JPH01129951A - Sintered alloy for valve seat for internal combustion engine - Google Patents

Abstract

PURPOSE:To inhibit the wear of valve seat in gasoline engine and to stabilize the function of valve seat by dispersing prescribed percentages of Cu and Pb into a carbide-dispersed iron matrix in which respective contents of C, Si, Cr, Mo, V and Fe are specified. CONSTITUTION:A sintered alloy for valve seat of internal combustion engine has a structure where 15-20wt.% (based on the composition as a whole), in total, of Cu and Pb are dispersed in a carbide-dispersed iron matrix. The above carbide-dispersed iron matrix has a composition consisting of, by weight, 1.2-2.7% C, 0.2-2.5% Si, 11-27% Cr, 0.6-4% Mo, <=2.5% V, and the balance Fe, and further. The above Cu and Pb are incorporated in the weight ratio of Cu to Pb of 80:20-60:40.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a valve seat for an internal combustion engine that functions stably with both unleaded gasoline and leaded gasoline.

[Prior Art] After automobile exhaust gas regulations were introduced, the valve seats of internal combustion engines were improved based on unleaded gasoline (approximately 0.5Q Pb/gallon).
For example, as disclosed in Japanese Patent Publication No. 55-36242, a sintered material in which lead is impregnated into the pores of a sintered alloy steel exhibits good wear resistance and has been put into practical use.

In addition, for this type of valve seat, Japanese Patent Application Laid-Open No. 51-37011,
Japanese Patent Publication No. 51-44684, Japanese Patent Publication No. 60-258449
As shown in No. 1, there is a sintered material in which the pores of sintered alloy steel are impregnated with copper-lead alloy.

However, worldwide, the reality is that leaded gasoline (for example, about 3 gPb/gallon) is still used in Europe, Australia, the Middle East, etc. for the purpose of improving engine output.

In the case of engines that use leaded gasoline as fuel, combustion products such as lead oxide, lead sulfide, and lead sulfate adhere to the valve and valve seat surfaces during combustion. Site-based heat-resistant steel ingot materials are generally used.

[Problems to be Solved by the Invention] As mentioned above, valve seats for gasoline engines are divided into those suitable for use with unleaded gasoline and those suitable for use with leaded gasoline.
When this valve seat is applied to a leaded gasoline engine, wear becomes noticeable. Furthermore, similar results will be obtained if a valve seat made of martensitic heat-resistant steel is applied to an unleaded gasoline engine. Therefore, it would be extremely convenient if C could be used without distinction between leaded and unleaded products, domestic specifications, and export specifications.

An object of the present invention is to provide a valve seat that is resistant to wear whether the fuel used in the internal combustion engine is unleaded gasoline or leaded gasoline.

[Means for Solving the Problems] In order to achieve the above object, the present invention is achieved by configuring the material of the valve seat as follows. That is, the composition is 01.2 to 2.7% by weight, Si0.2
~2.5%, Cr11~27%, Mo0.6~4%,■
In the iron base in which hard metal carbide consisting of 2.5% or less and the balance of Fe is dispersed, the total of CLI and PB is dispersed in the total composition of 15 to 25% by weight, and the Cu:Pb component is in the weight ratio. It is a sintered alloy characterized by a ratio of 80:20 to 60:40.

[Effect] Next, the effects of each element will be explained.

First, we will discuss base composition.

Effect of solid solution of Cr on two pig iron bases to improve high temperature strength and C
It is a component that contributes to improvement of wear resistance by combining with and precipitating hard carbide in the matrix. If the content is less than 11%, the base strength is too low. Also, it is prone to oxidative wear when used. On the other hand, even if it exceeds 27%, unleaded gasoline has little effect considering the amount added, and unleaded gasoline tends to warp and wear easily.

MO: Like C, it is a carbide-forming element and has the same effect as Cr. If it is less than 0.0%, it has little effect, and if it exceeds 4%, oxidative wear increases.

V: Forms the same carbide as Cr and Mo. ■Carbide is relatively hard. A small amount is effective, and too much will wear out the other valve, so it is best to add less than 2.5%.

Si This is an element added for the purpose of preventing wear due to oxidation.It is effective when added at 0.2%, and even when added in excess of 2.5%, the effect is small considering the amount of addition.

C: Solid solution in Fe to strengthen the base and Cr.

It combines with Mo and V and acts to precipitate hard carbides. If it is less than 1.2%, the amount of carbide produced is small and wear resistance cannot be expected. Moreover, if it exceeds 2.7%, the carbide becomes coarse and increases the wear of the mating valve during use.

As mentioned above, the characteristics of the iron base are that the Vickers hardness is Hv2000.
~3000 hard precipitated carbides (C".

It is configured to contain a large amount of Fe) 7 C3, (Cr, Mo, Fe) 7 C3 and VC.

Next, we will talk about the dispersion composition.

