Table 1.
The chemical composition of welding wires (wt%)
| C | Mn | Nb | B | Ni | Cr | N | Si | Mo | W | V |
|---|---|---|---|---|---|---|---|---|---|---|
| 0.100 | 0.890 | 0.0350 | 0.003 | 0.680 | 8.790 | 0.073 | 0.220 | 0.780 | 1.570 | 0.200 |
Table 2.
The chemical composition of deposited metal (wt%)
| C | Mn | Nb | B | Ni | Cr | N | Si | Mo | W | V |
|---|---|---|---|---|---|---|---|---|---|---|
| 0.099 | 1.010 | 0.033 | 0.004 | 0.660 | 8.338 | 0.070 | 0.180 | 0.68 | 1.310 | 0.170 |
Fig. 1.
Schematic diagram of multi-layer welding
Table 3.
Welding parameters
| Welding Beads | Welding current/A | Welding voltage/V | Welding speed/(cm·min–1) | Interlayer temperature/°C | Heat input/KJ/cm |
|---|---|---|---|---|---|
| 1 | 250 | 12 | 14 | 25 | 12.86 |
| 2 | 250 | 12 | 14 | 96 | 12.86 |
| 3 | 250 | 12 | 14 | 170 | 12.86 |
| 4 | 250 | 12 | 14 | 226 | 12.86 |
| 5 | 250 | 12 | 14 | 240 | 12.86 |
| 6 | 250 | 12 | 14 | 190 | 12.86 |
| 7 | 250 | 12 | 14 | 190 | 12.86 |
| 8 | 250 | 12 | 14 | 190 | 12.86 |
| – | – | – | – | – | – |
| 28 | 250 | 12 | 14 | 190 | 12.86 |
| 29 | 250 | 12 | 14 | 190 | 12.86 |
| 30 | 250 | 12 | 14 | 190 | 12.86 |
Fig. 2.
Location of deposited metal impact and tensile specimens
Fig. 3.
Sketch map of tensile samples processing
Fig. 4.
Size of thermal expansion sample
Fig. 5.
Deposited metal microstructure: a-50 μm, b-20 μm
Fig. 6.
Holding temperature of heat treatment at 740°C: (a) 2 h, (b) 4 h, (c) 8 h
Fig. 7.
Holding temperature of heat treatment at 760°C: (a) 2 h, (b) 4 h, (c) 8 h
Fig. 8.
Holding temperature of heat treatment at 800°C: (a) 2 h, (b) 4 h, (c) 8 h
Fig. 9.
Second phase of deposited metal: (a) Tempering area, (b) Non-tempering area
Fig. 10.
Average impact toughness of deposited metalheat treatment curves
Fig. 11.
Average hardness of deposited metal-heat treatment curves
Table 4.
Fiber fracture rate of deposited metals
| Tempering temperature (°C) | Holding time (h) | Fiber fracture rate /% | ||
|---|---|---|---|---|
| T = 2h | T = 4h | T = 8h | ||
| 740 | Measured value | 20; 22; 24 | 36; 37; 41 | 82; 83; 86 |
| Average value | 22 | 38 | 84 | |
| 760 | Measured value | 35; 35; 43 | 52; 54; 51 | 48; 55; 50 |
| Average value | 84 | 86 | 89 | |
| 780 | Measured value | 86; 84; 88 | 87; 85; 86 | 89; 88; 85 |
| Average value | 86 | 86 | 87 | |
Fig. 12.
Fiber fracture rate of deposited metals-heat treatment curve
Fig. 13.
Impact fracture morphology at tempered 740°C: (a) 2 h, (b) 4 h, (c) 8 h
Fig. 14.
Impact fracture morphology at tempered 760°C: (a) 2 h, (b) 4 h, (c) 8 h
Fig. 15.
Impact fracture morphology at tempered 800°C: (a) 2 h, (b) 4 h, (c) 8 h
Fig. 16.
Microstructure morphology of weld simulation t8/5: (a) 5 s, (b) 10 s, (c) 20 s, (d) 70 s
Fig. 17.
Relationship between impact toughness of weld and t8/5
Fig. 18.
Relationship between hardness of weld and t8/5
Fig. 19.
Impact fracture morphology of thermal simulation t8/5: (a) 5 s, (b) 10 s, (c) 20 s, (d) 70 s