闭塞冷锻行星齿轮齿形修正方法研究

针对闭塞冷锻行星齿轮齿形修正方法进行了研究.利用弹塑性有限元法模拟了行星齿轮闭塞冷锻过程,采集成形终了前两步工件表面各点处的接触应力作为模具弹性变形分析的边界条件,对模具进行弹性有限元分析.获得了模具弹性变形分布图,提取了齿形凹模齿长平分截面由齿根至齿顶的齿厚弹性变形量.以变位修正法为指导思想,提出了齿轮闭塞冷锻齿形凹模新的修正设计方法,并获得了试验验证.     

MB2镁合金变形组织性能研究

为了探讨镁合金铸造组织在较低温度下变形时对组织性能的影响,采用现代冶金分析和测试方法,研究了MB2镁合金铸棒在不同变形温度和变形程度下组织演变过程和再结晶行为,并对各变形条件下试样进行拉伸实验.结果表明,通过挤压变形及动态再结晶,可以显著细化铸造MB2合金的晶粒,其尺寸可由铸态的约100 μm减少到5μm;随变形温度的升高,MB2合金的抗拉强度下降,达到一定温度后,趋于稳定;在相同的变形程度下,随着变形温度的升高,晶粒有长大的趋势.     

Numerical and experimental investigation of cold rotary forging of a 20CrMnTi alloy spur bevel gear

Due to the complex three-dimensional (3D) geometry and tooling design, mass production of precision spur bevel gears by machining or conventional forging technology is impeded by numerous stubborn barriers to date. Cold rotary forging, an innovative incremental metal forming process, has great potential to improve the current situation owing to its flexibility and low tool load requirement. In the present study, a sound 3D rigid-plastic finite element (FE) model of cold rotary forging of a 20CrMnTi alloy spur bevel gear is developed under the DEFORM-3D platform. To ensure the precision of the proposed FE model, a series of experiments are well performed for the identification of the mechanical properties of 20CrMnTi alloy and the realistic friction conditions prevailing at the die-workpiece interface. By utilising this FE model, the workpiece geometry is optimised with the intention of achieving a better filling of gear shape and a lower forming load requirement, and then the distribution of different field-variables such as flow velocity and effective strain are thoroughly investigated. For verification purposes, the cold rotary forging experiments of 20CrMnTi alloy spur bevel gears are subsequently conducted. Good agreement between the experimental results and the simulation ones is highlighted by comparing the gear shape after cold rotary forging and the axial forging force, which validates employed model.     

锻造对30CrNi2MoV钢在亚温淬火下组织与性能的影响

30CrNi2MoV钢是一种中碳合金钢,常用于制造高强韧性的大型锻件,广泛用于制造火电、核电等电站装备和大型冶金、矿山和运输装备中的承力和传动结构部件.为提高30CrNi2MoV钢的低温冲击韧性和室温强度,本文采用金相显微镜、扫描电子显微镜、拉伸机和硬度仪等方法对其进行组织观测、断口形貌分析和力学性能测试,研究了不同锻造方式对30CrNi2MoV钢的组织与力学性能的影响.结果表明:经过2次镦粗的30CrNi2MoV钢再经1次镦粗或1次镦粗+1次拔长两种锻造方式后能够有效细化且均匀晶粒,提高晶粒等轴性;与2次镦拔工艺的30CrNi2MoV钢相比,再经过1次镦粗或1次镦粗+1次拔长后其抗拉强度、延伸率和冲击韧性分别由1 043.6 MPa、35.65%和40.33 J提高至1 161.6和1 157.4 MPa、37.80%和36.13%、103和87 J.数据表明,30CrNi2MoV钢经过2次镦拔+1次镦粗工艺后,其组织与力学性能达到最好状态.     

铁路车辆销类件摆辗精密成形及新型摆辗机研制

实验研究了铁路车辆销类件拔摆类件冷拔摆辗精密成形工艺，对工艺参数的确定和产品质量问题进行了分析，并研制了适合该工艺的新型摆辗机，结果表明：采用摆辗工艺生产销类件具有金属流线不易破坏，表面硬度略有升高，尺寸精度和表面粗糙度达到有关标准要求，综合机械性能有所提高等,析型摆辗轨具有液压踊跃式静压球形轴承摆，玫瑰线轨迹，大行程和圆形民轨结构，适用于销类件等法兰长杆件的加工。     

Effect of multidirectional forging on microstructures and tensile properties of a particulate reinforced magnesium matrix composite

A particulate reinforced magnesium matrix composite prepared with stir casting was subjected to multidirectional forging (MDF). The results showed that after 1 MDF pass the grain size of matrix in the composites decreased compared with as-cast composite, and increased with increasing the MDF temperature from 370 °C to 450 °C. With increasing the MDF passes at 370 °C, the particle distribution of the composite was improved until 3 MDF passes while the grain size of matrix in the composite reached a minimum after 4 MDF passes. Both the yield strength and the ultimate tensile strength of the composite were enhanced with increasing the MDF passes.     

