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Esra In - Istanbul -v0.3-

The best time to visit Istanbul is during spring (April to June) and autumn (September to November). These periods offer pleasant weather, with mild temperatures and lower humidity, making it ideal for sightseeing. Summer can be hot and crowded, while winters are generally cold and wet.

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Fig. 1.

Fig. 1.

Groove configuration of the dissimilar metal joint between HMn steel and STS 316L

Fig. 2.

Fig. 2.

Location of test specimens

Fig. 3.

Fig. 3.

Dissimilar metal joints for welding deformation measurement: (a) before welding, (b) after welding

Fig. 4.

Fig. 4.

Stress-strain curves of the DMWs using various welding fillers

Fig. 5.

Fig. 5.

Hardness profiles for various locations in the DMWs: (a) cap region, (b) root region

Fig. 6.

Fig. 6.

Transverse-weld specimens of DN fractured after bending test

Fig. 7.

Fig. 7.

Angular deformation for the DMW: (a) extracted section profile before welding, (b) extracted section profile after welding.

Fig. 8.

Fig. 8.

Microstructure of the fusion zone for various DSWs: (a) DM, (b) DS, (c) DN

Fig. 9.

Fig. 9.

Microstructure of the specimen DM for various locations in HAZ: (a) macro-view of the DMW, (b) near fusion line at the cap region of STS 316L side, (c) near fusion line at the root region of STS 316L side, (d) base metal of STS 316L, (e) near fusion line at the cap region of HMn side, (f) near fusion line at the root region of HMn side, (g) base metal of HMn steel

Fig. 10.

Fig. 10.

Phase analysis (IPF and phase map) near the fusion line of various DMWs: (a) location for EBSD examination, (b) color index of phase for Fig. 10c, (c) phase analysis for each location; ① DM: Weld–HAZ of HMn side, ② DM: Weld–HAZ of STS 316L side, ③ DS: Weld–HAZ of HMn side, ④ DS: Weld–HAZ of STS 316L side, ⑤ DN: Weld–HAZ of HMn side, ⑥ DN: Weld–HAZ of STS 316L side, (the red and white lines denote the fusion line) (d) phase fraction of Fig. 10c, (e) phase index for location ⑤ (Fig. 10c) to confirm the formation of hexagonal Fe3C, (f) phase index for location ⑤ (Fig. 10c) to confirm no formation of ε–martensite

Fig. 11.

Fig. 11.

Microstructural prediction of dissimilar welds for various welding fillers [34]

Fig. 12.

Fig. 12.

Fractured surface of the specimen DN after the bending test: (a) fractured surface (x300), (b) enlarged fractured surface (x1500) at the red-square location in Fig. 12a, (c) EDS analysis of Nb precipitates at the red arrows in Fig. 12b, (d) the cross-section(x5000) of DN root weld, (e) EDS analysis in the locations ¨ç–¨é in Fig. 12d

Fig. 13.

Fig. 13.

Mapping of Nb solutes in the specimen DN: (a) macro view of the transverse DN, (b) Nb distribution at cap weld depicted in Fig. 12a, (c) Nb distribution at root weld depicted in Fig. 12a

Table 1.

Chemical composition of base materials (wt. %)

C Si Mn Ni Cr Mo
HMn steel 0.42 0.26 24.2 0.33 3.61 0.006
STS 316L 0.012 0.49 0.84 10.1 16.1 2.09

Table 2.

Chemical composition of filler metals (wt. %)

AWS Class No. C Si Mn Nb Ni Cr Mo Fe
ERFeMn-C(HMn steel) 0.39 0.42 22.71 - 2.49 2.94 1.51 Bal.
ER309LMo(STS 309LMo) 0.02 0.42 1.70 - 13.7 23.3 2.1 Bal.
ERNiCrMo-3(Inconel 625) 0.01 0.021 0.01 3.39 64.73 22.45 8.37 0.33

Table 3.

Welding parameters for dissimilar metal welding

DMWs Filler Metal Area Max. Inter-pass Temp. (°C) Current (A) Voltage (V) Travel Speed (cm/min.) Heat Input (kJ/mm)
DM HMn steel Root 48 67 8.9 2.4 1.49
Fill 115 132–202 9.3–14.0 9.4–18.0 0.72–1.70
Cap 92 180–181 13.0 8.8–11.5 1.23–1.59
DS STS 309LMo Root 39 68 8.6 2.5 1.38
Fill 120 130–205 9.1–13.5 8.4–15.0 0.76–1.89
Cap 84 180–181 12.0–13.5 9.5–12.2 1.06–1.36
DN Inconel 625 Root 20 77 8.8 2.9 1.41
Fill 146 131–201 9.0–12.0 9.2–15.6 0.74–1.52
Cap 86 180 10.5–11.0 10.4–10.7 1.06–1.13

Table 4.

Tensile properties of transverse and all-weld specimens using various welding fillers

ID Transverse tensile test
 All-weld tensile test
TS (MPa) YS (Ϯ1) (MPa) TS (MPa) YS (Ϯ1) (MPa) EL (Ϯ2) (%)
DM 636 433 771 540 49
DS 644 433 676 550 42
DN 629 402 785 543 43

(Ϯ1) Yield strength was measured by 0.2% offset method.

(Ϯ2) Fracture elongation.

Table 5.

CVN impact properties for DMWs using various welding fillers

DMWs Absorbed energy (Joule)
 Lateral expansion (mm)
1 2 3 Ave. 1 2 3 Ave.
DM 61 60 53 58 1.00 1.04 1.00 1.01
DS 45 56 57 53 0.72 0.81 0.87 0.80
DN 93 95 87 92 1.98 1.70 1.46 1.71

Table 6.

Angular deformation for various specimens and locations

DMWs Deformation ratio (%)
Face Root Ave.
DM 9.3 9.4 9.3
DS 8.2 8.3 8.3
DN 6.4 6.4 6.4

Table 7.

Typical coefficient of thermal expansion [26,27]

Fillers Range (°C) CTE (10-6/°C)
HMn 25‒1000 22.7
STS 309LMo 20‒966 19.5
Inconel 625 20‒1000 17.4