研究目的
Understanding the role of filler wire addition in laser-MIG hybrid welding (LHW) process as compared with that in autogenous laser welding (ALW) process during welding of 10-mm-thick maraging steel plates.
研究成果
1. The chemistry of the LHW joint showed less Ni, Mo, and Ti when compared with the base metal due to the usage of filler wire with reduced solute content. The composition of the ALW fusion zone matched with that of the base metal since it involved melting and solidification of only the base metal.
2. The volume fraction of RA formed after aging was dependent on the as-welded fusion zone chemistry. The LHW joint had 2.5% and 2.6% RA in AFZ and LFZ respectively, whereas the fusion zone of ALW joint showed greater than 5% RA after aging.
3. While the joint efficiencies were as good as the base metal, KIc fracture toughness values reduced considerably. The ALW fusion zone showed a very low KIc fracture toughness value of 49.44 MPa√m. The LHW fusion zone exhibited comparatively better KIc fracture toughness of 77.4 MPa√m.
4. The fine structure and high volume fraction of precipitates contributed to high strength in ALW welds. On the other hand, fine structure means less intercellular spacing (the spacing between RA pools). Hence, the fusion zone of ALW weld failed easily by linking a series of voids which formed in the soft austenite pool.
5. LHW resulted in welds with comparatively lesser volume fraction of austenite as compared with ALW. By optimization of process parameters, it was possible to produce welds with substantially low volume fraction of reverted austenite and hence improved fracture toughness.
研究不足
The study focuses on the comparison between LHW and ALW processes for welding M250 maraging steel thick sections, specifically addressing the role of filler wire addition. The limitations include the specific conditions and parameters used in the study, which may not be universally applicable to all welding scenarios or materials.
1：Experimental Design and Method Selection:
The study involved single-pass LHW of 10-mm-thick maraging steel plates using a combination of 3.5-kW CO2 laser and synergic pulse MIG welding power source at a welding speed of 1 m/min. MIG filler wire with reduced solutes such as Mo and Ti contents was used for the LHW process. Simultaneously, double-sided single-pass ALW of similar plates was performed.
2：5-kW CO2 laser and synergic pulse MIG welding power source at a welding speed of 1 m/min. MIG filler wire with reduced solutes such as Mo and Ti contents was used for the LHW process. Simultaneously, double-sided single-pass ALW of similar plates was performed.
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: M250 grade maraging steel plates of 10 mm thickness received in solution annealed condition were used for the study. Filler wire M250 W2 type having a diameter of 1.2 mm was used for laser-MIG hybrid welding.
3：2 mm was used for laser-MIG hybrid welding.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: The laser hybrid welding system comprised the Rofin DC035 slab CO2 laser integrated with KEMPPI PROMIG 530 (Synergic) welding system. A 300-mm focal length mirror was used to get a laser beam spot size of 180 μm.
4：Experimental Procedures and Operational Workflow:
The plates were prepared with a Y-groove edge configuration, 16° included angle, and a root face height of 2.5 mm. A root gap of 0.2 mm was maintained between the plates during welding. The shielding gas mixture of 80% He + 20% Ar was passed through the MIG welding torch.
5：5 mm. A root gap of 2 mm was maintained between the plates during welding. The shielding gas mixture of 80% He + 20% Ar was passed through the MIG welding torch.
Data Analysis Methods:
5. Data Analysis Methods: The chemistry of the fusion zone in as-welded condition was studied using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The percentage of reverted austenite in the fusion zone microstructures after post-weld aging treatment was measured using image analysis software.
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