TPT-January-2015

Article

Shandong SiFang Technical Development Co Ltd

New material development and manufacture of crimping dies in UOE welded pipe plant By Li Xin-wen, Zhou Gui-de, Li Jian-xin and Su Qi-shuang from Baoshan Iron & Steel Co Ltd, Shanghai, China and Shandong SiFang Technical Development Co Ltd, Jinan, Shandong, China

Field practice experience and numerical simulation results demonstrate that during the UOE process, if there were no crimping process, both plate margins of about 300mm width (both sides of the welding seam after O-forming) would be difficult to improve significantly even after compression ratio 2 per cent of O press and expansion ratio 3 per cent of expanding machine, resulting in the difficulties of pre-welding process adjustment, burning through of submerged arc welding, cold cracking of expanding process and pipe defect peaks from normal pipe contour. In JCO (including PFP) processing method, if there were no crimping process, pipe defect peaks from normal pipe contour would be more serious than that in UOE processing. As can be seen from the development of crimping technology, a roller-type crimping process has been used in the early crimping technology, which is generally used for thin steel plates but it does not have an ideal effect on high strength plate due to the longitudinal extending of plate margins. The die-type crimping process has been the advanced technology developed for thick plates, in which two presses of thousands of tons force crimp plates step by step by pushing both plate margins upwards with dies of several metres long at the same time. Desirable shape of the plate margins induced by the process prevents cold cracking of expanding process and

1 Introduction of crimping press Crimping is one of the major processes of a LSAW (longitudi- nally submerged arc welding) steel pipe production line, which results in the bending deformation of both plate sides; after crimping, both sides become the arc of the curvature radius close to the finished pipe radius in order to ensure geometrical dimensional accuracy of the pipe welding seam area. There has been no crimping process in the early LSAW pipe production line, such as the world’s first industrial production line of UOE welded pipe in McKeesport, USA, in 1951. The second generation of UOE welded pipe mills were built from 1955 to 1967, and a portion of a total of 18 sets of new mills and one set of reconstructive mill have adopted roller-type crimping presses. The third generation of UOE mills appeared between 1968 and 1979, during when the crimping process developed dramatically from roller-type to die-type, and in total there are 16 sets of new mills put in use and two sets of old ones reconstructed all over the world. Since the 1990s, there have been more than ten large diameter JCO (including PFP) or RB production lines constructed in the world, of which JCO lines have adopted the die-type crimping process. This article introduces the function of the crimping processing, the technical development and the structure of the crimping press at first; then narrates the status in active service of the crimping die, its critical quality requirements and also its manufacture technical difficulty. The material and the corresponding manufacture process, which meet the requirements of the crimping processing, have been developed through the characteristics analysis of the former German dies, such as chemical composition, surface hardness and geometry size. After manufacture completion of the new dies, the testing results show that there are no remarkable differences in surface hardness, tensile strength and impact toughness between new dies and former German dies; after volume production experiment of welded pipes, there are scarcely any quality defects in the new dies by offline inspection.

Roller-type crimping press

Die-type crimping press

Figure 1: Structure schematic diagram of crimping press

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J anuary 2015