JPH0555592B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an iron-based sintered alloy for valve seats, and more specifically, an Fe-based sintered alloy consisting of a mixed structure of an austenite structure, a pearlite structure, and a ferrite structure.
Fine hard particles consisting of a Mo-Fe alloy phase are uniformly dispersed in a C-Co-Ni base structure, and further,
By using infiltration treatment with a Pb alloy or Cu alloy as necessary, the valve seat itself has excellent wear resistance and is less susceptible to damage to the engine valve, which is the mating material on which it slides. This applies to ferrous sintered alloys for valve seats that have a small amount of [Prior Art] Recently, there has been an increasing demand for improvements in automobile engines, such as higher output and higher revolutions, measures to purify exhaust gas, and measures to improve fuel efficiency. For this reason, it has become inevitable for engine valves and valve seats in automobile engines to withstand harsher usage environmental conditions than ever before. In other words, in engine valves, valve seats, etc., it not only improves their own wear resistance, but also reduces damage to the mating material on which they slide.
It is strongly desired to reduce the cost. However, as conventional sintered alloys for valve seats, those made by adding intermetallic compounds such as ferromolybdenum and composite carbides to iron-based alloys have been adopted as excellent sintered alloys for valve seats.
Such sintered alloys have had the problem of not being able to ensure sufficient durability to meet the recent strict requirements for properties as described above. In particular, many conventional engine valves have been treated with a metal filler such as stellite alloy to improve wear resistance. However, due to the recent demand for cost reduction, attempts have been made to abolish the metal fitting process for engine valves, but if the valve seat is made of the conventional material and the metal plate process is abolished, engine valve wear will increase. There was a problem with that. Against this background, there is a strong desire to develop a valve seat material that is less likely to damage the sliding mating material, the engine valve, and that can also ensure its own wear resistance. There was a problem in that the valve seat materials of 2000 and 2000 could not sufficiently meet the above-mentioned requirements. Therefore, in view of the current state of durability of conventional valve seats as described above, the inventors developed a new technology by uniformly dispersing hard particles of a specific composition in an Fe-C base structure mainly consisting of pearlite structure. As a valve seat, it has excellent wear resistance, and
We have already proposed an iron-based sintered alloy for valve seats that causes less damage to engine valves, which are sliding mating materials (title of invention: "Iron-based sintered alloy for valve seats", applicant: Toyota Motor Corporation). Co., Ltd., filing date: April 19, 1980). In addition, as another invention, the iron-based sintered alloy for valve seats of the above invention is further infiltrated with an infiltration alloy such as a Pb alloy or a Cu alloy, thereby achieving even better wear resistance. A ferrous sintered alloy for valve seats has also been proposed (name of invention;
"Iron-based sintered alloy for valve seats," applicant: Toyota Motor Corporation, filing date: May 28, 1980). Furthermore, as another invention, Fe-C-
By uniformly dispersing hard particles of a specific composition in the Co-Ni matrix structure and, if necessary, infiltrating with a Pb alloy or Cu alloy, we have achieved even better results. A wear-resistant iron-based sintered alloy for valve seats has also been proposed (Title of invention: "Iron-based sintered alloy for valve seats", Applicant: Toyota Motor Corporation, Application date: 1982)
(May 28, 2016). [Object of the Invention] The present invention was made in order to solve the problems of the prior art as described above. During the organization, Mo
- Fine hard particles consisting of Fe alloy phase are uniformly dispersed, and if necessary, Pb alloy or Cu
Infiltration of alloy By using infiltration treatment with alloy, the valve seat itself has excellent wear resistance, and the damage to the engine valve, which is the mating material on which it slides, can be reduced. The object of the present invention is to provide an iron-based sintered alloy for valve seats that can be manufactured at low cost. [Structure of the Invention] According to the present invention, such an object is to achieve a weight ratio of C; 0.2 to 0.5%, Mo; 3.0 to 10.0%, Co; 3.0.
~15.0%, Ni; 3.0~15.0%, the remainder essentially consists of Fe, pearlite structure, austenite structure,
Fe-C-Co consisting of a mixed structure of ferrite structure
- An iron-based sintered alloy for valve seats, which is made by uniformly dispersing fine hard particles consisting of a Mo-Fe alloy phase with an average grain size of 3 to 30μ and a hardness of Hv600 to 1300 in a Ni-based matrix structure. Therefore, this sintered alloy has a fine pearlite structure with a volume ratio of 5 to 20% and a volume ratio of 20 to 50%.
