The Large Hadron Collider (LHC), the world's largest particle accelerator, uses more than 250,000 high-strength, special 316L stainless steel fasteners. These molybdenum-containing fasteners allow particles to be crushed freely without magnetic interference, making important contributions to the research of particle physics and the exploration of the mysteries of the universe.

△Large Hadron Collider

The Large Hadron Collider is a "new physics" mechanism for particle physics scientists to explore new particles and microscopically quantify particles. It is a high-energy physics device that accelerates collisions of protons. It is the largest and highest energy in the world. The particle accelerator is composed of a 27-kilometer superconducting magnet ring. It is located in a 17-mile tunnel (including a circular tunnel) 100 meters deep in the Jurassic Mountains near the border between Switzerland and France near Geneva.

The Large Hadron Collider was first tested in September 2008, and the maintenance and upgrade of the accelerator began at the end of 2018. It is expected to resume operation in 2021. In addition to the maintenance of the system, the researchers hope that through this upgrade, the number of collisions per second of the collider can be doubled in order to collect more experimental data. The upgrade project includes replacing the fasteners used to secure the accelerator vacuum tube, because the connection parts made of molybdenum-containing materials are required to ensure the smooth progress of the experiment.

△Large Hadron Collider

When the Large Hadron Collider is in operation, the two particle beams driven by the superconducting magnet collide with each other at a speed close to the speed of light. Before the collision, the particle beam propagates backwards in two separate particle beam tubes that maintain an ultra-high vacuum. Liquid helium cools the superconducting magnet to a temperature lower than outer space: -271.3 degrees Celsius. Before maintenance, the staff must heat the accelerator to room temperature to operate. It is understood that it only takes about four months for the accelerator to heat to room temperature and remove more than 100 tons of liquid helium. Therefore, it is extremely necessary to use high-strength components that can adapt to extreme conditions and have a long life, such as fasteners made of molybdenum alloyed materials. The strength of the fasteners means that they can easily withstand the strength of the upgraded particle beam.

Fasteners used in the upgrade of the Large Hadron Collider have special requirements. Compared with standard 316L stainless steel fasteners, they require higher strength and lower magnetic permeability. The minimum tensile strength needs to be 1000 MPa (the highest tensile strength specified by the relevant ISO standard is 800 MPa), the yield strength is at least 900 MPa (the current standard specifies 600 MPa generally), and the fastener must be non-magnetic to avoid Disturb the movement of particles during acceleration. In order to meet these performance requirements of fasteners, its manufacturer Bumax in Sweden stipulates a high molybdenum content: 2.5%-3% (usually the molybdenum content of 316L is 2%-2.5%).

△Molybdenum-containing fasteners

Higher molybdenum content can not only reduce the magnetic permeability of stainless steel, but also improve the strength of fasteners. Fasteners made of austenitic stainless steel must be cold worked to achieve the tensile strength required to withstand the extreme temperature and strength of the collider. However, in this cold working strengthening process, part of the non-magnetic austenite metallographic structure of 316L stainless steel will be transformed into a magnetically deformed martensite structure. These tiny defects may interfere with the flow of particles between the superconducting magnets, thus hindering the function of the accelerator. Higher molybdenum content helps prevent this martensite transformation.

In addition, the prevention of martensite transformation is also very important for the structure of the collider itself. Therefore, the 27.4-kilometer-long vacuum tube for the large hadron collider, which contains the particle beam, is made of 316LN stainless steel. It is a derivative grade of 316 stainless steel. The higher nitrogen content makes the material have higher strength and prevents the formation of martensite, so that the collider can operate normally.

The above is about the continuous expansion of the application range of molybdenum fasteners, which is collated by Baoji Max Platinum Metal Products Co., Ltd.

Baoji Max Platinum Metal Products Co., Ltd. is a non-ferrous metal processing base in "China Titanium City"-Zhouyuan Industrial Zone, Baoji City, Shaanxi Province. The company is a professional deep-processing enterprise of refractory metals. Pioneering and innovative, determined to make progress-sincerely welcome friends from all walks of life to negotiate business, provide customers with high standards and high quality, tungsten, molybdenum, tantalum, niobium, titanium and other fasteners, screws, bolts, electrodes, precision fasteners and other deep processing product.