What is aluminum ingot ?
Aluminum is a silver-white metal and ranks third in the earth's crust after oxygen and silicon. The density of aluminum is relatively small, only 34.61% of iron and 30.33% of copper, so it is also called light metal. Aluminum is a non-ferrous metal whose output and consumption are second only to steel in the world. Because aluminum is light, it is often used in the manufacture of land, sea and air vehicles such as automobiles, trains, subways, ships, airplanes, rockets, and spacecraft to reduce its own weight and increase the load. The raw materials in our daily industry are called aluminum ingots. According to the national standard (GB/T 1196-2008), they should be called "aluminum ingots for remelting", but everyone is used to calling them "aluminum ingots". It is produced by electrolysis using alumina-cryolite. After aluminum ingots enter industrial applications, there are two major categories: cast aluminum alloys and deformed aluminum alloys. Cast aluminum and aluminum alloys are aluminum castings produced by casting methods; deformed aluminum and aluminum alloys are processed aluminum products produced by pressure processing methods: plates, strips, foils, tubes, rods, shapes, wires and forgings. According to the national standard, "remelting aluminum ingots are divided into 8 grades according to chemical composition, which are Al99.90, Al99.85, Al99.70, Al99.60, Al99.50, Al99.00, Al99.7E, Al99. 6E” (Note: The number after Al is the aluminum content). Some people call "A00" aluminum, which is actually aluminum with a purity of 99.7%, which is called "standard aluminum" in the London market. Our country’s technical standards in the 1950s came from the former Soviet Union. "A00" is the Russian brand in the Soviet Union’s national standards. "A" is a Russian letter, not the English "A" or the "A" of the Chinese phonetic alphabet. If it is in line with international standards, it is more accurate to call "standard aluminum". Standard aluminum is an aluminum ingot containing 99.7% aluminum, which is registered on the London market.
How are aluminum ingots made
The aluminum ingot casting process uses molten aluminum to inject into the mold, and after it is taken out after being cooled into a cast slab, the injection process is a key step for the quality of the product. The casting process is also the physical process of crystallizing liquid aluminum into solid aluminum.
The process flow of casting aluminum ingots is roughly as follows: Aluminium tapping-slagging-picking up-ingredients-furnace loading-refining-casting-aluminum ingots for remelting-finished product inspection-finished product inspection-warehousing aluminum out-slagging off-picking up- Ingredients-furnace loading-scouring-casting-alloy ingots-casting alloy ingots-finished product inspection-finished product inspection-warehousing
Commonly used casting methods are divided into continuous casting and vertical semi-continuous casting
Continuous casting can be divided into mixed furnace casting and external casting. All use continuous casting machines. Mixing furnace casting is the process of casting molten aluminum into the mixing furnace, and is mainly used to produce aluminum ingots for remelting and casting alloys. Outer casting is carried out directly from the ladle to the casting machine, which is mainly used when the casting equipment cannot meet the production requirements or the quality of the incoming materials is too poor to be directly fed into the furnace. Since there is no external heating source, it is required that the ladle has a certain temperature, generally between 690°C and 740°C in summer and 700°C to 760°C in winter to ensure that the aluminum ingot has a better appearance.
For casting in the mixing furnace, the ingredients must first be mixed, then poured into the mixing furnace, stirred evenly, and then added with flux for refining. The casting alloy ingot must be clarified for more than 30 minutes, and the slag can be cast after clarification. During casting, the furnace eye of the mixing furnace is aligned with the second and third molds of the casting machine, which can ensure a certain degree of mobility when the liquid flow changes and the mold is changed. The furnace eye and the casting machine are connected with a launder. It is better to have a shorter launder, which can reduce aluminum oxidation and avoid vortex and splashing. When the casting machine is stopped for more than 48 hours, the mold should be preheated for 4 hours before restarting. The molten aluminum flows into the mold through the launder, and the oxide film on the surface of the molten aluminum is removed with a shovel, which is called slagging. After one mold is filled, the launder is moved to the next mold, and the casting machine advances continuously. The mold advances in sequence, and the molten aluminum gradually cools down. When it reaches the middle of the casting machine, the molten aluminum has solidified into aluminum ingots, which are marked with a melting number by the printer. When the aluminum ingot reaches the top of the casting machine, it has completely solidified into an aluminum ingot. At this time, the mold is turned over, and the aluminum ingot is ejected from the mold, and falls on the automatic ingot receiving trolley, which is automatically stacked and bundled by the stacker to become the finished aluminum ingot. The casting machine is cooled by spraying water, but the water must be supplied after the casting machine has been turned on for one full revolution. Each ton of molten aluminum consumes about 8-10t of water, and a blower is required for surface cooling in summer. The ingot is a flat mold casting, and the solidification direction of the molten aluminum is from bottom to top, and the middle of the upper part solidifies finally, leaving a groove-shaped shrinkage. The solidification time and conditions of each part of the aluminum ingot are not the same, so its chemical composition will also be different, but it is in line with the standard as a whole.
