• 소성∙가공
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• 제19권5호
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• pp.311-319
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• 2010

Rare earth metal Ce has a relatively low melting point and high specific gravity. Because of its significantly high affinity to oxygen, nitrogen and sulfur, it is highly usable as a steel refining agent. However, because Ce compound has relatively high specific gravity, it is difficult to be separated from molten steel through floatation, and it degrades the purity of molten steel, or may clog the nozzle in continuous casting. Such problem may be solved by using an appropriate deoxidation agent together with Ce and settling molten steel sufficiently after refining. Thus a fundamental study in the formation behavior of non-metallic inclusion in Ce added Hyper Duplex STS melts was investigated. The addition amount of Ce, melt temperature were considered as experimental variables. A main non-metallic inclusion in mother alloy is 51(wt%MnO) - 27.6(wt%SiO$_2$)- 10.9(wt%$Cr_2O_3$). Non-metallic inclusion was dramatically decreased and the particle size was fined as the amount of Ce increased. Moreover (%MnO) and (%SiO$_2$) of non-metallic inclusion were decreased. But (%$Al_2O_3$)were relatively increased. The number of non-metallic inclusion were decreased and the large particle size were increased by increasing the temperature of molten steel.

• Journal of Welding and Joining
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• 제3권1호
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• pp.3-10
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• 1985

Lamellar tearing susceptibility and through-thickness tensile ductility have been investigated in $40kg/mm^2 and 50kg/mm^2$ class tensile strength steel plates in terms of cleanliness of non-metallic inclusion and welding condition. The plate which had 0.01% cleanliness of A-type inclusion (MnS) had 61% of the reduction of area in the through-thickness direction and did not show lamellar tearing. Lamellar tearing susceptibility decreased with increasing the preheat and interpass temperature. The plate which had 0.04% cleanliness of A-type inclusion did not show lamellar tearing under the condition of 75.deg. C of preheat and interpass temperature.

• 한국분말재료학회지
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• 제7권2호
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• pp.78-84
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• 2000

P/M high speed steels(1.28% C, 4.20% Cr, 6.40% W, 5.00% Mo, 3.10% V, bal. Fe) from two different venders were applied to powder compacting punch. The test results show that failure lifes were very different between two punches. These were no difference in volume fraction and mean size of carbides(MC or M6C) but non-metallic inclusions in two punches. Small amount of non-metallic inclusion in the punch did not greatly affect impact energy and transverse rupture strength (TRS). But, fatigue life was drastically decreased by non-metallic inclusions. These results show that fatigue failure was initated around non-metallic inclusion by cyclic load and the fatigue life was greatly affected by the presence of non-metallic inclusions in the punch.

• 소성∙가공
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• 제20권7호
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• pp.504-511
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• 2011

The alkaline earth metal Ba has a relatively low melting point. Because of its significantly high affinity to oxygen, nitrogen and sulfur, it is highly functional as a steel refining agent. But Ba can adversely affect the properties of steel especially the workability, because it can form a variety of inclusions. So, understanding of these inclusions is needed for improvement of the properties of steel. Thus a fundamental study in the formation behavior of non-metallic inclusions in Ba added Hyper Duplex STS melts was investigated. The amount of Ba, holding time and temperature were considered as experimental variables. The number of non-metallic inclusions decreased and the large particle size of non-metallic inclusions increased as the amount of Ba increased. The number of non-metallic inclusions also decreased and the large particle size increased with increased holding times and temperatures of molten steel.

• 한국신뢰성학회지:신뢰성응용연구
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• 제15권3호
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• pp.197-206
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• 2015

Failure analysis of pre-insulated pipe (SPPS 380, 400A) transporting high temperature water ($95{\sim}110^{\circ}C$) for a plant was carried out. The damaged area (${\Phi}5mm$) of pre-insulated pipe was found only on welds. The chemical composition of damaged pipe meets specification of carbon steel pipes for pressure service (KS D 3562). As results of microstructure analysis, crack propagated from outer to inside after pitting corrosion occurred on the outside surface. The non-metallic inclusion existed on the end of crack. And the non-metallic inclusion continuously and linearly formed along with the bond line of welds. Based on SEM-EDS analysis, the nonmetallic inclusions have higher Manganese (Mn) and Oxygen (O) content but sulfur (S) was not detected. As results of water quality analysis, hydrogen ion concentration and minerals like Fe, Mg, Si were in low level. But the content of dissolved oxygen (11.2 ppm) was slightly higher than that of standard. It seems that the cause of damaged pipe is grooving corrosion due to MnO inclusion formed on bond line and corrosion took place nearby welds.

