कंपनी की खबर Popular science article: What materials are used for SpaceX's Starship? What welding methods are employed?

The evolutionary path of SpaceX Starship welding technology. Initially, SpaceX planned to build the Starship using lightweight carbon fiber, but because it was not heat-resistant, it ultimately chose the economical and durable stainless steel. However, the welding process of stainless steel was challenging, and SpaceX managed to achieve the perfect weld of the Starship through continuous attempts and improvements, including techniques such as TIG welding, laser welding, robotic welding, and friction stir welding. The application of these techniques not only enhanced the precision and strength of the welding, but also improved the appearance of the Starship. The successful welding of the Starship laid a solid foundation for future launches.

Starship's main material composition

If it weren't for the numerous suborbital test flights and recoveries of SpaceX's Starship, probably no one would have thought Musk would choose stainless steel.

If someone had said in a domestic professional setting or on the Internet before Starship took off that stainless steel could really fly into the sky, they might have been criticized by netizens to the point of questioning life.

Musk, however, has used a large amount of stainless steel materials on the Starship rocket, particularly 300 series stainless steel and self-developed 30X stainless steel, which not only reduced the manufacturing cost of the rocket but also enhanced its performance and durability.

The main material of Starship is stainless steel, especially SpaceX's self-developed 30X stainless steel.  

30X stainless steel has many advantages: low cost, about $4 per kilogram; Good low-temperature performance, with a significant increase in strength at low temperatures, suitable for storing liquid oxygen and methane fuels; The process is relatively simple, and the desired structure can be formed by rolling in a low-temperature environment; Strong heat resistance, maintaining sufficient strength at temperatures of 800 to 1000 degrees Celsius without the need for thick insulation layers; The structural strength is sufficient, and the arrow design only requires a layer of stainless steel material, reducing weight and simplifying the structure.

In addition to stainless steel, Starship also uses materials such as carbon fiber and aluminum-lithium alloy in some key parts. In addition, the Starship's heat shield is made up of about 18,000 hexagonal black tiles to provide protection when the aircraft enters the atmosphere.

Starship mainly uses the following welding process:

TIG welding and laser welding

Both TIG welding and laser welding are used in SpaceX's welding. TIG welding, also known as tungsten inert gas welding, can be used to weld a variety of metal materials such as stainless steel. It can provide high-quality weld seams, stable welding process, beautiful weld appearance, high welding strength, and is suitable for welding critical parts of Starship. Laser welding, on the other hand, has the advantages of high energy density, fast welding speed, small heat-affected zone, and large depth-to-width ratio of weld seams. It can achieve high-precision and high-quality welding, and is suitable for thin-walled structural components of Starship and parts with high requirements for welding deformation control.

Arc welding

Arc welding was used in the early water tower versions of Starship. Arc welding is a common welding method that melts metal by the heat of the arc generated between the electrode and the workpiece. The equipment is simple, the cost is low, the operation is flexible, and it can be used for welding various metal materials and structural parts of different thicknesses, but the welding quality and precision may be slightly lower than TIG welding and laser welding, the welding deformation is large, and subsequent leveling treatment is required, etc.

Friction stir welding

It is reported that SpaceX is now using friction stir welding. Friction stir welding is a new type of welding process invented by the British Welding Institute in 1991. It uses the principle of friction. A high-speed rotating drill bit is inserted into the connection of two metal plates to be welded. The friction generated by the high-speed rotation of the drill bit causes the metal atoms in contact to move and diffuse rapidly within the metal, thus joining the two metal plates. This welding process has the advantages of no spatter, no fusion point, high weld quality and small welding deformation, and is suitable for large area plate welding and structural component connection of starship.

Youdaoplaceholder0 The main advantages of friction stir welding include ‌ : ‌

1.

Youdaoplaceholder0 High weld quality ‌ : The weld seam of friction stir welding is completed by extrusion in a plastic state and belongs to solid-phase welding. Therefore, it will not produce some defects related to metallurgical solidification, such as cracks, inclusions, pores, and burning loss of alloy elements, etc. The performance of the weld seam is close to that of the base material, and the mechanical properties are excellent.

2.

Youdaoplaceholder0 Low heat input ‌ : In friction stir welding, the heat input is relatively small compared to fusion welding, and there is no melting of the metal at the joint, making it a solid-state welding process. This helps maintain the metallurgical properties of the base material and can weld materials such as metal matrix composites and fast-setting materials that would have adverse reactions with fusion welding.

3.

Youdaoplaceholder0 energy-saving and environmentally friendly ‌ : Friction stir welding does not require the addition of wire and shielding gas, and does not produce smoke, spatter or harmful radiation during the welding process. It is a green and environmentally friendly welding method.

4.

Youdaoplaceholder0 Wide range of application ‌ : It can weld all grades of aluminium alloys, including 2-series and 7-series alloys that are difficult to weld with MIG welding. In addition, friction stir welding is suitable for dissimilar material welding and can weld materials sensitive to hot cracks.

5.

Youdaoplaceholder0 Easy to operate ‌ : friction stir welding is easy to mechanize and automate, with simple equipment, low energy consumption and low requirements for the working environment. The welding process does not require filler material or shielding gas, simplifying the welding procedure.

6.

Youdaoplaceholder0 Excellent joint performance ‌ : the mechanical properties of the welded joint, especially the fatigue resistance, are excellent. The weld metal generates plastic flow, and the joint does not produce structures such as columnar crystals. Grain refinement is beneficial for improving the mechanical properties of the joint.

7.

Youdaoplaceholder0 Easy to control ‌ : Friction stir welding is easy to achieve precise control of the welding process, as well as digital input, control and recording of welding specification parameters.

Automated welding technology

SpaceX widely uses welding robots for automated welding in Starship manufacturing. Automated welding technology uses advanced control systems and sensors to achieve precise control of the welding process, ensuring consistency in the shape, size and position of the weld seam, reducing human error in the welding process, improving the reliability and stability of the welding, while also enhancing production efficiency and ensuring the stability and consistency of the welding quality.

To ensure the quality of the weld, SpaceX conducts strict inspections and treatments on the weld. Early on, defects such as sharp edges and tiny cracks were removed by grinding the weld surface to reduce the risk of weld failure. At the same time, the process parameters and operation procedures were constantly optimized during the welding process to reduce the number of individual welds and potential failure points and improve the reliability of the overall structure.

In summary, SpaceX Starship welding is a combination of laser welding, friction stir welding, TIG welding, etc. A journey of a thousand miles begins with a single step. I hope more and more technology enterprises will innovate and develop, have big dreams, take every step steadily, constantly change and innovate, and walk the path of intelligent manufacturing.