型芯热气流硬化工艺研究

提出并研究了一种型芯硬化新工艺，其工艺过程是将燃烧燃料产生的热气流或加热的气体强制导入型芯内部，利用气体携带的热量和(或)二氧化碳硬化型芯。理论计算及实验研究结果表明，采用该工艺可以大幅度提高生产率、降低能耗及降低生产成本。该工艺可用于各类烘焙硬化和气体硬化型芯的硬化。     

关于冷硬呋喃树脂砂硬化过程影响因素的初步认识

本文是以大量的试验和对现场的调查为依据,对影响硬化过程的下列因素:催化剂的种类和加入量,环境温度和湿度,树脂的类型,原砂的性质等进行了分析研究之后总结而成的。在一定的温湿度条件下,随着催化剂加入量的增加,硬化速度加快而强度却存在一个“峰值”,因此必须根据型芯的工艺和生产率的要求来权衡硬化速度和型芯强度的取舍或兼顾,以选择合适的催化剂加入量。掌握温度变化和催化剂的加入量,以控制硬化速度是冷硬呋喃砂造型(制芯)工艺中的关键之一。气溫低、湿度大时,硬化速度变慢,型芯强度也受到损失。本文还就树脂的类型和原砂的性质对硬化过程的影响也作了论述。     

CO_2硬化时间及其自动控制

水玻璃砂型(芯)采用CO_2硬化法是一种操作简便,节约材料、减少设备、提高效率的好方法,在生产中得到广泛应用,但是如何合理的控制硬化时间,以便在最大限度节约CO_2情况下得到高质量的铸型(芯)却未得到应有的重视.实践证明,硬化时间过长不仅白白浪费CO_2气体,也是型芯麦面发白,长毛,容易粉化、降低型芯强度的主要原因.为此,我们对各种不同型芯恰当的CO_2硬化时间进行了一些摸索试验,在此基础上设计制作了一种CO_2硬化时间的自动控制装置其使用效果良好,杜绝了CO_2的浪费现象,每吨水玻璃砂的CO_2耗用量较以前节约50%左右,而且使型芯硬化质量有所提高.     

吹风硬化芯砂用无机粘结剂

实际生产中,尤其在型芯较大的情况下,通过冷气流的作用硬化普通水玻璃型芯是不可能的,因为这种混合物的硬化原理是以脱水为基础。在这种情况下,要解决的主要问题就是要有一种令人满意的凝结速度,同时还必须使型芯具有良好的除砂性能。水玻璃是一种胶体溶液,它的硬化(凝结)主要     

复杂镁合金铸件的水溶性砂芯材料及高效清理技术研究

为了解决复杂镁合金铸件成形及其清理困难的问题,开展了高性能的水溶性型芯材料和高效的型芯清理技术研究,主要研究了微波加热硬化硫酸镁砂芯的性能和树脂砂芯高效清理工艺。结果表明:微波加热硬化水溶性硫酸镁砂芯,具有良好的常温强度、高温溃散性及水溶性,但抗吸湿性较差,硫酸镁砂芯铸造镁合金铸件时、砂芯铸后可在较短时间内水溶溃散;型芯的清理效率随着Na OH溶液浓度、超声波功率和受热温度的增大而增加,随着激振力的增加先增大后减少,当清理液为清水时,溶解振动清理工艺不能清理覆膜砂试样,而溶解超声波清理工艺仍然具有一定的清理效果。     

VRH法在新型CO2硬化树脂砂中的应用

研究了ＶＲＨ法在聚丙烯酸盐为基的新型ＣＯ２硬化树脂砂中的适用性及真空度，ＣＯ２吹气量和吹气保持时间，粘结剂加入量对型芯强度的影响。     

C0_2气体硬化水溶性型芯的研究

介绍了铸钢件用CO_2气体硬化水溶性型芯的主要成分、性能和影响因素.试验表明,浇注后的这种型芯,在50℃左右的水中浸泡15分钟即可全都溃溶脱芯,制得的铸件表面光洁无缺陷.     

高温合金空心叶片用陶瓷型芯概述

介绍了陶瓷型芯在航空发动机发展中的重要作用,从陶瓷型芯的原材料选择、型芯制备方法、型芯脱芯工艺等方面概述了陶瓷型芯的国内外研究现状,分析了氧化硅基陶瓷型芯以及氧化铝基陶瓷型芯制备过程中的关键难点。氧化硅基陶瓷型芯在温度超过1 550℃时易与高温合金发生化学反应,氧化铝基陶瓷型芯的化学稳定性较好,但难以脱芯。陶瓷型芯制备方法、烧结工艺、强化处理等是影响其性能的重要因素。     

熔模精密铸造的新工艺——“七一”型芯

所谓的”七一”型芯,就是水玻璃砂用氯化铵水溶液浸润硬化的芯子。过去,由于熔模精密铸造一直没有园满地解决型芯的问题,有些复杂的零件还是铸造不出来,这就使熔模精密铸造生产受到了一定的限制。采用“七一”型芯进一步完善了熔模精密铸造工艺,大大扩大了它的应用范围。     

酯硬化水玻璃砂的研究与应用

研究了酯硬化水玻璃砂性能的主要影响因素和工艺特点,提出了实用的型砂工艺.生产实践表明,酯硬化水玻璃砂具有流动性好、成型性好、自硬快、强度高、溃散性和型芯存放性好的特点,铸件质量较好且型砂成本低廉,具有较大的推广价值.     

