TPT January 2013

Article

High chromium casting roll for straightening steel pipe, welding pipe and cold roll formed steel By Yuan Houzhi and Liu Xingyi (Shandong Province SiFang Technical Development Co, Ltd Jinan 250101, China)

welding pipe roll and cold roll formed steel roll in traditional design is alloy forging steel. Usually D2 and H13 are used in the design in America, X155CrVMo121 and X40CrMoV5-1 in Germany , SKD11 and SKD61 in Japan, Cr12MoV, 3Cr2W8V, Cr12, 9Cr2Mo and GCr15 in China. D2, X155CrVMo121 and SKD11 are about the same with Cr12MoV. They are cold working die steel with high carbon and high chromium, and it is a basic kind of cold working die steel. In production, D2, X155CrVMo121 and SKD11 forging steel rolls, which are used in advanced rolling pipe mills, specially under the condition of speedily cooling and speedily heating, are all designed to avoid the phenomenon of crack on roll face and looseness of roll shaft. Now Cr12MoV forged steel roll is only used in small size roll for welding pipe production lines in China and the great majority of mills are still using low class forging steel roll consisting of Cr12, 3Cr2W8V, 9Cr2Mo and GCr15. [1] These rolls have poor wear resistance and the service life is only 1 / 2 ~ 1 / 3 of above mentioned imported forging steel roll. For example, the sticking steel phenomenon has appeared in the use of domestic forging steel roll used in mills on stainless steel welding pipe production lines, and the wear is produced on the roll surface to use domestic GCr15 roll in 500x500x20mm square pipe mills when used more than once per month. The straightening pipe roll, HFW/ERW welding pipe roll and cold roll formed steel roll belong to special-shaped roll. This kind of roll is possessed of the features of complex shape, more size and small batch, etc. Especially when producing HFW/ERW welding pipe roll and cold roll formed steel roll, one drawing only produces one or two products, the maximum weight of product can be up to 8-10 tons per piece andminimum weight of product can be up to 58kg per piece. This kind of roll is difficult to produce to use forging tool steel – the inside hole can not be forged and the utilisation factor of material is lower than 50 per cent. D2, X155CrVMo121, SKD11 and Cr12MoV materials have narrow forgeable temperature area and large forged difficulty so the material has low utilisation factor and high energy consumption. Because the roll has complex shape and a big differential on wall thickness, the heat treatment has greater difficulty. China national standard “cast iron roll” and “cast steel roll”, which was applied in 2009 only contains the rolls for rolling

1 General The roll itself is the key component of the mill and the first aim of a rolling mill is to meet the different standards demanded in each country. At present in China various rolling mills and technical equipment levels have been measured that easily compete with those built around the world and the technical level of rolling steel now matches the world’s most advanced levels of machinery. In recent years China has introduced and constructed an increasing number of steel pipe production lines that meet world-class standards and some of the types of lines are not found anywhere else in the world. Now China’s steel pipe production industry is one of the largest in the world and as a result the consumption of rolls is also the largest in the world. The production of advanced steel pipe mills and high grade alloy steel pipe make high demands of the roll itself. Through cooperation and technical innovation the quality and production process and productivity are continuously increasing in the roll manufacturing industry in China. 2 Straightening pipe roll, HFW/ ERW welding pipe roll and cold roll formed steel roll The material design of rolls is a basic part of machinery design. The material used for steel pipe straightening rolls, HFW/ERW New high chromium alloy casting roll researched and developed by Shandong Province Sifang Technical Development Co Ltd (SDSF) for straightening steel pipe, HFW/ERW welding pipe and cold roll formed steel. It can successfully meet the production requirements of advanced steel pipe production mills and high grade alloy steel pipe production lines and the service quality and service life of that can be comparable to D2, X155CrVMo121, SKD11 classic forging steel roll and match the world’s most advanced levels. The casting roll has significant advantages compared with the same kinds of forging roll in its manufacturing method and manufacturing cost and has a marked improvement in energy resource saving and material saving.

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January 2013