KR20080001328A - Al-alloy for forging - Google Patents

Abstract

A method for manufacturing a forging aluminum alloy is provided to improve forging efficiency of an aluminum-magnesium alloy and to cut down a cost by increasing productivity of the forging aluminum alloy. A method for manufacturing a forging aluminum alloy includes a casting process, a leveling process, and a cooling process. The leveling process is performed at 470~490 degrees for 10~14 hours. The aluminum alloy is formed by 2.8~3.0 weight% of magnesium, under 0.03 weight% of silicon, under 0.03 weight% of iron, 0.07~0.08 weight% of copper, 0.018~0.022 weight% of titanium, 0.01 weight% of each inevitable element, and extra aluminum. The cooling process is performed at cooling speed over 200 degrees per hour to prevent a solidified compound from being precipitated.

Description

Manufacturing method of forging aluminum alloy {Al-alloy for forging}

1 is a correlation graph of homogenization treatment temperature and hardness.

The present invention relates to an Al-Mg-based aluminum alloy that is excellent in forging properties and optimized as a lightweight component material for automobiles.

Aluminum is the second most used metal after steel, and it is lightweight, has good corrosion resistance and workability, and has high electrical and thermal conductivity. It also contains elements such as Cu, Mg, Si, Zn, Mn, and Ni, and various kinds of high strength and high corrosion resistance alloys. It is used throughout the home and industry fields 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.

According to the above-mentioned demand for lightening automobiles, auto parts are mainly manufactured by a low pressure casting method. However, when forging aluminum is used, an aluminum part having a stronger strength than that produced by the low pressure casting method may be manufactured.

In other words, Al-Si die casting aluminum alloys were mainly used in low pressure casting.Since the range of Si addition amount is large, alloys with easy flowability and melt filling or alloys with low casting crack can be selectively manufactured by controlling the Si content. Could.

However, the conventional low pressure casting method has a disadvantage in that the material recovery rate is low and the post-process cost is high, and the Al-Si-based alloy manufactured by the low pressure casting has a disadvantage in that it does not contribute to the weight reduction of the automobile.

The present invention was devised to solve all the problems of the conventional low-pressure casting aluminum alloy as described above, to improve the forgeability of the Al-Mg-based alloy of the whole-body alloy, and to increase the productivity by improving the forgeability The purpose of the present invention is to provide a method of manufacturing an aluminum alloy having excellent forging ability to be used, for example, an aluminum wheel, which is an automobile light weight component.

The above object of the present invention is achieved by controlling the Mg, Si, Fe, Cu and Ti content of the alloying components and the homogenization treatment after casting.

The method of manufacturing the forging aluminum alloy of the present invention comprises a sequential process such as a casting step, a homogenization treatment step, and a cooling step, and the homogenization treatment temperature is performed at 470 to 490 ° C. for 10 to 14 hours. There is a characteristic, and the composition of the alloy should be limited as follows to have excellent forging property by the homogenization treatment.

That is, the aluminum alloy according to the method of the present invention, Mg 2.8 to 3.0% by weight, Si 0.03% by weight or less, Fe 0.03% by weight or less, Cu 0.07 to 0.08% by weight, Ti 0.018 to 0.022% by weight, 0.01% of other unavoidable components 0.01% It is composed of% or less and the residual amount of Al, and the reason for limiting the content of each component as described above is as follows.

Mg is a solid solution strengthening element. If the content is less than 2.8% by weight, its effect is insignificant, and as the Mg content increases, the deformation resistance under hot processing becomes high, making it difficult to process. When the content exceeds 3% by weight, Mg ₂ Al ₃ precipitates during the low temperature heat treatment or cooling at high temperature, thereby lowering the mechanical characteristic value, and excessive Mg decreases the solid solubility of Mg ₂ Si so that an appropriate homogeneity cannot be obtained.

Si is combined with Mg and precipitated as Mg ₂ Si by aging to influence the mechanical properties, and the remaining Si combined with Mg is precipitated alone to improve the mechanical properties and effective for improving the fluidity of the melt, but 0.03 When the weight percentage is exceeded, toughness is lowered while increasing the strength more than necessary while forming Mg ₂ Si, which adversely affects forging properties.

Fe is effective in suppressing coarsening of recrystallized grains and miniaturizing grains in casting, but when it exceeds 0.03% by weight, Fe acts as an impurity, while alloying effects are insignificant, and ductility is reduced. It will promote contact corrosion. In addition, the AlFeSi compound is formed, which degrades the hot workability and promotes wear of the mold.

