JPH07331399A - Remelting treatment of aluminum-made cylinder head - Google Patents

Abstract

PURPOSE:To execute the remelting treatment in deep depth without largely breaking the molten aluminum shape in a range between ports of an aluminum- made cylinder head with a TIG arc by using argon gas. CONSTITUTION:Before the remelting treatment of the cylinder head 1, plug bodies 6, 7 formed with material having higher m.p. and larger heat capacity than the aluminum are fitted into the ports 8, 9 in the aluminum-made cylinder head 1 to hold the ports to the closed condition. The range which is needed to reinforce and extended between the ports, is irradiated with the high density thermal energy of the TIG arc by using the argon under this condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for remelting an aluminum cylinder head.

[0002]

2. Description of the Related Art In recent years, a cylinder head made of aluminum has been widely used for the purpose of reducing the weight of a high-power engine, for example, a high-power diesel engine. When an aluminum cylinder head is used under a high heat load, cracking due to thermal fatigue becomes a problem.

In order to solve this problem, a method of refining aluminum crystal grains by applying remelting treatment to a portion subjected to a high heat load is adopted.

The remelting process is performed as shown in FIG.
After the foundry sand is dropped from the surface of the cast aluminum cylinder head (1) and the weir at the sprue is cut, a portion that receives a high heat load during operation, for example, an intake port in which a valve seat ring (5) is fitted ( The narrow reinforcement area (4) between 2) and the exhaust port (3) is irradiated with a TIG arc (using argon gas or the like as a shield gas) to re-melt the aluminum in this part to make crystal grains fine. This is a treatment method for preventing the occurrence of cracks due to thermal fatigue.

[0005]

Cylinder head (1)
As a means to increase the strength of
As shown in (A), the moving speed of the TIG arc traveling between the arc irradiation start points A and C and the arc irradiation end points B and C is reduced, or the current value is increased to increase the required area (4 ) Is known to increase the density of the thermal energy applied to. By irradiating with high-density heat energy, the remelting depth of the reinforced region (4) increases, and a refined layer of crystal grains having a desired depth dimension is formed. When high-density heat energy is applied for the purpose of increasing the melting depth, the amount of melting deformation of aluminum increases as shown in FIG.
And the required shape of the reinforced area, which is indicated by the two-dot chain line, that is, the remelting processing area (4) is lost. In this case, the surface of the remelting treatment region (4) has relatively large irregularities, and the shape of the work is largely destroyed. Therefore, it is necessary to take a large cutting allowance in the finishing step by the subsequent machining. As a result, not only it becomes difficult to secure the necessary remelting depth, but also the cost increases in terms of both material cost and processing cost. In order to solve this problem, a remelting treatment method using helium gas that can obtain a deeper remelting depth instead of argon has been proposed, but either method was adopted because helium gas itself is expensive. Even in this case, a significant cost increase cannot be avoided.

[0006]

As a means for solving the above problems, the present invention is formed in a port of an aluminum cylinder head from a material having a melting point higher than that of aluminum prior to the remelting treatment of the cylinder head. Re-melting treatment of an aluminum cylinder head, characterized in that the port is kept in a closed state by fitting a plug body, and then a high-strength heat energy is applied to a reinforced region extending between the ports. It provides a method. The material of the plug used as the port sealing member is preferably iron or ceramic having a large heat capacity.

[0007]

Function: Focusing on the fact that a higher density of heat energy can be applied if the molten aluminum does not drastically deform, the heat energy is applied to the port where the molten aluminum is expected to flow. Prior to the above, a plug made of a material having a melting point higher than that of aluminum was fitted, and this plug was used as a sealing member at the open end of the port while irradiating high-density heat energy to the area to be reinforced between the ports. As a result, a remelted portion having a predetermined depth is formed. Since the stopper functions as a weir, the sagging deformation of the molten aluminum is prevented. When iron or the like having a large heat capacity is used as the material of the plug body, the aluminum crystal grains are further refined by the so-called chilling effect.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific example in which the present invention is applied to a cylinder head (1) of a high power diesel engine will be described below with reference to FIG. In the following description, the same components as those of FIG. 2 showing the prior art are indicated by the same reference numerals or reference symbols in principle, and the description of the overlapping matters will be omitted.

In the open end (8) of the intake port (2) of the aluminum cylinder head (1), the melting point is higher than that of aluminum and the heat capacity is relatively large, prior to the start of the remelting process by the TIG arc, And, a frustoconical plug (6) made of a material to which molten aluminum is hard to adhere, for example, iron or ceramics is fitted and the opening end (8) is sealed. Further, a similar frustoconical plug body (7) is fitted in the opening end (9) of the exhaust port (2) to seal the opening end (9).

After that, a TIG arc is radiated to the reinforcing area (4) extending between the intake port (2) and the exhaust port (3) to melt the molten aluminum into the intake port (2) and the exhaust port (3). By remelting aluminum to a predetermined depth while blocking the inflow of (3), a larger remelting depth is secured in the reinforced region (4) and the crystal grains are further refined.

When the iron stoppers (6) and (7) are used, a proper cooling medium passage can be easily formed in the stoppers (6) and (7), and the reinforced region (forcibly cooled) is required. The refinement of crystal grains in 4) is further promoted.

In the present invention, in the remelting process by the TIG arc, since the large deformation between the ports due to the flow of the molten aluminum is prevented by the plugs (6) and (7), air is used to raise the temperature of the aluminum base material. It can be satisfactorily processed even with a cheap and inexpensive TIG arc using argon. Further, it is needless to say that other energy irradiation means such as a plasma jet torch can be adopted as the high density energy.

[0013]

As described above, according to the present invention, since the plug is fitted in the port when the re-melting process is performed between the ports of the aluminum cylinder head, for example, the TIG arc using argon gas causes a large depth between the ports. The shape of molten aluminum will not be greatly deformed even if re-melted, so the cutting allowance for finishing can be kept small, and the refining effect of the plug will further refine the aluminum crystal grains. Along with the increase in the depth of the remelting treatment, a significant increase in the strength of the interport region is achieved.

Further, since the shape of the molten aluminum is not greatly deteriorated, the remelting process can be performed without worrying about the temperature rise of the base material, and the generation of defective products due to the incomplete remelting process can be prevented.

Further, since the reinforcing effect is excellent, it becomes possible to adopt an aluminum cylinder head in a large-sized engine or a high-power diesel engine which receives a higher heat load.

[Brief description of drawings]

FIG. 1A is a plan view of an aluminum cylinder head for a high-power diesel engine showing a specific example of the present invention;
(B) is a cross-sectional view of the intake port and the exhaust port portion taken along the line I-I in FIG. 1 (A).

2A is a plan view of an aluminum cylinder head showing a conventional example of remelting treatment, and FIG. 2B is a line of FIG. 2A.
II-II is a cross-sectional view of the intake port and the exhaust port portion along line II-II, (C) is a block diagram illustrating a manufacturing process of the aluminum cylinder head.

[Explanation of symbols]

 1 Aluminum Cylinder Head 2 Intake Port 3 Exhaust Port 4 Reinforcement Required Area (Remelting Treatment Area) 6 Plug 7 Plug

Claims (1)

[Claims] 1. A port is hermetically sealed by fitting a plug body made of a material having a melting point higher than that of aluminum into the port of the aluminum cylinder head prior to the remelting process of the cylinder head. A method for remelting a cylinder head made of aluminum, which is characterized by holding and then irradiating high-strength heat energy to a reinforced region extending between the ports.