JP2648497B2 - Manufacturing method of casting and manufacturing method of cylinder head - Google Patents

Description

The present invention relates to a method for manufacturing a casting such as a cylinder head.

(Prior Art) In recent years, as the output of an engine has increased, the thermal load on the cylinder head of the engine has increased. And the mechanical strength of an aluminum alloy casting cast by a usual method is insufficient.
Further, among the casting methods, the low-pressure casting method with good productivity has a problem that the mold temperature is generally high, so that the casting structure of the cylinder head material becomes coarse and the thermal fatigue strength is poor.

In order to solve these problems, there has been conventionally known a method of improving the material of a cylinder head material by placing a cooling die or a water-cooled die in a portion where thermal fatigue characteristics are required and increasing a cooling rate. . In particular, as a method of strengthening a desired portion, a high-energy beam is applied to a desired portion of a cylinder head as disclosed in JP-A-61-193773, since the method is less restrictive and more effective than the above method. A method of obtaining a chill structure by heating and re-melting has been proposed.

(Problems to be Solved by the Invention) However, according to the latter re-melting method, as shown in FIG. 6, the surrounding molten metal is drawn when the re-melted portion a is solidified, so that the re-melting end portion is melted. There is a problem that the amount is insufficient and crater b is generated in this portion. This crater b
In the case of a cylinder head, this causes a reduction in the compression ratio or the occurrence of abnormal combustion.This problem is particularly encountered in a gasoline engine cylinder head that does not perform surface treatment in the combustion chamber after remelting. Notable.

As a method of suppressing the occurrence of such a problematic crater b, when re-melting using a high-energy beam, a slope mechanism for reducing the arc current near the re-melting end portion, or a method of moving the arc is used. Although methods for increasing the speed are known, the generation of the crater b cannot be fundamentally avoided by these methods.

(Objects of the Invention) In view of the above, the present invention has been made in spite of re-melting a casting material such as a cylinder head by an energy beam.
An object of the present invention is to provide a method of manufacturing a cast product such as a cylinder head in which a crater is not present in the obtained cast product.

(Means for Solving the Problems) In order to achieve the above object, the present invention is to remove an end portion of remelting by an energy beam by processing.

Specifically, a solution taken by the invention of claim 1 is that, after casting a molten metal into a mold to form a casting material, a predetermined portion of the casting material is re-melted by an energy beam, and the re-melting is performed. It is assumed that the melting ends at a portion corresponding to the processing portion, and thereafter, the remelting end portion is processed. In the invention of claim 2, the casting is a cylinder head, and in the invention of claim 3, the processing is drilling.

Further, a solution taken by the invention of claim 4 is a method of casting a cylinder head, comprising: injecting a molten metal into a mold to form a cylinder head material; Was continuously remelted by a high energy beam, and the remelting was terminated at a portion corresponding to the hole processing portion for the plug or the injection nozzle, and thereafter, the hole was formed at the remelting end portion. Things.

(Operation) With the above configuration, in the inventions of claims 1 to 4, the crater generated at the remelting end portion when the casting material such as the cylinder head is remelted by the energy beam performs processing such as hole processing. It is removed by applying.

Embodiment An embodiment of the present invention will be described below with reference to FIGS.

First, a molten metal of an aluminum alloy of JIS standard AC4B is poured into a mold, and a cylinder head material 1 for a gasoline engine as shown in FIG. 1 is formed by a low pressure casting method.

Next, the cylinder head material 1 is placed on the XY table, and the TIG arc 3 which is a high energy beam is
Using a welding machine, the electrode used was pure tungsten having a diameter of 4.8 mm, and the cylinder head material was moved as shown in FIG. 2 while moving the XY table under irradiation conditions in which the argon gas flow rate was 15 / min. Irradiation is applied to a portion requiring thermal fatigue characteristics in 1. As shown in FIG. 3, this irradiation is performed between the intake hole 11 and the exhaust hole 12 in the cylinder head blank 1 and at the opposite end of the hole processing portion 13 for the plug.
Starting from the point, the point B between the intake hole 11 and the exhaust hole 12 and the end of the hole processing portion 13, and the point C near the hole processing portion 13, It is located inside and ends at point D, which is the end of remelting. In this case, A → B → C
→ Over the melting range of D, the arc current value was 300 A, the processing speed was 0.3 m / min, and the resulting crater depth at point D was 3.5 mm.

