JP2017078199A - Aluminum alloy sheet for casing engine mount - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet for casing an engine mount good in all of drawing processability, bulging processability and bending processability.SOLUTION: There is provided an aluminum alloy sheet 3 containing Mg:2.0 to 4.0 mass% and the balance Al with inevitable impurities and having tensile strength in a direction parallel to a rolling direction of 170 MPa or more and Vickers hardness at a position P with 0.5 mm just below an apex of a cross section of a 90 degree V-shaped bending part with zero inside radius of 110 or less. There is provided an aluminum alloy sheet 3 for casing an engine mount preferably containing further at least one kind of Mn:0.5 mass% or less, Cr:0.35 mass% or less and Zr:0.35 mass% or less of 0.1 to 0.6 mass% as total of Mn, Cr and Zr if needed and desirably having surface crystal particle diameter of 95 μm or less.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an aluminum alloy plate used for manufacturing a casing (outer cylinder) of an engine mount for suspending an engine on a body of an automobile.

The engine mount is a member used for suspending the engine from the body. As shown in Patent Documents 1 and 2, an engine mount has a structure in which an elastic body (anti-vibration rubber) is installed in a metal casing. Many are used.
Conventionally, stainless steel has been used as a material for the casing of the engine mount. However, in recent years, application of an aluminum material (aluminum alloy plate) has been desired as part of weight reduction of the vehicle body.

  The casing of an engine mount is generally a rotating body, and many casings have a complicated longitudinal section. For example, in the case of a casing comprising a large-diameter portion and a small-diameter portion that are continuous via a step portion, and an outer flange formed at the end of the small-diameter portion, this can be manufactured from an aluminum alloy plate after multi-stage drawing. It is necessary to further perform the formation of a stepped portion by pipe (reducing diameter) processing, bending processing, stretch flange processing of the end portion, and the like. For this reason, the aluminum alloy plate for casings of the engine mount is required to have good workability that does not cause cracks in these processes and high strength that can withstand the weight and vibration of the engine.

  Among aluminum alloys, 5000 series (Al-Mg series) alloys have relatively good workability, high strength, and low cost, and are promising as materials for automobile parts that require deep drawing and the like in the manufacturing process. is there. For example, Patent Documents 3 and 4 describe Al—Mg alloy plates developed mainly as materials for automobile outer plates.

Japanese Utility Model Publication No. 60-118047 JP-A-6-94068 JP 2008-63623 A JP 2008-223054 A

When manufacturing the casing of the engine mount, a case where various severe plastic workings are applied to the Al—Mg alloy plate after a drawing process over a plurality of processes is assumed. For this reason, it is desirable that the Al—Mg-based alloy plate for casings of engine mounts has good stretchability and bending workability in addition to drawing workability.
On the other hand, the Al—Mg alloy plate described in Patent Document 3 is said to be excellent in drawing workability and overhang workability, but bending workability is not considered. Moreover, although the Al-Mg type alloy plate described in Patent Document 4 is considered to have excellent drawing workability, it does not take into account overhanging workability and bending workability.

  An object of the present invention is to provide an Al—Mg-based alloy plate that is excellent in drawing workability, overhang workability, and bending workability, and is suitable for manufacturing an engine mount casing.

The aluminum alloy plate (Al—Mg-based alloy plate) for casings of engine mounts according to the present invention contains Mg: 2.0 to 4.0% by mass, the balance is made of Al and inevitable impurities, and is parallel to the rolling direction. The tensile strength in the direction is 170 MPa or more, and the Vickers hardness at a position of 0.5 mm immediately below the apex of the cross section of the 90-degree V-bent portion having an inner radius of zero is 110 or less.
If necessary, the aluminum alloy plate may further contain at least one of Mn: 0.5% by mass or less, Cr: 0.35% by mass or less, Zr: 0.35% by mass or less, Mn, Cr and Zr. In total, it can contain 0.1-0.6 mass%. The aluminum alloy plate preferably has a surface crystal grain size of 95 μm or less.

