JP6223492B2 - Manufacturing method of aluminum alloy forgings for automobiles - Google Patents

Description

  The present invention relates to a method for manufacturing an aluminum alloy forging for automobiles such as a suspension arm.

  As a material for automobile parts such as suspension arms, a 6000 series aluminum alloy (sometimes referred to as “Al—Mg—Si series alloy”) defined in JIS is suitably used. The 6000 series aluminum alloy is also called a heat treatment type alloy and is subjected to a series of heat treatment (for example, T6 tempering) including solution heat treatment, quenching, and artificial aging treatment.

  In recent years, for aluminum alloy forgings for automobiles such as vehicles and automobile parts, weight reduction has been strongly desired for reasons such as reducing vehicle weight and improving fuel efficiency. In order to reduce the weight of aluminum alloy forgings for automobiles, it is necessary to increase the strength, and development of such materials is strongly desired.

  In order to increase the strength of aluminum alloy forgings for automobiles, many proposals have been made for solution heat treatment and artificial aging treatment among the heat treatments described above. However, at present, no such proposal has been made for quenching.

  Regarding quenching, for example, in Non-Patent Document 1, page 652, page 10.52, about quenching of aluminum alloy forgings, cooling water is excellent in cold water, but distortion due to residual stress during quenching. In order to prevent this, it is described that quenching with warm water of 50 to 60 ° C. or quenching with addition of a quenching agent is described.

Japan Light Metal Association Aluminum Technical Handbook Editorial Committee, “Aluminum Technical Handbook”, published by Karos Publishing Co., Ltd., June 16, 1985

  As described above, including Non-Patent Document 1, conventionally, quenching has not been a subject of consideration in further increasing the strength of automotive aluminum alloy forgings. That is, the aluminum alloy forged material for automobiles has room for improvement in order to further increase the strength with respect to the quenching conditions.

  This invention is made | formed in view of the said situation, and makes it a subject to provide the manufacturing method of the aluminum alloy forging material for motor vehicles which can provide high intensity | strength.

The manufacturing method of the aluminum alloy forgings for motor vehicles concerning this invention which solved the said subject melt | dissolves a raw material, adjusts a component, makes a 6000 series aluminum alloy, and casts an ingot after the said melting process. A casting process, a homogenization heat treatment process for performing a homogenization heat treatment on the ingot after the casting process, and a forging process for forging the ingot into an aluminum alloy forging material having a predetermined shape after the homogenization heat treatment process; A solution heat treatment step for performing a solution heat treatment on the aluminum alloy forged material after the forging step; a quenching step for quenching the aluminum alloy forged material after the solution heat treatment step; and the quenching step. Then, it was decided to perform quenching in which the quenching time was 1 to 5 minutes in the quenching step.
As described above, the method for manufacturing an aluminum alloy forged material for automobiles according to the present invention makes the quenching time shorter than the conventional method and has a predetermined range in which the strength analyzed in advance is high. Strength can be increased.

The method for producing an aluminum alloy forged material for automobiles according to the present invention is such that, in the quenching step, the surface area of the aluminum alloy forged material is SA and the cross-sectional area of the cross section parallel to the water for performing the quenching is SB. It is preferable to perform quenching in a posture where the value calculated by SB / SA is 0.0040 to 0.0400.
As described above, the method for manufacturing an aluminum alloy forged material for automobiles according to the present invention is hardened in a posture in which the value calculated by SB / SA falls within a predetermined range, so that quenching distortion hardly occurs. it can.

In the method for producing an aluminum alloy forged material for automobiles according to the present invention, the temperature of water for quenching is preferably 30 to 70 ° C.
As described above, the method for producing an aluminum alloy forged material for automobiles according to the present invention sets the temperature of the water for quenching within a predetermined range, so that the strength of the aluminum alloy forged material for automobiles can be more reliably increased. .

  The method for producing an automotive aluminum alloy forging according to the present invention can impart high strength to an automotive aluminum alloy forging.

It is a conceptual diagram explaining the value computed by SB / SA when the surface area of the aluminum alloy forging material for motor vehicles is SA and the cross-sectional area of a cross section parallel to the water for quenching is SB. It is a conceptual diagram explaining the value computed by SB / SA when the surface area of the aluminum alloy forging material for motor vehicles is SA and the cross-sectional area of a cross section parallel to the water for quenching is SB. It is the schematic which shows an example of the suspension arm which can apply the manufacturing method of the aluminum alloy forging material for motor vehicles concerning this invention. It is the schematic which shows an example of the suspension arm which can apply the manufacturing method of the aluminum alloy forging material for motor vehicles concerning this invention. It is a schematic explanatory drawing which shows the shape of an I-type arm, and the position of test site | part T1. It is explanatory drawing explaining a mode that it is confirmed whether the quenching distortion has arisen in the Example. It is explanatory drawing explaining a mode that it is confirmed whether the quenching distortion has arisen in the Example.

