KR20160024837A - Aluminum alloy extruded material having excellent machinability and method for manufacturing same - Google Patents

Abstract

An Al-Mg-Si based aluminum alloy extruded material having no surface and smooth surface is obtained without hindering the productivity.
An aluminum alloy billet comprising 2.0 to 6.0 mass% of Si, 0.3 to 1.2 mass% of Mg, and 0.01 to 0.2 mass% of Ti, the Fe content being regulated to not more than 0.2 mass%, and the remaining Al and inevitable impurities, The homogenization treatment is carried out at 500 to 550 占 폚 for 4 to 15 hours, and the mixture is forcedly cooled to a temperature of 250 占 폚 or less at an average cooling rate of 50 占 폚 / hour or longer, heated at 450 to 500 占 폚, And the extruded material is forcibly cooled at an average cooling rate of 50 DEG C / sec or more to perform aging treatment. An extruded material having a surface 10-point average roughness Rz of 80 m or less can be produced.

Description

FIELD OF THE INVENTION [0001] The present invention relates to an aluminum alloy extruded material having excellent machinability,

The present invention relates to an Al-Mg-Si-based aluminum alloy extruded material having high strength and excellent machinability suitable for machine parts and the like which are used in many machining processes in the course of manufacture, and a method of manufacturing the same.

Patent Documents 1 to 4 disclose an Al-Mg-Si-based aluminum alloy extrusion material for cutting. In order to improve machinability, these extruded aluminum alloys for cutting use Si in an amount of 1.5% by mass or more and distribute Si-phase crystallites (Si phase) as second phase hard particles in the matrix.

Japanese Patent Application Laid-Open No. 9-249931 Japanese Patent Laid-Open No. 10-8175 Japanese Patent Application Laid-Open No. 2002-47525 Japanese Patent Application Laid-Open No. 2003-147468

The Al-Mg-Si-based aluminum alloy for cutting is obtained by crystallizing Si and Mg ₂ Si during the solidification process, and forming a β-AlFeSi-based compound (β-AlFeSi ). Fig. 1 shows a micrograph of the billet before the homogenization treatment. The Si phase (gray) of the band is continuous in the form of a net, and the Mg ₂ Si phase (black) is distributed in the form of a dot in the inside thereof, and an acicular β-AlFeSi phase (white) is formed along the Si phase. When this Al-Mg-Si based aluminum alloy billet is extruded, there is a problem that the extrusion material is picked up and the smoothness of the surface of the extruded material is damaged.

The reason why the Al-Mg-Si aluminum alloy extruded material is burned is as follows.

The strip-shaped Si phase present in the billet before extrusion causes a process (eutectic) reaction with the Al phase and the Mg ₂ Si phase due to deformation of the material due to extrusion and machining heat generation due to friction between the material and the die bearing portion, Melting occurs. Due to the shearing force applied when the extruded material passes through the die bearing portion, the melting point becomes the starting point, and the material (the cell surrounded by the Si phase) of the surface of the extruded material falls off, and a small portion is generated.

Further, the needle-like β-AlFeSi phase present in the billet before extrusion causes a partial melting reaction with the Mg ₂ Si phase due to the processing heat generated by the extrusion, whereby local melting occurs. If the localized melt continues to be generated continuously, the material on the surface of the extruded material falls off due to the shearing force that the extruded material receives when it passes through the die bearing portion, resulting in a fired portion.

The inner circumferential surface of the die is mirror-finished, but when the surface is baked, the surface of the extruded material becomes rough and loses smoothness.

The firing portion based on the Si phase, the Al phase and the Mg ₂ Si phase is subjected to a homogenization treatment at 500 to 550 캜 for 4 hours or more before the extruded billet, can do.

On the other hand, the sintering process based on the entrapping reaction of the? -AlFeSi phase and the Mg ₂ Si phase is performed by homogenizing at a temperature of 500 ° C or higher for a long time (about 50 hours when the amount of Si and Fe is large) Or by lowering the extrusion speed to lower the heat generation amount of the work. However, the homogenization treatment for a long time deteriorates the productivity and is disadvantageous in terms of cost, and the lowering of the extrusion rate also hinders the productivity.

