JPS60147514A - High-temperature abrasion resistant valve seat - Google Patents

Abstract

PURPOSE:To improve abrasion resistance, heat conduction and anti-loosening properties by a method wherein a double layered structure of first layer, including the abutting surface of a valve, and second layer, supporting the first layer, is formed and respective layers are constituted of specified constituents such as Ni or the like consisting of specified weight ratios. CONSTITUTION:The iron base sintered alloy of double layered structure, consisting of the first layer 1 including the abutting surface of the valve and the second layer 2 supporting the first layer 1, is formed and both layers 1, 2 are connected by sintering metallurgically. The first layer 1 is constituted in weight ratio of the constituents of Mo; 2.5-15%, Co; 1-15%, Ni; 1-15%, Co; 0.2-0.7% and balance of Fe and impurities up to 2% while ferro-molybdenum having average particle diameter 10-30mu are dispersed uniformly in the constitution. The second layer 2 is constituted in weight ratio of the constituents of Ni; 1-5%, C; 0.2- 0.7% and balance of Fe and impurities up to 2%. Further, the difference of the amount of C between said both layers 1, 2 is specified to up to 0.3%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an iron-based sintered valve seat used in an internal combustion engine.

[Prior art]

Iron-based sintered metal is often used for valve seats in internal combustion engines because of its good wear resistance, but it is
Because of wear-resistant carbide extrusion, materials with a carbon content of around 1% are used. On the other hand, as the performance of internal combustion engines has improved in recent years, materials with better thermal conductivity are being sought after, but sintered metals inherently contain many pores, and conventional materials have a base structure of austenite + pearlite. Therefore, it often has poor thermal conductivity. As a solution, Cu i
Alternatively, there is a method of infiltrating Pb gold, but as the pores of Cu are filled by infiltration, the formation of oxides with lubricating action that were conventionally generated around the pores at high temperatures is inhibited, resulting in a decrease in wear resistance. Although C and Pb have an excellent lubricating effect, they have the problem of environmental pollution. Another problem is that the cost increases due to infiltration. Therefore, sintered rubber sheets, which are non-infiltrated, have good thermal conductivity, and are resistant to high temperature wear, have been sought after.

[Purpose of the invention]

The present invention meets the above-mentioned conventional demands, and aims to provide a low-cost sintered valve seat that is non-infiltrated, has excellent thermal conductivity, and has excellent wear resistance and loosening resistance. It is.

[Structure of the invention]

The valve seat of the present invention is an iron-based sintered alloy having a two-layer structure consisting of a first layer including the valve contact surface and a second layer that is a base material that fully supports the first layer. The second layer is metallurgically sintered, and the first layer has a gravity ratio of MO25 to 15 inches, eol to 15 inches,
The second layer consists of a component consisting of Ni 1 to 15 cycles, 002 to 0.7 cycles, the balance Fe, and less than 2 layers of impurities, and ferromolybdenum with an average particle size of 10 to 30 μ is uniformly dispersed. Ni 1-5%, CO, 2-o, 7 in weight ratio
z, the balance is Fe and less than 2% of impurities, and the difference in Cu between the first layer and the second layer is 0.3 or less.

In the valve seat of the present invention, in addition to the above components, the Ki 1 layer further contains Cu0.5-5%, MnO2-2tI), PO90
5~0, i, B O, 01~0.5%, qr O,
5-20%, W 0.5-8%, VO, 3-8%
, NbO, 1-, and M.

Incidentally, in the present invention, unless otherwise specified, the weight percentages are expressed as percentages by weight.

The reason for limiting each component element used in the present invention will be explained below.

First, to explain the components of the first layer, MO (molybdenum) exists mainly as wear-resistant particles, and a portion is solidly dissolved in the matrix to strengthen it. If the value is outside the upper limit or lower than the lower limit, the wear resistance will be insufficient, which is undesirable. Similarly, in the case of the average particle size of ferromolybdenum, if it deviates from the limited value, the wear resistance becomes poor.

CO (cobalt) and Ni are dissolved in the matrix to strengthen it and improve the heat resistance, high temperature strength, oxidation/corrosion resistance, and wear resistance of the valve seat. It is diffused into ferromolybdenum particles, increasing the retention of these particles in the matrix. In either case, below the limit value, the effect of addition is small, and if the limit value is completely reduced, not only will the cost be increased, but the effect will not improve even though it is added, and retained austenite will increase, impairing the material stability. Both CO and Ni were limited to 1 to 15.

