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

1

80 ℃

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

2

80 ℃

then the residuals are burned off at 500

7

00 ℃.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.