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems involved in the production of extrusion materials for Al-Mg-Si based aluminum alloys for cutting, and it is an object of the present invention to provide an Al- -Mg-Si based aluminum alloy extruded material.

The Al-Mg-Si based aluminum alloy extruded material according to the present invention contains 2.0 to 6.0% by mass of Si, 0.3 to 1.2% by mass of Mg and 0.01 to 0.2% by mass of Ti and has an Fe content of 0.2% regulation is, the balance Al, and is unavoidably made with the impurity, the diameter 5μm is more AlFeSi particles is 20 or less per area of 50 × 50μm, also the diameter is 2μm or more Mg ₂ Si particles below 20 per area of 50 × 50μm, 10 of the extruded material surface And a point average roughness Rz of 80 占 퐉 or less. The aluminum alloy extruded material may further contain at least one of Mn: 0.1 to 1.0 mass% and Cu: 0.1 to 0.4 mass%, if necessary. The aluminum alloy extruded material may further contain at least one of 0.03 to 0.1 mass% of Cr and 0.03 to 0.1 mass% of Zr, if necessary.

The method for producing an Al-Mg-Si based aluminum alloy extruded material according to the present invention is characterized in that an aluminum alloy billet having the above composition is homogenized at 500 to 550 캜 for 4 to 15 hours, And then hot extruded at an extrusion speed of 3 to 10 m / min by heating to 450 to 500 캜, forcibly cooling the extruded material at an average cooling rate of 50 캜 / second or more, Is performed. By this manufacturing method, the Al-Mg-Si based aluminum alloy extruded material according to the present invention can be obtained.

According to the present invention, in the production of the Al-Si-Mg based aluminum alloy extruded material having a relatively large Si content, it is possible to reduce the firing portion without involving the homogenization treatment for a long time and the lowering of the extrusion speed, It is possible to obtain an Al-Si-Mg based aluminum alloy extruded material having a smooth surface of 80 μm or less and excellent machinability.

The Al-Si-Mg-based aluminum alloy extruded material according to the present invention has high strength and excellent cutting performance and has a smooth surface because of its smooth surface. Therefore, it is possible to reduce the machining amount of the cutting, It can be used as a product surface (without cutting) as it is.

1 is a scanning electron microscope (SEM) micrograph of a billet before homogenization treatment.
Fig. 1 is a photograph of a scanning electron microscope after a homogenization treatment of a billet.
Fig. 1 is a scanning electron micrograph of the extruded material obtained from the billet of Fig.
Fig. 12 is a scanning electron micrograph after the homogenization treatment of the billet.
Fig. 12 is a scanning electron micrograph of the extruded material obtained from the billet.
Fig. 13 is a photograph of a scanning electron microscope after the homogenization treatment of the billet.
Fig. 13 is a scanning electron micrograph of the extruded material obtained from the billet of Fig.

Hereinafter, an Al-Si-Mg based aluminum alloy extruded material according to the present invention and a method for producing the same will be described in detail.

(Composition of aluminum alloy)

The aluminum alloy according to the present invention contains 2.0 to 6.0% by mass of Si, 0.3 to 1.2% by mass of Mg and 0.01 to 0.2% by mass of Ti, and is composed of Al and unavoidable impurities. The aluminum alloy further contains, if necessary, at least one of Mn: 0.1 to 1.0% by mass and Cu: 0.1 to 0.4% by mass, and further optionally contains 0.03 to 0.1% by mass of Cr and 0.03 to 0.10% 0.1% by mass or more. The composition of the aluminum alloy itself is known, but the present invention is characterized in that the content of Fe in the unavoidable impurities is regulated to 0.2 mass% or less. Each component of the aluminum alloy according to the present invention will be described below.

