基于Moldflow的大型检查井注塑流动分析

在分析大型检查井注塑工艺性能的基础上,以四通检查井注塑模浇注系统为例,采用Moldflow软件分析单浇口、轮辐式6浇口、轮辐式40浇口等浇注方式,并研究浇注系统的浇口位置、数量和尺寸对制品质量和锁模力、注塑压力、保压压力等工艺要素的影响。结果表明:在制品端口设置热流道轮辐式多浇口,可显著降低剪切速率、锁模力、注塑压力和保压压力,并减少或避免制品表面的熔接痕。     

24cm铝锅手柄注塑模具设计

通过分析铝锅手柄的结构特征,设计出一模四腔斜导柱抽芯注塑模具。模具采用热流道浇注系统,浇口点直达塑件最佳浇口位置,减少压力和温度损失,提高了塑件质量。模具设计结构合理,开合模动作可靠,制品脱模顺利,塑件精度高,产品完全达到客户要求。     

薄壁LDS天线件注射模具设计

以某手机天线后壳为研究对象,针对产品结构薄弱处容易发生断裂的风险,用Moldflow分析软件进行了模流分析,避免了熔接线出现在结构薄弱的位置,同时对模具冷却水路进行了优化。浇注系统采用2点热流道转冷流道及4个侧浇口的最佳浇注方案。实践证明,该设计提高了产品的结合性及良品率,产品符合设计要求,适于大批量生产。     

大浇口注射模改造热流道技术简

热流道技术是国家“十五”制造业大力发展而迫切需求的一项实用新技术,采用该技术可减少制品废料、缩短成型周期、提高制品精度。模具行业热流道的应用越来越主流,而一些旧式大浇口模具为了得到更好效益比,将会在条件允许的情况下进行热流道的改造。本文解析了现有大浇口注射模改造为热流道注射模的可行性以及工艺步骤,并对热流道的实用技术进行分析研究,让模具价值发挥到最大。     

大浇口注射模改造热流道技术

热流道技术是国家"十五"制造业大力发展而迫切需求的一项实用新技术,采用该技术可减少制品废料、缩短成型周期、提高制品精度。模具行业热流道的应用越来越主流,而一些旧式大浇口模具为了得到更好效益比,将会在条件允许的情况下进行热流道的改造。本文解析了现有大浇口注射模改造为热流道注射模的可行性以及工艺步骤,并对热流道的实用技术进行分析研究,让模具价值发挥到最大。     

汽车仪表台右侧装饰条骨架注射模设计

介绍了汽车仪表台右侧装饰条骨架热流道注射模的结构特点,参考模流分析设置浇口位置,并设计了普通流道及热流道相结合的浇注系统,根据制品形状特点设计了冷却水路。借助斜推机构、滑块、液压缸抽芯机构等实现了成型制品不同区域倒扣的脱模,模具采用一模多腔设计,抽芯结构多,配模难度大,经实际生产验证,模具成型的制品合格,可为类似制品的模具开发提供参考。     

热流道注射模

上海胜德塑料厂研制的热流道模具,采用外热式点浇口热流道,在八种制品上取得成功。其模具结构特点是:(1)采用两腔的点浇口,浇口尺寸随制件大小、材料而定,一般尼龙、PP、PE 等点浇口尺寸为φ0.8～1.2,PP 改性与 PC 的浇口应增大到φ1.5～1.8左右。(2)适用于各类注射机(包括立式、卧式)。(3)模具结构除热流道部分外,其余均采用常规注射模设计。(4)操作时应控制电流表的数据,以免线圈烧坏。(5)选择合理的     

