Compared with industrial developed countries, there is a big gap in the production of large steel castings in China in terms of product variety, process level, quality grade and manufacturing equipment.
In the large-scale nuclear power equipment, the main pump, nuclear power turbine cylinder and other large steel castings are mostly made of stainless steel, with extremely high quality requirements. China has not mastered the independent production technology and basically relies on imports. The main gaps are as follows:
① Chinese enterprises have not mastered the overalland technology of such large ;
② The level of chemical composition control in material smelting, especially harmful trace elements control and steel purity control is not high;
③ There is a gap in the control of material mechanical properties and the stability of casting quality.
The representative steel castings in large hydropower units are the upper crown, lower ring and blade of runner. The quality of these castings directly affects the service performance of the whole hydro generator unit – unit output, efficiency, cavitation erosion and stability. Compared with foreign advanced enterprises, the gap of domestic runner is mainly reflected in:
① The product design level is not high;
② The level of manufacturing technology is low, such as there is a big gap in casting technology and heat treatment technology;
③ The quality stability of casting products is not high, and the technical level of dimensional inspection and quality inspection is low.
Due to the existence of the above gaps, China’s large casting industry is lower than foreign advanced enterprises in comprehensive indicators such as labor productivity, hot processing output value, output and quality cost, and its comprehensive capacity is about 5 ~ 10 years behind that of advanced countries.