WO2011059412A2

WO2011059412A2 - Aluminium alloy which is able to be cast by high pressure die casting technique and results in better mechanical properties aluminium alloy product without heat treatment

Info

Publication number: WO2011059412A2
Application number: PCT/TH2010/000042
Authority: WO
Inventors: Masao Montani
Original assignee: Daiki Aluminium Industry (Thailand) Company Limited
Priority date: 2009-11-13
Filing date: 2010-11-12
Publication date: 2011-05-19
Also published as: WO2011059412A3

Abstract

Aluminium alloy comprising of Silicon at 6.0 to 12.0 percent, Magnesium at 0.5 to 1.0 percent, Chromium at 0.1 to 0.5 percent, Iron at below 0.5 percent and Aluminium with other unavoidable substances for the remaining percentage. This newly invented aluminium alloy possesses high enough proof strength, tensile strength and elongation to produce car parts and motorcycle parts that require toughness even without any heat treatment application.

Description

ALUMINIUM ALLOY WHICH IS ABLE TO BE CAST BY HIGH PRESSURE DIE CASTING TECHNIQUE AND RESULTS IN BETTER MECHANICAL PROPERTIES ALUMINIUM ALLOY PRODUCT WITHOUT HEAT TREATMENT

TECHNICAL FIELD

Metal chemical industry and metallurgical engineering which relate to the process of mixing and casting aluminium alloy

BACKGROUND ART

Pure aluminium has low tensile strength but can easily be blended with other elements, for example; copper, zinc, magnesium, manganese, and silicon (i.e. duralumin), in order to make aluminium alloy which is mostly used in industrial field.

Formerly, in order to make an aluminium alloy product that needs durability, hardness, and/or bendability, one will employ aluminium alloy, named, ADC12 to the Gravity Permanent Mold Technique (GPM) by melting the aluminium and pour the molten metal into the permanent metal mold. Later on, there has been a new casting technique, called High Pressure Die Casting, which can produce more works within the same duration. This technique is done by injecting molten aluminium into a die which is engaged to each other by high pressure in order to get the desired shape aluminium alloy product. After that the aluminium will be taken out of the die and got through heat treatment process in order to get the required mechanical properties.

Aluminium alloy that has formerly been used is ADC 12, which is categorized in Al-Si- Cu group. ADC12 has compositional percentage as follows; Silicon 9.6-12.0, Iron 0-1.3, Copper 1.5-3.5, Manganese 0-0.5, Magnesium 0-0.3, Zinc 0-1.0, Nickel 0-0.5, Tin 0-0.3, others 0-0.15, and the rest is Aluminium. ADC12 has already been granted a U.S. patent, application number 10/100,054, and filed international application under Patent Cooperation Treaty (PCT), application number PCT/US03/08269. Casting of this type of aluminium alloy by applying high pressure die casting technique will yield a better mechanical properties product and it is easier to cast ADC 12 by this technique than using the gravity permanent mold technique. As the result, ADC 12 is idely used with high pressure die casting technique in industrial fields nowadays. Most of the uses are to produce covers and cases of cars; however, there are several other products apart from cars that use ADC 12 to produce as well.

However, if one wants to cast ADC 12 to have enough strength to produce vehicle parts that require toughness such as covers, cases or carburetors, a heat treatment process must be applied to the product (the heat treatment process is the process that adjusts the mechanical properties of the product by leaving the product to cool down without applying a solution treatment. After that, artificial age treatment shall be applied by maintaining the temperature at the required level at a specific period of time, not less than 3 hours, and use wind blow to cooling off the products. The temperature and duration will differ depending on the type of treatment i.e. T5 will use 170 degrees Celsius for 3 hours while T6 will use higher temperature and duration) so that the toughness of the product will be improved to meet the designated level of toughness for each kind of parts.

Currently, the increases of producers of car parts and other metal parts used in other industrial fields cause price competitions and the global warming thought creates many energy saving campaigns. However, the making of high toughness aluminium alloy product by using ADC 12 requires high level of heat in high pressure die casting and heat treatment. The post- casting heat treatment for mechanical properties modification consumes more than 3 hours. This causes waste of huge amount of energy and costs.

SUMMARY OF INVENTION

The kind of aluminium alloy widely used in many industries with high pressure die casting technique nowadays is ADC 12. However, the aluminium product made by ADC 12 has not enough proof strength in its mechanical properties to be used as a car, motorcycle or machinery part that have to bear frequently repeated vibration, load and heavy crashes such as carburetor, cylinder block etc. unless it has passed heat treatment process. The heat treatment process is a time and energy consuming process. This absolutely means more cost to aluminium alloy product producers.

This new invention is an aluminium alloy that possesses high mechanical properties enough to make a car, motorcycle or machinery part that requires high toughness after the aluminium alloy has been cast by high pressure die casting technique without any heat treatment. The present invention can be achieved by mixing chemical compounds of the aluminium alloy in this following weight percentage and melt it together:

Silicon at 6.0 to 12.0 percent,

Magnesium at 0.5 to 1.0 percent,

• Chromium at 0.1 to 0.5 percent,

Iron at below 0.5 percent and

Aluminium with other unavoidable substances for the remaining percentage When one casts this invented aluminium alloy into a product by high pressure die casting technique, the yielded product will have high mechanical properties, close to those of post heat treatment ADC 12 aluminium alloy product, even though none of heat treatment has been applied upon. This can save a lot of energy, cost and time of aluminium alloy product producers.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 shows the photo of the invented aluminium alloy's microstructure of the sample 2 of table 3.

