Tempering Process to Improve Hardness Uniformity of Plastic Mould Steel

A new design of copper-bearing non-quenched plastic mold steel is presented and explained. Two kinds of microstrueture can be obtained from this new type copper-bearing steel via cooling with different cooling rates, bain- ite and a mixed microstructure consisting of ferrite and bainite. It is found that, after proper tempering process, the hardness will be increased. Moreover, the hardness difference between different microstructures will be reduced. For further investigation, the samples tempered at different temperatures were examined by XRD and 3PAP （three di- mensional atom probe） analysis. Results show that the improvement is contributed mainly by the precipitation of Cu phase and transformation of residual austenite.

Influence of Austenitizing Temperature on the Microstructure and Corrosion Resistance of 55Cr18Mo1VN High-Nitrogen Plastic Mould Steel

The influence of austenitizing temperature on the microstructure and corrosion resistance of 55Cr18MolVN high-nitrogen plastic mould steel was investigated. The microstructure, elemental distribution and Cr-depleted zone of different heat-treated samples were investigated by X-ray diffraction, electron probe microanalyzer analysis, and trans- mission electron microscopy. The corrosion resistance was evaluated using electrochemical measurements, and the analysis of passive film was carded out by X-ray photoelectron spectroscopy. The results indicated that the volume fraction of precipitates decreased, and the homogeneity of elements was improved with increasing austenitizing temperature. The degree of Cr-depleted zone around coarse M23C6 was severer than that around M2N, and pitting corrosion initiated preferentially around M23C6. The corrosion resistance of the samples increased with the austenitizing temperature. With the increase in austenitizing temperature, the passive film was thickened and Cr（III）cr2O3 in the inner layer of passive film was enriched, which enhanced the corrosion resistance of the steel. The higher content of nitrogen in solid solution at higher austenitizing temperature contributed to the increased intensity of CrN and NH3, leading to the increase in pH value in the pit, and promoting the repassivation of 55Cr18Mo1N steel.

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.

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。

Development of Non-Quenched Prehardened Steel for Large Section Plastic Mould

In order to meet the demand of prehardened steel for large section plastic mould and save energy, a nonquenched prehardened （NQP） steel is developed. The temperature field of a large block is researched by finite element method simulation and 9 test steels are designed in the laboratory. Their microstructures and hardness are investigated when they are air cooled and control cooled at cooling rate similar to the simulation. The result shows that the hardness uniformity through section is closely correlated to bainitic hardenability for the NQP steel, and the hardness of one test steel （0.27C-1.95Mn-1.04Cr-0.45Mo-0.1V） fluctuates between HRC 40 and 43 under both cooling conditions. The test steel has better machinability compared with C45 steel, and the NQP steel is produced successfully in the factory based on the laboratory results. Its microstructure is bainite, and it is distributed uniformly through the size of 460 mm×800 mm×3 200 mm.

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。

大截面非调质预硬型塑料模具钢组织对硬度均匀性的影响

采用光学显微镜,扫描电镜和透射电镜观察了截面尺寸为460mm×800mm的非调质预硬型塑料模具钢(NQP钢)模块心部和表层的组织,结果表明,心部组织较表层粗大,表层存在变形带特征,但精细结构均为位错密度较高的贝氏体铁素体板条和板条间不连续的碳化物或残余奥氏体组成,心部贝氏体铁素体板条稍宽于表层。结合NQP钢连续冷却时的相变特点,分析其截面硬度波动在±1.5HRC内的原因在于其有较好的贝氏体淬透性,模块整个截面上都得到了均匀的贝氏体组织,贝氏体板条宽度和位错密度的差异使得其表层硬度稍高于心部。

塑料模具钢表面激光熔覆陶瓷复合涂层的性能研究

为了提高覆层的硬度和耐磨性,在塑料模具钢P20表面预置非晶的纳米Al2O3,TiC,WC等陶瓷硬质颗粒的涂层,采用CO2激光器进行熔覆处理。对激光熔覆陶瓷复合层的显微组织结构进行了分析,并测试了其硬度和耐磨性。结果表明:通过高能量密度的激光处理,基体和熔覆层元素相互扩散与反应,其中的WC,Al2O3,FeSi成为熔覆层中的硬质相,显著提高了材料的硬度和耐磨性。磨损后熔覆层表面主要为细小的划痕,其磨损方式主要为磨粒磨损。