C (carbon fi, 'f+ penetration are insufficient, and if the ratio exceeds 0 or 7, carbides and retained austenite which reduce thermal conductivity will increase, which is not preferable. Therefore, C is 0.2~
It was limited to 0.7%.

Next, optionally added elements in the first layer will be explained.

Cu (copper) and Mn (manganese) are added to form a solid solution in the matrix to strengthen it, but below the limit, the effect is small, and beyond the limit (ii), Cu not only increases the cost but also weakens the alloy. Since the dimension n degree decreases, it is limited to a maximum of 5 degrees, and since Mn becomes brittle due to oxidation, it is limited to 2% or less.

P (phosphorus) and B (boron) form Fe-P- during sintering.
C, Fe-H-C OyoU Cholera-faMOk included
(r) The liquid phase is completely formed, promoting the progress of sintering, and making the pores of the alloy all spherical, increasing the IJ lux strength, and the residual liquid phase also acts as wear-resistant particles, but below a limited value, its effect is reduced. On the other hand, if it exceeds the visual standard value, the dimensional accuracy of the alloy will significantly deteriorate and the alloy will become brittle, which is not preferable.

Cr (chromium), W (tungsten), ■ (vanadium) and Nb (obium) mainly exist in the form of ferroalloys or carbides, and improve the wear resistance of the alloy, but below the limit value, the effect is small, and when the limit value is exceeded. Exceeding this will not only result in high costs and become too hard, resulting in a decrease in rigidity.
This is not preferable as it increases the aggressiveness towards the valve, which is the mating material, so it was set to below each limit value.

Nao, Cu, Mn, P, B, Cr, W, V
, Nb can be added alone or on 2a19 within the range of each limit value as necessary. Further, other elements other than ferromolybdenum may be added as a suitable briar alloy. MO may be added as pure MO or pre-alloy in addition to the MO contained in ferromolybdenum as long as the total amount is within the limited value.

Next, the components of the second layer will be explained.

The 21st layer is only for supporting the first layer, and if the valve seat is used in an aluminum alloy cylinder head, the performance required for the second layer is low, so a material that is as inexpensive as possible is selected.

Ni is added because it not only strengthens the matrix and improves the high-temperature strength, but also contributes to stably shrinking the sintered body and reducing pores. However, if less than 1 treble is added, the effect is small, and if 5 tres or more is added, not only will the cost increase, but the effect will not increase in proportion to the addition, and retained austenite will increase, similar to the case of the first layer. The temperature was set at 5mm below because the thermal conductivity would be completely destroyed.

The effect and reason for limitation of C's addition are the same as No. 141.

In addition, in the present invention, the difference in C content between the matrix of the first layer and the 27th tit is limited to 0.3 inch or less, but if it exceeds 0.3 inch, the difference in the amount of C between the matrix of the first layer and the 27th tit is limited to 0.3 inch or less. This is because the diffusion of C toward the low C content layer cannot be ignored, and both materials are not stable as intended, which is undesirable. Moreover, it has an adverse effect on the stabilization of the carbon potential of the atmosphere during sintering, which is undesirable since it impairs the stability of the material. Note that the high C content layer may be either the first layer or the second layer, but is preferably the first layer.

The ratio of the thickness of the first layer and the second layer is selected depending on the purpose,
``Thermal conductivity can be adjusted by adjusting the thickness of both layers appropriately.

〔Example〕

The present invention will be explained below using examples.

Example 1 Pure iron powder (-100 mesh: below 0 indicates the particle size)
4s Fe-63% MO alloy powder (-100 mesh), 1st Co powder (-100 mesh).

0.8 part of stearic acid was added as a lubricant to 100 parts of a mixed powder (intussusception: the same applies hereinafter) made by adding 1 hour of Ni powder (particle size 5μ) and 0.251 graphite powder (particle size 10μ). A powder for the first layer was obtained by mixing for 30 minutes using a type (3) mixer.

Next, 8 parts of zinc stearate was added to 100 parts of a mixed powder made by adding 1 inch tooth powder (particle size 5 μ) and 05 graphite powder (particle size 10 μ) to pure iron powder (-ioo mesh). The mixture was mixed for 30 minutes using a type (■) mixer to obtain a powder for the second layer.