Si: 2.0 to 6.0 mass%

Si forms a Si-based crystallization product (Si phase), which is a second-phase hard particle, in aluminum, and improves the cutting performance of cutting chips to improve machinability. For this purpose, it is necessary to add Si in an amount of 2 mass% or more, which exceeds the high-molecular-weight content in aluminum. On the other hand, when Si is added in an amount exceeding 6 mass%, a coarse Si phase is formed, and the melting initiation point is lowered by the process reaction of Si phase, Al phase and Mg ₂ Si phase. It is necessary to suppress the amount of heat generated at the time of extrusion in order to prevent the occurrence of local melting and firing accompanied by the drop of the melting start point. Therefore, the Si content is 2.0 to 6.0% by mass. The lower limit of the Si content is preferably 3.5 mass% and the upper limit is preferably 4.5 mass%.

Mg: 0.3 to 1.2 mass%

Mg is precipitated as fine Mg ₂ Si by the age-precipitation treatment to improve the strength. For this purpose, Mg is preferably added in an amount of 0.3 mass% or more. On the other hand, Mg ₂ Si is also formed as a crystallization product at the time of solidification, and undergoes a crystal reaction with β-AlFeSi at the time of extrusion to generate local melting, which causes baking. When the Mg content exceeds 1.2% by mass, a large amount of Mg ₂ Si crystallized product is formed, and the calcination is likely to occur. Therefore, the Mg content is set to 0.3 to 1.2% by mass. The lower limit of the Mg content is preferably 0.5% by mass, and the upper limit is preferably 0.9% by mass.

Ti: 0.01 to 0.2 mass%

Ti is added in order to stabilize the mechanical properties of the cast structure, but if it is less than 0.01 mass%, its effect can not be obtained. On the other hand, the addition of more than 0.2 mass% Therefore, the Ti content is set to 0.01 to 0.2 mass%. The lower limit of the Ti content is preferably 0.01 mass% and the upper limit is preferably 0.1 mass%.

Mn: 0.1 to 1.0 mass%

Cu: 0.1 to 0.4 mass%

Mn is precipitated as dispersed particles in the homogenization treatment, and the effect of improving the strength by fine-graining the crystal grains of the extruded material is added, if necessary. If the Mn content is less than 0.1 mass%, a sufficient effect can not be obtained. On the other hand, if the Mn content exceeds 1.0 mass%, the extrudability decreases. Therefore, the Mn content is set to 0.1 to 1.0 mass%. The lower limit of the Mn content is preferably 0.4 mass% and the upper limit is preferably 0.8 mass%.

Cu is added in place of or in combination with Mn to increase the strength of the extruded material as required. However, if the Cu content is less than 0.1 mass%, a sufficient effect can not be obtained. On the other hand, when the Cu content exceeds 0.4 mass%, corrosion resistance and extrudability are deteriorated. Therefore, the Cu content is set to 0.1 to 0.4 mass%. The lower limit of the Cu content is preferably 0.2 mass% and the upper limit is preferably 0.3 mass%.

Cr: 0.03 to 0.1 mass%

Zr: 0.03 to 0.1 mass%

Cr is added as necessary in order to suppress the recrystallization and to refine the crystal grains and to increase the strength of the extruded material. However, when the Cr content is less than 0.03 mass%, a sufficient effect can not be obtained. On the other hand, when the Cr content is more than 0.1 mass%, the sintering is likely to occur at the time of extrusion. Therefore, the Cr content is 0.03 to 0.1 mass%.

Zr is added in place of or in addition to Cr, if necessary, to refine the crystal grains by refining the crystal grains and to increase the strength of the extruded material. However, when the Zr content is less than 0.03 mass%, a sufficient effect can not be obtained. On the other hand, when the Zr content is more than 0.1 mass%, the compound with Al coarsens in the homogenization treatment and the effect of suppressing recrystallization is not obtained . Therefore, the Zr content is 0.03 to 0.1% by mass.

Fe: not more than 0.2% by mass

Fe existing as an unavoidable impurity in the aluminum alloy produces β-AlFeSi phase which is a needle-shaped crystallization product in the cooling process after casting. In order to reduce the amount of β-AlFeSi in the billet and to prevent burning at the time of extrusion, it is necessary to homogenize the β-AlFeSi phase to α form (spheroidize) or to reduce the Fe content of the aluminum alloy.

