砂芯高温膨胀对气缸体曲轴箱壁厚的影响

介绍硅砂的高温膨胀过程.以缸体非加工部位壁厚为例,通过试验说明硅砂高温膨胀引起的砂芯膨胀会减薄铸件壁厚,同时说明采用壁厚补贴的方法可以弥补砂芯高温膨胀对引起的壁厚减薄,使铸件壁厚达到设计要求.     

砂芯高温膨胀对缸体曲轴箱隔板壁厚的影响

简述了硅砂的高温膨胀过程,分析了其对铸铁件壁厚的影响,提出在浇注过程中砂芯的高温膨胀会使铸件的非加工壁厚减小。通过气缸体曲轴箱的浇注试验,证明了硅砂高温膨胀的存在,在工艺设计过程中增加壁厚补正量可以抵消砂芯表面的热变形,进而控制砂芯高温膨胀对缸体曲轴箱隔板非加工壁厚的影响。     

下箱体铸造工艺设计及数值模拟

下箱体为球墨铸铁件,在设备运行过程中承受交变的冲击载荷,箱体要求抗压测试,组织致密度要求高;铸件内部空腔较复杂,壁厚不均匀,最大壁厚80 mm,最小壁厚20 mm。对下箱体铸件进行工艺性分析、造型材料选择、浇注系统及砂芯设计等,采用组合砂芯解决内腔较复杂问题,通过在适当位置设置冒口的方法,使铸件均衡凝固,以达到零件致密度要求。设计过程使用UG三维造型软件进行三维建模,运用Pro CAST软件对铸件充型及凝固过程进行数值模拟,根据模拟结果对现有工艺方案进行了优化。     

湿拼砂芯在大型立柱上的应用

XH716D-2A101立柱长1 850 mm;宽1 380 mm;高630 mm;最大壁厚50 mm;最小壁厚20mm;材质HT300,铸件重1 800 kg,该件有长1 525 mm,宽70 mm的导轨两条,表面粗糙度Ra25 μm,侧面Ra6.3μm.该件不允许有砂眼、气孔、裂纹、疏松等铸造缺陷,人工时效后的硬度不低于180HB.在铸造生产中存在以下问题:型腔内砂芯大(砂芯形状见图1),曾考虑清砂工作的方便,腔内用一只砂芯形成,实际操作中、造芯操作很不方便,因为芯壳太大,刮砂面的肋条要全部捂出,砂芯的紧实度受到严重影响,铸件肋条毛糙、粘砂、烧结等缺陷经常发生,给清砂带来困难.     

树脂砂铸造床身铸件热裂纹的防止

床身铸件毛坯尺寸1910mm×960mm×1120mm,最大壁厚25mm,最小壁厚15mm,重量为2100kg,材质为HT300,导轨淬火.采用呋喃树脂砂造型,15t工频感应电炉熔炼.铸件清砂后经常发现在斜导轨底部支撑肋与油盘搭接处有热裂纹缺陷,裂纹断口处呈氧化色,宽度约1～2mm.曾用提高碳当量,提高砂芯退让性,壁厚处加石墨冷铁等措施来改善热裂纹缺陷,均未得到有效解决,铸件焊修率达90%以上,严重影响产品质量.     

液压泵体铸件坭芯的二次辅助射砂工艺

液压泵体由于铸件呈中空型结构,有多处油口,生产时制作的覆膜砂芯中间腔体尺寸较大,四周油口砂芯芯头的尺寸较小,砂芯结构壁厚不均,局部非常厚实,易出现覆膜砂加热不均,使得砂芯生产难度较大。采用预先射制一个壁厚随形小5~10 mm的辅助芯,放入模具中二次射砂,最终制作出一个整体砂芯。该整体砂芯二次射砂时壁厚均匀,模具加热管布置容易,砂芯固化均匀透彻,表面品质好,强度和尺寸精度高。减小了生产难度,提高了生产效率和铸件品质。     

水玻璃砂芯温度分布与溃散性关系的研究

随着铸件壁厚、形状和浇注温度等的不同,砂芯温度场分布也不尽相同。在设计水玻璃砂溃散剂时,应以砂芯温度场分布为出发点,针对不同的温度场分布设计出不同的溃散剂,以取得好效果。砂芯的温度场可用计算机数值模拟,本研究中模拟的圆筒形简单铸件与现场实测结果基本一致。采用残强法评定溃散性时,应使试样的温度场与实际砂芯的温度场基本一致(采用炉冷试样方式)。     

