Hits:

Affiliation of Author(s):材料科学与技术学院

Title of Paper:The porosity formation mechanism in the laser-MIG hybrid welded joint of Invar alloy

Journal:OPTICS AND LASER TECHNOLOGY

Key Words:Porosity Invar alloy Laser-MIG multi-layer hybrid welding Microstructure Energy dispersive spectroscopy (EDS) X-ray diffractometer (XRD)

Abstract:The porosity formation mechanism in the laser-metal inter gas (MIG) multi-layer hybrid welded (HW) joint of 19.05 mm thick Invar alloy is investigated. The microstructure characteristics and energy dispersive spectroscopy (EDS) are analyzed. The phase identification was conducted by the X-ray diffractometer (XRD). Experimental results show that the generation of porosity is caused by the relatively low laser power in the root pass and low current in the cover pass. It is also indicated that the microstructures of the welded joints are mainly observed to be columnar crystal and equiaxial crystal, which are closely related to the porosity formation. The EDS results show that oxygen content is significantly high in the inner wall of the porosity. The XRD results indicate that the BM and the WB of laser-MIG HW all are composed of Fe0.64Ni036 and gamma-(Fe,Ni). When the weld pool is cooled quickly, [NiO] [FeO] and [MnO] are formed that react on C to generate CO/CO2 gases. The porosity of laser-MIG HW for Invar alloy is oxygen pore. The root source of metallurgy porosity formation is that the dissolved gases are hard to escape sufficiently and thus exist in the weld pool. Furthermore, 99.99% pure Argon is recommended as protective gas in the laser-MIG HW of Invar alloy. (C) 2017 Elsevier Ltd. All rights reserved.

ISSN No.:0030-3992

Translation or Not:no

Date of Publication:2017-10-01

Co-author:Gao, Qiyu,Gu, Cheng,Sun, Weihua,Chen, Jicheng,Wei Yanhong

Correspondence Author:Xiaohong Zhan