JPS5877115A - Manufacture of valve seat - Google Patents

Abstract

PURPOSE:To form an oxidized film in a short time on a touching valve surface, by heating and simultaneously applying oxidation treatment to the touching valve surface of a valve seat used for an L, P G, engine and the like. CONSTITUTION:A valve seat 1 is fixed to a jig 4, and a valve adapted surface 2 of the valve seat 1 is heated by a heating means 5, then heating steam 6 at high temperature is jetted to the attaching valve surface to rapidly apply oxidation treatment. A high-frequency heating coil 5 is used as the heating means. In this way, only the attaching valve surface, required for oxidation treatment, can be rapidly heated, and an oxidation speed can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a knob seat made of a sintered alloy for internal combustion engines, particularly for high lead gasoline engines and L. P. G. It is suitable for nodal sheets that require special abrasion resistance, such as those used in engines.

Sintered alloys are widely used as heat-resistant and wear-resistant nozzle sheets, mainly in gasoline engines, but their wear resistance is largely due to the presence of pores unique to sintered alloys. That is, the pores and base structure existing in the sintered alloy are formed with an oxide film of (Fe3 04 ) by high-temperature combustion gas during engine operation, and this oxide film improves hardness and surface strength. In addition to this, the density of the surface is improved by reducing the amount of pores due to the expansion caused by oxidation, and the wear resistance against sliding and knocking wear is improved.

On the other hand, L, P, and G. In engines that use special fuels such as engines and hydrogen engines, the oxide film that is formed in conventional engines does not form, and high lead gasoline engines and E. G. R.

Corrosive wear of valve seats is a problem in engines that produce corrosive combustion gases, such as engines.

The most widely used anti-wear treatment for such wear is impregnation with lead or lead alloys, but lead and lead alloys are harmful to the manufacturing environment and are difficult to use. In contrast, sulfurizing, nitriding, and steam treatments are used to form a wear-resistant compound layer made of sulfide, nitride, and oxide compounds on the valve seat surface, but these relatively low-temperature heat treatments In this case, the valve seat softens due to heating, and falling off from the cylinder head due to softening is a major problem, especially in the case of sintered alloys having relatively low strength. In general, sintered alloys with low thermal conductivity due to the presence of sintered pores are sometimes subjected to infiltration treatment with copper or copper alloy to improve thermal conductivity. Since the treatment is carried out in a cyclic atmosphere, the oxide film is reduced and becomes useless.On the other hand, when oxidation treatment is performed after infiltration, the surface processing method per pulp of the valve seat usually takes about one fight. In a valve seat that is sealed by infiltration treatment and has a difficult compound layer depth, it is necessary to form an extremely deep compound layer, which not only increases the processing time but also causes the base structure to become brittle, making it difficult to put it into practical use.

The present invention is excellent in both wear resistance and strength, which are issues with the above-mentioned valve seats, and is particularly suitable for LPG.
The purpose is to obtain a valve seat suitable for engines and high-lead gasoline engines, and will be explained in detail below.

First, the gist of the present invention resides in a manufacturing method in which the pulp contacting surface of a valve seat is heated and simultaneously subjected to oxidation treatment.

That is, as shown in the embodiment diagram in FIG. 1, the valve seat 1 is fixed to a jig 4, the pulp contact surface 2 of the valve seat 1 is heated by the heating means 5, and high temperature heated steam 6 is applied to the pulp contact surface. It is ejected into the water and undergoes rapid oxidation treatment. In the embodiment shown in FIG. 1, a high frequency heating coil 5 is used as a heating means to heat the pulp contact surface 2 to a temperature of 450 to 800°C.
Ejects heated steam at 0 to 150°C. According to this manufacturing method, it is possible to rapidly heat only the pulp contact surface that requires oxidation treatment to increase the oxidation rate, and it is possible to form an oxide film on the pulp contact surface in a short time. It is what it is.

Furthermore, since the valve seat 1 is cooled by the jig 4, the temperature of the valve seat does not rise significantly at areas other than the pulp contact surface, and the valve seat is prevented from becoming softened by the oxidation treatment.

