Mr. Mark, thanks for your comment concerning your blade steel HT.
Your notes started my memories on one high-temperature metallurgical experiment during my studies several decades ago. We were tasked to produce very clean Si or Ge ingot for electronic components using the method of zone-refining. This method utilises the fact that most impurities have higher solubility in the melt than in the solid metal. An impure bar was passed slowly through a hot zone which melted small section of the bar. The impurities built up in the melt and were "escaping" before the solidification front. After several passes high levels of cleanliness were reached.
Your notes started my memories on one high-temperature metallurgical experiment during my studies several decades ago. We were tasked to produce very clean Si or Ge ingot for electronic components using the method of zone-refining. This method utilises the fact that most impurities have higher solubility in the melt than in the solid metal. An impure bar was passed slowly through a hot zone which melted small section of the bar. The impurities built up in the melt and were "escaping" before the solidification front. After several passes high levels of cleanliness were reached.