KR100732195B1 - Al-alloy for extrusion forming - Google Patents

Abstract

The present invention relates to a high-strength aluminum alloy for extrusion with excellent moldability of the 6xxx series.

In the aluminum alloy of the present invention, Si 0.95 to 1.05 wt%, Mg 0.5 to 0.6 wt%, Mn 0.5 to 0.6 wt%, Fe 0.15 to 0.25 wt%, Cr 0.13 to 0.18 wt%, Cu 0.05 wt% or less, Ti 0.03 up to wt%, up to 0.05 wt% of Zn and up to 0.02 wt% of each other unavoidable component, the sum of which is up to 0.10 wt% and the balance of Al.

The high-strength aluminum alloy for extrusion having excellent moldability of the present invention has the advantage of being able to improve productivity while improving the quality of a molded product having a complicated shape due to excellent moldability while improving extrudability and strength.

Aluminum alloy, formability, extrusion

Description

High-strength aluminum alloy with excellent moldability {Al-alloy for extrusion forming}

1 is a graph showing an energy dispersive spectroscopy of aluminum alloy.

  (A) is an analysis graph of one embodiment aluminum alloy of the present invention,

  (B) is an analysis graph of the conventional 6082 aluminum alloy.

Figure 2 shows a photograph of the structure after homogenizing the billet cast in a conventional 6082 aluminum alloy,

  (A) is the organizational picture of the core,

  (B) is the organization picture in the middle,

  (C) is a photograph of the organization of the surface.

Figure 3 is a view showing a structure photograph after homogenizing the billet cast in one embodiment of the present invention aluminum alloy,

  (A) is the organizational picture of the core,

  (B) is the organization picture in the middle,

  (C) is a photograph of the organization of the surface.

The present invention relates to a high-strength aluminum alloy for extrusion which can be used as a material for extrusion and forging. More specifically, the Mg content of Mg is increased so that Mg ₂ Si generated in the aluminum alloy structure is 1.0 wt% or less. Extrudeability with excellent moldability optimized for extruded products used in automobile parts, road and bridge materials, construction materials such as formwork and curtain walls by reducing weight control to improve extrudability and strength, and to have excellent formability. It relates to a high strength aluminum alloy.

Aluminum is the second most used metal after steel. It is lightweight, has good corrosion resistance and workability, has high electrical and thermal conductivity, and makes various kinds of high strength and high corrosion resistance alloys with elements such as Cu, Mg, Si, Zn, Mn, and Ni. It is used in all areas of home and industry such as aircraft, household goods, construction, vehicles, machinery, and electricity.

The aluminum is classified according to the type of alloy, bar 1000 is pure aluminum containing more than 99.00wt% aluminum, 2000 is Al-Cu alloy, 3000 is Al-Mn alloy, 4000 is Al It is widely used to classify and mark Si-alloy alloys, Al-Mg-based alloys for No. 5000, Al-Mg-Si-based alloys for No. 6000, and Al-Zn-based alloys for No. 7000.

The greatest advantage of the aluminum alloys classified as above is that the weight is about one third of that of steel, but it does not lag behind or have better mechanical properties than steel depending on the addition of various alloying elements. For example, the proportion applied to auto parts is increasing.

Automobiles have evolved as a means of transportation, the most basic element of modern civilization, and modern civilization without automobiles cannot exist, but the emissions of automobiles have a great influence on global warming and are the main culprit of air pollution. Among them, various regulations are being implemented or in preparation for reducing automobile emissions.

Accordingly, car makers are developing automobiles using electricity, fuel cells, hydrogen, etc. as energy sources, or hybrid vehicles using fossil fuels and electricity in parallel, and some of them are currently on the market.

However, as described above, many vehicles are still required to have no pollution emission or very few automobiles, and as an intermediate step, various automobile parts may be used to reduce emissions through improved fuel efficiency due to lighter weight of automobiles. It is replacing steel with aluminum.

In addition, in today's automobiles, the design and development of components are performed at the same time, and in order to reduce assembly time and reduce costs, a plurality of unit parts are assembled into one assembly, that is, a module unit, and then each assembly is assembled. Since the final combination is a modular method, among the modules constituting the vehicle, the aluminum of the chassis module, which is very important for the ride comfort and safety of the vehicle and has a heavy weight, is essential for the weight reduction of the vehicle.

