原位合成WC-6Co复合粉末制备超细YG6硬质合金

将原位合成WC-6Co复合粉末采用干袋式冷等静压压制成型(压制压力1×10~8 Pa、保压时间15 s),将压制好的坯料采用低压烧结炉烧结(烧结温度1360℃、烧结时间40 min、加压5 MPa、保温保压时间20 min),烧结制备超细YG6硬质合金,对合金的形貌、金相组织及物理力学性能进行分析。结果表明:原位合成WC-6Co复合粉末制备的超细YG6硬质合金,晶粒异常长大,WC平均晶粒尺寸为0.8μm,硬度HV_(30)为(21500±100) MPa,较传统超细YG6X硬度高。再将WC-6Co复合粉末采用滚动湿磨、压力式喷雾干燥、掺成型剂、挤压成型、低压烧结等工序制备超细YG6硬质合金,研究不同晶粒长大抑制剂配比、球磨时间、挤压压力、烧结温度对合金性能的影响。结果表明:添加0.3%VC、0.8%Cr_3C_2(质量分数),湿磨48 h,挤压压力24 MPa,烧结温度1340℃,制备的超细YG6硬质合金WC晶粒均匀,无异常长大的WC晶粒,WC平均晶粒度尺寸0.4μm,呈多边形,外形较圆。强度、硬度最高,抗弯强度TRS为(2250±20) MPa、硬度HV30为(22600±100) MPa。断口形貌为沿晶断裂,沿WC与WC晶界断裂或WC与Co晶界断裂。     

X70管线钢熔合区裂纹与焊接工艺的关系 孙咸

探讨了X70管线钢中熔合区裂纹与焊接工艺的关系。结果表明,在铁研试件中出现的沿熔合线分布的裂纹属于氢致冷裂纹。当冷裂纹三要素集中于X70管线钢熔合区的粗晶区时,该区成为接头的薄弱环节,极易形成裂纹。在裂纹影响因素中,熔合区组织特性是裂纹产生的必要条件,应力水平和氢的分布特征则是充分条件。焊接工艺与裂纹的关系实质上反映的是焊缝中氢和应力与裂纹间的关系。工程上常用焊缝中残留的扩散氢量最小化、不足以引发氢致冷裂纹的“焊缝金属低氢化”综合工艺,并获得了满意的效果。     

浅析罩式退火炉加热时间的影响因素

本文简要分析了影响罩式退火炉加热时间的因素,为罩式炉的生产操作提供参考。     

钛在F—22先进战术战斗机上的应用

在Ａｌ－Ｌｉ二元单晶体的锯齿流变中，锯齿类型决定于加载的应变速率，与锯齿产生的临界应变随温度和应变速率的变化没有对应关系；锯齿序列中的应力幅度随时效时间的变化较大。     

A numerical study of various plastically unstable behaviors in tension and compression

Various types of behavior due to plastic instability under uniaxial tension and compression are numerically investigated regarding sheet materials, plane strain blocks, and cylindrical bars and hollow cylinders. The code GOLDA for analysis of large elastic-plastic deformation previously developed by the author is used, which is one of quasi-static explicit FEM programs. Both of diffuse type and localized type of instability are concerned with. The role of vertex-hardening in plastic instability is payed attention, by using the J2G (J2-Gotoh’s corner theory) as the plasticity constitutive equation, which was proposed previously by the author and is a kind of vertex-hardening theory. Following results are mainly derived. 1) In plane strain tension, shear-type strain localization is realized by the use of J2G, but not by the conventional J2F (J2-flow theory). In axisymmetric tension of a cylindrical solid bar, however, such strain localization would never appear even by J2G, as expected by the experiment. 2) In axisymmetric tension of a hollow cylinder under the condition of no contractlion of its bore (therefore, in almost plane strain state with no circumferential strain), it is found that shear-type strain localization could occur. This is realized again by the use of J2G, whereas J2F never allows such strain localization. 3) In compression under the embedded edges condition, it is found that a sheet with initial aspect ratio of 2:1 (in height:breadth) yields double barreling, whereas a plane strain block yields double barreling at the initial aspect ratio of 3:1, not at 2:1 though expected from the conventional slip-line theory. As for a cylindrical solid bar, double barreling appears for the initial aspect ratio of 2:1 but only for higher n-vaiue (the strain hardening exponent), say n=0.5. 4) As for barreling mode, when thick-walled axisymmetric tubes with the initial ratio of thickness to inner diameter 1/5 to 1/3 are compressed axially, corresponding to the initial aspect ratios of 3:1, 2:1 and 1:1, triple barreling, double barreling and single barreling appear, respectively. 5) It is found that thin-walled tubes buckle in a progressive periodic mode with almost stationary compressive load under axial compression. Thus it can be used as a simplified model for buckling of more complex structures such as the honeycomb.     

