JPH059505B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to cast iron for Rotsuka arms, and more specifically, it is not only used for unleaded gasoline engines, but also for use in unleaded gasoline engines.
Cast iron for rocker arms is also suitable for use in high-lead gasoline engines, as it has excellent wear resistance and scuffing resistance, and is less likely to damage sliding mating materials. In the engine valve mechanism, the rocker arm that converts the rotational movement of the cam into the vertical movement of the valve must have sufficient mechanical properties to withstand complex stresses such as bending, tension, and compression. Of course, in sliding parts with other parts (cams, valves, etc.), we especially need to improve wear resistance, resistance to scratching and wear, so-called scuffing resistance, as well as to the sliding mating material. There is a need for less damaging properties. By the way, depending on the type of gasoline used,
There is a difference in the above-mentioned sliding wear performance of the Rocker arm, and if the Rocker arm material that has conventionally shown good sliding performance with unleaded gasoline is used with high lead gasoline, significant wear and scuffing may occur. This is because when high-leaded gasoline is used, combustion products unique to high-leaded gasoline that are not generated when unleaded gasoline is burned are produced by combustion of gasoline, and these products are mixed into the lubricating oil. ,
It is thought that this is hindering the sliding performance of the sliding part of the rocker arm. [Object of the Invention] The present invention solves the above-mentioned drawbacks regarding the sliding performance of conventional rocker arm materials.
By adjusting the composition and structure of the cast iron for the Rotsuka arm, we have achieved wear resistance and improved resistance not only when using unleaded gasoline but also when using high lead gasoline.
The object of the present invention is to provide a cast iron for rocker arms that has excellent scuffing resistance and causes less damage to sliding mating materials. [Structure of the Invention] According to the present invention, such an objective is to achieve a weight ratio of C: 1 to 4%, Cr: 1 to 15%, Mo: 1 to 20%.
%, the balance consists essentially of Fe, and the base structure is residual austenite, martensite,
This is achieved by a cast iron for a rock arm, which is characterized by having a single or mixed structure of pearlite or bainite, and having carbide dispersed and crystallized in the matrix structure. By adding C, Cr, and Mo compositions of the present invention in predetermined proportions, carbides are dispersed and crystallized in the base structure, thereby providing excellent wear resistance and scuffing resistance, and excellent sliding properties. Damage to the mating material can be reduced. The reason for limiting C to 1 to 4% is that if it is less than 1%, the wear resistance of the Rotsuka arm itself will be poor, and if it exceeds 4%, there will be no problem with the performance of the Rotsuka arm itself, but it will become more aggressive to the opponent, and the wear resistance of the Rotsuka arm itself will be poor. This is because it causes excessive wear. The reason why Cr is limited to 1-15% is that if it is less than 1%, the wear resistance of the Rocker Arm itself will be poor, and if it exceeds 15%, the carbide will easily fall off, which will not only affect the opponent's attack but also cause excessive wear of the Rocker Arm itself. This is because they will be rejected. The reason for limiting Mo to 1 to 20% is the same as the reason for limiting Mo to Cr: if it is less than 1%, the wear resistance of the rocker arm itself will be poor, and if it exceeds 20%, the carbide will easily fall off, and it will be difficult to attack the opponent. This is because the locking arm itself is subject to excessive wear. In addition, in the present invention, since the base structure is a mixed structure of retained austenite and martensite, it has excellent wear resistance and scuffing resistance, and can cause less damage to the mating material on which it slides. can. In addition, when casting with lost wax, it is manufactured in an as-cast state, so
Part of pearlite or bainite is inevitably formed singly or as a mixed structure. Furthermore, in the present invention, by adding carbides, that is, C, Cr, and Mo in predetermined proportions to the matrix structure, for example, highly hard M ₂₃ C ₆ carbides are dispersed and crystallized, It has excellent wear resistance and scuffing resistance, and can cause less damage to the mating material on which it slides. [Example] Hereinafter, an example of the present invention will be described based on the accompanying drawings. At Lost Wax, the composition shown in the table below was added to the iron, and the rough material of the Rotsuka arm was cast and formed. Incidentally, as the constituent elements for manufacturing the rough arm material, it is sufficient that C, Cr, and Mo are added to iron. However, in this example, since a scrap material in which about 0.1 to 0.8% of Si is inevitably mixed is used as the iron element material, Si is inevitably added as an impurity. As for the casting conditions, as is generally practiced, the molten metal was poured into a lost wax mold and then solidified in an as-cast state. The lost wax mold temperature is 800℃, the tapping temperature is 1500-1700℃, and the casting temperature is
The temperature is 1450-1650℃.

【table】

〔Effect of the invention〕

As is clear from the above, the cast iron for rocker arms according to the present invention has excellent wear resistance and resistance not only when using unleaded gasoline but also when using high lead gasoline by adjusting the composition and cast iron structure. It has the advantage of being excellent in scuffing resistance, causing little damage to the mating material it slides on, and having excellent so-called sliding performance.

[Brief explanation of drawings]

The figure is a graph showing the results of a low-speed motoring test performed by motoring various test materials.

Claims (1)

[Claims] 1 Weight ratio: C: 1-4%, Cr: 1-15%,
Mo: 1 to 20%, the balance substantially consisting of Fe, the base structure is a single or mixed structure of retained austenite, martensite, pearlite or bainite, and carbides are dispersed and crystallized in the base structure. A cast iron for rock arm that is characterized by: