Tesla filed a patent application, which describes a more efficient new cooling process that can be used to produce high-strength aluminum components used on its production line.
The patent is titled: "System and Method for Facilitating Pulsed Spray Quench of Extruded Objects" and describes a design aimed at improving the strength, rigidity and energy absorption of aluminum alloy components The quenching process will use a multi-channel nozzle system to spray-cool the extruded aluminum parts.
Today's vehicles use 6XXX aluminum alloy to make the front and rear bumpers of the car, the steps on the side and back of the vehicle, and the knee pads. Tesla also stated in the patent document that its car uses 6XXX aluminum alloy. After such parts are extruded, they will enter the quenching process, which is a simple process of cooling the heated metal.
At present, the quenching process used by Tesla is to soak the latest extruded aluminum alloy in water to achieve cooling purposes. This quenching process is called "rapid cooling". Although there are cooling methods such as air cooling and furnace cooling, for car manufacturing, immersing parts in water is the most time-saving method.
However, Tesla's patent admits that this method of rapidly cooling aluminum alloy components will adversely affect the integrity of the metal structure. Rapid cooling not only causes metal parts to deform and bend, but also causes chemical changes.
Magnesium silicide (Mg2Si) exists in aluminum alloy parts, and rapid cooling of aluminum alloy parts will inhibit the solidification of such compounds in metals. If Mg2Si is not properly processed when rapidly cooling aluminum alloy parts in water, the metal will require higher extrusion pressure and be more sensitive to heat. The combination of these two characteristics will effectively reduce the mechanical properties of the final product, resulting in a car The frame loses strength during the production process.
Therefore, Tesla plans to use a multi-pass spray system to cool extruded aluminum parts, avoiding the soaking process used by many aluminum alloy manufacturers. In the patent document, the company introduced a quenching system that can spray newly squeezed metal at different speeds according to the size of the part, and spray half a gallon to 10 gallons of water per minute to cool the metal.
In addition, two pyrometers are placed at the near and far end of the quenching chamber, which is responsible for keeping the metal at a certain temperature during the quenching process. This type of pyrometer can communicate with the system to ensure that it has a suitable cooling temperature, and that the aluminum parts will not cool down too quickly, so that Mg2Si can be properly processed. In addition, factors such as temperature control, injection frequency, liquid pressure, gas pressure, and water flow are also monitored to maximize the strength of the aluminum parts after quenching.
Tesla`s recognition of the shortcomings of rapid cooling of extruded metal parts also shows that the company realizes that the strength of car frames can be improved by more efficient cooling technology.