Sm(Co_(bal)Fe_xCu_(0.088)Zr_(0.025))_(7.5)(x=0-0.30)烧结永磁体的磁性及其高温特性

用粉末冶金工艺制备了Sm（CobalFexCu0.88Zr0.025）7.5（x=0-0.30）烧结磁体,对Fe含量x对磁体的磁性及其高温特性的影响进行了系统研究.随Fe含量的增加,最大磁能积（BH）max和剩磁Br逐渐增加,分别在x为0.21和0.27时达到了最大值205kJ/m3和1.055T,然后迅速下降.当x≥0.24时,磁体中开始有FeCo软磁性相析出,破坏了磁体的永磁特性.Fe含量对磁体高温稳定性有巨大的影响,在Fe含量x=0.21时,磁体内禀矫顽力温度系数β为-0.23％/K;当x=0.07时,β降至-0.14％/K（293-723K）.制备出有很好的高温稳定性的永磁材料Sm（CobalFe0.07Cu0.088Zr0.025)7.5,在723K时其磁性能为:Br=0.725T,bHc=517kA/m,iHc=764kA/m,（BH）max=95 kJ/m3,B-H退磁曲线保持为直线.     

环保型水溶性带锈防锈涂料的研制

为省去除锈除油等表面预处理工序，以简化涂漆工艺，减轻劳动强度，降低涂装成果，采用改性脲醛树脂作为水溶性带锈涂料的成膜物与转化液的最佳配比，研制出一种环保型水溶性带锈防锈涂料，较好地解决了水溶性带锈涂料耐水性和装饰性差的问题。     

一种新型混合输入式曲柄压力机的研究

介绍一种新型混合输入式曲柄压力机 ,根据压力加工工艺对滑块运动速度特性的要求 ,运用复数矢量法对该混合输入机构进行逆运动学分析 ,求解出伺服电机满足加工工艺要求时的实际运转情况 ,通过求得的伺服电机转角函数控制滑块运动。并对伺服电机和恒速电机功率分配问题进行了研究。通过研究表明 :这种新型混合输入式曲柄压力机可以满足多种冲压加工工艺对零件变形过程中速度变化特性的要求。     

单刚矩阵计算用神经网络结构的实验确定

提出将BP网络与函数型网络相结合用于有限元单元刚度矩阵的实时计算,给出了网络结构的设计依据,对不同阶数输入向量的网络的收敛速度进行了对比分析,为网络输入参数数目的确定提供了参考。     

基于模糊分析的环形起重机偏轨箱形主梁的优化设计

这里就环形起重机偏轨箱形主梁的设计问题,根据模糊分析的基本理论提出一种模糊优化设计方法。即在普通优化设计基础上考虑设计取值的不确定性以及影响设计的某些因素如应力性质、材质好坏又很难用确定的数值表示的情况,建立了模糊约束条件。在满足使用要求的前提下,以偏轨箱形主梁的总质量最小的优化目标,建立了该问题的模糊优化设计数学模型,并介绍了优化方法和效果。