Hereinafter, the form for enforcing the manufacturing method of the aluminum alloy forge for vehicles concerning the present invention is explained in detail.
The method for producing an aluminum alloy forged material for automobiles according to the present embodiment (hereinafter also referred to as “the present method”) includes a melting step of preparing a 6000 series aluminum alloy by dissolving raw materials and adjusting components; After the melting step, a casting step for casting the ingot, a homogenization heat treatment step for performing a homogenization heat treatment on the ingot after the casting step, and an aluminum alloy forging material having a predetermined shape after the homogenization heat treatment step ( Hereinafter, a forging process forging to “Al alloy forging material”, a solution heat treatment process for performing solution heat treatment on the Al alloy forging material after the forging process, and a solution heat treatment process, It includes a quenching process for quenching the Al alloy forging material, and an artificial aging treatment process for performing an artificial aging treatment after the quenching process, and the quenching time is 1 to 5 minutes in the quenching process. Also It is.

Thus, since this method sets the quenching time in the quenching process to 1 to 5 minutes, the strength of the Al alloy forging can be increased.
When the quenching time is less than 1 minute, the quenching is not sufficiently performed, so that the strength cannot be increased. On the other hand, when the quenching time exceeds 5 minutes, not only the quenching effect is saturated but also the strength tends to be slightly reduced. Accordingly, the quenching time is 1 to 5 minutes. From the viewpoint of increasing the strength, the quenching time is preferably 4 minutes or less, and more preferably 3 minutes or less.

In this method, the temperature of water for quenching is preferably 30 to 70 ° C. When the temperature of water is within this range, the strength of the Al alloy forging can be increased more reliably. In addition, it is preferable to perform the temperature of water within the said temperature range within the temperature +5 degreeC suitable for the alloy type of 6000 series aluminum alloy. For example, in the case of an Al alloy having chemical components shown in Table 1 to be described later, it is preferably performed at 40 to 45 ° C. In the case of other alloy types, an appropriate temperature can be easily grasped by appropriately conducting experiments within the above temperature range.
The temperature of the water is preferably controlled by a computer or the like by installing one or a plurality of thermometers in the quenching tank for quenching. When the temperature of water exceeds 70 degreeC, it is preferable to add water with low temperature newly and to lower temperature. Moreover, when the temperature of water is less than 30 degreeC, it is preferable to raise temperature with a heater.

  Moreover, it is preferable that the water for carrying out quenching is bubbled in this method. Thus, when water is bubbled, soft spots can be made difficult to occur. Here, the “soft spot” refers to a poorly quenched portion and an unquenched portion that are partially (locally) generated in the Al alloy forged material. Soft spots tend to occur when a large number of Al alloy forgings are arranged densely or stacked. The portion where the soft spot is generated has a lower strength than other normal quenched portions, and hinders homogeneity such as mechanical properties of the Al alloy forged material.

  As described above, soft spots are likely to occur when a large number of Al alloy forgings are arranged densely or stacked. It is considered that this is because, when the interval between adjacent Al alloy forgings is narrow, the water heated by cooling the Al alloy forging is difficult to move from that position. Therefore, it is not necessary to perform bubbling if the interval between adjacent Al alloy forgings is sufficiently open during quenching, but it is preferable to perform bubbling otherwise. Bubbles generated by bubbling have the property of moving upward regardless of the distance between adjacent Al alloy forgings. The bubbles move with water as they move upward. Therefore, even if the space | interval of adjacent Al alloy forging materials is narrow, circulation of water can be promoted. As a result, soft spots can be made difficult to occur as described above.

Bubbling can be performed by an exhaust part such as an air nozzle or a sparger installed in the lower part of the quenching tank, an air pipe connected to the exhaust part, and an air pump connected to the air pipe. In addition, an exhaust part blows air into the water in a quenching tank, and generates a bubble. The air pipe supplies air to the exhaust part. The air pump applies pressure to supply air to the air piping. These are conventionally known ones and can be carried out under general conditions.
The bubbling air pressure is preferably ² to 10 kg / cm ² , for example, but is not limited to this as long as soft spots can be hardly generated.

