added in the form of hard particles.

When the amount of Co-based hard particles added is 10% to 20%, the vehicle engine displacement may be applied to a vehicle of 1000cc to less than 2000cc. Co-based hard particulate (B) is for high temperature wear resistance, when less than 10wt% is added, the contribution of high temperature wear resistance is insufficient. On the other hand, Co-based hard particles (B) is for high temperature wear resistance when added in excess of 20wt% may increase the higher temperature wear resistance than necessary.

On the other hand, the support part, which is a non-functional part, has a fine composite carbide such as (FeCrMo) C (B) of several micrometers dispersed in a martensite matrix (A) having a microhardness of mHv (100 g) 350 to 550. Have organization.

The support part is made by the addition of alloy powders of Fe, Cr, Mo, and V having a size of 212 mu m or less and carbon powder of 12 mu m or less in size.

Cr content of the support part is 2.0 ~ 4.0wt%, when the content of Cr is less than 2.0wt%, the amount of (FeCrMo) C, which is a complex carbide, is less, there is a problem that the wear resistance is inferior as the solid solution of the matrix is reduced. On the other hand, when the content of Cr exceeds 4.0wt%, the complex carbide (FeCrMo) C is excessively precipitated, and there is a problem in that the product is vulnerable due to an excessive amount of known solid solution.

The composition of Mo of the supporting part is regulated to 0.2 to 0.4 wt%. Mo added to the support part forms complex carbides with Fe, Cr, and C to provide excellent wear resistance and heat resistance, and diffuses in the base to contribute to high temperature stability. If the content of Mo is less than 0.2wt%, there is a problem in that the amount of precipitated particles is weak and wear resistance is poor. If the content of Mo exceeds 0.4wt%, there is a problem in that the addition effect of Mo is lowered because the base metal is vulnerable and the machinability is lowered.

C added to the support part is dissolved in the Fe base to improve the strength of the matrix, and the Fe, Cr, Mo and carbides (eg, (Fe, Cr, Mo) C) included in the support form the strength of the material. Improve. If the content of C is less than 0.7 wt%, ferrite is formed together with the ferrite on the base metal, so that the strength of the base is lowered. On the other hand, when the content of C exceeds 1.1wt%, the carbon consumed in the ferrite and the remaining carbon forms Cementite having a network structure, thereby weakening the base metal.

Now, a method for producing a valve sheet using the sintered alloy of the above-described components will be described.

The method of manufacturing the valve sheet, raw material mixing step (S1), forming step (S2), pre-sintering step (S3), cold forging step (S4), secondary sintering step (S5), post-processing Step S6 is included.

In the raw material mixing step (S1), the alloy components are uniformly mixed in the mixer to have the alloy components described above. The mixer used in the raw material mixing step (S1) used a double cone (Double cone) and the mixing time was 40 minutes.

In the molding step (S2) by compression molding the composition mixed in the raw material mixing step (S1) to form a molded body. In the forming step (S2) was carried out by compression molding at room temperature using an automatic molding machine was molded so that the density of the molded body is 6.8 ~ 7.0g / cc.

In the preliminary sintering step (S3), the molded article formed in the forming step (S2) is strengthened by sintering in an atmosphere in which nitrogen gas (N ₂ ) and hydrogen gas (H ₂ ) are mixed at a temperature at which carbon does not diffuse. . In the preliminary sintering step (S3), the compacted body is compressed at a temperature of A1 transformation point (723 ° C.) to A3 transformation point (910 ° C.) in the Fe-C state diagram in which only a portion of carbon (about 20%) is diffused. It is sintered in an atmosphere composed of a mixture gas of phosphorus nitrogen (N ₂ ) and hydrogen reducing gas (H ₂ ) to have a certain strength. The reason for sintering using a mixed gas of nitrogen (N ₂ ) and hydrogen (H ₂ ) as reducing gas in the preliminary sintering step (S3) is to prevent the sintered body from being affected by external environmental conditions.

In the cold forging step (S4) to charge the pre-sintered body formed in the pre-sintering step (S3) to the mold and to increase the density of the pre-sintered body by applying a pressure of 10 ~ 15 ton / ㎠ to compactly form the base. After the cold forging step (S4), the density of the tissue becomes 7.2 ~ 7.5g / cc.

In the secondary sintering step (S5), the forging body formed in the cold forging step (S4) is sintered in an atmosphere in which nitrogen gas (N ₂ ) and hydrogen gas (H ₂ ) are mixed at a temperature below a melting point, thereby hardening Co-based hard. The particulate matter B is uniformly diffused and joined to the matrix and the matrix B forms sorbite and bainite, and the MnS phase C is uniformly distributed in a part of the pores.

In the post-processing step (S6), after the second sintering step (S5), the finished product of the valve sheet is obtained by undergoing a barrel process of removing machining and burrs after the machining. The post-processing step (S6) is a general process for processing the sintered body to match the drawing dimensions, according to the processing method according to the height grinding to match the height dimension, the outer diameter polishing to match the outer diameter, and the valve sheet of the sintered body in the head Chamfering is performed to facilitate the press-fitting. Finally, after removing the remainder of the jagged edges after processing, the valve sheet of the high temperature wear-resistant iron-based sintered alloy according to the present invention is completed.

