JPH09249952A - Production of aluminum forged product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a forged product having a structure after heat treatment in which recrystallized grains are finely controlled on the whole face and free from anisotropy in mechanical properties. SOLUTION: An extruded material of an aluminum alloy having a compsn. contg., by weight, 1.0 to 1.5% Si, 0.4 to 0.9% Cu, 0.8 to 1.5% Mg and 0.3 to 0.9% Cr, and in which the content of Fe is regulated to 0.05 to 0.2% and that of Zn to <=0.25% is cut, is heated at 450 to 500 C, is subjected to primary forging using a die held at 400 to 460 deg.C, is again heated at 500 to 540 deg.C, is subjected to secondary forging using a die held at 400 to 460 deg.C and is subjected to heat treatment in which it is subjected to solution treatment at 510 to 545 deg.C for 2 to 6hr, is water-cooled and is subsequently subjected to aging treatment at 160 to 190 deg.C for 4 to 12hr. The aluminum alloy to be used may contain 0.03 to 0.05% Ti, 0.0001 to 0.01% B, 0.2 to 0.6% Mn and 0.1 to 0.2% Zr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a forged aluminum product such as a vehicle part having excellent mechanical strength.

[0002]

2. Description of the Related Art Iron-based materials have been widely used as parts used for vehicles and the like. However, as the weight is reduced, the fuel consumption is improved, and the performance is improved, the number of cases where aluminum alloy forged products are used is increasing. Since the aluminum alloy used is required to have excellent corrosion resistance and strength, it is generally manufactured by hot forging an Al—Mg—Si alloy.

[0003]

However, conventional Al
In the —Mg—Si alloy, the work structure becomes coarse recrystallized grains by hot forging or the subsequent heat treatment, or the recrystallized grains rapidly grow to generate a secondary recrystallized structure, and as a result, sufficient recrystallized structure occurs. No strength can be obtained. The present invention has been devised to solve such a problem, and by combining the composition of the aluminum alloy to be used, extrusion, forging and heat treatment under specified conditions, it becomes possible to obtain fine recrystallized grains on the entire surface. It is an object of the present invention to provide a forged product having a controlled heat-treated structure and having no anisotropy in mechanical properties.

[0004]

According to the manufacturing method of the present invention,
Si: 1.0-1.5 wt%, Cu: 0.4-0.9 wt%, Mg: 0.8-1.5 wt% and Cr: 0.3-
Including 0.9% by weight, Fe: 0.05 to 0.2% by weight,
Zn: After the aluminum ingot regulated to 0.25% by weight or less is homogenized, the material temperature immediately after extrusion is 450 to
It is extruded to 500 ° C. and cut into a predetermined length.
When performing hot forging in one step, forging is performed so that the material temperature immediately after forging is 450 to 500 ° C, and then 510 to 510
Heat-treated at 545 ° C for 2 to 6 hours, cooled with water, and then cooled to 16
Heat treatment is performed at 0 to 190 ° C. for 4 to 12 hours.

When the shape is complicated and the production involves many steps, the aluminum ingot having the above-mentioned composition is homogenized, then extruded so that the material temperature immediately after extrusion is 450 to 500 ° C., and cut. The extruded material at 450 to 500 ° C.
To the material temperature immediately after the primary forging using a die held at 400 to 460 ° C so that the material temperature immediately after the primary forging is 450 to 500 ° C, and the primary forged product is again heated to 500 to 540 ° C, Secondary forging into a product with a complicated shape using a die held at 400 to 460 ° C so that the material temperature immediately after the next forging is 450 to 500 ° C, 510 to 545 ° C x 2
After heating for 6 hours and cooling with water, a heat treatment of heating at 160 to 190 ° C. for 4 to 12 hours is performed, and a predetermined forged product shape is machined. That is, it is important to maintain the material temperature during the forging process within the temperature range of 450 to 500 ° C. regardless of the number of times the forging is performed. The aluminum alloy used is T
i: 0.03 to 0.05% by weight, B: 0.0001 to
0.01 wt% and Mn: 0.2 to 0.6 wt% may be included. Further, an aluminum alloy containing Zr: 0.1 to 0.2 wt% can also be used.

