Properties of sodium silicate bonded sand hardened by microwave heating

The sodium silicate bonded sand hardened by microwave heating has many advantages,such as low sodium silicate adding quantity,fast hardening speed,high room temperature strength,good collapsibility and certain surface stability.However,it has big moisture absorbability in the air,which would lead to the compression strength and the surface stability of the sand molds being sharply reduced.In this study,the moisture absorbability of the sodium silicate bonded sand hardened by microwave heating in different humidity conditions and the effect factors were investigated.Meanwhile,the reasons for the big moisture absorbability of the sand were analyzed.Some measures to overcome the problems of high moisture absorbability,bad surface stability and sharply reducing strength in the air were discussed.The results of this study establish the foundation of green and clean foundry technology based on the microwave heating hardening sodium silicate sand process.

Recycling water glass from wet reclamation sewage of waste sodium silicate-bonded sand

Wet reclamation of waste sodium silicate-bonded sand produces much alkaline sewage and causes pollution. Recycling water glass from wet reclamation sewage of the waste sodium silicate-bonded sand can solve pollution issues and generate economic benefits. In this work, the wet reclamation sewage was filtered, and the filtrate was causticized with a quicklime powder to produce a lye. The effects of causticization temperature, causticization time, and the amount of quicklime powder on the causticization rate were studied. The lye was used to dissolve the silica in the filtration residue to prepare a sodium silicate solution. The effects of the mass of filtration residue, dissolution temperature, and dissolution time on sodium silicate modulus were studied. Finally, the recycled water glass was obtained by concentrating the sodium silicate solution, and the bonding strength of the recycled water glass was tested. The results showed that the causticization rate could be improved by increasing the amount of quicklime powder, causticization temperature, and causticization time, and the highest causticization rate was above 92%. Amorphous silica in the filtration residue dissolved in the lye. Increasing the amount of the filtration residue, dissolution temperature, and dissolution time could improve the sodium silicate modulus. The bonding strength of the recycled water glass was close to that of commercial water glass. The recycled water glass could be used as a substitute for the commercial water glass.

Mechanism of Increase in Strength of Sodium Silicate-bonded Sand by Silica Sand Surface Modified in High Temperature.

With the aid of XRD, SEM and EDS etc., there is absorbed film on sand grain surface, high temperature modify makes the film sintered firmly on sand grain surface. Thus it changes physical and chemical characteristics of the film and sand grain surface, improves the wetting properties greatly, makes the fracture features of bonding bridge change from the adhesive to the cohesive and raises the strength of sodium silicate-bonded sand.

Influence of Temperature and Water Vapour Pressure on Drying Kinetics and Colloidal Microstructure of Dried Sodium Water Glass

Industrially produced sodium water glasses were dried in climates with controlled temperature and humidity to transparent amorphous water containing sodium silicate materials. The water glasses had molar SiO2:Na2O ratios of 2.2, 3.3 and 3.9 and were dried up to 84 days at temperatures between 40&degC and 95&degC and water vapour pressures between 5 and 40 kPa. The materials approached final water concentrations which are equilibrium values and are controlled by the water vapour pressure of the atmosphere and the microstructure of the solids. The microstructure of the dried water glasses was characterized by atomic force microscopy. It has a nanosized substructure built up by the silicate colloids of the educts but deformed by capillary forces. In the final drying equilibrium, the water vapour pressure of the atmosphere in the drying cabinet is equal to the reduced vapour pressure of the capillary system built up by the silicate colloids. Their size scale can be explained by the deformation of colloidal aggregates due to capillary forces.

原砂对新型改性水玻璃型砂溃散性的作用机理

研究了原砂对水玻璃型砂溃散性的影响 ;通过扫描电镜观察了水玻璃型砂高温焙烧后的粘结桥形状和砂粒表面特征 ,用电子探针和X射线衍射分析了砂粒表面膜的主要生成物的成分和形态 ,揭示了不同品位的石英砂与水玻璃粘结剂发生高温反应后残留强度高低不同的原因 .研究结果表明 ,都昌砂高温下与水玻璃反应生成了高熔点的蜂窝状钾长石 ,导致型砂的残留强度很低 ;而海城砂则生成了低熔点的物质 ,使得型砂的残留强度很高 .因此 。

