The direction of extrusion is from left to right. This is a simple description of the most widely used direct extrusion. Indirect extrusion is a similar process, but there are also some very important differences. In the direct extrusion process, the mold is not moving. The pressure of the extruded rod pushes the aluminum alloy through the die hole. In the indirect extrusion process. The mold is mounted on a hollow extruded rod to squeeze the mold against the stationary aluminum rod blank, forcing the aluminum alloy to be extruded through the mold to the hollow extruded rod.
In fact, the extrusion process is similar to the extrusion of toothpaste. When pressure acts on the closed end of the toothpaste, the cylindrical toothpaste is squeezed out from the circular opening. If the opening is flat, the squeezed toothpaste is a ribbon. Of course, complex shapes can also be extruded at openings of the same shape. For example, a cake maker uses a specially shaped tube to squeeze ice cream to make a variety of decorative laces. What they do is actually extrusion. Although you can't make a lot of useful products with toothpaste or ice cream, you can't use your fingers to squeeze aluminum into aluminum tubes. But you can rely on high-power hydraulic presses to squeeze aluminum alloys out of a mold hole of a certain shape to produce a wide variety of useful and almost any shape.
The aluminum rod is the blank of the extrusion process, and the aluminum rod for extrusion can be solid or hollow, usually a cylinder, and the length is determined by the extrusion cylinder. Aluminum rods are usually formed by casting, and some are forged or powder forged. It is usually sawn from an aluminum alloy bar with a fine alloy composition. Aluminum alloys usually consist of more than one metal element. The extruded aluminum alloy consists of trace amounts (usually no more than 5%) of elements such as copper, magnesium, silicon, manganese or zinc. These alloying elements improve the performance of pure aluminum. And affected the extrusion process. The lengths of the aluminum rods of the various manufacturers are inconsistent, which is determined by the final required length of the aluminum profile, the extrusion ratio, the length of the discharge, and the amount of extrusion. Standard lengths typically range from 26" (660mm) to 72" (1830mm). Outer diameter ranges from 3" (76mm) to 33" (838mm) 6" (155mm) to 9" (228mm) direct extrusion processes
When the shape of the final product is determined, the appropriate aluminum alloy is selected, and the extrusion mold manufacturing has been completed, the preparation for the actual extrusion process is completed. The aluminum rod and the extrusion tool are then preheated, and the aluminum rod is inherently solid during the extrusion process but has become soft in the furnace. The melting point of the aluminum alloy is about 660 °C. Typical heating temperatures for extrusion processes are typically greater than 375 ° C and can be as high as 500 ° C depending on the extrusion of the metal.
The actual extrusion process begins when the extrusion bar begins to apply pressure to the aluminum rods in the ingot. Different hydraulic presses are designed to compress from 100 tons to 15,000 tons, almost any pressure. This squeezing force determines the size of the extrusion product that the extruder can produce. The extrusion product specification is expressed by the largest cross-sectional dimension of the product, and sometimes also the circumscribed circle diameter of the product.
When the extrusion has just begun, the aluminum rod is shortened and thickened by the reaction force of the mold until the expansion of the aluminum rod is restricted by the wall of the ingot cylinder. Then, as the pressure continues to increase, there is no place for the soft (still solid) metal. The flow can begin to be squeezed from the forming hole of the mold to the other end of the mold, which forms a profile.
About 10% of the aluminum rods (including the aluminum rod skin) are left in the barrel, the extruded product is cut from the mold, and the remaining metal in the barrel is also cleaned and recycled. When the product leaves the mold, the latter process is that the hot extruded product is quenched, mechanically treated and aged. When the heated aluminum is extruded from the mold through the ingot, the metal in the center of the aluminum rod flows faster than the edge. As indicated by the black strips in the illustration, the metal at the edges is left behind and recycled as a residue.
The extrusion speed depends on the shape of the extruded alloy and the die orifice, which is squeezed with hard alloys to squeeze the complex shape material, which may be as slow as 1-2 feet per minute. Extruding a simple shape material with a soft alloy can reach 180 feet per minute or even faster.
The length of the extruded product depends on the aluminum rod and the mold discharge hole, and an uninterrupted extrusion can extrude a product up to 200 feet. The latest forming extrusion, when the extruded product leaves the extruder, is placed on the sliding table (equivalent to the conveyor belt), depending on the alloy, the extruded product is cooled by: natural cooling, air or Water cooled and quenched. This is a critical step in ensuring metallographic performance after product aging. The extruded product is then transferred to a cold bed.
After the straight extrusion product is quenched (cooled), the straightening and correcting twisting is performed by a stretching machine or a straightening machine (stretching is also classified as cold working after extrusion). Finally, the product is transported by the conveyor to the sawing machine. Saw cutting A typical finished sawing is to cut a product into a specific commercial length. Circular saws are the most widely used today, as long as the spiral saw saws the long material that is extruded vertically. There are also saws cut from the top of the profile (such as electric miter saws). Also useful is the saw table, which is sawed with a circular saw blade from the bottom up, and then the saw blade is returned to the bottom of the table for the next cycle.
A typical finished circular saw, typically 16-20 inches in diameter, with more than 100 carbide teeth. Large size saw blades are used for large diameter extruders.
The self-lubricating sawing machine is equipped with a system for delivering lubricant to the serrations to ensure optimum sawing efficiency and kerf surface.
The automatic device press device fixes the profile for sawing, and the sawing debris is collected for recycling. Aging: Some extruded products need to pass the aging to achieve the best strength, so it is also called age hardening. Natural aging is carried out at room temperature. Artificial aging is carried out in an aging furnace. Academically speaking, it is called precipitation strengthening heat treatment.
When the profile is extruded from the extruder, the profile is in a semi-solid state. But soon it quickly becomes solid when it is cooled or quenched (whether air or water cooled). Non-heat treated reinforced aluminum alloys (such as aluminum alloys added with magnesium or manganese) are obtained by natural aging and cold working. Heat treatable reinforced aluminum alloys (such as aluminum alloys with copper, zinc, magnesium + silicon) can obtain better strength and hardness by affecting the heat treatment of the metallographic structure of the alloy.