KR100338551B1 - Sintered steel alloy for intake valve seat of internal combustion engine - Google Patents

Abstract

The present invention relates to an iron-based small alloy for intake valve seat of an internal combustion engine, which is employed in an engine of an internal combustion engine, and is used in an engine valve seat for maintaining the airtightness with the valve when opening and closing the intake valve to improve thermal efficiency in the combustion chamber. In the iron base alloy for intake valve seat of an internal combustion engine, 1.0 to 2.0 wt% Cr, 0.2 to 8.0 wt% Mo, 1.5 to 2.5 wt% Ni, 0.5 to 1.5 wt% Cu, 0.4 to 1.2 wt% C, Cr-based carbides, Mo-based carbides of several microns in size on substrates (A, BC) composed of up to 0.5% by weight of V and the remainder composed of Fe and composed of pearlite, tempered martensite and nickel rich martensite And V-carbide and tens of micron-sized hard Mo-based particles (D) are uniformly dispersed and sintered to improve wear resistance and heat resistance to cope with high engine output. c-3000cc), an iron-based small alloy for intake valve seat of an internal combustion engine which can be economically used even in use conditions such as camshaft type (DOHC, SOHC) and fuel.

Description

Sintered steel alloy for intake valve seat of internal combustion engine}

The present invention provides valve seats for intake valves of various internal combustion engines that can be shared in any condition in accordance with the use conditions such as displacement (800cc to 3000cc), camshaft type (DOHC, SOHC) and fuel. The present invention relates to an iron base alloy for intake valve seat of an internal combustion engine having wear resistance and heat resistance.

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 intake valve seat is made of an iron base 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 hundred thousand times per hour. do.

In addition, the conventional iron-based alloy for intake valve seat of the internal combustion engine has a different application material according to the use conditions such as the amount of displacement (800cc ~ 3000cc), cam-shaft type (DOHC, SOHC) and the type of fuel used .

The present invention was created to improve the above problems, and improved wear resistance and heat resistance to cope with high engine output, such as by displacement (800cc to 3000cc), camshaft type (DOHC, SOHC) and fuel An object of the present invention is to provide an iron-based small alloy for intake valve seat of an internal combustion engine that can be economically used even under operating conditions.

1 is a micrograph (× 200) showing an enlarged structure of an iron-based small alloy for intake valve seat of an internal combustion engine according to the present invention;

2 is a flow chart for explaining a method of manufacturing a valve sheet using the iron-based small alloy for intake valve sheet of the internal combustion engine according to the present invention.

<Explanation of symbols for main parts of the drawings>

A ... Perlite organization

B ... Tempered Martensite Base Organization

C ... Nickel Rich Martensite Base Structure

D ... Mo hard phase

E ... Turbine-containing pores

In order to achieve the above object, the iron-based small alloy for intake valve seat of an internal combustion engine according to the present invention is employed in an engine of an internal combustion engine, and maintains airtightness with the valve when opening and closing an intake valve, thereby improving thermal efficiency in the combustion chamber. In the iron-based small alloy for intake valve seat of an internal combustion engine applied to an engine valve seat, 1.0 to 2.0 wt% Cr, 0.2 to 8.0 wt% Mo, 1.5 to 2.5 wt% Ni, 0.5 to 1.5 wt% Cu, 0.4 Cr-based carbides of several microns in size, Mo-based, composed of a composition consisting of Felite, Tempered Martensite and Nickel Rich Martensite, consisting of -1.2 wt% C, up to 0.5 wt% V, and the remainder in Fe Carbide and V-based carbide and Mo-based hard particle phase of several tens of microns in size is uniformly dispersed and sintered.

According to the present invention, it is preferred that further 2.0% by weight or less of MnS is added to the composition.

Here, it is preferable that the pores of the sintered compact contain turbine oil for improving workability.

Therefore, when applied to the intake valve sheet using the iron-based small alloy for intake valve seat of the internal combustion engine according to the present invention, the wear resistance and heat resistance is improved to cope with the high output of the engine, according to the displacement amount (800cc ~ 3000cc), cam It is distinguished by the fact that it can be economically used even in the use conditions such as shaft type (DOHC, SOHC) and fuel.

