Improved Utilization of Added B in 9Cr Heat-Resistant Steels Containing W

Horiuchi, Toshiaki; Igarashi, Masaaki; Abe, Fujio

doi:10.2355/isijinternational.42.suppl_s67

Cited by 131 publications

(93 citation statements)

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“…The M 2 B phase was observed in the as cast condition of Steel A and in the as rolled condition in Steel B. However, contrary to the thermodynamic prediction which indicates that the M 2 B phase is stable until 1533 K (1260°C) in Steel A and 1540 K (1267°C) in Steel B, most of the M 2 B phase was found to dissolve after normalising at 1423 K (1150°C) in the two steels, which is consistent with the results reported by Horiuchi et al [16]. BN particles were not observed in the as-cast condition of Steel A whilst BN particles were observed in the as-rolled condition of Steel B.…”

Section: Identification Of Boron Nitride and M 2 Bcontrasting

confidence: 43%

Microstructural Evolution of Boron Nitride Particles in Advanced 9Cr Power Plant Steels

MacLachlan

Jepson

et al. 2013

Metall Mater Trans A

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Section: Identification Of Boron Nitride and M 2 Bcontrasting

confidence: 43%

Microstructural Evolution of Boron Nitride Particles in Advanced 9Cr Power Plant Steels

MacLachlan

Jepson

et al. 2013

Metall Mater Trans A

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“…Estos bordes se pueden clasificar según el ángulo girado de planos contiguos de una misma fase. Ángu-los mayores a los 15° representan bordes de alto ángulo [24] (HAGB -líneas negras en los mapas de bordes, Figuras 6b y 7b), en este caso atribuidos a bordes de grano austenítico primario y de placas de martensita, son de alta energía y nuclean por lo general el colapso de la estructura [4]. Ángulos mayores a 2° y menores a 15° se consideran de bajo ángulo o borde de subgrano [24] (LAGB-líneas claras en los mapas de bordes, Figuras 6b y 7b) son de baja energía y se los relaciona con la densidad de dislocaciones presentes en la microestructura [25].…”

Section: Microscopia Electrónica De Barrido (Sem) Y Análisis De Difraunclassified

“…Ángulos mayores a 2° y menores a 15° se consideran de bajo ángulo o borde de subgrano [24] (LAGB-líneas claras en los mapas de bordes, Figuras 6b y 7b) son de baja energía y se los relaciona con la densidad de dislocaciones presentes en la microestructura [25]. Es bien conocido que las dislocaciones son sitios de nucleación de precipitados MX y que estos últimos impiden su movimiento durante la degradación [2][3][4].…”

Section: Microscopia Electrónica De Barrido (Sem) Y Análisis De Difraunclassified

“…Para un rango de funcionamiento a temperaturas de 625-650º C y presiones de 30-35 MPa, se requiere la utilización de aceros resistentes al creep. Variaciones en la composición química de los aceros 9Cr permitieron elevar su resistencia mediante el agregado de W a expensas de una reducción en el contenido de Mo y adiciones de B [1] logrando de esta forma disminuir la degradación de la microestructura, reflejada en una disminución de la velocidad mínima de creep y un aumento del tiempo a la rotura [2][3][4]. Dado que los equipos donde se emplean estos materiales son de construcción soldada, la soldabilidad de estos materiales es relevante y el desarrollo del metal de aporte para su unión presenta los mismos desafíos que el metal base.…”

Section: Introductionunclassified

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Tratamiento térmico alternativo para el metal de soldadura de un acero 9Cr

Burgos

Rodrı́guez²,

Svoboda

et al. 2018

Matéria (Rio J.)

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“…4) About 0.003% boron and 0.06 % nitrogen are added to these steels as alloying elements. Several mechanisms of creep strengthening in these heat resistant steels [5][6][7][8] have been reported. For instance, nitrogen forms super fine nitrides with vanadium and niobium, and boron has the suppressing effects for the coarsening of carbides and the Laves phases that precipitate near the grain bounders.…”

Section: Introductionmentioning

confidence: 99%

Influence of Heat Treatment on Formation Behavior of Boron Nitride Inclusions in P122 Heat Resistant Steel

2006

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a cast structure or a forged and rolled structure, by assuming the same heat treatment condition and also by the appearance of the d-phase. As previously reported, 9) even the low C-9Cr-3Co-3W-V, Nb-N-B steel 18) showed the same formation behavior under the same heat treatment condition and the same contents of boron and nitrogen as the ones in this study. In other words, the formation of boron nitride inclusions is assumed to be affected mainly by the added contents of boron and nitrogen and the condition of heat treatments, and is hardly influenced by the steel structure. The Methods to Avoid the Formation of CoarseSize Boron Nitride Inclusions Boron and nitrogen that would help improve the creep strength of newly developed high Cr heat resistant steels would not perform efficiently if a large number of coarse boron nitride inclusions form. The growth of boron nitride inclusions of 20 to 30 mm are assumed to have undesirable influences on the mechanical properties of steel such as fatigue, thermal fatigue and impact. Therefore, the cooling rates after the hot working process should be controlled to avoid the formation of these inclusions. They can be avoided by adapting fast cooling rates or by controlling the heat treatments of normalizing or tempering to relatively thin and small size products such as heat exchange tubes.However, it will be difficult to employ fast cooling rates to thick and large size products such as main steam pipes that are produced from several ton steel ingots. The amount of boron and nitrogen concentrations which do not form boron nitride inclusions and the minimum adequate nitrogen contents that is needed to precipitate vanadium and niobium nitrides will have to be determined. Figure 12 shows the relation between boron and nitrogen in high Cr heat resistant steels that is necessary to form coarse size boron nitride inclusions 9) and the limits of boron and nitrogen concentrations in P122 and P92 steels by the ASME code.3) As shown in Fig. 12, boron and nitrogen concentrations are include in the area of boron nitride formation for both P122 and P92 steels. Therefore, we should try to obtain the boron and nitrogen concentration limit at the left side of the plot and the lowest point in the concentration limit area, to avoid the formation of coarse size boron nitride inclusions as much as possible. ConclusionsThe influences of remelting, forging, rolling and heat treatment on the boron nitride inclusion that were formed in P122 heat resistant steel containing 0.003 mass% boron and 0.06 mass% nitrogen were investigated by the SEM observation of the fractured surface. The following conclusions were drawn from this investigation.(1) The temperature where the boron nitride inclusion formation in P122 steel begins is between 1 150 to 1 200°C.(2) After forging and rolling, boron nitride inclusions form agglomerated groups of 20 to 30 mm during very slow cooling or of 10 to 20 mm during medium slow cooling.(3) Re-dissolution of boron nitride inclusions into the steel matrix begins above 1 200°...

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Improved Utilization of Added B in 9Cr Heat-Resistant Steels Containing W

Cited by 131 publications

References 0 publications

Microstructural Evolution of Boron Nitride Particles in Advanced 9Cr Power Plant Steels

Microstructural Evolution of Boron Nitride Particles in Advanced 9Cr Power Plant Steels

Tratamiento térmico alternativo para el metal de soldadura de un acero 9Cr

Influence of Heat Treatment on Formation Behavior of Boron Nitride Inclusions in P122 Heat Resistant Steel

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