KR20080058316A - Iron-based sintered alloy valve seat material for an internal combustion engine - Google Patents

Abstract

A valve seat material made of iron-based sintered alloy for an internal combustion engine is provided to disperse hard particles on a matrix phase of the alloy to increase abrasion resistance and aggressiveness to the opposite material of the matrix phase of the alloy. A valve seat material made of iron-based sintered alloy for an internal combustion engine disperses hard particles on a matrix phase of the alloy. The matrix phase includes C:0.3~1.5%, one or more elements selected from among Ni, Co, Mo, Cr and V, in a total amount of 1~20%, and the remainder Fe and other unavoidable impurities. The hard particles contain Si:1~15%, Mo:20~60%, 10~70% of one or more elements selected from among Cr, Ni, Co and Fe, and the balance unavoidable impurities, and have a hardness of 500HV0.1~1,200HV0.1, a density of 6.7 g/cm^3 or higher and a radial compression strength of 350 MPa or higher.

Description

IRON-BASED SINTERED ALLOY VALVE SEAT MATERIAL FOR AN INTERNAL COMBUSTION ENGINE}

TECHNICAL FIELD The present invention relates to a valve seat member for an internal combustion engine, and more particularly, to a valve seat member made of an iron-based sintered alloy having further improved strength and abrasion resistance, low relative attack resistance, and suitable for use in a gas fuel engine.

In internal combustion engines (engines) that use liquid fuels such as gasoline and diesel, the lubricity of the valve and the valve seat is maintained by the fuel and the combustion products, so that wear of the valve seat is suppressed to some extent. However, in engines using gaseous fuels such as LPG and CNG (Compressed Natural Gas), there are less combustion products and the metal contact between the valves and the valve seats tends to be smaller than in the case of using liquid fuels. Abrasion of the valve seat tends to increase. In such a situation, further improvement of the wear resistance of the valve seat has been desired for the gas fuel engine.

As a means for improving the wear resistance of the valve seat, a method of dispersing a large amount of Fe-W-based hard particles, Fe-Mo-based hard particles, carbide-based hard particles, and the like in the matrix of the valve seat has been conventionally used. However, when the amount of dispersion of these hard particles is increased, there is a problem that the relative aggressiveness increases and the wear of the valve increases.

For such a problem, for example, Patent Document 1 discloses at least 1 selected from the group consisting of C: 0.5 to 1.5% by weight, Cr and / or V: 0.5 to 10.0% by weight, or Ni, Co, and Mo as known components. Element of species: A valve seat for an internal combustion engine is proposed which contains at least 2.0 to 20.0% by weight in total and the balance Fe and at least 26 to 50% by weight of cobalt-based hard particles. The valve seat manufactured by the technique of patent document 1 can be used suitably for gas fuel engines of the severe use conditions which are easy to produce intermetallic contact wear.

In addition, Patent Literature 2 discloses a high-speed tool steel and an intermetallic compound having a total amount of C, Si, Cr, Ni, Mo, W, Co, and V, and containing a balance of Fe, wherein metal carbides are dispersed. A valve seat material for an internal combustion engine having a structure in which a dispersed cobalt alloy hard phase, an iron alloy phase containing Co-Ni-Mo-C and a cobalt alloy hard phase diffused in the other phases is mixed in a stained form has been proposed. have. According to the technique of patent document 2, the high temperature wear resistance of a valve seat material improves and the lifetime of the valve seat for LPG internal combustion engines can be aimed at.

In addition, Patent Document 3, the total composition contains a predetermined amount of Co, Mo, Cr, V, Si, C, Ni and the balance Fe, bainite (bainite) or bainite and sorbite (sorbite), And a valve seat for a high load engine having a metal structure in which a hard phase composed of Mo silicide in a mixed structure of martensite and austenite is dispersed as a nucleus. have. According to the technique of patent document 3, abrasion resistance improves and it becomes suitable as a valve seat material for high load engines, such as a CNG engine.

[Patent Document 1] Japanese Patent Laid-Open No. 1999-12697

[Patent Document 2] Japanese Patent No. 2706561

[Patent Document 3] Japanese Unexamined Patent Publication No. 2002-285293

In recent gas fuel engines, the engine performance has been further improved, and the use environment of the valve seat has become more severe. For this reason, the improvement of the strength and abrasion resistance of the valve seat used is calculated | required further. However, the valve seat manufactured in the above-described prior art has a problem in that it is impossible to secure a property that can sufficiently satisfy such a demand.

