JP2684774B2 - Iron-based sintered alloy for valve seats - Google Patents

Description

TECHNICAL FIELD The present invention relates to a ferrous sintered alloy for a valve seat of an automobile internal combustion engine.

2. Description of the Related Art A sectional view of a valve train of an automobile engine is as shown in FIG. 1, and a face portion 16 of an intake valve 7 comes into contact with a valve seat 9 by a vertical movement of the valve. The operating temperature of this intake valve is 100 to 400 ° C., and SUH1, 3, 4, and 11 having high softening resistance at operating temperature, high corrosion resistance, and high fatigue strength at the same time have been conventionally used.

Recently, high output, high speed,
There is a growing demand for improvement measures for exhaust gas purification or fuel economy. For this reason, it has become inevitable for engine valves and valve seats in automobile engines to withstand more severe use environment conditions than ever before.

In order to cope with such a severe use environment, a hard facing in which a Co-based or Ni-based metal alloy having excellent wear resistance and high resistance to high-temperature corrosion and high-temperature corrosion is welded to a valve face has been adopted. However, this hard facing is expensive due to the use of expensive metal,
For this reason, an intake valve that eliminates the filling of the face portion has often been used due to cost reduction requirements.

Further, as a conventional valve seat material, Fe-C-Co
-Intermetallic compounds such as ferromolybdenum (Fe-Mo) and ferrochrome (Fe-Cr) or Fe-C-Cr-Mo-V alloys, etc. for the purpose of improving wear resistance of Ni-based materials and Fe-C-based materials Is used (JP-A-56-154110).

[Problems to be Solved by the Invention] Originally, in engine valves, valve seats, etc.,
In addition to improving its own wear resistance, it is required to have little damage to the sliding mating material. However, when using intake valves (SUH1, 3, 4, 11) that do not have a helicopter and combining them with a valve seat in which ferromolybdenum or ferrochrome is added to the Fe-C base material, only the valve face wears. May have occurred.

As measures against this, in JP-A-60-224762, Fe-0.5 to 2.0% C-0.25 to 4.0% Cr-0.1 to 0.6% Mo is disclosed.
A Fe-based sintered alloy having a composition of −0.05 to 0.2% V and in which hard particles of a Fe—Cr alloy are dispersed in a range of 2 to 20% has been proposed. However, this material does not infiltrate Pb, which is a lubricating component, and is used for strengthening the matrix and improving heat resistance.
Co is not added. Therefore, heat resistance and lubricity are insufficient under severe sliding conditions in the intake valve, and it is not possible to completely prevent wear of the valve and the valve seat.

Further, in JP-A-60-251258, Fe-0.5 to 2.0%
C-0.25 to 4.0% Cr-0.1 to 0.6% Mo-0.05 to 0.2% V-3
~ 15 Ni or Co composition, Pb alloy or Sn
Fe-based sintered alloys have been proposed in which the alloy is infiltrated and hard particles of Fe-Cr alloy are dispersed in the range of 5 to 20%. However, although this material has a high Co content and strengthens the matrix and is excellent in heat resistance, it has a drawback that it is difficult to oxidize. Therefore, when used as an intake valve seat, in a low temperature atmosphere (when the seat temperature is about 100 ° C), the seat surface is not oxidized and adhesion occurs, which may cause wear of the valve and valve seat. is there.

The present invention has been made to solve the above-mentioned problems in the case of combining an intake valve made of SUH1, 3, 4, 11 which does not use a heap metal and an intake valve seat made of a ferrous sintered alloy. It is an object of the present invention to provide a sintered alloy for a valve seat, which can ensure the wear resistance of the intake valve and the valve seat even in combination with the intake valve which has abolished the deposit.

