JINAN -- A Chinese steel mill on Tuesday rolled off the world's largest seamless ring forging piece, which was developed especially as the key part of a nuclear power unit.

The loop-shape stainless steel piece, produced by the Shandong Iraeta Heavy Industry Co Ltd based in East China's Shandong province, weighs 150 tonnes and is 15.6 meters in diameter, breaking both the world records of its kind.

The product was developed by the Institute of Metal Research under the Chinese Academy of Sciences and ordered by the China National Nuclear Corporation.

It is expected to play the supporting function in a nuclear reactor vessel to withstand pressure up to 7,000 tonnes.

The giant steel structure used to be forged by segmented welding assembly. However, the welding joints are vulnerable to high pressure, which poses safety concerns in nuclear power generation.

Large seamless steel forging pieces are in high demand in China's hydro-power, wind-power and nuclear-power generation industry.