Effect of Slag-Metal Reaction on Transformation of Al2O3 inclusions in Pipeline Steel

2011 ◽  
Vol 284-286 ◽  
pp. 1143-1147
Author(s):  
Qiang Li ◽  
Xin Hua Wang ◽  
Hai Bo Li
Keyword(s):  
Molten Steel ◽  
Pipeline Steel ◽  
Refining Process ◽  
High Grade ◽  
Secondary Refining ◽  
Calcium Aluminates ◽  
Hydrogen Induced Cracking ◽  
Liquid Calcium ◽  
Calcium And Magnesium ◽  
Refining Time

For high grade pipeline steel, elimination of Al2O3 inclusions can improve the susceptibility of hydrogen-induced cracking (HIC) and stress corrosion cracking (SCC). In the present work, the transformation of Al2O3 inclusions with slag-metal reaction was studied by controlling ladle slag and relative technologies in LF-RH refining process. It is found that Al2O3 inclusions decrease with increasing refining time, and no pure Al2O3 inclusions exist in molten steel at the end of secondary refining; the remained inclusions in molten steel are liquid calcium aluminates and semi-liquid CaO-MgO-Al2O3 complex inclusions. The analysis of thermodynamic equilibrium proves that CaO and MgO in slag can be reduced by aluminum in molten steel, which is the source of calcium and magnesium in molten steel.

Effect of Nano CaO and MgO Addition on the Inclusions Composition in the Cast Microstructure of X80 Pipeline Steel

2013 ◽  
Vol 395-396 ◽  
pp. 289-292
Author(s):  
Yan Liu ◽  
Chun Lin He ◽  
Qian He Ma ◽  
Yang Liu
Keyword(s):  
Electron Microscope ◽  
Molten Steel ◽  
Pipeline Steel ◽  
Energy Dispersive Spectrometer ◽  
X80 Pipeline Steel ◽  
Composite Oxides ◽  
Segregation Phenomenon ◽  
Calcium And Magnesium ◽  
Scanning Electron ◽  
Cast Microstructure

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.

Effect of [Al]s, [Mg], [Ca] in Molten Steel on Inclusion Content for High Speed Wheel Steel during LF-VD Process

2014 ◽  
Vol 898 ◽  
pp. 60-63
Author(s):  
Yu Tang
Keyword(s):  
Fatigue Life ◽  
Molten Steel ◽  
High Speed ◽  
Refining Process ◽  
Fatigue Performance ◽  
Wheel Steel ◽  
Inclusion Content ◽  
High Basicity ◽  
Secondary Refining ◽  
Improve Fatigue

In order to improve fatigue life of wheel steel, LF-VD secondary-refining process is done with Al-deoxidation and slag of high basicity, high Al2O3 content and low oxidizing property. Inclusion content would be influenced by [Al]s, [Mg], [Ca] in molten steel. It is found that Al2O3 inclusions, which are the products of Al-deoxidation, would react with [Mg], [Ca] in molten steel to transform into CaO-MgO-Al2O3 complex inclusions, which is the key for the enhancement of fatigue performance for wheel steel.

Effect of Slag Composition on [Mg], [Ca] Content in Molten Steel for High Speed Wheel Steel

2013 ◽  
Vol 746 ◽  
pp. 501-504
Author(s):  
Tang Yu
Keyword(s):  
Molten Steel ◽  
Slag Composition ◽  
High Speed ◽  
Refining Process ◽  
Wheel Steel ◽  
Complex Inclusion ◽  
High Basicity ◽  
Secondary Refining ◽  
Positive Factor ◽  
Improve Fatigue

In order to improve fatigue life of wheel steel, secondary-refining process is done with Al-deoxidation and slag of high basicity, high Al2O3 content and low oxidizing property. [M, [C content in molten steel would be influenced by slag composition. It is found that high basicity, high Al2O3 content and low oxidizing property is positive factor for proper [M, [C content in molten steel which is the key of inclusion transformation from Al2O3 to CaO-MgO-Al2O3 complex inclusion, contributing to the enhancement of fatigue performance for wheel steel.

