JPS62139912A - Manufacture of intake/exhaust valve - Google Patents

Abstract

PURPOSE:To manufacture an intake/exhaust valve having an excellent pitching resistance where the coating layer will never peel off by roughly molding the intake/exhaust valve with aluminum alloy then applying a coating of heat resistant and abrasion resistant material thereafter applying a high frequency processing. CONSTITUTION:At first an intake/exhaust valve 6 is roughly molded with aluminum alloy then applied with a coating of heat resistant and abrasion resistant material such as Cr steel, Ni-Cr steel, Cr-Ni-Co system alloy, TiN, etc. Then it is heated for 10sec. to 1min. with a high frequency current having the frequency of about 200-600kHz thus manufacturing an intake/exhaust valve.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing an intake and exhaust valve for an engine.

(Prior art) Valves used as engine intake and exhaust valves are required to have heat resistance and wear resistance, so conventionally they were generally manufactured from heat-resistant steel. Since it has problems of poor heat conductivity and relatively heavy weight, various improvement methods have been proposed.

For example, as described in Japanese Unexamined Patent Publication No. 59-128908, as shown in FIG. By coating the valve body with a heat-resistant and wear-resistant material such as Cr-Motr4, heat transfer from the valve head part 2 to the valve stem part 3 is improved, thermal stress is suppressed to a low level, and the heat resistance and wear resistance of the outer peripheral part of the valve are improved. A method has been proposed to increase the thermal strength of the valve as a whole and to make it possible to reduce the weight of the valve.

(Problems to be Solved by the Invention) However, in the conventional intake/exhaust valve using this method, the coating layer 4 on the outer periphery of the valve is formed by thermal spraying or other ordinary coating means, but the coating layer 4 on the inside 5 of the valve and the coating layer 4 The interdiffusion region between the layers was only a very thin layer region.

Further, in the intake/exhaust valve 1 manufactured by the above method, since the material of the valve interior 5 and that of the coating layer 4 are different in terms of thermal properties, the thermal expansion between the valve interior 5 and the valve outer peripheral portion (coating layer) 4 is different. The difference in rates was extremely large. Therefore, when this intake/exhaust valve 1 is used as an intake/exhaust valve for an engine, the inside of the valve 5
The problem is that the coating layer 4 tends to peel off due to shear stress acting between the coating layer 4 and the coating layer 4 or due to thermal expansion and thermal contraction.

In addition, a method has been proposed in which Cr-Mo&Ii7 material is alloyed by surface laser alloying to form a ri layer on the valve base material, but in this method, Cr-Ma
The m material is alloyed with the aluminum alloy material that is the material of the valve base material, forming an alloy coating layer different from the Cr-Mo steel layer, so the Cr-Mo steel has excellent wear resistance and heat resistance. This characteristic is not fully demonstrated. Furthermore, the problem of easy peeling of the coating layer has not been completely solved.

Therefore, the present invention is a method capable of manufacturing an intake/exhaust valve that has good heat resistance and wear resistance, good heat conductivity, sufficient thermal strength, and is lightweight.
Furthermore, there is provided a method for producing an intake and exhaust valve that does not have the problems of easy peeling of the coating layer due to shear stress or easy peeling of the rough shaped material and the coating layer due to thermal expansion, and therefore has excellent pitting resistance. This is what I am trying to do.

(Means for Solving the Problems) In the method of manufacturing an intake and exhaust valve of the present invention, a roughly shaped material approximately in the shape of an intake and exhaust valve is formed from an aluminum alloy, and then Cr-Mo is coated on the outer surface of the roughly shaped material. It is characterized in that it is coated with a heat-resistant and wear-resistant material such as steel or TiN, and then the coated rough shape is subjected to high-frequency heat treatment.

In the method for manufacturing an intake and exhaust valve of the present invention, examples of the heat-resistant and wear-resistant material include Cr steel, Ni-Cr steel, Cr-Ni-C
Various alloys such as o-based alloys can be used, but from the viewpoint of wear resistance, the above-mentioned Cr-M is particularly preferred.

