SLS模料特性及熔模铸造工艺研究

Pattern-properties of SLS and Investment Casting

选择性激光烧结（SIS）在熔模铸造中已得到广泛的运用，但其模料为高分子化合物，熔化温度高，熔体粘度大，不利于脱蜡，易使铸件产生夹渣。研究了SIS模料的特性，并根据模料特性设计了结壳脱蜡工艺：于250～280℃下保温，使大部份蜡料流出，而后升温至500～700℃烧失残留部分。在实际生产中，由于浇注系统和零件简单部位用低温模料制作，而用SIS蜡料制作零件的复杂部位，所以在设计中还应考虑蜡料的脱出顺序：先在较低温度下脱出低温蜡料，再升温脱出SIS蜡料。在分析运用SLS蜡模浇注复杂铸件易产生夹渣等问题的原因之后，提出在蜡模易积渣的部位和凸台处设置出气冒口及排渣冒口，可使蜡料脱出干净，从而解决铸件夹渣等问题。将以上工艺运用于实践，成功浇注出了汽车排气管、大型不锈钢泵轮等复杂精密铸件。

Highly polymerized compound pattern-materials in SLS pattern is un-favorable for dewaxing and easily generating entrapped-slag in the investment castings due to high melting point and high viscosity.The pattern-materials properties in SLS pattern has been investigated,including melt viscosity temperature of 160~180 ℃,100 Pa s melt viscosity temperature of 230 ℃,initial decomposed temperature of 310.48 ℃ and fully decomposed temperature of 476 ℃ as well as ash content of 0.307%.Based on the pattern-materials properties,the process of designed shell-making and dewaxing is as follows:majority wax-materials is removed at about 250~280 ℃,then the residuals are burned off at 500~700 ℃.The sequence of dewaxing should be considered in the practice due to the pattern always assembled with simple parts and gating system with low melting point wax and SLS wax.The low melting point wax pattern is firstly dewaxed at a lower temperature,then SLS pattern is dewaxed at a higher temperature.Entrapped-slag in the investment castings can be eliminated by setting exhausted riser and exhausted-slag riser in concave and slag-collection position of pattern to fully remove wax based on analysis of origination of entrapped-slag in SLS pattern complex parts.Exhausted pipe in the car and large stainless steel pump wheel in investment casting have been successfully produced by using above-mentioned technology,realizing desirable effects.