Further, in this method, when the surface area of the Al alloy forging is SA and the cross-sectional area of the cross section parallel to the water for quenching is SB, the value calculated by SB / SA is 0.0040 to It is preferable to perform quenching in an attitude of 0.0400. 1A and 1B illustrate values calculated by SB / SA when the surface area of the Al alloy forging is SA and the cross-sectional area of the cross-section CS parallel to the water for quenching is SB. It is a conceptual diagram. FIG. 1A shows an attitude in which the value calculated by SB / SA is 0.0040 to 0.0400, that is, an Al alloy forged material is in a standing state as much as possible. Moreover, FIG. 1B has shown that the attitude | position which the value calculated by SB / SA does not become 0.0040-0.0400, ie, has made the Al alloy forging material lie down.
By setting the value calculated by SB / SA within the above range, quenching distortion can be made difficult to occur.

It is easy to grasp the throwing angle θ of the Al alloy forging material into water on the basis of the central axis C of the Al alloy forging material. When the value calculated by SB / SA is 0.0040 to 0.0400, the throwing angle θ into the water with respect to the central axis C is in the range of 0 to 45 °.
In addition, when a part of the Al alloy forging material is bent at a predetermined angle, the longer one of the lengths of the central axes C connecting the respective end portions based on the bent portion is used as a reference. Is preferred.

  The surface area of the Al alloy forged material and the cross-sectional area of the cross section parallel to the water for quenching can be easily grasped by, for example, reading the shape of the Al alloy forged material with a 3D scanner and analyzing it with arbitrary software. Can do. For example, if the shape is designed by 3D-CAD (Computer-Aided Design) or the like, it can be easily grasped from the 3D-CAD.

  When quenching is performed in the quenching tank, a holder for holding and supporting the solution heat-treated Al alloy forged material is used, or it is placed in a cage (a case of a wire mesh). Therefore, when quenching, it is preferable to devise the shape of the holder used or adjust the direction of the ridge so that the value calculated by SB / SA falls within the above-described range.

  The aluminum alloy used in this method is preferably a 6000 series aluminum alloy. If it does in this way, it will become possible to provide automobile parts which have high intensity, for example. Specific examples of the 6000 series aluminum alloy include 6061 alloy, 6110 alloy, 6111 alloy, 6003 alloy, 6151 alloy, 6061 alloy, 6N01 alloy, 6063 alloy, 6082 alloy, and 6182 alloy.

  Moreover, as an Al alloy forging material to which this method can be suitably applied, for example, a suspension arm can be cited. That is, this method can be suitably applied as a suspension arm. The suspension arm is a part that connects the wheel and the vehicle body, and is a device that prevents the impact and vibration from the road surface from being transmitted directly to the passenger compartment. Suspension arms include strut-type and double wishbone-type suspension upper and lower arms, as well as trailing arms and swing arms. The method can be applied to any of these arms. This method can be suitably applied particularly to suspension arms called I-shaped I-shaped arm 1 (see FIG. 2A) and L-shaped L-shaped arm 2 (see FIG. 2B). 2A and 2B are schematic views showing an example of a suspension arm to which the present method can be applied. The present method can also be suitably applied to a suspension arm called an A-shaped arm (not shown) having an A shape.

  In the present invention, each process other than the quenching process, that is, the melting process, the casting process, the homogenization heat treatment process, the forging process, the solution heat treatment process, and the artificial aging treatment process, produces an Al alloy forging material. It can be implemented with general equipment and conditions.

Next, the method will be described in more detail in comparison with Examples and Comparative Examples.
Using a 6000 series aluminum alloy having a chemical composition (mass%) shown in Table 1, a melting step, a casting step, a homogenizing heat treatment step, and a forging step were sequentially performed to forge the I-arm. Then, solution heat treatment was performed on the forged I-shaped arm at 550 ° C. × 240 minutes. Quenching was performed with the quenching time shown in 1-8. The quenching water temperature was set to 40 ° C., and the quenching water amount was set to a sufficient amount so that the temperature rise was 5 ° C. or less after the solution I heat treatment was performed. Quenching was performed such that the center temperature of the maximum thickness portion of the I-type arm was 40 to 45 ° C. The center temperature was confirmed by drilling a hole up to the center of the maximum thickness portion of the I-type arm and inserting a thermocouple into the hole (not shown in Table 2).

In Table 2, No. After quenching at each quenching time shown in 1 to 8, an artificial aging treatment at 175 ° C. × 8 hours was performed. No. manufactured in this way. From test part T1 (refer to Drawing 3) of I type arm concerning 1-8, a test piece is produced based on JISZ2241: 2011, and tensile strength (MPa) and proof stress are done by performing a metallic material tensile test. (MPa) and elongation (%) were measured.
Those having a tensile strength of 390 MPa or more were judged to have high strength.
Table 2 shows the results of the metal material tensile test along with the quenching time. In Table 2, the underline indicates that the requirement of the present invention is not satisfied.