Part of the components constituting the chassis module, in particular, aluminum parts are the control arm and the sub-frame, the control arm is located inside the tire to serve to transfer the load input from the road surface to the vehicle body It is a part that connects and supports wheels, brakes, etc. to the vehicle body, and the subframe is composed of cross members, side members, brackets, etc. to reinforce structural strength and to connect engines and various control arms. It will have a decisive impact on improvement.

In particular, subframes, which have a greater contribution to the weight reduction of automobiles, should be replaced with aluminum, but in Korea, subframes are still manufactured by press stamping steel sheets. However, there are only cases where prototypes were manufactured by gravity casting.

However, in the case of large overseas auto parts makers, the development of parts using aluminum materials in the hydroforming and press stamping processes has been completed, and research is being conducted to manufacture them more effectively.

As described above, an aluminum material of 6xxx series Al-Mg-Si is used as an aluminum material used for aluminumization of a subframe, which is essential for weight reduction of an automobile as described above.

Al-Mg-Si-based alloys are typical precipitation hardening alloys, and their high deformation ability is suitable for extrusion processing, and has superior extrudability compared to 5XXX series or 7XXX series aluminum alloys.

In addition, the 6xxx-based Al-Mg-Si-based alloys not only have age hardening properties, but also have good toughness and are suitable for deep processing, and are particularly widely used as extrusion materials. As the quality increases and the product structure becomes complicated, among the conventional Al-Mg-Si-based aluminum alloys, especially 6082 aluminum alloy is widely used as a material for automobile parts, it is required to provide the formability and strength suitable for the parts properties requiring high quality. It could not be satisfied.

In addition, not only the extrudeability of high-quality products such as automotive parts is deteriorated, but also the occurrence of cracks due to the lack of physical properties when processing the final product after cutting the extruded material has a problem that the cost of manufacturing parts.

The present invention was devised to solve various problems of the conventional Al-Mg-Si-based extrusion aluminum alloy, to improve the extrudability by reducing the content of Mg, and to uniformly produce and distribute Mg ₂ Si. Accordingly, it is an object of the present invention to minimize the internal stress change caused by Mg ₂ Si precipitation to provide a high-strength aluminum alloy for extrusion, as well as excellent formability after extrusion.

This object of the invention is achieved by controlling the content of Mg.

The high-strength aluminum alloy for extrusion having excellent moldability of the present invention is an Al-Mg-Si alloy that has a strength suitable for automobile parts, and includes Si 0.95 to 1.05 wt%, Mg 0.5 to 0.6 wt%, and Mn 0.5 to 0.6 wt%. , Fe 0.15 ~ 0.25wt%, Cr 0.13 ~ 0.18wt%, Cu 0.05wt% or less, Ti 0.03wt% or less, Zn 0.05wt% or less, and other unavoidable components individually to 0.02wt% or less, the sum is 0.10 The wt% or less, and the balance of Al, the reason for the content limitation of each component is as follows.

Si is combined with Mg and precipitated as Mg ₂ Si by aging to influence the mechanical properties.Since combined with Mg, the remaining Si precipitates alone to improve mechanical properties and is effective for improving the fluidity of the melt. If the wt% is not reached, the desired strength cannot be obtained, and if it exceeds 1.05 wt%, not only the extrudability but also the surface quality of the extruded product is degraded.

Mg is a component that is precipitated with the Si and the compound to improve the mechanical properties, if the content is less than 0.5wt% Mg ₂ Si precipitate amount is insufficient to obtain the required strength, if exceeding 0.6wt% as a disadvantage to the extrusion flexible as in the case of over-Si as well as the risk of low intensity, the extrudable degradation by inhibiting the employment of an extra Mg Mg ₂ Si failed to form a Mg ₂ Si at the same time, the falling down of the productivity strength Will drop.

Mn improves the strength without deteriorating the corrosion resistance and is an effective component for grain refinement. If the content is less than 0.5wt%, Mn can obtain an effect of improving surface pick-up during extrusion by miniaturization of Mg ₂ Si. In addition, if the strength improvement effect due to miniaturization of the alloy structure is small and exceeds 0.6wt%, the transformation of the equilibrium α-AlFeSi phase into the non-equilibrium β-AlFeSi phase is promoted during the homogenization process, and thus the strength is increased. It tends to be lowered.

