黄壤土砂铸型与铸件界面烧结层的力学行为

Mechanical Property of the Sintering Layer at the Interface of Natural Yellow Clay-bonded Sand Mould and Iron Casting

黄壤土天然粘土砂湿型铸造工艺应用于铸铁生产,能有效预防粘砂缺陷、提高铸件表面质量,同时具有成本低、污染小、效率高的综合优势。这种工艺与普通的湿型铸造工艺相比,最大的区别在于,它会在铸型与铸件之间形成一层致密的烧结壳。这层烧结壳能抵挡住金属液的冲刷和渗透,在金属凝固后能牢固的粘附在铸件表面,可实现高温打箱,而不至于使铸件冷却过快、表面硬度过高,从而提高生产效率;在室温时,它又能轻易地从铸件表面脱落,减轻清砂工作量。为深入了解这一现象,开展对黄壤土天然粘土砂烧结层的高温和室温力学性能的研究,结果表明,烧结层试样在高温下具有很好的塑性,随着温度的降低,塑性减小、抗压强度提高,在室温下表现出明显的脆性。这说明烧结层力学性能的变化与其在铸造过程中的行为正好吻合。

Natural yellow clay-bonded green sand casting process is suitable for producing iron casting.It can avoid burnt-on sand and improve the casting surface quality,and has the comprehensive advantages of low cost,less pollution and high efficiency.The big difference between natural yellow clay bonded green sand process and usual clay bonded green sand processis that the former can form a dense sinter skin at the interface of casting and mold,which can resist the scouring and infiltration of liquid metal,and can firmly adhere to the casting surface after the liquid metal is solidified.So,elevated temperature knockout can be realized without too fast cooling of casting and too high surface hardness,thus improving production efficiency.At room temperature,it can easily shed from the casting surface,thus reducing the amount of sand-removing work.In order to understand this phenomenon in depth,the mechanical performances of sinter layer of natural yellow clay-bonded sand at elevated and room temperatures are investigated.The results show that the sinter layer sample has excellent plasticity at elevated temperature,and with the decreasing of temperature,the plasticity decreases and the compression strength increases.At room temperature,it exhibits obvious brittleness.This accounts for the agreement of the variation of mechanical performance of sinter layer with its behavior in the casting process.