A portion of CIJ and Pb:Cu diffuses into the base and strengthens the base. In addition, a portion remains in the form of a copper phase, and the thermophilic conductivity of copper has the effect of improving the heat dissipation of the valve seat during use.

On the other hand, PB has the effect of preventing adhesive wear with valves during use, and is a highly effective component for unleaded gasoline. However, leaded gasoline reacts with the sulfur in the fuel to create combustion products that adhere to the seat face and accelerate wear.

When CLI and Pb coexist in a predetermined state, both lead-free and leaded materials are resistant to wear.

The weight ratio of Cu to PB is preferably in the range of 80:20 to 60:40. When the ratio of Cu is more than 80, the properties of Cu become noticeable and wear increases when used for unleaded gasoline. Furthermore, if the Cu ratio is less than 60, the properties of PB will appear and wear will increase when used for leaded gasoline. Furthermore, Cu and pb
It is important that the structure be dispersed in the matrix, and it is preferable that the alloy be in an alloy state in which PB is dispersed in Cu. This structure is obtained by a method of infiltrating Cu-Pb into an iron-based sintered body, and a method of blending Cu-Pb powder with alloyed iron powder, forming, and sintering. The total content of Cu and PB is 1 in the overall composition.
If it is less than 5%, the above-mentioned effects will be small, and if it exceeds 25%, the amount of base will decrease accordingly, resulting in a decrease in strength and poor wear resistance.

[Example] Hereinafter, it will be explained in detail using examples.

Example 1 Example 1 compares the wear characteristics of materials in which copper is dispersed, lead is dispersed, and copper-lead is dispersed in the base material.

First, the composition is Fe-18,5Cr-1,2M.

-0,6V-0,5Si-1,80 ferroalloy powder with a particle size of 100 mesh or less is added with 10.8% zinc stearate to make a mixed powder, and after compression molding into the specified dimensions of the valve seat shape. , sintered at a temperature of 1150° C. in an ammonia decomposition gas atmosphere furnace.

Then, a molded body of Cu-3co alloy powder and Cu-30Pb
A molded body of alloy powder was prepared, and infiltration treatment was performed together with the sintered body at a temperature of 1150° C. in an ammonia decomposition gas atmosphere furnace to create Sample 1 and Sample 2 for the wear test. CO in the Cu-Go alloy is added to prevent the base material from being eroded during infiltration. Another sample 3 was prepared in which the sintered body was heated and held in a vacuum container, then immersed in molten Pb, pressurized with nitrogen gas, and infiltrated with lead.

Table 1 shows the measurement results of the infiltration amount, radial crushing strength, and thermal conductivity of these samples.

The amount of infiltration is about 19%, the radial crushing strength is the highest in the copper-rich composition, and the thermal conductivity is also good in the copper-rich composition.

The wear resistance was evaluated using a 2,000cc, 6-cylinder engine.The sample was machined into a predetermined shape and installed, and the engine was rotated at a rotational speed of 6,000.
It was operated at full load with rotation.

The material of the valve is heat-resistant steel 2L-4N, and the fuel is leaded gasoline (3 g, Pb/gallon) and unleaded gasoline (0,
5(] Pb/gal). Figure 1 shows the results of measuring the amount of wear on the valve seat after 200 hours of operation.

According to this, it can be seen that the copper infiltrated sample 1 is good against leaded gasoline, but wears significantly when unleaded gasoline is used. On the contrary, lead layer-soaked sample 3 shows extremely high wear when using leaded gasoline. Copper-lead alloy infiltrated sample 2 has good wear resistance for both leaded and unleaded samples.

Table 1 Sample 1 2 3 Infiltrated surface (%)
18.3 18.5 19.8 (%) Radial crushing strength (kq/li2) 135 115
75 (ka/mm2) Thermal conductivity 0.17 0.13 0.
07 (Cal/an, s, 'C) Example 2 In Example 2, we investigated the effect of Pb-containing coral in Cu-Pb alloy in a copper-lead dispersion material that has good wear resistance for both leaded and unleaded gasoline. This is what I researched.

The alloyed iron powder was the same as in Example 1, and Cu-Pb alloy powder 1. t
Ptl ffl is 10%, 20%, 30%, 40% 4
Prepare the types and add 20% of each Cu-PB alloy powder to the alloy iron powder.
Mixed powders containing 0.8% of zinc stearate and 0.8% of zinc stearate were formed to give a sintered density of 8.0 (II/C13), and then sintered under the same conditions as Example 1 to obtain Samples 4 to 7. It was created.

The engine test was conducted under the same conditions as in Example 1, and the results of measuring the amount of valve seat wear after the test are shown in FIG. In addition, the results of Sample 1 and Sample 3 of Example 1 are added in the figure.

