Microstructure, Composition, and Impact Toughness Across the Fusion Line of High-Strength Bainitic Steel Weldments
- PDF / 6,385,406 Bytes
- 14 Pages / 593.972 x 792 pts Page_size
- 105 Downloads / 247 Views
NTRODUCTION
IN recent years, with the development of microalloying technology and thermomechanical control process, great advances have been made on mechanical properties of steels. High-strength bainitic steel, as a representative example, has an excellent combination of high strength, acceptable toughness, and good resistance to welding cold cracking, which is expected to be applied in the field of pipelines, offshore platforms, and engineering machinery.[1,2] However, their excellent microstructures may be upset by welding that is an essential process during the structural construction, and may lead to the formation of weld defects e.g., local brittle zone. To ensure structural integrity of weldments, optimizing welding process parameters should be conducted through experimental trial and error approach. Whereas, it is indeed a daunting task because many variables, such as welding process, process parameters,
LIANGYUN LAN and XIANGWEI KONG are with the School of Mechanical Engineering and Automation, Northeastern University, Shenyang 110819, China. Contact e-mail: [email protected] ZHIYUAN CHANG, CHUNLIN QIU, and DEWEN ZHAO are with the State Key Laboratory of Rolling Technology and Automation, Northeastern University, Shenyang 110819, China. Manuscript submitted March 18, 2016.
METALLURGICAL AND MATERIALS TRANSACTIONS A
and filler metal, need to be determined for optimum welding system design of steels.[3] For a given welding process and base metal, the heat input, defined as a function of the current, voltage, and welding speed, is the most important factor to influence microstructural evolution and mechanical properties of welded joint. Ion et al.[4] developed two types of HAZ microstructure/hardness diagrams as functions of heat input and peak temperature to predict the microstructural evolution of HAZ in an actual weld. Viano et al.[5] demonstrated that the content of acicular ferrite in the weld metal decreases, acicular ferrite laths become coarser with the increasing heat input, which decreases the hardness as well as Charpy V-notch toughness of weld metal. Moon et al.[6] investigated the effect of heat input on microstructure and mechanical properties in the HAZ of the ferritic–martensitic steel with reduced activation. It was shown that the HAZ toughness deteriorated with the increase in heat input due to the formation of martensite and delta-ferrite. In our previous study, the fracture mode of simulated coarsegrained HAZ changed from quasi-cleavage fracture to complete cleavage fracture with the increasing heat input, which rapidly lowered impact toughness.[7] To obtain quickly some information about weldability of newly designed steels, metallurgists have developed some standard evaluation methods and a series of empirical formula. For example, quite a number of
carbon equivalent equations can be employed to roughly estimate the hardenability of steels based on chemical compositions.[8] The single-pass bead-on-plate test is a convenient way that is often adopted to evaluate the HAZ hardenability beca
Data Loading...
