Abstract
The application of low transformation temperature (LTT) wire can effectively reduce residual stress, without the need for preheating before welding and heat treatment after welding. The mechanism reduces the martensitic transformation temperature, allowing the martensite volume expansion to offset some or all of the heat-shrinking, resulting in reduced residual stress during the welding process. In this paper, commercial ER110S-G welding wire and LTT wire with chemical composition Cr10Ni8MnMoCuTiVB were developed to solve the problem of stress concentration. The microstructure of the LTT joint is mainly composed of martensite and a small amount of residual austenite, while the microstructure of the ER110S-G joint is mainly composed of ferrite and a small amount of granular bainite. The micro-hardness and tensile strength of the LTT joint is higher than that of ER110S-G joint; however, the impact toughness of the LTT joint is not as good as that of the ER110S-G joint. The martensitic phase transformation of LTT starts at 212 °C and finishes at around 50 °C, and the expansion caused by phase transition is about 0.48%, which is much higher than that of the base metal (0.15%) and ER110S-G (0.18%). The residual tensile stress at the weld zone of the ER110S-G joint is 175.5 MPa, while the residual compressive stress at the weld zone of LTT joint is −257.6 MPa.
Highlights
With the characteristics of high strength and excellent weldability, high-strength low-alloy steel is widely used in automobiles, railway vehicles, bridges and other industries [1,2]
The microstructure joints were observed by Leica optical microscope
The microstructure of the low transformation temperature (LTT) joint is mainly composed of martensite and residual austenite, while the microstructure of the ER110S-G joint is mainly composed of a large number of acicular ferrite and a small amount of granular bainite
Summary
With the characteristics of high strength and excellent weldability, high-strength low-alloy steel is widely used in automobiles, railway vehicles, bridges and other industries [1,2]. In the process of welding steel, it is easy to generate large and centralized residual stresses, which may produce stress corrosion cracking and brittle fracture, seriously reduce the anti-fatigue performance, and greatly reduce the service life of the components [3,4,5,6]. The mechanical and heat treatment methods are usually used to reduce or eliminate the welding residual stress. These additional measures inevitably lead to an increase in costs. The application of low transformation temperature (LTT) wire can effectively reduce the residual stress, without the need for preheating before welding and heat treatment after welding [7,8]. The mechanism reduces the martensitic transformation temperature, allowing the martensite volume expansion to offset some or all of the heat-shrinking, resulting in Crystals 2018, 8, 293; doi:10.3390/cryst8070293 www.mdpi.com/journal/crystals
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
