Expected to Be Applied to Machining Hard-to-Manufacture Parts of Complex Shapes

The National Research Foundation of Korea (KRF) recently announced that a research team led by professor Lee Young-kook (Yonsei University) developed a new super-plastic steel material that is economical and relatively easy to produce.
Recently, shapes of components used in various industrial fields such as automobiles and aircraft have become increasingly complicated, and it is necessary to mold and assemble such hard-to-machine components of complicated shapes. In order to overcome these disadvantages, much attention is being paid to super-plastic steel materials and moldings that can create parts of complex shapes through a single process.

So far, various super-plastic materials have been developed but are difficult to commercialize. Zinc and aluminum alloys have low strength after molding. Raw materials for nickel and titanium alloys and stainless steels are expensive, and high carbon steel has a problem of a complicated manufacturing process.

The research team successfully developed an ultra-fine, medium manganese steel material with an elongation rate of up to 1341%, using medium manganese steel actively studied recently.

The researchers used medium manganese steel with manganese (6.6%) and aluminum (2.3%). This alloy can produce fine grains which are important prerequisites for a super-plasticity phenomenon due to a difference in the distribution of manganese and aluminum when undergoing heat treatment after a rolling process.

In addition, the research team conducted a tensile test at a temperature range of 650°C to 900°C, and found that the elongation rate was up to 1,314% at 850°C and rose over 300% at 650°C, a relatively low temperature.

The super-plastic medium steel material developed in this study is economical compared to conventional super-plastic stainless steel and high carbon steels because small amounts of manganese and aluminum go into the material and can be manufactured using a conventional steelmaking process. In particular, medium manganese steel has an advantage of easily forming crystal grains of several hundred micrometers to several micrometers, which are important for super-plasticity.

“We anticipated that this research will make it easier for various industries to manufacture parts of complex shapes difficult to mold, while requiring high strength by using new super-plasticity steel materials with excellent cost-cutting effects,” Professor Lee said.

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