The Study on Welding Technology of 9Ni Steel

Abstract:

9Ni steel is a low temperature serving ferrite steel, providing high strength and excellent low temperature toughness, which could serve well at-196°C. Therefore 9Ni steel is widely used in storage tanks and transport ships for liquefied natural gas (LNG). Nevertheless there are some challenges in the industrial application, such as hot cracking, cold cracking, magnetic arc blow, etc.. In this paper, the study on the welding technology of 9Ni steel developed by Baosteel is carried out. Firstly the weldability is analyzed through welding thermal simulation using Gleeble 3500 system, Y-groove cracking test, maximum hardness in weld heat-affected zone test. The results prove that 9Ni steel could be welded without preheating. The welding consumables have also significant influence on the performance of the welded joints. In this paper the characteristics of different types of welding consumables, including ferrite base type, austenitic stainless steel type, Ni-base alloy type and Fe-Ni base alloy type are analyzed, then the selecting principle for welding consumables is proposed. Furthermore welding process experiments are undertaken using various welding procedures such as SMAW, GTAW, FCAW and SAW. The results indicate that heat input and interpass temperature should be controlled to ensure a sound weld joint. Finally fracture toughness at-196°C of 9Ni steel and its joint is studied using CTOD test. In conclusion, 9Ni steel developed by Baosteel has good weldability and can meet the requirements of industrial application.

• Periodical: Materials Science Forum (Volume 941)
• Pages: 516-523
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.941.516
• Online since: December 2018
• Authors: Zhao Xia Qu*, Li Qian Xia, Xiao Jie Wang
• Keywords: 9Ni Steel, CTOD, Weldability, Welding Consumables, Welding Process

References

[1] LI Jianmin, WANG Peizhan, LIU Dongfeng, Investigation on Microstructure and Mechanical Properties of 9Ni Steel for LNG Storage Tank during Service, Journal of Taiyuan University of Technology. (1:2013) 71-75.

[2] YANG Yue-hui, CAI Qing-wu, WU Hui-bin, Effect of quenching, lamellarizing and tempering process on properties of 9Ni steel, TRANSACTIONS OF MATERIALS AND HEAT TREATMENT. 30(3:2009)92-95.

[3] LIU Dong-Feng, YANG Xiu-li, HOU Li-feng, Research and Application of Ultralow Temperature 9Ni Steel for LNG Storage Tank, Journal of Iron and Steel Research. 21(9:2009)1-5.