In the present invention, it is preferable that the depth of the oxide film from the pulp contact surface is in the range of 061 to 0.51R1IL. That is, if the depth from the pulp contact surface is less than 0.1 mm, the amount of oxidation coating necessary for wear resistance is too small, and
．． If you try to install more than 5 fins, the temperature of the entire valve seat will not only increase and soften, but also if you try to increase the temperature of the pulp contact surface to shorten the processing time and suppress the temperature rise of the valve seat body. However, the oxide film formed on the pulp contact surface becomes brittle, and the depth of the oxide film formed on the pulp contact surface is selected within the range of 0.1 to 0.5 fins. In the case of large valve seats, by setting the high-temperature heating steam temperature to 500°C or higher, the heated water or air can be directly injected onto the pulp contact surface, thereby eliminating the need for a special means for heating the pulp contact surface. It is possible to obtain an oxide film depth within the above range on the pulp contact surface. In this case, this can be achieved either by the large heat capacity of the valve seat body or by providing a forced cooling means in the jig for fixing the valve seat body. In cases where it is impossible to use the jet of high-temperature heated steam itself as a heating means, specifically, when the heated steam temperature exceeds the withstand temperature of the device, or when the valve seat itself If the cooling capacity of the pulp is low, special means for heating the surface per pulp is required. This heating means includes a high-frequency heating means shown in FIG. 1, which is a high-density energy heating means,
A plasma beam, a discharge arc current or a laser beam can be used.

These high-density energy heating means can selectively heat the pulp contact surface to a temperature of 450°C to 800°C in an extremely short period of time, without raising the temperature of the entire valve seat. be.

When heated steam is injected onto this selectively heated pulp contact surface, unlike the conventional steam treatment at a low temperature of about 550°C, the pulp contact surface is oxidized extremely rapidly, resulting in oxidation to the required depth. The layers are formed in a very short time. Further, by providing such a heating means, when heated steam is injected onto the pulp abutting surface, the risk of generation of water droplets due to some of the steam being cooled to the dew point temperature is also prevented.

As described above, in the present invention, by heating and oxidizing the pulp contact surface of the valve seat at the same time, it is possible to form an oxide film on the pulp contact surface in a short time, improving productivity and wear resistance. Not only does it have excellent properties, but it also maintains the strength of the valve seat because it can prevent the valve seat from softening.

The commonly used sintered alloys for valve seats include Cr, Mo, and WV- from the standpoint of heat resistance and wear resistance.

contains elements that have a softening resistance of
゛Preferably, the total amount of Cr, Mo, W, and V is 5 to 1
A ferrous sintered alloy containing 5% by weight is desirable.

In addition, in the present invention, a predetermined oxide film layer can be formed in a relatively short time even on a valve seat that has been subjected to an infiltration treatment; Because it is difficult to obtain an oxide film layer and has high thermal conductivity compared to those without oxidation, it is desirable to specially heat the contact surface of the pulp. Also, after oxidation treatment, expansion due to oxidation and sintered pores However, by processing the valve seat almost completely beforehand and oxidizing it, the oxidation treatment of the valve seat improves machinability, and the only post-processing required is surface polishing, which increases productivity. is further improved.

[Brief explanation of the drawing]

No. 1N: Example sectional view showing the manufacturing method of the present invention Explanation of the number ■ = Valve seat 2: Valp contact surface 5: Heating means 6: High temperature heating steam patent applicant Nippon Piston Ring Co., Ltd.

Claims (3)

[Claims] (1) A method for producing a valve seat, characterized in that in the method of forming an oxide film on the surface of a valve seat, the pulp contacting surface of the valve seat is heated and at the same time subjected to an oxidation treatment. (2) Valve seat manufacturing method 0 described in the patent, characterized in that the oxidation treatment is performed by injection of high-temperature heated steam (3) The heating means for the pulp abutting surface may include high frequency heating or i
d. Method 0 for producing a glue sheet characterized by using a high-density heat source of a plasma beam, a discharge arc flow, or a laser beam.