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%。

淬回火工艺对马氏体不锈钢3Cr17Mo组织和力学性能的影响

试验研究了960～1140℃淬火、200～650℃回火工艺对成分（％）为0．39C，16．73Cr，1．07Mo，0．25V，0．09Cu的塑料模具用马氏体不锈钢3Cr17Mo组织和力学性能的影响。结果表明，3Cr17Mo钢的淬火组织为板条马氏体＋铁素体＋（Fe，Cr）23C6碳化物；经1000～1060℃淬火、260～300℃或550～600℃回火后。3Cr17Mo钢具有良好的综合力学性能。

预硬型塑料模具钢的研究进展

综述了预硬型塑料模具钢的分类、性能要求和国内外预硬型塑料模具钢的牌号和化学成分,重点介绍了近年来国内预硬型塑料模具钢在成分设计和热处理工艺改进方面取得的研究成果,其中一些钢的性能和预硬化工艺达到国际先进水平,指出了预硬型塑料模具钢今后的发展方向。

P20钢大型塑料模具几种淬火工艺的三维温度与组织模拟

通过建立合适的三维有限元模型 ,研究了P2 0钢大型模具按 3种工艺进行淬火时的温度组织变化。模拟结果表明 ,工艺a造成了模块内过大的温度梯度 ;工艺b通过多次空冷加水淬使工件内的温度梯度下降 ;而工艺c使已转变的马氏体和贝氏体产生自回火。

预硬型塑料模具钢718的切削性能和夹杂物研究

对预硬型塑料模具钢ASSAB718和国产的GC718的切削加工性能进行了对比性研究 ,并结合Thermo Calc软件对钢中非金属夹杂物进行了分析。结果表明 ,由于钢中夹杂物的影响 ,ASSAB718钢的切削加工性能优于GC718钢 ;运用Thermo

塑料模具钢大模块的水冷复合间隙淬火技术

以计算机模拟为基础,在大模块塑料模具钢的热处理过程中,采用复合水冷替代传统的水淬油冷,研制了相对应的生产设备以及控制工艺,并已成功应用于工业生产中。

2311和2738模具钢热处理质量效应的数值模拟

利用数值模拟技术对 2 311和 2 738两种模具钢热处理质量效应进行了定量评估和现场试验验证。在此基础上对不同规格模坯材料及其回火工艺参数选择提出了具体建议 。

晶粒尺寸对贝氏体钢SDP1的连续冷却转变规律的影响

采用热膨胀仪测量了150μm和20μm大小两种晶粒尺寸的SDP1贝氏体钢的过冷奥氏体连续冷却转变(CCT)曲线,结合组织观察、硬度测试、热力学计算及动力学分析研究了晶粒尺寸对相变过程组织和硬度的影响。结果表明,小晶粒材料在低冷速相变过程中出现了片状珠光体,最低硬度为305HV,贝氏体转变对应冷速区间较小;大晶粒材料在各冷却条件下无珠光体产生,且贝氏体转变区较大,最低硬度为423HV。150μm和20μm晶粒材料的贝氏体相变激活能分别为124kJ·mol^(-1)和134kJ·mol^(-1)。

塑模钢P20BSCa合金化特点及热处理工艺的研究

分析了预硬型大截面塑料模具钢Ｐ２０ＢＳＣａ的合金化特点，并对热处理工艺进行了研究．结果表明，该钢具有优良的热处理工艺性能及预硬性能，淬火温度区间宽，适当地调整回火温度，可以很方便地得到ＨＲＣ３０～４５的预硬硬度要求；

贝氏体预硬型塑料模具钢大模块硬度与组织分析

对860 mm厚非调质预硬型塑料模具钢(NQP钢)大模块进行解剖,测定了模块截面硬度、碳含量,并对不同部位的组织进行了金相观察,测定了该钢的CCT曲线。结果表明:整个模块截面碳偏析程度在0.04%～0.06%,碳含量分布规律与硬度分布规律一致;CCT曲线表明其具备良好的淬透性,在0.015～0.1℃/s的冷速范围内可获得完全的贝氏体。分析其截面硬度波动在±1.5 HRC内的原因在于此钢具有较好的贝氏体淬透性,大模块整个截面上都获得了均匀的贝氏体组织,能满足大截面塑料制品行业的使用要求。

718塑料模具钢大模块淬火工艺的优化

718塑料模具钢在制造模具前需要进行淬火及回火预处理,使硬度达到29～35HRC,要求同一截面的硬度差不大于3HRC。然而对于大型的模块难以制定合理的预硬化工艺来保证硬度均匀一致且无淬火裂纹。为了改进并优化预硬化工艺,对718钢大模块淬火过程的瞬态温度场及组织场进行了耦合数值模拟。通过比较三种不同淬火工艺的模拟结果,为718模具钢大模块设计了一种较佳的淬火工艺,即淬入水中之前先在空气中预冷,淬水之后将模块出水在空气中自回火。