JPS5827947A - Medium-strength aluminum alloy for extrusion with superior hardenability and toughness - Google Patents

Abstract

PURPOSE:To provide a medium strength Al alloy for extrusion consisting of a prescribed percentage each of Mg, Si, Cu, Mn and Zr and the balance Al with inevitable impurities, showing medium strength only by T5 treatment after extrusion, and having superior hardenability and toughness. CONSTITUTION:This medium strength Al alloy for extrusion consists of, by weight, 0.7-1.1% Mg, 0.4-0.8% Si, 0.10-0.30% Cu, 0.20-0.60% Mn, 0.05- 0.30% Zr and the balance Al with inevitable impurities. The amount of Fe among the impurities entering inevitably from starting materials is required to be <=0.30wt%. The alloy is manufactured by a known method and can be supplied in the form of a billet. The mechanical properties of the alloy after extrusion satisfy the requirements of JIS6061.T6 only by T5 treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a medium-strength aluminum alloy for extrusion that has excellent hardenability and toughness.

Conventionally, kl -M, -8i series alloys suitable for a wide range of applications such as medium-strength structural materials and various strength members include:
A typical example is JIS6061 alloy (s70.40~0
8 weight ratio, F, 0.7% by weight or less, o, 0.15-0
．． 40 weight section, MrLO, 15 weight 1tq6 or less, IJy
o, 8 to 1.2% by weight, Or 0.04 to 0.35% by weight, Z 0.25% by weight or less, Ti 01515% by weight or less, other sides 005% by weight or less, total 0. 15% by weight or less, the balance being M).

However, this alloy has a high Mg+J content and Cr is added to improve toughness, so it is highly sensitive to quenching. Therefore, sufficient strength cannot be obtained by air cooling alone after extrusion unless the T6 treatment for hardening is performed. For this reason, either quenching the die end by water cooling during extrusion or
Alternatively, quenching treatment is performed again, but the extruded material becomes distorted due to water cooling, resulting in a decrease in yield due to poor shape, or poor workability and productivity. Therefore, there was a need to develop an alloy with improved quench susceptibility and without the above-mentioned drawbacks.

As a result of intensive research to satisfy these requirements, the present inventors found that the mechanical properties are equivalent to JT860 even with only T5 treatment after extrusion.
61 R that satisfies the T6 standard and also represents bendability
/,! (R: 90° minimum bending radius - plate thickness) is 2
We have developed the following medium-strength aluminum alloy for extrusion with excellent hardenability and toughness.

That is, the present invention contains MyO, 7 to 1.1% by weight, Si0.4
~08-3- Weight%, c, 0.10-0.30 Weight ratio, M,
0.20-0.60% by weight, Zr0. Os ~ o, ao
! ! :%, the balance being Al and unavoidable impurities, and relates to a medium-strength aluminum alloy for extrusion with excellent hardenability and toughness.

M8i is the main additive element t that forms Mg2Si, and unless M reaches 07% by weight and S reaches 0.4% by weight, sufficient strength cannot be obtained, and M! i is 1.1% by weight,
If Si exceeds 0.8% by weight, hardenability and extrudability will decrease.

O, L is effective in improving mechanical properties through age hardening, but if it is less than 0.10% by weight, the effect is small;
If it exceeds % by weight, corrosion resistance will deteriorate and extrudability will also decrease.

Mnlzr is finely precipitated in the matrix as Mnl-based and zr-based compounds and is effective in improving the hardenability and toughness of the alloy, but the effect cannot be fully exhibited when added alone. M and L are 0.20% by weight, Zr is 0.50% by weight
If it is less, no effect can be expected, and if MrLO exceeds 60% by weight and z, -o exceeds 39% by weight, hardenability and toughness decrease.

JP-A-58-2'7947 (2) At the stage of producing the alloy of the present invention, refinement treatment may be performed using Al-Ti-+3@ alloy in order to improve billet quality and castability.

The alloy of the present invention contains impurities that are inevitably mixed in from the raw materials. It is necessary to keep F at 0.30% by weight or less. 0
If F exceeds 30% by weight, extrudability and toughness decrease.

The alloy of the present invention is supplied in billet form, and its manufacture is based on known methods. The mechanical properties after extrusion are JIS 6061 with only T5 treatment.
It satisfies the T6 standard. Moreover, it goes without saying that the characteristics will be even better if T6 processing is performed.

Next, examples of the present invention will be shown.

Example 1 Table 1 shows the AtMy Si alloy composition used in this example.

S- 6- Mold ingot with these compositions (50+mm x 40
am X200111111) by a conventional method,
A round bar (29rm
φX 90 as ) was cut out and extruded using a universal testing machine under the following conditions for each sample to create plate samples.

Die shape: 2 bleached x 23 wrl Extrusion ratio: 14 Extrusion temperature: 480°C Extrusion speed: 84 on/rd' JI8 was used for tensile testing from the plate sample thus obtained.
No. 13B test piece and 60 womX for bending test
A test piece of 23 m x 2 mg was prepared. Each test piece was heated at 550°C for 3 hours, assuming T5 treatment in extrusion processing.
Perform solution treatment for 0 minutes, then reduce the cooling rate to 2℃74
It is then cooled to room temperature as a rice field and then tempered at 175°C for 8 hours.

Table 2 shows the results of measuring the mechanical properties of the tempered specimens at room temperature.

- 7 - Table 2 In the above table, () means that it does not meet the JIS 6061 T 6 standard, ○ means that there is no cracking at R/l = 2, and × means that cracking occurs at Vl = 2. .

Example 2 The component composition is M! 7o, ss Judo Chi, 8i0.5B weight%, 014020 weight ratio, MaO, 27 weight%, Zr0
．． 09% by weight, vtO3 16% by weight, Ti 0.01
A semi-continuously cast billet (22B-φX500+nm) of the alloy of the present invention with a heavy weight and the remainder A-1 was cast. After homogenizing this billet at 580°C for 8 hours,
An L-shaped solid material with a wall thickness of 3 m+n and a cross section of 324 mm was obtained by extrusion processing. After 21 hours of extrusion, the solid material obtained by this extrusion process is subjected to T5 treatment, that is, tempered at 175° C. for 8 hours for 14 hours. JIS 1 for tensile testing from tempered solid material
3 60wn x 23 for No. B test piece and bending test
Group x 3 test pieces were prepared and their mechanical properties were measured. The result is a tensile strength of 30.2 K9. /U, 02chi yield strength 26.1 (pcs, elongation 119%, JIS6061T
6 standards, and the minimum bending radius of 90° is V7.
= 2, no cracking was observed.

As shown in F below, the alloy of the present invention has medium strength after only T5 treatment after extrusion and has excellent toughness, so it is considered to have high industrial value as a medium-strength structural alloy.

Claims (1)

[Claims] My 0.7-1.1% by weight, 8i 0.4-0.8% by weight, Cu 0.10-0.30% by weight, MnO, 20-
A medium-strength aluminum alloy for extrusion with excellent hardenability and toughness, consisting of 0.60% by weight and 905 to 0.300% by weight of zrO with the balance being human and unavoidable impurities.