【作者】 朱胤；

【导师】 闵小俊；

【作者基本信息】 四川大学 ， 材料加工工程， 2007， 硕士

【摘要】 针对以石英或熔融石英为骨料，水溶性磷酸盐为粘结剂，氧化镁为固化剂的熔模铸造用浇注成形自硬型芯材料的工艺性能和应用特点进行了详细的研究。考察了常用的硅基热压注陶瓷型芯的性能和生产工艺，将浇注成形自硬型芯与之相比较，对比研究了后者独有的性能和工艺特点。对于JX-3、JXR、JXR-2、JXR-3四种系列的磷酸盐浇注成形自硬型芯材料的性能进行了测试研究，在不同的焙烧温度、不同的硅溶胶浸渍强化次数下分别对试样进行处理，以型芯抗弯强度为主要考察目标，芯料耐水性、高温热变形量、烧成收缩率、密度等性能作为参考指标，分析比较了在型芯生产工艺中对型芯性能造成较大影响的各项因素。结果表明：在采用600℃预焙烧去除型芯中残余蜡料和水分后，型芯强度会变得较低，平均值1MPa左右。采用硅溶胶浸渍强化后，型芯强度可以得到大幅度提升，一次强化后提升最为明显，二次强化仍具有较大效果。在模拟随型壳焙烧(900℃)后，型芯强度变化不大，基本能够满足熔模铸造对型芯的强度要求。在经受模拟浇注铸件加热(1550℃)后，型芯残余强度比焙烧前有轻微上升，对溃散性影响不大，平均残余强度6～8MPa。型芯在1500℃高温下的热变形量不大，由于骨料的热膨胀系数差异，全熔融石英骨料的JXR变形量最小，全石英骨料的JX-3热变形最大。型芯平均烧成收缩率1％左右，600℃预焙烧前后密度差低于0．2g/cm~3，具有较强的耐水性，适用于热水和蒸汽脱蜡。然后进行了芯料焙烧后未强化强度、强化强度及残余强度测试，对比了JXR在加入不同的混合液体后的强度性能。还进行了浆料流动性和悬浮稳定性、填充料焙烧后强度、高温稳定性及残余强度测试；对比了JX-2、JXR-2芯料和针对填充用途优化的JXR-3芯料性能。实验表明，与用水调拌的型芯相比，加入硅溶胶或磷酸溶液都能提高型芯强度，且磷酸溶液浓度越高，型芯强度提升幅度越大。但磷酸溶液会影响浆料的流动和固化，对强度没有特殊要求时推荐使用硅溶胶。在满足填充工艺所要求的浆料高流动性条件下，JXR-3的性能优于JX-2和JXR-2，具有足够的工作时间和悬浮稳定性、较高的焙烧后强度和高温稳定性。对比研究了水、硅溶胶和磷酸溶液三种浆料混合液体，结果表明，硅溶胶的效果最优。针对浇注成形型芯脱模容易的特点，研究了其在熔模铸造生产上的拓展应用。选择铸造了型芯难于脱模的离心式多叶片叶轮。该铸件由于具有扭曲叶片，如采用传统的热压注成形法陶瓷芯不能脱模，用JXR系列浇注成形磷酸盐自硬芯料的浆料浇注叶轮芯解决了上述工艺问题。随后系统研究了为避免熔模铸件内腔鼓胀和夹铁缺陷，用JX和JXR系列浇注成形磷酸盐自硬芯料的浆料填充型壳狭窄空腔的工艺问题。铸件浇注实验表明，JXR芯料能够低成本地用于生产局部具有复杂、狭窄内腔的铸件的各种型芯。JXR-3浆料由于流动性好，特别适合于型壳狭窄空腔填充，能成功消除熔模铸件内腔的夹铁和鼓胀缺陷。实际铸件生产实验表明浇注成型自硬芯料成形工艺实际可行，且易操作、不需要专用设备和成本较低，具有很好的应用前景。更多还原

【Abstract】 Technological performances and application characteristics of phosphate self-setting & formed by pouring materials were investigated, which based on quartz or fused-silica and regarded water-solubility phosphate as binder, regarded oxidize magnesium as solidify pharmaceutical. Performance and production technics of silica-base ceramic core which formed by hot-pressing were investigated. Phosphate self-setting core has been compared with it about their particular performances and technological characteristics.Performance of four series phosphate self-setting materials, JX-3, JXR, JXR-2 and JXR-3, have been tested and investigated. Having been baked under different temperature and strengthened by dipping silica sol, strength of the cores was regarded as the main objective parameter. Amount of deformation under high temperature, sintering shrinkage and density were regarded as referential index. Various factors which impacted performance of the core in making process were analysed and compared.The result shows that, strength of the core will be falling after baking in 600℃, because the wax and water has been wiped off completely in core. The average value is about 1MPa. Strength of the core can be strengthened a lot by dipping silica sol, especially in the first time. After simulating baking with shell molds in 900℃, strength of the core change little. After simulating baking under casting temperature in 1550℃, residual strength of the core will increase a little. The average value is about 6～8MPa. Under high temperature in 1500℃, amount of deformation of the core is a little. Because of the different heat expansion coefficient of aggregate, JXR which all based on fused-silica is the min, JX-3 which all based on quartz is the max. The average value of shrinking percentage after baking is about 1%. Density variation after baking in 600℃is under 0.2g/cm~3. The core has resistance to water, so it can be dewaxed by hot water or steam.Systematic strength testing of core after baking have been carried out, such as: unstrengthened strength, strengthened strength and residual strength. Strength performance of JXR materials have been compared, which have been mixed with different slurry mixing liquid. Systematic research has been carried out, including: slurry fluidity and suspending stability, strength after baking, high temperature stability and residual strength of the filled material. JX-2 and JXR-2 have been compared with JXR-3 which has been optimized for filling function. The result shows that, when mixed with silica sol or phosphoric acid solution, strength of core is superior to the one which mixed with water. Strength of core become higher with the increase of concentration of phosphoric acid solution. But phosphoric acid solution will impact slurry fluidity and self-setting. Silica sol is recommended in actual production when it doesn’t need special strength. When slurry flow ability is high enough to satisfy filling function, the performance of JXR-3 is superior to JX-2 and JXR-2. JXR-3 has enough bench time and suspending stability, high strength after baking and good high temperature stability. Three kinds of slurry mixing liquid, water, silica sol and phosphoric acid solution have been compared and evaluated, and it is concluded that silica sol is the best.Based on easy to demould characteristic of phosphate self-setting material, further application in investment casting has been investigated. To verify its practicability, we try to cast centrifugal & multiple-vane impeller, the core of it is difficult to demould. Because the casting have twisted blade, ceramic core can’t demould in conventional hot-pressing process. To solve mentioned above technical problem, we use JXR series phosphate self-setting material to form the impeller core. To avoid casting swelling and metal-leaking defects in the internal cavity of an investment casting, systematic research has been carried out, on technologic aspects that using the JX and JXR series phosphate self-setting material slurry to fill up the narrow cavity of shell molds. The actual casting making process shows that JXR material can be used in forming the cores of casting with low cost, which partial have complex shape and narrow cavity. Because it have good slurry flow ability, JXR-3 material is fit for filling up the narrow cavity of shell molds, can make a decisive effect to avoid casting swelling and metal-leaking defects.Actual cast product experiment shows that the forming technics of phosphate self-setting & formed by pouring materials is feasible. It easy to operate, doesn’t require special equipment, can be used in making all kinds of complex core and filling up shell molds with low cost. It have great application prospect.更多还原