The alloying elements contained in the aluminum alloy used in the present invention and their contents are as follows. Si: 1.0 to 1.5% by weight It is an element that improves the strength of the aluminum alloy by the precipitation effect. Since it is added together with Mg, the Mg ₂ Si-based compound is precipitated by the aging treatment during the T6 treatment, and the strength improving action is obtained. The action of such Si addition is S
It becomes remarkable when the i content is 1.0% by weight or more. But,
When a large amount of Si is contained in excess of 1.5% by weight, grain boundary embrittlement due to grain boundary precipitation of Si is likely to occur, resulting in deterioration of extrusion and forgeability. Cu: 0.4 to 0.9% by weight Solid solution strengthening of the matrix, and CuAl ₂ and Al-Cu-Mg based intermetallic compound are also precipitated by the aging treatment at the time of T6 treatment, and strength improving action by Mg ₂ Si precipitation It is an alloying element effective in promoting the above-mentioned phenomenon, and a content of 0.4% by weight or more is required. However, when a large amount of Cu exceeding 0.9% by weight is contained, quenching sensitivity becomes high,
Corrosion resistance deteriorates.

Mg: 0.8-1.5 wt% By aging treatment during T6 treatment, it reacts with Si to form a Mg ₂ Si-based compound which precipitates in the matrix and improves the strength of the aluminum alloy. In order to obtain this precipitation effect, 0.
A Mg content of 8% by weight or more is required. However, 1.
When Mg is contained in an amount of more than 5% by weight, not only the precipitation hardening effect is saturated, but also the quenching sensitivity becomes high. Cr: 0.3 to 0.9% by weight It is an important alloying element for suppressing the coarsening of recrystallized grains in cooperation with Mn, and the content of 0.3% by weight or more is necessary. The effect of Cr suppressing the growth of recrystallized grains is particularly exerted in the secondary forging and the subsequent T6 treatment, and makes the structure after T6 treatment a fine structure on the whole surface. However, when Cr is contained in an amount exceeding 0.9% by weight, workability is reduced.

Fe: 0.05 to 0.2 wt% Fe becomes an Al-Fe-Si compound and is dispersed in the matrix. The coarse Al-Fe-Si compound is
It adversely affects elongation and corrosion resistance. Therefore, the upper limit of the Fe content is set to 0.2% by weight. But F
When the e content is less than 0.05% by weight, casting cracks are likely to occur. Further, the Fe content is 0.05 to
In the range of 0.2% by weight, coarsening of recrystallized grains is suppressed by the Al-Fe-Si compound during solution treatment of the forged product. Zn: 0.25 wt% or less Zn is an unavoidable impurity that is mixed in from aluminum scrap or the like, and it is desirable that the amount is small. 0.25% by weight
Zn exceeding 5 is likely to cause stress corrosion cracking, so the upper limit of the Zn content is defined as 0.25% by weight.

Ti: 0.03 to 0.05% by weight It is an effective alloying element for refining the cast structure.
The effect of refining the cast structure becomes remarkable when the Ti content exceeds 0.03% by weight. In addition, the aluminum alloy whose structure is refined by the addition of Ti suppresses the occurrence of defects such as casting cracks in the billet. However, a large amount of T
Since the inclusion of i deteriorates the toughness of the aluminum alloy,
The upper limit was set to 0.05% by weight. B: 0.0001 to 0.01 wt% Like Ti, it is an alloying element effective for refining the cast structure, and its effect is observed at a content of 0.0001 wt% or more. The upper limit of the B content was set to 0.01% by weight for the same reason as the Ti content.

Mn: 0.2-0.6% by weight Like Cr, it is an alloying element effective in suppressing the growth of recrystallized grains and maintaining a fine structure after T6 treatment.
It is required to contain at least wt%. The effect of Mn suppressing the growth of recrystallized grains appears as a remarkable effect when coexisting with Cr, and suppresses the coarsening of recrystallized grains during the solution treatment in the secondary forging and T6 treatment. However, when a large amount of Mn exceeding 0.6% by weight is contained, the workability during forging becomes poor. Zr: 0.1 to 0.2% by weight It is an alloying element that is effective in suppressing coarsening of recrystallized grains in cooperation with Mn and Cr. Suppress coarsening. Such an effect of Zr addition becomes remarkable at a Zr content of 0.1% by weight or more.
However, if a large amount of Zr is contained, the workability is adversely affected. Therefore, when Zr is added, the upper limit is set to 0.2% by weight.