However, in order to change the? -AlFeSi phase to?, The homogenization treatment at a high temperature and for a long time is required and the productivity is impaired. On the other hand, when the Fe content of the aluminum alloy is regulated to 0.2 mass% or less, the amount of the produced β-AlFeSi phase is reduced, and the baking at the time of extrusion . On the other hand, the amount of Fe usually contained as an unavoidable impurity in the aluminum alloy is about 0.3% by mass.

(Manufacturing method of aluminum alloy extruded material)

Homogenization treatment conditions

The homogenization treatment of the cast billet is carried out at a holding condition of 500 to 550 DEG C for 4 to 15 hours. The reason why the holding temperature is set to 500 ° C or more and the holding time is set to 4 hours or more is to separate the Si phase crystallized in the strip and to solidify the crystallized Mg ₂ Si. As the holding temperature is high and the holding time is longer, the Si phase division and the solidification of Mg ₂ Si are promoted, which is preferable for reducing the bake. However, at a temperature exceeding 550 캜, local dissolution may occur. In time, productivity drops. Therefore, the homogenization treatment is carried out under the maintenance conditions within the range of 500 to 550 占 폚 for 4 to 15 hours. On the other hand, under this holding condition, the? -Derification of? -AlFeSi phase is not sufficiently achieved.

Cooling conditions after homogenization treatment

After the homogenization treatment, the billet is forcedly cooled at an average cooling rate of 50 DEG C / hour or more. Conventionally, after the homogenization treatment, the billet is taken out of the furnace and cooled by air cooling or air cooling. Since the high-temperature billets are cooled in a large accumulation state in the practical operation, even when the air is air-cooled, the cooling rate is generally estimated to be less than 30 DEG C / hour, but no attention has been paid to the cooling rate after homogenization . It is possible to suppress the precipitation of Mg ₂ Si to a minimum (to such an extent as to prevent occurrence of firing at the time of extrusion) by performing forced cooling until the temperature becomes 250 캜 or lower at an average cooling rate of 50 캜 / hour or more have. When the temperature is 250 DEG C or less, it may be cooled to room temperature. The preferable average cooling rate is 80 DEG C / hour or more, and can be achieved by forcibly performing fan air cooling without accumulating billets. More preferably water-cooling, in which case a cooling rate of about 100000 ° C / hour is achieved.

Extrusion conditions

After the homogenization treatment, the billet is reheated to 450 to 500 DEG C and hot extrusion is carried out at an extrusion speed of 3 to 10 m / min. Since the extruded material according to the present invention is a solid material (solid material), the extrusion ratio is relatively small and the heat generated by the process is not so large. Therefore, if the extrusion temperature is less than 450 캜, ℃. On the other hand, when the extrusion temperature exceeds 500 캜, the material heat is increased due to the application of heat from processing, and there is a risk that the extrusion material is burned. Therefore, the extrusion temperature (heating temperature of the billet) is set to 450 to 500 캜. If the extrusion speed is less than 3 m / min, the productivity is low. On the other hand, if it exceeds 10 m / min, the processing heat is increased and the material temperature rises, and there is a risk that the extruded material is burned. In addition, when the extruded material has angular portions on its cross section, a phenomenon called "cracks" in which the metal does not spread widely is apt to occur. Therefore, the extrusion speed is 3 to 10 m / min. In the production method of the present invention, the extrusion ratio (the cross-sectional area of the extrusion container / the cross-sectional area of the extrusion outlet) is preferably 15 to 40. [

Cooling conditions after extrusion

The extruded material immediately after extrusion is subjected to on-line forced cooling (die-casting) from the extrusion outlet temperature to a temperature of 250 DEG C or lower at an average cooling rate of 50 DEG C / sec or more. When the temperature is 250 DEG C or less, it may be cooled to room temperature. By an average cooling rate of more than 50 ℃ / sec, to prevent the precipitation of Mg ₂ Si. A preferred cooling means is water cooling.

Aging treatment conditions

The die extruded material is aged. The aging treatment may be carried out at a temperature in the range of 160 to 200 DEG C for 2 to 10 hours.

