equivalent CEIIW or CEPCM value be calculated and included in the PQR. The CEIIW or CEPCM value provides an indication of the base metal’s weldability based on hardness and hardenability. As defined within API 5L (Ref. 2), the CEIIW value is calculated (Equation 1) when the base metal’s carbon content is >0.12%. Also, as denoted within API 5L, the CEPCM value is calculated (Equation 2) when the base metal’s carbon content is ≤0.12%. For each equation, the respective carbon equivalent value is calculated to 1) evaluate a base metal’s weldability; 2) estimate the minimum preheat and interpass temperatures; and 3) approximate the minimum critical cooling rate required to mitigate detrimental untempered martensite from forming. CEIIW = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15 C > 0.12% (1) CEPCM = C + Si/30 + (Mn + Cu + Cr)/20 + Ni/60 + Mo/15 \ + V/10 + 5B C ≤ 0.12% (2) Due to the significance of hardness and hardenability, the carbon equivalent equations are cited in weld codes/standards (Ref. 6). When utilizing the equations, it is prudent to remain vigilant of 1) the actual carbon (C) content of the base metal and the hardness value; 2) the level of weld joint restraint; and 3) the hydrogen control method. Figure 4 shows pipe welding where the CEIIW value for API 5L X65 pipe is 0.43 (Ref. 6). Alleviating HIC A great deal of hydrogen control and HIC information is available in code books, articles, and handbooks. The methods noted as follows are based upon the literature and weld failure lessons learned. To alleviate conditions for weld deposit/HAZ microstructure HIC, it must be realized there are synergic relationships that exist between weld variables — Fig. 5. In qualifying a PQR, particularly for a cold climate region and/or a sour service environment, it is important that welding engineers be careful to • Reduce weld joint stress by mini- Project Pivotal Points: Welding Engineering 76 WELDING JOURNAL / JUNE 2016 Fig. 5 — Full encirclement reinforcement saddle weld on a 20-in.-diameter pipe. • Ensuring welders/pipeliners meet performance qualification requirements • Conducting weld safety, workmanship quality, materials, and technique training • Protecting personnel and the welding work area during construction activities (see figure below) • Specifying/planning of process for equipment, consumables, and tooling for the application (see figure below) • Qualifying PQRs/WPSs that meet code/standard, engineering authority, and DOT stipulations (Top) For pipeline construction, weld shelters are carried by sidebooms from weld joint to weld joint to provide weld crew protection from Arctic weather. (Bottom) A pipeliner’s welding rig.
Welding Journal | June 2016
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