The aluminum alloy whose composition has been adjusted as described above is cast into a billet or the like ingot having a cylindrical cross section by a normal semi-continuous casting method, homogenized, and then extruded into a shape suitable for the final product. To be done. Next, the extruded material is cut into a predetermined length. Extrusion Extrusion has a great influence on the subsequent product properties, so it is necessary to finely control the extrusion conditions. First, the billet cast prior to extrusion is 520 to 560 ° C x 5 to 1
After performing a homogenization treatment for 0 hours, it is cut, charged again in the heating furnace, and heated to 490 to 510 ° C. It is important to control the heating conditions so that the material temperature immediately after extrusion is 450 to 500 ° C., and by adjusting the temperature of the extruded material to this range, after the forging by the transition elements such as Cr, Mn, and Zr. The coarsening of recrystallized grains is suppressed by the T6 treatment. Also, if the temperature of the extruded material is lower than 450 ° C,
The T6 treatment of the forged product facilitates coarsening of recrystallized grains. On the contrary, if the temperature of the extruded material exceeds 500 ° C., there is a drawback that tearing occurs in the extruded material.

Primary Forging Before being subjected to the primary forging step, the cut extruded material is put into a heating furnace and heated to 450 to 500 ° C. The heating temperature at this time is important for making the structure of the final product after T6 treatment fine. If the heating temperature is not in the range of 450 to 500 ° C., the recrystallized structure after T6 treatment becomes coarse, and uniform and fine recrystallized grains cannot be obtained. The heating and holding is performed for about 1 hour in order to make the temperature uniform. In primary forging,
The mold is heated to 400 to 460 ° C. This mold temperature is important for preventing the material during primary forging from being excessively cooled. The material for the primary forging is 400-
By maintaining the temperature at 460 ° C., the temperature range of 450 to 500 ° C. is maintained. The temperature range of 450 to 500 ° C. is important for suppressing the growth of recrystallized grains after T6 treatment. If the heating temperature at this time is lower than 450 ° C., the deformation resistance increases, making not only forging difficult but also the crystal grains tend to become coarse during the heat treatment described later. Conversely, 500
If the heating temperature is higher than 0 ° C, burning tends to occur in the material.

In the primary forging, the raw material heated to 450 to 500 ° C. is vertically crushed by a die forging method to manufacture a primary forged product. Alternatively, the primary forged product can be manufactured by free forging. At this time, the vertical deformation rate [(initial extruded material length or outer diameter-extruded material length or outer diameter after forging) x (initial extruded material length or outer diameter) ^-1 x 1
[00%] is preferably 50 to 70%. Primary forging is a process for forming a shape close to the next product shape, and if the deformation rate is small, secondary forging becomes difficult. However, if the deformation ratio is excessively large, not only forging cracks will occur, but also forming by secondary forging becomes difficult. In this respect, when the extruded material is forged at a deformation rate of 50 to 70%, the extruded fibrous structure is elongated in the deformation direction, and thus the material becomes effective as a high-strength final product.

Secondary Forging The material that has been forged for primary is 500 to 5 before the secondary forging.
Heat to 40 ° C. The heating temperature of 500 to 540 ° C. is a high set value as compared with the normal hot forging temperature, but it is suitable for producing a product having a complicated shape by forging. If the heating temperature at this time exceeds 540 ° C, the secondary forged product is likely to crack. On the contrary, at a heating temperature which does not reach 500 ° C., the recrystallized grains of the final product are coarsened during the solution treatment in the T6 treatment. In the secondary forging, the die temperature is maintained in the range of 400 to 460 ° C so that the temperature of the forged product during the forging is 450 to 500 ° C as in the case of the primary forging.
Higher mold temperature is desirable, but if it exceeds 460 ℃,
Not only the life of the mold is shortened, but also the adhesion of the lubricant is deteriorated, and as a result, defects such as forging cracks are likely to occur. On the contrary, at a mold temperature of less than 400 ° C, the T6 of the secondary forged product is
The recrystallized grains become coarse during the solution treatment in the treatment. The primary forged product is forged into a secondary forged product with a deformation rate of about 50 to 70%. Even when the die temperature is 400 to 460 ° C, the forged material is heated to 500 to 540 ° C, and deformation resistance heat is generated during forging, so that the forged product is kept at 450 to 500 ° C. It is important that this temperature condition is satisfied regardless of the number of forgings.