(The number of AlFeSi particles and the Mg ₂ Si particles in the extruded material (數) density)

The distribution of coarse? -AlFeSi grains and Mg ₂ Si grains in the Al-Mg-Si-based aluminum alloy extruded material according to the present invention is determined by the difference between the? -AlFeSi phase in the billet after homogenization treatment (after cooling) ₂ Si phase distribution. This point will be described with reference to the electron microscopic tissue photographs of Figs. 2A to 4B.

Figs. 2A, 3A and 4A are diagrams for explaining the operation of the embodiment No. 2. 1 is an electron micrograph showing the distribution of the β-AlFeSi phase and the Mg ₂ Si phase in the billets of 1, 12, and 13, respectively. The β-AlFeSi phase is a white needle-shaped particle, and the Mg ₂ Si phase is shown as a black granular particle. Figure 2b, Figure 3b and Figure 4b is an electron microscope photograph showing the tissue distribution of AlFeSi particles and the Mg ₂ Si particles in the extruded material obtained from their billet. The original? -AlFeSi phase is divided at the time of extrusion to form aggregates of white granular particles.

2B, the number of AlFeSi particles having a diameter of 5 mu m or more and the number of Mg ₂ Si particles having a diameter of 2 mu m or more per a predetermined area (50 mu m x 50 mu m) are all within the range specified in the present invention. 2B, the number of AlFeSi grains having a diameter of 5 mu m or more is relatively large and exceeds the stipulated range of the present invention. On the other hand, in Fig. 4B, Mg ₂ Si grains having a diameter of 2 mu m or more The number is relatively large and exceeds the range defined by the present invention. On the other hand, when the distribution states of the β-AlFeSi phase and the Mg ₂ Si phase are compared in FIGS. 2A, 3A and 4A, the β-AlFeSi phase is small and the Mg ₂ Si phase is small in FIG. The AlFeSi phase is comparatively large, and the size of the Mg ₂ Si phase is relatively large in Fig. 4A.

As described above, when the number of coarse AlFeSi grains having a diameter of 5 탆 or more in the extruded material is large, the amount of β-AlFeSi phase of the billet before extrusion (after the homogenization treatment) is large. The method of extrusion diameter, the number of coarse Mg ₂ Si particles over 2μm much larger the billet size of Mg ₂ Si particles of the extrusion before (after homogenizing treatment). This correspondence relationship can be established except when the extrusion ratio is extremely large (for example, 45 or more). Accordingly, by defining the distribution state of the? -AlFeSi particles having a diameter of 5 占 퐉 or more and the Mg ₂ Si particles having a diameter of 2 占 퐉 or more in the extruded material, the distribution of? -AlFeSi phase and Mg ₂ Si phase in the billet before extrusion (after homogenization treatment) It indirectly prescribes the state.

When the number of AlFeSi particles having a diameter of 5 占 퐉 or more and the number of Mg ₂ Si particles having a diameter of 2 占 퐉 or more in the extruded material is within the range defined in the present invention, the amount of? -AlFeSi phase in the billet is small and the precipitation of Mg ₂ Si particles is suppressed And the size of the Mg ₂ Si phase is small. On the contrary, when the number of AlFeSi particles having a diameter of 5 占 퐉 or more in the extruded material exceeds a specified range of the present invention, the amount of β-AlFeSi phase in the billet is large. When the number of the Mg ₂ Si grains having a diameter of 2 μm or more in the extruded material exceeds the specified range of the present invention, precipitation of the Mg ₂ Si phase in the billet is not sufficiently inhibited and the size of the Mg ₂ Si phase is large.

The number density of AlFeSi particles and Mg ₂ Si particles in the present invention is measured in the following order.

1) A cross section for measuring the number density of the extruded material was polished and then observed by a scanning electron microscope (SEM) to observe a square of 50 占 퐉 50 占 퐉 (parallel to the pair of sides of the extrusion direction) Select more than one.

