JPH0318604A - Valve seat - Google Patents

Abstract

PURPOSE:To obtain heat resistance and wear resistance at high temperature, and to prevent increase in wear of opponent material by manufacturing valve seat material through infiltration of Pb or Pb alloy into holes of a sintered body having a prescribed composition. CONSTITUTION:Cu or Cu alloy coating of 5 to 30weight% is applied to the whole or a part of raw material powder of one kind or more. Powder, which is composed of C of 0.4 to 3.0weight%, Mo and/or W of 5 to 25weight%, Co and/or Ni of 0.5 to 20weight%, Si of 0.1 to 0.9weight%, P of 0.1 to 0.8weight%, Cr of 2 to 15weight%, Cu of 5 to 15weight%, Fe and impurities for the remainder, is mixed, compacted and sintered. In this way, a sintered body for valve seat material is manufactured so that it has Cu or Cu alloy powder distributed finely and uniformly in its matrix, and holes of 10 to 25volume% with Pb or Pb alloy infiltrated into them. By this constitution, such a valve seat can be furnished that has heat resistance, wear resistance at high temperature, and does not cause remarkable wear of a valve.

Description

[Detailed description of the invention] [Purpose of the invention]

(Field of Industrial Application) The present invention relates to a valve seat that is used as a companion material to a valve in an engine valve mechanism, and more specifically, to a valve seat that has excellent heat resistance and high-temperature wear resistance. The present invention relates to a heat-resistant and wear-resistant valve seat that exhibits excellent compatibility and is less aggressive to mating valves. (Prior Art) In recent years, with the demand for high output, high rotation speed, fuel efficiency, and exhaust gas countermeasures for automobile engines, attention has been paid to the wear and tear of engine valve train components, especially valves and valve seats. are now exposed to more severe conditions than before, due in part to higher engine exhaust temperatures. Conventionally, valve seats for automobile engines have been made of ferrous sintered alloys and heat-resistant steel. Cast iron is used as the material, but in order to increase wear resistance especially at high temperatures, alloying elements such as chromium, cobalt, molybdenum, and nickel are added, or iron-based sintered alloys are infiltrated with lead. For example, JP-A-57-108246, JP-A-62-211355, and JP-A-63-10914.
Publication No. 2, JP-A-63-203754, JP-A-6
Some of them are disclosed in Publication No. 3-290249. (Problem to be solved by the invention) However, in such conventional valve seats, alloying elements are further added to improve wear resistance at higher temperatures than before, such as composite carbide or composite carbide. If the amount of intermetallic compounds is increased excessively, there will be a problem that the wear of the valve seat, which is the mating material, will increase.In addition, in iron-based sintered alloys that have been infiltrated with lead, the surface temperature of the valve seat will increase. If the temperature exceeds about 300℃, cracks may appear inside and on the seat due to lead expansion, and infiltrated lead may escape, significantly reducing wear resistance and causing significant wear on the valve seat itself. was there. Therefore, in order to maintain heat resistance and wear resistance under high-temperature combustion, copper or copper alloys are infiltrated instead of lead, or copper or copper alloys are infiltrated during compaction. Mix the powder and sinter it, lII! # Valve seats with improved heat resistance and high-temperature wear resistance have been developed, but copper segregation may occur in the infiltration or mixed powder-sintering manufacturing methods, and copper or copper alloys cannot be uniformly coated. Considering that it is difficult to disperse finely and the environment in which valve seats are used becomes harsher, there is still room for improvement in heat resistance and high-temperature wear resistance. (Object of the Invention) The present invention has been made in view of the above-mentioned conventional problems, and provides a valve seat for automobile engines, particularly high-performance engines, which has the heat resistance and high-temperature wear resistance required. The purpose of this product is to provide a valve seat that does not significantly increase the wear of the mating material, the valve.