Effect of degree of cold work and annealing temperature on the microstructure and properties of cold drawn copper wires and tubes

This work gives the results of influence of temperature and deformation degree on changes in the metal grain growth of drawn copper products, because this mutual dependence was observed. Wire samples of O.F.H.C. copper and copper tube samples, chemical content of 99·97% Cu and 0·024% P, were exposed to recrystallized annealing after drawing. The annealing was carried out at temperatures of 400, 450, 500, 550 and 600°C, for 30 min, in laboratory conditions. Investigation results show that after drawing with high cold deformation degree (96–99%), the annealing leads to the changes in the continuous grain growth with increased temperature. The smaller grain size appears at 550°C in comparison with the lower annealing temperature. Annealing has influence on mechanical characteristics of tested samples and during drawing of copper products these characteristics are adequately changed: with regard to the annealing at the 500°C, the characteristics of strength and plasticity increase as a result of decreased grain size. The increase of annealing temperature to 600°C leads to the increased grain size and decreased values of strength and plasticity characteristics.     

冷轧Cu基原位复合材料组织演变及性能研究

采用冷拉拔与冷轧相结合的变形方式将Cu-15Cr-0.24Zr合金制备成纤维增强复合薄板材料.采用扫描电子显微镜(SEM)对不同变形量下Cr纤维的形态进行观察,利用拉力试验机和电阻率测试仪对不同变形量下的薄板材料进行抗拉强度和电阻率测试.结果表明:冷拔变形量为5.18时,枝晶Cr已经具备了纤维的基本形貌,但纤维不连续,呈竹叶状;冷轧变形量为91.6%时,形成了均匀、连续的Cr纤维,并且由竹叶状演变为板条状;在冷轧变形量为91.6%时,成功制备出抗拉强度大于800 MPa,导电率大于70%IACS的Cu-15Cr-0.24Zr薄板材料.     

变形程度对复杂铝合金锻件组织性能的影响

为确定最佳成形工艺,通过拉伸试验、金相观察、TEM和SEM观察等方法,研究了不同制坯变形程度对7A09铝合金复杂筋板类锻件组织性能的影响.实验结果表明:随着制坯变形量的增加,所得锻件的强度和硬度升高,而塑性和抗应力腐蚀性能下降;随制坯变形程度的增加,热变形时储存的变形能增多,可以得到更加细小的晶粒,而且储存变形能的增多有利于固溶程度的提高和强化相的析出,因而可以提高锻件的强度和硬度.晶粒细化使晶界面积增加是造成电导率降低的主要因素.因此,在设计成形工艺时,应根据零件按上述规律来调整变形程度.     

刚玉系抗弹陶瓷的显微结构与性能研究

研究了95瓷、99瓷、铬刚玉瓷和钒刚玉瓷等刚玉系抗弹陶瓷的显微结构与性能的影响关系。结果表明有效添加剂可以改善陶瓷的显微结构，提高其力学性能和抗弹能力，为研制高性能抗弹陶瓷提供了有效途径。     

粒度对纳米掺杂BaTiO3陶瓷结构和性能的影响

制备了纳米掺杂BaTiO3陶瓷,研究了纳米掺杂剂和BaTiO3的粒度对BaTiO3陶瓷的微观结构和介电性能的影响．结果表明,小粒度、高分散的纳米掺杂剂更易对BaTiO3颗粒实现均匀包裹,有效地抑制晶粒生长并形成更多的壳-芯晶粒,大比表面积使更多高活性的表面原子与BaTiO3发生原子输运形成传质,导致晶粒壳／芯比增大,从而提高其介电性能．纳米掺杂陶瓷的平均晶粒尺寸和四方率与BaTiO3粒度几乎成正比．随着BaTiO3粒度的减小,立方晶粒壳增大而四方晶粒芯减小,陶瓷由四方晶相向赝立方晶相转变,居里峰被显著压制,从而改善介电温度特性．同时,晶粒的壳与芯之间失配产生的内应力随之增加,使居里点向高温方向移动．