WO2005040440A1

WO2005040440A1 - Aluminum alloy extruded article excellent in shock absorbing property

Info

Publication number: WO2005040440A1
Application number: PCT/JP2003/013588
Authority: WO
Inventors: Shinji Makino
Original assignee: Aisin Keikinzoku Co., Ltd.
Priority date: 2003-10-23
Filing date: 2003-10-23
Publication date: 2005-05-06

Abstract

A shock absorbing member, characterized in that it is prepared by a method which comprises providing an aluminum alloy having a chemical composition, in wt %: Zn: 5.6 to 6.6 %, Mg: 0.75 to 1.10 %, Cu: 0.10 to 0.25 wt %, Mn: 0.05 to 0.20 %, Cr: 0.03 to 0.15 %, Zr: 0.10 to 0.25 wt %, Si: 0.02 to 0.10 wt %, Fe: 0.05 to 0.17 wt %, the balance: Al and inevitable impurities, casting the alloy, to prepare a billet, extruding the billet into an extruded article having a hollow cross-sectional shape, and then subjecting the article to an artificial aging treatment so as for the article to have an 0.2 % offset yield strength in the range of 320 to 390 MPa. The shock absorbing member comprises an aluminum alloy extruded article and is excellent in absorbing characteristics for collision energy generating, for example, in the collision between automobiles.

Description

Description Extruded aluminum alloy material with excellent shock absorption

The present invention relates to a shock absorbing member such as a pampering reinforcement beam for an automobile, and more particularly to a shock energy absorbing member at the time of a collision using an extruded aluminum alloy material. Background art

Extruded sections made of AI-Zn-Mg alloys are widely known for their high strength.

For automobile shock absorbers such as bumper reinforcement hoses and impact beams for automobiles, higher strength also contributes to weight reduction of parts and thereby the weight of automobiles, and also improves fuel efficiency.

However, the conventionally proposed AI-Zn-Mg-based aluminum alloy has a high tensile y-strength but is inferior in toughness, and not only reduces the amount of impact energy absorbed, but also in the event of a collision (during impact). There was a problem that cracks were easily generated.

If such an extruded material is used for a pampering reinforcement, etc., the edges of the cracks generated at the time of the collision may cause injury to humans, which is a serious safety problem.

Thus, for example, Japanese Patent Application Laid-Open Publication No. 2002-3227229 proposes an aluminum alloy extruded material having excellent crushing properties.

However, even with the aluminum alloy extruded material disclosed in the above publication, cracks are likely to occur at the time of collision, and the impact energy absorption is insufficient, and the stress resistance is low. Corrosion cracking was also insufficient. Disclosure of the invention

In the AI_Zn-Mg-based aluminum alloy, Fe and S components have been conventionally treated as impurities.

The present inventor has conducted a detailed investigation on the relationship between the power resistance and the energy absorption, and as a result, it has been found that high energy absorption can be stably obtained by controlling the Fe component and the Si component within a predetermined range. Became.

In addition, simply controlling the range of the aluminum alloy component to a predetermined range significantly changes the energy absorption depending on the conditions of human aging treatment, and it is difficult to stably suppress cracking at the time of collision.

In the present invention, it is clear that high energy absorption can be stably obtained by controlling the conditions of human aging treatment so that the 0.2% proof stress falls within the range of 320 to 390 MPa. Became.

Furthermore, since stress corrosion cracking often proceeds from the extruded surface of an extruded profile, the temperature of the profile during extrusion is controlled to be in the range of 500 to 540 ° C, so that it is resistant to stress. It was also found that stress corrosion cracking was improved.

Hereinafter, the specific contents of the present invention will be described.

As an aluminum alloy component suitable for the shock absorbing member made of the extruded aluminum alloy material according to the present invention, the Zn component has a 5.6 to 6.6% by weight (wt%) (hereinafter simply referred to as%). The Mg component is 0.75 to 1.10%, the Cu component is 0.10 to 0.25%, the Mn component is 0.05 to 0.20%, and the Cr component is 0.03 to 0.15%, Zr component is controlled to be in the range of 0.10 to 0.25%, respectively, and the Fe component, which was conventionally treated as an impurity, Is controlled within the range of 0.05 to 0.17%, and the Si component, which has also been conventionally collected as an impurity, is controlled within the range of 0.02 to 0.10%. The rest was virtually AI.