超硬磨具用耐高温树脂结合剂的性能研究

采用甲基三甲氧基硅烷(MTMS)为改性剂,通过酯交换方式制备出有机硅酚醛树脂(SPF),并用傅里叶变换红外光谱分析、热重分析、力学性能测试等表征方法对SPF进行测定。结果表明: MTMS被成功引入SPF树脂结构中,且SPF耐热性能优良,受热质量损失10%时温度为462 ℃,较普通酚醛树脂(PF)的温度提高了90 ℃。与以PF为结合剂的超硬磨具相比,以SPF为结合剂制造的超硬磨具的力学性能明显提高,磨削比提高了51.1%;同时,后者的弯曲强度和冲击强度较前者的分别提高了14.2%和5.7%。      

Influence of paraffin wax characteristics on the formulation of wax-based binders and their debinding from green molded parts using two comparative techniques

The influence of paraffin wax characteristics on the formulation of wax-based binders has been examined. Four paraffin waxes (PW₁, PW₂, PW₃ and PW₄) were physically and molecularly evaluated and four binder systems 1–4 were formulated by mixing the major binder consisting of the paraffin wax with stearic acid (SA) and the minor binder; poly (ethylene-co-vinyl acetate) (EVA). Differential scanning calorimetric (DSC) and thermo gravimetric analysis (TGA) were used to evaluate the thermal characteristics of the pure binder components and the formulated binder systems. Also, the rheological properties of the formulated binder systems and feedstock were studied to measure their viscosities. Data indicated that the binder system no. 4 consisted of 35 wt.% EVA (containing vinyl acetate content of 9 wt.%), 62 wt.% of PW₄ and 3 wt.% of SA is the preferable binder for powder compression or injection molding. Also, in order to compare between the two debinding techniques (solvent evaporation–condensation and solvent immersion techniques) to extract the soluble binder components (paraffin wax and SA) completely from the green molded parts, powder compression molded parts were prepared and subjected to both techniques. It can be concluded that solvent immersion is a preferable technique as it saves the amount of solvent used as compared with the evaporation–condensation technique. Consequently, the solvent immersion technique using cyclohexane solvent at extraction temperature of 40 °C and after extraction time of 5 h are the most suitable conditions for extracting the major binder and SA constituents completely from the binder mixture in the green molded part.     

增塑粉末挤压成形新技术

以硬质合金材质体系为对象，针对目前主要的一类挤压成形设备－真空螺杆挤压机，开发出了一种增塑粉末挤压成形新技术。从理论上系统分析了成形过程的物理本质及粘结剂非等温脱脂机理与动力学，并推导出了一系列流变学材料函数。理论分析与实验相结合，开发出了一种多组元新粘剂设计与制备技术，优化了挤压工艺参数，制备了直径20mm的硬质合金挤压棒。     

Ni_3Al粘结相对Ti(C,N)基金属陶瓷组织性能的影响

采用粉末冶金法制备了Ni3Al做粘结相的Ti(C,N)基金属陶瓷,研究了添加不同含量Ni3Al粘结相的金属陶瓷的力学性能和显微组织并与Ni做粘结相的金属陶瓷进行了对比。结果表明,Ni3Al作粘结相的金属陶瓷综合力学性能总体上不如Ni做粘结相的金属陶瓷,随着金属陶瓷中Ni3Al含量的增加,其洛氏硬度值不断下降,而抗弯强度和断裂韧性却不断增加;显微组织分析表明,Ni3Al做粘结相的金属陶瓷同样具有芯环结构,Ni3Al可以控制环形相的厚度,抑制晶粒异常长大,使硬质相芯相棱角圆润。Ni3Al含量为30wt%左右的金属陶瓷能够兼顾硬度和抗弯强度等力学性能,此时的主要力学性能指标为:抗弯强度1 045±80 MPa,洛氏硬度HRA89.7±0.25,断裂韧性KIC为14.26 MPa·m1/2。     

粘结剂组成对粘结剂和喂料热性能的影响

研究制备了PW，BO，OP3大系列10种组成的粘结剂及相应10种W-Ni-Fe粉末与粘结剂的混合料。并采用热失重-差热分析(TGA-DTA)分析了粘结剂和喂料的热性能。研究结果表明，粘结剂组成对粘结剂和喂料的热性能如熔点、热分解温度和热分解曲线有很大的影响。通过此变化可以更为准确地确定不同粘结剂组成的喂料中的粘结剂脱除工艺和脱除方式。     

