Structure, Microsegregation, and Precipitates of an Alloy 690 ESR Ingot in Industrial Scale

Wang, Min; Zha, Xiangdong; Gao, Ming; Ma, Yunyun; Liu, Kui; Li, Yiyi

doi:10.1007/s11661-015-3099-6

Cited by 15 publications

(6 citation statements)

References 39 publications

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“…As a consequence, the ingot center had the least amount of N in the matrix. According to the results of a previous work [14], the volume fraction of P-nitrides in the central area was below 0.03 vol% (within the fields containing several dendrites); consequently, the nitrogen remaining in the matrix would be no less than 0.005 wt%. The temperature employed in this calculation was 1300°C, the highest exposing temperature in this work.…”

Section: Thermodynamic Inevitability Of the Secondary Precipitationmentioning

confidence: 75%

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Secondary Precipitation Behavior of Nitride in the Electro-slag Remelted Structure of Alloy 690

Wang

Chen

Hao

et al. 2017

Acta Metall. Sin. (Engl. Lett.)

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The precipitation and evolution of secondary nitrides (S-nitrides) in the Alloy 690 electro-slag remelted (ESR) structure were investigated. Experimental results indicate that S-nitrides precipitated in the interdendritic region of the ESR structure at temperatures higher than 1100°C. S-nitrides could spread throughout the entire interdendritic area after sufficient exposure, and they were more numerous and much finer than primary nitrides. Furthermore, after studying the evolution of S-nitride particles at 1100, 1200 and 1300°C, it was determined that the precipitation of S-nitrides was controlled by the diffusion of nitrogen. In addition, by investigating the elemental segregation of ESR structure and calculating critical Ti concentrations, S-nitride precipitation was found to be thermodynamically inevitable in the Alloy 690 ESR structure.

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Section: Thermodynamic Inevitability Of the Secondary Precipitationmentioning

confidence: 75%

“…The manufacture and dissection of the large Alloy 690 ESR ingot have been presented elsewhere [14]. This ingot was produced by a double-route process involving VIM and ESR, and it was 1800 mm in height, 515 mm in diameter and 3 tons in weight.…”

Section: Methodsmentioning

confidence: 99%

Secondary Precipitation Behavior of Nitride in the Electro-slag Remelted Structure of Alloy 690

Wang

Chen

Hao

et al. 2017

Acta Metall. Sin. (Engl. Lett.)

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“…Columnar grains grew parallel to the direction of heat flow. 21) When the gas pressure was 0.1, 0.8 and 1.2 MPa, at the ingot center, the angle of grains with respect to the vertical axis was 36°, 45° and 40°, respectively. A larger angle implies a deeper metal pool.…”

Section: Methodsmentioning

confidence: 95%

Effects of Nitrogen Gas Pressure on the Solidification Parameters and As-cast Microstructure Revolution during Pressurized Electroslag Remelting AISI 304 Stainless Steel

Liu

et al. 2020

ISIJ Int.

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“…To evaluate the effect of ESR on the homogeneity of the steel alloy contents, i.e., micro-segregation, in the case of the present steels, the distributions of Cr, W, Mo, Ni, Mn, V, and Si were measured using EPMA. To determine the degree of elemental segregation, the nominal segregation index (ζi) [37,38] was calculated using the following equation, and the results are given in Table 6:…”

Section: Effect Of Esr On Micro-segregationmentioning

confidence: 99%

The Effect of Electroslag Remelting on the Microstructure and Mechanical Properties of CrNiMoWMnV Ultrahigh-Strength Steels

Ali

Porter

Kömi

et al. 2020

Metals

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The effect of electroslag remelting (ESR) with CaF 2 -based synthetic slag on the microstructure and mechanical properties of three as-quenched martensitic/martensitic-bainitic ultrahigh-strength steels with tensile strengths in the range of 1250-2000 MPa was investigated. Ingots were produced both without ESR, using induction furnace melting and casting, and with subsequent ESR. The cast ingots were forged at temperatures between 1100 and 950 • C and air cooled. Final microstructures were investigated using laser scanning confocal microscopy, field emission scanning electron microscopy, electron backscatter diffraction, electron probe microanalysis, X-ray diffraction, color etching, and micro-hardness measurements. Mechanical properties were investigated through measurement of hardness, tensile properties and Charpy-V impact toughness. The microstructures of the investigated steels were mainly auto-tempered martensite in addition to small fractions of retained austenite and bainite. Due to the consequences of subtle modifications in chemical composition, ESR had a considerable impact on the final microstructural features: Prior austenite grain, effective martensite grain, and lath sizes were refined by up to 52%, 38%, and 28%, respectively. Moreover, the 95th percentiles in the cumulative size distribution of the precipitates decreased by up to 18%. However, ESR had little, if any, the effect on microsegregation. The variable effects of ESR on mechanical properties and how they depend on the initial steel composition are discussed.The prior austenite grains are divided into packets, which consist of blocks of laths with the same habit plane. These blocks contain sub-blocks in which the laths have similar crystal orientations. The boundaries between packets and blocks have high-angle misorientations while the boundaries between sub-blocks and laths have low-angle misorientations [8][9][10].Strength and toughness properties can be improved simultaneously by grain refining, which can be achieved, for example, by the pinning of the austenite grain boundaries by fine precipitates, which are stable at high temperatures [11]. A high number density of fine precipitates leads to enhanced pinning of the grain boundaries, which subsequently leads to a reduction of the final prior austenite grain, packet, and block sizes and a significant effect on the mechanical properties of the steel. It was observed by Wang et al. [12] that the yield strength of 17CrNiMo6 martensitic steel is increased by 235 MPa by reducing the prior austenite grain size (PAGS) by 33% and the Charpy U-notch impact energy at 77 K was enhanced more than eight-fold.In addition to the above strengthening factors, additional strengthening can be achieved through precipitation. In the case of dislocation bowing between precipitates, the Orowan relationship [13] shows that the yield strength increment from precipitation increases with increasing volume fraction and decreasing size of the precipitates. In the case of tempered martensite, the optimum combinati...

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Structure, Microsegregation, and Precipitates of an Alloy 690 ESR Ingot in Industrial Scale

Cited by 15 publications

References 39 publications

Secondary Precipitation Behavior of Nitride in the Electro-slag Remelted Structure of Alloy 690

Secondary Precipitation Behavior of Nitride in the Electro-slag Remelted Structure of Alloy 690

Effects of Nitrogen Gas Pressure on the Solidification Parameters and As-cast Microstructure Revolution during Pressurized Electroslag Remelting AISI 304 Stainless Steel

The Effect of Electroslag Remelting on the Microstructure and Mechanical Properties of CrNiMoWMnV Ultrahigh-Strength Steels

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