2) The number of AlFeSi particles having a diameter of 5 占 퐉 or more and the number of Mg ₂ Si particles having a diameter of 2 占 퐉 or more contained in the observation region are measured (diameter is circle equivalent diameter). On the other hand, when measuring the number of particles contained in the area, it is preferable that the magnification of the SEM is set to 1000 times or more for precise measurement. The number of particles existing across the variation of the observation area is counted as one.

3) The number of each particle is measured for all observation regions selected in the order of 2), and an average value of the number of each particle included in all selected observation regions is obtained.

(Surface roughness of extruded material)

By homogenizing the billet of the Al-Mg-Si based aluminum alloy of the above composition under the above conditions, the band-shaped Si phase formed in the billet is spheroidized and Mg ₂ Si is solidified. Subsequently, precipitation of Mg ₂ Si particles during the cooling process is suppressed by forcibly cooling the billets held at the homogenizing treatment temperature to 250 ° C or lower at a cooling rate of 50 ° C / hour or more larger than usual. Since this billet has a small amount of β-AlFeSi phase and suppresses precipitation of Mg ₂ Si phase, the saturation reaction of β-AlFeSi phase and Mg ₂ Si phase is inhibited during extrusion and deposition of Mg ₂ Si phase is suppressed The process reaction of Si, Al and Mg ₂ Si is also suppressed. As a result, it is possible to manufacture an Al-Mg-Si aluminum alloy extruded material (extruded state material) having a reduced surface area of the extruded material and having a small surface roughness. According to the present invention, the surface roughness of the Al-Mg-Si based aluminum alloy extruded material can be made 80 탆 or less in terms of 10-point average roughness Rz (JIS B 0601: 1994).

Example

Al-Si-Mg-based aluminum alloy having the chemical composition (composition after dissolution) shown in Table 1 was dissolved and a billet having a diameter of 400 mm was formed by semi-continuous casting, and the homogenization treatment conditions (holding temperature, , Cooling rate). On the other hand, the remainder of the composition shown in Table 1 is inevitable impurities other than Al and Fe. Subsequently, extrusion molding was carried out at the extrusion conditions (extrusion temperature (billet heating temperature), extrusion speed and cooling speed) and extrusion ratio 33 shown in Table 1 to obtain an extruded material having a solid rectangular cross section (100 mm x 40 mm) Followed by aging treatment for 4 hours. On the other hand, the cooling rate is all the cooling rate up to 250 캜.

The number density of the coarse AlFeSi grains and the Mg ₂ Si grains and cutting performance, hardness, surface roughness (10-point average roughness Rz), and extrudability were measured by using the obtained extruded material as a specimen.

(A number density of particles and AlFeSi Mg ₂ Si particles)

After polishing the cross section for measurement of the number density of each of the specimens, each of the specimens was subjected to SEM observation (Scanning Electron Microscope, Scanning Electron Microscope) using a square of 50 m x 50 m ) Were selected from the two observation regions. For each of the specimens, the selected two observation regions were observed by SEM at a magnification of 1000, and AlFeSi particles having a diameter (circle equivalent diameter) of 5 탆 or more and Mg ₂ Si particles having a diameter (circle equivalent diameter) Were measured and the average value of the number of each of the particles measured in the two observation regions was obtained. The results are shown in Table 2. On the other hand, the number of particles existing across the variation of the observation region was counted as one.

(Machinability)

The drills were drilled at a speed of 1500 rpm and at a transfer speed of 300 mm / min using a commercially available high-speed 4 mm diameter drill, and the number of cuts in 100 g of the obtained cut powder was counted to determine the cutting property Respectively. It is preferable that the number of cuts is more than 7000 (⊚), that the number of cuts is 7000 to 5000 (∘), that the number of cuts is less than 5,000 to 3,000 (△) ×). The results are shown in the column of characteristics in Table 2.

(Hardness)

Rockwell hardness test of JIS Z 2245: 2011 - The Rockwell hardness (HRB) was measured based on the test method.

