Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(Vol.38 No.443 December 1997)
Effect of Weld Strength on Pipe End Deformation
- Improvement of Roundness at the End of ERW Pipes with Thin Wall IV -
Yoshiaki ITAMI, Matsuo ATAKA and Tetsu MATOBA
(Received on December 2, 1996)
The deformation behavior of electric resistance welded (ERW) pipes resulting from a sizing process was investigated in detail using a 3-dimensional elastic-plastic finite element analysis and an experimental method. The purpose of the study was to establish the effect of welded strength on the deformation of the pipe end after the pipe was cut, which results in the deterioration of the@roundness of pipe end. It was found that the extent@of@deformation to the pipe end, caused by the non-uniform distribution of strength in the circumferental direction, can be controlled by controlling the ratio of the top and bottom to side roll radius on a 4-roll sizer, with a vertical and horizontal roll stand having the same roll caliber as that when combined with a 2-roll sizer. It was also confirmed by calculations and experiments that the decrease of the top and bottom roll radius in the @circumferential seam direction of a pipe, compared with that of the side roll radius on a 4-roll sizer, was greater resulting in the improvement of the roundness of the pipe end.
Key words : residual stress, finite element method, finishing, sizing roll forming, electric resistance welded pipes
Effects of Preforming Methods on Cross-Sectional Shapes of
Extroll-Formed Square Steel Pipes
Fujun LIU, Yoshitomi ONODA, Takuo NAGAMACHI, Sadao KIMURA and Takeo KITAWAKI
(Received on January 16, 1997)
For improvement of the cross-sectional shape (outer curvature, inner curvature, wall thickness change at corner zones, and atness of sides) of square steel pipes (150.0mm wide) formed by use of an extroll-forming mill, two expansion-type preforming processes are used individually to impose peripheral bending on the portions of round pipes (190.7mm in outer diameter, 4.6mm wall thickness) that correspond to the corner zones of the finished product with four inner idler rolls or a pair of four inner and outer idler rolls (outer rolls: grooved rolls). Characteristics of the cross-sectional shapes of the formed square pipes are investigated with respect to the degree of corner bending in the preforming and compared with the results obtained by conventional extroll-forming. The results show that the cross-sectional shape of the finished product can be markedly improved by imposition of an appropriate degree of corner bending on the round pipe by use of a pair of inner and outer preforming rolls.
Key words : roll forming, tube forming, extroll-forming, preforming, round welded steel pipe, square pipe, non-driven grooved rolls
Effects of Forming Conditions on Cross-Sectional Shapes of the
Corner Zones of Square Steel Pipes Formed by an Extroll-Forming
Mill with Expanding Inner Idler Rolls
Fujun LIU, Yoshitomi ONODA, Takuo NAGAMACHI, Sadao KIMURA and Takeo KITAWAKI
(Received on January 16, 1997)
To improve the cross-sectional shapes (outer curvature, inner curvature, wall thickness change) of the corner zones of square steel pipes (150.0, 152.0, 054.0mm wide, STK400, SUS304) formed by an extroll-forming mill, an expanding-type forming tool with 4 idler rolls is introduced into the groove of No. 1 grooved rolls to impose peripheral bending on the portions of the round pipes (D0=190.7mm in outer diameter, t0=4.6, 8.3, 12.0 mm in wall thickness) that correspond to the corner zones of the finished products. Characteristics of the cross-sectional shapes of the corner zones of the square pipes are investigated with respect to the nose angle of the inner roll, the total reduction (=|ln(2H3T/D0), 2H3Theight of groove of finishing (flat) rolls), the n value of the round pipe and the wall thickness (t0) of the round pipe under a condition of the relative expanding stroke Sp (stroke of inner roll)/Spc (Sp for minimum clearance between inner roll and profile of groove of No.1 grooved rolls=t0)=0.97. These are then compared with the results obtained by conventional extroll-forming. The results show that heavy-gauge square steel pipe and the SUS304 square steel pipes both of which have a small outer radius and small change in thickness at each corner zone can be manufactured using a pair of inner idler rolls with large nose angles (about 120.0‹).
Key words : roll forming, tube forming, extroll-forming, round welded steel pipe, square pipe, non-driven grooved rolls, n value
Numerical Analysis of Deformation Behaviour of Edge Portion of Sheet Metal at Breakdown Pass in Roll Forming Process
Manabu KIUCHI and Feizhou WANG
(Recieved on February26, 1997)
Damage to the edge of sheet metals caused by contact between the sheet edge corner and forming roll at the inlet stage is a major obstacle to obtaining high welding quality of electric welded pipes with heavy gauges. In this paper, the deformation behaviour of the edge portion of the sheet metal was systematically investigated using FEM analysis based on an approximate model, and the relationship between edge damage and forming conditions at the breakdown (edge bending) stage was clarified. The following characteristics were found. (1) The metal flow pattern at the edge portion is dominated mainly by the contact condition between the sheet metal and rolls, especially the slope angle of bottom roll surface where the sheet's edge comes into contact with the bottom roll. (2) The deformed shape of the edge portion is also affected greatly by this contact condition. Based on these results, some methods for reducing edge damage during the edge bending at the breakdown stage were suggested, and the efficiency of these methods were verified by numerical simulation.
Key words : roll forming, breakdown, welded pipe, heavy gauge, edge damage, FEM
Proposal of the Flexible Edge Forming Method
- Development of Flexible Edge Forming for ERW Tube I -
Masayuki YAMADA and Tateo YAMADA
(Received on March 12, 1997)
Edge forming is one of the most important processes in the production of ERW (electric-resistance welded) tubes. When edge forming is performed without edge waves, the tube forming process is stable, and the edge joining and welding with squeeze rolls are carried out without any serious problems. For conventional edge forming methods, common rolls are used in the breakdown stands irrespective of the thickness of the walls of tubes. This leads to insufficient edge bending of thin walled plates, and to edge thinning of thick plates in the breakdown stands. In this paper, a new edge forming method, flexible edge forming (FEF), which can overcome the limitations of conventional processing, especially with regards to the forming of thin- and thick-walled tubes, is proposed for ERW tube manufacturing. The FEF method allows the edges to be formed without defects by varying the slant angle of the rolls by achieving a smooth, continuous change of contact point between the rolls and the plate.
Key words : roll forming, edge forming, ERW tube, flexible edge forming, edge bending
Numerical Analysis of Edge Bending of Sheet Metal by Involute Forming Method
Manabu KIUCHI and Feizhou WANG
(Received on April 7, 1997)
In order to produce welded pipes of various sizes and materials without roll change, the ginvolute forming methodh was developed and adopted by the Flexible Forming Mill (FFmill) instead of the conventional gcircular forming methodh. In this study, the finite element analysis technique was used to investigate the relationship between the roll position and sheet deformation in the edge bending process done using the involute forming method. The following results were obtained. (1) Various levels of edge forming/bending can be performed by adjusting the roll positions, and it is possible to obtain a satisfactory edge shape for diverse pipe sizes and material properties. (2) Moreover, due to the advantageous characteristic of the involute rollcaliber, the unformed edge of the sheet can be decreased to a limited range. (3) Due to the well formed shape of the edge, high quality welding is obtained. (4) A comparison between the involute forming method and the circular forming method was also performed. The superiority of the former is obvious when the common use of rolls and the reduced down time caused by roll change are considered.
Key words : roll forming, welded pipe, edge bending, involute forming, circular forming, FEM