Permeable Steel and Its Application in Plastic-injection Mould

The gas in plastics mould has great influence on performance, appearance and lifespan of the injection molded parts. Venting channel and its appendix system should be used for gas exhausting in general. However, the dependence on the venting system complicates the mould design. Furthermore in certain condition, it is difficult to integrate the venting system into the mould. Currently a kind of mold material which has gas permeability has been developed in abroad, but the applications of this mold material were restricted by its higher cost and smaller size. In this research, a porous material which was made by powder metallurgy was applied to plastic mould to replace the venting system. Permeability of the steel with different secondary processing was tested and compared with a special apparatus. The metallographic samples of the steel with different secondary processing were prepared and investigated. Finally an actual injection set was established to investigate the applications of permeable steel. The metallographies indicate that the micro-holes inside permeable steel were interconnected. Moulds made of permeable steel exhibit good permeability in the plastic-injection experiments and gas generated in the mould cavity was smoothly exhausted. The melted plastic did not penetrate into the mould or block in the micro-holes. After several times of plastic-injection experiments, the mould still retained good permeability. The strength of this permeable steel is between 200–250 MPa and suitable for industrial applications. The venting systems simplified by permeable steel in plastic-injection have simple structures, which can be applied into any place that requires gas exhausting.

Computer Aided Composition Design of Prehardened-Mould Steel for Plastic

The improvement of machining behavior of prehardened-mould steel for plastic is realized by using computer-aided composition design in this work. The results showed that the matrix composition of large sectional prehardened mould steel for plastic markedly influences the precipitation of non-metallic inclusion and the control of composition aided by Thermo-Calc software package minimizes the amount of detrimental oxide inclusion. In addition the modification of calcium is optimized in the light of composition design.

Investigation into microstructure of spray formed V4 cold working mould steel and its roiling and annealing

The material selected for this work was the spray formed Vanadis4 high alloy cold working mould steel （abbreviated to V4 steel）. Its microstructure, hot rolling process, and annealing treatment have been investigated. Observed from the optical and electron microscopes, the as-sprayed V4 steel had the finer microstructure of uniform and equiaxial grains ,while after hot rolling for densification and spheroidized annealing, the V4 steel obtained an excellent spheroidized structure that is favorable to subsequent quenching and tempering treatment. The spheroidized structure and level of annealed hardness of the V4 steel are almost the same as expensive imported powder metallurgy the V4 steel. It is difficult to produce V4 steel with the conventional ingot metallurgical technique, so the multi-step and high-cost powder metallurgy method is generally used at present. Compared to the powder metallurgy technique, using the spray forming technique to produce the V4 steel has obvious advantages and potential market competitiveness in reducing production costs, simplifying working process, and shortening the production cycle.

Solidification microstructure of M2 high speed steel by different casting technologies

The present work investigated the solidification microstructure of AISI M2 high speed steel manufactured by different casting technologies, namely iron mould casting and continuous casting. The results revealed that the as-cast structure of the steel was composed of the iron matrix and the M2C eutectic carbide networks, which were greatly refined in the ingot made by continuous casting process, compared with that by the iron mould casting process. M2C eutectic carbides presented variation in their morphologies and growth characteristics in the ingots by both casting methods. In the ingot by iron mould casting, they have a plate-like morphology and grow anisotropically. However, in the ingot made by continuous casting, the carbides evolved into the fiber-like shape that exhibited little characteristics of anisotropic growth. It was noticed that the fiber-like M2C was much easier to decompose and spheroidize after heated, as a result, the carbides refined remarkably, compared with the case of plate-like carbides in the iron mould casting ingot.

Computer-Aided Design of Some Advanced Steels and Cemented Carbides

Thermodynamic and kinetic study on TRIP （transformation induced plasticity） steels, cemented carbides and mold steel for plastics were carried out in order to design modern advanced materials. With the sublattice model, equilibrium compositions of ferrite and austenite phases in TRIP steels, as well as volume fraction of austenite at inter-critical temperatures for different time were calculated. Concentration profiles of carbon, manganese, aluminum and silicon in the steels were also estimated in the lattice fixed frame of reference. The effect of Si and Mn on TRIP was discussed according to thermodynamic and kinetic analyses. In order to understand and produce the graded nanophase structure of cemented carbides, miscellaneous phases in the M-Co-C （M= Ti, Ta, Nh） systems and Co-V-C system were modeled. Solution parameters and thermodynamic： properties were listed in detail. The improvement of machining behavior of prehardened mould steel for plastics was obtained by computer-aided composition design. The results showed that the matrix composition of large-section prehardened mould steel for plastic markedly influences the precipitation of non-metallic inclusion and the composition control by the aid of Thermo-Calc software package minimizes the amount of detrimental oxide inclusion. In addition, the modification of calcium was optimized in composition design.