[Structure of the invention]

(Means for Solving the Problems) The valve seat according to the present invention has a Cu content of 5 to 30% in gi ratio in all or part of one or more raw material powders.
Alternatively, a Cu alloy coating is applied and the weight ratio is C; 0.4 to 3.0%, any one of MO and W.
Seed or 2,l! ．． 5-25%, any one or two of Co and Ni; 0.5-20%, St; 0.
1-0.9%, P; 0.1x0.8%, Cr; 2-1
It is made by mixing, molding, and sintering a powder containing 5% to 30% Cu, and the balance consisting of Fe and impurities, and Cu or Cu alloy is finely and uniformly dispersed in the matrix. The valve seat is characterized by having a structure in which Pb or a Pb alloy is infiltrated into the pores of a sintered body having a porosity of 10 to 25% by volume. This is a means to solve the conventional problems. The present inventors have discovered that fine carbides are dispersed in the matrix of the valve seat, and that carbon dioxide is present in this matrix.
It has a structure in which U or Cu alloy is finely and uniformly dispersed, and the self-lubricating properties of Pb or Pb alloy infiltrated into the pores provide excellent heat resistance, high-temperature wear resistance, and conformability. I got some knowledge. The present invention was made based on such unprecedented knowledge, and firstly, l,? ! Alternatively, by using two or more types of raw material powders coated with Cu or Cu alloy on all or a part thereof, Cu or Cu alloy is finely mixed into the matrix by mixing the powder, forming it, and sintering it. Cu is dispersed uniformly to improve thermal conductivity, heat resistance, high-temperature wear resistance, and conformability. Moreover, a part of Cu dissolves in the matrix and strengthens the matrix, making it resistant to high-temperature performance. This increases the strength of the valve seat and suppresses the decrease in strength due to expansion and melting of Pb or Pb alloy at high temperatures. In addition, during the sintering process, the surface of the raw material powder is coated with Cu or Cu alloy, so
This suppresses agglomeration of carbides and enables uniform dispersion of carbides. Furthermore, by improving the wettability of Fe and Pb with Cu, the lubricating effect of Pb or Pb alloy infiltration is improved, resulting in excellent wear resistance even during low speed rotation, that is, at low temperatures (150 to 250 degrees Celsius). It has been found to have excellent wear resistance over a wide range of temperatures from high to low temperatures, and exhibits particularly excellent performance when used as a valve seat in an engine that uses lead-free Ganlin. did. Next, we will discuss the effects of each component element of the valve sheet according to the present invention, and the reasons for limiting the composition (wt%) and porosity. C;O. , a ~ 3.0% C improves wear resistance by combining with carbide-form elements such as Mo, W, and Cr in the components to form carbides, and the rest is in the matrix. It has the effect of providing high hardness and strength when dissolved in solid solution, but 0.4%
If the content is less than 3.0%, the effect will not be so noticeable, and if it exceeds 3.0%, the amount of carbide precipitated will increase and become coarse, which will not only embrittle the alloy but also damage the mating member. It was set at 4 to 3.0%. Any one or two of Mn and W; 5 to 25
% MO and W, along with Fe and Cr in the components, form double carbides and provide wear resistance, and some of them are dissolved in the matrix to strengthen the matrix and have temper hardening ability. Therefore, they are selectively included, but if the total content is less than 5%, the desired effect cannot be obtained, and even if the total content is more than 25%, the improvement will be even greater considering the increase in cost. Since no effect was observed, it was set at 5-25%. Any one or two of Co and Ni; 0.5
~20% Co and Ni are selectively included in order to further strengthen the matrix and further improve heat resistance and conformability, but if the total content is less than 0.5%, the desired addition is not possible. No effect was observed, and even if the total content exceeded 20%, there was no effect of improving properties despite the increase in cost, so it was set at 0.5 to 20%. St; 0.1 to 0.9% Si is not preferable because if it is added in an amount less than 0.1%, the deoxidizing effect will be small, the oxygen content in the powder will increase, and the sinterability will decrease. If it exceeds 0.6%, the deoxidizing effect will be small and the deoxidizing property will only decrease, so the content should be reduced to 0.61~
It was set at 0.9%. P; 0.1 to 0.8% P forms a low melting point liquid phase of iron-based alloy powder, and is important in promoting liquid phase sintering by low-temperature activation, and some of it precipitates as a hard phase. Although it is effective in improving wear resistance,
If it is less than 0.1%, the effect will be small, and if it exceeds 0.8%, the liquid phase will be excessive, forming a network of liquid phases, embrittling the sintered alloy, and worsening the dimensional accuracy of sintered parts. Therefore, its content was limited to 0.1-0.8%. Cr; 2 to 15% Cr forms double carbides together with Mo, W, etc., and improves wear resistance. At the same time, it dissolves in solid solution in the matrix, enhances the quenching and tempering effect, and further increases the corrosion resistance of the matrix. If it is less than 2%, the effect will be small, and if it is contained more than 15%, not only will there be no further improvement,
Since it reduces the mechanical strength of the sintered body, its content was limited to 2 to 15%. Cu or Cu alloy to be coated; 5 to 30% Cu or Cu alloy coated on all or part of one or more raw material powders is coated with Cu or Cu alloy after mixing, molding, and sintering of the raw material powders. The remaining part is dissolved in solid solution in the matrix to strengthen the matrix, and the remaining part is uniformly dispersed in the matrix, improving thermal conductivity, reducing heat load, and increasing thermal properties.At the same time, during combustion operation of the engine, An oxide film is formed on the surface, which acts as a lubricant and improves wear resistance. And Cu or C
If the amount of U alloy coating is less than 5%, the effect will be small, and if it exceeds 30%, the strength of the sintered body will decrease, so the amount of coating on the raw material powder was set to 5 to 30%. In the present invention, as a method for adding Cu or Cu alloy, in order to finely and uniformly disperse Cu or Cu alloy in the matrix, all or a part of the raw material powder is coated with Cu or Cu alloy, and mixed. It takes the process of powder, shape, and sintering. The coating in this case is performed, for example, by a chemical or electrochemical method, and the form of the coating is determined by mixing the raw material powder in consideration of finely and uniformly dispersing Cu or Cu alloy in the matrix of the sintered body. It is preferable to partially coat the raw material powder than to coat almost completely with Cu or Cu alloy, and it is also economically advantageous. The above-mentioned Cu alloys include well-known cu-Zn alloys, Cu-Co alloys, etc., which have excellent corrosion resistance. Cu-
