270 w œwz 29«6y (2009. 12) y xk r w ** 'F.O4w y xk e.o4 w Á½ k * Á½ w w v œw l Morphology and Segregation of Sulfide Inclusions in Cast Steels (II) (Influence of [Mn/S] Ratios on the Morphology of Sulfide Inclusions in Fe-Mn-S Alloys) Heung-Il Park, Ji-Tae Kim*, and Woo-Yeol Kim Department of materials processing engineering, Graduate school, Pukyung National University, Busan, 608-739, Korea *Samyoung M-Tek Co., Ltd., Kyungnam, 637-941, Korea Abstract After casting button-type small ingots of ternary Fe-Mn-S alloys which had three different Mn/S ratios (1, 5 and 70) in a vacuum arc furnace, the effect of the ratio on the sulfide formation was investigated. In case of the Mn/S ratio of 1, if alloy composition was located in an iron-rich corner on a Fe-Mn-S ternary phase diagram, only duplex MnS-FeS sulfide films were observed in the grain boundary. If the alloy composition was located in the miscibility gap area of the phase diagram, primary globular dendritic sulfides and dendritic sulfide slags were generated within the grain and tubular monotectic sulfides were also detected in the grain boundary. When the Mn/S ratio was 5, if the alloy composition was in the iron-rich corner, only bead-like sulfides were generated. On the other hand, if the composition was in the miscibility gap area, globular dendritic sulfides and dendritic sulfide slags were generated in the form of primary sulfide inclusions and rod-like eutectic sulfides were observed in the grain boundary. Especially, if the contents of Mn and S increased more in the miscibility gap area of the phase diagram, primary globular sulfides containing iron intrusions were observed. In case of Mn/S ratio of 70, if the contents of Mn and S was decreased in the Fe corner of the phase diagram, only bead-like sulfides were observed in the grain boundary. Despite the composition was outside the miscibility gap area of the phase diagram, if the contents of Mn and S increased, clusters of fine sulfide particles as well as fine spherical primary monophase sulfides were observed in the grain boundary. Key words : Fe-Mn-S alloys, Sulfide inclusions and morphology, Mn/S ratios. (Received November 8, 2009 ; Accepted December 8, 2009) 1. y» w ƒ y xk, r w ù œ w w [1-8]. Sims [9,10] y xk w Type I y Type III ƒx y Type II v y» { ww š w. y(s) w w (Mn) ƒ FeS y š š MnS y w y z ƒ [11,12]. Mn š w w w, Mn ƒ, [Mn/S] w w [13-16]. E. T. Turkdogan [14] š vw [Mn/ S] ƒ 3.0 w, H. Nakata [16] [Mn 3 /S] ƒ 1.5 wƒ š w z w š š w. Fe-FeS[17], Fe-Mn-S Fe-C-Mn-S w y xk wš, x t y r [18] š w wwš. [Mn/S] ƒ t x ù š w r [Mn/S] yƒ ¼, [Mn/S] ƒ w Mn S w ƒ w y xk š w» w x». w [Mn/S] ƒ 1, 5 70 ƒƒ r Mn S w y k E-mail : castpark@pknu.ac.kr
y xk r w (II) (Fe-Mn-S w y xk e Mn/S w)- et al. 271 Fe-Mn-S w x wš, w y xk e [Mn/S] w w. 2. x 2.1 r 5g, 12-13 mm, 7-8 mm j» x œ j w (Vacuum arc furnace, 220V, 60Hz, 30kW) þ»q w w.»q y (99.9%) (99.9%), š Fe- 39wt.%S w s w wš j ww t r w. r r yw» w x 3z ww. Table 1 x r [Mn/S] yw ùkü. r [Mn/S] ƒƒ 1, 5 70 3ƒ ù. Mn ys š S ys [Mn/S] ƒ 1 r Mn/S w (wt.%) ƒƒ 0.7/0.7 (IA) 1.4/1.4 (IIA) 2ƒ. [Mn/S] ƒ 5 r Mn S w j s ƒw, Mn/S w (wt.%) ƒƒ 0.7/0.14 (IB), 1.4/0.28 (IIB), 3.5/ 0.7 (IIIA) 7.0/1.4 (IIIB) 4ƒ. š Mn y s jš S ys [Mn/S] ƒ 70 r Mn/S w (wt.