The aluminum alloy plate according to the present invention has a Vickers hardness of 110 or less at a position of 0.5 mm immediately below the outer vertex of the cross section of the bent portion when performing 90-degree V-shaped bending with an inner radius of zero by the V-block method, Progress of work hardening is suppressed. For this reason, the aluminum alloy sheet according to the present invention has good drawing workability, overhang workability and bending workability (especially repeated bending workability), and it is necessary to apply more severe plastic working after multistage drawing. However, an engine mount casing can be manufactured without cracking.
Further, the aluminum alloy plate according to the present invention has a tensile strength in the direction parallel to the rolling direction of 170 MPa or more, and has a strength necessary for the casing of the engine mount.

It is a figure explaining the measuring test method (V block method) of a work hardening characteristic, (a) is a side view of the test piece etc. before V-shaped bending, (b) is a side view of the test piece etc. after V-shaped bending. FIG. It is a figure explaining the method (measurement location) of the measurement test of a work hardening characteristic, (a) is a front view of the test piece after V-shaped bending, (b) is a side view of the test piece after mechanical polishing. It is a figure explaining the method of the measurement test of repeated bending workability. It is a figure (micrograph) explaining the evaluation criteria of repeated bending workability.

Hereinafter, the aluminum alloy plate (Al—Mg alloy plate) according to the present invention will be described in more detail.
<Composition of aluminum alloy>
The aluminum alloy according to the present invention contains Mg: 2.0 to 4.0% by mass, the balance is made of Al and inevitable impurities, and if necessary, Mn: 0.5% by mass or less, Cr: 0 .35% by mass or less, Zr: 0.35% by mass or less, and 0.1 to 0.6% by mass in total of Mn, Cr and Zr.
Mg has the effect of improving the strength and drawing workability of the aluminum alloy plate. However, when the Mg content is less than 2.0% by mass, the strength is insufficient. When the Mg content is 2.3% by mass or more, the drawing processability is further improved. On the other hand, if it exceeds 4.0% by mass, work hardening tends to proceed, and in particular, the repeated bending workability of the aluminum alloy plate is lowered. Therefore, Mg content shall be 2.0-4.0 mass%. Preferably, the lower limit of the Mg content is 2.3% by mass and the upper limit is 2.8% by mass.

  Mn, Cr, and Zr have the effect of improving the strength of the aluminum alloy plate and preventing the crystal grains of the aluminum alloy plate from becoming coarse. If the total content of Mn, Cr and Zr is 0.1% by mass or less, the effect is insufficient. On the other hand, the Mn, Cr and Zr contents individually exceed 0.5% by mass, 0.35% by mass and 0.35% by mass, respectively, or the total content of Mn, Cr and Zr is 0.6% by mass. When it exceeds, work hardening will progress easily and the overhang workability and bending workability of an aluminum alloy plate will fall. Therefore, the contents of Mn, Cr and Zr are 0.5% by mass or less, 0.35% by mass or less and 0.35% by mass or less, respectively, and the total content of Mn, Cr and Zr is 0.1 to 0%. .6 mass%. Preferably, Cr content shall be 0.1-0.35 mass%. In addition, the effect | action (strength improvement effect) which Cr and Zr exert on work hardening of an aluminum alloy plate is about twice Mn when compared with the same content.

When Si exceeds 0.3% by mass among inevitable impurities, a Mg—Si-based coarse intermetallic compound is generated, and the workability of the aluminum alloy plate is lowered. Moreover, the amount of solid solution Mg falls and the intensity | strength of an aluminum alloy plate falls. Accordingly, the Si content is set to 0.3% by mass or less.
Similarly, when Fe exceeds 0.4 mass%, an Al—Fe based coarse intermetallic compound is generated, and the workability of the aluminum alloy plate is lowered. Therefore, the Fe content is 0.4% by mass or less.
Of impurities other than Si and Fe, Cu is 0.1% by mass or less, Zn and Ti are 0.2% by mass or less, preferably 0.1% by mass or less, and B, Ni, Sn, In, and Ga are Each is 0.05 mass% or less, and the total is 0.15 mass% or less.

