JPS61190051A - Manufacture of al type hollow section having low coefficient of linear expansion - Google Patents

Abstract

PURPOSE:To obtain Al type hollow sections excelling in low linear expansion coefficient characteristic and dimensional accuracy by subjecting an Al alloy ingot containing specific amounts of Si, Mg, Fe, and the like to soaking treatment under specific conditions and then to hollow extrusion at the temp. lower than that of the soaking treatment. CONSTITUTION:The Al alloy ingot containing, by weight, 5-15% Si, <=1.0% Mg, <=0.5% Fe, and <=0.25% each of Cu, Mn, Cr, Zn, Ti, and Zn is refined. This Al alloy ingot is subjected to soaking treatment at 460-540 deg.C for 2-8hr and then to hollow extrusion at 420-500 deg.C lower than the soaking temp. to obtain the hollow sections such as tubes. These hollow sections have superior mechanical strength as well as low linear expansion coefficient characteristic and wear resisting property, and, besides, no particular defect can be seen in their weld metal zones.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for producing /l (aluminum)-based hollow shapes having a low coefficient of linear expansion, and in particular, to
AI that has a base linear expansion coefficient according to the manufacturing method of hollow shapes from alloy ingots by hollow extrusion! It relates to a method for manufacturing medium-sized medium-sized goods, shapes, and materials.

(Background technology) Due to its light weight, Al-based materials have traditionally been used in various equipment parts and even industrial products. From the main body to vehicle body outer panel parts and suspension-related parts,
Furthermore, its application and use are expanding to include structures and functional components related to the engine area.

By the way, with the expansion of the use of such AJ-based materials, various properties are required, especially for structures and functional parts related to automobile engines, such as those mentioned above, which are exposed to high temperatures. For parts and parts that undergo thermal cycles, it is desirable to use materials with low thermal expansion, in other words, low coefficient of linear expansion, and for parts that are exposed to abrasion environments such as rotating parts. Therefore, wear resistance properties are required.

On the other hand, Al has a low coefficient of linear expansion and excellent wear resistance.
As for the Aj! series alloy, it is in the 4000 series. -3i alloys are known, but this alloy has poor extrusion properties due to its high Si content, making it extremely difficult to obtain hollow shapes. has become common knowledge.

In hollow extrusion to obtain hollow shapes, a porthole die is generally used, and the billet is divided and extruded from multiple ports, and the billets are crimped at the exit of the die to produce the desired product. It is made into a hollow shape material, but the compression bondability (
This is because it was considered difficult to form a good integral hollow product due to its poor adhesion.

For this reason, casting has traditionally been considered as a method for manufacturing hollow products from high-Si content Af-based alloys, but the cast products obtained by this method have poor dimensional accuracy. However, in order to make precision hollow parts, it is necessary to cut (cut out) such castings, which raises the problem of increased manufacturing costs. There are inherent problems in that the cutting process is extremely troublesome.

(Structure of the Invention) As a result of various researches against the background of the above circumstances, the present inventors have developed an AI-based hollow material having a low coefficient of linear expansion by devising various alloy components and manufacturing methods. We have discovered the fact that shapes can be advantageously manufactured by hollow extrusion, in other words, by porthole extrusion, without creating any foreign phase in their crimped parts (porthole welded parts), and have arrived at the present invention. be.

That is, the present invention contains, on a weight basis, 5 to 15% Si, up to 1.0% Mg, and has an Fe content of 0.0%.
5% or less, Cu, Mn, Cr, Zn.

The content of Ti and Zr was both 0.25% or less,
460 to 5 for an AA alloy ingot with the remainder being Af.
After soaking at a temperature of 40°C for 2 to 8 hours, hollow extrusion was performed at a temperature of 420 to 500°C, which is lower than the soaking temperature, to form the desired hollow shape. .