Austenite structure with high Co and Ni content, 5~
An iron-based sintered alloy for a valve seat, characterized by having a ferrite structure of 20%, and the remainder consisting of the Mo-Fe alloy phase and pores. and, in weight ratio, C;
0.2~0.5%, Mo; 3.0~15.0%, Co; 3.0~15.0%,
Ni: 3.0 to 15.0%, Pb alloy or Cu alloy infiltration alloy: 10 to 25%, the balance consists essentially of Fe, and Fe-C-Co-Ni consists of a mixed structure of pearlite, austenite, and ferrite structures. In the system base structure, average particle size: 3~30μ, hardness: Hv600~
This is an iron-based sintered alloy for valve seats that is made by uniformly dispersing fine hard particles consisting of a Mo-Fe alloy phase of 1300, and this sintered alloy has a volume ratio of 5 to 20%.
fine pearlite structure, 20 to 50% Co, austenite structure with high Ni content, 5 to 20% ferrite structure, the remainder being the Mo-Fe alloy phase, the infiltration alloy of the Pb alloy or Cu alloy, and This is achieved by using an iron-based sintered alloy for valve seats, which is characterized by having pores. [Operation of the invention] The operation of the invention will be explained below. In addition, in the following description, all contents of alloying elements will be explained in terms of weight ratio (%). In the material of the present invention, C forms a fine pearlite structure by forming a solid solution in Fe of the base structure, and
It is effective because it increases the hardness of the present invention material and improves its wear resistance, but if it is less than 0.2%, the effect of improving wear resistance is not sufficient, and if it exceeds 0.5%, the amount of soft ferrite structure will increase. It is set at 0.2 to 0.5% because this decrease not only increases the damage to the sliding mating material, the engine valve, but also tends to cause dimensional changes due to sub-zero treatment. In addition, both Co and Ni are effective because they dissolve in the matrix structure and improve wear resistance, but if the content is less than 3.0%, the effect of improving wear resistance is not sufficient.
If the amount exceeds 15.0%, the wear resistance improvement effect cannot be expected to be commensurate with the amount added.
It was set at 15.0%. Mo in the material of the present invention has an average particle size of 3 to 30μ, hardness;
Mo− with Fe diffused in Mo with Hv600 to 1300
This is important for uniformly dispersing fine hard particles made of Fe alloy (Mo + ε) phase. And this Mo-Fe alloy (Mo+ε) phase is
It has excellent wear resistance with almost no decrease in hardness even at high temperatures. For the reasons mentioned above, Mo is an important alloying element for improving wear resistance in the material of the present invention;
If it is less than 3.0%, the formation of fine hard particles consisting of the Mo-Fe alloy (Mo + ε) phase will be insufficient, and the effect of improving wear resistance will not be sufficient, and if it exceeds 10.0%, it will cause damage to the sliding mating material (engine valve). It was set at 3.0 to 10.0% because the damage property increases. Next, in the material of the present invention, in the fine hard particles consisting of the Mo-Fe alloy (Mo + ε) phase dispersed in the matrix structure, the average particle size is 3 to 30μ, and the hardness is
The reason for limiting it to Hv600-1300 will be explained. In other words, if the average particle size of the fine hard particles consisting of the Mo-Fe alloy (Mo + ε) phase is less than 3 μ and the hardness is less than Hv600, the wear resistance will not be sufficient;
If the hardness exceeds Hv1300, the damage to the sliding mating material (engine valve) will increase rapidly. Average particle size: 3 to 30μ, hardness;
It is best to set it to Hv600-1300. Next, the infiltration alloy of Pb alloy or Cu alloy is
It is effective because it is infiltrated into the sintered alloy that has been sintered, and its lubricating action improves wear resistance, and its sealing action also improves machinability. If it is less than 25%, the above-mentioned improvement effect will not be sufficient, and if it exceeds 25%, the strength will drop significantly, so it was set at 10 to 25%. In addition, when using a Cu alloy as an infiltration alloy, Pb; 20 to 40%, the balance consisting of Cu.
It is desirable to use a so-called Kelmet alloy. In addition, the volume ratio of ferrite structure is 5 to 20%.
