Mechanical Properties and Component Behaviour of X80 Helical Seam Welded Large Diameter Pipes

The paper discusses the development and processing of hot rolled X80 coil material and its conversion into thick-walled helical seam welded pipes. Microstructure, texture and mechanical properties of strips and pipes produced are characterized and compared. High strength characteristics and good deformability as a result of the fine homogenous mainly bainitic microstructure have been determined. Stress strain characteristics and the response to cold deformation during pipe forming have been investigated. Correlations between strip and pipe properties are described and have been used as a data basis for FEM simulations of the pipe forming process. The real pipe behavior has been investigated by means of burst tests performed on 48^″ and 42^″ pipe sections with 18.9mm wall thickness. The results achieved have been compared with results for other pipe grades, dimensions and types of pipe. An outlook will be given on future material and process development steps and use of X80 HSAW-pipes produced.