JPH0543913A - Fe base sintered alloy valve seat with extremely low attackability against object - Google Patents

Abstract

PURPOSE:To greatly reduce the attackability to structural material without damaging wear resistance, of a Fe base sintered alloy valve seat used as a structural member in internal combustion engines, etc. CONSTITUTION:A valve seat consists of Fe base sintered alloy having structure where 5-25wt.% carbide dispersed herd particles and/or intermetallic compound dispersed hard particles having MHv 500-1800 are dispersed on the matrix of Fe base alloy. The hard particles of the Fe base sintered alloy are made spherical.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve seat made of a Fe-based sintered alloy which has extremely low opponent attack.

[0002]

2. Description of the Related Art Conventionally, in the manufacture of valve seats, which are structural members of various internal combustion engines such as automobiles in general, excellent wear resistance is required. A structure in which carbide-dispersed hard particles and / or intermetallic compound-dispersed hard particles having a micro Vickers hardness (MHv) of 500 to 1800 are dispersed in an amount of 5 to 25% by weight for the purpose of improving wear resistance. The Fe-based sintered alloys that it has are widely used.

[0003]

However, the above-mentioned conventional F
In e-based sintered alloy valve seats, those with better wear resistance are more prone to wear of the mating valve, and this tendency is even more pronounced with the recent increase in output and speed of internal combustion engines. It is the current situation.

[0004]

Therefore, the present inventors have
From the above viewpoint, focusing on the above-mentioned conventional Fe-based sintered alloy valve seat, and conducting research to reduce the opponent attack without impairing the excellent wear resistance of the valve seat, When manufacturing a valve sheet made of an Fe-based sintered alloy, the raw material powder used for forming hard particles dispersed in the substrate of the Fe-based alloy is generally formed by water atomization, and therefore its shape is not uniform. It exhibits a regular lump shape, and this shape is directly inherited by the hard particles of the Fe-based sintered alloy that constitutes the valve seat, but if this is for forming carbide-dispersed hard particles, it is desirable that the weight% (hereinafter,% Represents weight%), Cr: 10 to 60%, Co: 10 to 40%, W and / or Mo: 5 to 30%, Si: 0.5 to 3%, C: 0.5 to 3%, Contains If necessary, Ni to 5 to 15%, Nb: 0.5 to 5%, V: 0.5 to 5%, and one or more of them, and the balance consisting of Fe and inevitable impurities. If it is for the formation of an alloy having, or an intermetallic compound-dispersed hard particle, it is desirable that Mo: 20 to 40%, Cr: 5 to 15%, Si: 1 to 5% are contained, and the balance is Co. When specified by an alloy having a composition of inevitable impurities and formed by gas atomization, the resulting gas atomized powder has a spherical shape. Therefore, using this as a raw material powder, an Fe-based sintered alloy valve sheet is used. When the manufactured valve seat is manufactured, the hard particles dispersed in the base material have a structure in which the hard particles have a spherical shape, and the conventional Fe-based sintered alloy has a structure in which the hard particles in irregular lumps are dispersed in the base material. Made We obtained the research result that it showed a much smaller opponent attack than the valve seat.

The present invention has been made based on the above-mentioned research results. MHv: 5 was added to a Fe-based alloy substrate.
Carbide dispersed hard particles having 00-1800 and /
Alternatively, in a valve seat composed of an Fe-based sintered alloy having a structure in which intermetallic compound-dispersed hard particles are dispersed at a ratio of 5 to 25%, excellent wear resistance can be obtained by making the hard particles spherical. The valve seat made of an Fe-based sintered alloy is characterized by significantly reducing the aggressiveness of the opponent while maintaining the above.

In the valve seat of the present invention,
The base material of the Fe-based sintered alloy constituting this contains Co: 2 to 10%, Ni: 0.5 to 10% Mo: 0.5 to 3%, C: 0.5 to 1.5%. In addition, if necessary, one or two of Cr: 0.5 to 5%, Nb: 0.1 to 2%, and the balance of Fe and inevitable impurities are contained. It is desirable to use an Fe-based alloy.

