共查询到20条相似文献,搜索用时 31 毫秒
1.
Chunyang Liu Motoki Yagi Xu Gao Sun-joong Kim Fuxiang Huang Shigeru Ueda Shin-ya Kitamura 《Metallurgical and Materials Transactions B》2018,49(1):113-122
During ladle furnace refining, initial Al2O3 inclusions generally transform into MgO·Al2O3 spinel inclusions; these generated spinel inclusions consequently deteriorate the product quality. In this study, the transformation from Al2O3 to MgO·Al2O3 was investigated by immersing an Al2O3 rod into molten steel, which was in equilibrium with both MgO and MgO·Al2O3 spinel-saturated slag. A spinel layer, with a thickness of 4 μm, was generated on the Al2O3 rod surface just 10 s after its immersion at 1873 K (1600 °C). The thickness of the formed spinel layer increased with the immersion period and temperature. Moreover, the MgO content of the generated spinel layer also increased with the immersion period. In this study, the chemical reaction rate at 1873 K (1600 °C) was assumed to be sufficiently high, and only diffusion was considered as a rate-controlling step for this transformation. By evaluating the activation energy, MgO diffusion in the generated spinel layer was found to be the rate-controlling step. In addition, this estimation was confirmed by observing the Mg and Al concentration gradients in the generated spinel layer. The results of this study suggest that the MgO diffusion in the spinel inclusions plays a substantial role with regard to their formation kinetics. 相似文献
2.
To investigate the evolution mechanism of Al2O3 inclusions after Mg treatment in H13 die steel, the determination of inclusions characteristics and thermodynamic calculation were carried out in the present study. The results showed that irregular and cluster Al2O3 inclusions in H13 die steel were modified to MgO·Al2O3 and MgO after Mg treatment. Two types of MgO·Al2O3 were detected after Mg treatment. The long-range gravity between the MgO-containing inclusions is weaker than that of the MgO-free inclusions. The long-range gravity between the inclusions decreases with the increasing of Mg content of the steel. The evolution mechanisms of inclusion in low Mg-containing and high Mg-containing H13 die steel were comprehensive discussed. The different reaction mechanisms result in the different of the core of the MgO·Al2O3 inclusion. 相似文献
3.
Yunqing Ji Chunyang Liu Yan Lu Huixiang Yu Fuxiang Huang Xinhua Wang 《Metallurgical and Materials Transactions B》2018,49(6):3127-3136
The slag composition plays a critical role in the formation of inclusions and the cleanliness of steel. In this study, the effects of FeO content and the C/A (CaO/Al2O3) ratio in the slag on the formation of inclusions were investigated based on a 10-minute slag–steel reaction in a MgO crucible. The FeO content in the top slag was shown to have a significant effect on the formation of MgO·Al2O3 spinel inclusions, and critical content exists; when the initial FeO content in the slag was less than 2 pct, MgO·Al2O3 spinel inclusions formed, and the T.O (total oxygen) was 20 ppm; when the initial FeO content in the slag was more than 4 pct, only Al2O3 inclusions were observed and the T.O was 50 ppm. It was clarified that the main source of Mg for the MgO·Al2O3 spinel inclusion formation was the top slag rather than the MgO crucible. In addition, the cleanliness of the steel increased as the initial FeO content in the top slag decreased. As regards the effects of the C/A ratio, the MgO amount in the observed inclusions gradually increased, whereas the T.O content decreased gradually with the increasing C/A ratio. Slag with a composition close to the CaO-saturated region had the best effect on the inclusion absorption. 相似文献
4.
