Research And Application Of Magnetic Controlled Submerged ARC Overlay Welding Process

The longitudinal magnetic fields are used during the welding process to make charged particle in welding arc rotating in a high speed, then change the form and static characteristics arc. Through the electromagnetic stirring, the process of mass transfer and heat transfer of the fluent metal in the crystallization process are changed, thereby affect the parent materials melting, welding shape and welding quality. In foreign countries it's called "none-defect welding".In this paper, the low frequency electromagnetic control technology is introduced to roll submerged arc overlaying technology. A single wire submerged arc welding magnetic head is designed in this paper, the insulation, cooling and seal of the head is designed to avoid the external factors interference magnetic field during welding process. According to the characteristics of big welding current, large pool and long duration in submerged arc welding process. The old electromagnetic stirring device is improved, output power is increased, the magnetic field parameters adjustment range is broaden. The improved electromagnetic stirring device can satisfy the requirement of submerged arc welding.During submerged arc welding process, the 16Mn steel is welded by using self-made magnetic control device. Under the external longitudinal magnetic field, the weld forming mechanism, and the different magnetic field parameters impact on the microstructure and hardness and wear-resisting performance was studied. Through a lot of experiments, satisfactory welding parameters and the magnetic field parameters are obtained: welding current is 400A, welding voltage is 30V and welding speed is 30 cm/min, exciting current is 2A, magnetic field frequency is 2Hz. Experimental results show that, with the low-frequency magnetic field intensity increasing, the submerged arc welding seam width increases and the depth decreases; without the magnetic field affect, the average grain intercept is 25.6μm, the metal surface hardness is HRC50.83, wear lossΔG = 0.035g; with the effect of magnetic field, the average grain intercept is 10.6μm, the metal surface hardness is HRC55, wear lossΔG = 0.015g, the weld microstructure get refinement. X-ray diffraction(XRD) analysis results show that the solid carbide in deposited metal increases, with the effect of longitudinal magnetic field, the distribution of ferromagnetic materials and paramagnetic material Cr₂₃C₆ are changed, thus the hardness and resistance of overlay welds are improved.