JP3487021B2 - How to locally strengthen aluminum - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for locally strengthening an aluminum material.

[0002]

2. Description of the Related Art As shown in FIG. 9, in an aluminum piston 2 having a combustion chamber 1 formed on an upper surface thereof, a large thermal stress acts on an opening edge (shelf) 3 of the combustion chamber 1, so that a crack 4 is formed. Tends to occur. In order to locally strengthen such an aluminum part, various methods have been proposed for overlaying a metal or the like having excellent heat resistance by arc welding (for example, Japanese Patent Laid-Open No. 62-150014).

[0003]

However, when aluminum and another metal are welded, a brittle intermetallic compound precipitates in the reaction layer between them, and in the conventional strengthening method by build-up welding, the reaction layer is thickly formed. However, there is a problem that the strength is lowered. If the heat-resistant substance is sufficiently diluted with aluminum as a countermeasure against this, the precipitation of intermetallic compounds can be suppressed, but the desired heat-resistant effect cannot be obtained at high temperatures of 400 ° C or higher. It is also possible to reduce the output of arc welding to suppress the reaction between the heat resistant substance and the aluminum base material, but the welding conditions become strict and the welding time is long, so it is not suitable for mass production, and from a cost perspective. It is difficult to achieve industrially.

Therefore, the present invention was devised to provide a method of locally strengthening an aluminum material capable of locally joining a strengthening substance by welding with very little precipitation of intermetallic compounds under industrially feasible welding conditions. It is a thing.

[0005]

According to the present invention, a dissimilar material made of a reinforcing material is placed on an aluminum base material, MIG welding is performed on both sides of the dissimilar material using aluminum wires, and then an aluminum filler material is applied from above the dissimilar material. Is used to perform overlay welding by arc welding. The reinforcing substance is preferably a high melting point heat resistant substance such as Ti.

[0006]

With the above structure, the heat input by the arc of welding is reduced in the dissimilar materials, the reaction with the aluminum base material is suppressed, and a good reaction layer with very little precipitation of metal compounds is firmly bonded.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a method for locally strengthening an aluminum material according to the present invention. First, a Ti rod 12 having a circular cross-section made of titanium, which is a heat-resistant substance, is placed along a portion of a flat plate of an aluminum base material (aluminum casting, aluminum wrought material, etc.) 11 to be strengthened (a). The Ti rod 12 has a diameter corresponding to the target portion (for example, φ
2.4mm) is used. Next, set the welding torch 13 of the MIG welding machine at a position slightly apart from the Ti rod 12,
Overlay welding is performed using the aluminum welding wire 14 (b
~ C). The position of the welding torch 13 is, for example, about 4 mm from the center of the Ti rod 12, and this position is moved in parallel with the Ti rod 12. With this, near the Ti rod 12, the weld overlay 1 with an appropriate penetration depth and height can be obtained.
5 is formed, and the weld overlay 15 and the portion from the side portion to the bottom portion of the Ti rod 12 are joined (d). Further, overlay welding is also performed on the opposite side of the Ti rod 12, and the Ti rod 12 is similarly joined to the aluminum base material 11 by the weld overlay portion 16 (e).

The state of this joining is shown in the cross-sectional photograph of FIG. The welding conditions at this time were 300 A, 20 V output power,
Welding speed is 300 mm / min, shield gas (Ar) flow rate is
25 liters / min, welding wire 14 is A1100, φ1.6mm
I assumed that. Looking at this cross-section photograph, the aluminum base material 11
It can be seen that a reaction layer having a thickness of about 5 μm, which is extremely thin as compared with the conventional bonding method, is formed between the Ti rod 12 and the Ti rod 12, and the bonding is extremely strong. Such a good reaction layer can be obtained because, as shown in FIGS. 1B and 1C, when the MIG welding is performed, the end of the arc 17 is used for welding. It is considered that the heat input to the Ti rod 12 itself is small and only a very small portion of the surface thereof is melted, and that this surface and the molten pool 18 formed by the welding wire 14 are mixed and solidified as a weld metal. . The welding conditions described above are within a range that can be industrially sufficiently adopted.

