Welded heat-treated

Fabricated casings shall be post-weld heat treated. Repairs greater than 10 in. in size shall be post-weld heat treated. All post-weld heat treatment shall be performed in accordance with ASME BPV Code. 

Country Alloy Standard Steel Proce.ss CHEMICAL COMPOSITION % MECHANICAL PROPERTIES (Minimum) Min. Oper. Temp. F Seamless or Weld Heat Treat... 

M. Attallah and H.G. Salem, Effect of Friction Stir Welding Process Parameters on the Mechanical Properties of the As-Welded and Post-Weld Heat Treated AA2095, Proceedings of the Fifth International Conference on Friction Stir Welding, Sept 14—16, 2004 (Metz, France), TWI, paper on CD... 

The CVN transition and Kid properties of 9Cr-l Mo plate steel in normalised and tempered (N+T) and in two simulated post-weld heat treated (PWHT) conditions were also evaluated. PWHT had no significant effect on the properties which is in conformity with the trend in literature where this steel is stated to be remarkably tolerant to wide variations in heat treatment conditions. Moreover, the cleavage strength of this steel was higher than that for the weld reported above, indicating comparatively poorer fincture resistance for the weld material. 

Although it is preferable to post weld heat treat the completed vessel in an enclosed furnace, this is not always possible. If it is not possible to place the entire vessel inside a furnace for PWHT the alternatives are as follows ... 

Heating the vessel portions in more than one heat If the vessel is too long for the furnace then one portion of the completed vessel is post weld heat treated and then the vessel is turned around to do the remaining portion. This method requires a thermal gradient control band for that portion of the vessel extending outside the furnace. The minimum overlap of each portion is 5 feet. 

This procedure is typically done following a repair or as the closure seam for a vessel that is post weld heat treated in multiple sections. 

Item 2 of the report documented HTHA can accumulate in high-stress areas in carbon steel, such as non-post-weld heat-treated welds. The welds of the B and E... 

DOT specification TC/MC-331 prescribes fabrication from steel under Section VIII of the AS ME Boiler and Pressure Vessel Code, and a minimum design pressure of 265 psig (1830 kPa) is required [14]. Steel of a thickness less than 3/16 inch (4.8 mm) must not be used for the shell, heads, or protective housings. Each cargo tank used for ammonia must be post-weld heat treated. The post-weld heat treatment must be performed as prescribed by the ASME Code. See 49 CFR 178.337-1, (f) [9]. 

For a Joint nfficlenc of 0 85 batveen hand and shall. poet weld heat treated... 

Stress relief Coded vessels tjrpically have a metal stamp attached that states, "Do not weld, stress relieved." That means the vessel has been post-weld heat treated to remove stresses in the vessel wall created by welding during fabrication. 

Welding Heat Treating 34 or Casting 36 or Plane Surveying 6... 

Some alkylation processes use concentrated HF instead of H2SO4 as the catalyst. In general, HF is less corrosive than HCl because it passivates most metals by the formation of protective fluoride films. If these films are destroyed by dilute acid, severe corrosion occurs. Therefore, as long as feedstocks are dry, carbon steel - with various corrosion allowances - can be used for the vessels, piping, and valve bodies of hydrofluoric acid alkylation units. AU carbon steel welds that will contact HF, should be post-weld heat treated. 

Sodium hydroxide is widely used in refinery and petrochemical plant operations to neutralize acid constituents. At ambient temperature and under dry conditions, NaOH can be handled in carbon steel equipment. Carbon steel is also satisfactory for aqueous caustic solutions below 50-80 °C, depending on concentration. For caustic service above these temperatures, but below 95 °C, carbon steel can also be used if it has been post-weld heat treated to avoid SCC at welds. Austenitic stainless steels, such... 

Caustic see of carbon steel occurs at temperatures above 50 to 80 °C (120 to 180 °F), depending on caustic concentration. Welded carbon steel components that are exposed to caustic solutions above these temperatures should be post-weld heat treated at 620 °C (115 °F) for 1 h per 25 mm (1 in.) of metal thickness. Caustic SCC of austenitic stainless steels occurs between 105 and 205 °C (220 and 400 °F), depending on caustic concentration. 

To minimize the likelihood of cracking, only low-strength steels, with a maximum tensile strength of 483 MPa (70 ksi), should be used in anhydrous ammonia service. Welds should be post-weld heat treated at 595 °C (1100 °F) or higher, with a maximum allowable hardness of 225 HB. 

All carbon steel vessels should be post-weld heat treated after completion of all welding. Minimum temperature should be 595 °C as stated in NACE MR 0175. This condition will lead to specify a PWHT target temperature of 615 20 °C. 

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