Google "Ultrasonic Velocity Table" and you will find several returns to get this information. There are also some very good articles within NDT.net regarding issues and complexities of UT done on stainless welds.
That is an excellent question that I am sure will draw a big discussion. Stainless steel is a funny animal with respect to UT. It has different velocities in each and every direction. Particularly with shear waves and even more so with heat affected zones and the weld metal itself.
Stainless steel can change direction of shear waves, mode convert and actually bend the sound beams once they enter the HAZ and the weld.
What type of Stainless steel are you examining? Basically it depends on the heat input during welding and the microstructure of the material after welding. It is coarse grained so you need to have very experienced UT techs that can recognize different reflections.
Im sure Mark Davis and Ed Ginzel and other experts in this area can give you a lot more insight on this subject.
Well ed, Experienced my tech is not, and i believe the grade is 301. Im only a ut ltd thickness inspector, so they sent me a tech and he is fresh ou of ocean corps, working on a machine he has never used and a cal block that hes never seen as well. Also due to lack of smart people in the office they have sent us a carbon steel block, thats why i am trying to find the velocity so as to cal to the carbon steel and then change the velocity
Been there, tried that. Works fairly well on thickness, doesn't work at all for shearwave. Different velocity gives different refracted angle. Now you don't have a valid velocity or angle, and you don't know where your indications are. If the test piece is clean, you're OK. If it has indications, you're lost.
Machine an ID and OD notch into a scrap piece of the pipe. Lacking machining capability, use a thin grinder wheel [cut-off disk] and make notches. Crank in a nominal velocity of 1235. Now you know where the ID & OD are, and you can get some idea where the indications are.
Really Tom, from the conditions you have described my advise would be to postpone the inspection whilst a Level III approved procedure is made available or formalised. This will include (amongst others) equipment including porbes to be used, operator experience of st. steel welds, applicable calibration and sensitivity blocks, test methodology including sizing method and acceptance criteria.
If you have any control of the situation, just postpone it until the above is satisfactorily organised.
Oops! Forgot to mention that the way we got ourselves out of the problem on the S/S shearwave was to have a S/S IIW block and S/S ASME Basic block expedited from PH Tool. Phil got us taken care of. Stayed late and made the Basic block, then Overnighted it. Not a cheap way out, but one that meets Code.
Do NOT use a Square-Wave pulser on S/S, Spike only. As Nigel Armstrong aluded to, stainless welds have a perverse grain structure, that 'eats' sound. Thus his recommendation for Level III input.
Your best [and most expensive] calibration block is an actual weld in something of very similar diameter and thickness, made using the same weld process. With accurate, ASME-sized ID and OD notches in the weld, you now can be CERTAIN that your inspection is accurate. Thats what my Level III requires.