For some Si-killed steel grades, it is desirable to obtain calcium or manganese silico-aluminate inclusions with low-melting temperatures, which form a glassy phase at low temperatures and are easily elongated and reduced in size during hot rolling. However, these inclusions sometimes exhibit coarse crystallization changes during heat treatment before hot rolling, which affects the rheological properties of inclusions. In the present work, the composition, morphology, and size of inclusions in Si-killed spring steel by two types of bloom-heating processes were investigated. It was found that most oxide inclusions in the billet were glassy and had good rolling deformability when a 1523 K × 150 minutes bloom-heating process was adopted. However, when a heating process of 1373 K × 40 minutes was adopted, the oxide inclusions had a high proportion of crystallization, and most of them had poor rolling deformability. Due to the influence of different crystallization ratios and crystal sizes of inclusions, the maximum inclusion sizes of the corresponding wire rods were 20 and 35 μm, respectively. On the basis of these results, it was suggested that to improve the inclusion control of Si-killed spring steel, the heating temperature and time before blooming should be selected in the high-temperature region above the nose temperature of the inclusion TTT transformation curve.

对于一些硅镇静钢种，希望获得具有低熔点的钙或硅铝酸锰夹杂物，它们在低温下形成玻璃相，并且在热轧过程中容易伸长和减小尺寸。但这些夹杂物在热轧前的热处理过程中有时会出现粗大的结晶变化，影响夹杂物的流变性能。在目前的工作中，研究了两种钢坯加热工艺在硅镇静弹簧钢中夹杂物的成分、形态和尺寸。采用1523 K×150 min的大方坯加热工艺发现，钢坯中的氧化物夹杂物大部分呈玻璃状，具有良好的轧制变形能力。然而，当采用 1373 K × 40 分钟的加热过程时，氧化物夹杂物结晶比例高，大部分轧制变形性较差。由于受不同结晶率和夹杂物晶体尺寸的影响，相应盘条的最大夹杂物尺寸分别为20和35微米，分别。在此基础上，建议提高硅镇静弹簧钢的夹杂控制，初轧前的加热温度和时间应选择在夹杂TTT转变曲线鼻尖温度以上的高温区域。