[Means for Solving the Problems] The sintered alloy for a valve seat according to the present invention is as a first invention,
C: 0.46-2.0%, Co: 1-3% by weight, Cr: 1.2- by weight ratio
Iron system for valve seats containing 3.6, Mo; 0.06 to 0.40%, V; 0.003 to 0.100%, the balance consisting essentially of Fe, and impregnated with 5 to 25% of Pb, Pb alloy, Cu alloy or Sn alloy. A sintered alloy, which is impregnated with the impregnated alloy in a weight ratio of C; 0.5 to 2.0.
%, Co; 1.0 to less than 3.0%, the balance consisting essentially of Fe, and a Fe--C--Co matrix structure consisting of a mixed structure of an austenite structure and a pearlite structure, in a weight ratio of C: 0.8 to 2.0.
%, Cr; 4 to 18%, Mo; 0.2 to 2%, V; 0.1 to 0.5%, the balance consisting of Fe, and the precipitated C of 10 μm or less inside thereof.
Contains r, Mo, V carbides, particle size 40-150 μm, hardness Hv30
The gist is that the hard particles of 0 to 850 are dispersed at a ratio of 3 to 20% by weight.

In the second invention, the weight ratio of C; 0.46 to 2.0%, Co; 1 to
It is an iron-based sintered alloy for valve seats containing less than 3%, Cr: 0.3 to 5.0%, the balance being substantially Fe, and impregnated with 5 to 25% of Pb, Pb alloy, Cu alloy or Sn alloy. Is impregnated with the impregnated alloy in a weight ratio of C; 0.5 to 2.0.
%, Co; 1.0 to less than 3.0%, the balance consisting essentially of Fe, and a Fe--C--Co matrix structure consisting of a mixed structure of an austenite structure and a pearlite structure, in a weight ratio of C: 0.8 to 2.0.
%, Cr; 10 to 25%, the balance consisting of Fe, and containing the carbide of precipitated Cr of 10 μm or less in the inside, particle size 40 to 15
3 to 20% by weight of hard particles of 0 μm and hardness Hv300 to 850
The point is that they are dispersed at the ratio of.

[Operation] Hereinafter, the operation of the present invention will be described. In the following description, the contents of alloy elements are all expressed in weight ratios (%).
It will be explained in.

First, the reason for limiting the range of each component constituting the hard particles used in the valve seat iron-based sintered alloy of the present invention will be described.

C in the hard particles dispersed in the material of the present invention is Fe, C
It is effective because it reacts with r, Mo, and V to form a carbide to improve wear resistance, but if it is less than 0.8%, the above-mentioned wear resistance improving effect is not sufficient because the amount of carbide is small,
On the other hand, if it exceeds 2.0%, the amount of carbide will be excessive, so 0.8
~ 2.0%.

Also, Cr, Mo, and V are effective in improving wear resistance because they react with C to form carbides, but Cr is less than 4%, Mo
Is less than 0.2% and V is less than 0.1%, the above-mentioned effect of improving the wear resistance is not sufficient because the amount of carbides formed is small. On the other hand, when Cr is 18%, Mo is 2.0% and V is more than 0.5%. Since the amount of carbides formed is excessive, especially V forms a large amount of hard VC carbides and increases the damage to the sliding material (engine valve), so Cr: 4-18%, Mo; 0.2
~ 2.0%, V; 0.1-0.5%.

In the second invention, since the hard particles are made of Fe-Cr-C system, the Cr content is set to 10 to 25%. In the second invention, since the hard particles do not contain Mo and V, when the Cr amount is less than 10%, the amount of carbides is small, and when it exceeds 25%, the amount of carbides becomes excessive and wears the counterpart material. Therefore, the Cr amount is set to 10 to 25%.

Next, the reason why the dispersion amount of the hard particles in the material of the present invention in the matrix structure composed of the mixed structure of the austenite structure and the pearlite structure is 3 to 20% by weight is that the dispersion amount of the hard particles is less than 3%. In this case, since the amount of hard particles is small, the effect of improving wear resistance is not sufficient. On the other hand, when the amount of hard particles dispersed exceeds 20%, damage to the sliding mating material (engine valve) increases. is there. Therefore, the dispersion amount of the hard particles is set to 3 to 20%.