Cheng-Bin Shi Xi-Chun Chen Han-Jie Guo Zi-Jiang Zhu Xiao-Lin Sun 《Metallurgical and Materials Transactions B》2013,44(2):378-389
The effect of calcium treatment and/or aluminum-based deoxidant addition on the oxygen control and modification of MgO·Al2O3 spinel inclusions during protective gas electroslag remelting (P-ESR) of H13 die steel with low oxygen content was experimentally studied. It is found that all the inclusions in the consumable electrode are MgO·Al2O3 spinels, besides a few MgO·Al2O3 spinels surrounded by an outer (Ti,V)N or MnS layer. After P-ESR refining combined with proper calcium treatment, all the original MgO·Al2O3 spinels in the electrode (except for the original MgO·Al2O3 spinels having been removed in the P-ESR process) were modified to mainly CaO-MgO-Al2O3 and some CaO-Al2O3 inclusions, both of which have a low melting point and homogeneous compositions. In the case of only Al-based deoxidant addition, all the oxide inclusions remaining in ESR ingots are MgO·Al2O3 spinels. The operation of Al-based deoxidant addition and/or calcium treatment during P-ESR of electrode steel containing low oxygen content is invalid to further reduce the oxygen content and oxide inclusions amount compared with remelting only under protective gas atmosphere. All the original sulfide inclusions were removed after the P-ESR process. Most of the inclusions in ESR ingots are about 2 μm in size. The mechanisms of non-metallic inclusions evolution and modification of MgO·Al2O3 spinels by calcium treatment during the P-ESR process were proposed. 相似文献
5.
《钢铁冶炼》2013,40(9):669-674
The effects of Mg on the inclusions and the as-cast microstructure of high carbon and high chromium die steel, a grade of cold working die steel with high C content of 1.4–1.6% and high Cr content of 11.0–13.0%, were systematically investigated. It is found that inclusions vary with the route as Al2O3 (No Mg) to MgO·Al2O3 +?Al2O3 (5?ppm Mg), and then to MgO+MgO·Al2O3 (11 and 15?ppm Mg). The average diameter of the inclusions decreased from 1.91 μm (no Mg) to 1.29 μm (15?ppm Mg), while the number density increased from 2.69?×?104 mm??3 (no Mg) to ~5.62?×?104 mm??3 (15?ppm Mg). The changes in the size and the number density were discussed in terms of the effect of inclusions on the nucleation process and the wettability of them with steel melt. The as-cast microstructures were greatly refined with Mg addition that correlated with the evenly dispersed fine Mg containing inclusions. 相似文献
6.
Cheng-Bin Shi Wen-Tao Yu Hao Wang Jing Li Min Jiang 《Metallurgical and Materials Transactions B》2017,48(1):146-161
Calcium modification of both alumina and MgO·Al2O3 inclusions during protective gas electroslag remelting (P-ESR) of 8Cr17MoV stainless steel and its effect on nitrides and primary carbides were studied by analyzing the transient evolution of oxide and sulfide inclusions in the P-ESR process. The oxide inclusions that were not removed during P-ESR without calcium treatment were found to retain their original state until in as-cast ingot. Calcium treatment modified all MgO·Al2O3 and alumina inclusions that had not been removed in the P-ESR process to liquid/partially liquid CaO-Al2O3-(MgO) with uniformly distributed elements, in addition to a small proportion of partially modified inclusions of a CaO-MgO-Al2O3 core surrounded by a liquid CaO-Al2O3. The modification of low-MgO-containing MgO·Al2O3 inclusions involves the preferential reduction of MgO from the MgO·Al2O3 inclusion by calcium and the reaction of calcium with Al2O3 in the inclusion. It is the incomplete/complete reduction of MgO from the spinel by calcium that contributes to the modification of spinels. Alumina inclusions were liquefied by direct reaction with calcium. Calcium treatment during P-ESR refining also provided an effective approach to prevent the formation of nitrides and primary carbides in stainless steel through modifying their preferred nucleation sites (alumina and MgO·Al2O3 inclusions) to calcium aluminates, which made no contribution to improving the steel cleanliness. 相似文献
7.
