JPH06340953A - Aluminum stock for disk wheel rim - Google Patents

Abstract

PURPOSE:To develop Al alloy stock having excellent characteristics as a disk wheel rim by forming the molten metal of an Al alloy having a specified compsn. into a sheet material by a direct casting method, thereafter subjecting it to skinpass rolling according to necessary and executing annealing at a specified temp. CONSTITUTION:The molten metal of an Al alloy having a compsn. contg., by weight, 2.0 to 3.5% Mg and at least one kind of 0.08 to 0.8% Mn and 0.08 to 0.8% Cr, furthermore contg. 0.002 to 0.1% Ti and 0.10 to 0.20% Si and contg <0.25% Fe, <0.10% Cu and <0.20% Zn as impurities is directly cast into a sheet material having 4 to 6mm thickness by a direct casting method. This sheet made of the Al alloy is subjected to skinpass rolling at <=5% rolling ratio according to necessary and is thereafter annealed at 200 to 450 deg.C. The Al alloy stock excellent in fatigue strength, impact resistance, formability, corrosion resistance and surface glossiness and suitable as the Al stock for the rim of a disk wheel can be obtd.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an aluminum material for disc wheel rims. Specifically, the present invention is characterized in that a molten aluminum-based alloy having a specific composition is formed into a cast plate having a thickness of 4 to 6 mm by a direct casting rolling method without hot and cold rolling. The present invention relates to an aluminum material used for a rim portion of a two (2) piece or three (3) piece disk wheel having excellent mechanical strength, moldability, corrosion resistance and gloss.

[0002]

2. Description of the Related Art In recent years, as the weight of automobiles has been reduced, the use of aluminum for each component has been studied. Among them, the use of aluminum for disc wheels has been emphasized as a measure to reduce unsprung weight. One (1) piece wheel, two piece or three piece in which a rim obtained by forming an aluminum alloy plate and a disc made by forging or casting are joined by welding or tight binding
Peace wheels are manufactured.

Prior to describing the present invention in further detail,
The manufacturing process and required characteristics of the two-piece and three-piece wheels will be described. The two-piece wheel consists of a rim portion and a disc portion. As a method of manufacturing the rim portion, a method is generally used in which a strip-shaped plate is formed into a cylindrical shape, both ends thereof are joined by welding, and then roll forming is performed, and there is also a method of forming an extruded pipe. The disc portion is generally manufactured by casting or hot forging. The two are joined by welding to form a disc wheel.

On the other hand, the three-piece wheel is composed of two rims on the front and rear sides and a disc.
The rim part is manufactured by spinning or pressing a disk on both the front side and the rear side, and then punching out the center part, and combining these with the disk part and joining them by welding or tight binding to form a disk wheel. As described above, both the two-piece wheel and the three-piece wheel are subjected to strong plastic working at the time of forming the rim portion, so that the aluminum material for the disc wheel rim is required to have excellent formability.

Furthermore, the automobile standard (JASO C-60
Based on 8), the disc wheel is required to have flexural moment durability, radial load durability, impact resistance, and airtightness of the rim, and excellent fatigue strength and impact strength are required. . The light alloy disc wheel is a very fashionable product, and its excellent surface gloss is an important factor for improving the commercial value. In addition, since it is exposed to a corrosive environment, it is one of the required properties that the material has excellent corrosion resistance.

[0006] Conventionally, as a method for producing an aluminum material for a disc wheel rim, a continuous casting method using a stationary annular mold, in particular, a slab is cast by a vertical type semi-continuous casting machine, followed by hot rolling and cold rolling. The method of going through a rolling process was common. (Hereinafter, a rolled plate manufactured by this method is referred to as a DC plate.) Conventionally, a DC plate has been mainly used as a material that sufficiently satisfies the excellent quality defined by automobile standards. The material was not used.

The rolling process is indispensable in the production of DC plate, and the hot rolling process homogenizes the metal structure and improves impact resistance, airtightness, etc., while the cold rolling process causes hardness due to working strain. Is added to the material to improve fatigue strength, bending strength, durability and the like. As described above, the DC plate is excellent for use in automobile parts, but has a drawback in that the cost and time required for the rolling process are long.

On the other hand, a so-called direct casting and rolling method is known as one of the methods for producing an aluminum alloy sheet used for purposes other than automobile parts. The manufacturing method is to supply the molten metal into a driving mold composed of a pair of cooled rotating casting rolls, a pair of running endless track-shaped molds, etc., and continuously form a cast plate without rolling. It is a manufacturing method. Direct casting and rolling method is "rolling" in its name
However, since there is no rolling process in the ordinary sense, for example, there is no large rolling process with a rolling ratio of 20% or more, it is also a significantly economical method compared to a DC plate.