In addition, the hardness of the hard particles is set to Hv300-850, Hv30
This is because if it is less than 0, the effect of improving wear resistance as hard particles is not sufficient, whereas if it exceeds Hv850, the hard particles are too hard and damage to the sliding mating material (engine valve) is increased.

Next, the reason for limiting the range of the components of the raw material powder for a matrix structure used to form the matrix structure of the iron-based sintered alloy for a valve seat in the material of the present invention will be described.

C is an effective component because it reacts with Fe to form a solid solution in a matrix structure composed of a mixed structure of an austenite structure and a pearlite structure and accelerates the sintering reaction, but if it is less than 0.5%, the above effect is not sufficient. On the other hand, if added in excess of 2.0%, a large amount of cementite structure precipitates and embrittles the sintered body, so the content was made 0.5 to 2.0%.

In addition, Co is effective as a solid solution in the matrix structure to strengthen the matrix structure and improve the oxidation resistance and heat resistance, but in the case of the intake valve, the valve seat temperature is about 10%.
Since it is as low as 0 to 400 ° C., if it is contained in an amount of 3% or more, oxidation of the surface of the seat does not proceed and adhesion with the valve face may occur. Conversely, if the Co content is less than 1%, the heat resistance is insufficient, so the Co content was made 1.0 to 3.0%. In the present invention, infiltration alloys such as Pb, Pb alloys, Cu alloys or Sn alloys are infiltrated into the sintered body during the sintering process, and improve the wear resistance by the lubricating action thereof, and the sealing action. Is effective because it can also improve machinability, but if it is less than 5%, the improvement effect is not sufficient.
%, The strength is markedly reduced.
~ 25%.

When a Cu alloy is used as the infiltration alloy, it is preferable to use a so-called Kelmet alloy, which is Pb; 20 to 40% and the balance Cu.

Next, the particle size of the fine carbide that precipitates in the hard particles
The reason why the grain size is 10 μm or less is that if the grain size of the carbide exceeds 10 μm, damage to the sliding material (engine valve) increases.

[Examples] Examples of the present invention will be described together with comparative examples to clarify the effects of the present invention.

Table 1 and Table 2 Compositions of matrix components of the materials of the present invention and comparative materials used as test materials, compositions and amounts of impregnated metals, hard molecules, hardness and density of sintered bodies, mating materials (intake valve ) Are the respective materials.

Hard powder raw material powder to be dispersed in a matrix structure composed of a mixed structure of austenite structure and pearlite structure was prepared according to the composition shown in Table 1 and melted, then by a water spray method, -100
An alloy powder of mesh was produced.

Next, this hard particle raw material powder was added to the iron powder for base composition of each component shown in Table 1 at the compounding ratio shown in Table 1, and further graphite powder and zinc stearate were added to mix for powder compact molding. Alloy powder was used.

6 tons of the powder mixture for green compacts prepared in this way
After powder compacting at / cm ² into a powder compact of φ40mm × 8mm, after sintering treatment at 1100 ℃ × 1 hour in ammonia decomposition gas, Pb alloy was used at the ratio shown in Table 2. It was infiltrated. The infiltrated sintered body was machined into a valve seat shape. Table 2 shows the overall composition, hardness and density of the valve seat material.

The valve seat manufactured in this way is
An intake valve seat was press-fitted into an aluminum alloy cylinder head of a 00cc engine, and an engine bench durability test was performed in combination with an intake valve made of SUH3.

The engine bench durability test was performed using unleaded gasoline as the fuel, the valve seat temperature was relatively low, and oxidation was difficult to proceed at 5600 rpm and idle rotation (about 800
rpm) and was operated for about 600 hours.

The durability test was evaluated by the amount of wear of the valve seat before and after the test, the amount of increase in the contact width of the valve seat, and the condition of the sliding surface. The results obtained are shown in Table 3.

