Aluminium extrusion process is a process in which extruded products are obtained. Extruded aluminium products have many applications in various industries such as automotive, aircraft, train, building, exterior, interior design, aerospace, etc.
Direct and indirect extrusion
There are two types of aluminium extrusion processes, direct and indirect. Direct extrusion is a process in which the end of a mold is held in place by a moving metal ram. Indirect extrusion is a process in which the ingot remains stationary while the mold assembly is at the end of the ram, moving in front of the ingot, creating the necessary pressure for metal to flow through the ingot.
The shape is a determining factor in the cost and ease of the piece that can be extruded. Extrusion can be used to extrude a variety of shapes, but there are limiting factors to consider. These include size, shape, alloy, extrusion ratio, tab ratio, tolerance, polishing, invoice and waste ratio. If a piece is beyond the range of these factors, it can not be extruded successfully.
Size, shape, alloy, extrusion ratio, tab ratio, tolerance, end, and waste ratio are related in the extrusion process, as are extrusion rate, billet temperature, extrusion pressure, and extruded alloy.
It is necessary to get acquainted with the aluminium extrusion process to making aluminium extruded products.
The first step in aluminium extrusion is that the billets must be heated to about 800-925 degrees Fahrenheit.
After a billet reaches the desired temperature, it is transferred to the loader, where a thin layer of stain or lubricant is added to the billet. The stain acts as a separating agent (lubricant) that prevents the two parts from sticking together.
The billet is transferred to the mold.
Under pressure, the billet becomes shorter and wider in front of the mold until it makes full contact with the walls of the container. As aluminium is driven through the mold, liquid nitrogen flows around some parts of the mold to cool it. This increases the life of the mold and creates an inert atmosphere that prevents the formation of oxides on the extruded shape. In some cases, nitrogen gas is used instead of liquid nitrogen. Nitrogen gas does not cool the mold but creates an inert atmosphere.
As a result of the pressure added to the billet, the soft but solid metal begins to compress through the opening of the mold.
When an extrusion comes out of the press, the temperature is measured with the actual T3 temperature technology tool mounted on the press plate. T3 records the extrusion temperature of aluminium extrusion. The main purpose of knowing the temperature is to maintain the maximum press speed. The target output temperature for an extrusion depends on the alloy. For example, the target output temperature for alloys is 6063, 6463, 6063A and 6101 930 degrees Fahrenheit (minimum). The target output temperature for 6005A and 6061 950 alloys is F (minimum).
When the profile (extruded product) reaches the desired length, the profile (extruded product) is cut.
At this stage of the aluminium extrusion process, the extruded product is cooled. After the aluminium has cooled and moved along the cooling table, then “hardening” is performed.
The next step is sawing. After the extrusions are pulled, they are transferred to the saw table and cut to specific lengths. Cutting tolerance in saws is 1/8 inch or more depending on the length of the saw.
After cutting the parts, they are loaded on a transport machine and transferred to old furnaces. Heat treatment or artificial aging of the metal by accelerating the aging process in a controlled temperature environment for a certain period of time.
In general, the extrusion speed differs directly from the temperature and pressure of the metal developed in the container. Temperature and pressure are limited by the alloy used and the extruded shape. For example, lower extrusion temperatures usually produce problems with better quality surfaces and more accurate dimensions. Lower temperatures require higher pressures. Sometimes, due to pressure constraints, it reaches a point where a shape cannot be extruded through a given press.
The preferred billet temperature is the temperature that provides acceptable surface conditions and tolerances while providing the shortest cycle time possible. The ideal billet extrusion is at the lowest temperature the process allows. An exception to this is alloys called quench presses, most of which are in the 6000 series. With these alloys, the temperature of the dissolved heat treatment in the range of 930-980 ° F must be obtained at the mold outlet to achieve optimal mechanical properties.
At excessive billet temperature and extrusion speed, the metal flow becomes more fluid. This metal, which seeks the path with the least resistance, tends to fill larger voids on the surface of the mold and resists the entry of compact areas. Under these conditions, the dimensions of the shape are usually less than the allowable tolerances, especially the dimensions of the ridges or thin ribs.
all steps in aluminium extrusion process cause extruded profile in different usages.