An investigation into the mechanical properties of super duplex stainless steel at the elevated temperatures expected during induction bending

International Journal of Materials Research

Byrne³

et al. 2010

Deleterious phasesresulting from the induction bending of thick-walledsuper-duplexpipework Temperfree inductionbendingcanh aveasignificantimpacton the mechanicaland corrosion-resistanceproperties of thick-walled superduplexpipe. Sectionsfrom induction bentpipeweresolution annealed at1120 8 Cforv arious periodst osequentiallyeliminated ifferentdeleterious phases.Bycomparing the results of modified DL-EPR analysis,opticalm icroscopy,mechanicaland corrosion testingbeforeand aftert he various heatt reatments,itw as shownthatt he deterioration in propertiesw asduetothe precipitation of a ' .Itwasalsopossible todetermine the orderin which a ' , c 2 and Cr 2 Nhadp recipitated,a nd thus to conclude thatt he unfavourable metallurgyw ast he result of inadequatep ost-bend cooling. Alikelyt hermalh istory fort he pipe isproposed thatleadst othe descriptiono fa modified temperfree process.

Section: Recommended Process Improvementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Deleterious phases resulting from the induction bending of thick-walled super-duplex pipework

International Journal of Materials Research

Byrne³

et al. 2010

“…Although research has been carried out in this area, previously published models produced results where the predicted deformed geometry [3] does not match what has been observed experimentally [2], or described phenomena such as ovality [4] and springback [3,5], which were not observed in test bends by contemporary authors. Previously published FEA of induction pipe bending has tended to be complex, typically using linked thermo-mechanical models [3,4,6].…”

Section: Fe Computational Modelsmentioning

confidence: 99%

“…Although induction bending has been used to bend pipe of a variety of materials, this article concerns only super duplex stainless steel (UNS S32760) -super duplex was chosen, because comprehensive data are available which relate the mechanical properties of super duplex to temperature over a wide range of temperatures [2]. The model was created in such a way that it could be easily adapted for different pipe schedules and bend radii.…”

Section: Model Utilizationmentioning

confidence: 99%

“…The process of temper-free induction pipe bending begins by heating a length of straight pipe using an induction coil to produce localized temperatures in excess of 1100 • C. At this temperature, the material's yield strength may be reduced by as much as 90 per cent [2]. The pipe is gradually pushed forward by a hydraulic ram, while a bending moment is applied (refer to Fig.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Modelling and Predicting the Deformed Geometry of Thick-Walled Pipes Subjected to Induction Bending

Higgins

Proceedings of the Institution of Mechanical Engineers, Part L:

2010

Induction bending offers a rapid, cost-effective method of producing complex convoluted pipework. The resultant bends, however, typically show unwanted geometric deformations which include wall thinning at the extrados, wall thickening at the intrados, awkward transitions on going from tangent to bend, and wrinkling at the intrados surface. All forms of geometric deformation are worse depending on the tightness of the bend and the thickness of the original pipe. Predicting the final geometry of the bend is a non-trivial problem.This article first considers the use of simple analytical models to predict the final deformed geometry of induction bends in thick-walled pipe. It then goes on to compare the predicted geometry obtained from those analytical models with the outputs from empirically derived charts and computational models. The article concludes that empirically derived charts do not offer accurate predictions of wall thinning, are not currently available for intrados wall thickening, and cannot, with confidence, be extrapolated to produce accurate results for very tight bends. Numerical models are developed which predict wall thickening and thinning for any combination of outside diameter/wall thickness/bend radius combination; however, it is concluded that their limited accuracy makes their use questionable. Elastic-plastic FEA is developed which is shown to provide the most consistently accurate means of predicting both wall thickening and wall thinning, and, while not providing a comprehensive prediction of the post-bend geometry did, nevertheless, to go some way towards predicting the overall deformed geometry including transition ramps and intrados surface wrinkling.

An Experimental Evaluation of the Temperature Profiles in Super Duplex Pipe Subjected to Induction Heating and Bending

J. of Materi Eng and Perform

2010

Self Cite

This article briefly explains the technique of induction heating as applied to thick-walled super duplex pipe. It describes the theoretical temperature distribution which might be expected through the wall of such a pipe. An experiment is outlined that uses thermocouples to determine the actual temperature profiles within the wall of induction-heated pipe. The results of the experiment are given, and identifiable trends are discussed. A second experiment is then performed where the pipe is subjected to induction bending, and again the results are explained and discussed. Apparent discrepancies between theoretical and actual temperature profiles are then explained.