Advantages

Market Status and Prospect Analysis

According to the data of the market research company IDC, the global sales of tablet PCs soared from the first quarter to the second quarter of 2011. Among them, the sales volume in the second quarter was 13.6 million units, a year-on-year increase of 303.8%, and the sales volume in the third quarter was 18.1 million units, a year-on-year increase of 264.5%. At the same time, IDC predicts that in 2012 the global...

If the original aluminum consumption of each tablet computer shell is 2kg, the aluminum consumption of this product in 2012 was 126,600 tons, which is about twice the aluminum consumption of rail vehicles, and the sales volume of tablet computers is not yet at an explosive period. As an electronic product, like a mobile phone, its replacement cycle is relatively short. With the rapid increase in penetration rate, the demand for tablet computers will be very large in the later stage, so this product will become another important market for industrial aluminum products.

Currently the main problem

As a high-end electronic product, the tablet computer has a strong decorative shell, which not only has good mechanical properties, but also requires a beautiful appearance. Therefore, for the machined and surface-treated aluminum casing, defects that can be found by the naked eye, such as black spots, miscellaneous spots, markings, and scratches, are not allowed. Because the machining is all CNC machining, the dimensional accuracy of the aluminum plate before machining is very high (the gap between planes with a width of 250mm cannot exceed 0.05mm), which brings great challenges to production. At present, many manufacturers in China are producing this product, but very few of them are really doing well. All of them have low yield and high scrap rate, especially the large amount of scrap after processing, resulting in a substantial increase in processing costs. The main flaws are as follows:

1. The plane gap is out of tolerance;

2. Dimensional accuracy is out of tolerance;

3. The indentation is too long;

4. Slag spots produced by oxides or other inclusions;

5. Coarse grains;

6. Low strength;

7. Layering, air bubbles, peeling;

8. Dark spots, snow spots.

Some of the above defects were discovered before machining, and the loss of a single piece caused by such scrapping is not very large, but the number is relatively large. This kind of scrapping is often caused by reasons such as plane gap tolerance, dimension tolerance and low strength, because these defects can be detected before machining. A considerable number of defects can only be found after chemical surface treatment after machining, and the loss of a single piece caused by such scrapping is very large. This kind of scrapping is often caused by slag spots, coarse grains, layers, bubbles, peeling, black spots, and snow spots caused by shrinkage, oxides or other inclusions.

key technology

There are many reasons for the above defects, including the inherent deficiencies of the production equipment, unreasonable design of the production process, and improper on-site control of the operator. To solve the above problems and greatly increase the rate of finished products and qualified rate, we mainly start from the following aspects:

1. Casting

1) Because the wall thickness of this type of product is relatively thick, the extrusion ratio is usually not large, and the metal deformation is not large during extrusion. Due to the very high requirements for the plane gap, the quenching strength should not be too large, so coarse grains are more likely to occur. In order to solve this problem, the grain size of the ingot must be considered in terms of alloy ratio, smelting process, and casting process. Some elements for refining grains should be appropriately added to strengthen the control of refining and casting cooling.

2) In order to prevent oxides or other inclusions from entering the ingot and entraining them into the extruded product, a good ceramic filter plate should be used during casting to effectively filter out oxides or other impurities.

2. Extrusion

1) In order to make the product uniform in structure and performance, the ingot should be homogenized, and the homogenization process can be carried out according to the ordinary 6063 alloy.

2) Since this product is a type with a single variety and a large batch, it is recommended to use a short ingot rapid heating furnace, preferably to make the ingot temperature gradient. The reasons are as follows: firstly, the deformation of the ingot end cut out by the current long ingot hot shearing machine is relatively large, which affects the subsequent peeling effect and easily causes the ingot skin to flow into the extruded product; secondly, there are a large number of cracks on the notch, It is difficult to exhaust completely during extrusion, which will cause bubbles in the extruded product; third, the rapid heating of the short ingot is conducive to maintaining the state after the homogenization of the ingot; fourth, the gradient heating of the short ingot (the temperature at the front end of the ingot is about 500 °C, the end temperature is about 460 °C), which is beneficial to reduce the formation of shrinkage of extruded products and is conducive to the consistency of mechanical properties of products.

From the comprehensive consideration of cost and ingot temperature control, I think it is best to use natural gas to heat first, and then use induction furnace to heat.

3) Ingot thermal peeling

In order to prevent sundries such as oxide skin on the surface of the ingot from entering the extruded product, the ingot should enter the ingot holding cylinder after heating and proceed to "peeling" treatment to remove the cast skin and so on. The thickness of the peeling is related to the diameter of the ingot and the quality of the ingot, usually 3-5mm.

4) Quenching treatment

Because the product is in 6063 T6 state, and the wall thickness is relatively thick, the plane clearance requirements are relatively high. If air cooling is used, the cooling rate is too low, the quenching effect is not good, the product grains are too large, and the mechanical properties are low. If the water tank or spray cooling is used, the cooling speed is too fast and the cooling is uneven, resulting in serious product deformation and out-of-tolerance plane clearance. To solve this problem, a combination of multiple cooling forms should be used. After testing, the best solution is to mix and cool the first 4-5 meters with wind and mist, reduce the temperature of the product to about 250 degrees, and then spray it with 1-2 meters. Of course, the layout of spraying should be particular, and all points around the product must be cooled evenly. After this quench, the product temperature drops to about 100°C. If you add a section of air cooling (4 meters is better), the effect will be better. This treatment can not only meet the requirements of cooling strength, give full play to the mechanical properties of the alloy, but also reduce the deformation of the product, ensure the requirements of the plane gap, and avoid the appearance of defects such as water marks and black spots. This link is very important, but often easily overlooked.

Aluminum profile extrusion is a systematic project, and each link will have a great impact on product quality, and each link should attract sufficient attention. The link introduced above is what should be paid attention to when this product is different from other building material products, and it is often easily overlooked by people, so I will make a key point to explain, hoping to be helpful to the manufacturer.