镁合金与铝合金压铸过程中型腔内压力的变化特性

对相同压铸条件下ADC12铝合金和AZ91D镁合金铸件型腔内的压力变化进行了比较研究.从高温液态到低温固态,铝、镁合金的压力曲线可划分为6个区,在实验分析结果的基础上定义了相应的特性参数.压铸充型过程中两种合金的充填压力和充填时间基本一致,压力曲线变化趋势也一致.压力曲线测试结果表明,铝合金的保压时间和有效压力保持时间远远高于镁合金.对于不同测试点的最大增压压力, ADC12铝合金比较接近, AZ91D镁合金相差较大.金属液凝固特性及合金力学性能的不同决定了两种合金压力益线的差异.

减速减压工艺对镁合金压铸件质量与性能的影响

以镁合金发动机缸盖罩盖为研究实例,对镁合金压铸过程中减速减压工艺对型腔内压力变化、铸件外观质量、铸件性能、铸件内孔洞的影响进行了研究。结果表明:镁合金压铸充型过程中采用减速或减压工艺会造成型腔内充填压力降低,导致铸件表观质量下降;分别采用减速或减压工艺,型腔内的增压压力稍有降低,铸件内孔洞数量和尺寸稍有增加,铸件强度和密度随之降低;同时采用减速和减压工艺,型腔内充填压力和增压压力显著下降,铸件内孔洞数量和尺寸明显增加,铸件强度和密度随之显著下降。

Influences of Casting Pressure Conditions on the Quality and Properties of a Magnesium Cylinder Head Cover Die Casting

Casting pressure conditions have great influences on the casting defects, such as gas porosity, shrinkage porosity and gas holes. A Mg cylinder head cover die casting was used to experimentally study the influences of casting pressure, the loading time and the piston position of pressure intensification on the variation of pressure and the quality of casting. The results show that casting pressure, the loading time and the piston position of pressure intensification have great influences on the pressure variations in the mold, the quality and performance of casting. The external quality, the density and the tensile strength of casting were improved with the increase of casting pressure and the piston position of pressure intensification and the decrease of the loading time of pressure intensification.

绢丝、棉、熟丝的包芯双股纱

通过改善绢丝纱的性质，可以改善绢丝织物的硬挺性，在过去，绢丝织物的柔软手感是它的致命弱点。而且，为了扩大蚕丝的最终用途，也必须发展具有与传统的纱线不同特性的新的纱线。