Causes and Elimination of Black Spots Defects on the Surface of Nodular Cast Iron Cylinder Head
Author of the article:GAO Bo;YAN Jiangbo;WANG Bin;CAO Gang;MA Yuliang;HE Yingzi;YANG Junjun
Author's Workplace：l.The Navy Military Representative Office in Xingping Region,Xingping 713105,China;Shaanxi Diesel Engine Heavy Industry Co.,Ltd.,Xingping 713105,China
Key Words：cylinder head black sports carbon equivalent
Abstract：The nodular cast iron cylinder head of a diesel engine was made of QT500-7.After finish machining,"black spots"appear on the upper machined surface,especially on the cylinder head,there were many parts near the edge of casting and sand core,resulting in the batch scrapping of the cylinder head.Through metallographic analysis and scanning electron microscope analysis,the causes of defects were found out and the proper smelting process was worked out.The results show that the surface pitting defects can be eliminated by controlling the carbon silicon equivalent of liquid iron,reducing the amount of spheroidizing agent and inoculating agent,and increasing the pouring temperature.
