JP3349458B2 - Aluminum alloy extruded material for automobile body structural member and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is excellent in strength, shock absorption, spot weldability and surface treatment properties, and uses a recovered aluminum material such as aluminum casting waste and aluminum can waste as a raw material at a low cost. The present invention relates to an aluminum alloy extruded material for an automobile body structural member that can be manufactured and a method for manufacturing the same.

[0002]

2. Description of the Related Art Automobile structural members have complicated shapes.
Since there are many hollow members, and aluminum alloy materials are lighter and more suitable for extrusion molding than other materials, the use of extruded aluminum alloy materials as structural members for automobile bodies has been studied. The extruded material of this aluminum alloy has features such as light weight and high rigidity, and furthermore, it can absorb energy at the time of collision by itself crashing,
It is a suitable material because it can enhance safety. However, materials conventionally used for such aluminum alloy extruded materials are mainly 6000 series aluminum alloys such as 6063.
Since the 00 series aluminum alloy has relatively low strength and low impact absorption energy as compared with other materials, there is a problem that the material thickness needs to be increased. In addition, the spot weldability is low, requiring a very large current for spot welding in the assembly process of automobiles, lowering productivity, and degreasing and chemical conversion properties are poor when performing surface painting, etc., resulting in durability There was a problem that it was difficult to paint well. In particular, among the structural members of automobiles, those called body frame structural members such as side frames, rear frames, center pillars, side sills, and floor frames are fixed by spot welding or the like, and are simultaneously exposed to the external environment, and furthermore, such as muddy water. Since it is exposed to a corrosive environment, coating and the like are performed for the purpose of improving the corrosion resistance, so that it is an indispensable material from chemical conversion treatment.

[0003] However, materials having various properties required for automobile body structural members such as extrudability, strength, workability, spot weldability, and surface treatment properties required of aluminum alloys, and excellent recyclability are known. Had not been developed. (1) For example, Japanese Patent Application Laid-Open No. 58-31055 discloses Si
2.3-6 wt%, Mg 0.4-1.0 wt%, Mn
Containing 0.4-1.0 wt% and small amounts of Zn and Sn,
The balance consists of Al, strength, weldability, structural aluminum alloy with improved machinability is disclosed, but spot weldability is not enough, containing both Cu and Zn elements,
Reduces the melting temperature of aluminum alloy, spot weldability and chemical conversion treatment during painting pretreatment (adhesion of zinc phosphate)
This is greatly different from the present invention in that it is not an improvement of the present invention. (2) Also, JP-A-61-190051 discloses that 5-1
Fe containing 5 wt% Si and up to 1.0 wt% Mg, Fe
A method for producing an Al-based hollow extruded material using an Al alloy with a content of 0.5 wt% or less and Cu, Mn, etc. of 0.25 wt% or less is disclosed. An alloy with higher Si content and improved heat and wear resistance, used as a bar and thick extruded material for high-temperature exposed parts and sliding parts of automobiles, spot weldability and zinc phosphate adhesion The surface treatment properties such as properties are low, and the extrudability is also insufficient. Therefore, this material cannot be used as an extruded member for a vehicle body structure as in the present invention.