<Characteristics of aluminum alloy plate>
The aluminum alloy plate according to the present invention has a Vickers hardness of 110 or less at a position of 0.5 mm immediately below the outer vertex of the cross section of the bent portion when 90-degree V-shaped bending with an inner radius of zero is performed by the V-block method. Despite severe bending by the V-block method, the Vickers hardness after processing is low, which means that the progress of work hardening is suppressed in the aluminum alloy plate according to the present invention. In manufacturing an engine mount casing, for example, when it is necessary to add plastic processing after multistage drawing, it is necessary that work hardening is not too large. When this Vickers hardness is 110 or less, the aluminum alloy plate exhibits good stretchability and repetitive bending workability, and after multistage drawing, for example, formation of a stepped portion by diameter reduction processing, bending processing, extension flange at the end Even when processing or the like is performed, generation of cracks due to work hardening is prevented.
The aluminum alloy plate according to the present invention has a tensile strength in the direction parallel to the rolling direction of 170 MPa or more. Thereby, the casing of an engine mount which is strong and lightweight can be manufactured.

<Crystal structure of aluminum alloy plate>
The average crystal grain size (plate surface) of the aluminum alloy plate according to the present invention is preferably 95 μm or less. When the average crystal grain size is 95 μm or less, the generation of wrinkles is suppressed in bending. In order to make the average crystal grain size 95 μm or less, the total content of Mn, Cr and Zr in the aluminum alloy is preferably 0.1% by mass or more.

<Method for producing aluminum alloy plate>
The method for producing an aluminum alloy plate according to the present invention may be a conventional method, and includes, for example, semi-continuous casting (DC (direct chill) casting), homogenization treatment, hot rolling, cold rolling, and finish annealing. .
The homogenization treatment is preferably performed within a range of 480 to 550 ° C. When the homogenization temperature is lower than 480 ° C., a coarse Mg—Si intermetallic compound is precipitated, which becomes a starting point of cracking during processing. On the other hand, when the homogenization treatment temperature is higher than 550 ° C., the amount of solid solution Mg increases, work hardening is easy, and workability is lowered. What is necessary is just to select a homogenization processing time suitably between 1 to 24 hours.

In the hot rolling, the final plate thickness is set so that a predetermined processing rate is obtained in the subsequent cold rolling. In cold rolling, the larger the processing rate, the smaller the crystal grain size after finish annealing, and the generation of wrinkles during bending is suppressed, so the processing rate is 50% or more.
The finish annealing is preferably performed in the range of 300 to 480 ° C. If the final annealing temperature is lower than 300 ° C., recrystallization is insufficient and cracks are likely to occur during processing, and if it is higher than 480 ° C., the recrystallized grains are coarsened and repeated bending workability is reduced (wrinkles are generated). What is necessary is just to select finish annealing time suitably in 1 to 24 hours.
The aluminum alloy plate manufactured by this manufacturing method is an annealed material (type: O material), and equiaxed crystals (aspect ratio is 1.2 or less) of recrystallized grains are observed on the plate surface.

Hereinafter, examples in which the effects of the present invention have been confirmed will be specifically described in comparison with comparative examples that do not satisfy the requirements of the present invention. In addition, this invention is not limited to this Example.
An aluminum alloy having a composition shown in Table 1 (Si and Fe contained as inevitable impurities) was dissolved, and an ingot having a thickness of 600 mm was produced using a semi-continuous casting method. After chamfering the surface layer of this ingot, and performing a homogenization treatment under conditions of 510 ° C. × 4 hours (No. 1 to 18) or 550 ° C. × 4 hours (No. 19), hot rolling is performed, The plate thickness was 8.0 mm. Subsequently, the hot-rolled material was cold-rolled, wound up as an aluminum alloy plate (coil) having a thickness of 3.0 mm, and subjected to finish annealing at 360 ° C. for 4 hours.