大型塑料注射模具讲座——第三讲 浇注系统的设计

<正> 概述 浇注系统通常分为普通浇注系统和无流道浇注系统。设计浇注系统时首先要了解塑料及其流动特性,根据流动比范围确定主流道、分流道、浇口的长度尺寸,再根据计算确定流道断面尺寸。设计分流道时(多针点式浇口)应尽量均匀布置或使各浇口处的熔体压力降相等,这样才能保证产品质量。大型模具设计中常用的有直浇口、潜伏式浇口、多针点浇口、圓环形浇口、轮辐式浇口、热流道浇注系统等。 设计大型塑料模具时应遵循下列原则: (1)能顺利地引导熔融塑料流到型腔各部位,尤其是各个深处。在填充过程中不产生涡流、紊流使型腔内的气体能顺利地排出。     

透明水箱热流道注射模设计

根据透明水箱表面质量要求高的特点,通过对塑件结构和工艺性进行分析,对不同浇口位置、普通流道与热流道方案的对比分析,确定了单点浇口的热流道模具设计方案,对模具设计要点及工作过程作了介绍,实践证明,生产的塑件合格,对同类产品的模具设计具有一定的借鉴作用。     

盖壳体形体要素与缺陷预期分析及注射模设计

通过对盖壳体形体要素分析,其具有凹槽、凸台和外观要素。盖壳体在注射模中竖立摆放,分型面设置在底面。若浇口也设置在底面,根据缺陷预期分析,塑料熔体为逆流填充而产生填充不足、气泡、过热痕、流痕和银丝等缺陷。因此,塑料熔体必须采用顺流填充,将模具潜伏式点浇口设置在盖壳体上部。如此,上述缺陷复不存在,并能满足外观要求。注入潜伏式流道的塑料熔体,借助顶杆上的点浇口进入模具型腔。依靠拉料杆可将主流道中冷凝料拉脱模,应用顶杆可顶脱分流道和潜伏式流道中冷凝料。在顶杆顶脱盖壳体的同时,使得附在顶杆中的点浇口冷凝料能自行掉落。该浇注系统缩短了浇注系统的长度,避免了使用热流道,这种浇注系统和脱模结构具有一定的使用价值。     

造粒炭黑质量分数对Cu-Fe摩擦材料性能的影响

采用干压擦筛造粒法制备了炭黑造粒颗粒,研究了炭黑造粒颗粒质量分数对Cu-Fe摩擦材料显微组织、力学性能、摩擦性能的影响。结果表明：炭黑造粒颗粒易被压制成条状形态,当炭黑造粒颗粒质量分数较低时,其与金属基体能形成完整的界面,而含量较高时界面易出现孔洞和裂纹;随着炭黑造粒颗粒质量分数的增加,摩擦材料的力学性能先增加后降低、摩擦系数和磨损量均先降低后增加。当炭黑造粒颗粒质量百分数为5%时,摩擦材料的力学性能最大,摩擦系数最低,磨损量最小,材料的综合性能最佳。     

Influence of temperature and the role of chromium on the kinetics of sulfidation of 310 stainless steel