A plant trial of the production of 60Si2Mn–Cr spring steel using silicon–manganese combined with aluminium to deoxidise was performed, and the characteristics of inclusions during ladle furnace refining, calcium treatment and in billets were investigated by scanning electron microscope–energy dispersive spectroscopy and thermodynamic calculations. The formation mechanisms of oxide and CaS inclusions are discussed. The experimental observation and thermodynamic analysis showed that calcium treatment cannot entirely modify large-size MgO·Al2O3 spinel inclusions into homogeneous CaO–MgO–Al2O3 inclusions, but formed a liquid xCaO·yAl2O3 layer on its surface. When the Al content was 0.05 mass%, [Mg], [Ca] and [O] in molten steel could be controlled at 2.7~5 ppm, 2.5~8 ppm and 4.1~5.2 ppm, respectively, to achieve inclusions in the low melting point region. A large amount of CaS was generated in the present process due to a higher sulphur concentration in the molten steel and an excessive amount of Ca–Si wire. To avoid/reduce its formation, the sulphur concentration should be controlled to below 70 ppm. 相似文献
8.
Shufeng Yang Qiangqiang Wang Lifeng Zhang Jingshe Li Kent Peaslee 《Metallurgical and Materials Transactions B》2012,43(4):731-750
The current study performed thermadynamic calculation, laboratory experiments, and industrial trials for the formation and modification of MgO-Al2O3 spinel inclusions in alloy steels. The stability Mg-Al-O diagram was obtained using the thermodymanic study. The resulting MgO-Al2O3-CaO inclusions from MgO-Al2O3 spinel inclusions after the calcium treatment were spherical, and?>?5???m MgO-Al2O3-CaO inclusions have a two-layer structure: an outside CaO-Al2O3 layer and a MgO-Al2O3 core. The modification of?>?5???m MgO·Al2O3 spinel inclusions by calcium treatment includes two steps: (1) reducing MgO in the inclusion into the dissolved magnesium by the dissolved calcium in the steel and (2) generating a liquid xCaO·yAl2O3 layer at the outside of the spinel inclusion. For <2???m MgO·Al2O3 spinel inclusions, they can possibly be modified into a xCaO·yAl2O3 inclusion by reducing all MgO component in the spinel inclusions with the added calcium. 相似文献
9.
The stability diagram of MgO, spinel solid solution (MgO·(Al
X
Cr1−X
)2O3), and sesquioxide solid solution ((Al
Y
Cr1−Y
)2O3) as a function of Mg, Al, and O contents at a constant chromium content (18 mass pct) in liquid iron is drawn at 1873 K.
The interaction parameters between Mg and other solutes (Al, Cr, Ni, Ti, Si, and C) are determined by the experimental method,
which assures equilibrium between Mg vapor and liquid iron, were applied to calculate the diagram. Titanium deoxidation is
not recommended for the prevention of spinel formation, because Ti accelerates Mg dissolution from refractory or slag due
to its high affinity for Mg (e
Mg
Ti
= − 0.64). The standard Gibbs free energies of formation for the three inclusions (periclase, spinel, and sesquioxide solid
solutions) and the tielines between two solid solutions were calculated with the aid of the regular solution model and the
thermochemical F*A*C*T database computing system, respectively. The phase stability regions and oxygen content in steel for
the current Fe-Mg-Al-Cr (18 mass pct)-O system are compared with those of the previous non-Cr system. Detailed information
on the spinel composition according to Mg and Al contents is also available from the present stability diagram. 相似文献
10.
Chang-Woo Seo Seon-Hyo Kim Sung-Koo Jo Min-Oh Suk Sun-Min Byun 《Metallurgical and Materials Transactions B》2010,41(4):790-797
High-melting-point inclusions such as spinel(Al2O3·xMgO) are known to promote clogging of the submerged entry nozzle (SEN) in a continuous caster mold. In particular, Ti-alloyed
steels can have severe nozzle clogging problems, which are detrimental to the slab surface quality. In this work, the thermodynamic
role of Ti in steels and the effect of Ca and Ti addition to the molten austenitic stainless steel deoxidized with Al on the
formation of Al2O3·xMgO spinel inclusions were investigated. The sequence of Ca and Ti additions after Al deoxidation was also investigated. The
inclusion chemistry and morphology according to the order of Ca and Ti are discussed from the standpoint of spinel formation.