No. For each of the aluminum alloy plates 1 to 19, the crystal structure of the surface (average crystal grain size, aspect ratio), work hardening characteristics, tensile strength, overhang workability, drawing workability, and bending workability (repetitive bending workability) Was measured as follows. The results are shown in Table 1.
(Average crystal grain size)
The average crystal grain size on the surface was determined by the intercept method. No. A test piece was cut out from each of the aluminum alloy plates 1 to 19, and the surface was mechanically polished, etched with an electrolytic solution, washed with water and dried, and then a structure photograph of the surface was taken 100 times with an optical microscope (each test piece 5 views each). The measurement line length in the section method was uniformly 0.95 mm, and the number of measurement lines was three for each visual field in the rolling parallel direction and the rolling perpendicular direction. The total of the measurement line lengths of the five visual fields is 0.95 × 3 × 5 mm in both the rolling parallel direction and the rolling perpendicular direction. From this measurement line length and the number of crystal grains completely traversed by 3 × 5 measurement lines, the average crystal grain size A in the rolling parallel direction and the average crystal grain size B in the direction perpendicular to the rolling are obtained, and the average value thereof. (A + B) / 2 was defined as the average crystal grain size of the surface.
(aspect ratio)
The aspect ratio of the surface crystal grains was calculated by A / B.

(Work hardening characteristics)
No. A rectangular test piece having a width of 20 mm and a length of 50 mm was sampled from the aluminum alloy plates 1 to 19 (the length direction is the direction parallel to the rolling), and as shown in FIGS. As the direction perpendicular to rolling, 90-degree V-bending with an inner radius of zero was performed by the V-block method. The test force was 1960N. In FIG. 1, 1 is a punch, 2 is a die, 3 is a test piece, punch 1 has a tip angle of 90 degrees and a radius of curvature of zero, and die 2 has a V-shaped angle of 90 degrees and a curvature radius at the bottom. Zero. Subsequently, the end surface of the test piece 3 after bending the V-shape is polished by a mechanical polishing method to expose a cross section (cross section perpendicular to the bending line) at a position 2 to 3 mm inward in the width direction from the original end surface, Smooth finish. In FIG. 2A, the position of the cross section exposed after mechanical polishing is indicated by a two-dot chain line, and the material polished (removed) by the mechanical polishing method is indicated by oblique lines. Subsequently, the Vickers hardness of the cross section was measured according to JIS-Z2244 (2009) with a test force of 0.1N. As shown in FIG. 2 (b), the measurement location was a position P that was 0.5 mm inside from the outer vertex of the test piece 3 after V-bending and mechanical polishing.

(Tensile strength)
No. JIS No. 5 tensile test specimens were taken from 1 to 19 aluminum alloy sheets so that the longitudinal direction was parallel to the rolling direction, and the tensile test was performed in accordance with JIS-Z2241 (2011) to measure the tensile strength. did.
(Overhang processability)
In accordance with JIS-Z2247 (2006), no. Test pieces were sampled from 1 to 19 aluminum alloy plates and subjected to an Erichsen test to determine Erichsen values. In the evaluation of the overhang workability, an Erichsen value of 9.5 or more was evaluated as （(excellent), 9.0 or more and less than 9.5 was evaluated as ◯ (good), and less than 9.0 was evaluated as x (bad).

(Drawing workability)
No. Disks of various sizes were punched from 1 to 19 aluminum alloy plates, a cylindrical deep drawing test was performed, and a limit drawing ratio (LDR) was measured. The cylindrical drawing test was performed with a punch diameter of 40 mm and a wrinkle holding load of 1 ton. The drawability was evaluated as L (1.95) or higher (excellent), 1.85 or higher and lower than 1.95 as ◯ (good), and lower than 1.85 as x (poor).