• 대한금속재료학회지
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• 제46권4호
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• pp.257-266
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• 2008

AHydrogen induced cracking (HIC) was phenomenologically studied in terms of the effect of nonmetallic inclusions and hot rolling process parameters. By comparing the level of non-metallic inclusions in two different kinds of commercial grade steels having different HIC resistance, the role of non-metallic inclusions in HIC occurrence was investigated. Change in inclusion morphology and distribution during hot rolling was also studied throughout slab, rolling at austenite recrystallization region (roughing mill; RM) and rolling at austenite non-recrystallization region (finish mill; FM). In addition, the contribution of RM and FM parameters to HIC was investigated from the standpoint of change in inclusion morphology during hot rolling processes. As a result, HIC was closely related to the separation of large complex inclusion during hot rolling process. Large complex inclusions originated from the improper Ca treatment, after which equilibrium composition of slag should have resulted in eutectoid composition. By controlling the equilibrium slag composition equivalent to eutectoid one, HIC resistance could be improved due to the reduced size of inclusions. In addition, change in reduction/pass in RM had an effect on HIC resistance of steels while that in FM did not. Increase in the reduction/pass in the latter stage of RM improved HIC resistance of steels by enhancing the void enclosure around inclusions.

• Metals and materials international
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• 제24권6호
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• pp.1432-1437
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• 2018

This work investigated edge-cracking behavior of equiatomic CoCrFeMnNi high-entropy alloy during hot rolling at rolling temperatures $500{\leq}T_R{\leq}1000^{\circ}C$. Edge cracks did not form in the material rolled at $500^{\circ}C$, but widened and deepened into the inside of plate as $T_R$ increased from $500^{\circ}C$. Edge cracks were most severe in the material rolled at $1000^{\circ}C$. Mn-Cr-O type non-metallic inclusion and oxidation were identified as major factors that caused edge cracking. The inclusions near edge region acted as preferential sites for crack formation. Connection between inclusion cracks and surface cracks induced edge cracking. Rolling at $T_R{\geq}600^{\circ}C$ generated distinct inclusion cracks whereas they were not serious at $T_R=500^{\circ}C$, so noticeable edge cracks formed at $T_R{\geq}600^{\circ}C$. At $T_R=1000^{\circ}C$, significant oxidation occurred at the crack surface. This accelerated edge crack penetration by embrittling the crack tip, so severe edge cracking occurred at $T_R=1000^{\circ}C$.

• 한국세라믹학회지
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• 제20권4호
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• pp.283-288
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• 1983

The properties of basic tundish coating powder were investigated comparing with acidic tundish coating powder especially in the corrosion resistance to the molten steel and the influence on non-metallic inclusion. The results show that the basic coating powder is superior to the acidic coating powder in corrosion resistance. It is appeared that the basic coating powder lining has less influence on the formation of non-metallic inclusions. These results will be promissing to reduce the coating thickness in tundish lining operation.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.262-263
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• 2006

The free sintering of metallic powders blended with non sintering inclusions is investigated by the Discrete Element Method (DEM). Each particle, whatever its nature (metallic or inclusion) is modeled as a sphere that interacts with its neighbors. We investigate the retarding effect of the inclusions on the sintering kinetics. Also, we present a simple coarsening model for the metallic particles, which allows large particles to grow at the expense of the smallest.

• 한국자기학회지
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• 제10권6호
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• pp.302-309
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• 2000

박강판의 내부에 존재하는 개재물성 결함을 검사하기 위해 누설자속법을 이용하여 탐상하는 시스템을 개발하였다. 연자성 코어의 보자력을 이용한 차등형 플럭스게이트 자력계를 제작하였다. FEM 소프트웨어를 이용하여 전자석을 설계하였으며, 3축 이동이 가능한 누설자속탐상장치를 제작하여 냉연강판을 검사한 결과 개재물성 결함을 검사학 수 있음을 알았다. 누설자속값을 디지털화하여 2차원 이미지로 처리한 결과 냉연강판에 존재하는 개재물성 결함 이외의 결함을 일부 구분할 수 있음을 알았다.