The thermodynamic interaction parameter of Mg with respect to the Ti alloying element was determined. The element of Ti in
steels could contribute to enhancing the spinel formation, because Ti accelerates Mg dissolution from the MgO containing refractory
walls or slags because of its high thermodynamic affinity for Mg
( e\textMg\textTi = - 0. 9 3 3). ( {e_{\text{Mg}}^{\text{Ti}} = - 0. 9 3 3}). Even though Ti also induces Ca dissolution from the CaO-containing refractory walls or slags because of its thermodynamic
affinity for Ca
( e\textCa\textTi = - 0.119 ), \left( {e_{\text{Ca}}^{\text{Ti}} = - 0.119} \right), dissolved Ca plays a role in favoring the formation of calcium aluminate inclusions, which are more stable thermodynamically
in an Al-deoxidized steel. The inclusion content of steel samples was analyzed to improve the understanding of fundamentals
of Al2O3·xMgO spinel inclusion formation. The optimum processing conditions for Ca treatment and Ti addition in austenitic stainless
steel melts to achieve the minimized spinel formation and the maximized Ti-alloying yield is discussed. 相似文献
11.
A thermodynamic equilibrium between the Fe-16Cr melts and the CaO-Al2O3-MgO slags at 1823 K as well as the morphology of inclusions was investigated to understand the formation behavior of the
MgO-Al2O3 spinel-type inclusions in ferritic stainless steel. The calculated and observed activities of magnesium in Fe-16Cr melts
are qualitatively in good agreement with each other, while those of aluminum in steel melts exhibit some discrepancies with
scatters. In the composition of molten steel investigated in this study, the log (X
MgO/X
Al
2O3) of the inclusions linearly increases by increasing the log [a
Mg/a
Al
2
·a
O
2
] with the slope close to unity. In addition, the relationship between the log (X
MgO/X
Al
2O3) of the inclusions and the log (a
MgO/a
Al
2O3) of the slags exhibits the linear correlation with the slope close to unity. The compositions of the inclusions are relatively
close to those of the slags, viz. the MgO-rich magnesia-spinel solid solutions were formed in the steel melts equilibrated with the highly basic slags saturated
by CaO or MgO. The spinel inclusions nearly saturated by MgO were observed in the steel melts equilibrated with the slags
doubly saturated by MgO and MgAl2O4. The spinel and the Al2O3-rich alumina-spinel solid solutions were formed in the steel melts equilibrated with the slags saturated by MgAl2O4 and MgAl2O4-CaAl2O4 phases, respectively. The apparent modification reaction of MgO to the magnesium aluminate inclusions in steel melts equilibrated
with the highly basic slags would be constituted by the following reaction steps: (1) diffusion of aluminum from bulk to the
metal/MgO interface, (2) oxidation of the aluminum to the Al3+ ions at the metal/intermediate layer interface, (3) diffusion of Al3+ ions and electrons through the intermediate layer, and (4) magnesium aluminate (MgAl2O4 spinel, for example) formation by the ionic reaction. 相似文献
12.
Wenkui Yang Jian Yang Runhao Zhang Han Sun Jingling Song Yinghui Zhao Xuan Zhou 《国际钢铁研究》2023,94(8):2300106
Herein, the formation and evolution mechanism of inclusions of Al2O3·SiO2·CaO and Al2O3·SiO2·CaO·MgO in seamless steel tube steel are investigated. In the long strip defects on the longitudinal cross section of the steel tube after the rolling bar piercing, the defect is mainly formed by Al2O3·SiO2·CaO·MgO inclusions and Al2O3·SiO2·CaO·inclusions dotted with·CaS inclusions after the rolling. The typical inclusions in the different steelmaking stages are mainly composed of CaS, Al2O3·(SiO2), CaO·(SiO2), MnS·(TiN), Al2O3·SiO2·CaO·(CaS)·(MnS), Al2O3·SiO2·CaO·MgO·(MnO), Al2O3·SiO2·CaO·MgO·(CaS)·(MnS), etc. In the billet, the average sizes of Al2O3·SiO2·CaO-based and Al2O3·SiO2·CaO·MgO-based inclusions are much larger than those of the other types of inclusions. Part of SiO2 in the deoxidized products SiO2 can be reduced by [Al], resulting in the formation of the Al2O3·SiO2 composite inclusions. The SiO2 in Al2O3·SiO2 inclusions can continuously be reduced by the dissolved [Ca] to form the Al2O3·SiO2·CaO composite inclusions. The SiO2 in the Al2O3·SiO2·CaO inclusions can be reduced by the dissolved [Mg] to form the Al2O3·SiO2·CaO·MgO composite inclusions. Another formation process of Al2O3·SiO2·CaO·MgO inclusions is the entrapment of ladle slag in the vacuum degassing (VD) stage, due to the strong agitation of the rising Ar bubbles in the vacuum condition of the VD stage. 相似文献
13.
