KR900006103B1 - Fe-sintered alloy for valve guide - Google Patents

Abstract

Fe system sintered alloy for valve guide consists of 2.0-5.0 wt.% Cu, 0.1-0.6 wt.% Sn, 0.2-0.8 wt.% P, 1.5-2.5 wt.% C, 2.0-4.0 wt.% Mo, 0.5-1.0 wt.% Mn and the balance Fe with up to 1.0 wt.% inevitable impurities.

Description

Ferrous Sintered Alloy for Valve Guide

1 is a sintered structure of the present invention.

2 is a basic principle diagram of an OKOSHI type wear tester.

3 is a change in the wear amount according to the ring rotation speed of the non-alloyed material and various comparative materials according to the present invention.

The present invention relates to a small alloy for valve guide of an internal combustion engine.

Since the valve guide, which is an engine part, is mounted on the cylinder head of the engine to perform relative sliding action as the valve is opened and closed, firstly, the valve guide itself must have self-lubrication because it must not damage the relative valve stem as well as the wear resistance of the valve guide itself. Second, the exhaust side is in contact with some high temperature and oxidizing atmosphere, so the heat resistance and thermal conductivity should be good. Third, when the engine is assembled, the inner diameter must be finished by reamer after assembly and mounting on the cylinder head. .

However, the valve guide material, which is mainly applied in the past, is usually made of cast iron on the hop side and Ni-Cr-Mo alloy cast iron on the exhaust side where some heat and oxidation resistance is required, but these materials do not have sufficient self-lubricating properties. In addition, defects in cost and mass productivity are exposed, and there is a demand for the development of new materials capable of satisfying all required characteristics.

Therefore, the present invention not only improves the problems of cast iron, but also creates iron base alloys for valve guides that completely compensate for the disadvantages of general sintered materials that have been applied to a limited portion.

The composition of the present invention is as follows.

It is composed of sintered material with excellent heat resistance, self-lubrication, abrasion resistance and machinability. The amount of each constituent element added and its purpose are as follows.

Copper generally plays a role of promoting sintering to improve the strength of the matrix. The high capacity of iron is 8%, but the high capacity decreases as the amount of carbon increases. The addition of 2.0% or more has an effect on the known strength. However, the addition amount of copper is limited to the range of 2.0-5.0% because the effect is small compared to the raw material powder price increase even if it is added more than 5.0%.

Tin also has the same strength enhancement effect as copper but at 0.1% or more. However, since the addition of more than 0.6% inhibits the embrittlement of the material and the stability of the product size, the amount of tin added is limited to 0.1-0.6%.

Phosphorus is added to form a ternary alloy of Fe-P-C to improve wear resistance. However, at less than 2.0%, the amount of alloy phase formed is small, and when added at 0.8% or more, excessive alloy phase is formed and the coating property is significantly impaired. Therefore, the addition amount of phosphorus is limited to 0.2-0,8% of range.

Carbon is dissolved in the matrix to strengthen the matrix and is dispersed in the matrix in the state of free graphite to impart self-lubrication to improve wear resistance.

Therefore, if the amount of glass graphite is less than 1.5%, it is insufficient to give self-lubricating property. If it is added more than 2.5%, the amount of carbon added is 1.5-2.5% because it causes the segregation and weakening of the graphite during powder molding along with the known strength decrease. It is limited to the range of.

Molybdenum is added in the state of molybdenum-iron alloy to attain some known reinforcement, but is mainly added as a dispersing hardener to improve abrasion resistance. If the content is less than 2.0%, the effect is insignificant, and when the amount is added more than 4.0%, the machinability is impaired and the powder formability is deteriorated. Therefore, the amount of molybdenum added is limited to 2.0-4.0%.

Manganese is added in the form of MnS for the purpose of improving machinability, and the amount of manganese is limited in the range of 0.5-1.0% because less than 0.5% of manganese improves machinability. do.

In the manufacturing method of the sintered material to which the sintered alloy of the present invention composed of the above elements is applied, the constituent raw material powders are first mixed to satisfy the required composition, and then molded at a molding pressure of 5-6 ton / cm 2 and sintered at 1000-1100 ° C. Sintering at temperature for 30-60 minutes. At this time, the sintering atmosphere is carburized gas to prevent decarburization.

Next, a characteristic test example relating to the alloy and the comparative material of the present invention will be described.

The composition of the present embodiment and the composition of the comparative material are shown in Table 1 as one example of the range of components defined by the inventor, and the manufacturing conditions were prepared as follows for tensile strength measurement specimens and wear measurement specimens.

Under the conditions of the preparation of the specimen and the comparative material consisting of the composition ratio of Table 1 were prepared and their respective physical properties and mechanical properties were compared in Table 2.

TABLE 1

TABLE 2

As shown in FIG. 1, the sintered structure of the present invention is a white coarse particle, a hard phase, a base phase is a pearlite, and a black part is a pore (some glass graphite).

In order to compare the wear resistance of the present invention with the sintered comparative material and the cast iron comparative material, the wear amount was measured using an Okoshi type abrasion tester, and the result table of FIG. 3 was obtained. .

The abrasion test conditions conducted in the above examples are as follows.

Thus, in the present invention, since the molybdenum-iron alloy powder was added to improve wear resistance and MnS was added to improve the machinability, as shown in Table 2, the hardness and the density decrease due to the slight deterioration of moldability. And although the tensile strength is expected to decrease, but the valve guide is not a component that requires mechanical strength such as hardness and tensile strength, but rather wear and machinability are very important parts of the present invention, the molybdenum-iron alloy powder and MnS It can be utilized as an excellent valve guide material that satisfies such required characteristics by the addition of sintered products. Sintered products are not directly proportional to wear resistance and hardness like general solvent materials. By evenly distributing the characteristics of excellent wear resistance Since the iron base alloy for valve guide according to the present invention has various requirements, that is, lubrication, heat resistance, abrasion resistance, machinability, etc. are greatly improved and mass production is provided, it improves the quality of the valve itself and solves the conventional problems. By doing so, it is possible to improve the quality of the entire vehicle and reduce costs.

Claims (1)

Weight ratio Copper: 2.0-5.0, Tin: 0.1-0.6, Phosphorus: 0.2-0.8, Carbon: 1.5-2.5, Molybdenum: 2.0-4.0, Manganese: 0.5-1.0, Others: 1.0 or less, Iron: Valve guide containing the rest Iron-based small bonds.

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