改质工艺对高强度低合金钢夹杂物特性的影响

利用300 t钢包炉工业试验研究了不同夹杂物改质工艺(包括未改质、稀土处理和钙处理)对铝镇静高强度低合金钢夹杂物特征的影响。结果表明,未改质处理炉次钢板中夹杂物为高铝含量的Al-Mg-Ca-O-S-Mn复合夹杂物,夹杂数量密度最小(仅为7.4和9.5个/mm2),但夹杂物平均尺寸大于3 μm,在轧板中检测到不小于20 μm的大尺寸夹杂数量多达0.1个/mm2。而稀土处理炉次钢板试样中夹杂物为球形La-Ce-O-S部分夹杂可能含少量Ca或Al。尽管夹杂数量密度最多达到32.5个/mm2,但夹杂平均尺寸最小(仅为2.3 μm),一个试样中未检测到不小于20 μm的夹杂,另一个试样中基本无不小于20 μm的大尺寸夹杂(仅0.01个/mm2)。钙处理炉次钢板中的夹杂物基本为球形夹杂,夹杂物成分为Ca-Al-S-O,部分夹杂可能含少量Mg或Mn,夹杂数量密度也较大,约为30个/mm2,夹杂平均尺寸为2.7 μm,稍大于稀土处理炉次,基本无尺寸不小于20 μm夹杂(0.01个/mm2)。高温共聚焦显微镜试验表明,稀土处理与钙处理的夹杂物在高温下不容易聚集成大尺寸夹杂物,而未改质炉次中的氧化铝由于与钢液界面张力大,容易聚集形成大尺寸夹杂物。

Influence of modification processes on inclusion properties of high strength low alloy steel

The influence of different inclusion modification processes (including unmodified, RE treatment and Ca treatment) on the inclusion characteristics of aluminum-killed high-strength low alloy steel was studied by the industrial 300 t ladle furnace. The results show that the inclusions were mainly irregular Al-Mg-Ca-O-S-Mn composed inclusion with high aluminium content. The inclusion density was the lowest (only 7.4 and 9.5/mm2), but the average size of the inclusions was more than 3 μm, and the number of large size inclusions not less than 20 μm was up to 0.1/mm2. The inclusions in steel plate sample by Re treated furnace are mainly spherical La-Ce-O-S with a small amount of Ca or Al. Although the maximum inclusion density is 32.5/mm2, the average inclusion size is the smallest (only 2.3 μm). No inclusions less than 20 μm were detected in one sample, and almost no large inclusion(≥20 μm) was detected in the other sample (only 0.01/mm2). The inclusions in the steel plate of the Ca treated furnace were almost spherical inclusions. The inclusions were mainly Ca-Al-S-O. Besides, partial inclusions may contain small amounts of Mg or Mn. And the number of inclusions is also large, about 30/mm2. The average size of inclusions is 2.7 μm, slightly larger than that of the rare earth treatment furnace, and basically there was no inclusion with size not less than 20 μm (0.01/mm2). The high temperature confocal microscopy tests show that the inclusion treated with rare earth and calcium is not easy to aggregate into large size inclusions at high temperature, while the alumina in the unmodified furnace is easy to aggregate into large size inclusions due to the high interface tension with liquid steel.The inclusions in the steel plate of the Ca treatment furnace were basically spherical inclusions. The inclusions were composed of CaS and calcium aluminate. And the number of inclusions was also large, about 30/mm2. The average size of inclusions was 2.7 μm, slightly larger than that of the RE treatment furnace, and basically there was no inclusion with size not less than 20 μm(0.01/mm2). The confocal laser scanning microscopy results showed that the inclusions treated with rare earth and calcium were not easy to aggregate into large sized inclusions at high temperature. Al₂O₃ in the unmodified furnace was easy to aggregate into large sized inclusions due to the high interface tension with liquid steel.