Fe is an ingredient that is effective in suppressing coarsening of recrystallized grains and miniaturizing crystal grains in casting.If it is less than 0.15wt%, Fe acts as an impurity, but the alloying effect is insignificant. It will also reduce the extrudability and productivity.

Cr inhibits the formation and growth of the recrystallized layer and forms a compound together with Al and Fe to distribute at the grain boundary, thereby inhibiting precipitation during aging and improving elongation. The content is 0.13wt%. If it does not reach, the recrystallization layer suppression effect is insignificant, the fatigue strength is lowered, and when it exceeds 0.18wt%, the extrudability is deteriorated.

Cu is a component that improves the flowability of the molten metal and improves the strength but lowers the corrosion resistance. When the content exceeds 0.05 wt%, Cu degrades the corrosion resistance, the weldability and the extrudability.

Ti is a component that is effective in refining particles, and when exceeding 0.03 wt%, the extrudability is reduced, and Zn is a component that improves corrosion resistance and mechanical properties, and when the content exceeds 0.05 wt%, Likewise, the extrudability is lowered.

In particular, the aluminum alloy of the present invention is improved in strength and extrudability and workability by adjusting the content of Si and Mn, which will be described below.

In order to accomplish the above object, by default, and the amount of precipitated and deposited in the form of Mg ₂ Si to be controlled with priority, it is In order that grain boundaries segregation at the same time that the amount of precipitation of the Mg ₂ Si to be adjusted to not more than 1.0wt% It should be suppressed, for this purpose it is to limit the content of Si and Mg to the above range.

Particularly, Mn plays a role of improving the strength and processability by minimizing the grain size and dispersing precipitate in the structure while minimizing segregation of Mg ₂ Si at the grain boundary during cooling after homogenizing the extruded material of the present invention. Rather, it promotes transformation of acicular β-AlFeSi into granular α-AlFeSi to improve the extrudability.

Further, by adding Mn together with Cr, these elements are efficiently dispersed in the structure, thereby preventing dislocation movement and recrystallization, thereby miniaturizing grains, thereby improving toughness and fatigue strength, as well as increasing temperature during extrusion. By suppressing the local melting phenomenon caused by the extrudeability.

In order to examine the characteristics of the aluminum alloy of the present invention having the composition as described above, the subframe was extruded after casting the example alloy of the present invention β and the commercially available 6082 alloy into billets. In Table 1, extrusion conditions and results are shown in Table 2 and mechanical properties in Table 3.

In addition, as shown in FIGS. 2 and 3, the structure photographs of the billets subjected to homogenization before extrusion are shown in FIGS. 2 and 3, and the needle-like precipitate is β-AlFeSi, which degrades the surface quality during extrusion and the mechanical properties of the extruded product.

Therefore, the needle-like β-AlFeSi should be changed to spherical α-AlFeSi. In the present invention, it was possible to transform β-AlFeSi into α-AlFeSi by controlling the amount of Mn added together with the homogenization treatment.