In the direct casting and rolling method, alloy components are liable to be forced to form a solid solution in the microstructure and the second phase particles are liable to be fine, so that impact resistance, formability, fatigue strength, glossiness, and It is said that an aluminum alloy plate (direct cast rolled plate) having good corrosion resistance can be obtained. However, in spite of the fact that the production method is a method of giving an aluminum alloy sheet having excellent properties as described above, the quality of the obtained alloy sheet is actually significantly affected by the molten metal composition and other casting conditions. However, it was not possible to obtain the same quality as the DC plate. Further, the relationship between the casting conditions and the quality of the cast plate has not been fully clarified yet.

[0010]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted extensive studies to find out a method for producing an alloy sheet which is excellent as a material for a disc wheel rim, and as a result, made use of the characteristics of a direct cast rolled sheet to obtain a specific composition. Finding a new rim material to replace DC plate that can solve the conventional problems and meet the above-mentioned severe requirements as a material for disk wheel rims by using molten aluminum base alloy and combining with annealing treatment Has reached the present invention.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to more economically provide an aluminum material for disc wheel rims having excellent quality, the purpose of which is to provide Mg.
2.0-3.5 wt% and Mn 0.08-0.8 wt%
And at least one of 0.08 to 0.8 wt% Cr, 0.002 to 0.1 wt% Ti, and 0.10 to Si
0.20 wt% and Fe 0.25 wt% as impurities
Below, Cu 0.10 wt% or less and Zn 0.20 wt%
Casting a cast plate having a thickness of 4 to 6 mm by a direct casting rolling method from a molten aluminum-based alloy containing the following and the balance being Al and unavoidable impurities other than the above, without hot and cold rolling. It is easily achieved by an aluminum material for a disc wheel rim, characterized in that the cast plate is annealed at 200 to 450 ° C.

The aluminum material for disc wheel rims of the present invention will be described in more detail below. First, the reason for adding each alloy component of the molten aluminum alloy used in the present invention will be described. Mg has the most effective effect in increasing the mechanical strength of the obtained alloy plate. 2.0
If it is less than 3.5% by weight, the effect is small, and if it is more than 3.5% by weight, moldability and castability are deteriorated.

Mn has an effect of effectively increasing the mechanical strength, and also has an effect of making the recrystallized grain size fine to prevent roughening of the surface after molding and further improving surface gloss and corrosion resistance. If it is 0.08% by weight or less, these effects are small, and if it is 0.8% by weight or more, the formability is deteriorated and the effect of improving the corrosion resistance is saturated. Cr has an effect of effectively increasing mechanical strength, and also has an effect of making the recrystallized grain size fine to prevent rough skin after molding and further improving surface gloss, corrosion resistance, and weldability. If it is 0.08% by weight or less, these effects are small, and if it is 0.8% by weight or more, these effects are saturated or diminished. Further, when Mn and Cr are added at the same time, these effects are further increased as compared with the case where each is added alone.

Ti is effective in making the crystal grains of the alloy plate uniform and fine. If the amount is 0.002% by weight or less, the effect is small, and if the amount is 0.1% by weight or more, the effect is saturated. Although the above effect is obtained by adding only Ti, the grain refining effect is further improved by adding B together with Ti. Therefore, 2 to 20% by weight of B with respect to the Ti amount is allowed to coexist. Is preferred.

Further, Si may be mixed inevitably in the production of aluminum alloy, but it also has the effect of improving the mechanical strength. An amount of less than 0.1% by weight is sufficient, but an alloy containing 0.1% by weight or more is commercially advantageous from the viewpoint of production or availability. However, if the content is too large, the formability, toughness and corrosion resistance deteriorate, so the upper limit is made 0.20% by weight.

On the other hand, among the impurities contained in the alloy components, Fe deteriorates the formability, toughness and corrosion resistance of the alloy plate, and Cu and Zn impair the corrosion resistance of the alloy plate.
It is necessary to suppress Fe to 0.25% by weight or less, Cu to 0.10% by weight or less, and Zn to 0.20% by weight or less. Preferably, Fe and Zn are 0.15% by weight or less, respectively.

In the present invention, a cast plate having a thickness of 4 to 6 mm is obtained from the molten aluminum-based alloy having the above composition by the direct casting and rolling method without hot and cold rolling. The hot and cold rolling referred to here are those with a high rolling rate, that is, those that change the quality of the material by homogenizing the metal structure, imparting processing strain, etc. It means 20% or more when displayed.