压力机床身铸造工艺设计

介绍了J75G-800型高速精密压力机床身铸件的铸造工艺。由于铸件外形尺寸庞大而壁薄、内腔结构复杂,采取了如下工艺措施：（1）分型面与浇注位置一致;（2）增加工艺补正量,将最薄壁厚20mm增加到25mm,原主要壁厚25mm增加到30mm;（3）采用φ50mm×8mm无缝钢管作为4个贯穿床身全长的狭长内腔砂芯的芯骨;（4）为加快导轨的凝固速度,在导轨表面等距离设置40mm厚的石墨冷铁。铸件检测结果：组织致密,珠光体体积分数大于98%,导轨硬度平均值为190HB,各项力学性能均达到了设计要求。     

改性水玻璃砂型(芯)温度场的计算机模拟和出砂性研究

根据Laplace导热方程,建立了各节点的数值方程以及求解条件,使用计算机编程对圆筒彤铸件及其砂芯、铸型进行从浇注、凝固到冷却的全过程模拟计算,为检验计算机模拟型、芯温度场的准确性,实测了圆筒彤铸件的砂芯、铸型和铸件的温度场,实测结果与计算机模拟结果基本相符。用上述计算程序模拟计算了壁厚分别为60、30、18、8mm的铸件砂芯温度场分布,模拟结果表明改性水玻璃砂有好的出砂性,浇注实验证实了计算机模拟分析结果。     

F3汽缸盖铸造缺陷的防止

针对低压铸造F3汽缸盖出现的铸件缺陷,在铸造工艺上进行了改进。解决铸件气道粘砂问题的办法,一是气道砂芯表面刷细密涂料;二是改进砂芯摆放方式,由原来的堆码式改为分层分件隔离式。对于壁厚复杂铸件常出现的缩松、缩孔问题,采用激冷方式得到解决;而对于局部厚大部位的缩松问题,采用顺序凝固,开辟补缩通道也行之有效。     

汽车前桥的V法铸造工艺

介绍了汽车前桥的铸件结构和技术要求,详细阐述了该铸件的生产条件和铸造工艺:利用V法造型机造型,砂箱尺寸2 500 mm×1 800 mm×350/300 mm;采用开放式浇注系统,浇口比为ΣF直:ΣF横:ΣF内=1:1.75:7,最小截面积为9.6 cm2,冒口尺寸为φ80 mm;在砂箱的箱档上焊接支撑与吸气2个功能的支撑钢管,涂刷涂料前,对砂型表面的涂料进行烘干,造型时要保证型腔干净,防止中间披缝;浇注温度1 540~1 560℃,浇注时间25~30 s;保压15 min,保温缓冷1 h后开箱,浇注与造型过程真空度≥55 kPa。最终生产的铸件的表面粗糙度比树脂砂工艺生产的铸件高1~2级。     

Linear contraction of ductile iron castings

The effect of casting design on the linear contraction of ductile iron castings produced in clay- and silicate-bonded sand moulds has been studied. The designs included free and restrained square bar castings.

Free contraction of very thin sections of ductile iron in sand moulds was found to approach 1.35%. As sections increased to 25 mm thick, the contraction decreased linearly to 1.08% in silicate-bonded sand moulds, but to 0.90% in clay-bonded sand moulds.

For test pieces with end flanges which stimulated various degrees of constraint as would be experienced in a shaped casting, the contraction was found to be sensitive to the third power of the relative cooling time of the flange and the cast section. In conditions of high constraint, contraction could fall as low as 0.55%.

The data from this study represent a first attempt to provide a designer and toolmaker with realistic contraction allowances for shaped castings.     

基于无模铸型制造技术的复杂铸件快速制造

无模铸型制造技术是以树脂砂为成型材料，利用快速成型技术的离散／堆积成型原理，对三维CAD实体模型进行分层切片处理，得到不同高度截面层的信息，采用截面扫描、喷射固化工艺，直接获得树脂砂铸型或铸造模具的一种方法。在复杂铸件快速制造的实际应用中，无模铸型制造技术表现出造型材料易得、制造时间短、制造成本低、铸件质量好等优点，体现了快速敏捷制造的优势，也为快速成形技术在铸造中的应用开辟了一个新领域。     

树脂砂床身热裂纹缺陷的成因及防止

分析床身铸件产生热裂纹的原因,发现热裂纹是铸件凝固过程中形成的残余热应力和型砂不良热效应相叠加的结果.根据分析的结果,采取修改铸件结构和增加变截面工艺拉筋两项工艺措施,从根本上消除了铸件热裂纹缺陷.     