In this way, as shown in FIG. 4, the re-melted portion is formed in the portion where the thermal fatigue property is required, that is, in the portion between the intake hole 11 and the exhaust hole 12 and in the peripheral portion of the hole 13 for the plug. 14
Then, the cylinder head material 1 is heated to 535 ° C.
, And then cooled with water and heated again to
The T6 treatment is performed while maintaining the temperature at 0 ° C. for 6 hours. further,
After drilling a plug hole 15 in the remelted end portion of the cylinder head blank 1 by machining, ASSY is performed to obtain a cylinder head 2 as shown in FIG.

The high-energy beam is the TIG of the above embodiment.
In addition to the arc 3, a plasma arc, a laser, an electron beam, or the like can be used.
Depending on the type, the remelting end portion may be a hole processing portion for an injection nozzle instead of the above embodiment.

 Hereinafter, a comparative example will be described.

In Comparative Examples 1 to 4, JIS standard A
C4B aluminum alloy is cast at low pressure to form a cylinder head material, and this cylinder head material is formed in the same range as point A → point B → point C in the above embodiment under the same electrode and argon gas flow as above. Irradiated with the TIG arc 3, the irradiation was performed under the following conditions between point A → point B and between point B → point C, and the following crater was obtained at point C.

Comparative Example 1: Between point A and point B: Arc current value 300A Processing speed 0.3m / min Between point B and point C: Arc current value 300A Processing speed 0.3m / min Crater depth: 3.5mm Comparative example 2: Point A → Between points B: Arc current value 300A Processing speed 0.3m / min. Between points B and C: Arc current value 300A → Slope down to 0A Processing speed 0.5m / min Crater depth: 1.7mm Comparative example 3: Point A → Between points B: Arc current value 320A Processing speed 0.3m / min Between points B and C: Arc current value 300A Processing speed 0.5m / min Crater depth: 2.7mm Comparative Example 4: Between points A and B: Arc current Value 280A Working speed 0.3m / min Between point B and point C: Slope down from 100A to 0A arc current Crater depth: 0.8mm As is clear from the results above, in Comparative Examples 1 and 3, the point was larger at point C. Craters occurred, and Comparative Examples 2 and 4
In, a crater still occurred although the depth was shallow because a slope mechanism that gradually reduced the TIG current value was used.
It is not preferable to use the slope mechanism as in Comparative Examples 2 and 4, since the remelting depth in this portion becomes shallow and the effect of the remelting treatment is reduced. On the other hand, if the re-melting end portion is formed in the plug hole processing portion 13 as in the above embodiment, no crater remains on the cylinder head 2 after the plug hole 15 is formed, and the crater is reduced in size. Therefore, it is not necessary to use a slope mechanism, so that it is possible to re-melt the gap between the non-sucking pores and the periphery of the plug hole to a predetermined depth.

(Effects of the Invention) As described above, according to the method for manufacturing a cast product such as a cylinder head according to the invention of claims 1 to 4, the crater generated at the end of remelting of the cast material is processed by hole processing or the like. Because it is removed, there are no craters in the obtained cast product, so it is possible to eliminate various problems due to craters,
In particular, in the case of a cylinder head, it is possible to prevent a reduction in the compression ratio and the occurrence of abnormal combustion.

[Brief description of the drawings]

FIG. 1 is a plan view of a cylinder head material obtained by the manufacturing method of the present invention, FIG. 2 is a perspective view showing a remelting step in the above method, FIG. FIG. 4 is a plan view of the cylinder head material obtained by the re-melting step, FIG. 5 is a plan view of the cylinder head obtained by the above method, and FIG. 6 is an enlarged sectional view of the cylinder head obtained by the conventional method. . 1 ... Cylinder head material, 2 ... Cylinder head, 3
…… TIG arc, 11 …… Intake hole, 12 …… Exhaust hole, 13 ……
Hole processing part, 14: Re-melted part, 15: Hole for plug.

Claims (4)

(57) [Claims] After a molten metal is poured into a mold to form a casting material, a predetermined portion of the casting material is re-melted by an energy beam, and the re-melting is terminated at a portion corresponding to a processing portion. And then processing the remelted end portion. 2. The method according to claim 1, wherein the casting is a cylinder head. 3. The method for manufacturing a cast product according to claim 1, wherein said processing is hole processing. 4. A cylinder head material is formed by injecting a molten metal into a mold, and a portion of the cylinder head material requiring thermal fatigue characteristics is continuously re-melted by a high energy beam. End at a portion corresponding to a hole processing portion for a plug or an injection nozzle, and thereafter, a hole processing is performed on the remelted end portion.