As is clear from Table 3, in Comparative Material 1 in which ferro-molybdenum is used as the hard particles, the valve seat hardly wears, and the valve wears excessively. Further, the comparative material 2 has a Co content of 0%, but the wear amount of both the valve seat and the valve face is 2 to 4 of the example of the present invention.
It was about twice, and there was no infiltration of Pb, so surface roughness due to adhesion was observed. Comparative material 3 had a Co content of 4%, but adhesion of the valve seat material was observed, and
A wear of about μ was observed.

On the other hand, invention materials 1 and 2 corresponding to the first invention
Inventive material 2 corresponding to the invention has a width increase per valve seat of 0.1 to 0.2 mm, and is compared with comparative materials 1 to 3.
As little as 1/2 to 1/4 and 12 valve face wear
~ 15μ, 1/3 ~ 1/1 compared to Comparative materials 1-3
It was 2 and was excellent in abrasion resistance, and it was confirmed that the material of the present invention exhibits excellent durability.

[Effects of the Invention] As described in detail above, the iron-based sintered alloy for a valve seat according to the present invention has a Fe-Cr-based matrix structure composed of a mixed structure of an austenite structure and a pearlite structure. An alloy obtained by dispersing fine hard particles of an alloy and infiltrating an infiltrating alloy such as a Pb alloy or a Cu alloy.
By reducing the Co content in the Co-based matrix structure, adhesion in the low temperature range is prevented, the valve seat itself has excellent wear resistance, and the damage to the mating material can be minimized. The wear resistance and durability of the intake valve and the valve seat can be ensured even in combination with the intake valve, which has been abolished. As a result, intake valves without a heap can be used, which enables resource saving and engine cost reduction. In addition, the hardness of hard particles is lower than that of ferro-molybdenum-added seat valve materials that have been widely used in the past. Therefore, the workability is improved.

[Brief description of the drawings]

 FIG. 1 shows a sectional view of a valve train of an automobile engine. 7 ... Valve, 9 ... Valve seat, 16 ... Face part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Ishii 1 Toyota-cho, Toyota-shi, Aichi Prefecture Toyota Motor Co., Ltd. (72) Inventor Takeshi Nakakobara 1-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd.

Claims (2)

(57) [Claims] 1. A weight ratio of C; 0.46 to 2.0%, Co; 1 to less than 3%, Cr; 1.2 to 3.6, Mo; 0.06 to 0.40%, V; 0.003 to 0.100%.
An iron-based sintered alloy for valve seats containing 5% to 25% of Pb, Pb alloy, Cu alloy or Sn alloy, which is substantially composed of Fe, and is impregnated with the impregnating alloy. At C; 0.5-2.0%,
Co; containing 1.0 to less than 3.0% and the balance consisting essentially of Fe,
In a Fe-C-Co matrix structure composed of a mixed structure of an austenite structure and a pearlite structure, C by weight ratio: 0.8 to 2.0%,
Cr; 4 to 18%, Mo; 0.2 to 2%, V; 0.1 to 0.5%, the balance consisting of Fe, and Cr and M precipitated within 10 μm
Containing o and V carbides, particle size 40-150μm, hardness Hv300-8
An iron-based sintered alloy for valve seats, characterized in that 50 hard particles are dispersed in a proportion of 3 to 20% by weight. 2. A weight ratio of C; 0.46 to 2.0%, Co; 1 to less than 3%, Cr; 0.3 to 5.0%, and balance of Fe, Pb, Pb alloy, Cu alloy or Sn. An iron-based sintered alloy for a valve seat, which is impregnated with an alloy in an amount of 5 to 25%, which is impregnated with the impregnated alloy in a weight ratio of C: 0.5 to 2.0%,
Co; containing 1.0 to less than 3.0% and the balance consisting essentially of Fe,
In a Fe-C-Co matrix structure composed of a mixed structure of an austenite structure and a pearlite structure, C by weight ratio: 0.8 to 2.0%,
Cr: 10-25%, balance Fe, 10% inside
Includes precipitated Cr carbide of less than μm, particle size 40-150μ
An iron-based sintered alloy for valve seats, characterized in that hard particles having m and hardness Hv 300 to 850 are dispersed in a weight ratio of 3 to 20%.