Effect of single pass welding heat input on microstructure and hardness of submerged arc welded high strength low carbon bainitic steel

Abstract

The bead on plate test method was employed to investigate the effect of single pass welding heat input on microstructure and hardness of submerged arc welded high strength bainitic steel. The weld metal microstructure contains very high volume fraction of acicular ferrite regardless of heat input. By contrast, with the increase in heat input, the main microstructure in coarse grained heat affected zone (HAZ) changes from a mixture of lath martensite and ferrite sideplate to full ferrite sideplate. Microhardness measurement showed that maximum hardness values always present at the coarse grained HAZ under lower heat input condition, which indicates that the minimum heat input of experimental steel should be higher than 0?92 kJ mm 21 to avoid the formation of welding cold crack. The size distributions of complex inclusions in the weld metal are very similar for all heat inputs mainly because the short residence time does not make the inclusion grow rapidly.

Effect of Heat Input on the Microstructure and Mechanical Properties of Low Alloy Ultra‐High Strength Structural Steel Welded Joint

“…It is generally recognized that acicular ferrite results from multiple hard impingement of different transformation products nucleating on intragranular inclusions at reconstructive and displacive transformation temperatures. The refinement of acicular ferrite depends on the nature of the transformation products …”

Challenges and developments in pipeline weldability and mechanical properties

“…This problem also exists in grade X80 but can be easily managed. Production experience available today is not sufficient to permit an 11 Mean chemical composition and distribution of impact energy values for SAW longitudinal seam WM for X80 pipe 26 Liu and Bhole Pipeline weldability and mechanical properties Science and Technology of Welding and Joining 2013 VOL 18 NO 2 assessment of the softening that occurs in the BM beside the weld. To advice this aspect, the X120 pipe steel contains some amount of V for its precipitation hardening effect.…”

“…2,11,28,44 It is easy to form coarse grain microstructure and MA constituent in HAZ after such ultrahigh heat input welding. Since grain coarsening and the MA constituent present in HAZ structure are the main reasons for toughness deterioration in the weld area, a fine microstructure and reduced formation of MA will lead to improve the HAZ toughness in X70 and X80 pipes.…”

Efeito da Velocidade de Soldagem nas Características Geométricas e Microestruturais de Soldas por Arco Submerso em Tandem Arc

“…Destaca-se o alto grau de refino da estrutura, composta de feixes de carbetos alongados de dimensões nanométricas e altamente dispersos na matriz ferrítica, conforme indicado na imagem de microscopia contida na Figura 11 e os respectivos aumentos em imagens de MEV [19][20][21]. Conforme reportado em Sirin et al [22] e Lan et al [23], aportes térmicos elevados provocam maior crescimento de grão, pois acréscimos na entrada de calor reduzem as taxas de resfriamento de maneira potencialmente excessiva, comprometendo a resistência mecânica da junta por aumentarem as dimensões da ZTA e da região de grãos grosseiros.…”

“…A microestrutura presente na zona fundida das juntas obtidas é composta majoritariamente de morfologias de ferrita, em especial a ferrita acicular (AF), ferrita primária de contorno de grão (PF(G)) e ferrita com segunda fase alinhada (FSA). As micrografias de menor magnificação apresentam o perfil colunar de crescimento característico de ZFs de aços carbono e aços baixa liga [1, 18,23]. As microestruturas características da ZF de cada cordão estão dispostas na Figura 12.…”