(3) Further, Japanese Patent Application Laid-Open No. 5-271834 discloses that Mg is 0.2 to 1.2 wt%, Si is 1.2 to 1.2 wt%.
2.6 wt%, and ｛Si (wt%)-Mg
An aluminum alloy is disclosed in which the value of (wt%) / 1.73 ° is more than 0.85 and less than 2.0, the balance is Al, the crystal grains are fine, and the artificial aging stability is stable. This is because the composition ratio of Mg and Si is higher than that of the stoichiometric composition.
On the side, Mg ₂ Si is an alloy which is easy to generate. These are only the compositions of Mg and Si in the composition of the conventional JIS 6N01 alloy and AA6005 alloy. The weldability and surface treatment properties are insufficient. (4) Furthermore, JP-A-8-25874 discloses that
0.5-2.5wt%, Fe 0.2-1.0wt
%, Zn 0.45 to 1.5 wt%, Cu 0.05 to
An aluminum alloy extruded material for an automobile structural member containing 1.0 wt% and Mn of 0.4 to 1.5 wt% is described. This extruded material is excellent in extrudability, strength, and surface treatment properties, but has a low electric resistance of the material and has a problem in spot weldability. That is, in spot welding of a mass production line of an automobile body structural member, the wear of the welding electrode is a problem, and as the electrode wear progresses, the structure of the weld becomes unstable,
Since the size of the nugget changes and the strength of the joint decreases, the electrodes must be replaced frequently, and the largest cause of disturbing the productivity of the mass production line is that the wear of the welding electrodes is related to the spot weldability. Was the problem. In recent years, the importance of recycling used products has been increasing in view of environmental issues and effective use of resources, and there is a movement to legislate the obligation to collect automotive parts. Various studies have been made. Above all, there is an urgent need to establish a technique for regenerating high-quality materials from collected aluminum cans and scraps of scrapped automobiles.

[0005]

Accordingly, the present invention provides
An object of the present invention is to provide an aluminum alloy extruded material for an automobile body structural member having excellent spot weldability, surface treatment properties such as chemical conversion property and degreasing property, high strength and ductility, and excellent shock absorption. I do. Another object of the present invention is to provide a method for producing an aluminum alloy extruded material for a vehicle body structural member having excellent spot weldability, surface treatment property and shock absorption. A further object of the present invention is to provide an extruded material for an automobile body structural member having the above-mentioned excellent properties, which can be produced by using aluminum can collection waste or automobile aluminum component waste as a raw material.

[0006]

Means for Solving the Problems The inventors of the present invention have made intensive studies in view of the above problems, and have found that an aluminum alloy having a specific composition is homogenized under specific conditions and then hot-rolled. It has been found that the above-mentioned problems can be solved by the extruded material obtained by the above method, and the present invention has been accomplished based on this finding. That is, the present invention relates to (1) Si2.
Exceeds 6 wt% (hereinafter simply referred to as wt%) and is 4.0.
% Or less, Mg exceeding 0.3% and 1.5% or less, Mn
0.3% to 1.2%, Zn 0.3% to 1.2%, Cu 0.2% to 1.2%, and Fe 0.1% to 1.5% An extruded material using an aluminum alloy containing the following, and the balance being Al and inevitable impurities, having a conductivity of 48% IACS or less and a melting start temperature of 570 ° C. or less, for an automobile body structural member. Aluminum alloy extruded material, (2) the aluminum alloy further contains 50 to 500 pp of Sr or Sb
The aluminum alloy extruded material for automobile body structural members according to (1), wherein the aluminum alloy ingot is homogenized at a billet temperature of more than 520 ° C. and 570 ° C. or less for 1 hour or more. After processing, exceeding 400 ° C and 520
(1) or (2), wherein after the homogenization treatment is carried out at a temperature of not more than 1 ° C. for 1 hour or more, cooling and reheating are performed, and hot extrusion is performed at a billet temperature of more than 330 ° C. and not more than 500 ° C. The method for producing an aluminum alloy extruded material for an automobile body structural member according to the above (4), wherein at least a part of the material sliding surface of the extrusion die has a ceramic coating. A method for producing an aluminum alloy extruded material, and (5) aluminum containing, in at least a part of the aluminum alloy ingot, more than 0.5% and less than 1.2% of Mn and more than 1.2% and less than 2.0% of Mg Can collection waste and Si over 2.5% 1
An object of the present invention is to provide an aluminum alloy extruded material for an automobile body structural member produced by the production method according to the above (3) or (4), wherein automobile aluminum parts scrap containing 4% or less is used.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum alloy used in the present invention is more than 2.6% of Si and not more than 4.0%, preferably 2.6-3.5%, and more than 0.3% of Mg and 1.5%.
Or less, preferably 0.3 to 0.8%, Mn more than 0.3% and 1.2% or less, preferably 0.3 to 0.8%,
More than 0.3% and 1.2% or less, preferably 0.3 to
0.8%, more than 0.2% Cu and less than 1.2%, preferably 0.2-0.8%, and more than 0.1% Fe and 1.5%
% Or less, preferably 0.1 to 1.0% or less.