(Surface roughness)

(Total four surfaces) of the extruded material were visually observed over the entire length of the extruded material and the surface roughness (10-point average roughness Rz) of the portions determined to have the greatest surface roughness with respect to each surface was measured in the extrusion direction In accordance with the provisions of JIS B 0601: 1994. The maximum value of the ten-point average roughness Rz obtained on each surface is shown in the characteristic column of Table 2 as the surface roughness (ten-point average roughness Rz) of the extruded material.

(Extrudability)

No. Each part of the extruded material of 1 to 22 was visually observed over the entire length of the extruded material to observe whether or not each crack occurred (good and poor extrudability). Furthermore, the billets corresponding to the extruded material of the test number in which the occurrence of each crack was confirmed were extruded at an extrusion rate lower than the extrusion rate shown in Table 1, and the occurrence of each crack was observed. The billets corresponding to the test number of the extruded material for which the occurrence of each crack was not confirmed were extruded at an extrusion rate larger than the extrusion rate shown in Table 1 and the occurrence of each crack was observed. At this time, the extrusion speed was 3 m / min, 5 m / min, 10 m / min, and the homogenization treatment conditions and the extrusion conditions (except for the extrusion speed) were as shown in Table 1. When the extrusion rate was 10 m / min and the occurrence of each crack was not confirmed, the extrusion property was evaluated as excellent (O), and the occurrence of each crack was confirmed at an extrusion rate of 10 m / min. In the case where it was not confirmed, the extrudability was evaluated as good (DELTA), and when the occurrence of each crack was confirmed even if the extrusion speed was 3 m / min, the extrudability was evaluated as defective (X). The results are shown in Table 2.

As shown in Tables 1 and 2, the number density of AlFeSi grains and Mg ₂ Si grains having the composition defined in the present invention is the number density satisfying the requirements of the present invention. The extruded materials 1 to 9 have a small surface roughness (10-point average roughness Rz ≤ 80 mu m) and excellent machinability. In addition, the Rockwell hardness is 38 HRB or more, which is also excellent in strength. No. The extruded materials 1 to 9 are all manufactured by the manufacturing method defined in the present invention. On the other hand, Fig. 2A and Fig. 2B show electron micrographs of the billet (after homogenization treatment) and the extruded material. Fig.

On the other hand, Since the extruded material of No. 10 has an excessive Si content, it is burnt and the surface roughness is large.

No. The extruded material of 11 is inferior in cutting ability because the Si content is too small.

No. Since the Fe content of the impurity is excessive, the number density of AlFeSi particles exceeds the specification of the present invention and the surface roughness is large (10-point average roughness Rz > 80 μm). No. Figs. 3A and 3B show electron micrographs of the billets of 12 (after the homogenization treatment) and the extruded material. Fig. As shown in FIG. 3A, the β-AlFeSi phase in the billet was large, so that a portion was formed during extrusion to increase the surface roughness.

No. 13, the number density of Mg ₂ Si particles exceeds the specification of the present invention, and the surface roughness is large (10-point average roughness Rz> 80 μm). No. Figs. 4A and 4B show electron micrographs of the billet 13 (after the homogenization treatment) and the extruded material. Fig. Since the cooling rate after the homogenization treatment was small, the size of the Mg ₂ Si phase in the billet was large as shown in Fig. 4A, so that a small portion was generated at the time of extrusion and the surface roughness was increased.

No. Of the extruded material 14 is greater than the provisions of the invention, the number density of the particles and AlFeSi Mg ₂ Si particles present SiMg _2, and No. The extruded material of No. 15 has a higher number density of AlFeSi particles than those of the present invention, and has a large surface roughness (10-point average roughness Rz > 80 μm). This is because no. 14, the time for the homogenization treatment was short, 15, the temperature of the homogenization treatment was low, so that the α-modification of the β-AlFeSi particles did not proceed, and the division of the Si phase in the billets and the solidification of the Mg ₂ Si phase were insufficient.

No. 16, and 17 have an excessive Fe content, and the number density of AlFeSi particles exceeds the specification of the present invention, but the surface roughness is small (10-point average roughness Rz 80 μm).