A laboratory study was carried out to investigate non‐metallic inclusions in high strength alloying steel refined by high basicity slag. The results indicated that the inclusions were mainly of the CaO? MgO? Al2O3 system, Al2O3? MgO and MgO‐based inclusions. The steel/slag reaction time and Al2O3 content in slag had a great effect on inclusions characteristics. With the reaction time increasing from 30 to 180 minutes, inclusions experienced a transformation process: from mainly Al2O3? MgO system and MgO‐based inclusions to spherical CaO? MgO? Al2O3 system inclusions surrounded by a lower melting temperature surface layer of CaO? Al2O3. Formation and transformation mechanisms of the inclusions were given based on the results. It was also found that with Al2O3 content in slag reduced from 40% to 30%, [Mg] contents in steel melts were increased and MgO in slag reached saturation, which contributed to the formation of more MgO‐based inclusions and a more scattered inclusion composition distribution after 90 min reaction. 相似文献
14.
Xi-Chun Chen Cheng-Bin Shi Han-Jie Guo Fei Wang Hao Ren Di Feng 《Metallurgical and Materials Transactions B》2012,43(6):1596-1607
The effect of remelting atmosphere and calcium treatment during electroslag remelting (ESR) of Inconel 718 superalloy on the oxide inclusions and primary carbonitrides was investigated. The results show that after ESR refining combined with calcium treatment, the original oxide inclusions in the electrode, mainly MgO·Al2O3 spinels and some MgO inclusions, were modified to CaO-Al2O3 system inclusions or the inclusions of MgO·Al2O3 spinel core surrounded by CaO-MgO-Al2O3 system inclusion layer. Without the calcium treatment in ESR process, all the oxide inclusions in superalloy ingots are MgO·Al2O3 spinels. All the oxide inclusions in ESR ingots act as the nucleation site for carbonitride (Nb,Ti)CN with two-layer structure precipitation, except for those with a single (Nb,Ti)CN layer containing a small amount of Ti and N in the ingot refined by a proper amount of calcium addition in ESR process. The carbonitrides (Nb,Ti)CN formed directly on the oxide inclusion have a small amount of Nb and C as well as a relatively fixed atomic ratio of Nb/Ti (about 0.6:1). There is a Nb-rich and C-rich (Nb,Ti)CN layer on the pre-existing (Nb,Ti)CN formed on the oxide inclusion. The size of the observed carbonitrides is in the range of 5 ??m to 15 ??m. The calcium treatment in the ESR process has a significant effect on the morphology of carbonitrides in superalloy ingot due to modification of oxide inclusions by Ca-treatment resulting in the change of precipitation and growth conditions for carbonitrides. The morphologies of carbonitrides were changed from clustered block or single octahedral to skeleton-like after calcium treatment. 相似文献
15.