(1) About the Z n component

The Zn component has a significant effect on the aging characteristics together with the Mg component.Since the atomic radius of Zn is relatively close to the atomic radius of AI, the change in deformation resistance during extrusion is small, so the amount of the Mg component is reduced. In order to control the power resistance within a predetermined range while suppressing it,

It is better to control in the range of 5.6 to 6.6%.

If the Zn component is less than 5.60, the yield strength will decrease, and if the Mg component is to be increased to that extent, the formability will decrease, especially for extruded profiles with hollow cross-sections. Speed is slow.

On the other hand, if the Zn content exceeds 6.6%, the stress corrosion cracking resistance becomes poor.

(2) About the Mg component

The Mg component, together with the previously described Zn component, has a significant effect on aging. Therefore, in order to control the heat resistance within a predetermined range, it is preferable to control the Mg component within a range of 0.75 to 1.10%.

The Mg component has a larger radius of the element than the atomic radius of AI and greatly affects the deformation resistance during extrusion.If the Mg component exceeds 1.100 _{/ 0} , the extrudability deteriorates. If it is less than 5 o / o, the yield strength will be low if the Zn component is kept in the range of 5.6 to 6.6.

(3) Cu component

The Cu component can improve the stress cracking resistance by relaxing the potential difference between the crystal grain boundary and the inside of the crystal grain of the aluminum alloy.However, if the content is less than 0.10%, the effect is insufficient. %, The general corrosion resistance deteriorates, so the Cu component should be kept within the range of 0.10 to 0.25%.

(4) About Zr, Mn, and Cr components

The Zr component has a significant effect on the fibrous structure, and its effect is insufficient at 0.10% or less, and at 0.25 o / o or higher, the molten metal temperature must be increased during billet production. It is necessary to reduce the creativity.

Therefore, it is preferable to control the Zr component within the range of 0.10 to 0.25%. The Mn component has an effect of making crystal grains fine.

If the content of 1 \! ₀ component is less than 0.05%, the effect is insufficient, and if it exceeds 0.20%, extrudability deteriorates and quenching sensitivity becomes too high.

The Cr component was added while the 1 \ 1 ^ component was suppressed to 0.20% or less.

Like the Mn component, the Cr component has the effect of refining crystal grains and, together with the Zr component, turning the metal structure into a fibrous structure.

However, since Cr segregates as the amount of addition increases, it is better to control the Cr component in the range of 0.03 to 0.15%.

(5) About the Fe component

The Fe component, which is a characteristic component of the present invention, is mixed as an impurity in the manufacturing process of an aluminum alloy pillet.

Therefore, the mixing of Fe from the melting furnace and the production route was suppressed, and the Fe component was controlled in the range of 0.05 to 0.17%.

The study by the present inventors has revealed that the influence of the Fe component on toughness is very large.

The badness of the toughness of the Fe component changes sharply between 0.17 and Q.40%, and unless it is less than 0.17%, stable mechanical properties and energy absorption cannot be obtained. It is preferably 0.15% or less. For example, in a product requiring particularly stable collision energy absorption, such as a pump-in hose, the Fe component is 0.10% or less. Ideally it should be kept to

(6) S i component

The Si component also has a significant effect on the toughness of the extruded aluminum alloy material.To improve the toughness while controlling the heat resistance within a predetermined range, it is necessary to control it within the range of 0.02 to 0.10%. good. More stable mechanical properties and toughness, Ideally, the Si component should be 0.06% or less in order to ensure energy absorption. In this way, the ranges of each component are controlled, and the balance is produced using an aluminum alloy substantially consisting of aluminum.

