*2.4. Sample Fabrication*

A commercial 304 stainless steel plate of 200 mm × 150 mm × 3 mm was used as a base plate to prepare the bead on plate welds, using 308L stainless steel wire of 1.2 mm (nominal diameter) as the electrode. The weld groove shape is "I" with no gap. The chemical composition of the base plate and filler wire is given in Table 1. Gas composed of 98% argon and 2% O2 was used as shield gas (20 L/min). The contact tip to base plate distance was 15 mm. In this paper, the influences of current waveform parameters on the weld pool behavior and microstructure of DP-GMAW were studied, which are thermal pulse frequency (TPF), thermal pulse current change (ΔI) and duty ratio of thermal pulse peak phase (DTp), respectively. As a comparison, the weld pool behavior and weld metal microstructure of P-GMAW were also studied. Welding parameters are listed in Table 2.

**Table 1.** Material characteristics of the base plate and welding wire.



**Table 2.** Welding parameters.

**Note:** ITp = the average current at the peak of the thermal pulse; ITb = the average current at the base of the thermal pulse; TPF = thermal pulse frequency; ΔI = ITp − ITb, DTp = duty ratio of thermal pulse peak phase; V = voltage; Speed = weld speed; DP = DP-GMAW, P = P-GMAW.