The reason for this is that if it is less than 5%, the soft ferrite structure will not have a sufficient effect of mitigating damage to the sliding mating material, and if it exceeds 20%, the sintered alloy will become too soft and its wear resistance will decrease. 5 to 20%. Next, in the base structure of the present invention material, if the amount of fine pearlite structure is less than 5% or the amount of austenite structure is less than 20%, the base structure becomes too soft and the wear resistance decreases, and the fine pearlite structure becomes too soft. If the amount of structure exceeds 20% and the amount of austenite structure exceeds 50%, the base structure becomes too strong and the damage to the sliding mating material (engine valve) increases. %. Therefore, the material of the present invention has a mixed structure forming a base structure of 5 to 20% fine pearlite structure, 20 to 50% austenite structure, and 5 to 20% ferrite structure in terms of volume ratio, and the remainder is Mo-Fe. alloy phase and pores,
Alternatively, it is composed of a Mo-Fe alloy phase, an infiltrated alloy of Pb alloy or Cu alloy, and pores. In addition, the porosity in the sintered alloy is 8 to 20 in terms of volume ratio.
%, and the average pore diameter is set to 4 to 24μ because if the porosity is less than 8% and the average pore diameter is less than 4μ, the ability to embed foreign matter decreases and foreign matter tends to remain on the sliding surface. The amount of wear on the valve seat increases, while the porosity is 20% and the average pore diameter is 24μ.
If the value exceeds this value, the strength of the valve seat decreases and the valve seat is likely to be abnormally worn or fall off, so the porosity was set to 8-20% and the average pore diameter was set to 4-24μ. [Example] Hereinafter, one example of the present invention will be described based on the attached table. The test piece used in this example was made with reduced iron powder as a base, and each alloying element powder was added to it so that it had the composition shown in Table 1. Furthermore, graphite powder and zinc stearate were added and compacted. It was made into a mixed alloy powder for use. For example, in the material of the present invention, the composition shown in Table 1 is based on reduced iron powder, 0.26% graphite powder, 4% Mo powder, 5% Co powder, and Ni powder.
9% of the powder was added, and furthermore, 0.8% of zinc stearate, which is commonly used as a lubricant, was added to obtain a mixed alloy powder for compaction. Similarly, in the present invention material, the first
With the composition shown in the table, using reduced iron powder as a base, Mo powder, Co powder,
Ni powder, if necessary, an infiltrated alloy of Pb alloy or Cu alloy, graphite powder, and zinc stearate were added to prepare a mixed alloy powder for compaction. In addition, the comparative material contained less than 0.2% (0.15%) of C.
That is. In addition, the comparative material contains more than 10.0% (15.0%) of Mo. In addition, the comparative material contains less than 3.0% (2%) of Mo, more than 15.0% (17%) of Co, and more than 20% (27%) of Pb alloy as an infiltration alloy. This is what I did. The mixed powder for compacting thus produced was compacted at 7 tons/cm ² to form a ring-shaped compact with a diameter of 30 mm x 18 mm and a thickness of 7 mm, and then placed in ammonia decomposition gas. After sintering at 1100°C for 1 hour, no infiltration treatment was performed for the inventive material and comparative material, and infiltration treatment was performed with Pb alloy for the inventive material and comparative material. For comparison materials, sintered alloys were manufactured by performing infiltration treatment with Kelmet alloy. The "base structure" of the sintered alloy produced in this way, the "hardness (Hv) and grain size (μ) of the (Mo+ε) alloy phase", "porosity (Vol%) and average pore diameter ( μ)”, “Hardness (Hv)”, “Density (g/
cm ³ )” are shown in Table 2. The sintered alloy, which had been sintered and optionally infiltrated as described above, was machined into a valve seat shape. The valve seat thus manufactured was press-fitted as an intake valve seat into the aluminum alloy cylinder head of a 4-cylinder, 1600 c.c. engine, and an engine bench durability test was conducted. The engine bench durability test conditions were to use engine valves without stellite metal treatment, use unleaded gasoline as fuel, and operate continuously for 200 hours at 6600 rpm and full load. In the results of this engine bench durability test, the durability of the valve seat was evaluated by measuring the "increase in the width of the valve seat contact surface" and the "amount of engine valve wear" after the end of the test. The engine bench durability test results are also shown in Table 2. As is clear from Table 2, the comparative material has a composition with less than 0.2% (0.15%) of C, so the Mo-Fe alloy (Mo+ε) phase, pearlite structure content is less than 5% (3%), and ferrite. Tissue volume is 20
