What is P11 Material?
P11 or T11 or F11 or ASTM A387 Gr. 11, also known as 1.25Cr-0.5 Mo (UNS No.: K11597) is a high-temperature low alloy steel material used mainly in power plants, oil & gas fields for the fabrication of pressure vessels, columns, and pipelines as per ASME Section IX, Section 1 and B31.3, etc. Chromium (Cr) provides elevated-temperature strength, improved oxidation resistance at high temperatures, and increases the tensile strength, yield strength & material hardness.
Molybdenum (Mo) in P11 material rises the load-bearing capacity, Yield strength, hardness, and toughness properties.
The Steel alloy contains 1.25% chromium and 0.5% Molybdenum thus the name is given as 1 1/4Cr-1/2Mo. If the material is supplied in pipe form it is designated as P11, in forging it is called F11, wrought fitting is W11, and casting is WC6.
P11 material specification is A335 for pipe, A213 for Tube, A234 for wrought fitting, for forging A182, For casting A217, and for plate, the material is A387 as shown in the below table.
Chemical and mechanical properties of P11 material
Welding electrode for P11 Material
SMAW or stick welding of P11 material is carried out using E8018-B2 (Low alloy low hydrogen electrodes). E8018-B2 gives the weld deposit as the base metal and matching base metal properties. TIG or MIG welding is carried out using ER80S-B2 filler wire. The SMAW electrodes need to be baked before the welding. Click below for baking requirements.
The typical minimum weld metal deposit chemistry and mechanical properties of E8018-B2 are given in the below table.
Preheating and interpass temperature for P11 Welding
Preheating and interpass temperature for P11 Welding is very critical as the weld metal is air hardenable. If proper preheating is not applied, the weld will be hardened and can get hydrogen cracking. The minimum preheat temperature of 250 °F (120 °C) shall be applied during the welding.
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The interpass temperature is kept at a maximum of 600 °F (315 °C) for P11 material welding.
Post heating or PWHT
Post heating or PWHT of P11 welding is carried out at 650 °C to 705 °C (1,200 °F to 1,300 °F). The holding time is kept at 1 h/25 mm (1 hr/in.) and 15 minimum.
Welding P11 to Carbon Steel
Welding of P11 to Carbon Steel can be carried out using SMAW or stick welding with E7018 or E8018-B2. E8018-B2 is recommended to provide better weldment properties compare to E7018. TIG or MIG welding of P11 is carried out using ER70S-6 or ER80S-B2 filler wire.
Welding P11 to P22 and P91
Welding of P11 to P22 can be carried out using SMAW or stick welding with E8018B3 or E8018-B2. E8018-B3 is recommended.. TIG or MIG welding of P11 is carried out using ER90S-B3 or ER80S-B2 filler wire.
P11 to P91 welding is carried out using E8018-B8 or ER80S-B8 filler wire.