Morphology Control of Copper Sulfide in Strip Casting of Low Carbon Steel

Liu, Zhongzhu; Kobayashi, Yoshinao; Nagai, Kotobu; Yang, Jian; Kuwabara, Mamoru

doi:10.2355/isijinternational.46.744

Cited by 39 publications

(37 citation statements)

References 32 publications

(48 reference statements)

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“…[1][2][3] However, copper and sulfur in steel may form various copper sulfides with different morphologies. [4][5][6][7] For example, the present authors have reported four kinds of copper sulfide in steel 6) : copper sulfide coexisted with oxide inclusion, plate-like copper sulfide, shell/filmlike copper sulfide and nano-scale copper sulfide. These copper sulfides may have great influences on the microstructure and properties of steel.…”

Section: Introductionmentioning

confidence: 99%

“…In the previous papers, 5,6,8) the authors found that copper sulfides could be formed in strip casting steel. Differently from the formerly reported copper sulfides in steel/ iron, [10][11][12][13][14][15] which usually coexisted with MnS, almost pure copper sulfides with various morphologies were found in the previous strip casting steels.…”

Section: Introductionmentioning

confidence: 99%

“…4,5) The shell/film-like copper sulfide may nucleate the acicular ferrite during gamma/alpha transformation and then refine the microstructure of steel. 7) The shell/filmlike copper sulfide may also improve the corrosion resistance of steel. 9) In addition, copper sulfides, unlike copper, does not wet or penetrate the grain boundaries and therefore may inhibit hot shortness.…”

Section: Introductionmentioning

confidence: 99%

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Isothermal Precipitation Behavior of Copper Sulfide in Ultra Low Carbon Steel

2007

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Copper and sulfur are typical residual elements or impurity elements in steel. Sufficient removal of them during steelmaking process is difficult for copper and costly for sulfur. Utilization of copper and sulfur in steel, especially in steel scrap, has been an important issue for a long period for metallurgists.Copper and sulfur may combine to form a copper sulfide, which may provide a prospect to avoid the detrimental effects of copper and sulfur in steel. Unfortunately the formation mechanism of a copper sulfide in steel has not been completely clarified so far. In the present paper, solution treatment of samples containing copper and sulfur are firstly performed at 1 623 K for 2.7ϫ10 3 s followed by quenching into water. The samples are then isothermally heat-treated at 673 K, 873 K, 1 073 K, 1 273 K and 1 373 K for different time followed by quenching into water again. The size, morphology, constituent and crystallography of sulfide precipitates in these samples are investigated by SEM and TEM equipped with EDS. Fine copper sulfides (less than 100 nm) are observed to co-exist with silicon oxide in samples even isothermally heattreated at 1 373 K for 1.44ϫ10 4 s; Film-like copper sulfides are generally observed to co-exist with iron sulfide in all samples; Plate-like copper sulfides are observed especially in sample isothermally heat-treated at 1 073 K for 1.44ϫ10 4 s. The formation mechanisms of these copper sulfides have been discussed in detail.KEY WORDS: copper sulfide; isothermal precipitation; morphology; crystallography; ultra low carbon steel.up to 780 K at 36.60 at% S and down to 345 K at 35.65 at% S. Therefore, the high Digenite is the most probable phase that is expected in steel at high temperature. But people have confusedly presumed and reported several crystal structures and phases, 11,[13][14][15]20) for example cubic Cu 1.8 S or Cu 1.6 S or CuS 2 , hexagonal CuS and rhombohedral Cu 1.6 S and so on, for copper sulfide in steel.In the previous papers, 5,6,8) the authors found that copper sulfides could be formed in strip casting steel. Differently from the formerly reported copper sulfides in steel/ iron, [10][11][12][13][14][15] which usually coexisted with MnS, almost pure copper sulfides with various morphologies were found in the previous strip casting steels. In the present paper, the formation mechanism such as precipitation temperature, stability and crystallography of various copper sulfides have been investigated during isothermal heat treatment process. Experimental Procedures Materials and Heat Treatment ConditionsThe chemical composition of the present steel is shown in Table 2. The steel is firstly prepared in an induction heating furnace under flowing argon gas. About 350 g of electrolytic iron is melted at 1 873 K. After the alloying elements (Cu, S) are added to the melted iron, the melt is cooled to room temperature with the furnace. An ingot with size of f40ϫH50 mm (hereafter named as sample H00) then could be obtained for the following heat treatment.The solution treatment o...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Isothermal Precipitation Behavior of Copper Sulfide in Ultra Low Carbon Steel

2007

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“…3,4) According to the phase diagram of the Cu-S system, CuS 0.5 is the most probable phase in the temperature range for γ-Fe.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic Properties of the MnS^|^ndash;CuS0.5 Binary System

et al. 2012

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In order to discuss the formation of MnS-CuS0.5 inclusion in γ-Fe, the phase diagram of the MnS-CuS0.5 binary system has been determined by using a confocal scanning laser microscope (CSLM) and a chemical equilibration technique. In addition, the activities of MnS and CuS0.5 in the liquid phase at 1 473 K were investigated by chemical equilibration with molten Cu. The phase diagram of the binary system was found to be of a eutectic type with mutual solid solubility between MnS and CuS0.5. The activities of MnS and CuS0.5 showed positive deviation from the ideality. Finally, the solid steel composition equilibrated with the inclusion was estimated by using the determined thermodynamic properties.

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“…First, this precipitation inevitably occurs even if the concentration of copper in steel is lower than 0.01 mass% which level is almost the same as that for impurity copper in common steel. 10) Second, copper sulfides are classified mainly into three types 11) as follows: 1. Plate-like copper sulfide (PS) 2.…”

Section: Introductionmentioning

confidence: 99%

Growth Rate of Copper Sulfide Precipitates in Solid Low Carbon Steel

et al. 2015

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The kinetics of copper sulfide growth has been investigated using low carbon steel samples such as Fe-0.3mass%Cu-0.03mass%S-0.1mass%C and Fe-0.1mass%Cu-0.01 mass%S-0.1mass%C. The samples were heat-treated at 1 273, 1 423 and 1 573 K for 100 s -14.4 ks for precipitation of copper sulfides and then subjected to observation by a scanning electron microscope (SEM) and a transmission electron microscope (TEM) to measure the size of copper sulfides precipitated in the samples. The growth kinetics of copper sulfides has been found to be well described by the Ostwald ripening model, as follows:where Rt and R0 are the radii of copper sulfide precipitates, respectively, at t = t and t = 0 where t is time, kO is the rate constant in this model and T is thermodynamic temperature. The diffusion coefficients and activation energy derived from values of kO are close to those of copper in austenitic iron. On the basis of the growth kinetics, it has been proposed that the heat-treatment for as-cast strip steel should be conducted at around 1 273 K, at which the size of copper sulfide precipitates can be controlled to be as small as 20-30 nm in several tens of minutes.

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Morphology Control of Copper Sulfide in Strip Casting of Low Carbon Steel

Cited by 39 publications

References 32 publications

Isothermal Precipitation Behavior of Copper Sulfide in Ultra Low Carbon Steel

Isothermal Precipitation Behavior of Copper Sulfide in Ultra Low Carbon Steel

Thermodynamic Properties of the MnS^|^ndash;CuS0.5 Binary System

Growth Rate of Copper Sulfide Precipitates in Solid Low Carbon Steel

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