硅砂表面高温改性提高水玻璃砂强度的机理

Ｘ－射线衍射（ＸＲＤ）、扫描电镜（ＳＥＭ）、能谱（ＥＤＳ）等的研究表明，硅砂表面存在吸附膜．高温改性使吸附膜被牢固烧结在砂粒表面，改变了吸附膜和砂粒表面的物理和化学特性，大大改善了湿润性，使粘结桥的断裂形式从附着断裂向内聚断裂转化，提高了水玻璃砂的强度．

硅溶胶—水玻璃复合涂料在精铸生产中的应用

介绍硅溶胶涂料的配制过程及复合制壳工艺 ,对使用结果作了简要分析。

水玻璃砂微波加热工艺及工程应用方案研究

系统测试和分析了水玻璃模数Ｍ、加入量、微波加热工艺对微波固化水玻璃砂抗拉强度σｂ 和高温烘焙后的残留强度σｂｃ 的影响规律。发现水玻璃砂微波加热时间过长抗拉强度有降低趋势。提出了水玻璃砂微波加热工艺的工程应用方案。

聚乙烯醇对二次微波硬化水玻璃砂的抗吸湿性影响

通过红外光谱和扫描电镜等测试方法,对普通水玻璃和添加聚乙烯醇后的水玻璃的官能团及组织进行了分析,添加聚乙烯醇后的水玻璃砂样抗吸湿性高于普通水玻璃砂样,当聚乙烯醇加入量为水玻璃质量的3%时,砂样的抗吸湿效果最佳。样品的红外图谱表明,添加聚乙烯醇水溶液后的水玻璃砂中出现了新的基团Si-O-C。扫描电镜分析表明,添加聚乙烯醇后,水玻璃膜均匀、完整地覆盖在砂粒表面,粘结桥中裂纹减少,断裂面以内聚断裂为主。

气体容量法测定水玻璃砂中碳酸盐含量

水玻璃再生砂中的碳酸盐对其性能有较大影响,需进行定量分析。用0.50mol/L盐酸分解10~50g试样后,用量气管收集并测量反应生成的二氧化碳气体体积,反应时间控制在18min以上,当量气管液面高度在3~5min内不变时为反应终点,根据二氧化碳气体体积计算碳酸盐含量,建立了气体容量法测定水玻璃砂中碳酸盐含量的方法。方法用于水玻璃砂模拟样品中碳酸盐含量的测定,测定值与理论值一致,相对标准偏差在0.20%~0.80%之间;用于水玻璃旧砂和再生砂中碳酸盐含量的测定,测得结果与滴定法基本吻合,相对标准偏差不大于0.91%。

水玻璃再生砂中碳酸氢盐和碳酸盐的含量测定

由于缺乏各组分含量的测试方法,水玻璃再生砂的性能一般采用总碱量评价。提出了一种采用气体容量法测定水玻璃再生砂中碳酸氢盐和碳酸盐含量的方法。将氯化钙溶液滴入水玻璃砂试样,反应时间控制在15 min以上,用量气管测量生成的二氧化碳体积,由气体状态方程求得碳酸氢盐含量。将盐酸溶液滴入试样,反应时间控制在20 min以上,测量生成的二氧化碳体积,求得碳酸盐含量。该方法用于水玻璃砂样品中碳酸氢盐和碳酸盐的含量测定,测定值与理论值一致,RSD小于0.9%;用于水玻璃旧砂和再生砂中碳酸氢盐和碳酸盐的含量测定,测定值与滴定法测量值吻合,RSD小于1.0%。

我国熔模精密铸造的历史回顾与发展展望

概述了熔模精密铸造的特点及在我国的整体发展现状。按照不同产品类别追溯了我国熔模铸造发展的历史、技术进展、行业现状。详细介绍了通用硅溶胶型壳工艺、钛合金熔模铸造工艺、铝合金熔模铸造工艺、石膏型熔模铸造工艺、水玻璃型壳工艺等多种工艺方法以及熔模精密铸造在航空、航天以及一般商用铸件上的应用。指出了我国熔模精密铸造与工业发达国家之间存在的差距,并对我国熔模精密铸造行业的发展提出了几点建议。