At this time, control is performed to minimize the incorporation of Fe and Si components during melting of the base metal, the added mother alloy, and the like, and at the time of hot water supply to the combined billet. The obtained aluminum alloy billet is subjected to homogenization treatment (homo treatment) at 450 to 500 ° C for 4 hours or more, and an extruded member having a hollow cross-sectional shape is produced by an extrusion press.

ADVANTAGE OF THE INVENTION The aluminum alloy which concerns on this invention is excellent in extrudability, and the thin extruded shape of a hollow cross-sectional shape is obtained.

Automotive parts such as bumper reinforcements are often subjected to post-processing such as press bending to match the body shape.

Therefore, measures against stress corrosion cracking are important, and extrusion conditions are also important. Conventionally, the heating conditions of the billet, the temperature of the extrusion die, the extrusion speed, etc., were set in consideration of the shape and surface quality of the extruded material.

On the other hand, the present inventor has clarified that the temperature of the profile immediately after extrusion (in the vicinity of extruded from the extrusion die) has a great effect on the stress corrosion cracking resistance. It has been found that it is better to control the temperature of the material so that it falls within the range of 500 to 540 ° C.

If the section temperature exceeds 540 ° C, the size of the recrystallized grains increases, and the stress corrosion cracking resistance decreases rapidly.

On the other hand, when the temperature is lower than 500 ° C., the extrusion productivity decreases.

In order to ensure stable and high impact energy absorption, artificial aging of extruded profiles after extrusion is important. Perform two-stage artificial aging at 70 to 170 ° C for 6 to 20 hours.

For example, after the first heat treatment at 70 to 95 ° C. X 3 to 8 hours, the second heat treatment at 130 to 170 ° C. X 3 to 12 hours is performed.

The purpose of this artificial aging treatment is to prevent cracking at the time of collision by making the precipitates finer and more uniformly dispersed to increase the toughness.

Therefore, the treatment is preferably performed at a relatively low temperature for a long time, and the conditions are set so that the 0.2% proof stress falls within the range of 320 to 39 OMPa.

Since the heat treatment conditions vary depending on the hollow cross-sectional shape and thickness, it is better to use a test piece in advance to make investigation settings. Brief Description of Drawings

Figure 1

The results of the component analysis of the aluminum alloy used for investigation in the present invention are shown.

Figure 2

The results of measuring the quality characteristics when extruded profiles were obtained using the aluminum alloys with the components shown in Fig. 1 are shown.

Fig 3

The figure shows the results of measuring the amount of energy absorbed until a crack is generated by applying a load to a test piece having a hollow cross-sectional shape of a predetermined size.

Fig. 4

The results of analyzing the effects of the Fe and Si components on the energy absorption are shown. BEST MODE FOR CARRYING OUT THE INVENTION

Fig. 1 shows a composition table of the aluminum alloy used to investigate and confirm the effects of the present invention. Examples 1 to 5 are alloys according to the present invention, and Comparative Examples 1 to 4 are alloys for confirming the effects of components.

In Examples 1 to 3, alloys were designed for the purpose of confirming the influence of the Fe component and the Si component, so that the other components were the same.

Example 4 is an alloy designed for the upper limit of each component, and Example 5 is designed for the lower limit.

Comparative Example 1 is an alloy design in which each component exceeded the upper limit of the purpose of the present invention, and Comparative Example 2 was an alloy design in which components other than Fe and Sί deviated from the lower limits.

Comparative Examples 3 and 4 are alloy designs when Fe and Si are more than the aim of the present invention.

Fig. 2 shows the results of an investigation of the quality characteristics of extruded shapes that were produced by using such an aluminum alloy to produce 8-inch billets, homogenized for 12 hours at 480 ° C for 12 hours, and extruded with an extrusion press.

The shape of the extruded profile is a cross section with an external dimension of about 65 mm X 125 mm, a general thickness of 2 to 4 mm.

In the evaluation items shown in Fig. 2, the mechanical characteristics were measured by cutting out a piece of Japanese Industrial Standard J 〖S5.

The EA amount is the amount of energy absorbed when a load is applied.The extruded bar with a cross section with a cross section is cut into a length of 3 OO mm, a load is applied to a flat rigid, and the area of the load stroke diagram is shown. The amount of energy absorbed was measured.

