B Fig. 6 — A — Predicted vs. measured ferrite content; B — Creq/Nieq ratio vs. MT temperatures plot; C — α’martensite (mass %) of different weld metals. from dilution were used to calculate the chromium equivalent (Creq) and nickel equivalent (Nieq) values using the following equations (Ref. 11): Creq = Cr% + Mo% + 0.7 × Nb% (4) Nieq = Ni% + 35 × C% + 20 × N% + 0.25 × Cu% (5) In order to predict the presence of - and - martensite, martensite start temperature (Ms) and -martensite start temperature (Ms), i.e., martensite transformation temperatures, for different weld metals, were calculated using the following equations (Ref. 12): Ms(K) = A3 – 199.8 × (C + 1.4N) –17.9 × Ni – 21.7 × Mn – 6.8 × Cr −45.0 × Si – 55.9 × Mo – 1.9 × (C + 1.4N) × (Mo + Cr + Mn)–14.4 × (Ni + Mn) × (Cr + Mo + Al + Si)1/2 – 410 (6) Ms(K) = A – 710.5 × (C + 1.4N) – 18.5 × Ni – 12.4 × Mn – 8.4 × Cr + 13.4 × Si – 1.6 × Mo – 22.7 × Al + 11.6 × (C + 1.4N) × (Mo+Cr+Mn) – 3.7 × (Ni + Mn) ×(Cr + Mo + Al + Si)1/2 + 277 (7) where A3 is the phase transformation temperature of pure iron, and B A is the fictitious phase transformation temperature of , about 390 K (Ref. 12). Grain Size Measurement The grain sizes of the welds were evaluated by the linear intercept method from the optical micrographs using image analyzing software (Axio- Vision/AxioCam version 4.6). An average of five readings was reported. Ferrite and Martensite Measurement The ferrite percent of each weld metal was evaluated using Feritscope® FMP30, and an average of ten readings was reported. The actual martensite content (C) had been computed from Feritscope data F (% ferrite) using relation C (mass %) = 1.7 × F (Ref. 13), and an average of five readings was reported. Microhardness Testing A microhardness survey was made on flat metallographic specimens across the joints in a Vickers’ microhardness testing machine (Make: LECO Co., USA; Model: LM248AT) using 100 gf load at an interval of 500 m. Tensile Testing Two different tensile specimens were prepared as shown in Fig. 3A and B. The unnotched smooth transverse tensile specimens were prepared to evaluate transverse tensile properties. WELDING RESEARCH 104-s WELDING JOURNAL / APRIL 2015, VOL. 94 Fig. 7 — Xray diffraction pattern collected from different welds. A — J3; B — J2; C — J4; D — J1. Table 3 — Average Bead Geometry for Different Welds Sample Bead Height Bead Width Height to Toe Angle Specification (H) (mm) (W) (mm) Width Ratio (Degree) J1 2.2 ±0.46 9.82 ±0.65 0.224 ±0.03 43.4 ±2.0 J2 2.15 ±0.4 9.89 ±0.50 0.217 ±0.03 42.6 ±2.3 J3 2.03 ±0.38 10.12 ±0.44 0.201 ±0.03 41.3 ±2.0 J4 1.88 ±0.40 10.44 ±0.7 0.180 ±0.03 40.7 ±2.2 A C A C D
Welding Journal | April 2015
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