水玻璃旧砂再生脱膜率评价方法初探

现有的水玻璃旧砂再生脱膜率采用砂中Na2O总含量进行评价,一般通过酸碱滴定方法直接测定。水玻璃旧砂表面粘结膜主要有碳酸钠、草酸钠、乙酸钠及模数不同的水玻璃等组分,其主要化学组成随固化方法和工艺的不同,有着明显的差异,各组分对再生砂性能的影响还未获得统一认识,且脱膜过程中各组分的脱除程度也不一样。可见,仅用Na2O总含量评价水玻璃砂再生脱膜率不全面,也不能完全反映再生砂的性能。针对现有测试Na2O的方法存在的准确度低等问题,文章概述了已有改进的Na2O测试方法,并给出了改变现有再生脱膜率评价方法的建议,主要包括在系统研究残留粘结膜各组分对再生砂性能影响的基础上,并结合再生方法的特点,综合考察粘结膜各组分的脱除程度,以实现再生脱膜率和再生砂的综合性能全面和准确的评价。

水玻璃砂芯微波固化用模具材料

分析了砂芯微波固化用模具材料应具备的性能 ,测试并分析了树脂模具和陶瓷模具的微波吸收性和穿透性。结果表明 ,塑料模具和陶瓷模具都可用于水玻璃砂芯的微波固化。塑料模具的优点是强度高、韧性好、易于制作 ,陶瓷模具的优点则是耐热性好、耐用性好。

石英砂高温改性对酯硬化水玻璃砂性能的影响

通过对由平度人造石英砂、围场砂和梧龙砂高温改性后混制的水玻璃砂铸造工艺性能的研究,发现在环境温度和湿度相同的条件下,随焙烧温度升高,型砂的抗拉强度提高;相同的焙烧温度下,高温焙烧对不同原砂的改性作用不同;对三种原砂而言,其抗拉强度还受到环境湿度和温度的影响,在相同的环境温度下,湿度越大,水玻璃砂的抗拉强度越低。提出了石英砂高温改性对酯硬化水玻璃砂性能的影响规律。

一起双氧水储罐爆炸事故的原因调查

错将水玻璃加到双氧水中,致使双氧水储罐爆炸,炸飞的罐体挂断供电线路,全厂断电停产23 h,经济损失100多万元,无人员伤亡。

水玻璃砂的干法再生

水玻璃砂的干法再生主要是解决溃散性和脱膜率问题。采用各种方法 ,降低水玻璃加入量是提高水玻璃砂溃散性的有效途径。把水玻璃砂加热到一定温度 ,使水玻璃膜变脆 ,然后进行机械再生 ,可以获得较好的再生效果。

电感耦合等离子体原子发射光谱法测定水玻璃再生砂中残余氧化钠含量

采用电感耦合等离子体原子发射光谱法测定水玻璃再生砂中氧化钠含量。研究了应用电感耦合等离子体原子发射光谱法测定水玻璃再生砂中氧化钠的提取方法、工作条件的选择、分析线的选择及干扰的消除。通过准确度和精密度试验,验证了方法的准确性和可靠性。

水玻璃砂微波加热过程温度场测试与分析

通过系统测试和分析水玻璃砂在微波加热过程中的温度场，揭示了水玻璃砂微波加热的快速升温及型芯内外同时升温等特性。通过实验和分析，探讨了形成这些特性的原因。提出了微波加热过程中水玻璃砂型芯的升温主要依赖于水玻璃对微波的吸收的观点。

工艺参数对微波硬化水玻璃砂溃散性影响的试验研究

采用微波加热技术硬化水玻璃砂，用电阻炉加热模拟型芯在铸造过程中的受热情况，测试砂型试样的溃散性，分析水玻璃加入量和水玻璃模数对微波硬化水玻璃砂残留强度的影响规律。结果表明，在微波加热功率为539W、微波加热时间为20min、电阻炉中保温时间为10min的条件下，当水玻璃加入量在5．0％～2．0％范围内，每下降1.0％时，砂型试样的残留强度平均值下降约5．0％；水玻璃的模数由2．3增加到2．5时，砂型的残留强度平均值有所降低。采用微波加热新工艺提高了水玻璃的粘接效率，降低了水玻璃的加入量，改善了水玻璃砂的溃散性。