Thanks Chris
Any idea what sort of variation in test results and design parameters could be expected across the three axes?
Cheers
Steve
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To: PipingDesign@yahoogroups.comFrom: chrisw@skypoint.comDate: Thu, 16 Oct 2008 15:43:59 -0500Subject: Re: [PipingDesign] Flange Material
On Oct 16, 2008, at 6:24 AM, Steve McKenzie wrote:> The requirement for circumferential rolling orientation suggests > that the mechanical properties depend (amongst many other things) > on the angle of applied loading in relation to the direction of > rolling. Most books give a tensile strength with no reference load > information.True, but many of the ASTM specs reference the rolling (or forming) direction both for strength and more importantly for toughness. I can't cite you chapter and verse, but most high strength ASME material specs for ferrous material specify Charpy testing taken transverse to the forming direction.> Presumably a piece of steel will have three different tensile > strengths; one for each of the primary axes. I expect the book > values refer to ultimate strength for load applied parallel to > rolling direction. How should we go about deciding on the safe > working load for the other two axes?Actually strength isn't as much of a driver as ductility. Unless a plate is cross rolled the metal grains are preferentially elongated in the direction of rolling. The ductility (elongation and Charpy toughness to name two metrics) are noticeably different parallel and transverse to the rolling direction. Depending on how you strengthen the material (heat treatment or cold or hot work) the strength may also vary.Reduction by cold work is a very important grain refinement technique. If you don't roll material properly you get a coarse grained microstructure at the center of the plate and the possibility of inclusions which may act as crack starters.For flanges, the direction of the normally higher stresses is in the circumferential direction, You normally get better strength and ductility in forgings inherently from the ring rolling process, so the Code wants flanges made from plate to follow suit.Christopher Wright P.E. |"They couldn't hit an elephant atchrisw@skypoint.com | this distance" (last words of
Gen........................................| John Sedgwick, Spotsylvania1864)http://www.skypoint.com/members/chrisw/
[Non-text portions of this message have been removed] Received on Fri Oct 17 16:32:00 2008
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