This paper analyzes the welding technology,welding materials,surface dirt of workpiece and chemical composition of materials,and identifies two causes of cracks:first,heat crack caused by sulfide segregation;second,welding specification is unreasonable.

The test results show that when the appropriate welding specifications are employed by the shielded metal arc welding and the submerged arc welding,the domestic welding materials meet the practical needs.

Welding current and time are the two most important determinants of joint quality in welding conditions.

Based on experimental study on the quantitative influences of welding conditions of SAW upon welds shape,the author derives a mathematical formula of this influence and advances an optimum method for calculating welding parameters of Ⅰ—shaped joints of SAW.

This paper presents the architecture of a network intrusion detection system based on common standard, describes the intrusion specification language through the instance, and analyze the inside communication mechanism and procedure interface standard.