Microstructure and Mechanical Properties of Weld Fusion Zones in Modified 9Cr-1Mo Steel
01 Jun 2001-Journal of Materials Engineering and Performance (Springer US)-Vol. 10, Iss: 3, pp 320-330
TL;DR: In this article, a plate of modified 9Cr-1Mo steel was welded with three different filler materials: standard 9Cr 1Mo, modified 9 Cr 1Mo and nickel-base alloy Inconel 182 post-weld heat treatment (PWHT) for periods of 2 and 6 hours.
Abstract: Modified 9Cr-1Mo steel finds increasing application in power plant construction because of its excellent high-temperature properties While it has been shown to be weldable and resistant to all types of cracking in the weld metal and heat-affected zone (HAZ), the achievement of optimum weld metal properties has often caused concern The design of appropriate welding consumables is important in this regard In the present work, plates of modified 9Cr-1Mo steel were welded with three different filler materials: standard 9Cr-1Mo steel, modified 9Cr-1Mo, and nickel-base alloy Inconel 182 Post-weld heat treatment (PWHT) was carried out at 730 and 760 °C for periods of 2 and 6 h The joints were characterized in detail by metallography Hardness, tensile properties, and Charpy toughness were evaluated Among the three filler materials used, although Inconel 182 resulted in high weld metal toughness, the strength properties were too low Between modified and standard 9Cr-1Mo, the former led to superior hardness and strength in all conditions However, with modified 9Cr-1Mo, fusion zone toughness was low and an acceptable value could be obtained only after PWHT for 6 h at 760 °C The relatively poor toughness was correlated to the occurrence of local regions of untransformed ferrite in the microstructure
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TL;DR: In this paper, the behavior of both the base metal and the weld metal of circumferential weldments performed using a semiautomatic welding process under gas mixture protection was studied and the microstructure was analyzed in different zones: weld metal, heat affected (coarse and fine grain, intercritical and subcritical) and not affected base metal.
Abstract: 9Cr steels are widely used for high temperature service, principally in applications related to energy generation. Lately several variants of these materials have been developed through the addition of B, W and Co, among others. Due to the fact that information on influence of welding procedure on the welded joint is scarce, the objective of this work was to study the behavior of both the base metal and the weld metal of circumferential weldments performed using semiautomatic welding process under gas mixture protection. Two FCAW rutilic slag wires, alloyed with 9Cr1Mo and 9Cr0.5Mo1W1Co respectively, were used under Ar/20%CO2 gas shielding. Post weld heat treatments of 4 and 2 hours have been carried out. The microstructure was analyzed in the different zones: weld metal, heat affected (coarse and fine grain, intercritical and subcritical) and not affected base metal. Chemical composition of the weld metal, transversal tensile properties of the joint and microhardness along the weld transversal section were determined. In all cases it was obtained maximum hardness values in the weld metal and a decrease in this property in the heat affected zone from the coarse grain zone to the base metal one. The minimal hardness values were achieved in the intercritical zone, lower than those of the metal base. Hardness and tensile strength increased when the weldment was performed with the 9Cr0,5Mo1W wire. The shorter heat treatment allowed obtaining higher values of tensile strength, in all the cases. Toughness and creep resistance determinations will be the next step. Key-words: 9Cr steel; Post welding heat treatment; Microstructure; Welded joint; Tubular wire Recebido em 11/12/2013, texto final em 19/02/2014. 1. Introducción Dentro de la familia de aceros ferríticos resistentes al creep (CSEFS-creep strength-enhanced ferritic steel) se encuentran los aceros ASTM 335 Gr P91, ampliamente utilizados en reemplazo de aleaciones tradicionales Cr-Mo. En general, el estado del arte de este tema reporta pocos problemas acerca de su soldabilidad; sin embargo, suelen encontrarse fallas prematuras debido a un mal diseño de la soldadura. Procedimientos incorrectos y tratamientos térmicos inadecuados suelen ser los responsables de estas fallas [1]. Las mayores causas de falla en uniones soldadas de los CSEFS se deben a: • Formación de ferrita delta
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Cites background from "Microstructure and Mechanical Prope..."