Technology and mechanism of a new protein-based core sand for aluminum casting

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｅｎｖｉｒｏｎｍｅｎｔａｌ ｐｒｏｂｌｅｍｓａｒｅｄｅｅｐｌｙｃｏｎ ｃｅｒｎｅｄｉｎｗｏｒｌｄｗｉｄｅ .Ｔｈｅｒｅｓｅａｒｃｈｅｓｏｆｍａｋｉｎｇｇｏｏｄｕｓｅｏｆｒｅｓｏｕｒｃｅａｎｄｃｌｅａｎｎｅｓｓｐｒｏｃｅｓｓａｒｅｂａｓｉｃｄｅｖｅｌ ｏｐｉｎｇｔｒｅｎｄｏｎｎｏｎｆｅｒｒｏｕｓｍｅｔａｌｓ[1] .Ｔｈｅｒｅａｒｅｍａｎｙｈａｒｍｆｕｌａｎｄｔｏｘｉｃｅｌｅｍｅｎｔｓｉｎｃｏｍｍｅｒｃｉａｌｌｙｕｓｅｄｒｅｓｉｎｂｉｎｄｅｒｓｆｏｒａｌｕｍｉｎｕｍｃａｓｔ…     

环保型无氮自硬呋喃树脂砂粘结剂的制作应用

介绍了基本上不含游离甲醛及游离苯酚含量很低的无氮自硬呋喃树脂砂粘结剂的制作方法和应用。这种粘结剂仍然使用甲醛、糠醇(呋喃甲醇)、苯酚等原料作为其合成树脂的主要材料,使用一种低分子物作为合成改性剂,采用适当的工艺制作而成,不改变树脂的性能,且树脂制作成本基本不变。该粘结剂的使用可在很大程度上降低铸件生产过程的游离甲醛和游离苯酚对生产环境和操作人员的污染和损害。     

A new starch-based binder for metal injection molding

A composition of starch and linear low-density polyethylene (LLDPE) was prepared as the binder and a mixture of this binder with 316L stainless steel powder was used to achieve a feedstock with 57% vol. powder loading. Rheological specifications of the binder and the feedstock were observed by means of capillary rheometery. Pseudo-plastic behavior of the binder and feedstock was investigated as a necessity in metal injection molding (MIM) process by proper flow characterization tests and their viscosity as the most significant flow characteristic was obtained in acceptable ranges. Thermogravimetric analysis (TGA) was carried out on feedstock in order to understand decomposition behavior of the binder components. In the next step, injection molding of the components was successfully conducted. Mechanical properties of compacts were then investigated through the triple point flexure test and the results showed that mechanical strength of specimens are very close to established ranges. The density of green parts was measured to assess the compaction of feedstock and it was achieved within the expected range for ferrous-based feedstocks. Debinding process was accomplished on compacted articles at three different temperature ranges including 70, 80 and 90 °C. Sintering process also was successfully accomplished on samples. For observing microstructures, the surface and cross section of specimens were compared before and after debinding as well as after sintering using scanning electron macrograph (SEM). Generally, this newly developed binder demonstrated a good potential for being utilized in MIM process.     

On the influence of binder content and binder composition on the mechanical properties of hardmetals

In order to achieve an understanding of damage mechanisms and the role of the binder phase in the fatigue behaviour of hardmetals, two series of hardmetals with 7, 15 and 27 wt% of Co and CoNiFe binder phases were investigated in a reversed bending stress apparatus. Microstructural investigations were carried out using SEM and TEM. Finite element simulations based on real microstructure cut-outs were used to analyse the stress and strain states. While both series of hardmetals exhibit inert strengths which depend strongly on the binder content, their fatigue behaviour is totally different. For the WC–Co grades, no significant influence of the binder content on the fatigue behaviour was found. In contrast to this, the fatigue behaviour of the WC–CoNiFe grades showed a clear dependence on the binder content. The microstructural investigations revealed that the mechanism of stacking fault formation and phase transformation in the Co binder phase, together with a stress concentration in the binder pools are responsible for the fatigue behaviour of the WC–Co grades. In WC–CoNiFe grades, no stacking faults or transformed zones were observed. In addition, the CoNiFe binder phase reveals a very ductile flow nature, which results in large plastically deformed zones in the binder phase.     

菜籽油脚与花生油脚改性为铸造用粘结剂研究

介绍一种以菜籽油脚和花生油脚为原料，通过脱水、缩合、氧化聚合、增强、增稠，改性制成的铸造用粘结剂。该粘结剂性能优于ＧＢ１２２１６－９０指标。已有三家工厂投产，不仅有较好的经济效益，而且消除了油脚对环境的污染。