The present invention advantageously solves these problems of the prior art, and has a sufficient strength even in a harsh use environment for a gas fuel engine, and can further maintain excellent wear resistance. The purpose is to provide.

MEANS TO SOLVE THE PROBLEM In order to achieve the subject mentioned above, this inventor earnestly examined the various factors which affect abrasion resistance. As a result, it is important to disperse a large amount of hard particles with low relative aggressiveness in the known phase in order to improve the strength and wear resistance under harsh use environments such as in a gas fuel engine, so that a large amount of hard particles can be stably dispersed in the matrix. In order to find out, it was necessary to set it as the material which has a density of 6.7 g / cm <3> or more and a rolling strength of 350 Mpa or more. As a result, it has been found that the hard particles can be prevented from escaping from the matrix and that high strength and excellent wear resistance can be ensured over a long period of time in a harsh use environment. This invention is completed further by examining further based on the knowledge mentioned above.

That is, the gist of the present invention is as follows.

(1) A valve seat made of an iron-based sintered alloy for an internal combustion engine in which hard particles are dispersed in a matrix of an iron-based sintered alloy, wherein the matrix is 0.3% to 1.5% by mass% and Ni, Co, Mo, Cr, V An intermetallic compound containing 1 to 20% of a total of 1 or 2 or more selected from among them, and having a known composition composed of residual Fe and unavoidable impurities, and containing Fe, Mo, and Si as main components; Hard particles containing one or two or more of an intermetallic compound having Mo and Si as main components, and an intermetallic compound having Ni, Mo and Si as main components, and having a hardness of 500 HV 0.1 to 1200 HV 0.1 in Vickers hardness. Containing 10 to 60% by mass, having a density of at least 6.7 g / cm 3 and a compressive strength of at least 350 MPa, wherein the valve seat made of an iron-based sintered alloy for an internal combustion engine.

(2) In the above (1), the known phase is 1% or 2 or more selected from C, 0.3 to 1.5% by mass, Ni, Co, and Mo, or further 1 or 2 selected from Cr and V in total. A valve seat material made of an iron-based sintered alloy for an internal combustion engine, comprising-20%.

(3) In (1) or (2), the hard particles include an intermetallic compound having Fe, Mo, and Si as a main component, an intermetallic compound having Co, Mo, and Si as a main component, and an intermetallic compound having Ni, Mo, and Si as main components. It is a hard particle containing 1 type (s) or 2 or more types, It contains 1 to 15% of Si, and 20 to 60% of Mo by mass%, and 1 type (s) or 2 or more types chosen from Cr, Ni, Co, and Fe. An iron-based sintered alloy valve seat material for an internal combustion engine, comprising 10 to 70% and having a composition composed of residual unavoidable impurities.

(4) In (3), the hard particles contain 1% by mass of Si: 1% to 15%, 20% to 60% of Mo, or 25% or less of Cr, and / or 10% to 40% of Co. The balance contains Fe-based hard particles having a composition composed of Fe and unavoidable impurities, by mass% by weight of Si: 1 to 15%, Mo: 20 to 60%, or Cr: 5 to 25%. Co-based hard particles having a composition composed of Co and unavoidable impurities, and containing 1% to 15% of Si, 20% to 60% of Mo, and 5% to 25% of Cr and / or 10% to Co or less in mass%. The iron-containing sintered alloy valve seat member for an internal combustion engine, further comprising: and the balance is any one of Ni-based hard particles having a composition composed of Ni and unavoidable impurities.

(5) The valve seat member made of iron-based sintered alloy for an internal combustion engine according to any one of (1) to (4), wherein the solid lubricant contains 0.2 to 5% by mass.

(6) The valve seat made of an iron-based sintered alloy for an internal combustion engine, according to any one of (1) to (5), which is produced through a process of repeating compression molding-sintering twice or a process of performing forging molding-sintering. .

According to the present invention, even in the harsh use environment as in the engine for gas fuel, it is possible to easily and stably produce a valve seat capable of ensuring excellent wear resistance and excellent wear resistance, and exhibits particular effects in the industry. .

