Understanding the role of cerium during VIM refining of nickel-chromium and nickel-iron alloys

Li, D.; Cosandey, F.; Maurer, G. E.; Foote, R.; Tien, J. K.

doi:10.1007/bf02650018

Cited by 26 publications

(8 citation statements)

References 11 publications

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“…The Al-Ce complex deoxidation of molten iron was examined by Dan and Gunji, 15) who found that Al-Ce addi-tion decreased the oxygen removal rate and increased the oxygen content compared to Al single deoxidation practice. These were believed to originate from the higher density of 17) reported that the oxygen and sulfur content was effectively reduced by addition of Ce in the Nibase alloys (80wt%Ni-20wt%Cr and 43wt%Ni-35wt%Fe-13wt%Cr-3wt%Ti-0.25wt%Al) through the formation of Ce oxides, sulfides and oxysulfides. They proposed that oxygen and sulfur removal was followed by the first order kinetics and that excessive addition of Ce was deleterious to hot shortness.…”

Section: Introductionmentioning

confidence: 99%

Influence of Refractory-Steel Interfacial Reaction on the Formation Behavior of Inclusions in Ce-containing Stainless Steel

Kwon

Park

2015

ISIJ Int.

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Effect of Ce addition on the interfacial reaction between alumina refractory and 25wt%Cr-20wt%Ni-4wt%Si-0.5wt%Mn stainless steel deoxidized by Al at 1 873 K was investigated to understand the contribution of the refractory-steel reaction to the inclusion evolution processes. The oxygen content markedly decreased by Al deoxidation, followed by a sluggish decrease by Ce addition greater than 0.5 wt%. The Ce content continuously decreased, but the higher the initial Ce content, the lower the Ce-decreasing rate was obtained. The content of Al initially decreased due to the formation of Al-rich inclusions, followed by an abrupt increase mainly due to a reduction of alumina refractory by Ce at the steel-refractory interface. The content of Al decreased again because of the formation of CeAlO 3 compound not only as inclusions but also as refractory-steel reaction products. The CeAl 11 O 18 and CeAlO 3 were formed at the refractory side, while the Ce 2 O 3 and CeAlO 3 were formed at the steel side in the 0.5 wt% and 1.0 wt% Ce added systems. From the refractory-steel reaction mechanism, the process of inclusion evolution was proposed to three steps as follows. The initial SiO 2 -rich oxides are reduced by Al, resulting in the formation of aluminosilicates inclusions (Step 1). The Al 2 O 3 in the inclusions are reduced by cerium, resulting in the formation of Ce-rich oxides (Step 2). Because the Ce content continuously decreased due to the refractory-steel reaction, the inclusions transform from Ce-Al complex oxides to Al-rich aluminosilicates and from Ce 2 O 3 to Ce-Al complex oxides in the 0.1 wt% and 0.5 wt% Ce added systems (Step 3).

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Section: Introductionmentioning

confidence: 99%

Influence of Refractory-Steel Interfacial Reaction on the Formation Behavior of Inclusions in Ce-containing Stainless Steel

Kwon

Park

2015

ISIJ Int.

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“…The reason for the increase of the small size cluster might due to the reoxidation as the oxygen content increases in PT12 sample. Removal of Ce clusters by floatation will be difficult owing to their relatively high density (pCe2O3~0.007 g/mm 3 ). It is reported 3) that Ce oxides easily accumulate on the crucible walls and crucible bottoms instead of flotation, which might be a reason for clogging.…”

Section: Average Size and Size Distribution Of Clustersmentioning

confidence: 99%

“…Removal of Ce clusters by floatation will be difficult owing to their relatively high density (pCe2O3~0.007 g/mm 3 ). It is reported 3) that Ce oxides easily accumulate on the crucible walls and crucible bottoms instead of flotation, which might be a reason for clogging. The number of big size clusters has decreased extremely much in PT12 sample, which implies that the big size clusters more easily adhere to the nozzle wall or the refractory than the small size clusters.…”

Section: Average Size and Size Distribution Of Clustersmentioning

confidence: 99%

“…It is reported that the rare earth metals (REM) can modify the shape of sulfide inclusions and improve the hot workability of steel. 1) Further studies [2][3][4][5][6] reported that rare earth metals reduce the degree of undercooling for nucleation, refine the as-cast structure, and limit solidification segregation in steels. However, the addition of a mischmetal to liquid steel often leads to formation of REM clusters and nozzle clogging, [7][8][9] which is a serious problem during continuous casting in the steel industry.…”

Section: Introductionmentioning

confidence: 99%

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Three Dimensional Evaluations of REM Clusters in Stainless Steel

Karasev

Jönsson

2014

ISIJ Int.

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It is known that clusters in liquid steel have a harmful effect on the casting process and the quality of the final steel product. In this study, clusters of rare earth metals (REM) were investigated in steel samples of a S30185 stainless steel grade from a pilot trial (PT, 250 kg) and from an industrial heat (IH, 100 t). Samples were taken from the liquid steel at different holding times after the addition of mischmetal. Thereafter, REM clusters collected on film filters after electrolytic extraction and filtration were investigated in three dimensions (3D) by SEM in combination with EDS. The morphology, composition, number and size of clusters in PT and IH steel samples were analyzed and compared as a function of holding time. It was found that typical clusters with regular and irregular inclusions were the main type of clusters (69%-98%) in all PT and IH steel samples. The composition of inclusions in clusters corresponded mostly to REM-oxides. The size of clusters that were observed in different samples varied mainly from 2 to 23 μm. In addition, the size and number of most clusters in PT are larger than those in IH samples. Furthermore, the formation mechanisms and evolution of different type of REM clusters were discussed in both PT and IH heats.

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“…Rare earths are among the strongest oxide and sulfide formers, based on their free energies of formation [94]. They also have low vapor pressures which should make them easier to control in vacuum melting than Mg or Ca [95].…”

Section: Rare Earthsmentioning

confidence: 99%

Review of Trace Element Effects on High-Temperature Fracture of Fe- and Ni-Base Alloys

George¹,

Kennedy²,

Pope³

1998

phys. stat. sol. (a)

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Trace elements can have harmful or beneficial effects on elevated‐temperature mechanical properties. In iron and low‐alloy steels, S at high concentrations forms sulfides which are potent nucleation sites for intergranular creep cavities. As a result, ductility decreases and fracture becomes increasingly intergranular with increasing S concentration. Oxides and nitrides nucleate cavities only in the presence of segregated S; by themselves they are relatively benign. The harmful effects of S can be ameliorated by the addition of carbon and phosphorus. It is unclear whether C and P have beneficial effects of their own, or whether they act merely by counteracting the negative effects of sulfur. Carbides almost never nucleate cavities. In Ni‐base alloys, too, S is deleterious, and alloying with strong sulfide getters increases ductility and rupture life. Boron and P interact synergistically and increase stress rupture lives in some alloys but not in others. The detailed mechanism of this interaction is not well understood.

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Understanding the role of cerium during VIM refining of nickel-chromium and nickel-iron alloys

Cited by 26 publications

References 11 publications

Influence of Refractory-Steel Interfacial Reaction on the Formation Behavior of Inclusions in Ce-containing Stainless Steel

Influence of Refractory-Steel Interfacial Reaction on the Formation Behavior of Inclusions in Ce-containing Stainless Steel

Three Dimensional Evaluations of REM Clusters in Stainless Steel

Review of Trace Element Effects on High-Temperature Fracture of Fe- and Ni-Base Alloys

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