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Open AccessArticle

The Microstructure and Mechanical Properties of Multi-Strand, Composite Welding-Wire Welded Joints of High Nitrogen Austenitic Stainless Steel

by 1,2, 1,2, 3, 3 and 1,2,*
1
School of Materials Science and Engineering, Tianjin University, Tianjin 300072, China
2
Tianjin Key Laboratory of Advanced Joining Technology, Tianjin 300072, China
3
Jiangsu Lianjie Welding Technology Co., Jiangyin 214400, China
*
Author to whom correspondence should be addressed.
Materials 2019, 12(18), 2944; https://doi.org/10.3390/ma12182944
Received: 16 August 2019 / Revised: 2 September 2019 / Accepted: 3 September 2019 / Published: 11 September 2019
(This article belongs to the Special Issue Microstructure and Mechanical Properties of Steels)
A multi-strand composite welding wire was applied to join high nitrogen austenitic stainless steel, and microstructures and mechanical properties were investigated. The electrical signals demonstrate that the welding process using a multi-strand composite welding wire is highly stable. The welded joints are composed of columnar austenite and dendritic ferrite and welded joints obtained under high heat input and cooling rate have a noticeable coarse-grained heat-affected zone and larger columnar austenite in weld seam. Compared with welded joints obtained under the high heat input and cooling rate, welded joints have the higher fractions of deformed grains, high angle grain boundaries, Schmid factor, and lower dislocation density under the low heat input and cooling rate, which indicate a lower tensile strength and higher yield strength. The rotated Goss (GRD) ({110}⟨1 1 ¯ 0⟩) orientation of a thin plate and the cube (C) ({001}⟨100⟩) orientation of a thick plate are obvious after welding, but the S ({123}⟨63 4 ¯ ⟩) orientation at 65° sections of Euler’s space is weak. The δ-ferrite was studied based on the primary ferrite solidification mode. It was observed that low heat input and a high cooling rate results in an increase of δ-ferrite, and a high dislocation density was obtained in grain boundaries of δ-ferrite. M23C6 precipitates due to a low cooling rate and heat input in the weld seam and deteriorates the elongation of welded joints. The engineering Stress–strain curves also show the low elongation and tensile strength of welded joints under low heat input and cooling rate, which is mainly caused by the high fraction of δ-ferrite and the precipitation of M23C6. View Full-Text
Keywords: high nitrogen austenitic stainless steel; multi-strand composite welding wire; electron backscatter diffraction; welding thermal cycle; mechanical property; microstructure high nitrogen austenitic stainless steel; multi-strand composite welding wire; electron backscatter diffraction; welding thermal cycle; mechanical property; microstructure
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Li, J.; Li, H.; Liang, Y.; Liu, P.; Yang, L. The Microstructure and Mechanical Properties of Multi-Strand, Composite Welding-Wire Welded Joints of High Nitrogen Austenitic Stainless Steel. Materials 2019, 12, 2944.

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