  As shown in Table 2, no. The I-type arm according to Nos. 2 to 5 has a quenching time of 10 to 30 minutes. Since it was as short as 1-5 minutes compared with 6-8, tensile strength and proof stress became high (all are Examples). In particular, no. Since the I-type arms according to 2 to 4 had a reasonably short quenching time, the tensile strength and the yield strength were higher.

In contrast, no. Since the I-type arms according to Nos. 1 and 6 to 8 did not satisfy the requirements of the present invention, the tensile strength and the yield strength did not increase (both were comparative examples).
Specifically, no. Since the I-type arm according to No. 1 had a quenching time that was too short, the center temperature did not drop to 40 to 45 ° C., and coarse precipitates appeared and the strength could not be increased. Therefore, no. The I-arm according to 1 did not have high tensile strength and yield strength.
No. Since the I-arms according to 6 to 8 had a quenching time that was too long, precipitation that did not contribute to the strength occurred, and the amount of precipitation in the artificial aging treatment step was reduced, so the strength was not increased. Therefore, no. The I-type arms according to 6-8 did not have high tensile strength and yield strength.

Moreover, the relationship between the attitude | position of the I-type arm and the L-type arm at the time of quenching, and quenching distortion was verified as follows.
No. in Table 3 As shown in 9 to 32, six types of suspension arms (three types of I-type arms and three types of L-type arms) having different surface areas of the Al alloy forged material were prepared.
In addition, No. As described above, the suspension arms according to 9 to 32 are manufactured by sequentially performing a melting process, a casting process, a homogenizing heat treatment process, and a forging process using a 6000 series aluminum alloy having the chemical composition (mass%) shown in Table 1. did.
Next, no. The suspension arms according to 9 to 32 were subjected to a solution heat treatment at 550 ° C. for 240 minutes in the same manner as described above. After quenching with the quenching time shown in 3 (that is, after quenching for 2 minutes), an artificial aging treatment at 175 ° C. × 8 hours was performed. During quenching, as shown in Table 3, the water injection angle θ for quenching was set to 0 to 45 °.
Then, the shape of each suspension arm is read with a 3D scanner and analyzed with arbitrary software, and the surface area SA of the suspension arm and the cross-sectional area SB of the cross section parallel to the water for quenching at each charging angle θ are obtained. Calculated. Further, SB / SA at each charging angle θ was calculated from the calculated SA and SB.

  Subsequently, No. manufactured as mentioned above was carried out. It was confirmed whether or not quenching distortion occurred in the suspension arms according to 9 to 32 using the predetermined jig 3 and dial gauge 4 shown in FIGS. 4A and 4B, respectively. “◯” indicates that the quenching distortion is within a tolerance range (based on a tolerance of 1.0 mm), and “x” indicates a tolerance exceeding the tolerance range. Table 3 shows the results.

As shown in Table 3, no. In the suspension arms according to 10 to 25 and 27 to 30, since the ratio SB / SA of the cross-sectional area SB of the cross section parallel to the water for quenching with respect to the surface area SA of the suspension arm was appropriate, It was within an acceptable range.
No. In the suspension arms according to 9, 26, 31, and 32, the ratio SB / SA of the cross-sectional area SB of the cross-section parallel to the water for quenching the surface area SA of the suspension arm was not appropriate, so that the quenching strain was a tolerance. It was beyond the acceptable range.
In addition, No. The tensile strength, proof stress, and elongation of any suspension arm according to Nos. 9 to 32 are also shown in Table 2. Same as 3.

SA Surface area of aluminum alloy forging SB Cross section of cross section parallel to water for quenching CS Cross section of water parallel to quenching

Claims (3)

A melting step of dissolving raw materials to adjust the components to obtain a 6000 series aluminum alloy;
After the melting step, a casting step for casting the ingot;
A homogenization heat treatment step of performing a homogenization heat treatment on the ingot after the casting step;
After the homogenization heat treatment step, forging step of forging the ingot into a predetermined shape aluminum alloy forging,
A solution heat treatment step for performing a solution heat treatment on the aluminum alloy forging material after the forging step;
After the solution heat treatment step, a quenching step of quenching the aluminum alloy forging material,
Including an artificial aging treatment step of performing an artificial aging treatment after the quenching step,
A method for producing an aluminum alloy forged material for automobiles, wherein quenching is performed in the quenching step for 1 to 5 minutes.   In the quenching step, when the surface area of the aluminum alloy forged material is SA and the sectional area of the cross section parallel to the water for quenching is SB, the value calculated by SB / SA is 0.0040 to The method for producing an aluminum alloy forged material for automobile according to claim 1, wherein quenching is performed in an attitude of 0.0400.   The temperature of the water for performing the said quenching is 30-70 degreeC, The manufacturing method of the aluminum alloy forging material for motor vehicles of Claim 1 or 2 characterized by the above-mentioned.

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