An important consideration for induction bends is the use of post bend heat treatments includingnormalise, anneal, temper, and quench and temper.In some cases there may be a conflict between the bending process parameters required to achievematerial properties – for example in heavy wall high strength pipe, the process parameters requiredto achieve the yield strength and tensile strength may cause the outside surface hardness limits to beexceeded. And the only way of solving that problem may be the application of a post bend heat treatment. Heat treatment may also resolve an impasse where the process parameters required tolimit the wall thinning (the bend is formed with very cold extrados) in a critical application, doesnot achieve the required material strength.
Post bend heat treatment is restricted by the size and availability of suitable furnaces. There arevery few furnaces available which are capable of heat treating induction bends made from largediameter pipe. This is especially so for bends which require quench and temper heat treatments.
Incorrect use of post bend temper heat treatments may cause more problems than it solves – in particular a temper heat treatment required for the bend area may adversely affect the unbentstraight tangent on each end of the bend.
Because of the size range of HFW pipe (limited diameter and relatively low wall thickness) and thatthe chemistry is generally well suited to the induction bending process, heat treatment is rarelyrequired for induction bends formed from HFW linepipe.
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