特大型球墨铸铁钢锭模的铸造工艺

介绍了重量38t的大型钢锭模球铁件的生产工艺。采用底注式浇注系统,锭模内孔型芯采用焊接钢管芯骨,外层30mm为呋喃树脂砂层。铸件顶部延长200mm作为本体冒口,其顶面还设有4个安全小冒口。浇注后钢管芯骨内注入冷却水,对铸件下段进行强制冷却。利用球墨铸铁石墨化膨胀进行自补缩解决了铸件内部的缩孔、缩松缺陷,使生产的铸件达到质量要求。     

真空负压法生产叉车驱动桥的工艺实践

驱动桥是叉车的重要安全零部件，材质QT450—10，对尺寸精度、表面质量、铸件的内部组织和力学性能要求很高。原工艺为普通粘土砂造型，树脂砂吊芯，每箱1件，生产率低；采用吊芯易产生偏芯造成铸件壁厚不均；普通砂造型型腔紧实度不足，易产生显微疏松，存在安全隐患，且表面质量较差。为避免这些不足，采用真空负压法试生产驱动桥获得成功。     

Mechanical properties and microstructures of AlSi7 alloy cast in sand and in polystyrene-containing sand moulds

Experimental work has been undertaken to study the effects of polystyrene pattern material on the mechanical properties and microstructures of cast aluminium alloys. This paper reports results obtained using Al—Si 7% (LM25) alloy. Rectangular tensile test-pieces of various thickness were cast at different pouring temperatures into standard resin-bonded sand moulds. The experiments were then repeated with polystyrene patterns placed into the sand mould cavities. A direct comparison of the effects of polystyrene pattern material on the properties of the cast test-pieces with those obtained under identical conditions by a standard sand casting method has thus been obtained. Ultimate tensile strength, elongation, Vickers hardness, porosity volume, and dendrite arm spacing (DAS) values relating to both methods were evaluated for a range of casting section thickness (4–16 mm) and pouring temperature (690–780 °C). The microstructural differences observed between the test pieces obtained, with and without polystyrene patterns, were verified by the changes in the solidification cooling curves recorded simultaneously for both methods.

The results obtained show that an expanded polystyrene pattern contained within a sand mould, under the experimental conditions used, does not have an adverse effect on the as-cast mechanical properties of LM25 alloy. On the contrary, the presence of polystyrene in the sand moulds resulted in higher rather than lower tensile properties. These findings have been supported by microstructural observations which reveal finer microstructures and lower volumes of porosity in the test pieces produced with the use of polystyrene, rather than in the absence of it. These observations are further supported by the evidence obtained from the cooling curves which reveal that the presence of polystyrene in the sand mould results in a faster casting cooling rate compared with that when no polystyrene is present.     

细纱机箱体铸铁件顶雨淋浇注系统充填补缩一体化设计

FA528型细纱机箱体铸件,材质HT200,轮廓尺寸840 mm×736 mm,主要壁厚12 mm,最大壁厚30 mm,重236 kg,呋喃树脂自硬砂型.用大孔出流理论设计浇口杯一内浇道二单元顶雨淋浇注系统,用均衡凝固收缩模数法核算浇注系统的补缩能力.设计结果：长盆形浇口杯上宽60 mm,下底宽30 mm,长430 mm;下设7只φ14 mm雨淋内浇道,在浇注系统的对侧设置溢流排气冒口.经3 800件批量生产验证,铸件没有冷隔、浇不足、缩孔、气孔类铸造缺陷.表明采用均衡凝固收缩模数法计算铸件的补缩是实用、可靠的.     

The production of high-density hollow cast-iron bars by vertically continuous casting

Hollow cast-iron bars with an outer diameter of 60-300 mm, a wall thickness of 7-40 mm and a length of 10 m or longer were produced massively by vertically continuous casting. The whole casting processes were analogous to the casting processes of solid bars by horizontal continuous casting. The metallographic microstructure, the distribution of chemical composition along their radius direction and the mechanical properties of the hollow bars were investigated. The results show that the hollow cast-iron bars are compact and few shrinkage cavities and shrinkage porosities exist in them. Their graphite grains or their eutectic colonies are very fine and their mechanical properties are superior to that of bars produced by sand casting. Their chemical composition is distributed uniformly along their radius direction and no segregation was observed.     

封口墙板裂纹的防止

封口墙板结构复杂、壁薄,铸造时易出现裂纹缺陷。通过降低材料牌号,使用呋喃树脂自硬砂取代粘土制芯,延长铸件在型内冷却时间,使裂纹缺陷问题得到解决。