Effects of Cr Diffusion on $RRR$ Values of Cr-Plated Nb$_{3}$Sn Strands Fabricated by Internal-Tin Process

Kim, Jiman; Sim, Kihong; Jang, Kyeong-Ho; Je, Sanghyun; Park, Pyeongyeol; Oh, Sangjun; Kim, Keeman

doi:10.1109/tasc.2008.922300

Cited by 10 publications

(1 citation statement)

References 3 publications

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“…The 8 TF strand types are covering several different heat treatment cycles with different durations and temperature plateaux. This has to be considered if comparing the quality or RRR performance [20][21][22]. Furthermore, batch variations are more pronounced in case of multiple suppliers for the Cu stabiliser.…”

Section: Residual Resistance Ratio (Rrr) and Cr Platingmentioning

confidence: 99%

Statistical analysis of the Nb₃Sn strand production for the ITER toroidal field coils

Vostner¹,

Jewell

Pong

et al. 2017

Supercond. Sci. Technol.

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The ITER toroidal field (TF) strand procurement initiated the largest Nb 3 Sn superconducting strand production hitherto. The industrial-scale production started in Japan in 2008 and finished in summer 2015. Six ITER partners (so-called Domestic Agencies, or DAs) are in charge of the procurement and involved eight different strand suppliers all over the world, of which four are using the bronze route (BR) process and four the internal-tin (IT) process. In total more than 500 tons have been produced including excess material covering losses during the conductor manufacturing process, in particular the cabling. The procurement is based on a functional specification where the main strand requirements like critical current, hysteresis losses, Cu ratio and residual resistance ratio are specified but not the strand production process or layout. This paper presents the analysis on the data acquired during the quality control (QC) process that was carried out to ensure the same conductor performance requirements are met by the different strand suppliers regardless of strand design. The strand QC is based on 100% billet testing and on applying statistical process control (SPC) limits. Throughout the production, samples adjacent to the strand pieces tested by the suppliers are cross-checked ('verified') by their respective DAs reference labs. The level of verification was lowered from 100% at the beginning of the procurement progressively to approximately 25% during the final phase of production. Based on the complete dataset of the TF strand production, an analysis of the SPC limits of the critical strand parameters is made and the related process capability indices are calculated. In view of the large-scale production and costs, key manufacturing parameters such as billet yield, number of breakages and piece-length distribution are also discussed. The results are compared among all the strand suppliers, focusing on the difference between BR and IT processes. Following the completion of the largest Nb 3 Sn strand production, our experience gained from monitoring the execution of the QC activities and from auditing the results from the measurements is summarised for future superconducting strand material procurement activities.

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Section: Residual Resistance Ratio (Rrr) and Cr Platingmentioning

confidence: 99%

Statistical analysis of the Nb₃Sn strand production for the ITER toroidal field coils

Vostner¹,

Jewell

Pong

et al. 2017

Supercond. Sci. Technol.

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Heat treatment effect on the strain dependence of the critical current for an internal-tin processed Nb3Sn strand

Park

Lee

et al. 2010

Physica C: Superconductivity

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Influence of heat treatment excursion on critical current and residual resistivity ratio of ITER Nb₃Sn strands

Lü¹,

McGuire²,

Hill³

et al. 2017

Supercond. Sci. Technol.

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Heat treatment is critically important to the performance of Nb3Sn superconducting strands. For very large Nb3Sn magnet coils, such as the International Thermonuclear Experimental Reactor (ITER) Central Solenoid (CS) coils, heat treatment carries risk of temperature and time excursion, which may result in performance degradation. Therefore, it is prudent to study the effect of possible excursion on Nb3Sn performance. In this study, Nb3Sn strands used for ITER CS coils are heat treated at different temperatures for different times. Their critical current, residual resistance ratio and hysteresis losses are measured. It is found that in the range we studied, critical current and hysteresis losses do not change significantly. Residual resistance ratio, however, decreases with increasing heat treatment temperature and time. This is attributed to the diffusion of metallic elements from the plated Cr layer to the copper stabilizer. Based on a model of metallic elements diffusion, a numerical code is developed to predict residual resistance ratio as a function of heat treatment temperature and time.

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Effects of Cr Diffusion on $RRR$ Values of Cr-Plated Nb$_{3}$Sn Strands Fabricated by Internal-Tin Process

Cited by 10 publications

References 3 publications

Statistical analysis of the Nb₃Sn strand production for the ITER toroidal field coils

Statistical analysis of the Nb₃Sn strand production for the ITER toroidal field coils

Heat treatment effect on the strain dependence of the critical current for an internal-tin processed Nb3Sn strand

Influence of heat treatment excursion on critical current and residual resistivity ratio of ITER Nb₃Sn strands

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Effects of Cr Diffusion on $RRR$ Values of Cr-Plated Nb$_{3}$Sn Strands Fabricated by Internal-Tin Process

Cited by 10 publications

References 3 publications

Statistical analysis of the Nb3Sn strand production for the ITER toroidal field coils

Statistical analysis of the Nb3Sn strand production for the ITER toroidal field coils

Heat treatment effect on the strain dependence of the critical current for an internal-tin processed Nb3Sn strand

Influence of heat treatment excursion on critical current and residual resistivity ratio of ITER Nb3Sn strands

Contact Info

Product

Resources

About

Statistical analysis of the Nb₃Sn strand production for the ITER toroidal field coils

Statistical analysis of the Nb₃Sn strand production for the ITER toroidal field coils

Influence of heat treatment excursion on critical current and residual resistivity ratio of ITER Nb₃Sn strands