This paper documents a series of experimental 4130 heats that had additions of rare earth master alloys with different rare earth oxide inclusions. Once melted, the heats were poured into keel block castings for mechanical testing and metallographic examination. Additionally, a single-thermocouple thermal analysis system was employed to examine the solidification reactions of each heat. Several interesting observations were made. First, the mechanical properties and solidification structure of the heats were similar, contrary to earlier work in 4130. Thermal analysis noted that the liquidus and peritectic did not shift with the master alloy additions. Inclusion characterization found that the inclusions in the final castings were significantly different from the ones in the master alloys. These inclusions contained low or no sulfur in them. Based on this, the author concludes that sulfur-containing rare earth inclusions are the likely nuclei in steels. This work identifies several important factors in the grain refinement of 4130. Not all rare earth inclusions cause refinement, supporting the conclusion by many that specific rare earth inclusions refine a steel’s structure by acting as heterogeneous nuclei. Sulfur-containing inclusions may be the compounds that are acting in this role. Additionally, shifts in the peritectic temperature appear related to the occurrence of refinement. No refinement in this work occurred, and no peritectic shift happened either. Other work in the literature observed an increase in the peritectic temperature and the onset of refinement. The peritectic reaction appears to play a role in steel solidification refinement.

本文记录了一系列的实验4130加热，其中添加了稀土母合金以及不同的稀土氧化物夹杂物。熔化后，将热量倒入龙骨块铸件中，以进行机械测试和金相检查。另外，采用单热电偶热分析系统检查每种热量的固化反应。进行了一些有趣的观察。首先，加热的机械性能和凝固组织是相似的，这与4130早期的工作相反。热分析表明，液相线和包晶层不会随母合金的添加而变化。夹杂物特征发现，最终铸件中的夹杂物与母合金中的夹杂物显着不同。这些夹杂物中的硫含量低或没有。基于此，作者得出结论，含硫稀土夹杂物是钢中可能的核。这项工作确定了4130晶粒细化中的几个重要因素。并非所有的稀土夹杂物都会导致细化，许多人得出这样的结论，即特定的稀土夹杂物通过充当异质核来细化钢的结构。含硫夹杂物可能是起这种作用的化合物。另外，包晶温度的变化似乎与细化的发生有关。这项工作没有改进，也没有包晶转变。文献中的其他工作观察到包晶温度的升高和细化的开始。包晶反应似乎在钢的凝固细化中起作用。作者得出结论，含硫稀土夹杂物是钢中可能的核。这项工作确定了4130晶粒细化中的几个重要因素。并非所有的稀土夹杂物都会导致细化，许多人得出这样的结论，即特定的稀土夹杂物通过充当异质核来细化钢的结构。含硫夹杂物可能是起这种作用的化合物。另外，包晶温度的变化似乎与细化的发生有关。这项工作没有改进，也没有包晶转变。文献中的其他工作观察到包晶温度的升高和细化的开始。包晶反应似乎在钢的凝固细化中起作用。作者得出结论，含硫稀土夹杂物是钢中可能的核。这项工作确定了4130晶粒细化中的几个重要因素。并非所有的稀土夹杂物都会导致细化，许多人得出这样的结论，即特定的稀土夹杂物通过充当异质核来细化钢的结构。含硫夹杂物可能是起这种作用的化合物。另外，包晶温度的变化似乎与细化的发生有关。这项工作没有改进，也没有包晶转变。文献中的其他工作观察到包晶温度的升高和细化的开始。包晶反应似乎在钢的凝固细化中起作用。