Heat treatment The secondary forged product is heated at 510 to 545 ° C. for 2 to 6 hours,
After cooling with water, an aging treatment (T6 treatment) of heating at 160 to 190 ° C. for 6 to 12 hours is performed. 510-545 ° C ×
The heating for 2 to 6 hours is a solution treatment for solid-dissolving Mg, Si, Cu and the like. The solid-solved Mg and Si precipitate as Mg ₂ Si in the subsequent aging step to secure the strength. Cu
Serves to strengthen the matrix by solid solution, partially precipitated during the aging treatment as CuAl _2, Al-Cu-Mg-based intermetallic compound further improves the strength. On the other hand,
Alloying components such as Cr, Mn, and Zr have already been precipitated as fine intermetallic compounds by the homogenization treatment, and they do not form a solid solution in the matrix even by the solution treatment, resulting in coarsening of recrystallized grains after forging. It is considered to have a preventive function. The effect of these precipitates is that the morphology of the precipitates differs depending on the forging temperature and the degree of processing, and it is speculated that certain specific morphologies and specific distributions of precipitates prevent coarsening of recrystallized grains. . And the material temperature during forging is 450 ~ 500
When the temperature is in the vicinity of ° C, the strain introduced during the hot working is released during the cooling, and the strain energy accumulated in the forged product before the solution treatment is reduced. Therefore, the energy available for crystal growth during solution treatment is small, and Mn, C
Coarsening of recrystallized grains is prevented by the r and Zr-based grains.
On the other hand, when forged at a temperature lower than 440 ° C., a large amount of strain introduced during forging remains even after the cooling is completed, and the residual strain becomes the growth energy of recrystallized grains during solution treatment, and M
Even if n, Cr, and Zr-based particles are present, coarsening of recrystallized grains cannot be prevented. On the contrary, forging at a temperature higher than 500 ° C. makes it impossible to produce a sound product due to the occurrence of burning. The solution treated product is water quenched and
An aging treatment is performed by heating at 0 to 190 ° C. for 4 to 12 hours. By this aging treatment, Mg ₂ Si, CuAl ₂ , Al
-Cu-Mg-based intermetallic compound and the like are deposited, and the strength of the matrix is secured. Machining The heat-treated product is machined to adjust the plate thickness of each part and to process screw holes.

[0016]

【Example】

Example: An aluminum alloy having the components and compositions shown in Table 1 was semi-continuously cast into a billet having a diameter of 240 mm. The billet was homogenized at 540 ° C. for 8 hours, cut into a predetermined length, heated to 500 ° C. and extruded to obtain a round bar having a diameter of 35 mm. The temperature immediately after extrusion of the extrusion rod was 490 ° C. This extruded rod has a diameter of 3
A test forging material having a length of 5 mm and a length of 90 mm was cut out.

[0017]

The forged material thus obtained was subjected to a soaking treatment at 480 ° C. for 1 hour, and then at a mold temperature of 430 ° C., the deformation rate of each part of the material was 50% in average deformation rate from the direction perpendicular to the longitudinal direction. It was forged and was first molded into a shape close to the secondary molded product of FIG. The material temperature immediately after forging at this time was 450 ° C. After heating this primary forged product at 400 ° C. and 520 ° C. for 1 hour, secondary forging was performed from a direction perpendicular to the length direction at a mold temperature of 430 ° C. and an average deformation rate of 70%, and the secondary forging shown in FIG. Forged into the shape of a forged product. The material temperature immediately after the secondary forging was 380 ° C. when heating at 400 ° C. and 490 ° C. when heating at 520 ° C. When the macrostructure of the vertical cross section of the secondary forging material was observed, all the forging materials had a uniform and fine structure as shown in FIGS. 2 and 3, regardless of the secondary forging temperature. After subjecting each secondary forged product to the water quenching treatment at 530 ° C. for 3 hours → water, the vertical cross-sectional macrostructure was observed. The macrostructure has a secondary forging temperature of 400 ° C.
At that time, as shown in FIG. 4, the recrystallized grains grew around the center in the vertical direction. On the other hand, when the secondary forging temperature was 520 ° C., the entire surface had a fine recrystallized structure as shown in FIG. 5, and the growth of recrystallized grains was not detected.

As is apparent from FIG. 4, when the secondary forging temperature is 400 ° C., the recrystallized grains in the central portion are coarse.
This is also due to the high deformation rate of the central portion, and when the deformation rate is high, the strain energy accumulated when the forging temperature is low is large and the recrystallized grains become coarse. On the other hand, in samples No. 2 and 3, coarsening of recrystallized grains is not progressing in the central portion as compared with sample No. 1. this is,
Compared to the sample No. 1 aiming at the effect of Cr, it is shown that the effect of compound addition of Cr + Mn in the sample No. 2 and Cr + Mn + Zr in the sample No. 3 is significantly exhibited.
The primary forging temperature is 400 ° C and the secondary forging temperature is 520.
In all cases, the recrystallization structure after the solution treatment was coarse at the center, when the temperature was ℃, and when the primary forging temperature was 400 ° C and the secondary forging temperature was 400 ° C. A material having such a structure is not preferable because it has anisotropic mechanical properties. Moreover, the recrystallized grains were not coarsened by the aging treatment.

