KR100338058B1 - Sintered alloy having superior wear resistance and process of manufacture therefor - Google Patents

Abstract

The present invention provides a sintered material having high material strength and excellent wear resistance and a method of manufacturing the same. Small bonds with good abrasion resistance have a total composition of 6.0 to 25 wt% Ni, 0.6 to 8.75 wt% Cr, 0.54 to 2.24 wt% C and Fe residues, and the core of Cr carbide and Cr surrounding the nucleus A hard phase composed of a diffused ferrite phase or a mixed phase of a ferrite and Cr diffused austenite exhibits a metal structure dispersed in a mixed structure of martensite and austenite, and austenite in the mixed structure of the metal structure The area ratio is 5 to 30%.

Description

Abrasion Resistant Sintered Alloy and its Manufacturing Method {Sintered alloy having superior wear resistance and process of manufacture therefor}

TECHNICAL FIELD The present invention relates to a wear resistant small alloy alloy having excellent wear resistance and a method of manufacturing the same, and more particularly, to a technique suitable for use in a valve seat for an internal combustion engine.

Background Art In recent years, automotive engines have become more stringent in terms of operating performance, and inevitably, the valve seats used in engines have to withstand more stringent operating environmental conditions. From this request, the applicant has previously disclosed, for example, Japanese Patent Publication No. 17968/74, Patent Publication No. 36242/80, Patent Publication No. 56547/82, Patent Publication No. 55593/93 and Patent Publication No. 98985/95 proposes a variety of small alloys with excellent wear resistance.

Among the wear-resistant small-kneading alloys relating to the above-mentioned proposals, in particular, the small-kneading alloy disclosed in Japanese Patent Publication No. 55593/93 is based on the alloy disclosed in Japanese Patent Publication No. 36242/80, and has a hard phase composed of Mo silicide in its matrix structure. It shows the metal structure which the diffused phase which Co diffused around surrounds, and shows the outstanding wear resistance by presence of a hard phase. The wear resistant sintered alloy disclosed in Japanese Patent Publication No. 98985/95 contains 5 to 27% by weight of Ni in the alloy disclosed in Japanese Patent Publication No. 55593/93, thereby enhancing the matrix structure to further improve wear resistance. will be.

However, since these alloys use expensive materials such as Co to form hard phases, it is expected that they will not meet the recent cost-performance demands. In other words, the recent development of automobiles is not only aiming at high performance, but also the development of inexpensive automobiles with an emphasis on economics. Therefore, the present applicant has proposed a wear-resistant small bond alloy capable of exerting the wear resistance required by low-cost materials in Patent Publication No. 195012/97. In this proposal, the base powder is strengthened using a powder obtained by partially diffusing Ni, Cu, and Mo powder in Fe powder as the matrix powder, and the hard phase mainly composed of Cr carbide is dispersed in this matrix structure, thereby increasing the cost of Co and the like. It provides the required wear resistance and strength without using materials.

By the way, the demand for performance-to-price ratio is increasing year by year, and the demand for abrasion-resistant small-kneading alloy for valve seat is higher than the wear-resistant small-kneading alloy related to the above proposal. Therefore, since expensive Mo is used also in the above-mentioned wear-resistant small bond alloy, there exists a possibility of further improvement in terms of a used material.

At present, it is a phenomenon that the operating conditions become even more severe due to the higher performance of automobile engines, and a material having better wear resistance and strength than the above-described small alloys is desired.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a wear-resistant sintered material and a method for producing the same, which can further improve material strength and wear resistance without using expensive materials.

1 is a view schematically showing the metal structure of the wear-resistant small alloy of the present invention,

2 is a graph showing the relationship between the amount of Ni, the amount of wear and the radial crushing strength in the embodiment of the present invention;

3 is a graph showing the relationship between the amount of Ni and the amount of austenite in an embodiment of the present invention;

4 is a graph showing the relationship between the amount of austenite and the amount of wear in the embodiment of the present invention;

5 is a graph showing the relationship between the amount of graphite powder added, the amount of abrasion, and the rolling strength in the embodiment of the present invention;

6 is a graph showing the relationship between the amount of hard phase forming powder added, the amount of abrasion and the crushing strength in the Examples of the present invention;

7 is a graph showing the relationship between the amount of Cr in the hard phase forming powder and the amount of wear and the rolling strength in the embodiment of the present invention;

8 is a graph showing the relationship between the amount of C in the hard phase forming powder and the amount of wear and the crushing strength in the Examples of the present invention;

9 is a graph showing the relationship between the amount of Mo in the hard phase forming powder and the amount of wear and the rolling strength in the Examples of the present invention;

10 is a graph showing the relationship between the amount of V in the hard phase forming powder and the amount of wear and the crushing strength in the Examples of the present invention;

11 is a graph showing the relationship between the amount of W in the hard phase forming powder and the amount of wear and the crushing strength in the Examples of the present invention;

12 is a graph showing the relationship between the amount of MnS powder added, the amount of abrasion, and the rolling strength in the embodiment of the present invention;

13 is a graph showing the relationship between the amount of MnS powder added and the number of processed pores in the embodiment of the present invention;

14 is a graph showing the relationship between the amount of Pb powder added, the amount of abrasion, and the rolling strength in the embodiment of the present invention;

15 is a graph showing a relationship between the amount of Pb powder added and the number of processed pores in the embodiment of the present invention;

16 is a graph showing the relationship between the amount of MgSiO ₃ powder added, the amount of abrasion, and the rolling strength in the embodiment of the present invention;

17 is a graph showing a relationship between the amount of MgSiO ₃ powder added and the number of processed pores in an embodiment of the present invention, and

FIG. 18 is a graph showing the effect of infiltration or impregnation of lead, copper, and acrylic resin on the amount of wear and the number of processed pores in an embodiment of the present invention. FIG.

The first wear-resistant small bond of the present invention relates to the improvement of the wear-resistant small bond which has been proposed by the applicant in Japanese Patent Publication No. 195012/97, and excludes Mo from the components forming the matrix structure, while increasing the content of Ni. Thus, the problem of the present invention has been achieved by setting the ratio of austenite in the known structure within an appropriate range.

