Effect of Ce Addition on Inclusions and Grain Structure in Gear Steel 20CrNiMo

To investigate the evolution of inclusions in high‐Al steel with addition of La, a series of laboratory experiments and thermodynamic calculations are performed, considering the reaction time and amount of La added. The main inclusions in the high‐Al steel without the addition of La are Al2O3, MnS, and Al2O3–MnS. The La treatment can efficiently modify Al2O3 to La–Al–O or La–O–S inclusions. For La additions less than 0.0041 wt%, the evolution route for the inclusion in high‐Al steel is Al2O3 → LaAl11O18 → LaAlO3 with an increase in reaction time. For high La additions, the evolution route for the Al2O3 inclusion is Al2O3 → LaAl11O18 → LaAlO3 → La2O2S → La2S3. The experimental results correlate with those of the thermodynamic analysis. Notably, excess La in high‐Al molten steel may consume O and S to form La oxysulfide and sulfide, respectively, which prevents the precipitation of MnS inclusion and promotes the formation of AlN inclusion during solidification.

{LaAl}_{11} {normalO}_{18} {+ 5 [La] = 6 LaAlO}_{3} + 5 [Al]

[ 17 ]…”

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Rare‐Earth La on Inclusion Evolution in High‐Al Steel

Zhu

Zhao

et al. 2021

“…The formation and modification of inclusions in steels have been widely investigated. [18][19][20][21][22][23][24][25][26][27] The thermodynamic equilibrium of Ce-O and Ce-O-S in the molten iron was studied. [28][29][30][31] Rare-earth elements had a strong affinity to oxygen and sulfur in the steel, [32] which could modify hard alumina [33,34] and elongated sulfides to rare-earth oxides or rare-earth oxy-sulfides.…”

Section: Introductionmentioning

confidence: 99%

Transient Evolution of Nonmetallic Inclusions in a Si–Mn‐Killed Stainless Steel with Cerium Addition

Zhang

Ren

et al. 2022

Laboratory experiments are performed to study the transient evolution of inclusions in Si–Mn‐killed stainless steels with additions of 40, 100, and 400 ppm cerium. With the increase of the cerium content in the molten steel, the evolution path of inclusions is Al2O3–SiO2–MnO–CaO → Ce2O3–Al2O3–SiO2–MnO–CaO → Ce2O3 → Ce2O3–CeS. The addition of 40 ppm cerium gradually increases the Ce2O3 content in liquid oxide inclusions. After the addition of 100 ppm cerium, inclusions first evolve to Ce2O3–Al2O3–SiO2–CaO–CeS, then to Ce2O3. The CeS is generated as a transient product then disappears. After the addition of 400 ppm cerium, liquid Al2O3–SiO2–MnO–CaO inclusions are modified to solid Ce2O3–CeS ones. The addition of 40 ppm cerium into the steel lowers the size from 1.74 to 1.53 μm. After the addition of 100 and 400 ppm cerium into the steel, the size of inclusions immediately decreases due to the formation of small Ce2O3–CeS inclusions and then increases owing to the collision of solid inclusions. A higher cerium content in the steel promotes the collision of Ce‐rich inclusions.

“…There have been extensive studies on the modification of Al 2 O 3based inclusions by REMs. [23][24][25][26][27][28][29] Li [25] studied the effect of lanthanum on inclusion evolution in high-Al steel and concluded that the evolution route was Al 2 O 3 ! LaAl 11 O 18 !…”

Section: Introductionmentioning

confidence: 99%

Modification Mechanism of Lanthanum on Alumina Inclusions in a Nonoriented Electrical Steel

Ren

Cheng

et al. 2022

The modification mechanism of lanthanum on alumina inclusions in a nonoriented electrical steel at 1600 °C is investigated using laboratory experiments. Inclusions are analyzed using an automatic scanning electron microscope equipped with energy‐dispersive spectrum at 1, 5, 10, and 30 min after lanthanum treatment. The contents of total oxygen (TO), total sulfur (TS), and total lanthanum (TLa) in steel are analyzed. Results show that Al2O3 inclusions are modified by lanthanum in two ways. One is that the dissolved lanthanum directly reduces the aluminum in Al2O3 inclusions and forms LaAl11O18 or LaAlO3 ones. The other is that a new La2O2S or LaS x shell is preferentially generated at the outside of Al2O3 and forms multiphase inclusions. With time increasing, the La2O2S or LaS x shell gradually reacts with the Al2O3 core and generates stable lanthanum‐containing inclusions. At the initial stage of lanthanum treatment, many transient inclusions including LaS x , La2O2S, and La–P(–As) are formed due to the high concentration of lanthanum, while gradually redissolving with time increasing. With the increase in TLa content in steel, the formation sequence of stable inclusions is Al2O3 → LaAl11O18 → LaAlO3 → La2O2S → LaS x , which is consistent with thermodynamic analysis.