The function of each element in the Al alloy material of the present invention will be described. Si enhances the strength of the Al alloy material, secures necessary elongation, and has the effect of increasing impact absorption energy. If the content is less than 2.6%, the effect is insufficient,
Exceeding 4.0% makes extrusion difficult. Here, the impact absorption energy refers to energy that can be absorbed by compression, elongation deformation, and the like. In the present invention, it is evaluated by the deformation energy up to breakage in a tensile test. This value is 0.035
Nm / mm ² or more preferably, 0.04 Nm / mm ² or more is more preferable. In addition, Mg forms an intermetallic compound with the above-mentioned Si, generates Mg ₂ Si, and has an effect of improving strength. If the amount of Mg is too small, the effect is insufficient, and if the amount is too large, the extrudability deteriorates. Mn increases strength and improves impact absorption energy. If the amount of Mn is too small, the effect is insufficient. If the amount is too large, a coarse crystallization phase of Al-Mn is generated, the impact absorption energy is reduced, and the extrudability is reduced. Zn lowers the melting point of the alloy and improves the spot weldability, and at the same time, increases the surface reactivity, thereby improving the surface treatment properties such as degreasing and chemical conversion properties. In a conventional aluminum alloy extruded material for an automobile structural member, when Zn is increased, the self-corrosion resistance is disadvantageously deteriorated. On the other hand, the surface coating is applied in the composition of the present invention, so that the allowable range of the self-corrosion resistance reduction is reduced. This has been prevented by the expansion. If the Zn content is too small, the spot surface treatment property is insufficient, and if it is too large, the corrosion resistance is reduced.
Cu increases the strength of the alloy and at the same time lowers the conductivity and melting point, thereby improving the spot weldability. In addition, it contributes to the improvement of the impact absorption energy due to the increase in the strength of the alloy. If the Cu content is too small, the effect is insufficient, and if it is too large, extrusion becomes difficult. Further, Fe has an effect of improving toughness by increasing the crystal grain size and increasing impact absorption energy. F
If e is too small, the effect is insufficient, and if it is too large, the extrudability deteriorates due to a coarse crystallization phase, and the impact absorption energy decreases.

In the present invention, the aluminum alloy may further contain 50 to 500 ppm of Sr or Sb, if necessary. This Sr or Sb has the effect of reducing the size of the Si particles of the aluminum alloy. If the amount of Sr or Sb is less than 50 ppm, the effect of miniaturization will be insufficient, and if it exceeds 500 ppm, the effect of miniaturization will be lost, resulting in a so-called overmodification state. Therefore, these elements are 50-500 pp
m, preferably about 50 to 300 ppm. Also, instead of Sr and Sb, for miniaturization of Si particles,
Although Na may be used, it is desirable to use Sr or Sb without using as much as possible because it causes cracking during hot extrusion. About 150 ppm of Na is sufficient at the maximum from the viewpoint of miniaturization treatment of Si particles, but it is necessary to use one part of the amount in consideration of hot cracking during extrusion. The aluminum alloy extruded material of the present invention has a conductivity of 48% IACS or less, preferably 46% IACS.
ACS or lower, and the melting start temperature is 570 ° C or lower, preferably 560 ° C or lower. Low electrical conductivity and low melting start temperature do not require a large current for spot welding in the body assembly process and can greatly improve the electrode life, so the welding quality of the spot weld and the productivity of the welding line In this case, an extruded material for an automobile body structural member capable of performing spot welding while maintaining the above conditions can be obtained.