Comparative Example: In the composition of sample No. 1 in Table 1, the billet was homogenized at 540 ° C. for 8 hours, cut into the same length, and heated to 470 ° C. and extruded.
A round bar having a diameter of 35 mm was obtained. The temperature of the extrusion rod immediately after extrusion was 440 ° C. After subjecting this forging material to heat treatment at 480 ° C for 1 hour, it is forged from a direction perpendicular to the length direction at a mold temperature of 430 ° C and a deformation ratio of each part of the material of 50%, and the secondary molding of Fig. 1 is performed. Molded into a shape close to the product. The temperature of the primary forged product immediately after forging was 453 ° C. After subjecting this primary forged product to a water quenching treatment at 530 ° C. for 3 hours and then observing the cross-sectional macrostructure in the vertical direction, it was found that the central portion was coarse-grained. From this, it is understood that when the material temperature immediately after extrusion deviates from 450 to 500 ° C., the recrystallized grains are coarsened during the solution treatment in the T6 treatment.

[0021]

As described above, in the present invention, by combining the components / compositions, extrusion and forging under specific conditions, coarsening of recrystallized grains is suppressed after T6 treatment, and the entire surface is uniform. It has a fine recrystallized structure. As a result, a highly reliable forged product having no anisotropy in mechanical properties and high reliability can be obtained.

[Brief description of drawings]

FIG. 1 is a secondary forged product for test manufactured in Example 1.

FIG. 2 is a photograph showing a macrostructure of a test forged product which has been subjected to secondary forging at a secondary forging temperature of 400 ° C.

FIG. 3 is a photograph showing a macrostructure of a test forged product that has undergone secondary forging at a secondary forging temperature of 520 ° C.

FIG. 4 is a photograph showing a macrostructure of a test secondary forged product obtained by subjecting a product secondary forged at a secondary forging temperature of 400 ° C. to a solution treatment.

FIG. 5 is a photograph showing a macrostructure of a test secondary forged product obtained by subjecting a product secondary forged at a secondary forging temperature of 520 ° C. to a solution treatment.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsu Yamada 1-34-1, Kambara, Kambara-cho, Anbara-gun, Shizuoka Prefecture Nippon Light Metal Co., Ltd. Group Technology Center (72) Yuuji Yuzuki, Kambara-cho, Anbara-gun, Shizuoka Prefecture 34-1-1 Nihon Light Metal Co., Ltd. Group Technology Center

Claims (4)

[Claims] 1. Si: 1.0 to 1.5% by weight, Cu:
0.4-0.9% by weight, Mg: 0.8-1.5% by weight and Cr: 0.3-0.9% by weight, Fe: 0.05
After homogenizing the aluminum ingot regulated to 0.2 wt% or less, Zn: 0.25 wt% or less, 490 to 510
Material temperature immediately after extrusion by heating to ℃ 450-500 ℃
And extruded so that the material temperature immediately after forging is 450 to 500 ° C., then subjected to solution treatment at 510 to 545 ° C. for 2 to 6 hours, and after water cooling , 160 to 190 ° C. × 4 to 12 hours, and a method for producing an aluminum forged product in which coarse growth of recrystallized grains during solution treatment is suppressed. 2. Si: 1.0 to 1.5% by weight, Cu:
0.4-0.9% by weight, Mg: 0.8-1.5% by weight and Cr: 0.3-0.9% by weight, Fe: 0.05
After homogenizing the aluminum ingot regulated to 0.2 wt% or less, Zn: 0.25 wt% or less, 490 to 510
Material temperature immediately after extrusion by heating to ℃ 450-500 ℃
And extruded so that the material temperature immediately after primary forging is 450 to 500 ° C., the extruded material is heated to 450 to 500 ° C., and 400 to 46
Primary forging is performed using a die held at 0 ° C, the primary forged product is again heated to 500 to 540 ° C, and 400 to 460 ° C so that the material temperature immediately after the secondary forging is 450 to 500 ° C.
Secondary forging is performed on a product having a complicated shape by using the mold held in, and solution treatment is performed at 510 to 545 ° C for 2 to 6 hours, and aging treatment at 160 to 190 ° C for 4 to 12 hours is performed after water cooling. A method for manufacturing an aluminum forged product that is heat-treated and machined into a predetermined forged product shape. 3. Further, Ti: 0.03 to 0.05% by weight,
B: 0.0001 to 0.01% by weight and Mn: 0.2 to
The method for manufacturing an aluminum forged product according to claim 1, wherein an aluminum alloy containing 0.6% by weight is used. 4. The method for producing an aluminum forged product according to claim 1, wherein an aluminum alloy further containing Zr: 0.1 to 0.2 wt% is used.