铸钢件气孔形成机理分析及预防措施

通过对气孔缺陷实例进行理论分析与探讨,得出铸钢件气孔产生原因主要分3种类型:脱氧不良及二次氧化,使钢液含氧量过高,在凝固降温过程中,碳氧平衡被破坏,发生碳氧反应,生成CO反应性气孔;炼钢氧化期后和浇注过程中,水蒸气对钢液的二次氧化,使钢液大量吸氢。在钢液凝固期间,氢因溶解度急剧降低而析出,形成析出性H2气孔;石灰石砂芯在高温下分解产生大量CO2气体不能及时排出,产生侵入性气孔。针对不同气孔形成机理提出了防止措施,有效地消除了气孔缺陷。

Investigation on the Formation Mechanisms and the Prevention of Blowholes in Steel Castings

There are three types of causes that result in blowholes in steel castings through theoretically analyzing actual blowhole defects: Poor deoxidizing and secondary oxidizing of molten steels lead to high oxygen content,the balance between carbon and oxygen is destroyed and carbon-oxygen reaction occurs,by which reactionblowholes of CO are produced during solidification and cooling of steels.After oxidizing period,steels are oxidized again by water vapor during pouring,which results in high hydrogen content in steels.Hydrogen is separated from steels as solubility of the hydrogen in steels dropped sharply and the blowholes of H_2 formed during the solidification of castings.Limestone sand cores are decomposed into a great amount of CO_2 gas at elevated temperature.If the gases cannot be removed in time they will form the intrusive blowholes.Prevention measures are proposed on the basis of different formation mechanisms of blowholes and blowhole defects can be eliminated effectively.