JPS59113164A - Production of bumper for automobile - Google Patents

Abstract

PURPOSE:To obtain a bumper for an automobile which is lightweight, is highly strong and is highly resistant to stress corrosion cracking by subjecting an A7003Al alloy contg. prescribed proportion of Zn, Mg, Zr, Cu, etc. to two-stage artificial aging treatment after extrusion processing under a prescribed condition. CONSTITUTION:An A7003Al alloy contg. 5-6.5% Zn, 0.5-1% Mg, 0.5-0.25% Zr, and contg., as impurities, <=0.3% Si, <=0.35% Fe, <=0.2% Cu, <=0.3% Mn, <=0.2% Cr, <=0.2% Ti is melted. The billet of such alloy is heated to >=450 deg.C and is then extruded to form a hollow extrudate of which the diameter of the circumcircle in the hollow part is made to <=100mm. and the circumferential length in the part of <=3mm. wall thickness is made to <=50% of the entire circumferential length in the hollow part. Such extrudate is subjected to aging for 2- 8hr at 75-105 deg.C after the extrusion processing then to aging for 4-10hr at 135-165 deg.C, whereby two- stage artificial aging treatment are accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an automatic dirt bumper.

In recent years, there has been a remarkable trend towards automatic ■lighter layering, and as part of this purpose, conventional! The use of aluminum @gold bumpers in place of iron bumpers is being considered. Among various aluminum alloys, 2T'
The composition range of A7003 alloy in L is Zn5, (
J~6, 5%, Mgo, 5°~1.0%, Zr(1,
05-11-25%, 810.30% or less as impurities, Fed-85% or less, CuQ, 20% or less, Mn0.
80% or less, CrO, 20% or less, TiO, 20% or less, others individually 0.05% or less9, total 0.15% or less, balance Al, medium to high strength aluminum alloy. Among them, it has relatively good extrusion processability, but
The drawback is that it is difficult to extrude complex shapes such as thin hollow shapes with a wall thickness of approximately 8 mm or less, which can reduce weight. Even if the billet heating temperature used in Yoshiba extrusion processing is increased to extrude such complex shapes, the stress corrosion resistance will be significantly impaired in this case, resulting in damage to the bumper itself. Otherwise, there is a risk of fatal defects such as the bumper falling off due to damage to the mounting part.

For the above reasons, conventionally (go) has been limited to thick-walled materials with a wall thickness of 8n or more or extruded shapes of solid materials,
There was a problem that the effect of reducing the number of employees could not be expected to be sufficient.

The present invention was completed as a result of various researches in order to establish a manufacturing method for automatic soil bumpers that are lightweight, have high strength, and have excellent stress corrosion resistance. In the method of manufacturing an automatic soil bumper by extruding into a hollow profile using A7008 aluminum alloy (al above A?00
3 fi of Cu in aluminum alloy! :Eo, 1~
(b) Hollow extruded cedar wood whose circumscribed circle has a diameter of 100 mm or more, and the circumference of the hollow part with a wall thickness of 3 m or less is 50% of the total circumference. Extrude the above hollow extruded shape, (c) Billet heating during extrusion processing?&['E45
0°C or higher, and (d) after extrusion processing, it is characterized by performing a two-stage artificial aging treatment of aging at 75 to 105°C for 2 to 8 hours, and then aging at 135 to 165°C for 4 to NOR. It is something.

(8) According to the composition and content specifications of A700B aluminum alloy,
Cu is not particularly considered as an effective element, but 0.
It is regulated to 20% or less. However, we have discovered that adding 0.1% or more of Cu is effective in improving stress corrosion cracking resistance. It was also found that if the amount of Cu added exceeds 0.2%, it would have an adverse effect on corrosion resistance, so stress corrosion resistance could be improved without impairing corrosion resistance.
In order to improve the properties, it is necessary to add 0.1-0.2% Cu.

