Tesla has submitted a patent that describes a new, more effective cooling process for manufacturing high-strength aluminum components to be used in its product line.
The patent entitled, “System and Method for Facilitating Pulsed Spray Quench of Extruded Objects”, describes a quenching process that aims to increase the strength, rigidity, and energy absorption of aluminum alloy components. A multi-way spray nozzle system would cool extruded aluminum with an atomized spray of liquid.
“A system includes a billet die at a proximal end configured to accept a billet and form an extrudate, a quench chamber located adjacent to the billet die for receiving the extrudate and comprising at least one pulsed width modulation (PWM) atomizing spray nozzle and a control module in communication with the at least one PWM atomizing spray nozzle and configured to independently control a liquid pressure, a gas pressure, a spray frequency, a duty cycle and flow rate of each at least one PWM atomizing spray nozzle,” reads the patent abstract.
Vehicles today use 6XXX aluminum alloys, which make up the front and rear bumpers, side and back steps, and knee bolsters of a car, the Kobelco Technology Review stated. Tesla also indicates within the patent that it uses 6XXX alloys for its vehicles. After these parts are extruded, they enter a quenching process, which is simply the process of cooling the metal after it has been heated.
Currently, Tesla utilizes a quenching process that involves cooling recently extruded aluminum alloys by soaking the parts in water. This process of quenching is recognized as “quick cooling.” While other cooling means are available, such as air cooling and furnace cooling, soaking the parts in water is the most time-effective method for automotive manufacturing.
However, Tesla’s patent recognizes the adverse effects that quick cooling aluminum alloy parts can have on the structural integrity of the metal. Quick-cooling can not only lead to deformation and warping of metal parts, but things can change chemically as well.
Magnesium silicide, or Mg2Si, is present in these aluminum alloy parts, and quick cooling them can inhibit the compound’s ability to set in the metal. Without the proper setting of Mg2Si by quick-cooling the aluminum alloy in water, the metal requires a higher extrusion pressure and becomes more sensitive to heat, according to Light Metals 2014. The combination of these two properties can effectively compromise the mechanical properties of the final product, making the frame of the vehicle lose strength through the manufacturing process.
Tesla plans to utilize a multi-way spraying system to cool extruded aluminum parts, eliminating the soaking process that is used by so many manufacturers of aluminum alloy. In the patent, the company describes a quenching system that would spray newly extruded metals at varying rates depending on the size of the part. Between one half-gallon and 10 gallons of water per minute would cool the metal in question.
Two pyrometers would be placed at both the proximal and distal ends of the quench chamber. These would hold the responsibility of maintaining the metal’s temperature through the quenching process. The pyrometers would communicate with the system to ensure proper cooling temperatures, making sure the aluminum does not cool too quickly, allowing the Mg2Si to set. In conjunction with the temperature control, spray frequency, liquid pressure, gas pressure, and flow rate will also be monitored to ensure maximum strength after extradition is complete.
Tesla’s recognition of the flaws in quick-cooling extruded metals indicates the company’s realization that increased strength of a car’s frame could improve with a more efficient cooling technique.
In the teardown of the Model Y, Sandy Munro complimented Tesla’s use of what he called the “aluminum rear crush plate.” The piece is located at the trunk hatch and is designed to fold in the event of a rear-impact. The part saves the sides of the body from being compromised in a crash, which can ultimately total the vehicle if the chassis bends excessively.
While the crush plate is durable and prevents excessive damage to the body of the Model Y, the quick-cooling process used during manufacturing could ultimately make the crush plate less sustainable than what it could be. Not to mention, the front bumper, rear bumper, side and back steps, and knee bolsters are also made of aluminum. Using a different cooling technique could eventually lead to an even safer Tesla vehicle, which already has many five-star crash safety ratings from several organizations located around the world.
Read Tesla’s patent for a new aluminum cooling process below.
Tesla SYSTEM AND METHOD FOR FACILITATING PULSED SPRAY QUENCH OF EXTRUDED OBJECTS by Joey Klender on Scribd