That is, the first wear-resistant small binder of the present invention has a total composition consisting of 6.0 to 25.0 wt% of Ni, 0.6 to 8.75 wt% of Cr, 0.54 to 2.24 wt% of C, and the remainder of Fe, and in the mixed structure of martensite and austenite Represents a metallic structure in which a ferrite phase in which Cr is diffused or a hard phase surrounded by a mixed phase of ferrite and austenite in which Cr is diffused is dispersed around a nucleus of Cr carbide, and the austenite in the mixed structure in the metal structure. The area ratio is 5 to 30%.

Hereinafter, with reference to FIG. 1, the effect | action of the wear-resistant small bond alloy of the said structure is demonstrated with reference to numerical limitation.

① Base

1 is a schematic diagram showing a metal structure in the case where the surface of the wear-resistant small-alloy alloy is subjected to corrosion treatment with nital or the like. As shown in Fig. 1, the base of this wear-resistant small binder is a mixed structure of martensite and austenite. Martensite is a structure with high hardness and material strength, which may contribute to an improvement in wear resistance. However, due to the hardness, for example, the wear of the valve serving as the counterpart is promoted. The metal particles resulting from the wear of the counterparts act as abrasive grains, and as a result, promote the wear of the valve seat. Therefore, in the present invention, by dispersing austenite having a high toughness, damage to the counterpart parts is reduced without compromising known wear resistance. According to the inventor's review, if the area ratio of austenite is less than 5%, the amount of martensite is too high to increase the aggression against counterparts. If the area ratio of austenite exceeds 30%, the wear resistance and material strength are increased. It is deteriorated.

Although not shown in FIG. 1, sorbite and bainite may be generated depending on the composition of the composition and the cooling conditions after sintering, and the present invention includes such a configuration. Specifically, the nucleus of the sorbite and / or upper bainite is a structure in which bainite is surrounded and a mixed structure containing bainite having high hardness and high strength close to martensite, whereby hardness is appropriately adjusted to wear resistance. At the same time, it can suppress the aggression against opponent parts. The formation of this martensite or bainite is determined by the diffusion concentration and cooling rate of an element which improves hardenability such as Ni and Cr which will be described later. In other words, the portion rich in these elements (high concentration) is transformed into martensite, and the rich portion is then converted to bainite. In addition, if the cooling rate is high, it converts to martensite and subsequently to bainite. On the other hand, when the element that improves the hardenability is insufficient or the cooling rate is slow, the transformation to sorbite and / or upper bainite.

② hard phase

As shown in Fig. 1, a ferrite phase or a hard phase surrounded by a mixed phase of ferrite and austenite is dispersed around the core made of Cr carbide. The core of Cr carbide is higher in hardness than martensite, further improving wear resistance. Further, the ferrite phase or the mixed phase binds the nucleus of Cr carbide to the base and at the same time has a high Cr concentration, which is high in toughness, and serves as a buffer material to alleviate the impact on the nucleus when the valve is installed, thereby preventing carbides from falling off. In addition, the hard Cr diffuses into the matrix, thereby strengthening the matrix and further improving wear resistance.

Next, the reason for numerical limitation of the said composition of components is demonstrated.

Ni: Ni is employed at the base to strengthen the base, contributes to the improvement of wear resistance, and also promotes martensite by improving the hardenability of the base structure. In addition, while spreading to the matrix and acting to enhance the solid solution of the matrix, the portion having a high Ni concentration remains as soft austenite, thereby improving the toughness of the matrix. If the content of Ni is less than 6.0% by weight, the above effect is insufficient. If the content of Ni is more than 25.0% by weight, the amount of the soft austenite phase increases, thereby reducing the wear resistance. Therefore, content of Ni is limited to 6.0-25.0 weight%.

Cr: Cr is employed in the base to strengthen the base and at the same time improves the hardenability of the base structure, and this action contributes to the improvement of the strength and wear resistance of the base. In addition, Cr forms a hard phase containing Cr carbide as a nucleus to further improve wear resistance. Further, Cr diffused from the hard phase to the base has a function of firmly binding the hard phase to the base and further strengthening the base structure to further improve hardenability. In addition, since the portion of the high Cr concentration around the hard phase forms a ferrite phase or a mixed phase of ferrite and austenite, the effect of relieving the impact at the time of valve installation and the removal of hard components such as Cr carbide from the friction sliding surface are eliminated. It is effective to prevent. If the content of Cr is less than 0.6% by weight, the above effect is insufficient. If the content of Cr is more than 8.75% by weight, the powder is cured to impair compressibility. Therefore, content of Cr is limited to 0.6-8.75 weight%.

C: C acts on strengthening of the matrix and contributes to improvement of wear resistance. In addition, C forms Cr carbide and further contributes to improvement of wear resistance. If the content of C is less than 0.54% by weight, ferrite having low abrasion resistance and low strength remains in the matrix structure, while carbide formation is insufficient and improvement in wear resistance is insufficient. On the other hand, when the content of C exceeds 2.24% by weight, cementite begins to precipitate at grain boundaries, the matrix becomes brittle, the strength decreases, the amount of carbides formed increases, and the wear of the counterpart is promoted, and the powder By this hardening, compressibility falls. Therefore, content of C is limited to 0.54-2.24 weight%.

Next, the second wear resistant small bond of the present invention is added with at least one of Mo, V, and W to the wear resistant small bond of the above constitution, so that the hard core is not only Cr carbide but also one of Mo carbide, V carbide and W carbide. It is characterized by consisting of more than one species.

That is, the second wear-resistant small binder contains 6.0 to 25.0 wt% of Ni, 0.6 to 8.75 wt% of Cr, 0.54 to 2.24 wt% of C, and at the same time, 0.05 to 1.05 wt% of Mo, 0.03 to 0.77 wt% of V, and 0.15 wt.% Of W. Ferrite phase or ferrite phase containing Cr at least one of -1.75% by weight, the remainder having a total composition consisting of Fe, and Cr being diffused around the nucleus mainly made of Cr carbide in a mixed structure of martensite and austenite. A metal structure in which the hard phase surrounded by the mixed phase of austenite diffused by Cr is dispersed is represented, and the area ratio of austenite in the mixed structure in the metal structure is 5 to 30%.