In this way, A700 with Cu iko of 1 to 0.2%
8 aluminum alloy is extruded into a hollow shape, and the total circumscribed diameter of the shape is 100 mm or more.

In general, in extrusion processing, the larger the object, the more difficult it is to extrude, but in the present invention, Ggo is able to extrude a large shape that was conventionally considered difficult to extrude, and in order to fully satisfy the performance as a bumper, the circumscribed circle Immediately after, the hollow shape member is 1QQjll1 or more. In addition, in order to fully demonstrate the effect of weight reduction, this profile has a wall thickness around the hollow part of approximately 8.
(
4) The circumference of the part must be at least 50% of the total circumference.

In addition, since the present invention is directed to the production of a lightweight and high-strength automatic blood pumping bumper, it is necessary to be able to extrude large and thin hollow shapes such as those mentioned above, and such complex In addition, in order to extrude a thin-walled shape, the billet must be heated to a high temperature of 450° C. or higher during extrusion. Conventionally, when extrusion processing is carried out at such high temperatures, the recrystallized grains of the extruded shape will become coarser and the stress corrosion resistance of the extruded shape will be significantly impaired. In the present invention, the A7008 aluminum alloy had to be inserted at a low temperature (3n), and was limited to extrusion processing of thick-walled materials and solid materials. By adding .2% Cu, the resistance to corrosion cracking was greatly improved, making it possible to extrude thin-walled hollow shapes at such high temperatures. The extruded hollow shape material is then subjected to artificial aging treatment.Then, in the present invention, it is made into a thin extruded shape material to reduce weight, and in order to satisfy the characteristics of high strength, the material itself must be nollil
It is essential that the temperature is high. As a specific guideline, it is desired that a yield strength of 80 kg/+a+2 or more be stably provided. Therefore, at 75-105°C
Aged for ~8 hours, then aged at 185-165 °C for 4-10
It is necessary to perform two-stage artificial aging treatment.

This artificial aging treatment is a condition for achieving maximum strength in this alloy, and it can be used at higher humidity or lower temperature, for short or long periods of time, or even for just one stage of aging. The elasticity is insufficient. Generally, artificial aging treatment such as T which brings about such maximum strength decreases stress corrosion resistance, but in the present invention, 0.1 to 0.2% Cu is applied to A7008 aluminum alloy. By adding this point, it is possible to improve En, maximize strength without impairing stress corrosion resistance, and make it possible to perform artificial aging treatment.

In the manner described above, an automatic bumper made of a thin-walled hollow profile that is lightweight, has high strength, and has excellent stress corrosion resistance is manufactured. In order to use it as an automatic main bumper, it is common to subject the profile to various bending processes, drilling processes for attachment to the vehicle body, and shearing processes.

If these processes are performed after artificial aging treatment, it will be quite difficult to process due to its high strength, and even if it is possible to process it, residual stress will remain, resulting in a decrease in stress corrosion cracking resistance. Ru. For this reason, bending is required.

When hole-filling, shearing, etc. are carried out, they are carried out at mJ of artificial aging treatment, but preferably carried out at least between the first aging and the second aging.

Next, embodiments of the present invention will be explained.

Example 1 Luminium alloy billets (diameter 176 mm, length 50 (131 mm)) having the chemical composition shown in Table 1 were prepared; 8 billets were prepared for alloy A, and 1 billet each for alloy B and alloy C. Son-'Pnzso.

Using a ton extruder, it was extruded into a shape (7) having the cross-sectional shape shown in Figure 1. The diameter of the circumscribed circle of this profile is l
40 tRM, and the wall thickness of the hollow part T is t1=1.6, t2=1.6*a, t3=2, Orm *t4=2.
It was 8 mm. Therefore, all the hollow parts of this profile have a wall thickness of 3gg or less, and in detail, the wall thickness of 1.6n or less is 45mm.
%, 2.0 fight or less is 80% # 2-8” or less is 100
%Met.

