Effect of nitrogen content on the microstructure and properties of the laser-arc hybrid welding joint of high nitrogen steel
Introduction
High nitrogen steel (HNS) is a newly developed material in which the nitrogen content is more than 0.4% [1], [2]. HNS are steels that combine high strength and ductility with good corrosion resistance specifically used in the arms, aerospace, cryogenic and medical device industries [3], [4], [5]. Nitrogen is one of the most important alloying elements in HNS because it can increase strength without significantly losing ductility [6], [7].
Many studies have been performed on the weldability of HNS, specifically related to nitrogen loss. In the welding process of HNS, nitrogen is easy to precipitate from the base metal, enabling lower nitrogen content in the weld than that in the base metal, which results in the degradation of joint properties [8], [9], [10]. To solve the problem of nitrogen loss in the weld, some researchers increase the nitrogen content in weld by controlling the composition of shielding gas, such as increasing the nitrogen partial pressure or adding a small amount of oxygen [11], [12], [13], [14]. In addition, researchers have used nitrogen-containing filler materials to increase the nitrogen content in the weld, or increased the content of manganese, chromium, and other alloy elements in the weld to improve nitrogen solubility in stainless steel [15], [16], [17], [18]. However, some studies have shown that when the nitrogen content of the weld increases, the mechanical properties of the joints do not significantly improve. Also, when the nitrogen content is too high, the mechanical properties of the joints begin to decrease [10], [19], [20], [21]. This is contradictory to the normal relationship between nitrogen content and performance in the base metal, so further research on this relationship is necessary.
Laser-arc hybrid welding technology has attracted wide-ranging attention for its advantages of large welding penetration, good bridging performance, and high welding speed [22], [23], [24]. It has been widely used in automobiles, ships, oil pipelines, and other fields [25], [26], [27]. Researchers have studied the influence of laser-arc hybrid welding process parameters on the structure and properties of HNS-welded joints. The study found that the weld structure is composed of austenite and a small amount of ferrite; large heat input makes the dendrites coarser, resulting in poor weld impact performance [28], [29]. Bai et al. [30] studied the corrosion behavior of laser-arc hybrid welded joints of HNS. It was found that the growth mode and density of dendrite were the most important factors affecting the corrosion behavior.
Current research on the welding technology of HNS primarily focuses on arc and laser welding. The published literature on laser-arc hybrid welding technology of HNS is less and typically focuses on the effects of process parameters on microstructure and properties. In previous research, the author's team solved the problem of nitrogen porosity in laser-arc hybrid welding of HNS through detailed process control methodologies. Based on the previous research, the present work studies the effects of nitrogen content in the weld on the resultant microstructure and properties.
Section snippets
Materials
The material used in this research is HNS. HNS plates with dimensions of 8 mm × 400 mm × 100 mm were cleaned with acetone to remove dirt and contamination. The test was conducted to obtain full penetration of 8 mm-thick specimens for a butt weld configuration with a Y-groove preparation. A schematic view of the welded sample is shown in Fig. 1. The welding wire with a diameter of 1.2 mm was used as the filler material for the hybrid welding test. The chemical compositions of the base material
The effect of nitrogen content on the microstructure of HNS welds
Fig. 4 shows the effect of different nitrogen content on the microstructure of the weld. When the nitrogen content is 0.38%, the microstructure of the weld is composed of coarse lath ferrite and austenite matrix. As the nitrogen content increase from 0.42% to 0.49–0.52%, lath ferrite gradually transforms into dendritic ferrite. Also, with increasing nitrogen content, the tertiary dendrite arms of the ferrite gradually disappear, and the trunk of the dendrite becomes thinner. Since nitrogen is a
Conclusion
In this study, to obtain HNS-welded joints with different nitrogen contents, HNS was welded by laser-arc hybrid welding with different various shielding gases. The effects of nitrogen content in weld on the microstructure and properties of the weld were studied, and the following conclusions were drawn:
- (1)
As the nitrogen content of the weld increases, the ferrite morphology changes and the size decreases. Nitrogen as an austenite-forming element can inhibit ferrite growth.
- (2)
As the nitrogen content
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funding
2021 Doctoral (Talent) Research Startup Fund (Natural Science) of Jilin Agricultural Science and Technology University: [2021] No. 5001.
References (32)
- et al.
Research progress and development tendency of nitrogen-alloyed austenitic stainless steels
J. Iron Steel Res. Int.
(2015) - et al.
Development of nitrogen-containing nickel-free austenitic stainless steels for metallic biomaterials
Mater. Sci. Eng.: C
(2004) - et al.
Influence of nitrogen and heat input on weld metal of gas tungsten arc welded high nitrogen steel
J. Iron Steel Res. Int.
(2007) - et al.
Effect of nitrogen addition on microstructure and fusion zone cracking in type 316L stainless steel weld metals
Mater. Sci. Eng. A
(2003) - et al.
Hot cracking susceptibility in laser weld metal of high nitrogen stainless steels
Sci. Technol. Adv. Mater.
(2004) - et al.
Shielding gas effects on double-sided synchronous autogenous GTA weldability of high nitrogen austenitic stainless steel
J. Mater. Process. Technol.
(2017) - et al.
Analysis of droplet transfer mode and forming process of weld bead in CO2 laser-MAG hybrid welding process
Opt. Laser Technol.
(2012) - et al.
Effects of relative positioning of energy sources on weld integrity for hybrid laser arc welding
Opt. Lasers Eng.
(2016) - et al.
Relationship between pool characteristic and weld porosity in laser arc hybrid welding of AA6082 aluminum alloy
J. Mater. Process. Technol.
(2017) - et al.
Stability evaluation of laser-MAG hybrid welding process
Opt. Laser Technol.
(2019)
Characteristics analysis of droplet transfer in laser-MAG hybrid welding process
Int. J. Heat Mass Transf.
Nitrogen containing austenitic stainless steels
Materialwiss. Werkst.
High nitrogen steels. Manufacture and application of high nitrogen steels
ISIJ Int.
Nickel free high nitrogen austenitic steels
ISIJ Int.
Manufacture and application of high nitrogen steels
ISIJ Int.
Effect of thermo-mechanical treatment on mechanical properties of high-nitrogen containing Cr-Mn-Ni austenitic stainless steels
ISIJ Int.
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2023, Journal of Manufacturing ProcessesCitation Excerpt :A strong relationship between arc morphology and welding process stability can be presumed. A laser-arc welding process was carried out by Li et al. [8] in welding HNS, and a positive correlation between arc energy and porosity in the weld metal was found, also reported by Cui et al. [9]. By comparing arc welding and CO2 laser welding in HNS, Dong et al. [10] found that there was just a slight increase in the nitrogen content for the laser weldment, but a sharp increase was observed in the arc weldment with the increase in nitrogen partial pressure.