JPH0344202B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a valve operating member used as a cam follower such as a rocker arm or tappet that constitutes a valve operating system for an internal combustion engine. In general, sliding parts of valve operating members such as rocker arms and tappets that function as driven members of cams are provided with pit materials made of chilled castings or iron-based sintered materials. By the way, in recent years, in response to demands for higher speed, higher output, and higher efficiency for internal combustion engines, engines equipped with superchargers such as turbos, diesel engines, etc. have become popular, and with this, the valve train components mentioned above have become more popular. The usage conditions for pad materials are becoming increasingly strict. For this reason, various research and development efforts have been made to improve the properties of the above-mentioned pad materials.
Although it has become possible to obtain materials with improved pitching properties, the current situation is that problems remain with respect to scuffing resistance, initial conformability, and attackability. The present invention was made in view of the above circumstances, and
It has excellent wear resistance and pitting resistance, and improves scuffing resistance and initial conformability.
It is an object of the present invention to provide a valve train member equipped with a pad material that can reduce the aggressiveness of opponents. As a result of intensive research to achieve the above object, the present inventors discovered that C-Cr-Mn can be used as a pad material.
-Si-P(B)-(Mo, W, Nb, Ti, Zr, Ta,
Using an iron-based powder sintered material made of V, Ni, Co, Cu, Sn)-Fe alloy, a carburized layer is formed on the sliding surface of this sintered body, and a nitrided layer is formed on the surface of this carburized layer.
By forming a nitriding reaction layer, a phosphate film, etc., a pad material with good properties can be obtained.Furthermore, the optimum composition of the alloy has been found, leading to the present invention. The present invention will be explained in detail below. In the valve train member of the first invention, the pad material forming the sliding surface has C: 1.0 to 3.5% by weight;
Cr: 3.0~25.0%, Mn: 0.1~2.0%, Si: 0.3~2.0
%, P: 0.1-1.0% or/and B: 0.01-0.5
%, Mo: 10% or less, W, Nb, Ti, Zr, Hf,
8.0% or less of one or more elements selected from the group consisting of Ta and V, 1.5% or less of impurities, and the above
The pad material is made of a sintered material in which the total amount of Cr, Mo, W, Nb, Ti, Zr, Hf, Ta, and V is 30% or less, and the balance is Fe, and this pad material has a carburized layer on the surface and , a nitrided layer with a thickness of 1 μm or more is formed on the surface layer of this carburized layer. Further, in the valve operating member of the first invention, the valve operating member of the second invention has a surface and a thickness of the pad material.
A phosphate film of 0.5 μm or more is formed. The valve operating member of the present invention has a main body made of a material such as steel or cast iron, and a pad material is provided on the sliding portion that contacts the cam. The main body is made of steel as before to provide sufficient mechanical strength.
This is also to keep the inertial mass small. In addition, the pad material is made by molding iron-based powder sintered material.