The sulfidation of 310 stainless steel was studied over the temperature range from 910 to 1285° K. By adjusting the ratio of hydrogen to hydrogen sulfide, variations in sulfur potential were obtained. The effect of temperature on sulfidation was determined at three different sulfur potentials: 39 N·m^–2, 1.4×10^–2 N·m^–2, and 1.5×10^–4 N·m^–2. All sulfide scales contained one or two surface layers in addition to a subscale. The second outer layer (OL-II), furthest from the alloy, contained primarily Fe-Ni-S. The first outer layer0 (OL-I), nearest the subscale, contained Fe-Cr-S. The subscale consisted of sulfide inclusions in the metal matrix. Two different phases were observed in OL-II depending on the temperature and sulfur potential. Below 1065°K OL-II is composed of a mixture of monosulfides of iron and nickel (Fe Ni)_1–xS and pentlandite (Fe_4.5Ni_4.5S₈) with the pentlandite phase exsolved as lamellae upon cooling. At temperatures higher than 1065°K only the pentlandite phase was formed, which melted above 1145°K at sulfur potentials greater than 10^–2 N·m^–2, yielding metal-rich iron-nickel-sulfur. Above 1145°K, and at sulfur potentials less than 10^–2 N·m^–2, OL-II ceased to exist (this temperature is termed transition temperature). Below the transition temperature, where OL-II exists, OL-I could be represented by the general composition (Fe, Cr)_1–xS. This phase on cooling transformed into an array of structures differing in FeCr ratio. These substructures, however, were not observed in quenched samples. Above the transition temperature OL-I changed to a chromium-rich sulfide composition and was associated with a sudden decrease in reaction rate. Subscale formation was found to be due to the dissociation of OL-I at the scale-metal interface, and the extent of subscale growth was found to depend on the temperature and the sulfur potential, as well as the composition of OL-I. At a given temperature and sulfur potential the weight-gain data obeyed the parabolic rate law after an initial transient period. The parabolic rate constants obtained at the sulfur potential of 39 N·m^–2 did not show a break when the logarithm of the rate constant was plotted as a function of the inverse of absolute temperature. Sulfidation carried out at a sulfur potential below 2 × 10^–2 N·m^–2, however, did show a break at 1145°K. This break was found to be associated with the changes which had occurred in the FeCr ratio of OL-I. Below the transition temperature the activation energy was found to be approximately 125 kJ · mole^–1. Above the transition temperature the rate of sulfidation decreased with temperature but depended on the FeCr ratio in the ironchromium-sulfide layers of the OL-I. A reaction mechanism consistent with the experimental results has been proposed in which the diffusion of cations through OL-I is the rate-controlling step. Below the transition temperature the diffusion of Fe and Ni through OL-I contributes to the scale formation, whereas above the transition temperature the diffusion of Cr through OL-I controls the scale formation. Existing literature on the Fe-Ni-S system is compared with the present results.     

Studies of the mechanism of reaction of nickel with SO2

The reaction of nickel with SO₂ has been studied. The composition and morphology of the scale formed in sulfur dioxide (1.013×10⁵ Pa) at 600°C and the transport phenomena occurring in the growing scale have been investigated. The experimental methods consisted of metallography, scanning electron microscopy, and electron microprobe analysis. The transport phenomena have been studied by the marker method and with the use of a³⁵S radioisotope. The scale was composed of a NiO and Ni₃S₂ mixture and grew by the outward diffusion of nickel and inward transport of SO₂ molecules through the discontinuities of the scale. It has been shown that outward transport of sulfur originating from grains of sulfide occurs.     

The Inhibitive Effect of Traces of SO2 on the Oxidation of Iron

The oxidation of Fe was investigated at 500–700°C in the presence of O₂ with 0–1000 ppm SO₂. The exposures were carried out in a thermobalance and lasted for 24 h. The oxidized samples were investigated by grazing-angle XRD, SEM/EDX, GDOES and XPS. The rate of oxidation of pure iron is slowed down by traces of O₂ in O₂ below 600°C while SO₂ has no effect on oxidation rate at higher temperatures. Exposure to SO₂<600°C resulted in the formation of small amounts of sulfate at the gas/oxide interface. In addition, sulfur, probably sulfide, accumulated at the metal/oxide interface. The influence of SO₂ on oxidation rate is attributed to surface sulfate. The sulfur distribution in the scale is rationalized in terms of the thermodynamic stability of compounds in the Fe–O–S system. Exposure to SO₂ caused the formation of hematite whiskers.     

Some aspects of the mechanism of high-temperature oxidation of nickel in SO2

A number of investigations on the mechanism of reaction of nickel with SO₂ has been summarized. The calculation results of the equilibrium gas composition in homogeneous SO₂+O₂ mixtures are described over wide ranges of temperatures (500–1100°C) and initial gas compositions. The Ni–O–S phase diagram at 540°C has been compared with data on the stability of interaction products under conditions close to equilibrium. The catalytic activity of NiO has been verified to accelerate the attainment of thermodynamic equilibrium in the SO₂–O₂–SO₃ system. The most effective catalytic activity of NiO occurred at 650–800°C. A monolayer (6 Å) of NiSO₄ was detected on the scale surface by ESCA. This surface phase is assumed to be formed either as an activated complex on the NiO catalyst or as the locally stable NiSO₄ phase. Both assumptions lead to a possible recognition of the sulfate intermediate mechanism.     

