Jang A.Y.,Dong - A University |
Lee D.J.,Dong - A University |
Lee S.H.,Dong - A University |
Shim J.H.,ESAB SeAH Corporation |
And 2 more authors.
Materials and Design | Year: 2011
The ductility-dip cracking (DDC) susceptibility of AISI 316L stainless steel weld metals was examined. Modified flux cored arc welding (FCAW) filler wires were fabricated with various chromium and nickel contents. The solidification mode and delta-ferrite content were determined from the chromium and nickel equivalent ratios (Creq/Nieq). Ductility-dip cracking occurred through a grain boundary sliding mechanism in the reheated region of the weld metal in the ferrite at cell and dendrite boundaries (AF mode), and the primary course of DDC formation was associated with the straight migrated grain boundary (MGB) morphology. No DDC was observed in the tortuous MGB due to the pinning effect of delta-ferrite in the continuous network of vermicular type of ferrite (FA mode)/acicular ferrite and continuous austenite network (F mode) weld metals. The DDC at the triple point or the intersection of the MGB showed a creep-like morphology. Severe localized and thermal plastic deformation was observed through the formation of micro-voids when grain boundary sliding was generated in the ductility-dip temperature range under strong restraint conditions. © 2010.
Im H.-D.,ESAB SeAH Corporation |
Kil W.,ESAB SeAH Corporation |
Shin K.,Changwon National University |
Koo B.-H.,Changwon National University
Journal of Korean Institute of Metals and Materials | Year: 2013
This study investigated the effect of heat input in overlay welding using stainless steel FCW on the dilution ratio and characteristics of microstructural evolution, initiation and propagation of a bending crack in the overlay weldment. When the heat input was varied in the range of 3.2-19.8 kJ/cm by adjusting welding parameters such as current, voltage and speed, the dilution ratio was the highest in 7.99.9 kJ/cm with the lowest values of Cr eqand Nieq, for which the formation of martensite was predicted by the Schaeffler diagram, and its existence was confirmed by optical microscopy. In addition, the width of the transition zone was the largest in heat input of 7.9-9.9 kJ/ cm, and martensite was observed in the transition zone of the first weld layer of E309LT1-1 (welding material) and ASTM A516 Gr.70 (base metal). According to the bending test, cracks were observed in the specimens with heat input of 8.6-9.5 kJ/cm. © The Korean Institute of Metals and Materials.
Bang K.-S.,Pukyong National University |
Kil W.,ESAB SeAH Corporation |
Chang W.-S.,Korea Advanced Institute of Science and Technology
Metals and Materials International | Year: 2013
In this study the effects of alloying elements on the microstructure and mechanical properties of 600MPa grade FCAW-S weld metals containing 2% Ni were examined. Carbon, manganese and aluminum contents were varied in the ranges of 0.075%-0.101%, 1.19%-1.69%, and 0.66%-1.49% respectively. Regardless of the Al content, all of the weld metals showed a bainite dominant microstructure with no δ-ferrite. This indicates that when a weld metal contains 2% Ni, the Al content can be increased up to around 1.5% without concern about the deterioration of impact toughness due to the presence of δ-ferrite. The tensile strength of the weld metals varied from 595 MPa to 702 MPa dependent upon the chemical composition. Multiple regression analysis showed that while C and Mn have strong influences on the tensile strength, Al has little influence. Therefore, the Pcm index of weld metals could be used as an indication of their tensile strength. Impact toughness of the weld metals was influenced most by tensile strength and showed that the 50J transition temperature increased by 36 C when the tensile strength was increased by around 100 MPa. Therefore, an excessive increase of the tensile strength should be avoided to attain higher impact toughness. Even when inclusion mean diameters were increased from 0.588 μm to 0.708 μm with an increase of the Al content from 0.66% to 1.49%, the size difference showed little influence on the impact toughness of the weld metals in this experiment. © 2013 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.
Bae S.H.,Dong - A University |
Lim H.D.,ESAB SeAH Corporation |
Jung W.J.,ESAB SeAH Corporation |
Gil W.,ESAB SeAH Corporation |
And 5 more authors.
Journal of Korean Institute of Metals and Materials | Year: 2012
This study investigated changes in phase fraction caused by the addition of Mo, as well as the subsequent behaviour of N and its effect on the mechanical properties of welded 24Cr-N duplex stainless steel weld metals. Filler metal was produced by fixing the contents of Cr, Ni, N, and Mn while adjusting the Mo content to 1.4, 2.5, 3.5 wt%. The delta ferrite fraction increased as the Mo content increased. In contrast, the γ fraction decreased and changed from a round to an acicular shape. Secondary austenite (γ) was observed in all specimens in a refined form, but it decreased as the Mo content increased to the extent that it was nearly impossible to find any secondary austenite at 3.5 wt% Mo. Both tensile and yield strengths increased with the addition of Mo. In contrast, the highest value of ductility was observed at 1.41 wt% Mo. At all temperatures, impact energy absorption showed the lowest value at 3.5 wt% Mo, at which the amount of δ-ferrite was greatest. There was no significant temperature dependence of the impact energy absorption values for any of the specimens. As the fraction of γ phase decreased, the amount of N stacked in the γ phase increased. Consequently, the stacking fault energy decreased, while the hardness of γ increased. © 2012 The Korean Institute of Metals and Materials.