A cone-type piercing mill was developed by the authors for materials with poor hot workability. This piercing mill is called "the super piercer" in Europe and America, This mill has a pair of cone-type main rolls supported at both ends with their roll axes inclined and crossed so as to enable piercing at high feed and cross angies, In order to ensure the best performance of the rotary piercing, disc rolls are adopted instead of plate guide shoes, The super piercer was put into practice at the small-diameter seamless tube plant operated in 1983. The recent progress in our research and development on the super piercer has resulted in the concept of "the new su per piercer", which allows expansion piercing. Namely, the development of the skewing technology for disc roll axes and its application to the cone-type piercing technology has real ized remarkable increase in the expansion ratio, The new su per piercer was adopted as the core technology of the new medium-diameter seamless tube plant operated in 1 997, In this paper, studied in detail were the influences of the piercing ratio, expansion ratio, feed and cross angles for main roll axes and skewangle for disc roll axes on the available piercing size range, KEYWORDS: rotary piercing process; feed angle; cross angle (toe angle, cone angle); skew angle; piercing ratio; expansion ratio; available piercing size range; wall thickness to diameter ratio; Mannesmann piercer; super piercer; new super piercer. l. Introduction The concept of the so-called Mannesmann piercing mill was invented by Mannesmann brothers In Germany in 1886. Over 100 years have passed since then, and the Mannesmann piercing process has becomemalnstream in the field of seamless steel tube manufacturing. Al
A cone-type piercing mill was developed by the authors for materials with poor hot workability. This piercing mill is called “the super piercer” in Europe. It has a pair of cone-type main rolls supported at both ends with their roll axes inclined and crossed so as to enable piercing at high feed and cross angles. In order to ensure the best performance of the rotary piercing, disc rolls are adopted instead of plate guide shoes. The super piercer was put into practice at the small-diameter seamless tube plant operated in 1983. The recent progress in our research and development on the super piercer has resulted in the concept of “the new super piercer,” which allows expansion piercing. Namely, the development of the skewing technology for disc roll axes and its application to the cone-type piercing technology has realized remarkable increase in the expansion ratio. The new super piercer was adopted as the core technology of the new medium-diameter seamless tube plant operated in 1997. In this paper, studied in detail were the influences of the expansion ratio, feed and cross angles on the rotary forging effects, redundant shear deformations and power consumption.
Abstract:An investigation work was made on the influence of the piercing process on the rotary forging effects, redundant shear deformations and power consumption. In this work, a study was made to compare the double and single piercing process with reference to the Mannesmann piercing mill and the cone-type piercing mill developed by the authors. If the conventional double piercing process employing the Mannesmann piercing mill is replaced by the single piercing process employing the cone-type piercing mill, the rotary forging effects and redundant shear deformations can be inhibited, and then, the materials with poor workability, such as stainless and high alloy steel can be pierced without inside bore defects. Furthermore, from the viewpoints of the piercing power and power consumption, the single piercing process employing the conetype piercing mill is very economical. As a result, the single piercing process employing the cone-type piercing mill provides the best economical advantage with respect to both capital and running costs.
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