Droplet Transfer Characteristics of High Nitrogen Steel in Ultrasonic Frequency Pulsed GMA Additive Manufacturing

doi:10.12382/bgxb.2023.0721

Abstract

Abstract:

For solving the problems of nitrogen escape and splash in the droplet transfer process of high-nitrogen steel additive manufacturing, the experiment of droplet transfer in an ultrasonic frequency pulsed gas metal arc (UFP-GMA) additive manufacturing is carried out, and the influences of different ultrasonic frequency pulsed current superposition modes and pulse current frequencies on the stability of high-nitrogen steel droplet transfer are studied, The process parameters that can realize the stable droplet transfer of high-nitrogen steel additives were obtained. The experimental results show that the of one-pulse-one-droplet transfer can be realized under the pulsed gas metal arc (P-GMA) process conditions, but the transition stability is poor and the splash is obvious. Superimposing the ultrasonic frequency pulse current at the base current stage of P-GMA or both at the base and peak current stages is not conducive to the droplet transfer, and the problems such as short circuit and droplet explosion are prone to occur. When the low-frequency (20kHz) pulse current is applied during the peak stage, its effect on droplet transfer is minimal. However, the medium-frequency (40-60kHz) pulse currents can be superimposed to inhibit the generation of large particle splash, leading to improved stability in droplet transfer, but many small splashes will be formed during the transition when the frequency exceeds 60kHz.

Key words: ultrasonic frequency pulse current, high nitrogen steel, additive manufacturing, droplet transfer

CLC Number:

TG403

MA Li, FAN Jikang, CONG Baoqiang, YANG Dongqing, PENG Yong, WANG Kehong. Droplet Transfer Characteristics of High Nitrogen Steel in Ultrasonic Frequency Pulsed GMA Additive Manufacturing[J]. Acta Armamentarii, 2024, 45(10): 3686-3695.

Figures/Tables 13

Table 1 Chemical compositions of welding wire and high nitrogen steel substrate %

材料	C	Ni	Cr	Mo	Mn	Si	N	Fe
焊丝	0.028	2.08	22.7	1.19	17.86	0.18	0.99	余量
基板	0.02	1.24	20.8	3.62	17.47	0.85	0.81	余量

Table 2 Process parameters of UFP-GMA additive manufacturing

试验序号	工作模式	I_p/ A	t_p/ ms	I_b/ A	I_pp/ A	脉冲频率/ kHz	占空比/%
1	CP	270	5	35
2	BP	270	5	25	50	50	20
3	PP	260	5	35	50	50	20
4	AP	260	5	25	50	50	20
5	PP-1	260	5	35	50	20	20
6	PP-2	260	5	35	50	40	20
7	PP-3	260	5	35	50	60	20
8	PP-4	260	5	35	50	80	20

Fig.1 Schematic diagram of UFP-GMA additive manufacturing current (PP mode)

Fig.2 Droplet transfer electrical signal of P-GMA additive manufacturing

Fig.3 P-GMA additive droplet transfer process

Fig.4 Droplet transfer process under BP mode

Fig.5 Droplet transfer process under PP mode

Fig.6 Droplet transfer process under AP mode

Fig.7 Droplet transfer processes at different pulse current frequencies

Fig.8 Electrical signals at different pulse current frequencies

Table 3 Nitrogen contents under different processes

测试样	焊丝	试样1	试样5	试样6	试样7	试样8
氮含量/%	0.99	0.71	0.73	0.75	0.79	0.70

Fig.9 Splash diffusion during droplet growth

Fig.10 Appearances of weld seams at different ultrasonic pulse current frequencies

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