„Super Steel”: China Unveils Game-Changing Cryogenic Steel for Fusion Reactors

China has developed a breakthrough material, CHSN01 (China high-strength low-temperature steel No 1), capable of withstanding extreme cold and massive magnetic forces, and deployed it this year in the world’s first fusion nuclear power generation reactor, according to SCMP.

The steel puts China at the forefront of materials science and could have applications beyond fusion.

The ultra-strong cryogenic steel meets the demands of superconducting magnets operating near absolute zero and in magnetic fields of up to 20 Tesla. It can endure stresses of 1,300MPa and has superior fatigue resistance to traditional alloys. “In addition to its applications in superconductivity, this steel can also be used in other related areas,” said Zhao Zhongxian, a top Chinese physicist.

Development began after a 2011 setback at the International Thermonuclear Experimental Reactor (ITER) in France, where cryogenic steel turned brittle under testing.

China’s team, led by Li Laifeng of the Chinese Academy of Sciences, spent over a decade refining the material—starting with nitrogen-enhanced stainless steel, then incorporating vanadium and controlling carbon/nitrogen ratios.

Foreign experts had called the new approach “absolutely impossible,” but Zhao encouraged persistence: “Do not blindly trust foreign authorities. This matter is worth pursuing.”

In 2021, China set strict specifications—1,500MPa yield strength and over 25% elongation at cryogenic temperatures—described by fusion expert Li Jiangang as essential for the country’s compact fusion devices.

SCMP writes that the High-Strength Steel Research Alliance, uniting institutes, companies, and welding specialists, fast-tracked progress through biweekly technical forums and independent testing.

By August 2023, CHSN01 met all targets and entered production for the Burning Plasma Experimental Superconducting Tokamak (BEST), now under construction and due for completion in 2027. Of its 6,000 tonnes of components, 500 tonnes of conductor jackets are made from CHSN01.