The valve seat member of the present invention is a valve seat member made of an iron-based sintered alloy for an internal combustion engine formed by dispersing hard particles in a known phase of an iron-based sintered alloy. Hereinafter, the mass% with respect to the composition is described only in%.

In the valve seat member of the present invention, the matrix phase contains C: 0.3 to 1.5% and 1 to 20% of one or two or more selected from Ni, Co, Mo, Cr, and V, and the balance Fe and inevitable. It has a known composition consisting of red impurities.

First, the reason for limiting composition on a known phase is demonstrated.

C: 0.3 to 1.5%

C is added to promote diffusion at the time of sintering, but is an element which is dissolved in a matrix to increase the strength of the matrix phase. In order to obtain such an effect, 0.3% or more of C is required. On the other hand, when it contains exceeding 1.5%, cementite will become easy to produce | generate in a matrix, a liquid state will generate | occur | produce easily at the time of sintering, stability of matrix structure will fall, and dimensional change of a product will become large. For this reason, in this invention, the known C content was limited to 0.3 to 1.5% of range.

1 type, or 2 or more types selected from Ni, Co, Mo, Cr, and V: 1 to 20% in total

Ni, Co, Mo, Cr, and V are all elements which improve a known wear resistance, and this invention requires 1% or more of total content. On the other hand, even if it contains more than 20% in total, the effect is saturated, so that a moderate effect on the content cannot be expected, which is economically disadvantageous. In addition, Ni, Co, and Mo are more effective in improving the high temperature strength and toughness than Cr and V, and preferably contain one or two or more selected from Ni, Co, and Mo. Therefore, one or two or more selected from Ni, Co, Mo, Cr and V, preferably one or two or more selected from Ni, Co and Mo, or one or two more selected from Cr and V It is preferable to limit the species to 1-20% in total.

Remainder other than the above-mentioned component in a matrix phase consists of Fe and an unavoidable impurity.

The valve seat member of the present invention is composed of an iron-based sintered alloy obtained by dispersing 10 to 60% by mass% of hard particles having a hardness of 500 HV 0.1 to 1200 HV 0.1 in Vickers hardness in a matrix having a known phase composition.

Hard particles are dispersed in a known phase in order to secure wear resistance, but when the hardness of the hard particles is less than 500 HV 0.1, the desired wear resistance cannot be secured. On the other hand, if it becomes higher than 1200 HV0.1, the relative aggressiveness will increase. For this reason, the hardness of hard particle was limited to the range of 500HV0.1-1200HV0.1 in Vickers hardness. The hard particles to be dispersed in the matrix phase contain Si: 1 to 15%, Mo: 20 to 60%, in terms of mass% of the whole hard particles, from the viewpoint of abrasion resistance, self-lubrication, and relative aggression, and include Cr, Ni, An intermetallic compound having a composition containing 10 to 70% of one or two or more selected from Co and Fe, and an intermetallic compound containing Co, Mo, and Si as a main component, Ni It is set as hard particle containing 1 type, or 2 or more types of the intermetallic compound which has, Mo, and Si as a main component.

Specifically, in the present invention, the hard particles dispersed in the matrix phase contain Si: 1 to 15%, Mo: 20 to 60%, or Cr: 25% or less, and / or Co is further contained 10 to 40%, the remainder is Fe-based hard particles of the composition consisting of Fe and unavoidable impurities, the mass% of the total of the hard particles contains Si: 1-15%, Mo: 20-60% Or Cr: 5 to 25%, the remainder being Co: hard particles having a composition consisting of Co and unavoidable impurities, and Si: 1 to 15%, Mo: 20 to 20% by mass relative to the whole hard particles. Ni-based hard particles having a composition containing 60%, or further containing 5% to 25% of Cr and / or 10% or less of Co, and having a balance of Ni and an unavoidable impurity, or any combination thereof. desirable.

If the hard particles dispersed in the known phase are less than 10% by mass% of the entire valve seat material, the desired wear resistance cannot be secured. On the other hand, when it contains a large amount exceeding 60%, manufacturing cost rises and it becomes economically disadvantageous, moldability deteriorates, relative aggression increases, and bond force with a base falls. For this reason, in this invention, hard particle was limited to the range of 10 to 60% by mass% with respect to the whole valve seat material.