Effect of weld line positions on the tensile deformation of two-component metal injection moulding

Knowledge of the mechanical properties of two-component parts is critical for engineering functionally graded components. In this study, mono-and two-component tensile test specimens were metal injection moulded. Three different weld line positions were generated in the two-component specimens. Linear shrinkage of the two-component specimens was greater than that of the mono-component specimens because the incompatibility of sintering shrinkage of both materials causes biaxial stresses and enhances sintering. The mechanical properties of 316L stainless steel were affected by the addition of a coloured pigment used to identify the weld line position after injection moulding. For the two-component specimens, the yield stress and ultimate tensile stress were similar to those of 316L stainless steel. Because 316L and 630(also known as 17-4PH) stainless steels were well-sintered at the interface, the mechanical properties of the weaker material(316L stainless steel) were dominant. However, the elongations of the two-component specimens were lower than those of the mono-component specimens. An interfacial zone with a microstructure that differed from those of the mono-material specimens was observed; its different microstructure was attributed to the gradual diffusion of nickel and copper.

Biocompatibility of MIM 316L stainless steel

To evaluate the bioeompatibility of MIM 316L stainless steel,the percentage of S-period cells were detected by flow cytometry after L929 incubated with extraction of MIM 316L stainless steel,using titanium implant materials of clinical application as the contrast.Both materials were implanted in animal and the histopathological evaluations were carried out.The statistical analyses show that there are no significant differences between two groups(P>0.05),which demonstrates that MIM 316L stainless steel has a good biocompatibility.

新能源冷藏车制冷机锁扣注射模设计

针对10%碳纤维改性PEEK材料的新能源冷藏车制冷机锁扣,设计了1模2腔三板注射模,模具浇注系统使用点浇口,采用4个定模滑块先抽芯机构实现成型塑件部分特征的脱模,其中1个为斜向抽芯机构,3个为直线型抽芯机构。抽芯机构依靠开模动力驱动锁紧块拉动滑块抽芯和锁紧,动作可靠且效率高,保证了塑件的成型效率及成型品质。

内置钢管式塑料托盘注塑模具设计及承重仿真分析

针对内置钢管式塑料托盘,详细介绍了模具主要结构设计,包括浇注系统、成型零部件、侧向抽芯、顶出系统、冷却系统以及排气系统的设计,并绘制了模具结构总装图,阐述了模具工作原理。由于模具结构复杂为四面滑块抽芯结构,故对于天侧倒扣区域采用“大滑块+液压油缸”的单侧抽芯机构,操作侧、非操作侧倒扣区域采用“大滑块+液压油缸”的两侧抽芯机构,地侧倒扣区域采用“斜导柱+大滑块”的抽芯结构,内侧倒扣区域则是采用一种新型交叉辅助杆斜顶抽芯结构,从而解决托盘脱模困难问题。此外,利用有限元分析软件Abaqus模拟托盘在静载荷、动载荷(叉车搬运)状态下的受力情况。由分析结果可知,托盘在两种状态下最大应力均未超过材料的屈服强度,说明托盘强度能够满足使用要求。最终进行实际生产,结果表明,设计的模具结构合理,安全可靠,成型后的托盘质量好,能够为同类托盘的设计提供参考依据。

减少冷轧低碳钢轧材表面夹杂缺陷实践

针对冷轧低碳钢轧材表面夹杂缺陷问题,分析主要原因是结晶器保护渣卷入钢水导致,采取优化保护渣理化性能,优化铸机拉速、水口浸入深度和氩气流量等措施后,降低了卷渣风险,冷轧低碳钢表面夹杂缺陷指数由4降至1,提高了产品表面质量。

重晶石混凝土异形构件钢模具有限元模拟

装配式构件模具的力学性能对预制构件质量控制至关重要。为分析重晶石混凝土异形墙体构件钢模具在新浇筑混凝土作用力下的力学性能及变形影响因素,利用有限元软件ABAQUS建立有限元仿真模型,对模板施加混凝土荷载,进行模拟分析。结果表明,此构件模具变形较大处在侧面模板中上部,模具最大变形量随钢板弹性模量、厚度的降低以及加劲肋间距、混凝土重度的增加而逐渐增大。

组合式钢模台车在长距离隧道施工中的应用

水利水电项目隧道工程采用钢模台车进行衬砌施工,常常会遇到曲线段台车就位难度大、转角处易侵占衬砌结构面等问题,影响隧道衬砌质量和使用性能。结合长距离隧道曲线特征、断面尺寸、工作面划分等特点,将钢模台车设计成标准单元模块型式,通过标准单元模块自由组合成长度为16 m、24 m和32 m的组合式钢模台车,用于隧道衬砌施工。应用实践表明,组合式钢模台车施工效率高、工作面之间协调灵活,大幅缩短施工进度和减少台车的配置,同时在曲线段将台车分离成标准单元长度使用,更容易控制曲线隧道衬砌结构面,保障工程施工进度。