Figure 2 shows the photo of the invented aluminium alloy's microstructure of the sample 4 of table 3.

Figure 3 shows the photo of the ADC12 aluminium alloy's microstructure.

Figure 4 shows the graph of the invented aluminium alloy's mechanical properties of the 7 samples of table 3.

Figure 5 shows the table of the comparison between the mechanical properties of the invented aluminium alloy that is combined as the sample 2 of table 3 and ADC12.

DETAILED DESCRIPTION

This invention relates to an aluminium alloy that will possess better mechanical properties after high pressure die casting in comparison with its widely used prior art, ADC 12. This newly invented aluminium alloy can be used to make aluminium alloy products that require toughness such as car parts etc. by high pressure die casting technique without necessity to further improve its mechanical properties by heat treatment process.

In order to make this invention, first, the materials for essential compositions shall be prepared as follows:

This invented "Aluminium alloy which is able to be cast by high pressure die casting technique and results in better mechanical properties aluminium alloy product without heat treatment" has been blended with Silicon at the percentage of 6.0 to 12.0 per weight. An addition of Silicon will reduce the temperature of the casting process. If the quantity of Silicon is less than 6.0 percent, the temperature in the casting process will be higher and the fluidity of molten body of the aluminium alloy will be decreased, then, the flow of the molten body cannot be well-controlled. On the other hand, if the quantity of Silicon is more than 12 percent, the molten body will have good fluidity but there will be too low elongation to meet the required mechanical properties. Therefore, the amalgam of Silicon between these percentages will increase the molten aluminium's fluidity so that it will be able to flow into the groove of the die properly and results in complete products in desired shape while having high elongation. Moreover, adding of Silicon, in order to reduce the casting's temperature, even helps prolong the die's life because the lower temperature of the casting will reduce the probability of soldering occurrence and the degree of the heat that the die has to withstand.

This newly invented aluminium alloy is comprising of Iron at below 0.5 percent per weight quantity which is lower than the percentage of Iron in ADC 12. Addition of Iron into the alloy can prevent soldering but if the quantity of Iron is higher than 0.5 percent, toughness of the alloy will be lower. Therefore, the proper percentage of Iron in the new aluminium alloy shall be below 0.5 percent. Furthermore, adding Iron into an aluminium alloy will cause raphides form structure since this aluminium alloy is categorized in Al - Si - Fe group, as the result, there is a probability that aluminium alloy ingot will be cracked after cooled down. However, the cracking of aluminium alloy ingot can be solved by adding Chromium in to the aliminium alloy.

Chromium shall be added into this invented aluminium alloy at the amount between 0.1 to 0.5 percent per weight. This will change raphides structure caused by adding Iron. When Chromium becomes solid form, it will merge with aluminium alloy and results in Al - Si - Cr - Fe and the alloy's microstructure will be in curved shape as seen in Figure 1, Besides changing raphides structure, adding Chromium into aluminium alloy in this percentage can also reduce soldering problem. There is evidence that addition of chromium in the percentage of less than 0.1 causes more chance of soldering than one defined above. However, adding of Chromium more than 0.5 percent will result in decreases of aluminium alloy's elongation.

This new invention shall also have Magnesium as one of its essential compounds at the proportion of 0.5 to 1.0 percent. Even though most of aluminium alloy materials already contain Magnesium in Mg₂Si compound but, in order to produce this newly invented aluminium alloy, the percentage of Magnesium per weight shall be controlled to be within 0.5 to 1.0 percent. Adding Magnesium at this percentage will increase toughness and tensile strength of the alloy. However, if the percentage of Magnesium in an aluminium alloy is lower than 0.5 percent, the alloy's proof strength and tensile strength will not be good enough. If the percentage of Magnesium in an aluminium alloy is higher than 1.0 percent, the alloy's elongation will be reduced. This new invention shall contain Aluminium and unavoidable substances for the remainders.

After all materials and the essential compounds mentioned earlier have been prepared, they will be put in either the open wall or close packed furnace to get molten aluminium alloy. When the materials are molten, there might be a purification process as necessary such as dehydrogen treatment of the aluminium alloy molten body or removing adulterants. The purified molten body will then flown to the prepared die and become solid following the shape of the die used i.e. aluminium alloy ingot and/or other shapes of the dies used. This aluminium alloy ingot can be cast to produce aluminium alloy products.

Unlike ADC 12 that requires heat treatment to improve its mechanical properties, Applying high pressure die casting technique to this invented aluminium alloy to make products in absence of a heat treatment process will yield aluminium alloy products that possess high enough mechanical properties (such as toughness, proof strength, tensile strength and elongation) to make car parts, motorcycle parts or machinery parts that have to bear frequently repeated vibrations, loads and heavy crashes such as carburetor, cylinder block, wheel and spokes etc. The average mean of the invented aluminium alloy and ADC 12 before heat treatment are as specified in the Table 2 herein.