In addition, the valve seat material of this invention may contain 0.2-5% of a solid lubricant by mass% with respect to the whole valve seat material for the purpose of improving cutting property. The blade can be protected by dispersing the solid lubricant in the known phase. Moreover, the dispersed solid lubricant is the starting point of the cutting, and the machinability is further improved. Examples of the solid lubricant include sulfides such as MnS and MoS ₂ , fluorides such as CaF _2, and oxides such as MgSiO ₂ . If the solid lubricant is less than 0.2%, the above effects are not confirmed. On the other hand, even if it contains in large quantities exceeding 5%, a fall of strength arises. For this reason, it is preferable to limit a solid lubricant to 0.2 to 5% of range by mass%. Moreover, More preferably, it is 0.5 to 3%.

Moreover, the valve seat member of the present invention is characterized by having a density of 6.7 g / cm 3 or more and a compressive strength of 350 MPa or more. In addition, the "pressing strength" here is taken as the value calculated | required based on the specification of JISZ2507.

If the density is less than 6.7 g / cm 3, the binding force between the hard particles and the known particle is insufficient, and further, the wear resistance is lowered, and the desired wear resistance cannot be secured under the harsh environment of the gas fuel engine. For this reason, the density was limited to 6.7 g / cm <3> or more. Moreover, it is preferably 6.8 g / cm 3 or more.

Further, in the present invention, the compressive strength is made 350 MPa or more in order to improve the bonding force between the hard particles and the known material and to secure desired wear resistance under the harsh environment of the gas fuel engine. If the compressive strength is less than 350 MPa, the bonding force between the hard particles and the known material is insufficient, and the wear resistance is insufficient, and cracks and damages are likely to occur during valve seat (product) processing. Moreover, Preferably it is 450 Mpa or more.

The valve seat member of the present invention described above is manufactured through a process of repeating compression molding-sintering twice or a process of performing forging molding-sintering in order to ensure the density and the crushing strength stably. desirable.

Next, the preferable manufacturing method of the valve seat material of this invention is demonstrated.

First, as the raw material powder, graphite powder as alloy element powder and at least one of Ni powder, Mo powder and Co powder as pure iron powder and at least one of Cr powder and V powder so as to have the above-described known composition. It is mix | blended so that more than 1 type may become said matrix composition, and the hard particle powder which has the above-mentioned hardness and said composition to become said content, or further mix | blends a solid lubricant powder so that it becomes said content, Preferably Is further blended with stearic acid zinc or the like as a lubricant, mixed and kneaded to obtain a mixed powder. Moreover, in this invention, even if it mix | blends predetermined amount powder of these alloying elements with pure iron powder as mentioned above so that it may become said known phase composition, and may mix | blend predetermined amount low-alloy steel powder and alloy iron powder containing these elements, Or you may use both together.

Subsequently, these mixed powders are filled into a valve seat-shaped die having predetermined dimensions, subjected to a primary compression molding-sintering step of compression molding and temporary sintering to obtain a primary sintered body. Subsequently, it is preferable to set it as the process of repeating a compression molding-sintering process twice to give a secondary compression molding-sintering process which further recompresses a primary sintered compact, and subsequently sinters, and makes it a sintered compact (valve sheet material). Do. By the said process, the sintered compact (valve sheet material) which has desired density and a compressive strength can be obtained.

In addition, it is preferable to perform compression molding by press molding, such as a mechanical press and a hydraulic press. The sintering is preferably performed in a reducing atmosphere or in a vacuum, preferably in a temperature range of 1000 to 1200 ° C.

In the present invention, the forging-sintering step may be used instead of the step of repeating the compression molding-sintering step twice.

Moreover, you may infiltrate low melting metals, such as Pb, Cu, Zn, into the hollow hole of the obtained sintered compact. By infiltrating the low melting point metal into the hole, the wear resistance and the counterpart aggressiveness can be further improved.

The obtained sintered compact (valve sheet material) is cut as needed, and it turns into a valve seat which is a product.

 EMBODIMENT OF THE INVENTION Hereinafter, based on an Example, this invention is demonstrated in detail.

(Example)

The solid lubricant of the kind shown in Table 1 so that a pure iron powder and an alloying element powder may have the known phase composition shown in Table 1, the hard particles of the kind shown in Table 2 and hardness become content of Table 1, or the kind shown in Table 1 further It mix | blended, respectively, so that content shown might be mix | blended further, the zinc stearate as a lubricant was mix | blended, and it mixed and knead | mixed in the V-type mixer, and it was set as the mixed powder. In addition, the compounding quantity of zinc stearate as a lubricant was 1.0 weight part in weight part with respect to 100 weight part of total iron powders, alloying element powders, hard particles, and a solid lubricant.