Next, as shown in FIG. 1 (f), the Ti rod 1
A welding torch 19 of a TIG welding machine is set above (immediately above) 2 and overlay welding is performed using an aluminum filler material (filler rod) 20. That is, the weld overlay 21 is formed by low-power TIG welding so as to cover the Ti rod 12 and the weld overlays 15 and 16 for MIG welding. Now the Ti rod 12
It is joined to the aluminum base material 11 while being surrounded by the weld overlays 15, 16 and 21. This state is shown in FIG. 3, which schematically shows a cross section. The welding conditions at this time are: pulse current 100 A (base current 50 A), welding speed 200 mm / min,
The flow rate of the shield gas (He) was 25 liters / min, and Al-15Cu-2Ni-0.1Ti-0.05B was used as the aluminum filler material 20. Looking at this section, the weld overlays 15, 16, 21
Is formed as a homogeneous weld metal without cracks, etc., and it can be seen that the Ti rod 12 is joined in a good condition. This welding condition is also within a range that can be industrially sufficiently adopted.

Thus, the Ti rod 1 is formed on the aluminum base material 11.
2 is placed, and MIG is made on both sides by using aluminum wires 14.
After welding, TIG welding was used to perform overlay welding from above the Ti rod 12 using the aluminum filler material 20, so the reaction between Ti and Al during welding was suppressed, and the interface (reaction layer) Moreover, the precipitation of intermetallic compounds can be reduced. That is, the aluminum base material 11 and the Ti rod 12 can be welded with sufficient joining strength and under the welding conditions in the normal range in which mass production can be performed, and the heat resistance of the aluminum material can be improved at low cost and high quality. To be achieved.

In this embodiment, the Ti rod 12 is placed on the flat aluminum base material 11. However, as shown in FIG. 4, a mountain-shaped mounting portion 31 is formed on the aluminum base material 11. Alternatively, the Ti rod 12 may be placed at the position of the apex 32 and the arc of MIG welding may be applied in the direction 34 perpendicular to the slope 33 of the mounting portion 31. By doing so, the defective joint between the Ti rod 12 and the weld overlay is reduced,
The bonding strength can be further increased. Further, the Ti rod 12 is not limited to one having a circular cross section, and for example, an inverted triangular Ti rod 41 may be used as shown in FIG. The direction 42 of the arc at this time is the vertical direction or the Ti rod 41.
It may be slightly inclined to the side. However, regarding the shape of dissimilar materials, the bottom has a flat plate shape or a shape close to it,
For example, when a curved surface having a large radius of curvature is used, a gap may be formed between the bottom surface of the curved surface and the aluminum base material, and the bonding strength may be reduced, so care must be taken. The size of the dissimilar materials is not particularly limited, but if joining is not possible with one MIG welding, the multi-layer embossing 43 may be used as shown in FIG.

The different material used is preferably a heat-resistant substance having a high melting point (1,000 ° C. or more) such as titanium so that the melting by the arc or the reaction with the weld overlay portion does not proceed excessively. Further, if the surface of the dissimilar material is previously subjected to aluminizing treatment or the like, the wettability is improved, and better welding can be performed. The welding wire used for MIG welding or the filler material for TIG welding may be an Al-based alloy, an Al wrought material, or the like. In addition, the build-up welding performed from above the dissimilar material is not limited to TIG welding, but may be MIG welding at the same output or other arc welding. Further, if the remelting process (DC TIG) is performed to remove defects such as blowholes after the build-up welding, better welding can be obtained.