It is made by sintering, and a carburized layer is formed on the sliding surface, and the surface of this carburized layer is coated with one or more of a nitrided layer, a nitrided reaction layer, and a phosphate coating layer. layers are formed. This padded material is
It is fixed to the valve operating member body, for example, by brazing with copper solder or by diffusion bonding after sintering. The carburized layer formed on the surface of the pad material prevents the softening of the matrix when a nitrided layer, nitrided reaction layer, phosphate film, etc. are further formed on the surface, and has the effect of ensuring appropriate hardness. do. Additionally, the carburized layer is interposed between the nitrided layer or phosphate coating and the sintered alloy to alleviate extreme changes in hardness between the nitrided layer or phosphate coating and the sintered alloy. This has the effect of maintaining good bonding properties of the nitrided layer and the like to the sintered alloy, thereby preventing the peeling phenomenon of the nitriding layer and the like, as well as improving the durability of the pad material. The carburized layer can be formed by forming the pad material from a sintered alloy and then applying a well-known treatment method such as solid carburizing, liquid carburizing, or expected carburizing. The depth of the carburized layer in this case is on the order of 100 μm. Further, the nitrided layer, nitrided reaction layer, and phosphate film layer greatly improve the initial conformability and pitting resistance of the pad material to the cam, and reduce the aggressiveness of the pad material. These effects are particularly effective when the pad material is used under high surface pressure from the cam. In order for the nitrided layer etc. to fully exhibit the above effects, it is desirable that the thickness is 1 μm or more, and if it is less than 1 μm, sufficient effects may not be obtained. Furthermore, in valve train parts, when the pad material is subjected to high surface pressure by the cam and is used under harsh conditions such as high-speed operation, a nitrided layer is formed on the surface of the carburized layer, and the nitrided layer is further Forming a phosphate film layer on the surface of the material is effective in improving initial conformability, pitting resistance, and reducing aggressiveness. In this case, it is desirable that the nitride layer has a thickness of 1 μm or more, and the phosphate film has a thickness of 0.5 μm or more. The nitrided layer and nitrided reaction layer are formed by forming a carburized layer on the pad material, degreasing it, and then immersing it in a bath containing a mixture of cyanate and carbonate at a temperature of about 550 to 580°C. can be formed by
The thickness of the layer can be determined by adjusting the processing time. In this way, since the nitriding treatment is performed at a temperature equivalent to the tempering treatment, a decrease in hardness occurs in the base material, but in this invention, since the surface layer is carburized in advance, the extent of the decrease is small. Note that the nitrided layer can also be formed by gas soft nitriding treatment or ion nitriding treatment. In addition, for the phosphate film, a carburized layer is formed in the same manner as in the nitriding process, and after degreasing, the film is immersed for about 1 to 10 minutes in a manganese phosphate bath maintained at a bath temperature of 92 to 100°C. can be formed by Next, the composition of the sintered material of the pad material used in the examples of the present invention will be explained. As for the above sintered material, when expressed in weight%, C is
1.0~3.5%, Cr 3.0~25.0%, Mn 0.1~2.0%,
Si 0.3-2.0%, P 0.1-1.0% or/and B
0.01 to 0.5%, Mo 10% or less, W, Nb, Ti,
Contains 8.0% or less of one or more elements selected from the group consisting of Zr, Hf, Ta, and V, and Ni and/or Co.
5.0% or less, Cu and/or Sn 15% or less, and the above-mentioned Cr, Mo, W, Nb, Ti, Zr, Hf, Ta,
The total amount of V and V is 30% or less, the balance is Fe, and other impurities are 1.5% or less. Carbon C dissolves in the matrix, increases the hardness of the matrix and strengthens it, as well as Cr, Mo,
It forms carbides and double carbides with W, Nb, Ti, Zr, Hf, Ta, and V, and has the effect of improving wear resistance. If the content is less than 1.0%, the above effects will not be fully expressed, and if it exceeds 3.5%, the amount of carbides will increase and grow as crystals, which will reduce the toughness of the sintered alloy matrix and cause sliding problems. This is not desirable because the characteristics are significantly reduced and the aggressiveness of the opponent is increased. Cr dissolves in the matrix and strengthens the matrix and improves heat resistance and sliding properties, and carbides and double carbides produced by reaction with C improve wear resistance, scuffing resistance, and initial conformability. It has the effect of causing If the content is less than 3.0%, a sufficient effect cannot be obtained, while if it exceeds 25.0%, the amount of hard carbide produced increases, which deteriorates the sliding properties and increases the aggressiveness of the opponent, which is not preferable. Furthermore, Mn is dissolved in the matrix, strengthens the matrix, improves hardenability, and has the effect of significantly improving wear resistance and sliding properties. Furthermore, during sintering, it functions to improve sinterability and increase density at low temperatures.