In the wear-resistant small-bonding alloy of the above structure, the hard particles (nuclei) in the hard phase are composed of Mo carbide, V carbide or W carbide, or an intermetallic compound of Cr and Mo, V or W, in addition to Cr carbide. That is, in the schematic diagram of Fig. 1, the metal structure is obtained by replacing the core made of Cr carbide with the core made mainly of Cr carbide. In addition, V and W form fine carbides with C to contribute to the improvement of wear resistance, while the intermetallic compound and the carbide have the effect of preventing coarsening of Cr carbides. Since the coarse Cr carbide promotes wear of the counterpart parts, wear of the valve, which is the counterpart part, is suppressed by preventing coarsening, and wear resistance is also improved. Mo is employed in the base to strengthen the base, and at the same time to improve the hardenability of the base structure, by this action contributes to the improvement of the strength and wear resistance of the base. In addition, V also strengthens the base and contributes to strengthening the base and improving wear resistance. Therefore, the second wear-resistant small binder of the present invention not only has the above excellent characteristics, but also has improved wear resistance.

Here, if the contents of Mo, V, and W are less than 0.05%, 0.03%, and 0.15% by weight, respectively, the above-described effects cannot be expected. On the other hand, when it exceeds 1.05% by weight, 0.77% by weight, and 1.75% by weight, respectively, the powder is cured and the compressibility is impaired, and the amount of precipitated intermetallic compound or carbide is increased to promote the wear of the counterpart. Therefore, in the second wear-resistant small binder, the content of Mo is limited to 0.05 to 1.05% by weight, the content of V to 0.03 to 0.77% by weight, and the content of W to 0.15 to 1.75% by weight. Moreover, according to the inventor's examination, if content of Mo, V, and W is within the said upper limit, it is confirmed that such a problem does not arise even if they are used together.

It is preferable to disperse | distribute 0.1-2.0 weight% of 1 or more types of manganese sulfide, lead, and a magnesium silicate mineral in the metal structure of the said 1st, 2nd wear-resistant small bond alloy. These compounds are machinability improving components, which are dispersed in a matrix, thereby reducing the cutting force during cutting and starting the breaking of the cutting chips, thereby improving the machinability of the small alloy. If the content of these machinability improving components is less than 0.1% by weight, the effect is insufficient. If the content of these machinability improving components exceeds 2.0% by weight, the machinability improving component inhibits the diffusion of powders during sintering, and thus the strength of the small-bonded alloy decreases. do. Therefore, content of the said machinability improvement component is limited to 0.1-2.0 weight%.

Moreover, it is preferable to contain lead, copper, a copper alloy, or an acrylic resin in the pore of the said wear-resistant small bond alloy. These are also components for improving machinability. In particular, when cutting the small-bonded alloy having pores, intermittent cutting is carried out. However, the inclusion of lead, copper, copper alloy or acrylic resin in the pores results in continuous cutting, and the impact on the tool blade is alleviated. do. In addition, lead also functions as a solid lubricant, and copper or copper alloy has a high thermal conductivity, thereby preventing heat from being limited to the inside, thereby reducing damage to the blade due to heat. There is a function to be a starting point for breaking a cutting chip.

Next, the production method of the wear-resistant small binder alloy of the present invention is Cr 4.0-25.0 wt% based on the known component powder having a composition consisting of 0.5 to 1.4 wt% graphite powder, 6.0 to 25.0 wt% Ni, and the remainder of Fe with respect to the whole mixed powder. , C 0.25-2.4% by weight and 15.0-35.0% of a hard phase forming powder having a composition consisting of the remainder of Fe were prepared, and the mixed powder was molded and sintered to form a mixed structure of martensite and austenite. A ferrite phase in which Cr is diffused or a hard phase surrounded by a mixed phase of the ferrite and Cr in which austenite is diffused forms a metal structure in which the nucleus of Cr carbide is dispersed, and austenite in the mixed structure in the metal structure is formed. It is characterized by setting the area ratio of to 5 to 30%.

Hereinafter, the reason for limitation of the ratio of the component of each powder and each component is demonstrated.

(1) matrix type powder

Ni: Ni is an element that enhances mar resistance by improving the hardenability of the matrix structure while enhancing the wear resistance by solidifying the matrix. In addition, a known portion having a high Ni concentration remains as austenite, thereby improving the known toughness.

It is easy to give Ni in the form of a simple powder, but in consideration of the fluidity of the powder, a powder in which Ni is partially diffused into Fe powder or an alloy alloy containing Ni (Fe-Ni alloy powder) alone It is also possible to use or use together. However, if it is added only in the form of Fe-Ni alloy powder, Ni concentration becomes uniform and component segregation does not occur. As a result, no mixed structure of martensite and austenite is formed in the matrix. Therefore, the following five forms of addition of Ni are preferable. In addition, partial diffusion means that Ni powder diffuses and fixes to Fe powder.

① Fe Powder + Ni Powder

② Ni partial diffusion Fe powder

③ Ni partial diffusion Fe powder + Ni powder

④ Fe-Ni alloy powder (pre-alloy powder) + Ni powder

⑤ Powder with Ni partially diffused into Fe-Ni alloy powder

The amount of Ni imparted in such a form cannot be expected as such when the content of Ni in the whole mixed powder is less than 6.0% by weight. On the other hand, when the amount of Ni exceeds 25 wt% with respect to the total weight of the mixed powder, the amount of retained austenite increases, and wear resistance and strength decrease. Therefore, the content of Ni in the matrix type powder is limited to the amount corresponding to 6.0 to 25.0% by weight of Ni in the whole mixed powder.

Graphite: When C is added to Fe powder or Ni powder in solid solution, the powder is cured and the compressibility thereof is lowered. Thus, graphite is added in the form of graphite powder. C added in the form of graphite powder strengthens the matrix and at the same time improves the wear resistance. When the amount of graphite added is less than 0.50% by weight, ferrite having low wear resistance and low strength remains in the matrix structure, and the amount of Cr carbide is insufficient. On the other hand, when it exceeds 1.40 weight%, cementite will begin to precipitate in a grain boundary, a matrix will embrittle and strength will fall. Therefore, the graphite to be added is limited to 0.50 to 1.4O% by weight based on the total weight of the mixed powder.

(2) hard phase forming powder

The hard phase forming powder is Fe-Cr-C alloy powder, and explains the basis of numerical limitation of the composition of components of the hard phase forming powder.