Further, in the valve seat of the present invention,
Regarding the hard particles of the Fe-based sintered alloy constituting this, even if the hardness is less than 500 in MHv, the content ratio is 5%.
If the hardness is less than the desired level, the desired wear resistance cannot be ensured. On the other hand, if the hardness exceeds 1800 in MHv or the content exceeds 25%, the aggressiveness against the opponent will sharply increase. Therefore, the hardness is 50 at MHv.
It is specified that the content is 0 to 1800 and the content is 5 to 25%.

[0008]

EXAMPLES Next, the valve seat of the present invention will be described in detail with reference to Examples. As a raw material powder for forming carbide-dispersed hard particles (hereinafter referred to as carbide-based powder), for forming intermetallic compound-dispersed hard particles (hereinafter referred to as intermetallic compound-based powder), and for forming a base material (hereinafter referred to as base powder),
Those having the hardness and composition shown in Table 1, Table 2 and Table 3 and for forming hard particles are, for example, spherical powder having a particle size of 60 mesh or less by gas atomization and particle size: 80 mesh or less by water atomization. Prepare powder in irregular lumps, and base powder is water atomized and particle size: 10
Powders of 0 mesh or less were mixed, and these raw material powders were compounded in the compounding compositions shown in Tables 4 and 5, and zinc stearate: 1
% And mixed for 30 minutes in a mixer, then 5 to 7 to
Press-molded into a green compact at a pressure of n / cm ² , hold this green compact at 500 ° C. for 30 minutes to degrease it, and then in an ammonia decomposition gas atmosphere, to a predetermined temperature within a range of 1100 to 1200 ° C. Sintered under conditions of holding time, the composition substantially the same as the composition, theoretical density ratio shown in Table 4 and Table 5,
And outside diameter: 34 mm x inside diameter: 27 mm x thickness: 7 mm, and a sintered body with a size of 7 mm. Direction: 20% forged, further 600-70
The present invention valve seats 1 to 13 in which hard particles have a spherical shape, and comparative valve seats in which hard particles have an irregular lump shape, by heat-treating at a predetermined temperature within a range of 0 ° C. for 1.5 hours. 1 to 13 were produced respectively.

[0009]

[Table 1]

[0010]

[Table 2]

[0011]

[Table 3]

[0012]

[Table 4]

[0013]

[Table 5]

Next, regarding the various valve seats obtained as a result, the material of the valve: Stellite No. 6 gold, the heating temperature of the valve: 850 to 900 ° C., the seating number of the valve: 3000 r. p. m. Atmosphere: Propane gas with a pressure of 0.4 kg / cm ² and combustion gas with oxygen at a flow rate of 1.6 l / min, Surface heating temperature of valve seat (internal water cooling): 350-4
A wear test was performed under the conditions of 00 ° C. test time: 100 hours, and the maximum wear depth of the valve seat and the maximum wear depth of the valve, which is a mating member, were measured. The measurement results are shown in Tables 4 and 5.

[0015]

From the results shown in Tables 4 and 5, the valve seats 1 to 13 of the present invention all show excellent wear resistance and have a low opponent attack property, while the comparative valve seat 1 Nos. 13 to 13 show excellent wear resistance, but it is clear that the wear of the valve, which is the mating member, is remarkable due to the shape of the hard particles dispersed in the base material being irregular.

As described above, the Fe-based sintered alloy valve seat of the present invention has extremely low opponent attack and excellent wear resistance, so that it is sufficiently satisfactory for high speed and high output of the internal combustion engine. It has excellent performance in response to.

Claims (3)

[Claims] 1. A carbide-dispersed hard particle and / or an intermetallic compound-dispersed hard particle having a micro-Vickers hardness of 500 to 1800 is added to an Fe-based alloy substrate in an amount of 5 to 5.
A valve seat made of a Fe-based sintered alloy having a structure that disperses at a rate of 25% by weight, wherein the hard particles are spherical, and a valve made of an Fe-based sintered alloy having a very low opponent attack characteristic. Sheet. 2. The valve seat made of an Fe-based sintered alloy having extremely low opponent attack property according to claim 1, wherein the valve seat is composed of an as-sintered Fe-based sintered alloy. 3. The valve seat made of an Fe-based sintered alloy having a very low opponent attack property according to claim 1, wherein the valve seat is made of a forged material of an Fe-based sintered alloy.