SeAH Besteel begins mass production of domestically developed steel for robot joints

SeAH Besteel has developed and begun mass-producing special steel for robot reducers using domestic technology, breaking a long-standing dependence on Japanese and other foreign suppliers. The company plans to expand its product line from industrial robots to special steel for humanoid robots.

SeAH Besteel announced Tuesday that it had developed and commercialized special steel for reducers, a core component in robot motion systems.

A reducer converts the high-speed rotation of a motor into the speed and torque a robot needs, functioning much like a human joint. For a robot arm or leg to move precisely to a set position, minimizing the gaps between gears inside the reducer is critical.

The newly developed special steel is used in the flex spline, a key internal component that transmits motor force within the reducer. Because the part bends and moves repeatedly, it demands both machining precision and durability.

SeAH Besteel focused particularly on reducing the microscopic warping that metals undergo during heat treatment. Through proprietary alloy design, the company engineered the material to hold its shape under temperature changes and impact, improving the dimensional accuracy needed for precision machining.

The steel was also reinforced to prevent cracking even as robots repeat the same motions countless times.

To achieve this, the company applied a vacuum refining process to remove microscopic impurities from the steel. Fewer impurities lower the risk of cracks forming under repeated stress, extending the service life of reducer components. SeAH Besteel said the process enabled it to produce high-purity special steel.

The project has already moved beyond the development stage. SeAH Besteel made its first supply of special steel for industrial robot reducers to domestic precision reducer maker SPG in February and has since entered full mass production.

The development is significant for bringing the supply chain of a key robot component back onshore. The market for special steel used in robot reducers had long been heavily dependent on a small number of foreign suppliers, particularly from Japan.

SeAH Besteel is now targeting the humanoid robot market beyond industrial robots. Building on its mass-production experience with flex spline steel, the company plans to develop additional special steel grades applicable to the joints and drive units of humanoid robots.

"Achieving mass production using purely domestic technology in a market that has been almost entirely dependent on a handful of foreign companies, particularly Japanese ones, is a highly meaningful accomplishment," a SeAH Besteel official said. "Self-sufficiency in core materials is essential for the domestic robot ecosystem to grow, and we will continue to lead the localization of high-quality special steel to help the Korean robot industry build a firm competitive edge on the global stage."

Meanwhile, SeAH Besteel's holding company is also expanding its special materials business into the aerospace sector. SeAH Superalloy Technology, a special alloy production subsidiary under construction in Texas, is expected to begin commercial production as early as the first half of next year.