SCC is a result of the stress corrosion cracking test, which evaluates the state of crack occurrence after immersing a test piece subjected to a predetermined bending stress in the following test solution.

Test liquid: 36 g of chromium oxide, 30 g of potassium dichromate, 3 g of sodium chloride, 50 ° C

In the table in Fig. 2, for example, “72, O” means that cracks occur after 72 hours of immersion. It means that it did not occur, and "22, XJ means that a crack occurred in 22 hours.

`` Eye-shaped speed J means the extrusion speed when extruded material with an eye-shaped cross section.For example, `` 6, 〇 '' can be extruded at a speed of 6 m. "2, XJ means that extrusion was possible at 2 mZ, but productivity was poor.

The profile temperature indicates the value obtained by measuring the surface temperature of the profile immediately after extrusion.

ET LT temperature means the preheating temperature of the billet.

As a result, Examples 1 to 5 satisfied the target quality, and Comparative Examples 1 to 4 did not satisfy any of the items.

Fig. 3 is a graph showing the results of analyzing the relationship between proof stress and energy absorption based on the measurement results shown in Fig. 2.

It is natural that the energy absorption amount is low when the power resistance value is low, but it is clear that the energy absorption amount decreases rapidly when the power resistance value exceeds about 300 MRa. It is the result of.

This is due to severe cracking of the extruded profile during the process of increasing the load.

Therefore, in order to secure a high and stable impact energy absorption amount, it is better to control the 0.2% proof stress value within a range of 320 to 390 MPa.

The graph shown in FIG. 4 shows the result of analyzing the relationship between the resistance value and the amount of energy absorption with respect to the component amounts of Fe and Sί.

The plots exhibiting a resistance value of 350 MPa or more correspond to Examples 1, 2, and 3, and the plots of 320 MPa or less are values obtained from Comparative Examples 3 and 4.

It has been clarified that the Fe and Si components continue to affect the resistance value and, as a result, are factors that make the energy absorption unstable.

From the results shown in Fig. 2, the relationship between SCC (stress corrosion cracking resistance) and section temperature was solved. When analyzed, it is preferable to keep the temperature within the range of 500 to 540 ° C. Industrial applicability

When the aluminum alloy profile according to the present invention is used, high and stable toughness (energy absorption characteristics accompanying the cross-sectional deformation) can be obtained.

Therefore, the present invention can be applied to a member that absorbs collision energy at the time of a collision, such as a bumper reinforcement mounted in front of and behind a vehicle, or an impact beam (side beam) mounted in a vehicle door.

In particular, in the case of a pump-in line hose, it is necessary to design so that a predetermined collision energy is absorbed and an air pack or the like is activated when an excessive impact is applied.

In such a field, product design becomes difficult if the amount of energy absorption is not stable. However, if the shock absorbing member according to the present invention is applied, the amount of energy absorption can be accurately grasped in advance, and airbags and other such devices can be used. It is easy to set operating conditions.

Claims

The scope of the claims

1.Zn: 5.6 to 6.6 wt%, Mg: 0.75 to 1.10 wt%, Cu: 0.10 to 0.25 wt%, Mn: 0. 0 5 to 0.20 wt%, Cr: 0.03 to 0.15 wt% .Zr: 0.10 to 0.25 wt%, Si: 0.02 to 0. Each component is controlled within the range of 10 wt% and Fe: 0.05 to 0.17 wt%, and the balance is obtained by manufacturing using an aluminum alloy consisting of AI and unavoidable impurities. The extruded billet is extruded to obtain an extruded material with a hollow cross-section, and is subjected to artificial aging so that the 0.2% proof stress is in the range of 320 to 390 MPa. Shock absorbing member.

2. By controlling the temperature of the extruded material at the time of extrusion to be in the range of 500 to 540 ° C, the impact resistance according to claim 1 is excellent in stress corrosion cracking resistance. A shock absorbing member.

3. An automobile shock absorbing member using the shock absorbing member according to claim 1 or 2.