In addition, in some valve seat materials, low alloy powder A (Cr: 3.0 mass%, Mo: 0.2 mass%, V: 0.3 mass%, balance: Fe), and low alloy instead of a part of pure iron powder and alloy element powder Powder B (Cr: 1.0 mass%, Mo: 0.3 mass%, balance: Fe) was used.

Subsequently, the mixed powder was filled into a metal mold, compression-molded by a mechanical press, and formed into a valve sheet shaped body of 27 mm x 22 mm x 7.0 mm, and then temporarily sintered to obtain a primary sintered body. In addition, after the obtained primary sintered compact is finished by a hydraulic press and recompressed to a valve seat shape having dimensions (27φmm × 22φmm × 6.5mm), re-sintering is performed to perform two compression molding-sintering steps of forming the sintered compact. Repeated (2P2S). Moreover, in some sheet | seat material, the forging-sintering process (FS) which forged and sintered after one compression molding-sintering process (1P1S) was implemented. In addition, sintering was made into the heat processing (sintering process) heated to 1160 degreeC in a reducing atmosphere.

The obtained sintered compact was used as a valve seat material, and the valve seat was completed. About the obtained valve seat, abrasion resistance was investigated while measuring density and a crushing strength.

The density was used for Archimedes method, and the rolling strength was calculated | required based on the specification of JISZ2507. In addition, wear resistance was evaluated by the following test.

The obtained valve seat was mounted on a 2000CC, four-cylinder, four-cycle natural gas engine, and the operation condition was set to 6000 rpm / WOT (full operation) for 24 hours. In addition, the counterpart valve member was made of heat resistant steel SUH35 as the base material, and tribaloy was deposited on the valve face portion. Wear resistance was evaluated by measuring the amount of sediment after wear of the valve seat and the valve on the exhaust side.

The obtained results are shown in Table 3.

In all of the examples of the present invention, it is understood that the amount of wear of the valve seat and the valve, which is the counterpart material, is small on the exhaust side exposed to the harsh environment in the gas fuel engine, and the wear resistance and the relative aggressiveness are improved.

On the other hand, in the comparative example outside the scope of the present invention, it can be seen that the wear of the valve seat is increased, or the wear of the valve is increased, the wear resistance is degraded, and the relative aggressiveness is large.

Claims (3)

In a valve seat member made of an iron-based sintered alloy for an internal combustion engine formed by dispersing hard particles in a matrix of an iron-based sintered alloy, The matrix phase contains, in mass%, C: 0.3 to 1.5%, 1 to 20% of one or two or more selected from Ni, Co, Mo, Cr, and V, with the balance being Fe and unavoidable impurities. Has a known composition consisting of, The hard particles contain, in mass%, 1 to 15% of Si and 20 to 60% of Mo, and 10 to 70% of one or two or more selected from Cr, Ni, Co, and Fe, The balance has a composition composed of unavoidable impurities, and contains 10 to 60% by mass of hard particles having a Vickers hardness of 500 HV 0.1 to 1200 HV 0.1. It has a density of 6.7g / cm 3 or more, and a compressive strength of 350MPa or more Valve seat made of iron-based sintered alloy for an internal combustion engine. The method of claim 1, The base phase further contains 1 to 20% of one or two or more selected from Ni, Co, and Mo, in addition to C, and one or two or more selected from Cr and V in mass%. Characterized Valve seat made of iron-based sintered alloy for an internal combustion engine. The method of claim 1, In addition to Si and Mo, the hard particles further contain at least one of Cr: 25% or less and Co: 10-40% by mass, and the Fe-based composition having a balance comprising Fe and unavoidable impurities. In addition to the hard particles, the Si and Mo, in addition to Co-based hard particles having a composition of 5% to 25% by weight of Cr, the balance consisting of Co and inevitable impurities, and in addition to the Si, Mo , By mass%, containing at least one of Cr: 5 to 25% and Co: 10% or less, and the balance is any one of Ni-based hard particles having a composition composed of Ni and an unavoidable impurity. Valve seat made of iron-based sintered alloy for an internal combustion engine.