expect that the stainless steel shell is quite a bit thicker than the fitting, and the shell’s cylindrical shape will give it considerable stiffness, so most or all of the yielding will have to be in the flange of the fitting. The AK Steel online Data Bulletin provides typical yield strength of 304 as a function of temperature, as shown in Table 1. Also included in Table 1 are the reduction factors (ratio of elevated-temperature yield strength to room-temperature yield strength), from the AISC Design Guide 30: Structural Stainless Steel, to be applied to the design of stainless steel construction. The two sources provide similar information. Local heating with a torch would be very risky in this case because of the temptation to direct the heat on the surface for a while, then withdraw the torch and test the surface temperature with a temperature-indicating crayon. You can easily exceed the suggested temperature limit before you realize it. I suggest you use electric strip heaters for the heating, and use thermocouples or an optical pyrometer to measure temperature continuously to be sure that 750°F is not exceeded. Table 1 indicates that the yield strength of 304 stainless steel at 750°F is likely to be about one-half of that at room temperature. So there will be some help in your attempt to realign the fitting. But, because the flange diameter is greater than the pipe diameter, there will also be a tendency for the pipe to bend more easily than the flange, even if the pipe is kept cold. I suggest you put a sleeve (a largerdiameter pipe that just fits over the neck of the fitting) to stiffen your lever arm when trying to bend the flange of the fitting. In summary, your welder’s idea is not a bad idea, but its execution is not without risk. If you follow the guidelines herein, I think you can be successful, though I would not guarantee it.♦ DAMIAN J. KOTECKI is president, Damian Kotecki Welding Consultants, Inc. He is treasurer of the IIW and a member of the A5D Subcommittee on Stainless Steel Filler Metals, D1K Subcommittee on Stainless Steel Structural Welding; and WRC Subcommittee on Welding Stainless Steels and Nickel-Base Alloys. He is a past chair of the A5 Committee on Filler Metals and Allied Materials, and served as AWS president (2005–2006). Send questions to damian@ damiankotecki.com, or mail to Damian Kotecki, c/o Welding Journal Dept., 8669 NW 36th St. # 130, Miami, FL 33166-6672. WELDING JOURNAL 21 Table 1 — Effect of Temperature on 304 Stainless Steel Yield Strength Temperature, °F (°C) 68 (20) 200 (93) 400 (204) 600 (316) 750 (399) 800 (427) AK Steel Typical YS, ksi (MPa) 36 (241) — 23 (159) 20 (134) — 17 (114) AISC Reduction Factor 1.00 0.80 0.65 0.59 0.55 0.54 For info, go to www.aws.org/ad-index
Welding Journal | January 2014
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