In the present invention, the thickness of the cast plate needs to be 4 to 6 mm. The thickness of 4 to 6 mm is required for the final product of the disc wheel rim, and if it is too thin, sufficient strength cannot be expected, and if it is too thick, the weight increases and molding becomes difficult, which is not preferable. Thereafter, this cast plate does not undergo a normal hot or cold rolling process or the like.

In the present invention, the cast plate thus obtained is annealed. This improves the formability of the cast plate and controls the mechanical strength. Annealing temperature is 200
~ 450 ° C, preferably from 250 to 400 ° C,
It is selected according to the composition of the cast plate. When the temperature is 200 ° C or lower, the effect of improving the formability and controlling the mechanical strength is not recognized, and when the temperature is 450 ° C or higher, the recrystallized grains of the cast plate are coarsened, and the textured surface becomes rough during rim processing (so-called orange peel). ), Defects such as cracks occur and conversely the moldability deteriorates.

Further, in the present invention, in order to remove the plate strain of the cast plate and improve the plate thickness accuracy and formability, skin pass rolling with a rolling ratio of 5% or less can be performed. Unlike the so-called rolling, the skin pass rolling is a method of treating a surface of a cast plate with a rolling roll at a very low rolling rate, for example. The cast plate is then cut into a predetermined size and directly subjected to a rim forming process.

Regarding the relationship between the skin pass rolling and the annealing treatment, either one may be performed first. When the skin pass rolling is performed first, the sheet thickness precision is improved by the skin pass rolling, and the formability is improved by the annealing treatment. When the annealing treatment is performed first, the annealing treatment improves the formability, and the skin pass rolling improves the sheet thickness accuracy and adds compressive residual stress to the surface of the cast sheet, so that the formability is further improved. The cast plate subjected to the mechanical or thermal treatment is subsequently subjected to a rim forming process. The specific implementation method depends on the circumstances such as whether or not the casting machine is equipped with auxiliary equipment such as a pinch roll for skin pass rolling, and the like, for example, a combination of the following steps can be adopted.

Casting → Skin pass rolling → Annealing → Cutting → Rim processing Casting → Skin pass rolling → Cutting → Annealing → Rim processing Casting → Annealing → Skin pass rolling → Cutting → Rim processing

[0023]

EXAMPLES Next, the present invention will be explained more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist. Comparative Examples 1a to 5a Obtained by supplying molten aluminum-based alloy having the composition shown in Table 1 between a pair of cooled rotating casting rolls and continuously casting at a casting speed of 0.7 m / min. Plate thickness 5
The tensile test, the fatigue test, the impact test, the bending test, the microstructure observation, the spray test and the gloss measurement were performed on the direct casting rolled plate of mm. The results are shown in Tables 2 and 3. Tensile test according to the method based on JIS standard, tensile strength, 0.2%
The yield strength and elongation were measured. In the fatigue test, the maximum value of the stress amplitude which does not break even after the number of repetitions of 10 ⁶ times at 1800 cpm was obtained by the plane bending test. The impact test is performed according to JIS Z 2242 in accordance with the metal material impact test method (JIS Z 2242).
No. 3 test piece No. 02 (width 5 mm) was used. The bending test was performed on a No. 3 test piece of JIS Z 2204 based on the bending test method for metal materials (JIS Z 2248), and the surface condition after bending was evaluated by the presence or absence of cracks. If cracks occur, they will be cracked during rim processing, making molding impossible or defective. That is, this evaluation corresponds to evaluation of whether or not each aluminum-based alloy plate before rim processing can be formed as a rim material, that is, evaluation of basic characteristics as a rim. Microstructure observation is 4
It was carried out at a magnification of 00 times, and 10 planes of 1 mm ² were selected at 10 points in a cross section perpendicular to the casting and rolling directions, and the number of crystallized substances having a size of 10 μm or more present in each was measured. Spray test is JI
Referring to SH 8681, using a Cass tester (Suga Tester Co., Ltd. CASSER-ISO type), JIS
Salt water was sprayed for 30 minutes under the test conditions specified in H 8681. After the test was completed, the rating number was determined according to the rating number standard chart. The gloss is JIS
According to Z 8741, the value of the glossiness G _S (45 °) of the black glass mirror surface having a refractive index _{n = 1.520} is set to 88.8%, and based on this, a double-headed buffing machine (peripheral speed 200 m with a peripheral speed of 200 m) using Machires as an abrasive. / Min) of each alloy plate whose surface has been polished
The value of _S (45 °) was measured.

[0024]

[Table 1]

Comparative Examples 1 to 9 A molten aluminum base alloy having the composition shown in Table 1 was supplied between a pair of cooled rotating casting rolls and continuously cast at a casting speed of 0.7 m / min. Obtained plate thickness 5
mm direct casting and rolling plate and vertical type semi-continuous casting method to cast slabs, 5 mm thick, H obtained by hot rolling process
Various tests similar to Comparative Examples 1a to 5a were performed on the 112 temper DC plate. The results are shown in Tables 2 and 3.