It is desirable to use Cr alloy, Cu-Sn alloy, Cu-Ni alloy, etc. Porosity of sintered body: 10 to 25% by volume If the porosity of the sintered body is less than 10% by volume, the amount of open bores is too small to sufficiently melt Pb or Pb alloy, which has excellent lubricity. However, when the porosity exceeds 25% by volume, the strength decreases significantly and the abrasion resistance also deteriorates. The porosity of the aggregate was limited to 10 to 25% by volume. Pb or Pb alloy infiltrated into the pores: In the Pb or Pb alloy infiltrated into the pores of the sintered body, Pb-Sn alloy and Pb-In alloy, both of which have excellent lubricity, are used as the Pb alloy. It is desirable to use alloys such as Pb-Sb alloys. (Function of the invention) The valve seat according to the present invention has the above-described structure, in which fine carbides are dispersed in the matrix of the valve seat, and Cu or Cu alloy is finely dispersed in the matrix. It has a uniformly dispersed structure and the self-lubricating properties of Pb or Pb alloy infiltrated into the pores provide excellent thermal properties, wear resistance, and conformability. (Example) Next, an example of a valve seat according to the present invention will be explained in detail while comparing it with a comparative example. -10 as raw material powder
Several types of 0 mesh Fe-Cr-Mo-W-St-C atomized alloy powder and -325 mesh Fe
- Mo alloy powder or pure MO powder, Fe-W alloy powder or pure W powder and Fe-Cr alloy powder, -1250 mesh Fe-26% P alloy powder, -100
Prepare mesh CO powder, -200 mesh Ni powder, -250 mesh Pb powder, -250 mesh Pb-Sn alloy powder, etc., and first convert these raw material powders to N0.1 in Table 1. They were mixed to give the composition set shown in ~5 and mixed for 30 minutes using a V-type mixer. All or part of the raw material powder was coated with Cu at the ratio of the raw material powder to be coated shown in Table 1, 0.5% by weight of higher fatty acid was added, and the mixture was mixed again using a V-type mixer. At this time, the Cu coating was performed such that the amount of Cu in the coating was 10 to 20% by weight. Next, each of the obtained mixed powders was shaped into a bulb seat-shaped compact at a pressure of 7 tonf/cm2, and sintered by holding it at a temperature of 1080 to 1200°C for 60 minutes in an ammonia decomposition gas. By subsequently performing quenching and tempering treatment, a sintered body having the composition shown in Table 2 was obtained. Then, the obtained sintered body was treated with P, which is an infiltrant shown in Table 2.
The valve seat of the embodiment of the present invention is produced by immersing the sintered body in a bath containing melted Pb or Pb alloy at around 500°C, infiltrating the pores of the sintered body with Pb or Pb alloy under high pressure, and then machining it. N0. I got a score of 1-5. (Comparative example) For comparison, the valve seat No. of the comparative example shown in Table 3 is shown in Table 3.
, 1 to 5 were prepared. Among these, Comparative Example No.
In Nos. 1 to 3, Cu was added by mixing Cu powder. It is manufactured by infiltrating sintered vkPb, and as shown in Table 3, it is a valve seat having the same composition as the valve seats of Examples No. 0.1 to 3 shown in Table 1. (However, in Comparative Example No. 3, Cu
Does not include. ). Moreover, comparative example No. 4 and N0.
5 is a commonly used type of valve seat infiltrated with Pb and a valve seat made of JIS heat-resistant steel SUH4. (Evaluation Test Example) Next, using a valve-valve seat unit testing machine as shown in FIG.
1 to 5 and Comparative Example No. A wear test was conducted for each valve seat No. 1 to No. 5. In this valve-valve seat unit test Ia1, the valve 3, which is moved up and down by the rotating cam 2, repeatedly hits the valve seat 5 with impact by the spring 4. The valve 3 is heated by a gas burner 6, and air is blown in the direction of the arrow from an air nozzle 8 attached to a head 7. At this time, by controlling the amount of propane gas supplied to the burner 6 and the amount of air blown from the nozzle 8, the temperature of the valve 3 and the temperature of the valve seat 5 are kept constant, and the temperature of the intake valve seat is kept constant. Tests were conducted under the conditions shown in Table 4, which determined the operating environment, and the amount of wear was determined from changes in the shape of the contact surfaces of valve seat 5 and valve 3. Table 4 The results of this wear test are shown in Figure 2. As is clear from FIG. 2, the valve seat No. 0.1.2 of the comparative example had almost the same composition as the valve seat No. 0.1.2 of the example of the present invention, and Cu powder was added as a mixed powder.
In this case, the amount of wear at a seat temperature of 400°C is larger than that of Valp Sea}N0.1.2 of the example of the present invention at the same temperature, and at a low seat temperature of 250°C, C
It was observed that because u was not uniformly dispersed, hard carbides agglomerated and the wear resistance was insufficient. In addition, the comparative example Valpsi}N0.3 has a small amount of C and a small amount of carbide, so it shows excellent wear resistance at a seat temperature of 250°C, but the wear resistance deteriorates markedly at a seat temperature of 400°C. was recognized. Furthermore, the comparative example Valpsi H (0.4.5 made of conventional material) was inferior in wear resistance at a valve seat temperature of 400°C, and among these, the comparative example Valpsi H (N0.4) had cracks on the surface. Compared to this, valve seat No. 0 of the embodiment of the present invention.
Nos. 1 to 3 had excellent wear resistance from low temperatures (sheet temperature 250°C) to high temperatures (sheet temperature 400°C), and the effect of uniformly dispersing Cu was recognized. and,
The amount of wear of the valve seat of the example of the present invention is that of the valve seat with a large amount of dispersed carbide (valve seat of the example) N0.4.
5), the amount of wear at low temperatures (seat temperature of 250°C) is slightly greater, but the amount of wear at high temperatures is considerably less, compared to the valve seat of the comparative example made of conventional material}N0. ．． 4
．． It was observed that the high temperature wear resistance was significantly improved compared to No. 5.