Cr: Cr in the hard phase forming powder forms C and Cr carbides dissolved in this alloy powder, and becomes a hard core, contributing to the improvement of wear resistance. In addition, a part of Cr diffuses into the matrix to improve the hardenability of the matrix to promote martensite formation, while forming a ferrite phase or a mixed phase of ferrite and austenite in a portion of high Cr concentration around the hard phase. This contributes to the effect of alleviating the shock at the time of valve installation. If the content of Cr is less than 4% by weight based on the total weight of the hard phase forming powder, the amount of Cr carbide to be formed is insufficient to contribute to wear resistance. On the other hand, if it exceeds 25% by weight, the amount of carbides to be formed increases, thereby facilitating abrasion of the counterpart parts, increasing the hardness of the powder and impairing compressibility. Moreover, abrasion resistance also falls by increasing the quantity of a ferrite phase or the mixed phase of this ferrite and austenite. As mentioned above, content of Cr in a hard phase formation powder is limited to 4-25 weight%.

C: C in the hard phase forming powder forms Cr and Cr carbide, and becomes a hard core, contributing to the improvement of wear resistance. When the content of C is less than 0.25% by weight relative to the total weight of the hard phase forming powder, the amount of carbides is insufficient and does not contribute to the improvement of wear resistance. When the content of C exceeds 2.4% by weight, the amount of carbides formed increases and the While promoting wear, the hardness of the powder increases and the compressibility decreases. Therefore, content of C in hard phase formation powder is limited to 0.25-2.4 weight%.

(3) Weight ratio of matrix type powder and hard phase forming powder

The hard phase formed by the hard phase forming powder forms a hard nucleus in which the original powder part has hard particles made of Cr carbide, and a mixture of austenite and ferrite having a high Cr concentration around the nucleus is soft. The phase forms the surrounding tissue. As described above, the hard phase has a function of improving wear resistance and preventing a drop in material strength due to the presence of a mixed phase having high toughness. If the amount of the hard phase forming powder is less than 15% by weight based on the total weight of the mixed powder, the amount of the hard phase to be formed is insufficient to contribute to the wear resistance, and when added in excess of 35% by weight, the wear resistance cannot be further improved. When the amount of the ferrite phase having a high Cr concentration, or the mixed phase of austenite and ferrite is increased, defects such as lowering of material strength and lowering of compressibility occur. Therefore, the amount of hard phase forming powder added is limited to 15 to 35% by weight based on the total weight of the mixed powder.

(4) Adjustment of area ratio of austenite

In order to reduce the ratio of austenite in the metal structure and increase the ratio of martensite, it is most simple to increase the cooling rate after sintering. When the content of Ni in the matrix type powder is large, the proportion of retained austenite increases, but in this case, it can be transformed into martensite by subzero treatment described later. Alternatively, by mainly using prealloy powders of Fe and Ni as Ni in the matrix type powder, the diffusion of Ni becomes more uniform and the ratio of austenite is reduced.

The wear-resistant small binder prepared using the mixed powder consisting of the predetermined amount of the known ingredient powder and the hard phase forming powder is Ni 6.0-25.0 wt%, Cr 0.6-8.75 wt%, C 0.54-2.24 wt%, and Fe remaining portion. A metal structure in which a hard phase surrounded by a ferrite phase in which Cr is diffused or a mixed phase of austenite in which ferrite and Cr are dispersed is dispersed in a mixed structure of martensite and austenite in a mixed structure of martensite and austenite. In addition, the area ratio of austenite in the mixed structure in the metal structure is 5 to 30%.

Here, the hard phase forming powder contains Cr 4.0-25.0 wt%, C 0.25-2.4 wt%, and at least one of Mo 0.3-3.0 wt%, V 0.2-2.2 wt%, and W 1.0-5.0 wt%. It is preferable to use the alloy powder of the composition which contains the above and consists of Fe remainder.

The production method of the wear-resistant alloy using the alloy powder as described above is characterized in that at least one of Mo, V, W is added to the matrix-type component of the production method. The wear-resistant small binder prepared using this matrix powder contains 6.0 to 25.0 wt% of Ni, 0.6 to 8.75 wt% of Cr, 0.54 to 2.24 wt% of C, and 0.05 to 1.05 wt% of Mo and V 0.03 to 0.77. Ferrite containing at least one of weight% and W 0.15 to 1.75 weight%, the balance having a total composition consisting of Fe, and Cr diffused around the nuclei mainly made of Cr carbide in a mixed structure of martensite and austenite. A metal structure in which a hard phase surrounded by a phase or a mixed phase of austenitic ferrite and Cr diffused is dispersed, and the area ratio of austenite in the mixed structure in the metal structure is 5 to 30%.

Powder of lead, manganese sulfide, boron nitride, and magnesium silicate mineral

In order to improve the machinability of the wear-resistant small binder alloy of the present invention, in the mixed powder, at least one of lead powder, manganese sulfide powder, boron nitride powder, and magnesium metasilicate mineral powder is 0.1 to 2.0% by weight based on the whole powder. % Can be added. In addition, the basis of numerical limitation of this addition amount is as having mentioned above.

Content of lead, copper, copper alloy, or acrylic resin

Lead, copper, copper alloy or acrylic resin can be infiltrated or impregnated in the pores of the wear resistant small binder alloy of the present invention. Specifically, lead, copper or copper alloy powder is added to the mixed powder to sinter the molded body of the powder so that these metals can be infiltrated or impregnated in the pores. Alternatively, the acrylic resin can be filled (impregnated) into the pores by filling the sealed acrylic resin with the wear-resistant small binder and depressurizing the inside of the sealed container. In addition, these metals can be impregnated into the pores by using molten lead or copper or a copper alloy instead of an acrylic resin.

Deep cooling

By deep-cooling the wear-resistant small binder of the present invention, part of the austenite remaining at room temperature is transformed into high strength martensite, whereby the strength and wear resistance can be further improved. However, when impregnating the acrylic resin described above, in order to prevent the impregnated resin from deteriorating by deep cooling, it is necessary to perform deep cooling before impregnating the resin.

(Example)

Hereinafter, embodiments of the present invention will be described.

[First Embodiment]

As the matrix powder, Ni partial diffusion Fe powder shown in Table 1, Fe-Ni alloy powder (prealloy powder) shown in Table 2, single Ni powder, single Fe powder and graphite powder were prepared. In addition, an alloy powder shown in Table 3 is prepared as a hard phase forming powder.

