Research on the variation of the inclusion and sulfur content in Pipeline steel

2021 ◽  
Vol 118 (2) ◽  
pp. 214
Author(s):  
Tongsheng Zhang ◽  
Rensheng Li ◽  
Wanlin Wang ◽  
Shifan Dai ◽  
Peisheng Lv ◽  
...  

Pipeline steel is widely used in various industries, and the sulfur content and inclusions in steel have a significant impact on performance, which determines whether the steel quality is qualified. The experiments were carried out to explore the sulfur content and inclusion evolution of pipeline steel which was deoxidized by Si–Mn–Al with “EAF-LF-VD-T-CC”. The samples of molten steel and slag were taken during the process of LF-VD-Tundish after EAF tapping. The kinetics model was established to simulate the desulfuration process of molten steel in actual production, obtaining a result which the error is within 3 ppm. It can be summarized that proper calcium treatment can transform the inclusion into a liquid inclusion, the value of [Ca] ranges from 25 to 45 ppm. Too high and lower calcium treatment can cause the compositions of inclusions to deviate from the liquid phase area, while too low calcium treatment will increase the overall size and density of the inclusions. In addition, the evolution of inclusion in steel at refining temperature and during solidification process was comprehensively calculated, considering all types of inclusions such as calcium oxide, magnesium oxide, aluminum oxide, calcium sulfide, spinel, calcium aluminate and liquid inclusion. The thermodynamic calculations are in good agreement with experimental results, which can predict the formation of the inclusions in Si–Mn–Al deoxidized pipeline steel.

2019 ◽  
Vol 116 (2) ◽  
pp. 206 ◽  
Author(s):  
Ming Li ◽  
Yang Liu ◽  
Lifeng Zhang

In the current study, the effect of reoxidation on inclusions during calcium treatment was studied via adding Fe2O3 into a Al-killed molten steel at 1 min after the addition of calcium. The total oxygen (T.O.) content increased from 10 to 24 ppm just after the reoxidation occurred, while it finally decreased to 14 ppm since inclusions were floated to the top of the steel and absorbed by the formed slag layer. The increased T.O. favored the decomposition of CaS, especially for the heat with high sulfur contents. The vaporization of calcium, which leads to the decrease of calcium content, is the driving force for the evolution of inclusions from CaO-CaS-(Al2O3) to CaO-Al2O3-(CaS) due to the limited degree of reoxidation. The contact angle between inclusions and the molten steel increased with the increase of Al2O3 in calcium alumina, which favored the removal of inclusions. Increased sulfur content decreased the surface tension of molten steel, which led to remove less inclusions since the contact angle between inclusions and the molten steel was decreased. Thus, more inclusions were measured in heats with higher sulfur content.


Minerals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1016
Author(s):  
Zhaoqi Song ◽  
Wei Liu ◽  
Yuhang Liu ◽  
Yongfeng Chen ◽  
Xiaotan Zuo ◽  
...  

Ds-type inclusions during production are an important factor affecting the performance and quality of manufactured 10B21 steel. To minimize Ds-type inclusions in steel and improve the production qualification rate of steelmaking plants, a refining slag system optimization scheme was proposed based on the analysis of current inclusion evolution during the steelmaking process, and industrial tests were conducted to verify improvements resulting from application of the proposed scheme. The results showed that the composition of Ds inclusions in 10B21 steel are mainly CaO–Al2O3–MgO–CaS–TiN, which exists in the form of calcium–magnesium aluminate coated with titanium nitride and calcium sulfide. The main reason for the formation of Ds inclusions is the poor fluidity of the refining slag and its low capability to absorb inclusions. The poor coverage of the refining slag on the molten steel during refining can easily cause secondary oxidation of the molten steel. Thus, the formation and growth of Ds-type inclusions are aggravated after the calcium feeding line and soft blowing operation. Here, we propose to minimize Ds inclusions using our optimized refined slag system. The mass percentage of the optimized slag system is CaO: 55–60%, Al2O3: 20–35%, SiO2: 3–7%, MgO: 4–8%, (MnO + FeO) < 1%, and the basicity is controlled within the range of 7–11. We observed that our optimized refining slag system has a significantly improved ability to remove inclusions, particularly Ds inclusions, which improves the qualification rate of 10B21 steel.


