Production process and classification of aluminum ingots

Production process and classification of aluminum ingots

What is the production process of aluminum ingots?

The production of aluminum ingots is composed of bauxite mining, alumina production, aluminum electrolysis and other production links.

The bauxite is mined first, and the aluminum ore powder is produced through processes such as washing and grinding, and then alumina is obtained through four complicated processes such as roasting.

There are three main types of bauxite for the production of alumina: gibbsite, diaspore, and boehmite.

Among the proven global reserves of bauxite, 92% are weathered laterite-type bauxite, which belongs to the gibbsite type. These bauxites are characterized by low silicon, high iron, and high aluminum-silicon ratio, and are concentrated in Africa. Western, Oceania and Central and South America. The remaining 8% is sedimentary bauxite, which belongs to boehmite and diaspore type, with medium and low grades, mainly distributed in Greece, the former Yugoslavia and Hungary.

Due to the different characteristics of the three kinds of bauxite, each alumina production enterprise adopts different production processes in production, mainly including Bayer method, soda lime sintering method and Bayer-sintering combined method.

Usually, high-grade bauxite is produced by Bayer method, and medium and low-grade bauxite is produced by combined method or sintering method. Due to its simple process and low energy consumption, the Bayer method has become the most important method used in the current alumina production, and its output accounts for about 95% of the world's total alumina production.

Under the action of strong current, aluminum oxide is electrolyzed to produce aluminum metal. This process is called electrolytic aluminum;

How many types of aluminum ingots are there?

Aluminum ingots can be divided into three types: aluminum ingots for remelting, high-purity aluminum ingots, and aluminum alloy ingots according to their composition;

Several common aluminum ingots:

Aluminum ingot for remelting--15kg, 20kg(≤99.80%Al):

T-shaped aluminum ingot--500kg, 1000kg(≤99.80%Al):

High-purity aluminum ingot--l0kg, 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 ingot - 30~60kg (for wire drawing).

What are the common defects of aluminum for remelting?

① stomata. The main reason is that the casting temperature is too high, the aluminum liquid contains more gas, the surface of the aluminum ingot has many pores (pinholes), the surface is dark, and thermal cracks occur in severe cases.

② Slag inclusion. The main reason is that one is that the slag is not clean, resulting in slag inclusion on the surface; the other is that the temperature of the molten aluminum is too low, resulting in internal slag inclusion.

③ Ripple 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 the low casting temperature, which makes the crystallization of aluminum ingots not dense, resulting in looseness and even cracks. Hot cracks are caused by high casting temperature.

⑤ composition segregation. It is mainly caused by uneven stirring when casting alloys.

Shangang has been committed to researching and improving the quality of steel. The aluminum produced for remelting has fewer pores, basically no slag inclusions and cracks, and the composition is uniform. We are proud to strive to provide customers with high-quality aluminum ingot products.

The process flow of casting aluminum ingots is roughly as follows:

(1) Aluminum tapping—slag removal—weight inspection—ingredients—furnace loading—scouring—casting—aluminum ingots for remelting—finished product inspection—finished product inspection—storage

(2) Aluminum tapping - slag removal - weighing - batching - furnace loading - refining - casting - alloy ingots - casting alloy ingots - finished product inspection - finished product weighing - storage

Commonly used casting methods are divided into continuous casting and vertical semi-continuous casting

Introduction to the continuous casting method of cast aluminum ingots:

Continuous casting can be divided into two ways: mixed furnace casting and external casting. Both use continuous casting machines.

Mixing furnace casting is to pour aluminum liquid into the mixing furnace, and then pour it from the mixing furnace. It is mainly used to produce aluminum ingots and casting alloys for remelting.

For casting in a mixing furnace, it must first go through batching, then pour it into the mixing furnace, stir evenly, and then add flux for refining. Casting alloy ingots must be clarified for more than 30 minutes, and the slag can be cast after clarification. When 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. Furnace eye and casting machine are connected by launder, and the launder should be shorter, which can reduce the oxidation of aluminum 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 slag removal. After one mold is filled, the launder is moved to the next mold, and the casting machine moves forward continuously. The casting mold advances one by one, and the molten aluminum gradually cools down. When it reaches the middle of the casting machine, the molten aluminum has solidified into aluminum ingots, and then the smelting number is stamped 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 casting mold is turned over, and the aluminum ingot is released from the mold and falls on the automatic ingot receiving trolley. It is automatically stacked and bundled by the stacker to become a finished aluminum ingot. ingot. The casting machine is cooled by spraying water, but the water can only be supplied after the casting machine has turned a full circle. Each ton of molten aluminum consumes about 8-10t of water, and a blower is required for surface cooling in summer. The ingot belongs to flat die casting, and the solidification direction of the molten aluminum is from bottom to top, and the upper middle is finally solidified, leaving a groove-shaped depression. The solidification time and conditions of each part of the aluminum ingot are different, so its chemical composition will also be different, but it meets the standard as a whole.

External casting is to cast directly from the ladle to the casting machine. It is mainly used when the casting equipment cannot meet the production requirements, or the quality of the incoming material is too poor to be directly put into the furnace. Since there is no external heating source, the ladle is required to have a certain temperature, generally 690-740°C in summer and 700-760°C in winter, to ensure a better appearance of the aluminum ingot.

Introduction of vertical semi-continuous casting method for casting aluminum ingots:

Vertical semi-continuous casting is mainly used for the production of aluminum wire ingots, plate 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 wire, it is necessary to add Al-B in the middle plate before casting to remove titanium and vanadium (wire ingot) from the molten aluminum; the plate ingot needs to be added with Al-Ti--B alloy (Ti5% B1%) for refinement. Make the surface structure finer.