This is because no. 16, the extrusion speed was significantly lowered than the lower limit of 3 m / min. 17, the time for the homogenization treatment was considerably longer than the upper limit of 15 hours, which is the prescribed value. As a result, 16, and 17, the productivity is lowered.

No. 18, and 19, the water densities of the AlFeSi particles and the Mg ₂ Si particles both satisfy the requirements of the present invention, but the surface roughness is large (10-point average roughness Rz> 80 μm). This is because no. 18, the extrusion temperature is too high; 19 shows that the extrusion speed is too high, the material temperature rises due to processing heat generation, and the extrusion material is burnt.

No. The extruded material of No. 20 had an excessive Cu content, so that the extrudability deteriorated.

No. Since the extruded material of No. 21 has an insufficient Mg content, its strength (hardness) is low.

No. Since the extruded material of No. 22 has an excessive Mg content, the number density of Mg ₂ Si particles exceeds the specification of the present invention and the surface roughness is large (10-point average roughness Rz> 80 μm). This is presumably because the Mg content was excessive, so that a large amount of Mg ₂ Si phase was formed in the billet, and a sintering occurred at the time of extrusion.

The present application is accompanied by a priority claim based on Japanese Patent Application No. 2014-156634 filed on July 31, 2014 as a basic application. Mention is made herein to MICRO-2014-156634.

Claims (8)

As an Al-Si-Mg based aluminum alloy extruded material having excellent machinability,
2.0 to 6.0% by mass of Si,
Mg: 0.3 to 1.2 mass%
Ti: 0.01 to 0.2 mass%
≪ / RTI >
The Fe content is regulated to 0.2 mass% or less,
The remaining Al and inevitable impurities,
The number of AlFeSi particles having a diameter of 5 占 퐉 or more is 20 or less per 50 占 50 占 퐉,
20 or less Mg ₂ Si particles having a diameter of 2 탆 or more per 50 × 50 μm area,
An aluminum alloy extruded material having an average surface roughness Rz of 80 탆 or less on the surface of the extruded material. The method according to claim 1,
Further comprising an Al-Si-Mg based aluminum alloy extruded material containing 0.1 to 1.0 mass% of Mn and 0.1 to 0.4 mass% of Cu. The method according to claim 1,
Further comprising at least one of 0.03 to 0.1% by mass of Cr and 0.03 to 0.1% by mass of Zr in an Al-Si-Mg based aluminum alloy extrusion material. 3. The method of claim 2,
Further comprising at least one of 0.03 to 0.1% by mass of Cr and 0.03 to 0.1% by mass of Zr in an Al-Si-Mg based aluminum alloy extrusion material. A method of producing an Al-Si-Mg based aluminum alloy extruded material excellent in cutting property,
2.0 to 6.0% by mass of Si,
Mg: 0.3 to 1.2 mass%
Ti: 0.01 to 0.2 mass%
≪ / RTI >
The Fe content is regulated to 0.2 mass% or less,
An aluminum alloy billet made of Al and inevitable impurities,
The homogenization treatment is carried out at 500 to 550 占 폚 for 4 to 15 hours, and the mixture is forcedly cooled to a temperature of 250 占 폚 or less at an average cooling rate of 50 占 폚 / hour or longer, heated at 450 to 500 占 폚, And subjecting the extruded material to forced cooling at an average cooling rate of 50 占 폚 / second or more to perform an aging treatment. 6. The method of claim 5,
Wherein said aluminum alloy further contains at least one of Mn: 0.1 to 1.0 mass% and Cu: 0.1 to 0.4 mass%. 2. The Al-Si-Mg based aluminum alloy extruded material according to claim 1, 6. The method of claim 5,
Wherein the aluminum alloy further contains at least one of 0.03 to 0.1% by mass of Cr and 0.03 to 0.1% by mass of Zr, based on the total mass of the Al-Si-Mg-based aluminum alloy extruded material. The method according to claim 6,
Wherein the aluminum alloy further contains at least one of 0.03 to 0.1% by mass of Cr and 0.03 to 0.1% by mass of Zr, based on the total mass of the Al-Si-Mg-based aluminum alloy extruded material.

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