The Change of Composition of Inclusion during Ca Treatment

Self Cite

To examine the reaction mechanism of the variation of calcium content in inclusions and the molten steel and the effect of flux composition on the reaction, the variations of molten steel content and inclusion content during CaO, 60%CaO-40%CaF2 or 50%CaO-50%CaSi powder blowing onto the molten steel under reduced pressure were investigated with 15 kg scale experiments. From the experimental results, it was found that the inclusion composition was changed from Al2O3 to Al2O3-CaO by CaO flux that did not contain CaSi alloy, and that the reaction path of the inclusion composition was changed remarkably by CaSi alloy in CaO flux. From the experimental results and the chemical thermodynamic calculation, the effects of the flux and CaSi alloy on the change in composition of inclusion and melts were examined.

Section: Introductionmentioning

confidence: 99%

Change in Inclusion Composition during CaO Flux Powder Blowing under Reduced Pressure

Numata¹,

Higuchi²

2012

Self Cite

“…The 20,38) enter the bulk of melt, and transfer to the surface of Al2O3 inclusions. Then some MgO·Al 2 O 3 and CaO-MgO-Al 2 O 3 form on the surface of Al2O3 inclusions as Eqs.…”

Section: Change Mechanism Of Inclusionsmentioning

confidence: 99%

“…14(a)), however, actually the alumina was not fully changed to MgO·Al2O3 spinel in the plant experiment. [19][20][21][22][23][24][25][26][27] and some models have been proposed. [25][26][27] There are few thermodynamic calculation on the transformation of MgO·Al 2 O 3 spinel inclusions by calcium treatment.…”

Section: Formation Thermodynamics Of Oxide Inclusionsmentioning

confidence: 99%

Characteristics of Inclusions in Low Carbon Al-Killed Steel during Ladle Furnace Refining and Calcium Treatment

Yang

Zhang

Wang³

et al. 2013

172

112

A plant trial of the productions of LCAK steel was performed, and characteristics of inclusions during LF refining and calcium treatment were investigated. Besides, thermodynamic diagram among magnesium, aluminum, and oxygen as well as calcium, magnesium, aluminum, and oxygen in the steel melt were studied to understand the fundamentals of inclusion modification by calcium treatment in LCAK steel. Furthermore, the change mechanisms of oxide inclusions and the precipitation of calcium sulfide were discussed. The experimental results showed that oxide inclusions were partly changed along with the path of Al2O3→MgO·Al2O3→(MgO·)CaO·Al2O3, which was a little different from the thermodynamic calculation results due to the limited kinetic conditions. Calcium treatment somehow modified the inclusions, however, many large inclusions were generated, and the modification effect would be dramatically decreased by the formation of large amount of CaS inclusions, which appeared with three main distribution forms. The formation of inclusions after calcium treatment were discussed based on the thermodynamic analysis. In order to reach the target of modification, sulfur concertration in steel should be reduced to a small amount to decrease the formation of CaS.

“…Reduction of inclusions and impurities by slag control made it possible to produce highly clean steels that had low HIC susceptibility due to less crack initiation sites. [9][10][11] Along with decrease in Manganese and Phosphorous contents, the soft reduction technology in continuous casting process was applied to decrease centerline segregation of the slab. 12) Those advanced technologies in steelmaking and continuous casting processes extraordinary contributed to development of sour resistant materials for line pipe.…”

Section: Hydrogen Induced Cracking (Hic) and Hic Evaluation Methodsmentioning

confidence: 99%

Recent Activities in ISIJ HLP Research Committee Corrosion Working Group: Proposal of pH Buffer Test Solution for Fitness-For-Purpose HIC Evaluations

Mizuno¹,

Yasuda²,

Ishikawa³

et al. 2016

The HLP (High-strength Line Pipe) Research Committee in the Iron and Steel Institute of Japan (ISIJ) has investigated the major issues of line pipes from the viewpoints of corrosion and fracture. Fitness-ForPurpose (FFP) evaluations for Hydrogen Induced Cracking (HIC) have been the subject of considerable study in recent years. FFP is the idea that appropriate materials are chosen depending on the severity of the use environment. Therefore, it is possible that the applicable range of material strength and the flexibility of manufacturing can be expanded by establishing the FFP evaluation approach. This paper reviews the recent activities of the HLP Corrosion Working Group during the past few years.The current status of the conventional HIC test method and FFP HIC evaluation methods were overviewed. Based on the results of a variety of experiments, the HLP Research Committee proposed a HIC test solution for FFP evaluations in the NACE Task Group. The proposed solution is a highly concentrated acetate buffer solution that is 5%NaCl + 0.93N − (CH 3 COOH + CH 3 COONa), and is expected to be adopted as the optional solution in NACE TM0284. The solution displayed an excellent pH buffering capacity during a long-term HIC test in comparison with the conventional HIC test solutions. The corrosion rate and hydrogen permeation behavior of the steel specimen in the solution were similar to those in the conventional solutions.KEY WORDS: the HLP Research Committee; line pipe; HIC; Fitness-for-Purpose; pH buffer.