Cu is a component added for the purpose of suppressing the stress corrosion cracking of Al-Mg alloy. If the content is less than 0.07% by weight, the effect is insignificant, but when it exceeds 0.08% by weight, the hardness is increased more than necessary. The workability will be reduced.

Ti is a component that is effective for fine graining, and when it is less than 0.018% by weight, the effect of addition cannot be obtained. When Ti exceeds 0.022% by weight, the workability is deteriorated.

And, after casting the aluminum alloy of the composition as described above is subjected to silicidation treatment, if the temperature does not reach 470 ℃ during the homogenization treatment, the nonuniformity between the alloy surface and the internal structure becomes large and the forging is inferior When the temperature exceeds 490 ° C., the low melting point compound in the alloy may be locally dissolved, thereby preventing the original shape of the cast shape from being maintained.

    In addition, as a thick oxide layer is formed on the surface of the alloy by high temperature oxidation, forging property as well as surface quality deterioration may be caused, and manufacturing cost is increased.

In the case of homogeneous time, another variable of the homogenization treatment, if it does not reach 10 hours, sufficient homogenized tissue cannot be obtained, and if it exceeds 14 hours, the manufacturing cost is increased by unnecessary energy consumption. In particular, when less than the minimum time, the non-uniformity of the alloying components will result in the presence of segregation and reverse segregation layer adversely affects the workability.

Cooling, which is the final step, is preferably possible because of quenching, which is to prevent precipitation of compounds dissolved in the matrix during the cooling process.

The characteristics of the aluminum alloy manufactured by the above method will be described as follows.

Example

Since the billet was manufactured by the air slip method, its composition and production conditions are as shown in Table 1 and Table 2, respectively.

  division Alloy number                      Ingredient Content (wt%)   Cu   Si   Fe   Mn   Mg   Zn   Cr   Ti   Ni    Comparative Example   One 0.080 0.050 0.173 0.011 2.905 0.014 0.021 0.049 -   2 0.079 0.049 0.142 0.011 2.989 0.019 0.016 0.088 -   3 0.083 0.050 0.076 0.008 2.963 0.011 0.002 0.028 -   4 0.200 6.952 0.185 0.086 0.310 - - 0.125 0.024  Example   5 0.070 0.020 0.040 0.001 2.950 0.002 0.003 0.010 -

 division  Alloy number Casting speed (mm / min) Cooling condition    Melting temperature (℃)     Homogeneous / cooling condition  Cooling water amount (l / min) Coolant temperature (℃) Early normal Early normal Holding furnace Distribution box  Temperature (℃) Retention time Cooling time (hr)   Comparative Example   One  50  63  900 2270   21  730  715  560 11.5    4   2  50  64  700 2130   26  745  735  560 15    4   3  52  64  800 1900   21  730  715  540 14    4   4  -  -   - -   -   -   -   -  -    - Example   5  50  65  750 1750   22  700   -  480 12    4

Comparative Example 4 in Table 2 shows the general chemical composition of the aluminum alloy prepared by a conventional low pressure casting method.

Due to the characteristics of the Al-Mg-based aluminum alloy, the recrystallization temperature decreases as the homogenization heat treatment temperature increases. Therefore, the homogeneous heat treatment temperature was changed as shown in Alloy Nos. 1 to 3 in consideration of the forging property, and the rest of the casting conditions were the same. .

Based on the experimental results of Alloy Nos. 1 to 3, alloy components, casting conditions, and homogenization heat treatment conditions of Alloy No. 5, which are examples of the present invention, were derived.

As a result of the hardness test for the improved alloy cast by varying the homogenization heat treatment temperature is shown in Figure 1, the lower the homogenization heat treatment temperature can be seen that the hardness decreases. It can be seen that the pressure required for forging is also reduced.

As described above, the aluminum alloy manufactured according to the present invention has advantages in that the forging property is improved as compared with the conventional in situ aluminum alloy, and the manufacturing cost can be reduced by improving productivity by improving the forging property.

Claims (2)

Melting and casting the aluminum alloy; Homogenizing at 470-490 ° C. for 10-14 hours; Method for producing a forging aluminum alloy comprising the step of cooling at a cooling rate of 200 ℃ / hr or more. According to claim 1, The aluminum alloy, Mg 2.8 to 3.0% by weight, Si 0.03% by weight or less, Fe 0.03% by weight or less, Cu 0.07 to 0.08% by weight, Ti 0.018 to 0.022% by weight, 0.01% of other unavoidable components 0.01% A method for producing an aluminum alloy for forging, characterized in that the composition of less than% and the remaining amount of Al.

Images