With reference to the accompanying drawings, the iron-based small alloy for intake valve seat of the internal combustion engine according to the present invention having such characteristics will be described in detail.

As shown in Figure 1, the iron-based small alloy for intake valve seat of the internal combustion engine according to the present invention is employed in the engine of the internal combustion engine to maintain the airtightness with the valve when opening and closing the intake valve to improve the thermal efficiency in the combustion chamber It is applicable to the valve seat for intake of the engine.

Thus, the iron-based small binder is 1.0 to 2.0 wt% Cr, 0.2 to 8.0 wt%, 1.5 to 2.5 wt% Ni, 0.5 to 1.5 wt% Cu, 0.4 to 1.2 wt% C, the maximum 0.5 wt% V and the rest is Fe It is composed of a composition consisting of, has a surface hardness of HRB 80 to 110, and a density of 6.4 to 7.0 g / cc.

The iron-based small-bonded alloys, which are seen by tissue region, are composed of perlite having a microhardness of 200 to 400 mHv (100 g), tempered martensite and nickel rich having a microhardness of 350 to 550 mHv (100 g). A few microns of Cr-based carbides, Mo-based carbides and V-based carbides with mHv (100 g) in the base structures (A, B, C) of the martensite (Ni-rich martensite) matrix Micron sized hard Mo-based hard phase (D) has a uniformly dispersed structure.

In addition, it is preferable that MnS of 2.0% by weight or less is further added to the composition to improve machinability during machining as a workability improving agent. This can be utilized as the material of the excellent valve sheet which satisfies such a required characteristic according to the addition of the MnS since the small alloy of the present invention is applied to a valve sheet where wear resistance and machinability are very important. In the iron-based small alloy alloy according to the present invention, the pores (E) of the sintered compact contain oil, for example, turbine oil, for improving machinability and preventing corrosion.

When the intake valve sheet is manufactured from the iron-based small alloy, it is excellent in wear resistance and heat resistance, and can be shared in accordance with the use conditions such as displacement (800cc to 3000cc), camshaft type (DOHC, SOHC) and fuel.

When explaining the effect of the composition and the reason for the composition limitation in detail as follows.

Cr precipitates hard particles that are carbide together with C, and the precipitated hard particles are dispersed in the matrix structure to improve wear resistance and heat resistance. If the added amount is less than 1.0% by weight, the wear resistance and heat resistance are poor due to the weakness of the precipitated particles, and when the amount is more than 2.0% by weight, the substrate is embrittled due to the excessive amount of the precipitated particles, and the above effect cannot be expected, There is a risk of promoting the wear of the valve, which is a counterpart. Therefore, the preferable addition amount of the said Cr is limited to the range of 1.0-2.0 weight%.

Mo forms carbide with C to obtain excellent abrasion resistance and heat resistance, and diffuses in the base to contribute to high temperature stability. In addition, there is an effect of improving the toughness of the matrix structure of martensite. If the content is less than 0.1% by weight, the wear resistance of the precipitated particles are reduced, and if the content exceeds 0.6% by weight, the matrix structure becomes weak, and thus, the enhanced effect cannot be expected due to the decrease in the machinability. Therefore, the content is preferably limited to 0.2 to 0.6% by weight.

Ni diffuses and solidifies into the base structure together with Cr to improve heat resistance and high temperature characteristics. Therefore, if the content is less than 1.5% by weight, the above effect is insignificant, and if the content exceeds 2.5% by weight, the entire structure of the matrix is changed to martensite, thereby increasing the hardness more than necessary, and the machinability deteriorates. Along with this, Ni is an expensive metal, which is economically disadvantageous. Therefore, the content is preferably 1.5 to 2.5% by weight.

Since Cu is solid-solution in the base and improves strength, it is excellent in thermal conductivity, so that the thermal load is reduced during high temperature operation, and the coincidence of the sintered valve sheet is improved. In addition, by solid solution in Fe during the sintering process to fine precipitate on the base during cooling contributes to the improvement of wear resistance. If the content is less than 0.5% by weight, the amount of the solid solution to the base is not enough to expect the above effects, if the content exceeds 4.0% by weight unstructured particles due to the remaining unemployed particles, the dimensional change also shows the same phenomenon Therefore, dimension management becomes difficult. Therefore, Cu content is limited to the range of 0.5-4.0 weight%.