Next, FIG. 6 shows a specific embodiment of the present invention, showing a case where the piston 51 of the internal combustion engine is locally strengthened. A reentrant type combustion chamber 53 having a shelf portion 52 is sectioned and formed on the upper surface of the piston 51, and the shelf portion 52 with severe thermal stress is a site to be strengthened. That is, the foreign material 54 such as Ti is embedded in the shelf 52. When manufacturing this piston 51,
As shown in FIG. 7, after forming a basic piston body (coarse material) 55 having a depressed center by aluminum casting, a ring-shaped dissimilar material 54 is placed coaxially with the central recess 56. The ring inner diameter of the dissimilar material 54 is slightly larger than the inner diameter of the protruding end of the shelf 52. The mounting surface 5 on which the dissimilar material 54 is placed
7 is different material 5 than the level of the piston upper surface 58.
The position is lower by a distance equal to or larger than the diameter of 4. Therefore, the mounting surface 57 may be formed in a stepped shape as illustrated. Then, MIG welding is performed along the ring inner diameter side and the outer diameter side of the dissimilar material 54, and the weld overlays 15, 16 are formed.
The dissimilar material 54 and the piston main body 55 are joined together. Then, in consideration of the machining allowance, the TI overlay is obtained so that the weld overlay 21 that is appropriately higher than the level of the piston upper surface 58 is obtained.
Overlay welding is performed by G welding, and finally, the shelf 52 and the combustion chamber wall 59 having a predetermined shape are cut and processed to partition and form the combustion chamber 53. This makes it possible to manufacture the reentrant type combustion chamber 53 in which Ti is added to the shelf 52 and which is heat-resistant reinforced. That is, the heat resistance of the combustion chamber 53 is improved. In addition, in this kind of piston 51, other portions to be strengthened, for example, the ring groove 60 that is required to have wear resistance.
On the other hand, the reinforcing substance may be welded and joined by the same procedure.

FIG. 8 shows another specific embodiment of the present invention, which is applied to a cylinder head 71 of a four-valve internal combustion engine. On the lower surface of the cylinder head 71, since the space between the intake port 72 and the exhaust port 73 (valve portion 76) is thin, thermal cracking is likely to occur, and this is the portion to be strengthened. Therefore, a dissimilar material 75 such as a Ti rod is placed on the lower surface of the cast cylinder head (coarse material) radially from the position of the nozzle hole 74 so as to pass through the intervalve portion 76, and MIG welding is performed on both sides of the material. The overlay welding is performed by TIG welding or the like. As a result, the heat resistant component is added to the intervalve portion 76 of the cylinder head 71, and the heat resistance is improved. In the cylinder head 71, the strengthening substance may be welded to other portions to be strengthened, for example, the valve seat portion of the port, by the same procedure.

The present invention is not limited to the piston 51 and the cylinder head 71 shown in these specific embodiments, but can be widely applied to aluminum parts or aluminum members to be locally strengthened.

[0017]

In summary, according to the present invention, the strengthening substance can be locally strengthened and joined to the aluminum base material by the good welding with less precipitation of the intermetallic compound under the industrially applicable welding conditions. That is, it has an excellent effect.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a method for locally strengthening an aluminum material of the present invention, in which (a) is a perspective view of a dissimilar material placed on an aluminum base material, and (b) and (c). Is a front sectional view of a process of MIG welding both sides thereof, (d) and (e) are front sectional views of a weld overlay portion, and (f) is a front sectional view of a overlay welding process from above a dissimilar material. .

FIG. 2 is a cross-sectional photograph showing a bonded state of a dissimilar material and an aluminum base material.

FIG. 3 is a schematic cross-sectional view showing a joined state of a dissimilar material and an aluminum base material.

FIG. 4 is a front sectional view showing a main part of another embodiment of the present invention.

FIG. 5 is a front sectional view showing a main part of another embodiment of the present invention.

FIG. 6 is a diagram showing a specific embodiment of the present invention,
(A) is a side sectional view of the piston, and (b) is a plan view thereof.

7 is a cross-sectional view showing a main part of FIG.

FIG. 8 is a bottom view of a cylinder head showing another specific embodiment of the present invention.

FIG. 9 is a plan view of a piston for explaining the problems of the conventional technique.

[Explanation of symbols]

11 Aluminum base material 12 Different materials 13 Welding torch (for MIG welding) 14 Welding wire (aluminum wire) 15,16 Weld overlay 19 Welding torch (for TIG welding) 20 Aluminum filler

Claims (2)

(57) [Claims] 1. A dissimilar material made of a strengthening substance is placed on an aluminum base material, MIG welding is performed on both sides of the dissimilar material using aluminum wires, and then meat is formed by arc welding from above the dissimilar material using an aluminum filler material. A local strengthening method for aluminum materials, which is characterized by welding by welding. 2. The method for locally strengthening an aluminum material according to claim 1, wherein the strengthening substance is a refractory substance having a high melting point such as Ti.