Steel, TiN, etc. are preferred.

The high frequency heat treatment performed in the method of the present invention is, for example, 20
The method involves heating a rough profile coated with a heat-resistant and wear-resistant material for 10 seconds to 1 minute using a high-frequency current having a frequency of 0 kHz to 600 kflz.

(Function) In the method for manufacturing intake and exhaust valves of the present invention, a coating layer is formed on a rough shaped material by a method such as thermal spraying, and then high frequency heating treatment is performed to heat the rough shaped material and the coating layer. interdiffuses at the boundary, and a very thick alloy layer is formed between the rough profile and the rimmed layer. Therefore, the bonding strength between the rough profile and the coating layer is significantly strengthened compared to the case where thermal spraying or the like is simply performed.

In addition, this alloy layer is formed by mutual diffusion of the aluminum alloy that forms the rough shape material and the heat-resistant and wear-resistant material that forms the coating layer, and its coefficient of thermal expansion is approximately between that of the rough shape material and that of aFt. becomes. Therefore, when the intake/exhaust valve is used, this alloy layer acts like a cushion against temperature changes, so that only a small amount of thermal distortion occurs.

(Example) Hereinafter, a method for manufacturing an intake and exhaust valve according to an embodiment of the present invention and characteristics of the obtained intake and exhaust valve will be described with reference to the drawings.

Example In this example, first, an intake and exhaust valve 6 shown in FIG. 1 was manufactured using an aluminum alloy material having the composition shown in Table 1 below.
A rough shaped material 7 was produced. Next, the rough shape material 7 is made of Cr-Mo
Coating steel material by thermal spraying and heating at 400 ktlz for 30 hours.
High-frequency heating treatment was performed under conditions of 2 seconds.

The intake and exhaust valve 6 obtained in this example is hereinafter referred to as intake and exhaust valve C.
It is called.

Comparative Example 1 For comparison, Cr-
There are two types of intake and exhaust valves: an intake and exhaust valve that is simply coated with a thermal spray coating of Chokusaisai (hereinafter referred to as an intake and exhaust valve); B
It is called. ) was created.

The intake and exhaust valves A, B, and C are used as exhaust valves for a similar engine, and this engine is operated at 66.6km using leaded fuel.
A wear test was conducted on the valve face portions 11 of the intake and exhaust valves A, B, and C by operating under the conditions of 00 rpm x 1000 hours. The results are shown in Figure 2. As is clear from this graph, the amount of wear on the valve face portion 11 of the intake/exhaust valve C according to the embodiment of the present invention is much smaller than the amount of wear on the intake/exhaust valves A and B.

Comparative Example 2 The third aluminum alloy material having the composition shown in Table 1 above was used.
Three test pieces 9 as shown in the figure were manufactured. C) Cr2M for each specimen.

Steel material was coated with four shots and subjected to high frequency heat treatment under the same conditions as Example 1 (hereinafter referred to as test piece C), A
) Simply coated with (:r Motliff material by thermal spray coating (hereinafter referred to as test weft) and B) Cr-
Mo6m material with surface leather alloying (hereinafter referred to as
It is called test piece B. ) was created.

A Mori 2 transfer fatigue test was conducted on the test pieces A, B, and C thus prepared at a surface pressure of 600 kgf/m rd. The results are shown in Figure 4. As is clear from this graph, test piece C had a much higher number of repetitions than test pieces A and B until pitching occurred. That is, the test piece C according to the method of the present invention has extremely excellent pitting resistance.

Intake and exhaust valve A revealed in Comparative Examples 1 and 2 above
, B, and C are due to differences in the configuration near the surfaces of the intake/exhaust valves A, B, and C, respectively, as shown in FIG.

That is, the intake and exhaust valves A are made of the rough shaped material 7 and Cr-M.