Liangjun Chen Weiqing Chen Wei Yan Yindong Yang Alexander McLean 《Canadian Metallurgical Quarterly》2019,58(3):335-345
Ca treatment is generally used in the production of Al-deoxidised steel to prevent nozzle blockage by modifying high melting point inclusions such as MgO·Al2O3 (Melting point: 2408?K). However, the successful application of Ca treatment can be quite difficult due to the requirements for stringent control of the amount of calcium that is added. In the present paper, a novel and effective method of inclusion modification by Na2CO3 treatment is developed and the evolution process of inclusions in Al-deoxidised steel with Na2CO3 treated is studied, which is in good agreement with FactSage calculation results. In addition, the relevant refractory/steel/inclusion interaction mechanisms are also discussed. The experimental results show that MgO–Al2O3 inclusions can be transformed into Na2O–MgO–Al2O3–SiO2 inclusions with low-melting points by Na2CO3 treatment. After Na2CO3 addition, both the dissolved [Na] and [Si] start to reduce MgO and Al2O3 in the generated MgO–Al2O3 inclusions from outside to inside, accompanied with the reduction of MgO–Al2O3 reaction layer at the steel-refractory interface by [Na] and [Si] in the steel. 相似文献
16.
To elucidate the morphology evolution of the inclusions in 16MnCrS5 steel with various masses of Mg addition, the experiments and thermodynamics were carried out with a high-temperature tube electric resistance furnace and FactSage software, respectively. The evolutions of the inclusions after the smelting and hot-processing were described. The experimental results show that with Mg addition of 35–42?ppm, many spindle and spherical inclusions with the size below 20?μm appeared, whereas the long-strip inclusions above 20?μm disappeared; after hot-processing, particularly, the h value was above 50%, beneficial to obtaining more spindle inclusions, and most spherical inclusions at 35?ppm were also obtained. The thermodynamics show that with Mg mass between 0.349 and 6.076?ppm, Al2O3 was easily converted to MgO·Al2O3, whereas above 6.076?ppm, Mg was directly converted to form MgO; above more, MgS coexisted with MgO. 相似文献
17.
This study describes an investigation into the improvement of castability, final surface quality and formability of titanium-stabilized AISI 409 ferritic stainless steel on an industrial scale. Non-metallic inclusions found in this industrially produced stainless steel were first characterized using SEM-EDS analyses through the INCA-Steel software platform. Inclusions were found to consist of a MgO·Al2O3 spinel core, which acted as heterogeneous nucleation site for titanium solubility products. Plant-scale experiments were conducted to either prevent the formation of spinel, or to modify it by calcium treatment. Modification to spherical dual-phase spinel-liquid matrix inclusions was achieved with calcium addition, which eliminated submerged entry nozzle clogging for this grade. Complete modification to homogeneous liquid calcium aluminates was achieved at high levels of dissolved aluminum. A mechanism was suggested to explain the extent of modification achieved. 相似文献
18.
Joo Hyun Park 《Metallurgical and Materials Transactions B》2007,38(4):657-663
19.
Al2O3-rich (>70?wt-%) inclusions generally hard and non-deformable are extremely detrimental for saw wire. In order to explore the source of this type of inclusion and provide solutions, experiments on the interaction between Al-containing MgO–C refractory and high-carbon steel for saw wire was conducted on a laboratorial scale using a cold crucible levitation melting furnace under vacuum conditions. [Al]S (acid-soluble Al), [C] and [Mg] concentrations in steel, Al2O3 concentration in inclusions and microstructure of refractory/steel interface, etc. were analysed to clarify the influence of vacuum pressure, refractory addition amount and interaction time. Based on the experimental results and thermodynamic calculations, a presumable impact mechanism of Al antioxidant in MgO–C refractory on the formation of Al2O3-rich inclusions in high-carbon steel for saw wire under vacuum conditions was deduced, which in turn provided a reference for the control of Al2O3-rich inclusions in high-carbon steel for saw wire. 相似文献
20.
The transformation of MgO ? Al2O3 based inclusions in alloy steel during refining has been studied by industrial trials. Besides Factsage software is used to study the formation and modification of spinel inclusions in alloy steel using calcium treatment during refining process. The results show that the transformation sequence of inclusions is: MgO ? Al2O3→CaO-Al2O3-MgO complex inclusions→MgO ? Al2O3, and under present experimental condition, in order to avoid forming MgO ? Al2O3 inclusions the content of dissolved Ca in the molten steel has to reach 1×10?6. Also the results show that when more calcium was added to molten steel, the content of Al2O3 and MgO will be lower. Besides, increasing the content of CaO in the inclusions will increase even if the content of SiO2 changes little. 相似文献