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Shimonoseki, Japan

Abe H.,ZircoProducts Co. | Furugen M.,Makino Inc.
Journal of Materials Processing Technology | Year: 2012

A new method of evaluating the workability of a tube in cold pilgering has been studied on the basis of material deformability and the effects of process conditions. A circumferential compression test of a tube is confirmed to be an effective evaluation method for deformability. The critical reduction in height upon crack initiation in the compression test is also found to be a good measure of material deformability. Systematic cold pilgering tests and the numerical analysis of cold pilgering are conducted. As a result, the ratio of radial strain to circumferential strain during pilgering is a good indicator of process conditions, and a common mechanism of inner fissure formation during pilgering in stainless steel, titanium alloy, and zirconium alloy is proposed. Finally, a suitable expression for workability is obtained by considering material deformability and the effects of pilgering conditions. These findings will assist the selection of appropriate pilgering conditions to prevent the formation of fissures on the inner surface of a tube. © 2012 Elsevier B.V. All rights reserved. Source


Abe H.,ZircoProducts Co. | Furugen M.,Makino Inc.
Materials Transactions | Year: 2010

The workability in the cold pilgering of a zirconium alloy tube was investigated. In this study, a compression test was proposed as a method of evaluating cold workability. Compression test results showed the effects of heat treatment in the fabrication process and the texture of the tube on the cold workability of a Zircaloy-4 tube shell. Cold pilgering test results ascertained that the reduction in the height of the circumferential- direction specimen of the tube shell at the crack initiation in the compression test was a good measure of cold workability. The numerical analysis results of cold pilgering proved the validity of the compression test as a method of evaluating cold workability. © 2010 The Japan Institute of Metals. Source


Abe H.,ZircoProducts Co. | Nomura T.,ZircoProducts Co. | Kubota Y.,ZircoProducts Co.
Journal of Materials Processing Technology | Year: 2014

A new method of evaluating the lubrication state of a tube in cold pilgering has been studied. A method of calculating the oil film thickness in a bite area on both the outer and inner sides of a tube using the Reynolds equation was proposed. The calculation results revealed that the effects of the tool design, rolling speed, and feed rate on the oil film thickness were significant. Cold pilgering tests were performed on zirconium alloy tubes, including measurement of the oil film thickness using laser equipment and observation of the surface characteristics of tubes. The test results proved the validity of the proposed method. The method is expected to assist the selection of appropriate operation conditions in cold pilgering. © 2014 Elsevier B.V. Source


Abe H.,ZircoProducts Co. | Iwamoto T.,ZircoProducts Co. | Yamamoto Y.,ZircoProducts Co. | Nishida S.,ZircoProducts Co. | Komatsu R.,ZircoProducts Co.
Journal of Materials Processing Technology | Year: 2016

The effects of process conditions on the dimensional accuracy of tubes in cold pilgering were studied. The dimensions included the ovalities of the outer and inner diameters and the eccentricity ratio of the wall thickness. The permissible variations of the dimensions on the objective tubes were of 10 μm order. The process conditions included the feed rate (1.0, 1.5, 2.0, and 2.5 mm/stroke), stroke speed (140, 180, and 200 strokes/min), and turn angle (40, 60, and 80°). The materials tested were type 316L stainless steel and the zirconium alloy Zircaloy-4. The dimensions of the tubes were measured by ultrasonic and laser equipment, and the characteristics of the tubes were determined, such as their hardness, tensile properties, residual stress, and crystallographic texture. The dimensions of the tubes being subjected to cold pilgering were continuously measured by ultrasonic equipment. Strong effects of the feed rate and turn angle on the ovality were observed; the ovality increased with the feed rate. The increase in ovality was thought to be caused by springback. The mechanism underlying the increase in ovality with the feed rate is described by considering the inhomogeneous springback after releasing the tubes from the constraint of the tools. The effect of the turn angle on the ovality was proved to be related to the asymmetric deformation of the tube from the numerical analysis results of cold pilgering. The effect of the springback on the ovality was confirmed by the measurement results for the residual stress. The eccentricity ratio of the wall thickness was unaffected by the process conditions; it was mainly determined by the eccentricity ratio of the mother tube. The eccentricity ratio of 316L tubes decreased after cold pilgering, whereas that of Zircaloy-4 tubes increased. The change in the eccentricity ratio was explained by a self-centering mechanism based on the combined effect of the roll dies and mandrel, and the eccentricity ratio of Zircaloy-4 tubes was proved to be related to the mechanical anisotropy owing to their crystallographic texture. These findings are expected to assist the selection of manufacturing conditions for tubes with close tolerance. © 2016 Elsevier B.V. All rights reserved. Source

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