Effect of Nanometer Calcium and Magnesium Oxides Addition on the Cast Microstructure Grain Size of Pipeline Steel

2013 ◽  
Vol 380-384 ◽  
pp. 4245-4248
Author(s):  
Jian Ming Wang ◽  
Yan Liu ◽  
Long Xian Ding ◽  
Qian He Ma
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Molten Steel ◽  
Pipeline Steel ◽  
Great Influence ◽  
X80 Pipeline Steel ◽  
Line Method ◽  
Calcium And Magnesium ◽  
Cast Microstructure

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 cast microstructure grain size. The grain size of the cast microstructure in each sample was measured by the cutting line method. The results show that the nanometer oxides addition has a great influence on the cast microstructure grain size. When adding 0.01 wt% nanoCaO or MgO oxides, the grain size decreases from 0.664 mm to 0.632 mm and 0.457 mm, respectively. When adding 0.02 wt% nanoCaO or MgO oxides, the grain size becomes finer, and the cast microstructure is remarkably refined. In contrast with the grain size of no nanometer oxides addition, the grain size decreases from 0.644 mm to 0.438 mm and 0.389 mm and is refined by 1.47 and 1.66 times, respectively. When adding 0.05 wt% nanoMgO oxides, the grain size does not decrease, but increases to 0.778 mm. The reason is that as the amount of adding oxides increases, the dispersity of the nanometer oxides becomes worse, and the agglomeration of the grains occurs. Therefore, the nanometer oxides can not achieve the role of grain refinement.

Effect of Nanometer Calcium and Magnesium Oxides Addition on the Inclusions in the Cast Microstructure of X80 Pipeline Steel

2013 ◽  
Vol 401-403 ◽  
pp. 606-609
Author(s):  
Jian Ming Wang ◽  
Yan Liu ◽  
Chun Lin He ◽  
Yang Liu
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Molten Steel ◽  
Pipeline Steel ◽  
X80 Pipeline Steel ◽  
Oxide Addition ◽  
Calcium And Magnesium ◽  
Aggregation Phenomenon ◽  
Scanning Electron ◽  
Cast Microstructure

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) was used to analyse the morphology and distribution of the inclusions in the cast microstructure of the X80 pipeline steel. The results reveal that there are a small amount of inclusions in the sample of no nanometer oxides addition. With the amount of the nanoMgO oxide addition rising, the number of the inclusions in the sample firstly increases and then decreases gradually. When adding 0.05 wt% nanoMgO or CaO oxides, the size of the inclusions is big and the aggregation phenomenon appears. When adding 0.02 wt% nanoMgO or CaO oxides, the number of the inclusions in the cast microstructure is the most, whose size is smaller, about 2~4 μm and the inclusions are the most uniformly distributed.

Research of High Grade HIC-Resistant Pipeline Steel

2014 ◽  
Vol 900 ◽  
pp. 730-733 ◽  
Author(s):  
Xiu Hua Gao ◽  
Jing Li ◽  
Chuang Li ◽  
Yan Liang ◽  
Lin Xiu Du ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Pipeline Steel ◽  
Granular Bainite ◽  
High Grade ◽  
Good Resistance ◽  
Corrosion Resistant ◽  
Structures And Properties ◽  
Hydrogen Induced Cracking ◽  
Closed Formation

Carry out research on the processes, structures and properties of the X70 corrosion-resistant pipeline steel and analyze the mechanism of the hydrogen induced cracking. The results show that: the developed steel not only has excellent mechanical properties, but also has good resistance to H2S corrosion. Microstructure of the X70 corrosion-resistant pipeline is mainly the acicular ferrite and granular bainite, with well-closed formation and fine grains. Hydrogen Induced Cracking (HIC) begins with the appearance of the hydrogen blistering on the specimen surface, and cracks generated by the hydrogen blistering gradually extend inward from the surface along the grain boundary, diffuse inside the specimen gradually, and finally form hydrogen induced cracking.

Sign in / Sign up

Export Citation Format

Share Document