If the Mn content is less than 0.1%, the above-mentioned effects cannot be obtained sufficiently, and if it exceeds 2.0%, the aggressiveness toward opponents increases, which is not preferable. Si is added when producing raw material powder and acts as a deoxidizing agent. Also, in the sintered state, it is effective in strengthening the matrix. If the amount of Si added is less than 0.3%, the effect of deoxidizing the raw material powder will be small;
Particularly when the Mn content is high, it is necessary to perform sufficient deoxidation treatment, and it is necessary to add 0.3% or more.
On the other hand, if it exceeds 2.0%, the hardenability during sintering will decrease, making it impossible to obtain a sintered body with sufficient hardness, and the wear resistance will decrease accordingly. Either or both of P and B are added, but both of them form a solid solution in the matrix, increase the activity during sintering, and generate a partial liquid phase at low temperatures during sintering. It has the effect of promoting sintering. If P is less than 0.1% and B is less than 0.01%, sufficient effects cannot be expressed. Also, P is 1.0%, B is 0.5%
If it is added in excess of this amount, the amount of liquid phase generated during sintering becomes excessive, the sintered structure becomes coarse, and the sliding properties deteriorate. In addition, Mo is added as necessary.
It dissolves in solid solution in the matrix, strengthens the matrix, improves hardenability, and has the effect of improving the hardness of the sintered body. Furthermore, the carbides and double carbides produced by the reaction of Mo not only improve the wear resistance but also effectively act to improve the sliding properties. If the amount of Mo added exceeds 10%, the amount of carbides generated during sintering increases, and furthermore, acicular carbides are formed at grain boundaries, making the sintered body brittle, reducing wear resistance, and reducing the Aggression increases, which is undesirable.
Moreover, it also causes an increase in cost, which is not economically preferable. One or more of W, Nb, Ti, Zr, Hf, Ta, and V are selected and added as necessary. These components all react with C and other components to produce fine carbides and double carbides, and these carbides serve to improve wear resistance. If the amount of these components added exceeds 8%, the amount of carbides of these elements generated during sintering becomes excessive.
For this reason, the extremely hard carbide increases the aggressiveness toward others and makes manufacturing difficult, which is undesirable. Furthermore, the above-mentioned components such as Nb and Ti are undesirable because they are expensive and increase the cost. Either or both of Ni and Co may be added as necessary. These components form a solid solution in the matrix, strengthen the matrix, and are particularly effective in improving the toughness, initial conformability, and heat resistance of the sintered body. Even if Ni and/or Co are contained in an amount exceeding 5%, no significant effect can be obtained, and on the contrary, the cost will increase, so it is necessary to suppress the content to 5% or less. Further, one or both of Cu and Sn may be added as necessary. These components form a solid solution in the matrix, and part of them generates a liquid phase during sintering, contributing to stabilization of sintering, as well as having an effective effect on strengthening the matrix and refining carbides. Furthermore, the undissolved portion of Cu and/or Sn has a great effect on improving the initial conformability and sliding properties of the sintered body. When these Cu and sn are contained in an amount exceeding 15%, it is not preferable because it lowers the strength and wear resistance of the sintered body. In addition, the above-mentioned Cr, Mo, W, Nb, Ti, Zr, Hf,
The total amount of Ta and V needs to be 30% or less by weight. If it exceeds 30%, the resulting sintered body becomes more aggressive towards others and has lower toughness, which is not preferable. Furthermore, when sintering the sintered material having the above composition, the density ratio of the obtained sintered body is 87%.
