A Study On Side Defects Of Hot Rolled Q235B And Q345B Strip Steels

The hot rolled plate, which plays an important role not only in the development of national economy, but also in promoting the development of the national economy, is mainly used in ships, bridges, boilers, containers and also many other aspects just like petrochemical technology, engineering machinery and construction of national defense.Carbon structureal steel, which is applicable to a great variety of construction,bridge, railway, vehicle, vessel and chemical engineering, is produced in large numbers. It has various species and specifications and is a versatile and economical material.Folded groove mark,trimming vertical crack, ordinary vertical crack,cornor crack, edge crack, vertical crack in the side, range peel are seven of the common edge defects during the manufacture of hot rolled plate. Most customers may use edge cutting to make good of the edge defects during use, but as a result of the demand of fieldwork, some users can not cut the edges, and then these defects will seriously affect the usability. Researching the discipline of the formation of the common defects of rolled plate, taking corresponding measures to solve these problems, has an important significance not only to directing manufacture of hot rolled plate, but also to improving the quality and success rate of products.In the seven defects above, studies on folded groove mark, trimming vertical crack, ordinary vertical crack, cornor crack are so much that the forming mechanism of them are revealed comprehensively, however, studies on the latter three defects are comparatively rare, therefore, it is necessary for us to study the forming mechanism of the three defects, which will be helpful to full understanding the production situation and improving the quality of the product.Connecting with the production practice of Laiwu Steel Group, hot rolled plates with the defects of edge crack,vertical crack in the side, range peel, just like Q235B, Q345B, were analyzed by means of macro inspection, optical microscope and electron probe micro-analyser (EPMA), and the formation mechanism of the three defects were obtained through opposite experiment,which have been successfully applied to practical manufacture.