Common defects of aluminum ingots for remelting are:
① Stoma. The main reason is that the casting temperature is too high, the molten aluminum contains more gas, the surface of the aluminum ingot has many pores (pinholes), the surface is dark, and hot cracks occur in severe cases.
② Slag inclusion. The main reason is that the slagging is not clean, resulting in slag inclusion on the surface; the second is that the temperature of the molten aluminum is too low, causing internal slag inclusion.
③Ripple and flash. The main reason is that the operation is not fine, the aluminum ingot is too large, or the casting machine is not running smoothly.
④ Cracks. Cold cracks are mainly caused by too low casting temperature, which makes the aluminum ingot crystals not dense, causing looseness and even cracks. Thermal cracks are caused by high casting temperature.
⑤ Segregation of components. Mainly caused by uneven mixing when casting alloy.
Vertical semi-continuous casting
Vertical semi-continuous casting is mainly used for the production of aluminum wire ingots, slab ingots and various deformed alloys for processing profiles. The molten aluminum is poured into the mixing furnace after batching. Due to the special requirements of the wires, the intermediate plate Al-B must be added to remove the titanium and vanadium (wire ingots) from the molten aluminum before casting; the slabs must be added with Al-Ti--B alloy (Ti5%B1%) for refinement treatment. Make the surface organization fine. Add 2# refining agent to high-magnesium alloy, the amount is 5%, stir evenly, after standing for 30 minutes, remove the scum, then cast. Lift the chassis of the casting machine before casting, and blow off the moisture on the chassis with compressed air. Then raise the base plate into the crystallizer, apply a layer of lubricating oil to the inner wall of the crystallizer, put some cooling water into the water jacket, put the dry and preheated distribution plate, automatic regulating plug and launder in place, so that the distribution plate Each port is located in the center of the crystallizer. At the beginning of casting, press the automatic adjustment plug with your hand to block the nozzle, cut open the furnace eye of the mixing furnace, and let the aluminum liquid flow into the distribution plate through the launder. When the aluminum liquid reaches 2/5 in the distribution plate, release the automatic Adjust the plug so that the molten aluminum flows into the crystallizer, and the molten aluminum is cooled on the chassis. When the aluminum liquid reaches 30mm high in the crystallizer, the chassis can be lowered, and cooling water will start to be sent. The automatic adjusting plug controls the balanced flow of the aluminum liquid into the crystallizer and keeps the height of the aluminum liquid in the crystallizer unchanged. The scum and oxide film on the surface of the molten aluminum should be removed in time. When the length of the aluminum ingot is about 6m, block the furnace eye, remove the distribution plate, stop the water supply after the aluminum liquid is completely solidified, remove the water jacket, take out the cast aluminum ingot with a monorail crane, and place it on the sawing machine according to the required size Saw it off and prepare for the next casting. During casting, the temperature of the molten aluminum in the mixing furnace is maintained at 690-7l0°C, the temperature of the molten aluminum in the distribution plate is maintained at 685-690°C, the casting speed is 190-21Omm/min, and the cooling water pressure is 0.147-0.196MPa.
The casting speed is proportional to the linear ingot with a square section:
VD=K where V is the casting speed, mm/min or m/h; D is the side length of the ingot section, mm or m; K is the constant value, m2/h, generally 1.2～1.5.
Vertical semi-continuous casting is a sequential crystallization method. After the molten aluminum enters the casting hole, it begins to crystallize on the bottom plate and the inner wall of the mold. Because the cooling conditions of the center and the sides are different, the crystallization forms a form of low middle and high periphery. The chassis descends at a constant speed. At the same time, the upper part is continuously injected with liquid aluminum, so that there is a semi-solidified zone between the solid aluminum and the liquid aluminum. Because the aluminum liquid shrinks when it is condensing, and there is a layer of lubricating oil on the inner wall of the crystallizer, as the chassis descends, the solidified aluminum exits the crystallizer. There is a circle of cooling water holes in the lower part of the crystallizer, and the cooling water can be sprayed until it has escaped. The surface of the aluminum ingot is subjected to secondary cooling until the entire wire ingot is cast.