(Bending workability)
The bending workability when repeatedly bending was evaluated assuming the above-described method for manufacturing the casing of the engine mount (multi-stage drawing, diameter reduction processing, bending processing, stretch flange processing). No. A rectangular test piece having a width of 20 mm and a length of 50 mm was taken from the aluminum alloy plates 1 to 19 (the length direction is the parallel direction of rolling), and the bending line was made perpendicular to the rolling perpendicular direction with respect to the test piece 4 to form a V block. The first 90 degree V-bending was performed by the method. The radius of curvature of the punch tip was 6 mm. The test piece 4 after the first 90-degree V-bending is shown in FIG. Subsequently, after the test piece 4 is bent back linearly as shown in FIG. 3B, the second 90 degree V-bending (bending of the bending) is similarly performed by the V-block method as shown in FIG. 3C. The direction was opposite to the first). The radius of curvature at the tip of the punch was 2 mm.
The surface of the outer apex portion of the test piece 4 (Fig. 3 (c)) subjected to the second 90 degree V-bending was observed with an optical microscope to check for the presence of cracks and wrinkles. Sex). As shown in FIG. 4 (a), the evaluation criteria are x (defective) when cracks were observed, and ○ when wrinkles were observed but cracks were not observed as shown in FIG. 4 (b). (Good), as shown in FIG. 4 (c), those in which no noticeable wrinkles were observed were marked as ◎ (excellent).

  As shown in Table 1, the alloy composition and work hardening characteristics (Vickers hardness) after 90-degree V-bending with zero inner radius satisfy No. 1 of the present invention. For Nos. 1 to 12, the tensile strength was 170 MPa or more, and all of the stretchability, drawability and repeated bending property were evaluated as ◎ or ○. No. Nos. 1 to 12 have surface textures consisting of equiaxed crystals of recrystallized grains, of which no. Nos. 1 to 9 and 12 were evaluated as ◎ for repeated bending workability.

On the other hand, the alloy composition or the work hardening characteristics (Vickers hardness) after 90-degree V-bending with zero inner radius do not satisfy the provisions of the present invention. For Nos. 13 to 19, the tensile strength was less than 170 MPa, and any of the overhanging workability, drawing workability, and repeated bending workability was evaluated as x. Specifically, it is as follows.
No. No. 13 has a low tensile strength because the Mg content is insufficient.
No. No. 14, the Mg content was excessive, the work hardening characteristics (Vickers hardness) after 90-degree V-shaped bending with an inner radius of zero did not satisfy the provisions of the present invention, and the repeated bending workability was evaluated as x.
No. No. 15, the Cr content was excessive, the work hardening property (Vickers hardness) after 90-degree V-bending with a zero inner radius did not satisfy the provisions of the present invention, and the repeated bending workability was evaluated as x.

No. No. 16 has a low tensile strength because the Mg content is insufficient.
No. No. 17 had an overhang workability of x because the total content of Mn, Cr and Zr was excessive.
No. No. 18, the Mn content and the total content of Mn, Cr, and Zr are excessive, and the work hardening characteristics (Vickers hardness) after 90-degree V-bending with an inner radius of zero do not meet the provisions of the present invention. Workability and repeated bending workability were evaluated as x.
No. No. 19 has a relatively high soaking temperature of 550 ° C., so that the work hardening characteristics (Vickers hardness) after 90-degree V-bending with an inner radius of zero do not satisfy the provisions of the present invention, and the repeated bending workability is × It was evaluated.

1 Punch 2 Die 3, 4 Test piece

Claims (3)

Mg: 2.0 to 4.0% by mass, the balance is made of Al and inevitable impurities, the tensile strength in the direction parallel to the rolling direction is 170 MPa or more, and the 90-degree V-bend portion with an inner radius of zero An aluminum alloy plate for a casing of an engine mount, wherein the Vickers hardness at a position 0.5 mm immediately below the top of the cross section is 110 or less. Further, at least one of Mn: 0.5% by mass or less, Cr: 0.35% by mass or less, Zr: 0.35% by mass or less, and 0.1 to 0.6 in total of Mn, Cr and Zr The aluminum alloy plate for an engine mount casing according to claim 1, wherein the aluminum alloy plate is contained by mass%. The aluminum alloy plate for casings of an engine mount according to claim 1 or 2, wherein the crystal grain size of the surface is 95 µm or less.