difference between tp316 and mt316

I believe the TP is supposed to be an abbreviation for Type, as in Type 316 stainless steel. This is poor form for engineering work and should not be used. Regards, Cory Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.Thanks for the reply CoryPad but I don't think that Type is the answer. I realize now that I should have posted this question in the ASTM forum but I wasn't a subscriber to it. I dug out a few of the ASTM standards this morning and started looking a little deeper. ASTM A213 designated grades for seamless tube walls for Ferritic & Austenitic Alloy Boiler Superheater & Heat-Exchanger Tubes and ASTM A269 Seamless & Welded Austenitic SS Tubing for General Service both use TP (TP 316) in their material designations. I assume TP stands for "TubePipe". The reason for this assumption was fortified when I reviewed ASTM 511 for Seamless Stainless Steel Mechanical Tubing which uses MT in their alloy designations (MT 316) and ASTM A276 Standard Specification for Stainless Steel Bars & Shapes uses no lettering in their alloy designations (316).Can't put my hands on a published document to back this up - but I've heard that "TP" stands for Tubular Product (Tube/Pipe makes sense as well). "F" stands for Forging (A182), "C" for Casting (A351)..I agree with CoreyPad that TP = Type. Although the only official ASTM mentions are in piping specifications, e.g., A312, it clearly refers to the austenitic alloy and not the form, e.g., as AISI grades also used in pressure vessels. see below. Further, use of TP has been discontinued as redundant in SS Grade specifying. see below. Also, TP has never been used to designate Tubular Products of any other material (to my knowledge), although it would have been if it indeed indicated form. From ASTM A312/A312M-03 Standard Specification for Seamless and Welded Austenitic Stainless Steel Pipes "Note 1—When the impact test criterion for a low-temperature service would be 15 ft-lbf [20 J] energy absorption or 15 mils [0.38 mm] lateral expansion, some of the austenitic stainless steel grades covered by this specification are accepted by certain pressure vessel or piping codes without the necessity of making the actual test. For example, Grades TP304, TP304L, and TP347 are accepted by the ASME Pressure Vessel Code, Section VIII Division 1, and by the Chemical Plant and Refinery Piping Code, ANSI B31.3, for service at temperatures as low as -425oF [-250oC] without qualification by impact tests. Other AISI stainless steel grades" astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/ "Work Item Summary Copyright 2003 ASTM International. All rights reserved. WK1264 Standard Specification for Seamless and Welded Austenitic Stainless Steel Pipes Work Item Type: Revision of A312/A312M-03 Developed by Subcommittee: A01.10 Date Initiated: 06-04-2003 1. Rationale Drop TP from Grade Names as serving no purpose. {my emphasis} Was identified as 012T-9. ------------------------------------------------------------ Keywords austenitic stainless steel; seamless steel pipe; stainless steel pipe; steel pipe; welded steel pipe; 23.040.10" [pasted link didn't work. Go to astm.org and search for WK1264]