It is desirable to select conditions that satisfy the above conditions. When the density ratio is lower than 87%, wear resistance particularly when used under a high-pressure surface decreases, and a desired nitrided layer may not be obtained during nitriding treatment. Therefore, a pad material that is formed by sintering a sintered material having a specific composition as described above, has a carburized layer on its surface, and has a nitrided layer formed on the surface of this carburized layer. As described in detail, the sintered body that serves as the base has a unique composition that provides wear resistance and toughness, and the nitride layer on the surface of the sintered body also provides pitting resistance and scuffing resistance. , the initial familiarity is further improved, and the aggressiveness of the opponent is reduced. Therefore, the valve train member of the present invention equipped with the above-mentioned pad material has good properties of the above-mentioned sintered body and surface layer, and has wear resistance, toughness, initial conformability, pitting resistance, and scuffing resistance. It has good characteristics as a camouflage, such as high dexterity and low opponent aggression. In particular, by further forming a phosphate film on the surface of the nitrided layer, the soft film deforms and widens the contact surface, which acts to relieve pressure, making the above effects even stronger. Initial familiarity is enhanced. Furthermore, since the nitrided layer, phosphate film, etc. are formed on the surface of the carburized layer formed on the sintered body, the carburized layer can prevent the matrix from softening when forming the surface layer. In addition, the bond between the surface layer and the sintered alloy (matrix) is improved, and therefore, it has the advantage of being excellent in durability as a valve operating member. Next, the present invention will be explained in more detail with reference to Examples. Example Six kinds of powder sintered materials shown below were prepared, and these were mixed with Ni, Co, Cu, Sn, Cu-12%Sn,
C powders were mixed in the proportions shown in the table below (weight% relative to the sintered material), each was molded and sintered as a pad material for a tapepet, and these pad materials were
The tappet body made of SCr420 was soldered using copper solder. Next, the surface of the pad material was carburized to form a nitride layer on the surface, and a phosphate film was further formed on a part of the material to create a tapepet. For comparison, a pad material with a nitride layer and/or phosphate film formed without carburizing was prepared and fixed to a tapepet body made of SCr420 to prepare a comparative tapepet. The above tappet was assembled to the lifter valve of a diesel engine, and using SCM carburized and quenched cam as the cam, it was operated in special degraded oil for 300 hours at a load of 200 kg and a rotational speed of 1500 rpm. The amount of wear was investigated. The results are shown in the table. Γ powder sintered material (weight%) 3.5%Cr/0.5%Mn-1.0%Si-0.5%P-remainder
Fe, 12.0%Cr-0.5%Mn-1.0%Si-0.5%P-balance Fe,

[Table] As shown in the table, the valve train member of the present invention has excellent pitting resistance, and the amount of wear on the cam is extremely small compared to the comparative example, so it has high initial conformability and is less likely to attack opponents. I know it's small.

Claims (1)

[Scope of Claims] 1. A valve train member for an internal combustion engine, in which a pad material forming a sliding surface is provided on a main body of the valve train member, wherein the pad material has a weight percentage of C: 1.0 to 3.5%; Cr: 3.0-25.0%, Mn: 0.1-2.0%, Si: 0.3-2.0%, P: 0.1-1.0% or/and B: 0.01-0.5%, Mo: 10% or less, W, Nb, Ti, Zr , Hf, Ta, and V, containing 8.0% or less of one or more elements selected from the group consisting of V, and 1.5% or less of impurities, and the above-mentioned Cr, Mo, W, Nb, Ti, Zr, Hf, Ta.
The pad material has a carburized layer on its surface, and a nitrided layer with a thickness of 1 μm or more on the surface of this carburized layer. A valve operating member for an internal combustion engine, characterized in that: 2. A valve operating member for an internal combustion engine in which a pad material forming a sliding surface is provided on a valve operating member main body, wherein the pad material has, in weight percent, C: 1.0 to 3.5%, Cr: 3.0 to 25.0%. , Mn: 0.1-2.0%, Si: 0.3-2.0%, P: 0.1-1.0% or/and B: 0.01-0.5%, Mo: 10% or less, W, Nb, Ti, Zr, Hf, Ta, V 8.0% or less of one or more elements selected from the group consisting of 1.5% or less of impurities, and the above-mentioned Cr, Mo, W, Nb, Ti, Zr, Hf, Ta
The pad material has a carburized layer on its surface, and a nitrided layer with a thickness of 1 μm or more on the surface of this carburized layer. A layer with a thickness of 0.5μ is formed on the outer surface of the nitride layer.
A valve train member for an internal combustion engine, characterized in that a phosphate film of m or more is formed.