C forms carbide with other elements and diffuses to the base, thereby improving wear resistance according to the improvement of the strength and hardness of the material, and C dissolved in the Fe base improves the strength of the matrix. If the content is less than 0.4% by weight, ferrite is excessively formed together with the ferrite in the base metal, so that the base is softened, thereby reducing the strength and wear resistance. On the other hand, if the content exceeds 1.2% by weight, the carbon remaining in the pearlite forms cementite having a network structure, thereby weakening the matrix structure. Therefore, the content is preferably limited to 0.4 to 1.2% by weight.

By adding a small amount of V, the crystal grains are refined to increase toughness and at the same time to increase the print resistance at the time of tempering. In particular, strong carbides are formed and dispersed at the base, thereby causing dispersion strengthening to increase wear resistance and contribute to stability at high temperatures. If the content exceeds 0.5% by weight, it is undesirable in terms of machinability and economics.

Since MnS as a workability enhancer is stable as a compound even at high temperatures, it can remain in the sintered body in the form of MnS after sintering to obtain a sintered body with good machinability during machining. Is lowered.

Mo-based hard particle phase (D) added as a hard particle phase has a microhardness mHv (100 g) of 1000 to 1500 in size of several tens of microns, and is a high hardness hard particle phase having excellent abrasion resistance at room temperature. It plays a role. The composition of the Mo-based hard particle phase (D) itself is composed of 60.0 to 65.0 wt% Mo and the remaining Fe. What is necessary is just to set content which the Mo-type hard particle phase (D) occupies in the whole composition in consideration of the component ratio of Mo in the whole composition. For reference, the Mo component contained in the Mo-based hard particle phase (D) should not exceed 8.0% by weight in the whole composition, and the entire Mo composition in addition to the Mo component contained in the Mo-based hard particle phase (D) or In view of the fact that the Mo component added as the Mo alloy powder is included, the maximum content of the Mo-based hard particle phase (D) in the whole composition is preferably limited to about 10.0% by weight.

Therefore, the intake valve seat to which the small alloy is applied has excellent wear resistance and heat resistance to cope with the high output of the engine, and can be used for each displacement (800cc to 3000cc), cam-shaft type (DOHC, SOHC), and fuel. Depending on the conditions, the material can be shared, resulting in a simplified production line resulting in cost savings.

Hereinafter, a method of manufacturing a valve sheet using an iron-based small alloy for intake valve sheet of an internal combustion engine according to the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 2, first, a composition prepared through strict inspection, that is, 1.0 to 2.0 wt% Cr, 0.2 to 8.0 wt% Mo, 1.5 to 2.5 wt% Ni, 0.5 to 1.5 wt% Cu, 0.4 to 1.2 wt Blend the raw material composition in% C, up to 0.5% by weight V and the balance Fe. The component ratio of Mo (0.2 to 8.0% by weight) in the mixed raw material composition is the sum of the component ratio of Mo single metal powder or Mo alloy powder and the Mo component ratio contained in Mo-based hard particle phase (D) composed of Mo and Fe. . The component ratio of Fe is also the sum of the component ratios of the Fe single metal powder or the Fe alloy powder and the Fe component ratio contained in the Mo-based hard particle phase (D). Thereafter, these compositions are roughly mixed in a double cone. Mix uniformly for 40 minutes (S1).

Next, a molded article is formed by compression molding the mixed composition at room temperature with an automatic molding machine using a high precision mold (S2). The density here is approximately 6.8-7.0 g / cc.

