Microstructure characteristics and mechanical properties of steel stud to Al alloy by CMT welding-brazing process

Cold metal transfer(CMT) welding of nickel-coated Q235 steel studs with 6061 Al alloy was carried out using ER4043 as filler metal.The welding process was stable,and appearance of weld formed well without surface defect under the parameters of welding current 121 A,welding voltage 15.4 V and welding speed 6 r/min.The microstructure of filler metal was analyzed by means of scanning electron microscopy.The filler metal and 6061 Al alloy were fused to form fusion welding interface,the fusion zone had a good bonding without any micro defect.The steel stud did not melt and brazing interface was formed between the filler metal and steel stud.Two different reaction layers existed in the brazing interface,the Fe_2Al_5 layer about 10- 12 μm formed near the steel stud side,and the other layer was mainly composed of FeAl_3.Nickel-rich zone was formed in the root toe area of the fillet weld,which was mainly composed of Al_3Ni_2.The tensile tests showed that the maximum shearing strength of the joints was 129 MPa.The joint was brittle fractured in the intermetallic compound layer where plenty of FeAl_3 were distributed continuously.     

变频器在小流量恒压供水系统中的应用

传统的小区多泵组恒压洪水系统大多没有设置小流量水泵，造成小流量供水时段较大的电能浪费，本文结合某生活小区的变频供水系统，介绍了小流量变频供水系统设计及控制功能。     

变频器在制药行业的应用与选型

变频调速技术是针对固定工频而采取的高效节能措施,工频(50Hz)是发电的最佳频率,但它并非是所有用电设备的最佳工作频率,因而导致许多设备长期处于低效率、低功率因数运行状态。占全国耗电近2/3的交流电动机目前大多数还在工频、恒速下运行,运行效率只有60%左右。