Importance of filler material chemistry for optimising weld metal mechanical properties in modified 9Cr–1Mo steel
01 Aug 2001-Science and Technology of Welding and Joining (Taylor & Francis)-Vol. 6, Iss: 4, pp 247-254
TL;DR: In this paper, the weld fusion zones were metallographically examined in detail and hardness, tensile properties, and toughness were estimated, and the weld metal produced from one of the two electrodes was distinctly superior in terms of ductility and toughness for any given welded or heat treated condition.
Abstract: Although modified 9Cr–1Mo (grade 91) steel is considered weldable using conventional procedures, the attainment of optimum weld metal properties often causes concern. In the current work, plates of grade 91 were manual metal arc welded using electrodes with slightly different compositions provided by two manufacturers. Post-weld tempering was performed at 730 and 760°C for 2 and 6 h in each case. The weld fusion zones were metallographically examined in detail and hardness, tensile properties, and toughness were estimated. The results showed that the weld metal produced from one of the two electrodes was distinctly superior in terms of ductility and toughness for any given welded or heat treated condition. This was attributed to the slightly higher silicon, niobium, and chromium contents in the inferior electrode, which resulted in both retention of some high temperature ferrite and a greater degree of precipitation. In this electrode, additionally, the alloying elements were introduced through th...
Citations
More filters
TL;DR: In this article, microstructure evolution in P91 steel and their weldments are reviewed in as-virgin and heat treatment and creep exposure condition, and the role of grain coarsening, Cr/Fe ratio, lath widening and dislocation density on creep rupture life of base metal and weldments is discussed.
155 citations
TL;DR: In this article, a new class of ferritic alloys, known as creep strength enhanced ferritic steels, has been developed to meet the requirements of increasing the efficiency and reducing the carbon footprint of new and existing fossil fired power plants.
Abstract: Fossil fuels continue to be the primary source of energy in the world. The worldwide demand for clean and affordable energy will continue to grow, and a strong emphasis has been placed on increasing the efficiency and reducing the carbon footprint of new and existing fossil fired power plants. Throughout Asia, Europe and the USA, this demand is being met with programmes to develop advanced materials that have enhanced high temperature creep and corrosion properties. A new class of ferritic alloys, known as creep strength enhanced ferritic steels, has been developed to meet these requirements. This article focuses on the weldability of the advanced ferritic alloys used in boilers and boiler components of ultrasupercritical coal fired power plants. This review focuses on alloy selection; welding and weldability issues, including in service weld failure such as type IV cracking; welding of dissimilar metals; and weld repair. Future articles will address the welding and weldability issues of two other...
90 citations
17 Jan 2018-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the microstructure evolution in sub-zones and mechanical properties of dissimilar welded joints were studied in as-welded and post weld heat treatment (PWHT) condition.
Abstract: Creep strength enhanced ferritic/martensitic 9Cr-1Mo-V-Nb (P91) steel is also designated as ASTM A335 used for out-of-core and in-core (piping, cladding, ducts, wrappers, and pressure vessel) of Gen IV reactors. In present investigation, the dissimilar weld joint of P91 and P92 steel were made using the autogenous tungsten inert gas (TIG) welding with single pass, double side pass and multi-pass gas tungsten arc (GTA) welding with filler wire. Microstructure evolution in sub-zones and mechanical properties of dissimilar welded joints were studied in as-welded and post weld heat treatment (PWHT) condition. Formation of δ-ferrite patches in weld fusion zone and heat affected zones (HAZs) and their influence on the mechanical behaviour of the welded joints were also studied. Presence of higher content of ferrite stabilizer in P92 steel have resulted the formation of δ-ferrite patches in weld fusion zone as well as HAZs. The δ-ferrite was observed in autogenous TIG welds joints. The δ-ferrite patches were formed in as-welded condition and remained in the microstructure after the PWHT. The δ-ferrite patches leads to reduction in Charpy toughness of autogenous TIG welds joint and also lower down the average hardness of weld fusion zone. Peak hardness and poor impact toughness were observed for autogenous TIG welds joint as compared to GTA welds. For microstructure characterization, field-emission scanning electron microscope (FESEM) with energy dispersive spectroscopy (EDS) and optical microscope were utilized.
55 citations
TL;DR: In this paper, the evolution of δ-ferrite patches in weld fusion zone and heat affected zone (HAZ) of welded joints was performed in as-welded and postweld heat treatment (PWHT) condition.
52 citations
TL;DR: In this article, the microstructural and microchemical variations in a multipass Gas Tungsten Arc weld (GTAW) of modified 9Cr-1Mo steel are described.
Abstract: This paper presents the results of a study on the microstructural and microchemical variations in a multipass Gas Tungsten Arc weld (GTAW) of modified 9Cr-1Mo steel. The changes brought about in the steel due to the heating and cooling cycles during welding and the subsequent effects due to reheating effects during multipass welding are described. Detailed analytical transmission electron microscopy has been carried to study the type and composition of the primary and secondary phases in this steel. The systematic changes in microstructural parameters such as Prior Austenite Grain Size, martensite lath size, number density, size and microchemistry of carbides, have been understood based on the different transformations that the steel undergoes during the heating and cooling process. Based on the observed microstructure, an attempt has been made to identify distinct microstructural zones and possible thermal cycles experienced by different regions of the weldment.
35 citations
References
More filters
TL;DR: In this article, the authors investigated the influence of trace amounts of V and Nb on the sequence of precipitation processes and identified the basis for the enhanced high-temperature strength compared to the standard 9Cr-lMo composition.
Abstract: The tempering and subsequent annealing of modified 9Cr-lMo steel have been investigated to determine the influence of trace amounts of V and Nb on the sequence of precipitation processes and to identify the basis for the enhanced high-temperature strength compared to the standard 9Cr-lMo composition. Air cooling (normalizing) from 1045 °C results in the precipitation of fine (Fe, Cr)3C particles within the martensite laths. Additional carbide precipitation and changes in the dislocation structure occur during the tempering of martensite at 700 °C and 760 °C after normalizing. The precipitation of M23C6 carbides occurs preferentially at lath interfaces and dislocations. The formation of Cr2C was detected during the first hour of tempering over the range of 650 °C to 760 °C but was replaced by V4C3 within 1 hour at 760 °C. During prolonged annealing at 550 °C to 650 °C, following tempering, the lath morphology remains relatively stable; partitioning of the laths into subgrains and some carbide coarsening are evident after 400 hours of annealing at 650 °C, but the lath morphology persists. The enhanced martensite lath stability is attributed primarily to the V4C3 precipitates distributed along the lath interfaces and is suggested as the basis for the improved performance of the modified 9Cr-lMo alloy under elevated temperature tensile and creep conditions.
166 citations
TL;DR: A small research program has been performed on a Modified 9% Cr 1% Mo steel (T91-ASTM A213) base material and weldments to establish the most fruitful lines along which a larger project could develop as discussed by the authors.
25 citations
TL;DR: In this paper, the authors describe the Weldability of 9Cr•1Mo•Nb, V P91 steel intended for service in the power industry and show that it can be used in a number of applications.
Abstract: (1996). Weldability of 9Cr‐1Mo‐Nb, V P91 steel intended for service in the power industry. Welding International: Vol. 10, No. 5, pp. 370-380.
14 citations