Re: TORQUING VALUES FOR BOLTS

>Now my query is whether the
>torquing values will be same for carbon steel ,alloy steel, & SS bolts or
>can we use same torquing values for different material bolts like one of
>A193 B8 & other of A453 gr 660c.

No. As you pointed out the torque values are based on yield strength, and the yield strength differs for different materials. Be careful lifting torques from catalogs--don't apply them to other manufacturers fasteners and follw the lubrication instructions carefully. Torques will vary a great deal depending on the thread lubricant and the technique used. The required torque will also depend on the preload value actually needed to maintain a seal. The high torques needed for seating metal ring gaskets withh crush softer materials.

>Also normally what torquing values are supplied in catalogues are for cold
>bolting , what should be the torquing values for hot bolting ?
Depends on the temperature. You don't really need an empirical relationship--estimate the loss in pre-load due to differential thermal expansion and increase the torque to account for the loss. Machinery's Handbook has a very good section on bolting and bolt torques and how to figure what you need.

Christopher Wright P.E.    |"They couldn't hit an elephant at
chrisw@skypoint.com        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)