Table 2
Chemical composition of the weld metal (wt%)
| No. | C | Si | Mn | Nb | W | Cr | Mo | P/S | Ti | Ni |
|---|---|---|---|---|---|---|---|---|---|---|
| 1# | 0.03–0.05 | 0.2–0.4 | 3.2–3.8 | 1.10 | 1.6–1.8 | 12.5–13.0 | 7.4–7.7 | ≤ 0.015 | 0.10–0.13 | Bal. |
| 2# | 0.03–0.05 | 0.2–0.4 | 3.2–3.8 | 1.30 | 1.6–1.8 | 12.5–13.0 | 7.4–7.7 | ≤ 0.015 | 0.10–0.13 | Bal. |
| 3# | 0.03–0.05 | 0.2–0.4 | 3.2–3.8 | 1.52 | 1.6–1.8 | 12.5–13.0 | 7.4–7.7 | ≤ 0.015 | 0.10–0.13 | Bal. |
Fig. 1
Tensile specimen of deposited metal and its sampling position
Fig. 2
Drawing of weld metal impact sampling
Fig. 3
Position diagram of welding joint hardness test position
Fig. 4
Schematic diagram of welding groove
Table 3
Welding parameters of deposited metal
| Welding current (I/A) | Welding voltage (U/V) | Welding speed (v/cm/min) | Inter channel temperature (T/°C) | Heat input (E/kJ/cm) |
|---|---|---|---|---|
| 95 | 27 | 13 | 100 | a |
Table 4
Mechanical properties of 9Ni steel
| Tensile Strength (Rm/MPa) | Yield strength (Rp0.2/MPa) | Elongation (A/%) | Impact absorbing energy Akv/J (−196°C) |
|---|---|---|---|
| 727 | 668 | 27 | 231, 240, 233 234.7 |
Fig. 5
Microstructure and electron microscopic structure of 9Ni steel as observed by optical microscope (A) and SEM (B). SEM, scanning electron microscopy
Fig. 6
Macro diagram of metal weld bead
Fig. 7
Penetration test of molten metal: (A) 1#; (B) 2#; (C) 3#
Fig. 8
Pore image under optical microscope
Fig. 9
Slag interlocking between welding channels
Fig. 10
Intergranular hole
Fig. 11
Crack morphology and its energy spectrum of 3# deposited metal: (A) crystal crack; (B) morphology of crystal crack; (C) energy spectrum
Table 5
Precipitates’ composition of 3# deposited metal (wt%)
| Precipitates | S | Cr | Mn | Fe | Ni |
|---|---|---|---|---|---|
| Content | 2.50 | 13.42 | 3.59 | 4.19 | 74.34 |
Fig. 12
Macromorphology of 2# deposited metal
Fig. 13
Microstructures of the root and surface of the deposited metal: (A) the root; (B) the surface
Fig. 14
Microstructure of three kinds of deposited metals: (A) 1#; (B) 2#; (C) 3#
Fig. 15
Austenite grain boundary microstructure of three kinds of deposited metals: (A) 1#; (B) 2#; (C) 3#
Fig. 16
Metallographic microstructure of the welding channels for the 2# deposited metal
Fig. 17
Scanning position and the line scanning result of the element
Fig. 18
Variations among Ni, Cr, and Mo contents within the 2# deposited metal weld: (A) Ni, (B) Cr, (C) Mo
Fig. 19
Variation among Fe and C contents within the 2# deposited metal weld
Fig. 20
Precipitation and energy spectrum of granular Nb carbides
Fig. 21
Precipitation and energy spectrum of long strip Nb carbides
Fig. 22
Ellingham chart [20]
Fig. 23
Morphology and energy spectrum of WC precipitates
Fig. 24
Precipitation of Al and Ti oxides
Fig. 25
Precipitation of Nb carbide
Fig. 26
Morphology and energy spectrum of 1# deposited metal precipitates
Fig. 27
Morphology and energy spectrum of 2# deposited metal precipitates
Fig. 28
Morphology and energy spectrum of 3# deposited metal precipitates
Fig. 29
Morphology and EDS analysis of precipitates of deposited metal. (A) 3#SEM, (B) 3#EDS. EDS, energy dispersive spectrometer; SEM, scanning electron microscopy
Fig. 30
Zigzag grain boundary
Fig. 31
Intergranular cracking and precipitates of the three deposited metals: (A) SEM, (B) First measuring point and element analysis, (C) Second measuring point and element analysis, (D) Third measuring point and element analysis. SEM, scanning electron microscopy
Table 10
Composition of deposited metal precipitates (wt%)
| Precipitate | Nb | Ni | Al | Ti |
|---|---|---|---|---|
| 1 | 33.19 | 15.82 | 14.27 | 19.71 |
| 2 | 47.19 | 14.99 | 9.47 | 15.29 |
| 3 | 46.16 | 18.98 | 8.80 | 13.53 |
Fig. 32
Precipitate morphologies: (A, C, E) root of 1#, 2#, 3# welding; (B, D, F) surface of 1#, 2#, 3# welding
Fig. 33
Quantity of precipitated phases of the three deposited metals
Table 11
Tensile properties of welding rod deposited metal
| No. | Tensile Strength (Rm) MPa | Yield strength (Rp0.2) MPa | Elongation (A)% | Section shrinkage (Z)% |
|---|---|---|---|---|
| 1# | 687 | 429 | 33.1 | 33 |
| 2# | 705 | 478 | 32.5 | 34 |
| 3# | 710 | 482 | 27.5 | 30 |
Fig. 34
Intergranular crack in tensile test: (A) 1#; (B) 2#; (C) 3#
Fig. 35
Longitudinal distribution of hardness of deposited metal
Table 12
Impact resistance of deposited metal
| No. | Akv/J |
|---|---|
| 1 | 132, 133, 126, 140, 126 |
| 2 | 115, 123, 119, 112, 113 |
| 3 | 80, 89, 82, 95, 92 |
Fig. 36
SEM morphologies of impact fracture of deposited metal: (A) 1#, (B) 2#, (C) 3#. SEM, scanning electron microscopy