Calculation of Reactive-evaporation Rates of Chromia

A methodology is developed to calculate Cr-evaporation rates from Cr₂O₃ with a flat planar geometry. Variables include temperature, total pressure, gas velocity, and gas composition. The methodology was applied to solid-oxide, fuel-cell conditions for metallic interconnects and to advanced-steam turbines conditions. The high velocities and pressures of the advanced steam turbine led to evaporation predictions as high as 5.18 × 10⁻⁸ kg/m²/s of CrO₂(OH)₂(g) at 760 °C and 34.5 MPa. This is equivalent to 0.080 mm per year of solid Cr loss. Chromium evaporation is expected to be an important oxidation mechanism with the types of nickel-base alloys proposed for use above 650 °C in advanced-steam boilers and turbines. It is shown that laboratory experiments, with much lower steam velocities and usually much lower total pressure than found in advanced steam turbines, would best reproduce chromium-evaporation behavior with atmospheres that approach either O₂ + H₂O or air + H₂O with 57% H₂O.     

Assessment of the effect of fillets and special features of technology on the mechanical properties of brazed joints

The factors determining the contribution of fillets to the mechanical properties of brazed joints are systematically analysed. A model is proposed for evaluating the contribution of fillets in the tensile test. The mechanical properties of the joints are influenced by: the geometrical factor α, which determines the ratio of the fracture areas S₁ (fillet) and S₂ (joint) α = S₁/S₂; structural and technological factors which determine the chemical composition of the joint, fillets, and also their dimensions and structure. The contribution of the fillets to the mechanical properties of the joints may be equal to 10–70%. In brazing heat exchangers at α = 0.5–0.8, the contribution of the fillets to the mechanical properties does not exceed 10%, and the special features of the technology have a controlling effect.     

Characterization of the effects of silicon on the formation of goethite

Goethite samples were synthesised with different sodium silicate concentrations (0, 10⁻⁵, 10⁻⁴, 10⁻³ and 10⁻² M) in the initial aqueous solution. X-ray diffraction (XRD), Mössbauer spectrometry, inductively coupled plasma mass spectrometry (ICP-MS) and transmission electron microscopy (TEM) were used to investigate the influence of Si content on the formation and physical characteristics of goethite. Mössbauer spectroscopy and TEM results demonstrate that the particle size changes as the sodium silicate content increases. XRD results (lattice parameters, line width and mean coherence length values) do not show any indication that Si species would substitute for Fe in the goethite structure.     

纳米氧化铜对磷酸盐胶黏剂耐水性能的影响

以H3PO4和Al(OH)3为基体,纳米氧化铜为填料来制备磷酸盐无机胶黏剂。胶黏剂粘结的莫来石片,在人工海水中浸泡168 h后,测试其剪切强度,并以此强度为标准,来探究纳米氧化铜的加入对磷酸盐胶黏剂耐水性能的影响。研究结果表明,纳米氧化铜可以有效改善粘结剂的耐水性能,并且当加入量为基体的20%(质量分数,下同)时,经150℃处理的莫来石粘结片浸泡在人工海水中168 h的抗剪切强度最高,为7.13 MPa;莫来石粘结片经1300℃处理后,浸泡在人工海水的抗剪切强度最低,为2.31 MPa;发现经煅烧处理的纳米氧化铜相比未煅烧处理的氧化铜可以更好地提高粘结剂粘结强度。     

Thermodynamics of Solvent Extraction of Indium with EHEHPA

Molalities of In³⁺ were measured at ionic strength from 0.1 to 2.0 mol·kg⁻¹ in aqueous phase containing Na₂SO₄ as supporting electrolyte and at constant molality extractant at temperatures from 278.15 to 303.15 K in organic phase. The standard extraction constants K ⁰ at various temperatures were obtained by methods of extrapolation and polynomial approximation. Thermodynamic quantities for the extraction process were calculated.