Effect of Welding Heat Input on the Microstructure and Impact Toughness of HAZ in 420 MPa-Grade Offshore Engineering Steel

In the present work, the effect of the welding heat input on the microstructure, martensite–austenite (M–A) constituents, and impact toughness of the coarse-grained heat-affected zone (CGHAZ) in offshore engineering steel with Ca deoxidation is studied. With the heat input increased from 50 to 100 kJ/cm, the HAZ toughness decreased rapidly, while the measured microhardness decreases steadily. The grain sizes are increased from 52 to 132 μm, and the width of bainite lath increased from 0.4 to 2 μm. The area fraction of lath bainite (LB) decreased, while the area fraction of granular bainite (GB) increased. The average width of M–A constituents grows from 0.3 to 0.6 μm, and the average length grows from from 0.5 to 0.9 μm. Its area fraction is increased from 5.3 to 8.6% and then decreased to 6.1%, and its number density decreased from 0.7 to 0.2 μm−2. The morphologies of M–A constituents change from dot-like to slender and blocky, which are deleterious to impact toughness. The fracture mechanism changes from ductile to quasicleavage and cleavage as the heat input is increased. As the M–A constituents are always found as the cleavage initiation, they should be responsible for the decrease in HAZ toughness when the heat input is above 100 kJ/cm.

[1]  Jian Yang,et al.  The Effect of Ca Content on the Formation Behavior of Inclusions in the Heat Affected Zone of Thick High-Strength Low-Alloy Steel Plates after Large Heat Input Weldings , 2019, Metals.

[2]  K. Ichimiya,et al.  Nucleation Effect of Ca-Oxysulfide Inclusions of Low Carbon Steel in Heat Affected Zone by Welding , 2018, Materials Science Forum.

[3]  G. Miyamoto,et al.  Chemistry and three-dimensional morphology of martensite-austenite constituent in the bainite structure of low-carbon low-alloy steels , 2018 .

[4]  H. Matsuura,et al.  Effects of Zr addition on evolution behavior of inclusions in EH36 shipbuilding steel: from casting to welding , 2018 .

[5]  Sunghak Lee,et al.  Effects of Ni and Mn addition on critical crack tip opening displacement (CTOD) of weld-simulated heat-affected zones of three high-strength low-alloy (HSLA) steels , 2017 .

[6]  Jian Yang,et al.  Effect of Mg Content on the Microstructure and Toughness of Heat-Affected Zone of Steel Plate after High Heat Input Welding , 2016, Metallurgical and Materials Transactions A.

[7]  Gang Huang,et al.  Effect of Cr Content on Microstructure and Impact Toughness in the Simulated Coarse‐Grained Heat‐Affected Zone of High‐Strength Low‐Alloy Steels , 2016 .

[8]  A. Gerlich,et al.  Influence of martensite-austenite (MA) on impact toughness of X80 line pipe steels , 2016 .

[9]  S. Subramanian,et al.  EBSD characterization of secondary microcracks in the heat affected zone of a X100 pipeline steel weld joint , 2015, International Journal of Fracture.

[10]  K. Ishida,et al.  Grain Refinement of Heat Affected Zone in High Heat Input Welding by Liquid Phase Pinning of Oxy-Sulfide , 2015 .

[11]  K. Wu,et al.  Effect of fast cooling on microstructure and toughness of heat affected zone in high strength offshore steel , 2014 .

[12]  E. Østby,et al.  Cleavage Fracture Initiation at M–A Constituents in Intercritically Coarse-Grained Heat-Affected Zone of a HSLA Steel , 2013, Metallurgical and Materials Transactions A.

[13]  L. Du,et al.  Microstructural characteristics and toughness of the simulated coarse grained heat affected zone of high strength low carbon bainitic steel , 2011 .

[14]  Zhenguo Yang,et al.  Effect of Magnesium on the Austenite Grain Growth of the Heat-Affected Zone in Low-Carbon High-Strength Steels , 2011 .

[15]  H. Ohta,et al.  Effects of Ca Addition on Formation Behavior of TiN Particles and HAZ Toughness in Large‑Heat‑Input Welding , 2011 .

[16]  T. N. Baker,et al.  Effect of morphology of martensite–austenite phase on fracture of weld heat affected zone in vanadium and niobium microalloyed steels , 2010 .

[17]  G. Thewlis,et al.  Overview Inclusion assisted microstructure control in C–Mn and low alloy steel welds , 2005 .

[18]  Shinichi Suzuki,et al.  High tensile strength steel plates with excellent HAZ toughness for shipbuilding: JFE EWEL technology for excellent quality in HAZ of high heat inputwelded joints , 2005 .

[19]  D. Kaplan,et al.  Morphological aspects of martensite–austenite constituents in intercritical and coarse grain heat affected zones of structural steels , 2004 .

[20]  T. Nakashima,et al.  Super High HAZ Toughness Technology with Fine Microstructure Imparted by Fine Particles , 2004 .

[21]  W. Choo,et al.  Effect of Ti Addition on the Potency of MnS for Ferrite Nucleation in C–Mn–V Steels , 2000 .

[22]  T. Gladman,et al.  Grain refinement of steel by oxidic second phase particles , 1999 .

[23]  Julia King,et al.  Cleavage initiation in the intercritically reheated coarse-grained heat-affected zone: Part I. Fractographic evidence , 1994 .

[24]  I. Hrivňák,et al.  Metallographic Investigation of M-A Constituent : Toughness Deterioration and Its Improvement of Weld HAZ with High Heat Inputs in 780 and 980 MPa Class HSLA Steels (Report 2) , 1994 .

[25]  I. Hrivňák,et al.  Toughness Deterioration and Its Improvement of Weld HAZ with High Heat Inputs in 780 and 980MPa Class HSLA Steels(Report 2). Metallographic Investigation of M-A Constituent. , 1994 .

[26]  M. Toyoda,et al.  Role of Stress and Strain Fields in the Vicinity of Local Hard Zones in Fracture Toughness of Weld HAZ , 1992 .

[27]  John G. Speer,et al.  A perspective on the morphology of bainite , 1990 .

[28]  Takao Araki,et al.  Micro-fracture behaviour induced by M-A constituent (Island Martensite) in simulated welding heat affected zone of HT80 high strength low alloyed steel , 1984 .

[29]  V. Bišs,et al.  Martensite and retained austenite in hot-rolled, low-carbon bainitic steels , 1971 .