...Esta diferencia en la composición química de los alambres se ha traducido en una diferencia en los valores de Cr equivalente (Creq), de manera que en la probeta PMo se superó el valor de 10 que es considerado crítico para la presencia de ferrita delta [9], mientras que en la probeta PMoW el Creq se mantuvo por debajo de este valor....
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TL;DR: In this paper, the microstructural and mechanical properties of the dissimilar weld joint were investigated and it was shown that the weld was comprised of typical tempered martensite microstructure.
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01 Jan 2021
TL;DR: In this paper, the influence of different heat treatment processes which will yield better tensile strength and microstructures of 8mm-thick plates metal inert gas welded IS2062-EN9 joint was investigated.
Abstract: The present investigation, influence of different heat treatment processes which will yield better tensile strength and microstructures of 8-mm-thick plates metal inert gas welded IS2062-EN9 joint. Mechanical properties of the joint increased with annealing heat treatment processes, higher grain size was measured at welded zone, and it decreased. It is found that the joint fabricated at a low heat input condition showing excellent mechanical and metallurgical properties. After annealing heat treatment process, tensile strength improved around 14.52%, the pearlite phase increased from 36.75 to 47.15%, and ferrite phase has decreased from 59.36 to 50.61% and other decreased from 3.88 to 2.24%. The tensile strength is improved due to grain size that was observed to be 7.5 before heat treatment and 9 after annealing heat treatment, and ferrite phase is transformed into pearlite phase.
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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: In this paper, a ternary system composed of a pure iron substrate and a 70Ni-30Cu filler metal was used to determine the nature and evolution of boundaries and structure in dissimilar metal welds.
Abstract: Cracking, or disbonding, along the fusion boundary in dissimilar metal welds has been a persistent problem, particularly in applications where austenitic alloys are clad on to structural steels for corrosion protection. Many failures in dissimilar metal welds occur as a result of cracking along a boundary that runs parallel to the fusion boundary in the adjacent weld metal. A preliminary investigation was undertaken to determine the nature and evolution of boundaries and structure in dissimilar metal welds using a simple ternary system composed of a pure iron substrate and a 70Ni–30Cu (Monel) filler metal. Changes in base metal dilution were found to alter the evolution of boundaries and structures near the fusion boundary dramatically. Optical metallography and electron microanalysis reveal that the resulting weld microstructures and boundaries are similar to those observed in engineering materials used for cladding and corrosion resistant overlay. Transmission electron diffraction analysis revea...
63 citations
TL;DR: In this paper, the authors describe an investigation of the creep rupture strength (CRS) of 9Cr•1Mo•V•Nb•N steel welded joints by welding thermal cycle simulation.
Abstract: Summary This paper describes an investigation of the creep rupture strength (CRS) of 9Cr‐1Mo‐V‐Nb‐N steel welded joints by welding thermal cycle simulation. The reduction in the CRS of the welded joints is successfully reproduced, and the reasons for this reduction are discussed from the perspective of fine precipitates in the matrix. The CRS of the simulated HAZ (heat affected zone) varies with the peak temperature of welding thermal cycle simulation (PT). It falls sharply beyond the Ac1 temperature, gradually reaching the minimum at the Ac3 temperature of 925 °C. At any higher temperature than Ac3, it rises steadily, showing almost the same CRS as the base metal at 1100°C. The weakest CRS of the simulated HAZ lies at the lowest limit of the CRS data band of various welded joints prepared by GTA (TIG), MMA, and submerged‐arc (SA) welding with the same base metal. The simulated HAZ is useful for evaluation and analysis of the CRS reduction of welded joints. Heating to the Ac3 temperature by welding change...
30 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