Rotary Forming for the Straightening of Tubing

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K. Kawai et al. / Journal o f Materials Processing Technology 48 (1995) 135-141
ment was commercially aluminum seamless pipe, JIS All00-TD, with t h e i n i t i a l o u t e r d i a m e t e r o f 35 ram, wall thickness o f i mm a n d l e n g t h o f 500 mm. T h e o u t e r d i a m e t e r a n d the wall thickness of s e a m l e s s p i p e used in the experiment was selected as about 1/10 size of the actual large diameter seamless pipes whose curved shape near both ends causes trouble in industry. Assuming the Swift-type stress-strain relationship for this material, the flow s t r e s s in the uniaxiai tension is given by (~ = 136(0.002 + E p) 0.0493 MPa. Before the straightening experiment, pipe specimen was so bent as to give a curved shape whose radius of curvature i s e i t h e r 60 mm o r 180 ram. The straightening experiment was carried out at room temperature without any lubricant after degreasing the surfaces of s p e c i m e n and rollers. While the nominal reduction in radius was defined by t h e o u t e r d i a m e t e r of s p e c i m e n a n d the gap of rollers, the actual reduction in radius measured from outer diameters before and after straightening, except for the experiment by convex rollers, was less than 0.25% at the most. Three types of roller, flat roller, concave roller and convex roller were used in the experiment. Since it was clarified that the longer roller gives the higher straightening ratio in the preliminary straightening experiment without feed angle, the l e n g t h of r o l l e r s w a s d e t e r m i n e d a s to be maximum supported by the roller-holding attachment. The length and the outer diameter of f l a t r o l l e r a r e 72 mm a n d 60 ram. The radii of curvature of c o n c a v e r o l l e r a n d c o n v e x r o l l e r a r e 675 mm a n d 69.8 ram, r e s p e c t i v e l y . The straightening ratio is defined
ELSEVIER
Journal o f Materials Processing Technology 48 (1995) 135-141
Materials Processing Technology
Journalof
Rotary Ken-ichi
Forming Kawai, Hakoto
for
the
A new straighterfing method using rotary forming with three rollers is proposed. A h e l i c a l r o l l i n g mill w i t h t h r e e r o l l e r s i s u s e d i n t h e e x p e r i m e n t . The prebend aluminum seamless pipes are straightened under various working conditions. It is clarified that an attainable straightening ratio of the product can be determined by the pitch and the nominal reduction in r a d i u s , a n d t h e r e e x i s t s a minimum l e n g t h of r o l l e r s to g u a r a n t e e the selected straightening ratio. The curved shape can be straightened u p t o 90% under optimum working conditions. It is also clarified that there exists an maximum p i t c h to g u a r a n t e e a c e r t a i n s t r a i g h t e n i n g ratio and the axial feed rate can be selected arbitrarily in practice.
1. INTRODUCTION S e a m l e s s p i p e s , s u c h a s oil c o u n try tubular goods, are mainly m a n u f a c t u r e d b y s e a m l e s s p i p e mills s u c h a s p l u g mill a n d m a n d r e l rail/. A solid round billet is uniformly heated in a furnace and pierced by a piercer. Then a hollow shell is roll-reduced in outside diameter and wall t h i c k n e s s . The rolled tubing is simultaneously burnished inside and outside by a reeler and t h e n s i z e d i n t h e s i z i n g roll. A common fault in manufacturing of seamless pipes is that the product is not straight. The curved tubing is effectively straightened by a rotary straightener but the curved s h a p e n e a r b o t h e n d s of t u b i n g is not corrected completely by the straightener [1]. In order to reduce the cropping l o s s of b o t h e n d s of t u b i n g it is important to develop a straightening method for the curved shape
Straigபைடு நூலகம்tening Yukio Inoue and
of Haruhiko
Tubing Sugita
Satake,
Department of Hechanical Engineering and Haterials Science, Faculty of Engineering, Yokohama National University, 156 Tokiwadai, Hodogaya-ku, Yokohama, 240 Japan
near both ends of tubing. In the present paper, the authors propose a straightening method using rotary forming with three rollers.
2. EXPERIMENTAL PROCEDURE
Roller aoOre,