After that, the powder for the second layer was filled without cutting into a mold having a molding cavity with an outer diameter of 30wn and an inner diameter of 20mm, and after preliminary pressurization with an upper punch, the powder for the first layer was filled to 7 tons.
It was pressure-molded to a height of 8 parrots at a pressure of /, 7. In addition, during molding, the JIA amount 'f! :It was adjusted. In addition, as shown in the figure, the upper part pressing surface of the molded product is made of the first layer (1) and the second layer
The shape of the bonding interface with layer (2) was a curved surface that descended toward the inner diameter side 1 of the annular body.

The obtained powder compact was heated to 1 in a total ammonia decomposition gas atmosphere.
After sintering at 150°C for 60 minutes, the first layer became F'e-2,
5%Mo-11Co-1%Nj -0.2%C (D1m
The second layer is F'e-1qI)Ni-0,2'l
A composite sintered body having a composition of C and in which both layers were metallurgically sintered and bonded was obtained.

Hereinafter, inventive material 1 having the composition described in Table 1 below was carried out in the same manner.
-7 were produced. Comparative materials 1 to 3 were also produced in the same manner using the same raw material powder.

Comparative material 2 is a sintered body infiltrated with Pb=i15 and comparative material 3 is a conventional valve seat material in which Cu is similarly infiltrated with 10. These sintered bodies were processed into the shape of a valve seat and assembled into an engine with a 1600CC aluminum alloy cylinder head, and a long bench test was carried out equivalent to 50,000 km - 4-way high-speed running. The results are shown in Table 1. As can be seen from the results in Table 1, the present invention materials 1 to 7 all showed the same results as comparative material 2 with a tappet clearance of 0.05w++ or less after the test1, and the pullout load was also 1.
000 KyJJ, and the dimensional stability and loosening resistance were also good.

Note) The first layer component compositions of Inventive Materials 4 to 7 in the table above indicate that each element was added to the first layer component of Inventive Material 2.

Example 2 Using the same sintering method as in Example 1 using raw material powders, Il, and Ij, 20 test pieces with a diameter of 20 mm and a thickness of 20 pieces were manufactured. In addition, the present invention material has a first layer:second layer ratio i
The ratio was 50:50. In addition, a sample of a comparative material was similarly prepared with the same composition as that described in Example 1.

Table 2 shows the results of thermal conductivity (IL) measurements of these specimens.As can be seen from the results in Table 2, the present invention material 2 has good wear resistance. It showed almost the same thermal conductivity as

Table 2 [Effects of the Invention] The present invention has a two-layer structure including a first layer that includes a valve contact surface that requires wear resistance, and a second layer that serves as a base material that supports the first I-. As a result, a valve seat can be obtained that has wear resistance, good thermal conductivity, and loosening resistance that have not been obtained with conventional single-structure sintered bodies. Moreover, by adjusting the ratio of the thickness of the first layer and the second layer, the thermal conductivity and loosening resistance can be adjusted, so it can be used not only for aluminum alloy cylinder heads but also for conventional cast iron cylinder heads. It also has the advantage of being usable.

[Brief explanation of drawings]

The figure is a sectional view showing the valve seat of the present invention. In the figure, 1...First layer 2...Second layer Patent applicant: Toyota Motor Corporation Japan Powder Alloy Co., Ltd.

Claims (2)

[Claims] (1) An iron-based sintered alloy with a two-layer structure consisting of a sheath including a pulp contact surface and a second layer supporting the first layer, where the first layer and the second layer are metallurgically It is sintered and bonded, and the first layer has a weight ratio of Moz 5 to 15% and C01 to 15 Chi. Nt 1~t 5rs, CO, 2~o, 7*, remainder F
The second layer is composed of a component consisting of impurities of less than 2% and a composition in which ferromolybdenum with an average particle size of 10 to 30μ is uniformly dispersed, and the second layer has a weight ratio of Ni 1 to 5T, co, 2 to 0.7%,
A high-temperature wear-resistant valve seat for an internal combustion engine, characterized in that the remainder is Fe and less than 2 mos of impurities are present, and the difference in C amount between the 11th wheel and the 2nd wheel is 0.3 coefficient or less. . (2) In addition to the above components, the first layer also contains Cu □, 5~
5%, Mn□, 2-2%, PO, 05-0.
8%, 13o, oi ~0.5%. A valve seat according to the first aspect of the claim.