1. Alloying elements
6063 alloy is an alloy made of aluminum, magnesium and silicon as the main elements. Each element has a certain range of content, and the price of magnesium is high. In order to reduce costs, some manufacturers reduce the amount of magnesium to the minimum allowable content. Some even go so far as to lower the magnesium content below the minimum allowable level. There are also factories that add waste wires and waste pots and waste aluminum pots to the alloy, which is basically not 6063 alloy. As a result, the mechanical strength of the aluminum profile is very low, which can be so low that it is easy to bend with both hands, commonly known as soft like noodles. This is one of the reasons why aluminum can be thousands of dollars cheaper.
Regular aluminum manufacturers have internal standards when formulating alloy components, that is, within the content range of various elements, each factory has its own smaller variation range, and the ratio of aluminum, magnesium, and silicon is very strict. Each factory has its own data, which is kept secret from each other. The quality of the alloy can only be guaranteed if there is a qualified formula, otherwise the quality will not improve in the future.
2. Aluminum alloy melting furnace
How to melt the prepared 6063 alloy and what furnace to use are also crucial. The furnaces used in China now range from the level of the 1940s to the 1990s. The worst manufacturers use original crucible boilers. There are coal-burning, oil-burning, gas-burning and electric heating smelting furnaces. Some stoves have chimneys, and some stoves have no chimneys. Generally, square furnaces (rectangular furnaces) are used, and advanced ones are circular furnaces, and some circular furnaces can be tilted to pour aluminum water. In terms of tonnage, there are one-ton, two-ton, five-ton, ten-ton, twenty-five-ton and fifty-ton aluminum melting furnaces. More advanced, add a static furnace under the aluminum melting furnace, the static furnace is mainly used for preparing 6063 alloy, in this furnace, slag and gas can be removed, static, and then aluminum rods can be cast for extrusion. The quality of the alloy prepared in the original coal-fired furnace and the modern circular furnace is absolutely different. Generally, no matter what kind of fuel is burned, there should be a chimney, and most of the waste gas and residue generated during the combustion of fuel can be discharged from the chimney. If there is no chimney exhaust gas and waste slag is completely melted in aluminum water, the aluminum rod for extrusion will have serious slag inclusion bubbles inside, which is one of the reasons for the poor quality of aluminum materials and one of the reasons for the cheap aluminum price.
3. Alloy casting
The level of domestic casting equipment is also very different. The oldest domestic casting equipment includes iron mold casting at the level of the 1940s, and the advanced hydraulic semi-continuous casting. Iron mold casting cast rods have poor crystallization structure, and there are a lot of slag inclusions and bubbles in the cast rods, and the quality of cast rods is very poor. Now the general factories use horizontal casting (also known as continuous casting) and semi-continuous casting. , semi-continuous casting most of the wire rope transmission, the best hydraulic transmission. Semi-continuously cast rods are available in varying lengths, typically 3m, 4m up to 8m. The semi-continuous casting is a pit type, casting down while casting, and cooling with cold water on all sides. Because the water is evenly cooled around, the crystal structure of the cast rod is uniform and fine. However, the downward transmission of the steel wire rope is not as stable as the hydraulic transmission, and the surface of the casting rod of hydraulic casting is smoother than that of other casting rods. A smooth surface of the cast rod is one of the prerequisites for extruding a good profile. The surface of the cast rod cast by other methods is relatively rough. In order to ensure the quality of the profile, sometimes the cast rod is turned first to remove the rough appearance of the cast rod. The semi-continuous casting mold commonly used now is an advanced casting mold with the same level as the hot top. The characteristics of this casting mold can cast several to dozens of pieces at a time, and the casting quality is good at the same time. With high-quality 6063 aluminum alloy casting rods Only in this way can it be possible to produce good aluminum profiles. If it is impossible to cast good cast rods with original and old casting equipment, it is impossible to produce good aluminum profiles at all. There are many aluminum factories in China that do not have the equipment to produce aluminum rods. Instead, they purchase 6063 alloy rods from electric aluminum factories or other factories. In such aluminum factories, the quality of aluminum is in the hands of the casting rod factory, and the aluminum produced is It is difficult to achieve stable quality of materials. Compared with advanced casting equipment, the use of backward equipment is less investment and lower production costs, which is one of the reasons why the price difference of aluminum products is large.
4. Profile extrusion
There are various types of profile extrusion machines in my country, and the grades vary greatly, which is also the highest in the world. There are simple extruders of the factory itself, some are modified by extruding plastic machines, a small amount are made in China, followed by most of them are from Japan, the United States and Germany, with water pressure and oil pressure. In short, there are hundreds of extrusion machines in China. It is generally believed that Japanese, American and German extruders are better. Good and bad extruders, the same casting rod, the quality of the extruded profile is absolutely the same. We often see 6063T5 used for architectural aluminum doors and windows, which is an American brand used internationally.
The Chinese trademark is LD31RCS. Both T5 and RCS indicate the state, which means the state of air-cooling and quenching artificial aging. The quenching of metal is quenching when high temperature suddenly drops to low temperature. For example, the blade of a steel knife must be quenched in water to be hard and sharp, while the quenching of aluminum also has water-cooling quenching and air-cooling quenching. The 6063 profiles used in construction are air-cooled and quenched, and the quenched aluminum is placed in an aging furnace for a certain period of time, and the internal crystals of the aluminum are rearranged, and the mechanical strength is significantly improved. Among all metal alloys, only aluminum alloy has an aging state.