2013 ◽  
Vol 395-396 ◽  
pp. 289-292
Author(s):  
Yan Liu ◽  
Chun Lin He ◽  
Qian He Ma ◽  
Yang Liu

Nanometer calcium and magnesium oxides were added into molten steel by the carrier method in the experiment. The experiment takes the X80 pipeline steel as the research object and analyses the effect of nanometer calcium and magnesium oxides addition on the inclusions in the cast microstructure of the X80 pipeline steel. The scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) were used to analyze the composition of the inclusions in the cast microstructure of the X80 pipeline steel. The result reveals that when no addition of nanooxides, the inclusions in the cast microstructure are the C-Fe-Si-Al-Mn-based inclusions. When adding nanoMgO, the inclusions are mainly the composite oxides of Fe-Mg-Si-O, Fe-Mg-Si-Mn-O and Mg-Si-Mn-Al-O. When adding nanoCaO, the inclusions are mainly the composite oxides of Fe-Ca-Al-O, Fe-Ca-Si-O, Fe-Ca-Si-Mn-O and the composite oxides or sulfides of Fe-Ca-Si-Mn-O-S. There is more Fe in some inclusions and Fe is not uniformly dispersed in the molten steel. As the result, some certain segregation phenomenon takes place.


2013 ◽  
pp. 395-399
Author(s):  
Haiyan Tang ◽  
Tongbo Zhang ◽  
Jingshe Li ◽  
Yanqi Song

2019 ◽  
Vol 116 (6) ◽  
pp. 612
Author(s):  
Wanlin Wang ◽  
Liwen Xue ◽  
Tongsheng Zhang ◽  
Lejun Zhou ◽  
Daoyuan Huang ◽  
...  

The experiments were carried out to determine the transient behavior of the inclusion in Si-deoxidized stainless steel for high-grade plate. The samples were taken from three heats of the steel during the whole production process from the AOD to the mold, which were subsequently examined by an automatic scanning electron microscope with field energy dispersive spectrometer (FE-SEM&EDS). It can be summarized that appropriate calcium treatment intensity could modify inclusions into liquid ones. Excessive calcium treatment above ([Ca] = 25 ppm) will increase the melting point of the inclusions, which cannot keep in the liquid region at the solidification temperature. Therefore, the calcium addition in Si-deoxidized stainless steels should be controlled to a relatively lower value ([Ca] = 10 ppm). In addition, the content of aluminum in steel also has an important influence on the control of inclusion. When the content of aluminum ([Al] = 0.012%) is too high, the inclusions in steel are difficult to be controlled within the liquid phase. The chemical evolution of the inclusions in steel at high temperature and during solidification process were comprehensively calculated, considering all types of inclusions such as calcium oxide, aluminum oxide, silicon oxide, calcium aluminate, calcium silicate, mullite, and liquid inclusion. The thermodynamic calculations are in good agreement with experimental results, which can predict the formation of the inclusions in Si-deoxidized stainless steels.


Metals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 104 ◽  
Author(s):  
Yandong Li ◽  
Tongsheng Zhang ◽  
Huamei Duan

Experimental simulations of steelmaking with different amounts of aluminum were achieved in the tube furnace at 1873 K and field scanning electron microscopy and energy dispersive X-ray spectroscopy (FE-SEM and EDX) were employed to explore the characteristics of the inclusions in Ti-bearing steel during the calcium treatment process. It was found that morphologies, chemical compositions, and the size distribution of the inclusions were obviously different before and after calcium treatment. The calcium addition need be carefully considered regarding the mass fraction of aluminum with the purpose of modifying the solid inclusions to liquid phases. The thermodynamic analysis of inclusion formation in the Al–Ti–Ca–O system at 1873 K was conducted, as well as transformation behaviors of inclusions including all types of solid inclusions and liquid phases during solidification. The thermodynamic equilibrium calculations are in good agreement with experimental data, which can be used to estimate inclusion formation in Ti-bearing steel.


1947 ◽  
Vol 20 (1) ◽  
pp. 41-44
Author(s):  
F. T. Wall ◽  
F. W. Banes ◽  
G. D. Sands

Abstract The chain transfer theory of modifier action has been tested on commercial GR-S by means of molecular weight and sulfur content determination. The number of sulfur atoms per molecule was found to range between 0.7 and 1.1, to be compared to the theoretical value of unity. In view of the experimental difficulties involved, the results are considered to be in good agreement with the theory.


2011 ◽  
Vol 399-401 ◽  
pp. 189-194
Author(s):  
Hai Chuan Wang ◽  
Xin Li ◽  
Zhi You Liao ◽  
Ming Li ◽  
Zhang Xiu Qian ◽  
...  

The experiment has studied the effect of solidification process of Fe-C-S alloy treated RE on the distribution of elements and inclusions on the distribution of elements and inclusions after the electric pulse field is applied. The results show that Rare Earth in the molten steel has played a purification role and change the strip MnS inclusions into spherical sulfide inclusions. Meanwhile, the co-action of electric pulse field and Rare Earth can reduce and refine inclusions and improve the distribution of elements in solidification microstructure.


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