%) ƒƒ 0.7/0.01 (IC), 1.4/0.02 (IIC), 3.5/ 0.05 (IIIC) 7.0/0.10 (IIID) 4ƒ. 2.2 y x r wš qw w. k, ù k y w r w Ÿwx x (SEM) y xk w. y s y w EPMA w w. y e r 5-6 mm m w. Fig. 1 x x x e ùkü. 3. x š 3.1 y xk x y p k š ü y y (primary sulfide inclusions), š š y 2 y (secondary sulfide inclusions) w Table 1. Chemical compositions of Fe-Mn-S alloy specimens used for morphological study of sulfide inclusions. [Mn/S] ratios 1 5 70 (Mn/S)wt.% [IA] 0.7/0.7 [IB] 0.7/0.14 [IC] 0.7/0.01 [IIA] 1.4/1.4 [IIB] 1.4/0.28 [IIC] 1.4/0.02 - [IIIA] 3.5/0.70 [IIIC] 3.5/0.05 - [IIIB] 7.0/1.4 [IIID] 7.0/0.10 Fig. 1. (a) shape and (b) dimensions of a button-type small steel ingot produced by vacuum arc melting system. The dark circle in Fig. 1b indicates a metallographic examination point of specimens.. Fig. 2 t y ùkü. Fig. 2a(IIID), Fig. 2b(IIA), Fig. 2c(IIIA) Fig. 2d(IIIB) Fig. 2f(IIIB ) ù k w Ÿwx. š Fig. 2e Fig. 2d(IIIB) w r y w x (SEM). Fig. 2a [Mn/S] ƒ 70 IIID. j» 5 µm w y, y EPMA 7.8%Fe-57.1%Mn-35.1%S(at.%). Fig. 2b [Mn/S] ƒ 1 IIA. j» 10-20 µm š y, y yw 8.2%Fe-40.9%Mn- 50.9%S(at.%). Fig. 2c [Mn/S] ƒ 5 IIIA. lù p j» 10-20 µm š y, y yw 2.6%Fe-49.1%Mn-48.3%S(at.%). Fig. 2a, Fig. 2b Fig. 2c y xk j» œm. l y, FeSƒ š š Mn(Fe)S y. Fig. 2d [Mn/S] ƒ 5 IIIB. (ring shape) y lù p. y yw 2.0%Fe- 47.8%Mn-50.1%S(at.%). Fig. 2f Fig. 2d w IIIB r. yw 2.0%Fe-46.8%Mn-51.2%S(at.%), Fig. 2d y yw w Mn(Fe)S y y. l š y š w ù e w. y x y IIA, IIIA IIIB. Fig. 2e Fig. 2d y y k SEM. Fig. 2d y» Fe. š Fig. 2f y Fe. Fe-MnS k [19,20] 1610 o C š
272 Journal of the Korean FoundrymenÌs Society Vol. 29, No. 6, 2009 Fig. 2. Typical as-cast microstructures and morphology of the primary sulfide inclusions; (a) fine spherical mono-phase sulfides in IIID, (b) globular dendritic sulfides in IIA, (c) globular dendritic sulfides enveloped in austenitic shell in IIIA, (d) globular dendritic sulfides contain iron intrusion in IIIB and (f) dendritic sulfide slags contain iron droplets in IIIB specimen, nital etched optical micrographs. Fig. 2 (e) shows a sulfuric acid deep-etched scanning electron micrograph of Fig. 2d. r Fe y (L M ) S y (Ls) œ w. wr y ƒ r [L M + Ls L M + Ls + MnS(solid)] 1610-1580 C o šw» wš Feƒ. r y šw ùš Feƒ Fig. 2e enw Fig. 2d y xk šw. w Fe enx Bigelow [19] š. wr Fig. 2f y Feƒ w w r y š Fe y enw Feƒ y s k e». 3.2 2 y xk Sims [9,10] y xk Type I, v Type II, š ƒx Type III y w. Fig. 3 2 y Fig. 3a, Fig. 3b v, Fig. 3d Type II w š, Fig. 3c Type I w. Fig. 3 x Fe-Mn-S w t 2 y xk, ù k w SEM. Fig. 3a [Mn/S] ƒ 5 IB SEM. w y. y yw 45.3%Fe-19.1%Mn-35.6%S(at.%). Fig.
y xk r w (II) (Fe-Mn-S w y xk e Mn/S w)- et al. 273 Fig. 3. Typical as-cast morphology of the secondary sulfide inclusions; (a) bead or chain-like sulfides in IB, (b) sulfide films or networks in IA, (c) clusters of fine sulfide particles in IIIC and (d) rod-like eutectic sulfides in IIIB specimen, nital deep-etched scanning electron micrographs. Fig. 4. Typical as-cast morphology of the secondary sulfide inclusions; (a) duplex MnS-FeS sulfide films in IA and (b) ring-like small sulfides in IIA specimen, sulfuric acid-etched optical micrographs. Fig. 4(c and d) show tubular monotectic sulfides observed in C area of Fig. 4b, nital deep-etched scanning electron micrographs.