The aluminum alloy extruded material for an automobile body structural member of the present invention is obtained by homogenizing an aluminum alloy ingot having the above-described composition under specific conditions, and then cooling and reheating.
It can be manufactured by performing hot extrusion at a predetermined temperature. At this time, the homogenization treatment is performed at a temperature of more than 450 ° C. and 520 ° C. or less for 1 hour or more.
A homogenization treatment for 1 hour or more at a billet temperature of 70 ° C. or less,
Or, at a billet temperature exceeding 520 ° C and not more than 570 ° C,
After the homogenization treatment for at least one hour, the temperature may be maintained at a temperature of more than 400 ° C. and at most 520 ° C. for one hour or more. By the homogenization treatment at a temperature exceeding 450 ° C., Mg ₂ Si precipitates, and the deformation resistance decreases. Further, when the homogenization treatment is performed at a high temperature exceeding 520 ° C., the Mn-based precipitate becomes coarse, the high-temperature deformation resistance in the presence of Mg is reduced, and the upper limit of the extrusion speed can be increased.
The homogenization treatment at a temperature exceeding 400 ° C. and not more than 520 ° C.
Mg ₂ Si can be precipitated to further reduce the deformation resistance, which further increases the upper limit of the extrusion speed. On the other hand, if the billet heating temperature is too low, the pressure will be excessive and extrusion will not be possible. If it is too high, melting occurs due to the heat generated during processing during extrusion.

The aluminum alloy extruded material for a vehicle body structural member of the present invention is characterized in that, in the production thereof, the extrusion speed can be made higher than in the conventional method. Further, it is preferable to apply a ceramic coating to a part or all of the material sliding surface of the extrusion die, because the sliding resistance is reduced and the upper limit of the extruded material speed can be improved by about 20%. The ceramic coating is more preferably applied to a portion having a clearance of at least 3 mm or less, or to the entire die surface. As described above, by subjecting an aluminum alloy ingot of a specific composition to a soaking treatment and an extrusion treatment at a specific temperature, the occurrence of cracks at the time of extrusion, an excessive extrusion load, and the like are improved, and the productivity is improved. The cause of cracking during extrusion is considered to be that the speed of each part is different due to the difference in metal flow, and that internal shear force acts inside the extruded profile, resulting in fracture due to the tension, especially hollow material with a middle pillar The possibility of cracking is high because the processing speed is generally large due to the large difference in speed between the parts, but according to the method of the present invention, such a shaped member can be manufactured at a high extrusion rate without cracking. it can.

In the alloy of the present invention, cracks are likely to occur during hot extrusion, which may degrade productivity. However, extrusion is performed at a speed determined from the relationship between the homogenization treatment and the shape of the extruded material described below. Thereby, cracks can be avoided. (V represents the extrusion speed (m / min) and T represents the billet temperature (° C.) at the start of the extrusion.) When the homogenization treatment is performed at a temperature of more than 450 ° C. and 520 ° C. for 1 hour or more Certain hollow materials: V <14000 / T Hollow materials without solid pillars and solid materials: V <20,000 / T When homogenization treatment is performed at a temperature of more than 520 ° C. and 570 ° C. or more for 1 hour or more Hollow with a middle pillar Material: V <15000 / T Hollow material without solid pillar and solid material: V <22000 / T After homogenizing treatment at a temperature of more than 520 ° C. and 570 ° C. or more for 1 hour or more, exceeding 400 ° C. and 530 In the case of holding for 1 hour or more at a temperature of not more than 0 ° C. Hollow material with a central pillar: V <16000 / T Hollow material and solid material without a central pillar: V <24000 / T As described above, the extrusion speed is: Excellent in order.

One of the features of the method for producing an aluminum alloy extruded material for an automobile body structural member of the present invention is that an aluminum layer of an aluminum can or a scrapped automobile can be recycled and used. Since the aluminum alloy used in the present invention contains a large amount of Si, Mn, and Zn, it is possible to recycle various metal scraps as raw materials. Recyclable scraps that can be used include, for example, collected aluminum cans and scraps of parts such as automobile engine scraps. Aluminum can scrap preferably containing more than 0.5% and less than 1.2% Mn and more than 1.2% and less than 2.0% Mg and automotive aluminum parts containing more than 2.5% and less than 14% Si Recycling material such as waste is used as part of the raw material. In this case, the recovery material is subjected to a purification treatment as needed, and these purification treatments can be carried out by a commonly used method such as an α solid solution separation treatment. Such a purification treatment method is known in the art, and is described in, for example, JP-A-7-54061 and JP-A-7-197140, and can be performed in accordance therewith. By using the above-mentioned waste, the impact absorption energy of the obtained member can be increased. In addition, these wastes are relatively easily available, which leads to cost reduction of members.