【Effect of the invention】

The valve seat according to the present invention is manufactured by using mixed powder, T& shape, etc., using one or more raw material powders, all or part of which is coated with Cu or Cu alloy. The base material is a sintered body in which Cu or Cu alloy is uniformly and finely dispersed in the matrix to suppress the agglomeration of carbides, and the pores of the sintered body are It is infiltrated with Pb or Pb alloy.
b1 etc. have excellent heat resistance, and their wear resistance at high temperatures is also significantly improved compared to conventional ones, and they are also less aggressive to mating valves. It has excellent properties, and has the remarkable effect of being applicable as an engine valve seat that can withstand particularly harsh conditions.

[Brief explanation of drawings]

Claims (1)

[Claims] (1) Coating of Cu or Cu alloy of 5 to 30% by weight is applied to all or part of one or more raw material powders, and C: 0.4 to 3.0% by weight; M
Any one or two of o and W; 5 to 25%
, any one or two of Co and Ni; 0.
5-20%, Si; 0.1-0.9%, P; 0.1-0
．． 8% of Cr, 2 to 15% of Cu, and 5 to 30% of Cu, with the balance consisting of Fe and impurities. Finely and uniformly dispersed and 10
Pb is added to the pores of the sintered body having a porosity of ~25% by volume.
Or a valve seat characterized by being made by infiltrating a Pb alloy.