JPS6073032A - Aluminum alloy-made cylinder head casting - Google Patents

Abstract

PURPOSE:To secure such a casting as being excellent in castability and heat fatigue strength, by forming a partial cylinder head from an aluminum alloy- made fusion welding body being heterogeneous with each other. CONSTITUTION:A portion inclusive of a fire contact surface on a cylinder head is made up of a muturally heterogeneous, aluminum alloy-made fusion welding body being formed into such a casting construction as being small in silicon or iron content in a chemical component as compared with other casting parts. With this constitution, a required part alone can be made up into an optional casting composition being excellent in fatigue strength against heat. And, such a casting as being solidified in fusion welding as one body that makes the other part into molten metal formation excellent in inexpensiveness and castability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aluminum alloy cylinder head casting for internal combustion engines having a cast film that is excellent in two-law thermal fatigue.

Aluminum alloy cylinder heads have traditionally been widely used in small high-speed engines, including automobiles, due to their light weight and good cooling performance.

Improving thermal fatigue strength is an issue in the case of high-output engines such as those equipped with a supercharger, an interthaler, or a diesel engine.

By the way, the conventional production of aluminum alloy cylinder heads uses a mold that incorporates a complex core into which the intake/exhaust ports of the combustion chamber and the water cooling jacket are cast. S1 aluminum alloy molten metal (alloys specified by JIS are AC2B, AC4A, etc.)
AC4B, AC4C, etc.) is cast by gravity or pressure, but as shown in Figure 1, in a water-cooled aluminum alloy cylinder head, during high load operation, it is placed within the contact surface 1 shown by diagonal lines. between the intake valve seat 2 and the exhaust valve seat, and between the flow chamber cap 4 and each valve seat, which is additionally added in the case of the taser engine/engine seat 8.
A crack X develops and grows from the surface on the contact side.

There is a danger that water leakage may eventually occur.

Therefore, the inventor developed AI-5i-Cu-Mg-W
rn-based alloy (Si 12% or less, Cu 5% or less, Mg 1%
Hereinafter, for MTlo, 5% or less, Fet 2% or less), a high temperature plastic fatigue test (assuming a constant 250°C, ± 1
As a result, Table 1 was obtained, and the following experimental formula was obtained.

Here, N: Constant determined by test conditions Sl: Weight ratio of silicon (CH) Fe: Weight ratio of iron (impurity) (%) Po: Porosity (volume ratio CH) indicating the degree of degassing amount, that is, It has been found that the higher the silicon content and iron content in the components, and the higher the residual porosity due to insufficient degassing in the structure, the shorter the thermal fatigue life.

The present invention was developed based on the results of thermal fatigue research on aluminum alloy cylinder heads in order to eliminate the drawbacks of conventional cylinder heads. An aluminum alloy cylinder head that has less silicon or iron in its chemical components, or has fewer pores (-A cylinder head made of aluminum alloy, which is made of a multi-layer fusion welded body of mutually different aluminum alloys with a cast structure). suggest.

Two aspects of the present invention will be specifically described below.

In the first embodiment shown in FIG. 2, insert the core d seven times into the upper and lower molds e and f of the cylinder head.
~15 molten metal a is injected into the upper and lower molds e and f, and the ignition surface side that forms the combustion chamber is cast.
．． 7%, Mg0.21'%, Fed, 72%
.

A molten metal bath consisting of MnO, 5% or less, and the balance A1 is used in upper and lower molds e.

Inject into the cylinder f to form the cylinder head.

Install this cylinder head into the engine, stop the circulation of coolant to the cylinder head, and run 4200 RPM for 2 minutes.
When the test was carried out by repeating the process of operating at full load, then stopping the engine and injecting cooling water into the cylinder head, the results shown in Table 2 were obtained.

In the second embodiment shown in Table 2 and FIG. 6, the molten metal (
Instead of a), should we pre-contain low S?

Alternatively, a cast piece with extremely low iron content or absorbed gas content is inserted as a molded piece (c) as shown in Figure 4, and this is then filled with the molten metal (b) from the remainder of the main body to form a fusion welded piece. This is an example of what happens when you do this.

Here, the cast piece (c) is shown in Fig. 4 (a), (
As shown in b), it is preferable to use a cast-out intake boat (ri) and exhaust port (5') so that they can be attached and fixed to the core for each port, and the intake and exhaust valve seats are cast in advance. It may be wrapped or inserted. (In case of diesel, the hole for the swirl chamber cap should be
Drill holes as appropriate before or after casting. ) Each of the above embodiments uses gravity casting from above, but pouring from below or pressure casting may also be used.

The cast piece (c) should be easy to fusion weld.

The surface may be coated with a low melting point metal such as zinc plating in advance.

The third embodiment shown in FIG.
So-called low-pressure casting (this is an example of the case where the molten metal is poured from the remaining part of the main body of 7F into the specified cylinder from the conduit (1 day) provided between the 2nd stroke (5) and the lower mold (6). Gently pour the molten metal (a) on the contact surface side onto the tip of the hot water before pouring (b), and immediately pour the molten metal (a) on top of it.
After the molten metal (15) of b) is supplied into the mold and solidified by applying K air pressure (p), the pressurizing force of the molten metal is reduced,
It is shown lowered to a sunny position.

In this case, when feeding the molten metal (a) on the catalytic side, the position of sunlight on the molten metal (6) and the speed of feeding the molten metal into the mold can be adjusted as appropriate.

In the case of Fig. 5, it is the molten metal (a) on the catalytic side.

Molten metals with low Si and low Fe content, such as JIS alloys AC5A and AC7A, which are strong in thermal fatigue life but have poor castability, or simply molten metals with minimal iron content or degassed and fine-grained molten metals, etc. It can be widely used as molten metal for pouring a small amount first.

In the case of the present invention, it is applicable not only to the low pressure casting method as shown in FIG. 5, but also to high pressure die casting.

As described above, in the aluminum alloy cylinder head according to the present invention, only the necessary parts can be made of any casting composition with excellent thermal fatigue strength by making slight changes to conventional equipment, and other parts can be made of any desired casting composition with excellent thermal fatigue strength. This makes it possible to make a rational fusion-welded integral casting with an economical molten metal composition and excellent castability.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the throat of a conventional cylinder, Fig. 2 is a sectional view showing the first embodiment of the present invention, Fig. 6 is a sectional view showing the second embodiment of the invention, Fig. 4a . b is a plan view and a sectional view of the cast piece C of the second embodiment. FIG. 5 is a sectional view showing a sixth embodiment of the present invention. a + b: Molten metal + e, f: Mold Figure 1 Figure 2 Figure 4 Figure 5

Claims (1)

[Claims] (1) A part of the cylinder head including the firing surface has a cast structure that contains less silicon or iron in the chemical components or has fewer pores than other cast parts. An aluminum alloy cylinder head casting characterized by being composed of fusion-welded bodies of mutually different aluminum alloys.