Furthermore, when comparing the mechanical properties of 7 samples of this invented aluminium alloy with a sample of ADC 12 then take it to the T5 heat treatment process, the result will be as shown in Table 3.

When we bring the comparison of 7 samples of the invented aluminium alloy and a sample of ADC 12 after T5 heat treatment to make a graph, the graph will be as appeared in Figure 4. In the case where a formula of the invented alloy has to be chosen to compare to ADC 12, the result will be as shown in Figure 5 (In this case sample 2 is chosen.). The results of all statistics show that the mean of mechanical properties of the invented aluminium alloy, after heat treatment, in part of tensile strength is close to the tensile strength level of ADC 12, however, proof strength and elongation of the invented aluminium alloy are much higher than _ild C ₍%₎ E_l R_ttom_pon_sssenaue_su_s

those of ADC 12. The number of tensile strength of the invented aluminium alloy can be higher than the one of ADC 12 if the chosen sample is switched to some other samples such as sample 7. Therefore, the mechanical properties requirement of the desired product will decide what formulae of the invented aluminium alloy will be chosen and applied. It should be noted that pre-heat treatment version of the invented aluminium alloy also has high level of mechanical properties comparing with post-heat treatment ADC12.

Sample Sample Sample Sample Sample Sample Sample ADC 1 2 3 4 5 6 7 12

Si 7.02 7.12 9.40 9.47 9.50 9.89 10.2 11.4 g 0.58 0.76 0.62 0.52 0.62 0.60 0.58 0.23

Cr 0.29 0.29 0.31 0.31 0.43 0.31 0.43 0.02

Fe 0.45 0.47 0.41 0.40 0.45 0.09 0.47 0.62

Cu - - - - - - - 2.46

Zn - - - - - - - 0.83

Heat Treatment T5 T5 T5 T5 T5 T5 T5 T5

Tensile

Strength

321 337 355 347 351 350 353 345

(N/mm²)

Elongation

4.9 4.0 3.8 4.3 3.6 3.7 3.7 1.3 (%)

0.2%Proof

Strength

239 262 265 254 266 236 263 206

(MPa)

Table 3: Comparison of mechanical properties of 7 samples of invented aluminium alloy and a sample of ADC 12 after T5 Heat Treatment

Claims

CLAIMS What is claimed:

1. An aluminium alloy consists essentially of the following constituents by percentage of weight: Silicon at the amount between 6.0 to 12.0 percent, Magnesium at the amount between 0.5 to 1.0 percent, Chromium at the amount between 0.1 to 0.5 percent, Iron at the amount less than 0.5 percent and the remainders shall be aluminium and other unavoidable substances. ,

2. The aluminium alloy according to claim 1, wherein the aluminium alloy is in fluid or solid forms.

3. The aluminium alloy according to any of claim 1 to 2, wherein the aluminium alloy is casted by utilizing a high pressure die casting technique.

4. The aluminium alloy according to any of claim 1 to 2, wherein the aluminium alloy is casted by utilizing Gravity Permanent Mold Technique.

5. The aluminium alloy according to any of claim 1 to 4, wherein the heat treatment is applied to the aluminium alloy.

6. The aluminium alloy product made from the aluminium alloy according to any of claim 1 to 4, wherein the heat treatment is applied to the aluminium alloy products.

7. The aluminium alloy or aluminium alloy product according to any of claim 5 to 6, wherein the heat treatment comprises:

leaving the casted aluminium alloy product to cool down without applying a solution treatment; and

applying an artificial age treatment by using 160 to 180 degree Celsius temperature constantly for at least 3 hours.

8. The aluminium alloy or aluminium alloy product according to any of claim 5 to 6, wherein the heat treatment comprises:

applying a solution treatment by using 922 degree Fahrenheit to 942 degree Fahrenheit temperature for at least 4 hours; and

water quenching; and

applying an artificial age treatment by using 346 to 366 degree Fahrenheit temperature constantly for at least 5 hours.

9. The aluminium alloy or aluminium alloy product according to any of claim 5 to 8, wherein the aluminium alloy or aluminium alloy product is casted by utilizing a high pressure die casting technique.

10. The aluminium alloy or aluminium alloy product according to any of claim 5 to 8, wherein the aluminium alloy or aluminium alloy product is casted by utilizing Gravity Permanent Mold Technique.

11. An aluminium alloy ingot or plate, wherein the aluminium alloy ingot or plate is made from the aluminium alloy or aluminium alloy product according to any of claim 1 to 10.

12. A wheel or a spoke or any part of a wheel of a car or motorcycle, wherein the wheel, spoke or part of wheel is made from the aluminium alloy or aluminium alloy product according to any of claim 1 to 11.

13. A part of a car or part of an industrial equipment or part of electric device, wherein the part of a car or part of an industrial equipment or part of electric device is made from the aluminium alloy or aluminium alloy product according to any of claim 1 to 11.