The billet was then heated to the extrusion temperature shown in Table 2 and extruded at that temperature. 3.The shape after extrusion processing is as follows:
Artificial aging treatment was performed under the conditions shown in Table 2.

The obtained gamma cedar wood was evaluated by tensile tests and stress corrosion cracking tests. In the stress corrosion cracking test, a hole is punched in the center of the test piece using a puncher using a power press.
After that, the artificial aging treatment was performed, and then the stress corrosion test solution (CrOB869, 2Cr2o780f
- NaCl18F dissolved in 1000 oo of water), held at 50°C for 72 hours, taken out, no stress corrosion cracking was observed n (8) Those with no stress corrosion cracking passed, those with stress corrosion cracking recognized. It was evaluated as failing.

The results of the tensile test and stress corrosion split test are shown in Table 8. Of the samples shown in Table 2, A-1 could not be extruded, so no test was conducted. In addition, as an example of the present invention, a cross-sectional micrograph of alloy B after stress corrosion cracking test (2
0x) is shown in FIG. 2, and as a comparative example, a cross-sectional micrograph (20x) of a C alloy after a stress corrosion cracking test is shown in FIG. 8.

As is clear from the above results, according to the present invention (7)
(A-2, B) t; J, Izun also have a proof strength of 30 kg
/par? The stress corrosion rate was 1. was not seen at all.

On the other hand, even if Cu is added, the extrusion temperature is low (A-1)
However, it is impossible to extrude into thin-walled hollow shapes, and even if extruded at high temperatures, artificial aging treatment is performed in one stage (
In A-3), the strength was insufficient. Stress corrosion cracking was observed in the sample (C) which was extruded into a thin hollow profile at high temperature without adding Cu as an effective element.

As explained in detail above, the present invention enables extrusion processing of thin-walled hollow materials with a focus on weight reduction, as well as excellent cold workability and stress corrosion cracking resistance. It becomes possible to manufacture automobile bumpers with high strength.

[Brief explanation of the drawing]

FIG. 1C is a longitudinal sectional view of the hollow profile extruded in Example 1. Figures 2 and 3 show cross-sectional micrographs (11) and mirror photographs (20x magnification) of the test piece after the stress corrosion cracking test conducted in Example 1, and the second thickness is an uninvented one (
B alloy), and FIG. 8 shows a comparative example (C alloy). Patent applicant Aisin Seiki Co., Ltd. Representative Reio Nakai Representative Aisin Light Metal Co., Ltd. Michitsugu Inaba Sumitomo Aluminum Smelting Co., Ltd. Representative Heizo Itoi (12) T 1st Flash Figure 2 Figure 3 319-

Claims (1)

[Claims] α) A7003 aluminum alloy (Zn5.O~6
．． 5%, Mg0.50-1, 0%, Zr0.05-0
25% - Si0.30% or less as impurities, FeO,
85% or less, Cutl, 20% or less, Mn 0.30% or less, Cr 0.20 or less, TiO, 2U% or less, others individually 0.05% or less 1 total 0.15% or less, remainder A
In the method of manufacturing a bumper for an automatic vehicle by extruding an alloy consisting of (aluminum) into a hollow profile,
1 of Cu in the A 7003 aluminum alloy
A billet with rK of 0.1 to 0.2% was extruded into an extruded shape. (C1 The billet heating temperature during the extrusion process was 4500C.
(d) After extrusion processing, at 75 to 105 °C for 2 to 8
Aging for 4-10 hours at 185-165℃
A method for producing an automatic soil bumper with high strength and excellent stress corrosion resistance, characterized by performing a two-stage artificial aging treatment with one aging. (2) When processing a shape material with residual stress such as bending, drilling, shearing, etc., a patent claim must be made before the two-stage artificial aging treatment or between the first and second aging stages. The method described in Item 1 of the scope or Item 2 of GJ.