JPS63145756A - Treatment of aluminum alloy surface - Google Patents

Abstract

PURPOSE:To produce Al alloy stock whose surface has superior thermal fatigue resistance, by forming many small recesses in the surface of Al alloy stock, subjecting the surface to TIG remelting and cooling to make the structure fine and planing the surface. CONSTITUTION:Recesses 2c of 2-4mm diameter and 1-4mm depth are formed in the surface 2a of Al alloy stock so that they account for >=50% of the area of the surface 2a. The surface 2a is then remelted with a tungsten electrode 3 whose diameter phi is larger than the diameter of the recesses 2c and the remelted surface is cooled to form a part 2b having a fine structure. The cooled surface is machined to plane the part 2b and Al alloy stock whose surface has superior thermal fatigue resistance is produced.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an improvement in a method for treating the surface of an aluminum alloy.

(Prior art and its problems) Generally, for example, in automobile engines, higher output and lower fuel consumption are pursued, and therefore the temperature in the combustion chamber tends to rise.

For this reason, the thermal load on the valve bridge portion of the aluminum alloy cylinder head becomes more severe, and in conventional low-pressure casting cylinder heads, cracks and the like occur in the valve bridge portion, causing problems such as water leakage.

Therefore, as a countermeasure to this problem, as shown in Fig. 2 (a), the surface (upper part) Ia of the aluminum alloy material (valve bridge) l is remelted using a TIG arc, etc., as shown in Fig. 2 (b). After refining the surface structure and cooling it as shown in FIG. 2(c), this surface 1a is cut at a predetermined height ho as shown in FIG. 2(d), thereby improving thermal fatigue resistance. A method has been proposed to improve this (see Japanese Patent Publication No. 61-36566).

However, in the conventional surface treatment method described above, the width W° of the refined portion tb is narrow and the depth is shallow from 1'. , TIG arc, ;) Because it is necessary to increase the current value or increase the number of beads, it is undesirable because it causes blowholes and a fine structure with uneven bead spacing. Surface 1a of 1tl alloy element
Since cutting is performed after remelting, if the refined portion 1b is shallow, most of it will be removed during cutting, so there is a problem that the effect of surface treatment cannot be obtained.

(Objective of the Invention) The present invention has been made in order to solve the above-mentioned conventional problems, and therefore aims to make it possible to easily obtain wide and deep refined portions on the surface of an aluminum alloy material. This is the purpose.

(Construction of the Invention) For this reason, the present invention provides an aluminum alloy material with a diameter of 2 to 4 mm on the surface.
a+m, depth 1-4III11 concave area ratio 50%
- It is characterized in that it is formed as described above, and then this surface is remelted by a TIG arc whose electrode diameter is larger than that of the recess.

(Effects of the Invention) According to the present invention, the absorption rate of TIG arc irradiation energy is increased by increasing the surface area by avoiding making the surface of the aluminum alloy material uneven.
It becomes possible to obtain a wide and deep finely divided portion.

In addition, because the width is wide, fewer beads are required, which reduces remelting defects, and because it is deeper, less fine parts need to be removed during cutting, which improves the effectiveness of surface treatment, that is, thermal fatigue resistance. It becomes like this.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1(a), the method for treating the surface of an aluminum alloy is to first coat the surface 2a of an aluminum alloy material 2 with a diameter of 2 to 4 mm.
Concave portions (spherical dimples) 2c, .

If the area ratio is less than 50%, a wide refined portion 2b (see FIG. 2(b)) cannot be obtained. When the number of beads is increased to increase the width, the structure between the beads becomes coarser. In addition, since it is difficult to ensure the depth of the refined portion 2b, it is necessary to increase the current value of the TAG arc or slow down the moving speed, but defects such as blowholes occur.

Further, if the diameter of the recessed portion 2c is less than 2n+m, the absorption rate of irradiation energy is low and the width of the refined portion 2b is narrowed. On the contrary, 4
If it exceeds III11, the irradiation energy will be locally concentrated and the required range will be insufficiently refined.

Furthermore, if the depth of the recess 2C is less than 1III+, TIG
The arc becomes one-sided, and a wide refined portion 2b cannot be obtained. On the other hand, if it exceeds 4 nm, there is a risk that the original shape will remain unless the cutting process is deep, and the TIG arc length will become non-uniform, making it impossible to obtain the refined portion 2b with a stable depth.

Next, as shown in FIG. 1(b), the surface 2a of this aluminum alloy material 2 is remelted with a T[q arc to refine the surface structure.

The TIG arc irradiation conditions were as follows: using an electric current of 4.8 nm whose diameter φ is larger than the diameter of the recess 2C, using Ar gas as an assist gas, current value: 300 A, transfer speed: 1
, Om/ll1in, arc length: 211II11.

After cooling as shown in Fig. 1(C), Fig. 1(d)
), this surface 2a is cut to a predetermined height h.

Next, an example will be described.

(1) On the surface 2a of the AC4D aluminum alloy material 2, a recess 2C with a diameter of 2 mm and a depth of 4 mm was formed at an area ratio of 60%. .

(2) Next, electrode 3. whose diameter φ is 4.8 mm. TIG arc irradiation was performed under the following conditions: Ar assist gas, 'rri flow value: 300 A, transfer II J degree 1.0 m/+++in, and arc length 2 II 1 m.

(3) Then, when this aluminum alloy material 2 was cut in cross section and the refined part 2b was observed, it was found that the refined part (melted part)
The width W of 2b was 12 mm J'' and the width d was 3.6 mm.

Also, when this was cut at a height h, the depth d was 2
A finer part 2b of about /3 (2.4 mm) could be secured.

Note that the size of the eutectic Si was about 6 μm, and the untreated portion was 40 μm, so it was confirmed that the size was miniaturized.

(4) For comparison, the surface 2a (surface roughness 11 μm) of the AC4D aluminum alloy material 2 was irradiated with a TIG arc under the conditions of (2) above, and the finer parts were observed. As shown in Fig. 2(c), the width of the refined part was 8 mm, and the depth d'' was 2.1 mm.
When this was cut, most of the finer parts were removed as shown in FIG. 2(d), and the effect of surface treatment could not be obtained.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(d) are explanatory diagrams of a method for treating an aluminum alloy surface according to the present invention, and FIGS. 2(a) to (d) are diagrams for explaining a conventional method for treating an aluminum alloy surface. 2... Aluminum alloy material, 2a... Surface, 2b...
Refinement part, 2c... recessed part.

Claims (1)

[Claims] (1) A method of remelting the surface of an aluminum alloy material to refine its surface structure, which involves melting the surface of the aluminum alloy material with a diameter of 2 to 4 mm and a depth of 1 to 4 m.
1. A method for treating an aluminum alloy surface, which comprises forming recesses with an area ratio of 50% or more, and then remelting the surface using a TIG arc having an electrode diameter larger than that of the recesses.