[0014]

Next, the present invention will be described in more detail with reference to examples. As shown in Tables 4 and 5, A shown in Table 1
The aluminum alloys having compositions I to I were soaked and extruded under the conditions I to VI shown in Table 3 to produce aluminum alloy extruded samples 1 to 15. After air cooling at the time of extrusion and aging treatment at 180 ° C. for 2 hours, the following characteristics were evaluated. The results are shown in Tables 4 and 5. In addition, ADC12Z, UBC, and AC4C used for AC of Table 1 were used.
The composition of H is as shown in Table 2, and the purification was performed by the α solid solution separation method. The test method for each characteristic is as follows. Tensile Test (Tensile Strength, Yield Strength, Elongation Value) Tensile strength, proof stress, and elongation value were determined by using an INS-5 type tensile tester at a tensile speed of 10 mm / min using a JIS No. 5 test piece. Impact Absorbing Energy The energy that can be absorbed by plastic deformation such as tension and compression of extruded profiles, and the deformation energy up to fracture in a tensile test was determined. Conductivity The conductivity was measured by an eddy current method using a measuring device adjusted with a standard test piece, and represented by IACS%.

Melting start temperature Determined by performing a thermal analysis by a DSC method at a heating rate of 20 ° C./min. Zinc Phosphate Adhesion In each step, the zinc phosphate treatment was performed using a commercially available chemical manufactured by Nippon Parker Rising, using a test piece with dimensions of 70 mm x 150 mm, after pretreatment for degreasing and surface conditioning. It was done in the procedure of doing. The treatment process is as follows: After degreasing at 43 ° C. × 2 min with a degreasing agent (trade name: FC-L4460), room temperature × 3 with a surface conditioner (trade name: PL-4040).
After 0 sec, the zinc phosphate treating agent (trade name: PB-L
3020), a zinc phosphate treatment was performed at 43 ° C. for 2 minutes. After the treatment was completed, washing and drying were performed, and the adhesion weight of zinc phosphate per unit area was measured.

Spot Weldability Spot welding is performed using a single-phase rectifier welder with 1% Cr-Cu.
Using R type electrode R = 150, pressing force 3923N
(400 kgf) at a welding current of 30 KA. In addition,
In spot welding, the welding force is held for a certain period of time, a welding current is applied during the holding of the welding force, and after the welding current is held for a certain period of time, the nugget part of the material is completely solidified even after the welding current is applied. Until the pressing, the pressure was maintained. Here, the time (squeeze time) until the welding current rises after the pressing force is applied is 35 cycles (0.70 s).
ec), the time for maintaining the constant current value and melting the material (weld time) is 12 cycles (0.24 sec), and the holding time after the current application is completed (hold time) is 15
Cycle (0.30 sec), welding 1 spot /
3 seconds, as a result, the tensile shear load is 3000
The point at which the value became kN or less was evaluated as the electrode life. Bending workability A 90-degree V-shaped bending (tip R: 2 mm) was performed. If no cracks were generated, it was evaluated as good.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

[0020]

[Table 4]

[0021]

[Table 5]

