Railway manufacturing using extrusion methods
What is Aluminum Extrusion?
Aluminum extrusion forces aluminum alloy material through a die with a specific cross-sectional profile. A powerful ram pushes the aluminum through the die and out the opening. Then it is pulled out along a run-out table in the same shape as the die. The aluminum is shaped through the opening in the die.
To simplify the process, think about a tube of toothpaste or some children’s play dough. When you squeeze the toothpaste out of the tube, it maintains its shape, the same thing with the play dough. When you put play dough through a press, it will keep that shape also. In this case, the toothpaste tube or press is the extrusion die. The most commonly extruded shapes are angles, channels, and round tubes. These shapes can be solid, hollow, or semi-hollow.
The aluminum extrusion process is simple, but there are several steps. Billets should be heated to around 800-925° F. After reaching the desired temperature, and they are moved to the loader. A thin film of lubricant is applied to the billet and the ram. The lubricant acts as a releasing agent between the two parts. This lubrication will prevent the parts from sticking together. The billet is repositioned to the cradle. The ram forcefully pushes the billet inside the container to the dummy block.
The billet is squeezed against the die. The billet shortens and widens until it makes contact with the walls of the container. At the same time, liquid nitrogen, or nitrogen gas, flows around some of the die to keep it cool. This extends the life of the die and creates a stagnant atmosphere, which prevents oxides from developing on the extruded shape. The nitrogen gas doesn’t cool the die itself but will make a stagnant environment.
The malleable metal gets pushed through the die opening due to the pressure applied to the billet. A puller positioned on the press plate measures the temperature of the extrusion as it exits the press. The temperature determines the speed at which the press can go. The alloy determines the target’s exit temperature. For example, alloys 6063, 6463, 6063A, and 6101 have a target exit temperature of 930° F. (minimum). The alloys 6005A and 6061 have a target exit temperature of 950° F. TensileMill CNC is your expert in material hardness testing!
Extrusions are pressed into the die and onto the lead-out table. This guides the alloy down the run-out table during the process. Then it’s cooled while being pulled by several fans that run the entirety of the run-out and cooling table. The billet cannot be used in its entirety. Oxides from the billet skin are present in the remainder. The end is cut off and discarded, and the process continues with another billet loaded and welded to a previously loaded billet. When the extrusion has reached the desired length, it is sheared off. The metal is transferred to the cooling table from the run-out table.
Extrusions are straightened and ‘work hardened’ when stretched. Then the extrusions are stretched before being moved to the saw table and cut to the lengths needed. Saws have a cutting tolerance of at least 1/8 inch or more, depending on the length of the saw. Once the cuts have been made, they are loaded onto a transport device and transported to age ovens. This process of artificial aging, known as “heat-treating,” hardens metal by hastening the aging process in a contained temperature environment during a specific period.
The billets rack, hot shearing machine, and furnace body are part of the heating system, which is the main machine. The power of the unit is the extrusion press. The mold heating furnace heats the molds. And the puller machine pulls, saws, and lengthens. Without this, it would be much more difficult for the worker to obtain the correct size. The cooling beds not only cool but also feed and straighten the material. The aging furnace hardens, polishes, and shines when everything is done.
There are different extrusion methods. The most common for aluminum is direct or forward. There are also indirect, tube, hydraulic, and impact methods. With the direct method, the aluminum extruder is placed in a heated walled container with the billet. The metal is then forced into the die via the moving ram.
Many fields use the method, such as sporting goods, toys, exercise/fitness equipment, boats, electrical equipment, medical/dental equipment, and solar, wind, and geothermal equipment, just to name a few. But they are quickly finding this extremely valuable in railway manufacturing. Aluminum extrusion in railway manufacturing is the preferred extrusion process because lightweight aluminum components are critical in providing increased speed, safety, and comfort for the train design. Trains require lighter materials that are corrosion-resistant and capable of achieving a tight seal. Aluminum is an excellent material for train bodies due to its high strength-to-weight ratio and elasticity.
Many fields use the method, such as sporting goods, toys, exercise/fitness equipment, boats, electrical equipment, medical/dental equipment, and solar, wind, and geothermal equipment, just to name a few. But they are quickly finding this extremely valuable in railway manufacturing. Railway manufacturing uses the process because lightweight aluminum components are critical in providing increased speed, safety, and comfort for the train design. Trains require lighter materials that are corrosion-resistant and capable of achieving a tight seal. Aluminum is an excellent material for train bodies due to its high strength-to-weight ratio and elasticity.
Aluminum is not the only possible material. Metals such as brass, copper, lead, magnesium, zinc, steel, and titanium can all be used. Plastic and ceramics, such as terra cotta, can also be used.
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