碱性酚醛树脂熔融陶瓷砂烧结层的形成机理与解决对策

Formation Mechanism and Resolution of Sintered Layers of the Alkaline Phenolic Resin Fused Ceramic Sand

碱性酚醛树脂熔融陶粒砂铸造是一种生产高品质铸钢件的优异工艺,但是该工艺存在型砂烧结导致清砂困难的问题。为此,以铸钢磨盘的铸造为例,采用微观形貌分析、成分分析、烧结对比试验,研究了碱性酚醛树脂熔融陶粒砂在铸造过程中烧结成壳的机理。研究发现,碱酚熔融陶粒砂烧结成壳归因于高温作用使得陶粒砂之间形成烧结颈将砂粒粘结在一起。烧结颈主要是通过陶粒砂表面元素向砂粒之间的凹角处堆积生长而成,其中K和Si元素更易向凹角处扩散,形成低熔点钾硅酸铝盐。碱性酚醛树脂在陶粒砂表面引入较高含量的K碱,进一步促进了烧结颈的形成。采用“化学法+热法”再生技术能够大幅度降低旧砂表面残留的K和Na等物质,从而降低旧砂复用时的烧结倾向。

Alkaline phenolic resin fused ceramic sand casting is an excellent process for producing high-quality steel castings,but it has the tendency of sintered to shell,which makes sand cleaning difficult.Based on the casting of thick grinding plate steel castings,the sintering mechanism of the alkaline phenolic resin ceramic sand in the casting process was studied through micro morphology analysis,composition analysis and sintering comparison test.It is found that the sintering shell of the ceramic sand with alkaline phenolic resin was mainly due to the formation of sintering neck between sands under high temperature.The sintering neck was mainly formed by the accumulation and growth of surface elements to the concave corner between ceramic sands,in which K and Si elements were easier to diffuse to the concave corner to form low melting point potassium aluminum silicate.Among them,the alkaline phenolic resin introduced a high content of K on the surface of the ceramic sand,which further promoted the formation of the sintering neck.“Chemical+thermal”regeneration technology greatly reduced the residual K,Na and other substances deposited on the surface of the used sand,consequently reduced its sintering tendency during reuse.