These powders are mixed at the compounding ratios shown in Tables 4 and 5 to prepare mixed powders (alloys Nos. 1 to 76). These mixed powders were molded into a cylindrical shape having an outer diameter of 50 mm, an inner diameter of 45 mm and a height of 10 mm at a molding pressure of 6.5 ton / cm 2, and sintered at 1180 ° C. for 60 minutes in an ammonia decomposition gas atmosphere, and the components shown in Tables 6 and 7 An alloy (alloy numbers 1 to 76) having a composition is obtained. Further, a deep cooling treatment in which most alloys are immersed in liquid nitrogen is performed. Immersion time (minutes) is shown in Table 4 and Table 5.

The surface of the alloy was corroded with nital, and the area ratio of austenite in the metal structure was measured from the micrographs thereof, and is shown in Tables 6 and 7.

The alloy is subjected to measurement of the rolling strength and a simple abrasion test, and the results are shown in Tables 8 and 9 and FIGS. 2 to 11. In addition, the simple abrasion test presses and fits a small alloy processed into a valve seat shape into an aluminum alloy housing, and moves the valve up and down by rotating the eccentric cam by a motor drive, thereby causing the valve face and the seat face of the valve seat. This test is repeated collision. In addition, the temperature setting in this test was made into the test which simulates the use environment in an engine room simply by heating the bevel of a valve with a burner. In this test, the number of rotations of the eccentric cam is set to 2700 rpm, the test temperature of the valve seat portion is set to 250 ° C., and the repetition time is set to 15 hours.

(1) Influence of Ni amount

FIG. 2 is a graph comparing the relationship between the wear amount and the strength of each alloy having different amounts of Ni (alloys 1 to 7), and FIG. 3 shows the relationship between the Ni content of the respective alloys and the amount of austenite (area%). The graph shown. Alloys 1 to 7 were subjected to deep cooling for 10 minutes. As shown in FIG. 3, the amount of austenite changes almost linearly with respect to the Ni content, and the amount of austenite is increased by setting the Ni content to 6 to 25% by weight. It was confirmed that it became 5 to 30% of range.

As is apparent from Fig. 2, as the amount of Ni increases, the amount of martensite increases with austenite, so that the wear resistance and strength of the valve seat increase as the amount of Ni increases. The effect of the decrease in the known strength due to the increase of austenite is greater than the effect of improving the strength and the wear resistance due to the increase of, and the wear resistance and the strength of the valve seat are lowered.

In alloy 1 having an amount of Ni of less than 6% by weight, the amount of martensite is insufficient, so that the amount of wear of the valve seat VS is large, and the rolling strength is low. In addition, in the alloy 7 in which the Ni amount is more than 25% by weight, as is apparent from FIG. 3, as the amount of soft austenite is excessively increased, the strength decreases and the amount of wear of the valve seat is significantly increased. In contrast, in the alloys 2 to 6 in which the amount of Ni is in the range of 6 to 25% by weight defined in the present invention and the amount of austenite is in the range of 5 to 30% by weight specified in the present invention, the amount of wear of the valve seat and the valve is reduced. There is little, and the ring strength is maintained in a sufficient range.

(2) the effect of austenite content

FIG. 4 is a graph comparing the amount of wear of each alloy in which two austenitic components are adjusted so that only the austenite content is different by varying the liquid nitrogen soaking time during the deep cooling treatment in the same composition. As can be seen from Fig. 4, in alloy 19 having an austenite content of less than 5% by weight, the aggressiveness against the valve, which is a counterpart, is high, and thus, the wear amount of the valve V is increased, and the wear powder becomes abrasive grain. It acts as an increase in the amount of wear of the valve seat VS. In addition, in alloys 23 and 24 in which the amount of austenite exceeds 30% by weight, the amount of soft austenite increases, so that the amount of wear of the valve seat increases considerably, and the valve also increases wear due to the adhesion of austenite. On the other hand, in the alloys 6, 16, and 21, the amount of austenite is in the range of 5 to 30% by weight, so the amount of wear is small and excellent wear resistance is shown. In addition, since alloy 22 has an austenite content of about 30.4% and is almost the upper limit, wear resistance is sufficient.

(3) Influence of Graphite Powder Addition

5 is a graph comparing the amount of wear of each alloy having a different amount of graphite powder added. As can be seen from FIG. 5, since C of the graphite strengthens the matrix and forms carbide at the same time, the wear resistance of the valve seat increases with the increase in the amount of addition thereof, but the abrasion resistance against the counterpart increases, and the valve wear amount increases. do. In addition, when a certain value is exceeded, precipitation of cementite increases, the matrix becomes brittle, the wear resistance and the strength decrease, and the wear powder of the valve acts as abrasive particles, thereby promoting wear of the valve seat. In alloy 25 having an graphite powder content of less than 0.5% by weight, the solid solution strengthening and formation of a hard phase are insufficient, so that the amount of wear of the valve seat VS is large, and the rolling strength is low. Further, in the alloy 30 in which the amount of graphite powder added exceeds 1.4 wt%, cementite precipitates, resulting in an increase in the wear amount of the valve seat and the valve, and also low rolling strength. On the other hand, in the alloys 26 to 29, in which the graphite addition amount is in the range of 0.5 to 1.4% by weight in the present invention, the wear amount of the valve seat and the valve is small, and the ring strength is maintained in a sufficient range.

(4) Effect of the amount of hard phase forming powder added

6 is a graph comparing the amount of wear of each alloy having different amounts of hard phase forming powder. As can be seen from Fig. 6, as the amount of hard phase forming powder is increased, the amount of the mixed phase of soft ferrite and austenite increases, and at the same time, the powder hardens and the compressibility decreases, so that the density of the alloy decreases. , The strength of the alloy gradually decreases. In addition, when too many soft mixed phases show that wear resistance of a valve seat falls, it turns out from FIG. In alloy 31 in which the amount of hard phase-forming powder added is less than 15% by weight, since the hard phase is insufficient, the amount of wear of the valve seat VS increases. In addition, in the alloy 35 in which the amount of hard phase forming powder is more than 35% by weight, the valve wears due to the increase in aggressiveness to the valve due to the increase in hard phase, and at the same time, the wear powder acts as abrasive particles and soft mixing. As the phase increases and the known strength decreases, the amount of wear of the valve seat increases. On the other hand, in alloys 32 to 34 in the amount of hard phase forming powder added in the range of 15 to 35% by weight specified in the present invention, the ring strength is maintained in a sufficient range, and the amount of wear of the valve seat and the valve is reduced.