Sequential crystallization can establish relatively satisfactory solidification conditions, which is beneficial to the grain size, mechanical properties and electrical conductivity of the crystallization. There is no difference in mechanical properties in the height direction of the comparative ingot, the segregation is also small, the cooling rate is faster, and a very fine crystal structure can be obtained.
The surface of the aluminum wire ingot should be flat and smooth, free of slag, cracks, pores, etc., the length of surface cracks should not exceed 1.5mm, the depth of slag and ridge wrinkles on the surface should not exceed 2mm, and the section should not have cracks, pores and slag inclusions. There are no more than 5 slag inclusions less than 1mm.
The main defects of aluminum wire ingots are:
① Cracks. The reason is that the temperature of the molten aluminum is too high, the speed is too fast, and the residual stress is increased; the silicon content in the molten aluminum is greater than 0.8%, and the same melt of aluminum and silicon is formed, and then a certain amount of free silicon is generated, which increases the thermal cracking property of the metal: Or the amount of cooling water is insufficient. When the surface of the mold is rough or no lubricant is used, the surface and corners of the ingot will also crack.
② Slag inclusion. The slag inclusion on the surface of the aluminum wire ingot is caused by the fluctuation of the molten aluminum, the rupture of the oxide film on the surface of the molten aluminum, and the scum on the surface entering the side of the ingot. Sometimes lubricating oil can also bring in some slag. Internal slag inclusion is caused by the low temperature of the molten aluminum, the high viscosity, the inability of the slag to float in time or the frequent changes of the molten aluminum level during casting.
③Cold compartment. The formation of the cold barrier is mainly caused by excessive fluctuations in the level of molten aluminum in the mold, low casting temperature, excessively slow casting speed, or the vibration and uneven drop of the casting machine.
④ Stoma. The pores mentioned here refer to small pores with a diameter of less than 1 mm. The reason for this is that the casting temperature is too high and the condensation is too fast, so that the gas contained in the aluminum liquid cannot escape in time, and after solidification, small bubbles are gathered to form pores in the ingot.
⑤The surface is rough. Because the inner wall of the crystallizer is not smooth, the lubrication effect is not good, and aluminum tumors on the crystal surface are formed in severe cases. Or because the ratio of iron to silicon is too large, the segregation phenomenon caused by uneven cooling.
⑥Leakage of aluminum and re-analysis. The main reason is the operation problem, and the serious one can also cause nodules.
Application of Cast Aluminum Silicon (Al-Si) Alloy
Aluminum-silicon (Al-Si) alloy, the mass fraction of Si is generally 4%~22%. Because Al-Si alloy has excellent casting properties, such as good fluidity, good air tightness, small shrinkage and low heat tendency, After modification and heat treatment, it has good mechanical properties, physical properties, corrosion resistance and medium machining properties. It is the most versatile and most versatile type of cast aluminum alloy. Here are some examples of the most commonly used ones:
(1) ZL101(A) alloy ZL101 alloy has good air tightness, fluidity and thermal crack resistance, moderate mechanical properties, welding performance and corrosion resistance, simple composition, easy casting, and suitable for various castings method. ZL101 alloy has been used for complex parts that bear moderate loads, such as aircraft parts, instruments, instrument housings, engine parts, automobile and ship parts, cylinder blocks, pump bodies, brake drums, and electrical parts. In addition, based on the ZL101 alloy, the impurity content is strictly controlled, and the ZL101A alloy with higher mechanical properties is obtained by improving the casting technology. It has been used to cast various shell parts, aircraft pump bodies, automobile gearboxes, and fuel oil. Box elbows, aircraft accessories and other load-bearing parts.
(2) ZL102 alloy ZL102 alloy has the best thermal crack resistance and good air tightness, as well as good fluidity, cannot be strengthened by heat treatment, and has low tensile strength. It is suitable for casting large and thin-walled complex parts. Suitable for die casting. This type of alloy is mainly used to withstand low-load thin-walled castings with complex shapes, such as various instrument housings, automobile casings, dental equipment, pistons, etc.