% (30%), the matrix structure is weak, and the hardness of the (Mo + ε) phase is less than Hv600 (Hv500), and its average particle size is less than 3μ (1μ), so it is difficult to use for engine stands. The amount of wear on the valve seat in the upper durability test is increasing. In addition, the comparative material has a large amount of Mo (15%) exceeding 10% in its composition, so the hardness of the Mo-Fe alloy (Mo+ε) phase exceeds Hv1300 (Hv1500) and its average grain size also exceeds 30μ. (40μ)
As a result, the damage to the sliding mating material (engine valve) increases, the porosity exceeds 20 Vol% (23 Vol%), and the average pore diameter exceeds 24 μ (26 μ). Valve seat wear is increasing. In addition, the comparative material contains less than 3.0% (2%) of Mo, more than 15.0% (17%) of Co, and more than 25% (27%) of Pb alloy as an infiltration alloy. The amount of wear on the valve seat in the engine bench durability test is large, and the amount of austenite structure is more than 50% (55%), so the amount of wear on the engine valve is also large. In contrast to the above comparative materials, the inventive materials had an "increase in the contact surface of the valve seat" of 0.2 mm, as is clear from the engine bench durability test results shown in Table 2. The amount of wear on the engine valves below is less than 4μ, demonstrating excellent durability.

[Table] Kelmet alloy.

〔Effect of the invention〕

As is clear from the above, according to the iron-based sintered alloy for valve seats according to the first invention, the Fe-C-Co-Ni base structure is composed of a mixed structure of an austenite structure, a pearlite structure, and a ferrite structure. By uniformly dispersing fine hard particles consisting of a Mo-Fe alloy phase, the valve seat itself has excellent wear resistance and reduces damage to the engine valve, which is the mating material on which it slides. It has the advantage that it can be manufactured at low cost. Further, according to the ferrous sintered alloy for valve seats according to the second invention, the ferrous sintered alloy for valve seats according to the first invention is subjected to an infiltration treatment with an infiltration alloy of a Pb alloy or a Cu alloy. When used together, in addition to the effect of the first invention, it is infiltrated into the sintered alloy that has been sintered, and its lubricating action improves wear resistance, and its sealing action improves the wear resistance. It has the advantage that machinability can also be improved.

Claims (1)

[Claims] 1. In terms of weight ratio, C: 0.2 to 0.5%, Mo: 3.0 to
10.0%, Co; 3.0 to 15.0%, Ni; 3.0 to 15.0%, the remainder essentially consisting of Fe, in the Fe-C-Co-Ni base structure consisting of a mixed structure of pearlite structure, austenite structure, and ferrite structure. An iron-based sintered alloy for valve seats, which is made by uniformly dispersing fine hard particles consisting of a Mo-Fe alloy phase with an average particle size of 3 to 30μ and a hardness of Hv600 to 1300. , a fine pearlite structure with a volume ratio of 5 to 20%, an austenite structure with a high Co and Ni content of 20 to 50%, a ferrite structure of 5 to 20%, and the remainder consisting of the Mo-Fe alloy phase and pores. A ferrous sintered alloy for valve seats featuring: 2 Weight ratio: C: 0.2~0.5%, Mo: 3.0~
15.0%, Co; 3.0~15.0%, Ni; 3.0~15.0%, Pb
Alloy or infiltration alloy of Cu alloy: 10 to 25%, the balance is substantially Fe, and the average grain size is This is an iron-based sintered alloy for valve seats, which is made by uniformly dispersing fine hard particles consisting of a Mo-Fe alloy phase with a diameter of 3 to 30μ and a hardness of Hv600 to 1300.This sintered alloy has a volume ratio of 5 to 20% fine pearlite structure, 20 to 50% austenite structure with high Co and Ni content, 5 to 20% ferrite structure, and the remainder is the Mo-Fe alloy phase, the Pb alloy or Cu alloy melt. An iron-based sintered alloy for valve seats, characterized by comprising an immersion alloy and pores. 3. The iron-based valve seat according to claim 1 or 2, wherein the sintered alloy has a porosity of 8 to 20% in terms of volume ratio and an average pore diameter of 4 to 24μ. Sintered alloy.