(Specific description of the structure) Here, according to the present invention, Si, which is the main alloy component mixed with Al, is Al! It is an effective element in reducing the linear expansion coefficient (thermal expansion coefficient) of the alloy.
Further, the addition of Si imparts wear resistance properties. In order to obtain a sufficient effect of lowering the coefficient of linear expansion by adding Si, it is necessary to add at least 5% (
It is necessary to add Si so that the ratio is equal to or higher than the weight standard (same below), and as the amount added increases, the effect of lowering the coefficient of linear expansion can be further exerted, but if the amount added is If it exceeds 15%, hollow extrusion becomes extremely difficult and a good hollow profile cannot be obtained, so addition of Si in an amount exceeding 15% must be avoided. In the present invention, an AA gold alloy having a Si content of 8 to 13% is preferably used.

In addition, Mg, which is the other main alloy component in the present invention, is
Aj! It is an effective element that can effectively increase the strength of -3i alloys while maintaining their low linear expansion and wear resistance properties, and the addition of Mg imparts mechanical strength that is effective as a mechanical element. However, the M
Since g is also an element that increases the coefficient of linear expansion of the alloy, its upper limit should be kept at 1.0%. In addition, such Mg is preferably added at a rate of 0.1% or more in order to improve the strength as described above, but it may simply cause the performance required of the obtained hollow shape to be low. In the case of expansion characteristics or wear resistance characteristics, the addition of Mg is not essential.

Furthermore, in the An alloy composition according to the present invention, the Fe content is 0.5% or less, and furthermore, Cu, Mn5CrS
The contents of Zn, Ti, and Zr are all set at 0.25% or less, and the contents of these alloy components or components mixed as impurities are regulated. However, when the amount of any of these Fe, Cu, Mn, Cr, Zn, and Ti increases, the extrusion characteristics deteriorate.

That is, this is because the extrusion speed or the pressure adhesion of the boat hole welded portion is reduced. Note that the total amount of these alloy components such as Fe is preferably suppressed to 0.3% or less.

In the present invention, after a molten Al alloy is prepared with such alloy components and composition ranges, the desired Al
In order to obtain an alloy hollow profile, a predetermined alloy ingot is cast from the molten metal according to a known ordinary method, and then the obtained ingot is extruded according to a predetermined hollow extrusion method (boathole extrusion method) to achieve the intended purpose. A hollow extruded section will be manufactured.

That is, first, A consisting of the alloy composition according to the present invention is prepared.
/2 for gold alloy ingots at a temperature of 460-540°C.
Soaking treatment will be performed for ~8 hours. By this soaking treatment, a high content of Si components and further Mg components can be finely dispersed in the alloy structure, thereby making it possible to refine the extruded structure. Note that if this soaking temperature is lower than 460°C, the dispersion of the alloy components such as St will not be sufficient, and therefore the extruded structure will not be sufficiently refined. If the temperature is used, it is not preferable because the alloy components may be leached into the grain boundaries and the alloy may become brittle. Note that this soaking process is performed in one step or in multiple steps.

Next, the soaked Al alloy ingot is subjected to normal boathole extrusion to form the desired hollow shape, at an extrusion temperature of 420 to 500°C. In addition, the soaking temperature is lower than the above-mentioned soaking temperature. By setting this extrusion temperature lower than the soaking temperature, problems such as the crystal grains of alloy components such as Si that are dispersed and precipitated become larger, and the pressure bonding properties of boat hole welds deteriorate due to surface oxidation can be prevented. That will happen.

The hollow extruded shape obtained in this way is cut out to a predetermined size as necessary to make the desired hollow product, but such an extruded shape also includes If necessary, tempering treatment, or quenching treatment and tempering treatment are performed according to conventional methods.

(Effects of the Invention) As described above, according to the present invention, even if an Al-based alloy with a high Si content has a high Si content, boathole extrusion can be performed without causing any defects in the welded part. This made it possible to advantageously obtain the desired hollow extruded shape, which not only expanded its use as an AN alloy with a small coefficient of thermal expansion, but also made it possible to form the desired hollow material without machining. It is also possible to obtain the same material, reducing the processing time and cost, and because it is an extruded material,
Compared to machining, complex shapes can be obtained at low cost, and strength can be controlled over a wide range by adjusting the amounts of St and Mg within the range of the present invention.