According to this, the Pb suspension of the Cu-Pb alloy to be added is 20
In the range of ~40%, both of the two types of fuel show results with less wear. Further, it can be seen that if it is less than 20%, wear increases when using unleaded gasoline, and when it exceeds 40%, wear increases when using leaded gasoline.

Example 3 Based on the results of Examples 1 and 2, Example 3
The relationship between the amount added to alloyed iron powder and wear was investigated using a 0% PB alloy as a representative example.

The same alloy iron powder Cu-30Pb alloy powder as in Example 1 was used, and CIJ-30Pb alloy was 10% and 15%.

20%, 25%, and 30%, each with 0.8% zinc stearate added to make a mixed powder, sintered density 8.0g
/ca+3, and then sintered under the same conditions as Example 1 to prepare a sample. Engine test is Example 1
The conditions are the same as that of the third test, and the results of measuring the amount of valve seat wear after the test are
As shown in the figure.

According to this, the amount of Cu-30Pb alloy added is 15 to 2
Within the range of 5%, both leaded gasoline and unleaded gasoline have little wear, but outside this range, the wear resistance becomes poor.

Example 4 In Example 4, the relationship between the composition and wear resistance of the ferroalloy forming the matrix and the comparison with conventional materials were conducted.

The composition in Table 2 shows the main components of the ferroalloy powder excluding Fe and unavoidable impurities in percentages, and each ferroalloy powder contains Ct.
j-30Pb alloy at 20% constant and 0.8% zinc stearate added respectively to make a mixed powder, and the sintered density was 8. Oa
/ca+3, and then sintered under the same conditions as Example 1 to create Samples 6 to 15. Samples 6 to 9 are materials of the present invention.

Margin below Table 2 Na CrMoVSiC 6 Invention material 18.5 1.2 0.6 0.5 1.
87 # 11,8 1.2 0,9 0,4
1,88 ,, 26,5 1,1 0.9
1.3 1,99 II 18,5 1,
6 0.1 2.5 1.810 Comparative material 6.
10.51.80.32:211, 31,2
1,3 0.5 1,9 1,912 〃22
．． 5 4.9 1.1 0.5 1,513 r
t 18.4 1,3 2,5 0,5 1.6
14 # 18,2 1,2 0.8 0,5
0. (315n 14,5 1.6 0,7
0.5 3.116 Conventional material Fe-6,5Co
-1,5N i-0,8c15. Opb17 n
Fe-20Cr-1,5N i-2S i-1
, QC Also, Samples 16 and 17 are conventional materials and are shown in overall composition. Sample 16 is Go, manufactured by Special Publication No. 55-36242, which has a proven track record for valve seats for unleaded gasoline.

The material is a lead-infiltrated iron-based sintered alloy containing Ni and C. Sample 17 is a valve seat made by cutting a 5UH4 heat-resistant steel lumber ω.

The engine test was carried out under the same conditions as in Example 1, and the results of measuring the wear m of the valve seat after the test are shown in Table 3.

Table 3 Wear 1 (μ-) Lead-free Leaded 6 Invention material 5545 7 # 50 608 #
60 4G9 #
55 4510 Comparative material 230
25511 #90 4
012 #95 4513
# 105 4014 #
135 15015 #
120 7516 Conventional material
50 380″ 17 tt 5
00 60 According to this, it can be seen that the samples with the base iron alloy composition of the present invention show a small amount of wear in both leaded gasoline and unleaded gasoline, but the comparative materials of Samples 10 to 15 have a large amount of wear. In addition, among the comparative materials, sample 11
Sample 12 and Sample 12 have a relatively small amount of wear, but are not preferable because they wear out the other valve.

It can be seen that the conventional material shows excellent properties with one fuel, but wears out significantly with the other fuel.

[Effects of the invention] As detailed above, the valve seat of the present invention can suppress wear to a minimum in both leaded gasoline engines and leaded gasoline engines, and is stable over a long period of time. It becomes functional.

[Brief explanation of the drawing]

Figure 1 is a graph showing the wear results of valve seats made by infiltrating sintered iron alloy with each ridge material, and Figure 2 is a graph showing the wear results of valve seats infiltrated with sintered iron alloy.
Figure 3 is a graph showing the relationship between the Pb content of the alloy powder and the wear of the valve seat, and Figure 3 is a graph showing the relationship between the addition m of Cu-Pb alloy powder mixed in the iron alloy powder and the wear of the valve seat.

Claims (1)

[Claims] Composition is C1.2-2.7%, SiO0.2-2 by weight ratio
．． 5%, Cr11-27%, Mo0.6-4%, V2.
In the carbide-dispersed iron base consisting of 5% or less and the remainder Fe, the total of Cu and Pb is dispersed in a total composition weight ratio of 15 to 25%, and the weight ratio of Cu:Pb is 80:20 to 60:
40. A sintered alloy for a valve seat of an internal combustion engine, characterized in that the alloy is 40.