(5) Effect of Cr content in hard phase forming powder

7 is a graph comparing the amount of wear of each alloy having different Cr amounts in the hard phase forming powder. As can be seen from FIG. 7, as the amount of Cr in the hard phase forming powder increases, the hardness of the powder increases and the compressibility decreases, so that the rolling strength of the alloy gradually decreases. In addition, when the Cr amount is too large, it can be seen from FIG. 7 that the amount of Cr carbide is increased to promote the wear of the valve, thereby promoting the wear of the valve seat. In alloy 36 in which the amount of Cr in the hard phase forming powder is less than 4% by weight, the formation of Cr carbide is insufficient, so that the amount of wear of the valve seat VS increases. In addition, in alloy 42 having an amount of Cr exceeding 25% by weight, at the same time as the decrease in the known strength due to the decrease in compressibility of the powder, the increase in valve wear due to the increase in valve aggressiveness and increase in valve seat wear due to the valve wear powder, The amount of wear on the valve increases. On the other hand, in alloys 37 to 41 where the Cr amount is in the range of 4 to 25% by weight specified in the present invention, the wear amount of the valve seat and the valve is small, and the rolling strength is maintained in a sufficient range.

(6) Effect of C content in hard phase forming powder

8 is a graph comparing the amount of wear of each alloy having a different amount of C in the hard phase forming powder. As can be seen from Fig. 8, as the amount of C in the hard phase forming powder increases, the hardness of the powder increases and the compressibility decreases, so that the rolling strength of the alloy gradually decreases. In addition, when the amount of C is too large, it can be seen from FIG. 8 that the wear of the valve is promoted by the increase of carbides, thereby promoting the wear of the valve seat. In the alloy 43 in which the amount of C in the hard phase forming powder is less than 0.25% by weight, the generation of carbides is insufficient, so that the amount of wear of the valve seat VS increases. In addition, in the alloy 49 where the amount of C exceeds 2.4% by weight, the compressibility of the powder is lowered, so that the rolling strength is low, and the wear amount of the valve seat is increased due to the decrease in the known strength and the wear of the valve. In contrast, in alloys 44 to 48 having a C content in the range of 0.25 to 2.4% by weight in the present invention, the amount of wear of the valve seat and the valve is small, and the ring strength is maintained in a sufficient range.

(7) Effect of Mo content in hard phase forming powder

9 is a graph comparing the relationship between the wear amount and the rolling strength of each alloy having different Mo amounts in the hard phase forming powder. As can be seen from Fig. 9, as the amount of Mo in the hard phase forming powder increases, the hardness of the powder increases and the compressibility decreases, so that the rolling strength of the alloy gradually decreases. It is also understood from FIG. 9 that if the amount of Mo is too large, the wear of the valve is promoted by the increase of carbide, thereby promoting the wear of the valve seat. In alloys 51 to 57, in which the Mo content is in the range of 0.3 to 3% by weight in the present invention, the wear amount of the valve seat and the valve is stabilized to a fairly low value, and the rolling strength is also maintained in a sufficient range. On the other hand, in the alloy 39 in which the amount of Mo in the hard phase forming powder is less than 0.3% by weight, the generation of carbides is not suitable, so that the amount of wear of the valve seat VS is relatively large. In addition, in alloy 58 in which the Mo content exceeds 3% by weight, the compressive strength is low due to the decrease in compressibility of the powder, and the amount of wear of the valve seat also increases due to the decrease in the known strength and the wear of the valve.

(8) Effect of V content in hard phase forming powder

FIG. 10 is a graph comparing the relationship between the wear amount and the rolling strength of each alloy having different amounts of V in the hard phase forming powder. FIG. As can be seen from Fig. 10, as the amount of V in the hard phase forming powder increases, the hardness of the powder increases and the compressibility decreases, so that the rolling strength of the alloy gradually decreases. Also, it can be seen from FIG. 10 that when the amount of V is excessively large, the wear of the valve is promoted by the increase of carbides, thereby promoting the wear of the valve seat. In alloys 59 to 65 in which the amount of V is in the range of 0.2 to 2.2% by weight specified in the present invention, the amount of wear of the valve seat and the valve is stabilized to a fairly low value, and the rolling strength is maintained in a sufficient range. In contrast, in the alloy 39 where the amount of V in the hard phase forming powder is less than 0.2% by weight, the generation of carbide is not suitable, so the amount of wear of the valve seat VS is relatively large. Further, in alloy 66 in which the amount of V exceeds 2.2% by weight, the compressive strength is low due to the decrease in compressibility of the powder, and the amount of wear of the valve seat also increases due to the decrease in the known strength and the wear of the valve.

(9) Effect of W content in hard phase forming powder

FIG. 11 is a graph comparing the relationship between the wear amount and the rolling strength of each alloy having different amounts of W in the hard phase forming powder. FIG. As can be seen from Fig. 11, as the amount of W in the hard phase forming powder increases, the hardness of the powder increases and the compressibility decreases, so that the rolling strength of the alloy gradually decreases. In addition, when the amount of W is too large, it can be seen from FIG. 11 that the wear of the valve is promoted by the increase of carbide, thereby promoting the wear of the valve seat. In alloys 68 to 72, in which the amount of W is in the range of 1 to 5% by weight in the present invention, the amount of wear of the valve seat and the valve is quite low, and the rolling strength is maintained in an appropriate range. On the other hand, in the alloy 73 in which the amount of W in the hard phase forming powder exceeds 5% by weight, the compressive strength is low due to the decrease in compressibility of the powder, and also the amount of wear of the valve seat is large due to the decrease in the known strength and the wear of the valve. Lose.

(10) Effect of Containing Multiple Components such as Mo in Hard Phase Forming Powder

Alloy 76 contains 3 wt% Mo, 2.2 wt% V, and 5 wt% W in the hard phase forming powder, which is the upper limit of the numerical limitation of the present invention. Therefore, the influence on the amount of wear and the compressive strength is examined. According to Table 9, the rolling strength of alloy 76 is 947 MPa, the valve seat wear amount is 31 micrometers, and the valve wear amount is 18 micrometers. From this, even if it contains many types of Mo, V, and W, although slight fall was seen in the rolling strength, it turned out that it is advantageous in abrasion resistance.

