Causes of surface black spot and cracks of sponge clamp were analyzed by means of appearance and metallographic observation.

Oxide scale formation during cooling and pickling of Q195 and ST13 steel sheets at different temperature were studied to study the black spots on cold rolled pickled steel sheets.

The examination was made on the black spot defects which occurred on the local areas of the surface of 2A12-T451 plate after anodized in chromic acid.

According to analyzing the phenomena of black spots forming on bead wire,it is considered that such reasons are led to by the water remain on the steel wire after it being washed and the improper packing way as well as the too humid storing environment The methods for solving the problem have been put forwar

Black spots occurred in vacuum ceramic envelope during ceramice metallizing were observed and analyzed.

It is found that the bubbles and black spots on the Al electrode surface was reduced and the luminescence performance of the device was improved obviously after the heat treatment.

The microstructure of GH3044 with freckles was investigated by SEM and EDAX and the variation of liquid concentration during solidification and equilibrium phase transformation was calculated by the Thermal-Calc analysis.

The research development of channel segregation (freckle) during solidification in multi-component systems is discussed, including the freckle characteristic, influencing factor and physical feature.

Mechanisms for Macro Segregation Freckles and Their Criteria;

The results show that black speck is caused by suspending,covering zincilate and silicon oxide;grey speck is caused by bottom zincilate;deep color moire pattern is caused by zinc-iron alloy layer which partly and excessively grows onto the surface of galvanized IF steel sheet.