Evolution of Oxide Inclusions in G20CrNi2Mo Carburized Bearing Steel during Industrial Electroslag Remelting

The variation of non-metallic inclusions and total oxygen contents in different steel grades were investigated by taking samples in steelmaking process, including gear steel, anchor chain steel, hard wire steel, bearing steel and spring steel. The inclusions mainly were Al2O3, MnS, and their composite inclusions in aluminum killed steel at the beginning of LF refining due to addition of FeAl alloy during the tapping from EAF and feeding of Al wire in LF process, and then Al2O3 inclusion changed to the Al2O3 - CaO composite inclusions after feeding of SiCa wire. The inclusions at the beginning of LF refining mainly were MnS, SiC and their composite inclusions in non-aluminum killed steel due to addition of the composite deoxidation and slagging agents (mainly including CaC2 and SiC) when EAF taping, while the inclusions in tundish mainly were MnS, CaO - SiO2 - Al2O3 composite oxide - sulfide inclusions. It is showed that the inclusions in bearing steel and spring steel samples were mainly globular oxide inclusions and silicate inclusions with higher rated results. Therefore, the refining process should be improved to remove globular oxide inclusions. The inclusions in molten steel were controlled by enhancing the diffusion deoxidation process, adjusting and controlling the basicity and composition of refining slags, respectively, and satisfactory results were obtained. The industrial test shows that the total oxygen content of the aluminum killed steel in the test heat after feeding wire reached the minimum value, which indicates that the optimized slag has a strong ability of absorbing Al2O3 inclusions. For non-aluminum killed steel, the total oxygen content was 0.0027 % to 0.0029 % in rolled products. The inclusions in the end of refining and rolled product were small and dispersed composite inclusions, and the separate Al2O3 inclusions can not be found in the non-aluminum killed steel after optimization of the refining process.

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Effect of CeO2 addition in the slag on inclusions of FGH96 superalloy during electroslag remelting

Metallurgical Research & Technology ◽

10.1051/metal/2020041 ◽

2020 ◽

Vol 117 (5) ◽

pp. 501

Author(s):

Xiaoyong Gao ◽

Lin Zhang ◽

Xuanhui Qu ◽

Yifeng Luan ◽

Xiaowei Chen

Keyword(s):

Oxygen Content ◽

Molten Slag ◽

Oxide Inclusion ◽

Electroslag Remelting ◽

Molten Alloy ◽

Number Density ◽

Oxide Inclusions ◽

Order Of Magnitude ◽

Main Factors

The FGH96 superalloy was electroslag remelted by utilizing CeO2 containing slag. CeO2/Al2O3 ratio and atmosphere are found to be the main factors that control the oxide inclusion contents during electroslag remelting (ESR). The reaction between CeO2 in the molten slag and Al in the molten alloy leads to the increased dissolved Ce in the molten alloy, which is effective to remove oxide inclusions. Dissolved Ce reacts with MgO in the inclusions, leading to the transformation of Al2O3–MgO inclusion in the electrode to Al2O3–MgO–Ce2O3 and Al2O3–Ce2O3 inclusions in the ESR ingot. In case of low CeO2/Al2O3 ratio of 0.263, oxygen content decreases to as low as 8 ppm after ESR under vacuum, and the number density of oxide inclusion decreased by an order of magnitude in comparison to the electrode. In case of high CeO2/Al2O3 ratio of 5.0, oxygen content decreases further to 6 ppm no matter what the condition is.

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Effect of the Al2O3 Content in the Slag on the Chemical Reactions and Nonmetallic Inclusions during Electroslag Remelting

Metallurgical and Materials Transactions B ◽

10.1007/s11663-020-01896-8 ◽

2020 ◽

Vol 51 (5) ◽

pp. 1904-1911 ◽

Cited By ~ 2

Author(s):

Reinhold S. E. Schneider ◽

Manuel Molnar ◽

Gerald Klösch ◽

Christopher Schüller

Keyword(s):

Chemical Composition ◽

Service Life ◽

Nonmetallic Inclusions ◽

Roller Bearing ◽

Bearing Steel ◽

Electroslag Remelting ◽

Al2o3 Content ◽

Spinel Type ◽

Bearing Steels ◽

Equilibrium Reactions

Abstract The service life of roller bearings is extremely sensitive to large and hard nonmetallic inclusions (NMIs), requesting the highest standards in their production. To determine the metallurgical possibilities, the effect of Al2O3 contents between 0 and 33 pct in the remelting slag was investigated by remelting a roller bearing steel in an experimental electroslag remelting (ESR) plant. Thereby, changes in the chemical composition of the materials (electrode vs ingots) and in the remelting slag during remelting, as well as the amount and composition of the NMIs prior to and after remelting, were investigated. Changes in the chemical composition can largely be explained by equilibrium reactions between the slag and the metal, thereby low Al contents in the remelted materials could only be achieved with the lowest Al2O3 contents in the slag. Furthermore, higher Al2O3 contents in the slag also lead to higher oxygen and sulfur contents in the steel as well as higher amounts of NMIs after remelting. The composition of the NMIs changed from alumina type for high Al2O3 contents to spinel type and other mixed MgO-SiO2 oxides for low Al2O3 contents. The results indicate solutions for the production of bearing steels with the lowest amounts of undesired large and hard NMIs.

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Evolution of Oxide Inclusions in Si-Mn-Killed Steel During Protective Atmosphere Electroslag Remelting

Metallurgical and Materials Transactions B ◽

10.1007/s11663-019-01564-6 ◽

2019 ◽

Vol 50 (3) ◽

pp. 1139-1147 ◽

Cited By ~ 9

Author(s):

Chengbin Shi ◽

Joo Hyun Park

Keyword(s):

Electroslag Remelting ◽

Protective Atmosphere ◽

Oxide Inclusions

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