Second Embodiment

(1) sample preparation

As the powder for matrix formation, a single Ni powder, a single Fe powder and a graphite powder, and an alloy powder shown in Table 3 as a hard phase forming powder were prepared, and these powders, manganese sulfide powder, lead powder, and magnesium metasilicate mineral powder were prepared. As an example, any one of the MgSiO ₃ powders was mixed at the compounding ratio shown in Table 10, and the mixtures were sintered and sintered under the same conditions as those in the first embodiment to prepare alloys 77 to 101 having the composition shown in Table 11. Lead, copper or acrylic resin was infiltrated or impregnated into the pores of the alloys 96-101. In addition, all the alloys are subjected to the deep cooling treatment of immersion in liquid nitrogen, and the immersion time (minutes) is written in Table 10 together.

(2) evaluation of strength and machinability

The alloy was subjected to measurement of rolling strength, simple abrasion test and machinability test. The results are shown in Table 12 and FIGS. 12 to 15. In addition, the machinability test uses a bench drill to drill a sample with a constant load and compares the number of possible machining. In this test, the load is 1.0 kg and the drill used is a cemented carbide drill. It carried out by setting the thickness of the sample to 3 mm.

(3) Effect of Manganese Sulfide Powder Addition

12 is a graph comparing the relationship between the wear amount of each alloy with the addition amount of the manganese sulfide powder as the machinability improving component and the rolling strength, and FIG. 13 is a graph comparing the number of processed pores. As can be seen from Fig. 13, with the increase in the amount of manganese sulfide powder added, the machinability is improved by the effect of the manganese sulfide particles dispersed in the matrix, but according to Fig. 12, the diffusion of powders between the manganese sulfide powders during sintering is improved. Since it suppresses, a known strength falls and it turns out that a rolling strength falls. In addition, as can be seen from FIG. 12, the valve seat wear amount tends to increase slightly up to 2.0% by weight of manganese sulfide powder, but at a low value, it shows good wear resistance, but exceeds 2.0% by weight. The amount of wear increases due to the influence of the decrease. From this, when the addition amount of manganese sulfide powder was 2.0 weight% or less, it turned out that machinability can be improved in the range which does not impair strength and abrasion resistance.

(4) Effect of Lead Powder Addition

Next, FIG. 14 is a graph comparing the relationship between the wear amount and the rolling strength of each alloy in which the addition amount of the lead powder as the machinability improving component is different, and FIG. 15 is a graph comparing the number of processed pores. 15, it turns out that machinability improves with the increase of the addition amount of lead powder. As can be seen from Fig. 14, when the amount of lead powder added is less than 2.0% by weight, it becomes a metal structure in which fine lead phase is dispersed in the matrix, and exhibits a good characteristic value almost the same as in the case of no addition with strength and wear resistance. However, when the addition amount of lead powder exceeds 2.0 weight%, it shows the tendency for abrasion resistance to fall. The reason is considered as follows. In other words, when the lead powder is added in excess of 2.0% by weight, the lead powder aggregates to form coarse lead in the matrix. The coarse lead phase in this matrix causes the force to press and expand the matrix due to the expansion of lead under high temperature, and as a result, the strength of the matrix is considered to decrease. However, this tendency is not remarkable in the pressure test at room temperature. From this, it can be seen that by adding the lead powder at 2.0 wt% or less, the machinability can be improved without compromising the strength and the wear resistance.

(5) Effect of MgSiO ₃ Powder Addition

Next, FIG. 16 is a graph comparing the relationship between the wear amount of each alloy having a machinability improving component MgSiO ₃ powder and the rolling strength, and FIG. 17 is a graph comparing the number of processed pores. It can be seen from FIG. 17 that the machinability is improved by the effect of MgSiO ₃ particles dispersed in a matrix as the amount of MgSiO ₃ powder added increases. In addition, as can be understood from FIG. 16, it is understood that the increase in the added amount of the MgSiO ₃ powder inhibits the diffusion of the powders during sintering, so that the rolling strength is lowered because the known strength is lowered. As can be understood from FIG. 16, the valve seat wear amount tends to increase slightly when the amount of MgSiO ₃ powder added is less than 2.0% by weight, but a low value shows good wear resistance, but exceeds 2.0% by weight. The amount of wear increases by the influence. From this, it can be seen that by adding the MgSiO ₃ powder at 2.0 wt% or less, the machinability can be improved in a range that does not impair strength and wear resistance.

(6) Effect of infiltration such as lead

Next, FIG. 18 is a graph comparing the relationship between the wear amount of the alloy infiltrated or impregnated with lead and the like, and the number of processing pores. In addition, for comparison, the amount of wear and the number of pores of alloy 3 which have not been infiltrated or the like are written together. As can be seen from Fig. 18, by infiltrating or impregnating lead, copper, and acrylic resin, the wear resistance is equal to or higher than that in the case of infiltration or impregnation, and the machinability can be significantly improved while maintaining good wear resistance.

Further, the wear-resistant small alloy of the present invention is not limited to the valve seat as in the above embodiment, but can be applied to all parts requiring wear resistance.

As described above, in the wear-resistant small-kneading alloy of the present invention and the method for producing the same, high wear resistance can be imparted as the small-kneading alloy for valve seat of the internal combustion engine as compared with the conventional art. In addition, by adding manganese sulfide powder, lead powder, boron nitride powder or magnesium metasilicate mineral powder, or by infiltrating or impregnating lead, copper, copper alloy or acrylic resin, the machinability can be improved while maintaining good wear resistance. have.