As is clear from the results of Tables 4 and 5,
Sample 10 as a comparative example has a low impact absorption energy and a short electrode life during spot welding. Further, the melting start temperature is high, the amount of zinc phosphate attached is small, and the surface treatment property is poor. Sample 11 has extremely poor tensile strength and proof stress, extremely low impact absorption energy, and is not practical in terms of mechanical properties such as strength. This sample 11 has a high conductivity and a high melting start temperature, a short electrode life at the time of spot welding, a zinc phosphate adhesion amount of 1.8 g / m ² or more,
g / m ² or more) is also extremely low at 0.75 g / m ² . Sample 12 has high tensile strength, elongation and impact absorption energy and good weldability, but has a low zinc phosphate adhesion of 1.65 g / m ² and is inferior in chemical conversion treatment. As described above, Samples 10 to 12 have problems such as low strength, impact absorption energy, weldability (electrode life during spot welding), or chemical conversion treatment. Samples 13 to 15 had remarkably poor extrudability. Samples 13 and 15 were broken at the center column of the hollow material, and sample 14 was not extrudable, and the desired extruded material could not be obtained. On the other hand, Samples 1 to 9 of the present invention have excellent tensile strength and elongation, high impact absorption energy, low electrical conductivity, and low melting start temperature. And the zinc phosphate adhesion amount showing surface treatment property is very excellent, showing a value of 1.87 to 2.44 g / m ² , furthermore, the electrode is less worn at the time of spot welding, the life of the electrode is longer, and the spot weldability is higher. Excellent.

[0023]

The aluminum alloy extruded material for an automobile body structural member of the present invention has low conductivity and low melting start temperature, so that the electrode is less worn during spot welding, the productivity of the assembling process can be improved, and the degreasing property can be improved. Since the chemical conversion treatment is good, the surface treatment is excellent, the strength is high, and the impact absorption energy is large. The extruded aluminum alloy is used as an automobile body structural member in applications requiring both spot weldability and surface treatment properties such as side frames, rear frames, center pillars, side sills, and floor frames. Further, according to the production method of the present invention, an extruded material having no crack at a high extrusion speed can be produced with high productivity. Further, the aluminum alloy extruded material for an automobile body structural member of the present invention,
It can be manufactured at high quality and at low cost using aluminum can collection waste and automobile aluminum parts waste.

Continued on the front page (72) Inventor Nobuaki Ohara 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd. (72) Inventor Noboru Hayashi 1-4-1 Chuo, Wako-shi, Saitama Honda Motor Co., Ltd. In the laboratory (58) Field surveyed (Int. Cl. ⁷ , DB name) C22C 21/00-21/18 C22F 1/04-1/057

Claims (5)

(57) [Claims] 1. Si exceeds 2.6 wt% and 4.0 wt%
Hereafter, Mg exceeds 0.3 wt% and 1.5 wt% or less.
n is more than 0.3 wt% and not more than 1.2 wt%;
More than 3 wt% and less than 1.2 wt%, Cu 0.2 wt%
Extruded material using an aluminum alloy containing more than 1.2 wt% and less than 0.1 wt% and more than 0.1 wt% and less than 1.5 wt% of Fe, with the balance being Al and inevitable impurities. Hereinafter, the melting start temperature is 570 ° C.
An aluminum alloy extruded material for an automobile body structural member, characterized by the following. 2. The extruded aluminum alloy material for an automobile body structural member according to claim 1, wherein said aluminum alloy further contains 50 to 500 ppm of Sr or Sb. 3. An aluminum alloy ingot is subjected to a homogenization treatment at a billet temperature of more than 520 ° C. and 570 ° C. or less for 1 hour or more, and after a homogenization treatment of holding at a temperature of 400 ° C. or more and 520 ° C. or less for 1 hour or more, 3. The method for producing an aluminum alloy extruded material for an automobile body structural member according to claim 1, wherein the extruded material is heated and cooled, and hot extruded at a billet temperature of more than 330 ° C. and not more than 500 ° C. 4. The method for producing an aluminum alloy extruded material for an automobile body structural member according to claim 3, wherein at least a part of the material sliding surface of the extrusion die has a ceramic coating. 5. The method according to claim 1, wherein at least a part of the aluminum alloy ingot has a Mn content of more than 0.5 wt% and less than 1.2 wt%.
g Aluminum can waste containing more than 1.2 wt% and less than 2.0 wt%, and more than 2.5 wt% Si and 14 wt%
%. Aluminum alloy extruded material for an automobile body structural member manufactured by the manufacturing method according to claim 3, wherein the aluminum alloy scrap containing automotive aluminum parts containing not more than 5% is used.