易切削非调质汽车用钢表面裂纹形成机理及工艺优化

易切削非调质汽车用钢采用410 mm×530 mm大断面连铸坯轧制成规格Φ130~220 mm的钢材,表面探伤合格率较低,钢材表面出现裂纹缺陷,通过对钢轧全流程系统分析发现为连铸坯表面角部横裂纹和星状裂纹所导致,其与结晶器铜管倒锥度及R角不合理、钢中硫化物形态及偏析聚集、保护渣理化指标适配性差、二次冷却系统工艺有待优化等方面原因有关。通过改进结晶器铜管倒锥度及R角、微钙化处理工艺改善钢中硫化物形态、调整结晶器保护渣的理化性能指标、优化二次冷却系统,酸洗试样表面质量合格率提高了近30%,铸坯表面磁粉探伤合格率提高至99.2%,连铸坯所对应轧材的表面探伤最高炉次达98.6%、最低炉次达92.4%,铸坯纵剖酸洗试样V型偏析改善明显,且碳、硫的中心偏析指数分别为1.04、0.97,符合±0.05的高标准均质化要求。

国内外模具钢发展现状

简要分析了过去、现在乃至今后国内外模具钢(冷作模具钢、热作模具钢和塑料模具钢)发展的基本指导思想及在此指导思想下研发的各种新型模具钢。最后对我国模具钢发展和生产中存在的问题进行了分析并提出了建议。

汽车覆盖件用淬硬钢模具铣削加工的研究进展

作为汽车产销量第一大国,我国的汽车模具加工能力远远不能适应汽车更新换型的需要,中高档轿车关键覆盖件模具铣削加工质量还达不到设计要求。通过汽车大型覆盖件淬硬钢模具的铣削加工特征和难点的分析可知,铣削过程建模与仿真分析、加工工艺系统动力学特性和铣削稳定性分析、汽车覆盖件淬硬钢模具铣削加工用刀具研制、自由曲面数控编程技术及工艺规划是汽车模具高精度铣削加工的研究重点,总结归纳这几个方面的研究现状,同时探讨汽车覆盖件淬硬钢模具铣削加工仍有待于进一步解决的问题,为其后续研究方向提出一些建议。

调质工艺对3Cr2Mo钢组织和性能的影响

通过洛氏硬度和冲击试验以及OM、SEM和TEM组织观察,研究了不同热处理工艺参数对塑料模具用3Cr2Mo钢显微组织和力学性能的影响,分析不同热处理工艺条件下3Cr2Mo钢塑性、硬度以及冲击韧性的变化规律。结果表明:3Cr2Mo钢经850～920℃×1 h油淬,获得细小板条状马氏体组织,合金元素充分溶解;经570～630℃空冷回火,碳化物细小弥散分布得到均匀稳定的回火索氏体组织,其硬度达到较佳的使用范围(28～36 HRC),且具有较好的强韧性配合,能够满足塑料模具钢使用要求。

合金钢连铸结晶器保护渣的基本功能

分析了合金钢连铸结晶器保护渣对钢水的保温和避免钢液氧化功能、吸收夹杂物的能力、以及润滑铸坯和控制传热的功能。改善保护渣的保温性能 ,有利于减轻振痕缺陷和铸坯皮下夹渣 ,提高保护渣吸收夹杂能力 ,防止高合金钢连铸时的漏钢和减少铸坯夹渣缺陷 ;而协调保护渣传热与润滑的功能对避免粘结漏钢和减少铸坯表面纵裂纹和微裂纹有着不可低估的作用。

大截面预硬型塑料模具钢的组织与性能

对大截面预硬型塑料模具钢ASSAB718和国产GC718钢进行了对比性研究。结果表明 ,GC718钢的等向性较好 ,厚向的冲击功可达到纵向的 70 %～ 80 % ,但以氧化物为主的夹杂物含量高。ASSAB718钢表面的等向性高 ,但心部等向性低 ,心部厚向冲击功仅为纵向的 32 % ,以硫化物为主的夹杂物含量为 0 0 9%。

H13模具钢离子渗氮层的组织与性能

利用 10kW的等离子体气相沉积炉对H13钢进行了离子渗氮处理 ,研究了不同温度及时间对渗氮层组织及性能的影响。结果表明 ,采用合适的处理温度和时间 ,可以得到最佳的渗氮层化合物相组成及表面硬度 ,在保证一定的渗氮层深度条件下 ,H13钢的耐磨性能明显提高。

钛稳定化321不锈钢连铸结晶器“结鱼”的研究

用扫描电镜分析了钛稳定化 32 1铬镍奥氏体不锈钢板坯连铸过程中结晶器中形成的“结鱼”的物相组成 ,探讨了“结鱼”形成机理和预防措施。结果表明 ,连铸过程钢水中已形成的TiN在结晶器内聚集 ,并与保护渣中SiO2 和Fe2 O3等氧化物反应放出氮气 ,由于是吸热反应 ,促使局部钢水冷却凝固形成“结鱼” 悬浮钢块。保持钢中 [Ti% ]·[N % ]× 10 3<3 5 ,Alsol≤ 0 .0 1%时 ,可避免形成“结鱼”。