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

Comparative Examples 6a to 8a Among the alloys having the compositions shown in Table 1, the direct casting rolled plates with alloy names B, C and G were subjected to skin pass rolling, and then cut to a predetermined size, and the plate thickness distribution was measured. did. Further, an adhesion bending test was carried out and the surface condition after the test was examined. The results are shown in Table 4. The plate thickness distribution is 1 mm by trimming 35 mm at both ends in the plate width direction from a directly cast rolled plate with a plate width of 1070 mm.
A 000 mm × 1000 mm plate was cut out, and a position of 25 mm from the periphery of this plate was selected at 4 positions on each side of the plate, for a total of 16 positions, and the results of measuring the plate thickness at that position are shown. In the close contact bending test, the aluminum-based alloy sheets of Comparative Examples 1a to 5a were subjected to the same test (based on JISZ 2248) after being subjected to skin pass rolling and cutting, and the surface state after bending was determined depending on whether or not rough skin was generated. evaluated. That is, this evaluation corresponds to the determination of the quality of the processed surface after the rim processing, that is, the evaluation of the characteristics for satisfying higher quality requirements for the rim. Comparative Examples 9a to 11a Among the alloys having the compositions shown in Table 1, the direct casting rolled plates with alloy names B, C and G were cut into predetermined dimensions, and then the same tests as in Comparative Examples 6a to 8a were performed. The results are shown in Table 4.

[0030]

[Table 5]

Examples 1 to 6 Among the alloys having the compositions shown in Table 1, the directly cast rolled plates of alloy names C and G were annealed at a temperature of 200 to 450 ° C. for 2 hours, and then subjected to a tensile test and a contact bending. The test was conducted. The results are shown in Table 5. Comparative Examples 10 to 13 Among the alloys having the compositions shown in Table 1, the directly cast rolled plates of alloy names C and G were annealed at a temperature of 200 ° C or lower and 450 ° C or higher for 2 hours, and then subjected to a tensile test and a contact bending. The test was conducted. The results are shown in Table 5.

[0032]

[Table 6]

Example 7 In Comparative Example 4a in which a direct cast rolled plate was produced using Alloy G, annealing treatment was then performed at 250 ° C. for 2 hours, and further 1.5% skin pass rolling was performed. Various physical properties of the obtained rolled plate were measured and the following results were obtained.

The tensile strength of 23.5kg / mm ² 0.2% proof stress 13.6 kg / mm ² elongation 30% fatigue test 13.0 kg / mm ² impact value 13.5kg · m / cm ² adhesion bending test ◎ plus surface Very good condition Thickness distribution 4.94 ± 0.02 mm In comparison with Comparative Example 4a, annealing treatment improves mechanical strength and significantly improves adhesion bending property, and skin pass rolling improves thickness accuracy. I know what I did.

[0035]

INDUSTRIAL APPLICABILITY In the cast plate of the present invention, alloy components are easily dissolved during casting, which effectively acts to improve mechanical strength, and the amount of partially crystallized intermetallic compounds is small and fine. Therefore, it is extremely excellent in fatigue strength, impact resistance, moldability, corrosion resistance, and surface glossiness, and is suitable as an aluminum material for a rim of a disc wheel that requires these characteristics. INDUSTRIAL APPLICABILITY The present invention can significantly shorten the rolling process as compared with a DC plate and can provide an excellent wheel rim material. In addition, since a cast plate having a plate thickness of 4 to 6 mm is directly obtained, the rolling process (hot rolling and cold rolling) can be completely omitted, which is extremely advantageous industrially and economically for disc wheel rims. Aluminum material can be manufactured.

Claims (2)

[Claims] 1. Mg of 2.0 to 3.5% by weight and Mn of 0.
08-0.8 wt% and at least one of Cr0.08-0.8 wt% and Ti 0.002-0.1 wt%
And Si 0.10 to 0.20% by weight, Fe as an impurity 0.25% by weight or less, Cu 0.10% by weight or less and Zn 0.20% by weight or less, the balance being Al and unavoidable other than the above. A cast plate having a thickness of 4 to 6 mm was cast from a molten aluminum-based alloy containing various impurities by the direct casting and rolling method without hot and cold rolling.
An aluminum material for a disc wheel rim, characterized by being annealed at 00 to 450 ° C. 2. The aluminum material for a disc wheel rim according to claim 1, wherein the cast plate is skin-pass rolled at a rolling ratio of 5% or less.