(3) ZL104 alloy ZL104 alloy has good air tightness, fluidity and thermal crack resistance, high strength, corrosion resistance, welding performance and cutting performance, but low heat resistance strength, easy to produce small pores, casting The process is more complicated. Therefore, it is mainly used to manufacture large-size sand metal castings that withstand high loads, such as transmission casings, cylinder blocks, cylinder head valves, belt wheels, cover plate toolboxes and other aircraft, ships and automobile parts.
(4) ZL105 alloy ZL105 alloy has high mechanical properties, satisfactory casting performance and welding performance, better cutting performance and heat resistance strength than ZL104 alloy, but low plasticity and low corrosion stability. It is suitable for various casting methods. This type of alloy is mainly used to produce aircraft, engine sand molds and metal mold casting parts that bear heavy loads, such as transmission casings, cylinder blocks, hydraulic pump housings and instrument parts, as well as bearing supports and other machine parts.
Application of Cast Aluminum Zinc (Al-Zn) Alloy
For Al-Zn alloys, due to the high solubility of Zn in Al, when Zn with a mass fraction of more than 10% is added to Al, the strength of the alloy can be significantly improved. Although this type of alloy has a high natural aging tendency and high strength can be obtained without heat treatment, the disadvantages of this type of alloy are poor corrosion resistance, high density, and hot cracking easily during casting. Therefore, this type of alloy is mainly used to manufacture die-cast instrument housing parts.
The characteristics and applications of common cast Al-Zn alloys are as follows:
(1) ZL401 alloy ZL401 alloy has medium casting performance, small shrinkage cavity and hot cracking tendency, good welding performance and cutting performance, high strength in the as-cast state, but low plasticity, high density, and poor corrosion resistance. ZL401 alloy is mainly used for various pressure casting parts, the working temperature does not exceed 200 degrees Celsius, and the structure and shape of the automobile and aircraft parts are complex.
(2) ZL402 alloy ZL402 alloy has medium casting performance, good fluidity, moderate air-tightness, thermal crack resistance, good cutting performance, high mechanical properties and impact toughness in the as-cast state, but high density, smelting The process is complex, and it is mainly used for agricultural equipment, machine tools, ship castings, radio devices, oxygen regulators, rotating wheels, and air compressor pistons.
Application of Cast Aluminum Magnesium (Al-Mg) Alloy
The mass fraction of Mg in the Al-Mg alloy is 4%~11%. The alloy has a low density, high mechanical properties, excellent corrosion resistance, good cutting performance, and a bright and beautiful surface. However, due to the complicated smelting and casting processes of this type of alloy, in addition to being used as a corrosion-resistant alloy, it is also used as an alloy for decoration. The characteristics and applications of common cast Al-Mg alloys are as follows.
(1) ZL301 alloy ZL301 alloy has high strength, good elongation, excellent cutting performance, good weldability, can be anodized, and vibrated. The disadvantage is that it has a tendency to microscopically loose and is difficult to cast. ZL301 alloy It is used to manufacture parts with high corrosion resistance under high load, working temperature below 150 degrees Celsius, and working in the atmosphere and sea water, such as frames, supports, rods and accessories.
(2) ZL303 alloy ZL303 alloy has good corrosion resistance, good weldability, good cutting performance, easy polishing, acceptable casting performance, low mechanical properties, cannot be strengthened by heat treatment, and has a tendency to form shrinkage holes. It is widely used Die casting. This type of alloy is mainly used for medium load parts under the action of corrosion or parts in cold atmosphere and operating temperature not exceeding 200 degrees Celsius, such as marine ship parts and machine shells.
(3) ZL305 alloy ZL305 alloy is mainly added with Zn on the basis of Al-Mg alloy to control natural aging, improve strength and stress corrosion resistance, have good comprehensive mechanical properties, and reduce the oxidation, porosity and pore defects of the alloy. This type of alloy is mainly used for high-load, working temperature below 100 degrees Celsius, and high corrosive parts that work in the atmosphere or sea water, such as parts in marine ships.
Introduction to aluminum ingot knowledge
Aluminum ingot for remelting-15kg, 20kg (≤99.80%Al):
T-shaped aluminum ingot--500kg, 1000kg (≤99.80%Al):
High-purity aluminum ingots-10kg, 15kg (99.90%～99.999% Al);
Aluminum alloy ingot - 10kg, 15kg (Al--Si, Al--Cu, Al--Mg);
Plate ingot--500～1000kg (for plate making);
Round spindles-30～60kg (for wire drawing).
More details Link: https://www.wanmetal.com/
Reference source: Internet
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Post time: Aug-27-2021