Due to these characteristics, the Al-based hollow extruded shape obtained according to the present invention can be suitably used in related parts around the engine of automobiles, for example, rotating parts such as rotors, parts subject to thermal cycles, etc. This is where the present invention has great industrial significance.

(Examples) In order to clarify the present invention more specifically, some examples of the present invention are given below, but the present invention is not limited in any way by the description of such examples. That goes without saying.

Example I Si: 10.54%, Fe: 0.14%, Cr:
An Al alloy ingot having a chemical composition of 0.01% Ti: 0.01% and the balance Al2 was melted, and 500%
After soaking for 4 hours at ℃, boathole extrusion was carried out at an extrusion temperature of 460℃ to obtain a boathole extruded tube (hollow shape material) with a tube outer diameter of 267 mm and a tube wall thickness of 3.5 m + t. ) was obtained.

When we performed a cone expansion test on this extruded tube to check for defects in the welded part, cracks occurred at an expansion rate of 1.4D, but the cracks occurred in the base material. (locations other than the welded areas), and as a result, it was determined that there were no particular defects in the welded areas. Further, as a result of observing the cross-sectional macrostructure and microstructure of the welded part and the normal part, it was found that the crystal grains were very fine and no defects were observed in the welded part.

The linear expansion coefficient of the obtained extruded tube was determined to be 19°5 x 10-6/"C (temperature range = 23 to 150°C), which is higher than that of a normal extruded shape. The linear expansion coefficient of the material made of the A6063 alloy, which is known as a material, was significantly smaller than 23.8 x 10-6/°C.The chemical composition of the A6063 alloy was Si:0. 20-0.6%.

Fe: 0.35%, Cu: 0.10%, Mn 1.10%
, Mg: 0.45-0.9%, Cr: 0110%
.

Zn: 0.10%, Ti: 0.10%, /l! : Consists of the remainder.

Example 2 Various Al alloy ingots having the chemical components shown in Table 1 below were melted and soaked at 500°C for 4 hours. Boat hole extrusion was carried out with the extrusion temperature set to
A 3.5 mm boathole extruded tube was obtained. In addition, the extrusion speed was 6.5 to 8.0 m/min in all cases.

Regarding the various extruded tubes (T, material) obtained in this way, and those obtained by subjecting such T1 material to tempering treatment (T, material),
Further, the mechanical properties of the materials subjected to water quenching and then tempering (T6 materials) are shown in Table 2 below.

As is clear from the comparison of the results in Tables 1 and 2, it is recognized that the strength increases and the elongation decreases with the addition of Mg and the increase in the amount of Si. Further, when extruded tubes obtained from each material were subjected to tube expansion tests and the welded portions thereof were evaluated, it was found that there were no particular problems with the welded portions even if Mg was added. Furthermore, when we investigated the cross-sectional macro and micro Mi textures of these extruded pipes, we found that it was not clear whether welded areas or normal areas could be distinguished.
It was determined that complete welding had been achieved, but material I
For I&15 (13% Si), the presence of some giant compound was observed.

Claims (1)

[Claims] Contains 5 to 15% Si and up to 1.0% Mg, and contains 0.5% or less of Fe, Cu, Mn on a weight basis.
, Cr, Zn, Ti and Zr contents are all 0.25
% or less, the remainder of which is Al, is soaked at a temperature of 460 to 540°C for 2 to 8 hours, and then soaked at a temperature of 42°C, which is lower than the soaking temperature.
A method for producing an Al-based hollow shaped material having a low coefficient of linear expansion, which comprises performing hollow extrusion at a temperature of 0 to 500° C. to form a desired hollow shaped material.