Since the mutual diffusion region between the coating layer 8 made of steel material, that is, the alloy layer 10 is very thin, the rough profile 7 and the ri layer 8
The bond with is weak. In addition, the intake and exhaust valve B has a coating layer itself of C.
Since it is an alloy of r-Mo steel and aluminum alloy, the characteristics of Cr-Mold's excellent wear resistance and heat resistance cannot be fully demonstrated, and the formed coating layer does not have sufficient durability strength. It cannot be said that the coating layer has a

On the other hand, in the intake and exhaust valve C according to the present invention, between the coating layer 8 having good wear resistance and heat resistance and the rough profile 7,
The aluminum alloy forming the rough profile 7 and the target ff1J
A very thick alloy layer 10 is formed by mutual diffusion of the heat-resistant and wear-resistant material forming W8. This alloy layer 10 strengthens the bond between the covering layer 8 and the rough shaped material 7, and acts as a buffer between the covering layer 8 and the rough shaped material 7, which have different coefficients of thermal expansion.

(Effects of the Invention) According to the method for manufacturing an intake/exhaust valve of the present invention, the aluminum alloy forming the rough shape and the heat-resistant and wear-resistant material forming the coating layer are formed at the boundary between the rough shape and the coating layer by high-frequency heat treatment. and diffuse into each other to form a thick alloy layer. Therefore, the bonding force between the rough shaped material and the ri layer is strengthened. Therefore, the intake and exhaust valves manufactured by the manufacturing method of the present invention, for example,
When used as an exhaust valve for an engine, the problem of peeling of the ri layer due to shear stress acting between the ri layer and the rough profile does not occur. In addition, the coefficient of thermal expansion of this alloy layer is
Since the material is intermediate between the rough profile material and the Fi layer, when the intake and exhaust valve undergoes repeated thermal expansion and contraction, this alloy layer plays the role of a cushion, resulting in only a very small amount of thermal strain. do not have. Therefore, since the thermal strain caused by heating by engine exhaust gas is small, peeling of the coating layer does not occur even in areas with a large thermal history, such as the valve head of an exhaust valve.

Furthermore, the method of manufacturing the intake and exhaust valves of the present invention does not have the problems of the conventional manufacturing method using surface laser alloying.

Furthermore, the manufacturing method of the intake/exhaust valve of the present invention is similar to the conventional method, since it can be formed using a rough aluminum alloy material that is lightweight and has excellent heat conductivity and a coating layer of a heat-resistant and wear-resistant material. The intake and exhaust valves can be made to have good heat resistance and wear resistance as well as conventional ones, good heat conductivity, and relatively light weight.

[Brief explanation of drawings]

Figure 1 is a front view of the intake and exhaust valve of the example (the left half is a sectional view)
, Figure 2 is a graph showing the relationship between intake and exhaust valves A, B, and C and the amount of face wear. Figure 3 is a front view of the test piece used in the example (the left half is a cross-sectional view). Figure 4 is Figure 5 is a graph showing the relationship between test pieces A, B, and C and the number of repetitions until pitching occurs for intake and exhaust valves A and B.
6 is a partially enlarged cross-sectional view showing the vicinity of the surface of each of C and C. FIG. 6 is a cross-sectional view of a conventional intake and exhaust valve. In the figure, 6... Intake/exhaust valve 7... Rough shaped material 8... Covering layer 10... Alloy layer 11... Valve face patent applicant Toyota Motor Corporation 3 drawings 4 drawings 5 drawings

Claims (1)

[Scope of Claims] A roughly shaped material approximately in the shape of an intake/exhaust valve is formed from an aluminum alloy, and then the outer surface of the roughly shaped material is coated with a heat-resistant and wear-resistant material such as Cr-Mo steel or TiN. A method for manufacturing an intake and exhaust valve, characterized by subjecting a rough shaped material to high-frequency heat treatment.