274 w œwz 29«6y (2009. 12) Fig. 5. Effects of [Mn/S] ratios on the morphological changes of (a) primary and (b) secondary sulfide inclusions in Fe-Mn-S alloy specimens. 3b [Mn/S] ƒ 1 IA SEM. x v q y xk. Fig. 3c [Mn/S] ƒ 70 IIIC SEM. w y s, yw 56.7%Fe-22.7%Mn-20.6%S(at.%). Fig. 3d [Mn/S] ƒ 5 IIIB SEM, y yw 64.9%Fe-15.6%Mn-19.5%S(at.%). Bigelow [19] y Fe-MnS w œ w. Fig. 4a Fig. 4b ƒƒ [Mn/S] ƒ 1 IA IIA y y w Ÿwx. Fig. 4a IA v y A t w w z B t w 2. EPMA A yw 42.5%Fe- 6.5%Mn-51.1S(at.%) š B yw 40.1%Fe-15.8% Mn-44.1%S(at.%), A B Mn w 2. y MnS FeS š Mn(Fe)S y œ w MnS-FeS 2 y y. 2 y Mn w» Sƒ w IA IIA. Fredriksson [21] 2 y FeS š w MnS y (Q-phase) šw, Biglow [19] y x y xk
y xk r w (II) (Fe-Mn-S w y xk e Mn/S w)- et al. 275 (degenerate rod morphology) [Mn/S] ƒ w v ùkù š w. wr IIA (Fig. 4b) MnS-FeS 2 y wì C t w š y. y yw 34.1%Fe-51.3%Mn-14.5%(at.%), 2 y Mn w {. wr Fig. 4c Fig. 4d š y SEM. ù k š y w Fe k, Ÿwx š y 3-5 µm w q v ùq y y. [Mn/S] ƒ 1 IIA Mn S w, Mn S r ƒƒ. Fe-MnS k Lm MnS-FeS 2 y x wš, MnSƒ Ls r r y [20]. 3.3 y xk e [Mn/S] w Fig. 5 Fe-Mn-S 3 sx k [19,22] Fe. k Mn S œ r, š x r [Mn/S] ƒ. Fig. 5a Fig. 5b [Mn/S] Mn S w w ƒƒ w r 2 y xk Fe-Mn-S 3 sx k ùkü. Fig. 5a Fe-Mn-S 3 sx k œ (miscibility gap, Lm +Ls) ƒ w, [Mn/S] 1 IIA, [Mn/S] 5 IIIA IIIB Mn(Fe)S š y ƒ. Fe-MnS[19,20] k Mn w ƒw Feƒ (Lm) Sƒ (Ls) 2 x ƒ w. œ w y e w y j ew. wr Fe-Mn-S 3 sx k Fe, Mn S w û w [Mn/S] ƒ 1 IA, [Mn/S] ƒ 5 IB IIB, [Mn/S] ƒ 70 IC IIC y. ù [Mn/S] ƒ 70 w IIIC IIID Fe-Mn-S 3 sx k œ ù Mn S w w y. Fig. 5b x 2 y xk Fe- Mn-S 3 sx k ùkü. [Mn/S] ƒ 1 IA IIA r, FeS MnS 2 v y, p Fe-Mn-S 3 sx k œ w w IIA MnS-FeS 2 v y r y. [Mn/S] ƒ 5 IB IIB, [Mn/S] ƒ 70 IC IIC, Fe-Mn-S 3 sx k Fe Mn S w û w y. wr [Mn/S] ƒ 5, œ Mn S w IIIA IIIB w œ y. p [Mn/S] ƒ 70 r Mn w S w û Fe-Mn-S 3 sx k œ ù IIIC IIID w ˆ y ƒ. Table 2 x t y xk p k w. y (Fig. 2a), š y (Fig. 2b), lù p š y (Fig. 2c,d), Feƒ en y (Fig. 2d) Fe y (Fig. 2f) y. wr y (Fig. 3a), v y (Fig. 3b), s y (Fig. 3c), œ y (Fig. 3d), v FeS- MnS 2 y (Fig. 4a,b), š q v ùq ƒ r y (Fig. 4c,d) 2 y. 4. œ j [Mn/S] ƒ ƒƒ 1, 5 70 Fe-Mn-S Table 2. Morphological classification of sulfide inclusions observed in Fe-Mn-S alloy specimens. Groups Morphological classification Reference figures Specimens Fine spherical sulfides Fig. 2a IIIC, IIID Globular dendritic sulfides Fig. 2b IIA, IIIA, IIIB Primary sulfide inclusions Globular dendritic sulfides enveloped in austenitic shell Fig. 2c,d IIIA, IIIB Globular dendritic sulfides contains iron intrusion Fig. 2d,e IIIB Dendritic sulfide slags contain iron droplets Fig. 2f IIA, IIIA, IIIB Bead or chain-like sulfides Fig. 3a IB, IIB, IC, IIC Sulfide films or networks Fig. 3b IA, IIA Secondary sulfide inclusions Clusters of fine sulfide particles Fig. 3c IIIC, IIID Rod-like eutectic sulfides Fig. 3d IIIA, IIIB Duplex MnS-FeS sulfide films Fig. 4a,b IA, IIA Tubular monotectic sulfides Fig. 4c,d IIA
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