Hereinafter, the physical properties of the valve sheet made of the sintered alloy according to the present invention will be described and it will be described whether the target has sufficient performance.

As a result of analyzing the alloy components of the valve sheet manufactured by the above method, the components of the seat part were 1.5 wt% of chromium (Cr), 4.5 wt% of molybdenum (Mo), 1.3 wt% of silicon (Si), and cobalt (Co) 13.5. wt%, nickel (Ni) 1.5wt%, manganese (Mn) 1.2wt%, sulfur (S) 1.2wt%, carbon (C) 1.0wt%, and the rest was composed of other impurities and Fe.

On the other hand, the support part was made of 2.0 wt% of chromium (Cr), 0.25 wt% of molybdenum (Mo), 0.8 wt% of carbon (C), and the rest was composed of other impurities and Fe.

The valve sheet manufactured according to the embodiment of the present invention has a surface hardness of Hv30 280 of the seat part, Hv30 320 of the support part, and a density of the completed valve sheet of 7.3 g / cc, which is required by a domestic automobile manufacturer. The surface hardness Hv30 220-320 of the seat part which is a specification of a valve seat, the surface hardness Hv30 270-370 of a support part, and the density 7.0-7.4g / cc were satisfied.

In addition, unlike the conventional valve seat, by forming MnS to improve workability, lead (Pb) is not included, thereby providing an effect of preventing environmental pollution.

Thus, the high temperature wear-resistant iron-based sintered alloy and the valve sheet manufacturing method using the sintered alloy according to the present invention do not contain lead, do not cause environmental pollution, and have excellent wear resistance and heat resistance, so as well as diesel or LPG There is an effect of providing valve seats that can be shared in harsh conditions such as in fuel engines.

While the present invention has been described with reference to the preferred embodiments, it is to be understood that the invention is not to be limited by the example, and various changes and modifications may be made without departing from the spirit and scope of the invention.

A: Base tissue mixed with Sorbite and Bainite
B: Co-based hard phase
C: MnS
D: pore
S1: raw material mixing step
S2: forming step
S3: pre-sintering step
S4: cold forging step
S5: Second sintering step
S6: Finishing Step

Claims (2)

In the high-temperature wear-resistant iron-based sintered alloy that is employed in the engine of the internal combustion engine and applied to the engine valve sheet for maintaining the airtightness with the valve when opening and closing the intake and exhaust valves, to improve the thermal efficiency in the combustion chamber,
A seat part, which is a functional part, and a support part, which is a non-functional part,
The sheet part,
Chromium (Cr) 0.5 ~ 2.0 wt%, molybdenum (Mo) 3.5 ~ 7.5wt%, silicon (Si) 0.1 ~ 2.0wt%, cobalt (Co) 11.0 ~ 18.0wt%, nickel (Ni) 0.5 ~ 2.0wt%, Manganese (Mn) 0.3 ~ 1.65wt%, Sulfur (S) 0.15 ~ 0.95wt%, Carbon (C) 0.6 ~ 1.0wt%, 2.0wt% or less It contains impurities added as other components, the rest is composed of Fe ,
The support part,
It contains impurities added as chromium (Cr) 2.0 ~ 4.0wt%, molybdenum (Mo) 0.2 ~ 0.4wt%, carbon (C) 0.7 ~ 1.1wt%, 2.0wt% or less, and the rest is composed of Fe High temperature wear-resistant iron-based sintered alloy, characterized in that. In the method of manufacturing the alloy of claim 1,
Raw material mixing step (S1) of uniformly mixing the alloy component in the mixer to have the alloy component according to claim 1;
A molding step of forming a molded body by compression molding the composition mixed in the raw material mixing step (S2);
A pre-sintering step (S3) of sintering and strengthening the molded body formed in the molding step at a temperature of 723 ° C to 910 ° C in a mixture of nitrogen gas (N ₂ ) and hydrogen gas (H ₂ );
A cold forging step (S4) of charging the pre-sintered body formed in the pre-sintering step into a mold and applying a pressure of 10 to 15 ton / cm 2 to increase the density of the pre-sintered body to compactly form a matrix;
The forging body formed in the cold forging step is sintered in a mixed atmosphere of nitrogen gas (N ₂ ) and hydrogen gas (H ₂ ) at a temperature below the melting point, whereby Co-based hard particles (B) are uniformly diffused and joined to the base. And the base B forms a sorbite and bainite, and a secondary sintering step S5 for uniformly distributing the MnS phase C in a part of the pores; And
After the secondary sintering step, after the machining and the barrel process to remove the burrs after the machining (post processing) to obtain a finished product of the valve sheet (S6); high temperature wear resistance comprising Method of manufacturing a valve sheet using an iron-based sintered alloy.

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