ββ classification Si Fe Cu Mg Zn Mn Cr Ti Al  Standard of the Invention 0.95-1.05 0.15 to 0.25 0.05 or less 0.5 to 0.6 0.05 or less 0.5 to 0.6 0.13 to 0.18 0.03 or less Balance Example 1 0.954 0.178 0.015 0.547 0.005 0.544 0.140 0.020 Balance Example 2 0.984 0.172 0.011 0.554 0.001 0.561 0.150 0.019 Balance Example 3 0.966 0.176 0.016 0.568 0.003 0.554 0.139 0.021 Balance Example 4 0.995 0.180 0.012 0.559 0.007 0.549 0.143 0.016 Balance Example 5 0.978 0.174 0.014 0.537 0.002 0.558 0.148 0.011 Balance Example 6 0.991 0.171 0.015 0.570 0.010 0.547 0.137 0.013 Balance Example 7 0.987 0.179 0.017 0.561 0.006 0.552 0.149 0.016 Balance Example 8 0.973 0.169 0.013 0.547 0.004 0.558 0.142 0.018 Balance Example 9 0.969 0.177 0.012 0.551 0.008 0.552 0.145 0.013 Balance maximum 0.995 0.180 0.017 0.570 0.010 0.561 0.150 0.021 at least 0.954 0.169 0.011 0.537 0.001 0.544 0.137 0.011 Average 0.977 0.175 0.014 0.555 0.005 0.553 0.144 0.016  Specified Standard 0.70 to 1.30 0.50 or less 0.10 or less 0.6 to 1.20 0.20 or less 0.40 to 1.00 0.25 or less 0.10 or less Balance Comparative Example 1 0.965 0.115 0.013 0.992 0.002 0.712 0.055 0.007 Balance Comparative Example 2 0.971 0.117 0.016 0.998 0.006 0.724 0.049 0.006 Balance Comparative Example 3 0.969 0.120 0.015 0.996 0.009 0.719 0.058 0.004 Balance Comparative Example 4 0.963 0.111 0.019 0.982 0.003 0.721 0.043 0.009 Balance Comparative Example 5 0.974 0.118 0.012 0.988 0.007 0.715 0.041 0.005 Balance Comparative Example 6 0.976 0.123 0.013 0.993 0.001 0.722 0.051 0.007 Balance Comparative Example 7 0.980 0.114 0.011 0.997 0.006 0.717 0.053 0.006 Balance Comparative Example 8 0.967 0.116 0.017 0.995 0.010 0.709 0.057 0.008 Balance Comparative Example 9 0.977 0.119 0.018 0.987 0.008 0.727 0.047 0.003 Balance maximum 0.980 0.123 0.019 0.998 0.010 0.727 0.058 0.009 at least 0.963 0.111 0.011 0.982 0.001 0.709 0.041 0.003 Average 0.971 0.117 0.015 0.992 0.006 0.718 0.050 0.006

          division    Example    Comparative Example   Temperature (℃)  Billet       480       490  Die       460       460  Container       420       420 Extruder pressure (kgf / cm ²⁾  Second pressure    190-200    210 to 220  Medium pressure    170-180    190-200  Horse    130 to 140    150 to 160   Puller speed (mm / sec)      8 to 10      6 to 8     Ram speed (mm / sec)      5 to 6      2-3   Outlet temperature (℃)             500-530

* Extrusion ratio: 44.3, Billet weight: 4,021 kg / m, hollow mold

  division Yield strength (N / mm ² ) Tensile Strength (N / mm ² )  Elongation (%)  Invention 1       281       338     16  Invention Material 2       281       337     16  Comparative material 1       270       313     13  Comparative material 2       272       316     11

The mechanical properties of Table 3 above are for the homogenized subframe after extrusion into the alloy of the present invention and the conventional 6082 alloy.

The alloy of the present invention is an improvement of the conventional 6082 alloy, the alloy composition range of the present invention overlaps most of the standard range of the conventional 6082 alloy, Si, Fe, Cr, etc., each composition range contained in the 6082 alloy While allowing the width to be adjusted within a specific range narrowed by 16-20%, Cu, Zn and Ti, etc., limit the maximum allowable amount to 50% or less, especially in the influence of Mg, which has a significant influence on the extrudability and mechanical properties. The technical feature is to reduce the overlap with the 6082 alloy.

That is, since the content of Mg is remarkably different from 54 to 58% of the conventional alloy, the difference in extrudability and strength occurs due to this difference, which means that extra Si that does not form Mg and Mg ₂ Si the result obtained by suppressing the employment of Mg ₂ Si.

As a result of the above results, as can be seen in Tables 2 and 3, the alloy of the present invention has further improved extrudability and excellent mechanical properties as compared with the conventional 6082 alloy.

As described above, the high-strength aluminum alloy for extrusion excellent in formability of the present invention by reducing the content of Mg, not only improves extrudability but also has high strength and optimum processability, thereby improving the quality of products with complex shapes and Together, there is an advantage to improve productivity.

Claims (2)

In Al-Mg-Si-based alloys, Si 0.95-1.05 wt%, Mg 0.5-0.6 wt%, Mn 0.5-0.6 wt%, Fe 0.15-0.25 wt%, Cr 0.13-0.18 wt%, Cu 0.05 wt% or less High strength aluminum for extrusion, characterized in that the Ti composition is 0.03wt% or less, Zn 0.05wt% or less and other unavoidable components of 0.02wt% or less, the sum of which is 0.10wt% or less, and the balance of Al. alloy. delete

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