JPS6119809B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a welded valve used in engines such as automobiles. The umbrella part of this type of valve has a temperature of 400 to 600℃ on the suction side.
The exhaust side reaches a high temperature of 700 to 900°C, and the valve seat in particular requires wear resistance and heat resistance against constant hammering and rotation, so austenitic heat-resistant steel is used, and it is hardened, tempered, or solution-treated followed by aging treatment. This provides the necessary hardness. When used in engines that require particularly severe conditions, stellite or Ni-
It is also sometimes coated with metal such as Co alloy. On the other hand, the shaft end of this type of valve normally contacts the tip of the hardened rocker arm adjusting screw or push rod at a frequency of 1/2 of the engine rotation to open the valve against the engine valve spring. Therefore, not only wear due to simple point contact but also complex scratching wear may occur depending on the engine mechanism. Generally, SUH ₃ (C0.35, Cr12.0,
Mo1.0, Si2.0), SUH11 (C0.45, Cr8.0, Si1・
Martensitic heat-resistant steel such as 5) is used, but this type of heat-resistant steel lacks wear resistance.
It has not been possible to sufficiently respond to the recent improvements in engine performance, and as a result, the frequency of stellite overlay on the shaft end is increasing. However, applying stellite to the end of the shaft requires a high degree of skill, and pinholes may occur.
There are disadvantages such as high costs due to post-processing problems and poor mass productivity. In view of the above, the purpose of the present invention is to provide a welded valve with a shaft portion that is excellent in mass production and functionally has a wear resistance comparable to that of a valve with stellite overlay. Japan Industrial Standards symbol SKD11, which has a hardness of at least Hv500 or more in the range, contains carbide M ₇ C ₃ at 10% by volume or more in the quenched state, and has high wear resistance.
An alloy tool steel _represented by
Contains 10% by volume or more of mixed carbide consisting of MC,
It also has a shaft made of high-speed tool steel with the same symbol SKH9, which has high wear resistance; and a cap made of austenitic heat-resistant steel with the same symbol SUH38, which is welded to the shaft. It is something. Hereinafter, one embodiment of the present invention will be explained with reference to the drawings. Fig. 1 shows a welded valve of the present invention, where A is a shaft made of alloy tool steel represented by the Japanese Industrial Standard symbol SKH9, and B is the same symbol SUH38. The cap is made of austenitic heat-resistant steel represented by , and is welded to the shaft part A, C is the face part filler part made of Stellite No. 6, and D, E and F are H _R C58, 50 and H R C58, 50 and 50, respectively, by induction hardening. 40
The hardened parts are shown respectively. The shaft portion A may be formed of high-speed steel represented by the same symbol SKD11. Figure 2 shows a conventional welded valve, where B and C are the cap and face filler parts made of the same material as those in Figure 1, and A' is martensitic heat-resistant steel represented by the same symbol SUH ₃ . The shank portion and G represent the metal filling portion of Stellite No. 1, respectively, and both B and A' were oil-cooled from 1120°C to 750°C and then subjected to aging treatment. Table 1 shows the main chemical components and heat treatment conditions for SKD11 and SKH9, SK3 (carbon tool steel), SUJ2 (bearing steel), SUH3 (martensitic heat-resistant steel), and Stellite No.1 used for the shaft. Table 2 shows the hardness of the various steels shown in Table 1 at room temperature and high temperature. SKH9, which contains 10% by volume or more of carbides M ₆ C and MC in the quenched state, and SKD11, which contains 10% by volume or more of carbides M ₇ C ₃ , have a high-temperature hardness of 500 Hv or more at 300°C, and are ranked No. 1 in Stellite. It is clear that they are comparable. In Table 1, the carbide M ₃ C of SK3 means Fe ₃ C. The carbide M ₃ C of SUJ2 mainly contains Fe ₃ C, in which Cr is substituted for Fe. SKD11
The carbide M ₇ C ₃ is mainly composed of Cr ₇ C ₃ and Fe,
Carbide MC of SKH9, which contains carbides in which Mo and V are substituted with Cr, mainly contains VC with Fe, Cr,
Contains carbides in which W and Mo are substituted with V, and carbides M ₆ C mainly contain Fe ₄ W ₂ C with Cr, Mo,
Contains carbides in which V is replaced with Fe or W. Carbide M ₇ C ₃ of SUH3 is mainly composed of Cr ₇ C ₃ and Fe and Mo.
Contains carbide substituted with Cr. Carbide M ₆ C of Stellite No. 1 mainly contains W ₆ C with Cr replacing W, and carbide M ₇ C ₃ contains:
Contains carbides mainly composed of Cr ₇ C ₃ in which W is substituted for Cr.

【table】

[Table] Next, the shaft part A is listed in Tables 1 and 2 above.
SK3, SUJ2, SKD11, SKH9 and SUH3, while the umbrella part B is made of SUH38 (C0.32, Si0.35,
P0.32, Ni10.5, Cr20.5, Mo1.7, B0.001) and manufactured a welded valve with the same configuration as in Fig. 1, and used it to conduct various tests as described below. I went. First, as a first step, a motoring test was conducted on engines equipped with each welded valve, and only those with excellent durability were further confirmed by a durability bench test. In the motoring test, welded valves using SK3, SUJ2, and SUH3 were found to have some scratch marks, but only the welded valve using SUH3 was kept for comparison as the currently used valve, and this and SKH9,
It was used as a welded valve and test valve using SKD11 for durability bench tests. The valve shown in Figure 2, in which Stellite No. 1 is deposited on the end of the valve shaft, has already been subjected to durability bench tests several dozen times under the same conditions, so this valve is based on past data. was used. Furthermore, in order to confirm the durability of each test valve by firing, an overhead valve engine with a displacement of 1500 c.c. was used at a rotation speed of 5000 r.pm.
A 200 hour high speed durability test was conducted under full load and tappet clearance of 0.15mm, and the results shown in Table 3 were obtained.
The test valves in the table are expressed by the steel type and metallization of the shaft, and each value indicates the amount of wear (mm). In this case, the fuel used was high octane leaded gasoline (lead content: 2.0 g/gallon), which has the property of causing severe wear especially at the end of the shaft.

[Table] Considering the above results, the causes of wear at the end of the valve shaft are not only mechanical as mentioned above, but also combustion products such as gasoline and lubricating oil in the engine. It is also thought that the surface of the shaft end is greatly affected by the generation of frictional heat. In addition, even when using carburized hardened azimuth screws, they tend to wear out due to their compatibility with valves made with Stellite No. 1 metallization, so the valves have excellent tempering resistance and high hardness at high temperatures. A material containing an appropriate amount of composite carbide is more suitable than simple carbide, and as mentioned above, it can be incorporated into the integrated work process compared to stellite metal, so the manufacturing cost is low and it is suitable for mass production. considered suitable. The welded valve of the present invention is manufactured through the following manufacturing process [] or [].

[Table] Shaft terminal Shaft terminal
( ) ( )
Induction hardening Induction hardening

Claims (1)

[Claims] 1. At least in the range from room temperature to 300°C
Alloy tool steel with the Japanese Industrial Standard _symbol SKD11, which has a hardness of Hv500 or more, contains carbides _M7C3 in the quenched state at least 10% by volume, and has high wear resistance, or in the range from room temperature to 300℃. At least Hv500
The same symbol has the same hardness, contains 10% by volume or more of a mixed carbide consisting of carbide M ₆ C and MC in the quenched state, and has high wear resistance.
A welded valve comprising: a shaft made of high-speed tool steel represented by SKH9; and a cap made of austenitic heat-resistant steel represented by the same symbol SUH38, which is welded to the shaft.