When the molding step (S2) as described above is completed, the molded body is sintered in a mixed gas atmosphere of (N ₂ + H ₂ ) at a temperature below the melting point, that is, a general temperature of 1130 ° C (S3). In this way, Cr, Mo, and V in the composition react with C, respectively, to produce Cr-based carbides, Mo-based carbides, and V-based carbides having a size of several microns, and Mo-based hard particles having a size of several tens of microns. (D) is uniformly dispersed in matrix structures A, B, and C composed of pearlite, tempered martensite and nickel rich martensite. On the other hand, as is well known, since the amount of each of the Cr-based carbide, Mo-based carbide and V-based carbide produced during the sintering process (S3) will vary depending on the sintering conditions, Cr-based carbide produced during the sintering process (S3) It is very difficult to measure the component ratio of each of the carbides, Mo-based and V-based carbides, and the component ratios of the carbides do not significantly influence the mechanical properties of the small alloy. That is, the sintered body formed through the sintering process (S3), the mechanical properties are greatly influenced by the component ratio of each element (Cr, Mo, Ni, Cu, C, V, Fe, etc.) constituting the sintered body, each of the elements Since the component ratio of is always kept the same regardless of the amount of carbides produced, the component ratios of the carbides themselves are not important elements in the present invention. Thus, the sintered body has desired mechanical properties. Here, the reason for sintering the molded body in the atmosphere of the reducing gas is to prevent the product from reacting with the environment of the outside.

In the next step, the sintered body is subjected to heat treatment, that is, tempering, for 1 to 2 hours at a temperature of 150 to 250 ° C. to remove stresses remaining in the sintered body during sintering, and to soften the structure so that the machinability is improved. Improve (S4).

Next, in order to improve the processability of the sintered body and to prevent rusting, an oil such as turbine oil is contained in the pores E formed in the sintered body (S5).

Thereafter, the valve sheet as a finished product is obtained by going through a post-process of the barrel process for removing the machining and metal bark (S6). The post-process described above is a general process for processing a sintered body to match the drawing dimensions, and the processing method according thereto is a high-polishing to match the height dimension, an outer-polishing to match the outer diameter, and the valve seat of the sintered body is press-fitting in the head. Chamfering is performed to facilitate this.

Finally, after removing the remainder of the jagged edge portion after the processing as described above is completed the manufacture of the valve sheet of the iron base alloy according to the present invention.

In this way, the manufactured intake valve seat has a surface hardness of HRB 80 to 110, mHv (100 g) of pearlite having a micro hardness of 200 to 400, and tempered martensite having a micro hardness of 350 to 550 mHv (100 g). And several tens of microns of high hardness having microhardness of several microns of Cr-based, Mo-based, and V-based carbides and mHv (100 g) in the matrix structure (A, B, C) of nickel rich martensite. By uniform distribution of the Mo-based hard particle phase (D), the structure becomes uniform and the hardness, abrasion resistance and heat resistance are improved.

In the present invention, the iron-based small alloy for the intake valve sheet of the internal combustion engine is applied to only the intake valve sheet. However, the present invention is not limited thereto, and the present invention is applicable to other parts requiring sufficient wear resistance and heat resistance.

As described above, the iron-based small alloy for intake valve seat of the internal combustion engine according to the present invention has improved wear resistance and heat resistance to cope with high engine output, and according to displacement (800cc to 3000cc), camshaft type (DOHC). It is advantageous in that it can be economically used even in the use conditions such as SOHC) and fuel.

Claims (3)

In the iron base alloy for intake valve sheet of an internal combustion engine, which is employed in an engine of an internal combustion engine and is applied to an engine valve sheet for maintaining an airtightness with the valve when opening and closing an intake valve, thereby improving thermal efficiency in the combustion chamber. Cr-based carbides, Mo-based carbides, and V-based carbides of several microns in size and hardened Mo-based hard materials with tens of microns in the matrix (A, BC) organized by pearlite, tempered martensite and nickel rich martensite The sintered compact in which the particulate-form D is disperse | distributed uniformly, The composition ratio of the component which comprises the said sintered compact is 1.0-2.0 weight% Cr, 0.2-8.0 weight% Mo, 1.5-2.5 weight% Ni, 0.5-1.5 weight% Cu , 0.4 to 1.2% by weight C, the maximum 0.5% by weight V, the remainder is Fe, the pores (E) formed in the sintered body contains a turbine oil for improving workability, the intake valve seat of the internal combustion engine Iron-based small bonds. The method of claim 1, Iron-based small alloy for intake valve seat of the internal combustion engine, characterized in that the addition of more than 2.0% by weight of MnS to the composition. delete