Claims (20)

It has a total composition consisting of 6.0 to 25.0 wt% of Ni, 0.6 to 8.75 wt% of Cr, 0.54 to 2.24 wt% of C, and the remainder of Fe, and Cr diffuses around the core of Cr carbide in the mixed structure of martensite and austenite. A ferrite phase or a hard phase surrounded by a mixed phase of austenite in which ferrite and Cr are dispersed is dispersed, and the area ratio of austenite in the mixed structure in the metal structure is 5 to 30%. Wear-resistant small bonds made. Containing 6.0 to 25.0 wt% Ni, 0.6 to 8.75 wt% Cr, 0.54 to 2.24 wt% C, and at least one of 0.05 to 1.05 wt% Mo, 0.03 to 0.77 wt% Mo, and 0.15 to 1.75 wt% W And a remainder having a total composition consisting of Fe, and in a mixed structure of martensite and austenite, a ferrite phase in which Cr diffused mainly around Cr nuclei or a mixture of austenite in which ferrite and Cr diffused The wear-resistant small bond alloy which shows the metal structure which the hard phase which a phase surrounds disperse | distributes, and the area ratio of austenite in the mixed structure in the said metal structure is 5 to 30%. In a mixed structure consisting of martensite and austenite, bainite and sorbite, having a total composition consisting of 6.0 to 25.0 wt% Ni, 0.6 to 8.75 wt% Cr, 0.54 to 2.24 wt% C, and Fe residues. Represents a metallic structure in which a ferrite phase in which Cr is diffused or a hard phase surrounded by a mixed phase of the ferrite and austenite in which Cr is diffused is dispersed around the nucleus of Cr carbide, and the austenite in the mixed structure in the metal structure. Abrasion resistant small bonds, characterized in that the area ratio of 5 to 30%. Containing 6.0 to 25.0 wt% Ni, 0.6 to 8.75 wt% Cr, 0.54 to 2.24 wt% C, and at least one of 0.05 to 1.05 wt% Mo, 0.03 to 0.77 wt% Mo, and 0.15 to 1.75 wt% W A ferrite phase in which Cr is diffused around a nucleus composed mainly of Cr carbide in a mixed structure composed of one or more of martensite, austenite, bainite and sorbite; The hard structure surrounded by the hard phase surrounded by the mixed phase of the austenitic ferrite and Cr diffused austenite is dispersed, and the area ratio of the austenite in the mixed structure in the metal structure is 5 to 30%. . 5. The method according to any one of claims 1 to 4, wherein at least one of lead, manganese sulfide, boron nitride, and magnesium metasilicate mineral is dispersed in the metal structure at 0.1 to 2.0 wt%. Abrasion resistant small bonds. The wear-resistant small binder according to any one of claims 1 to 4, wherein the pores of the small binder are filled with lead, copper or a copper alloy, or an acrylic resin. Cr-based component powder composed of 0.5-1.4 wt% of graphite powder, 6.0-25.0 wt% of Ni, and Fe residue, based on the whole mixed powder, Cr 4.0-25.0 wt%, C 0.25-2.4 wt%, and Fe residue Preparing a mixed powder comprising 15.0 to 35.0% of a hard phase forming powder having a negative composition, forming and sintering the mixed powder, and surrounding the nucleus of Cr carbide in the mixed structure of martensite and austenite. Forming a metal structure in which a ferrite phase in which Cr is diffused or a hard phase surrounded by a mixed phase of ferrite and Cr in which austenite is dispersed is dispersed, and the area ratio of austenite in the mixed structure in the metal structure A method for producing a wear-resistant small bond alloy, characterized in that 5 to 30%. Cr-based component powder composed of 0.5-1.4 wt% of graphite powder, 6.0-25.0 wt% of Ni, and Fe residue, based on the whole mixed powder, Cr 4.0-25.0 wt%, C 0.25-2.4 wt%, and Fe residue Preparing a mixed powder comprising 15.0 to 35.0% of a hard phase forming powder having a negative composition; forming and sintering the mixed powder; and at least one of martensite, austenite, bainite, and sorbite. And forming a metal structure in which a hard phase surrounded by Cr diffused ferrite phase or a mixed phase of ferrite and austenite diffused Cr is dispersed around the nucleus of Cr carbide in the mixed structure. The area ratio of the austenite in the mixed structure in the above is 5 to 30%. 8. The method of claim 7, wherein the hard phase forming powder contains 4.0 to 25.0 wt% of Cr, 0.25 to 2.0 wt% of C, and 0.3 to 3.0 wt% of Mo, 0.2 to 2.2 wt% of V, and 1.0 to 5.0 wt of W. A method for producing a wear-resistant small binder containing at least one of% and an alloy powder having a composition consisting of Fe remaining portions. The mixed powder according to any one of claims 7 to 9, wherein at least one of lead powder, manganese sulfide powder, boron nitride powder, and magnesium metasilicate mineral powder is 0.1 to 2.0 based on the whole mixed powder. A method for producing a wear-resistant small bond alloy, characterized in that added by weight%. 10. Preparation of wear-resistant small bonds characterized by infiltration or impregnation of lead, copper, copper alloys or acrylic resins in the pores of the wear-resistant small bonds prepared using the mixed powder according to any one of claims 7 to 9. Way. A process for producing a wear-resistant small bond alloy, which is further subjected to deep cooling treatment of the wear-resistant small bond alloy produced by the production method according to any one of claims 7 to 9. The wear resistant small binder according to claim 5, wherein the pores of the small binder are filled with lead, copper or a copper alloy, or an acrylic resin. 9. The method according to claim 8, wherein the hard phase forming powder contains 4.0 to 25.0% by weight of Cr, 0.25 to 2.0% by weight of C, while 0.3 to 3.0% by weight of Mo, 0.2 to 2.2% by weight and 1.0 to 5.0% by weight of W. A method for producing a wear-resistant small binder containing at least one of% and an alloy powder having a composition consisting of Fe remaining portions. 15. The method of claim 14, wherein at least one of lead powder, manganese sulfide powder, boron nitride powder, and magnesium metasilicate mineral powder is added to the mixed powder in an amount of 0.1 to 2.0 wt% based on the whole of the mixed powder. Method for producing a wear-resistant small binder to be. A method for producing a wear resistant small bond alloy, wherein the lead, copper, copper alloy or acrylic resin is infiltrated or impregnated in the pores of the wear resistant small bond alloy produced using the mixed powder according to claim 10. A method for producing a wear resistant small bond alloy, wherein the lead, copper, copper alloy or acrylic resin is infiltrated or impregnated in the pores of the wear resistant small bond alloy produced using the mixed powder according to claim 14. The method for producing a wear resistant small bond alloy is further subjected to deep cooling treatment of the wear resistant small bond alloy produced by the production method according to claim 10. The method for producing a wear-resistant small bond alloy is further subjected to deep cooling treatment of the wear-resistant small bond alloy produced by the production method according to claim 11. The method for producing a wear-resistant small bond alloy is further subjected to deep cooling treatment of the wear-resistant small bond alloy produced by the production method according to claim 14.