简介:ProblemsaboutsurfacemountingprocessforfinepitchdevicesandreasonsonsolderbridgingofLtypeleaddevicesweldedaredepicted.Bridgingmechanismandinfluencefactorsareanalyzedwithtwo-dimensionalgeometricmodel.Basedonthis,high-densitysurfacemounttechnology(SMT)forfinepitchLtypeleaddevicesheatedbyscan-ninglaserisraised.SurfacemountprocessforQFP208onprintedcircuitboard(PCB)isstudied.Theresultsoftestsarethatitisquitepossibletosolvethesolderbridgingofsurfacemountingforpitchdeviceswithscanninglaser-heat-ingmethod.
简介:Ultra-finetitaniumcarbonitride(TiCN)matrixmaterialswithagrainsizelessthan1μmweresuccessfullypreparedbyvacuummicrowavesintering.ThemillingprocessforrawTiCNparticlesandthemicrostructureandpropertiesofcermetsproducedwithacompositionof15wt.%WC-17wt.%(Co+Ni)-9wt.%Mo2C-59wt.%Ti0.7N0.3andsinteredbyvacuummicrowavewereanalyzedbyscanningelectronmicroscopy(SEM)andX-raydiffraction(XRD).Theresultsshowthataball-to-powdermassratioof8:1andamillingtimeof50hprovidedappropriateconditionsfortheproductionofultra-fineTiCNsolidsolutionpowders.Theuseofvacuummicrowavesinteringproducedcermetswithmuchfinergrainandblackcorestructuresandhigherrelativedensityandhardnessthanthoseproducedbyvacuumsinteringtechnology.
简介:前不久,中国航天科技集团公司第六研究院第十一研究所发来感谢信,对中国科学院兰州化学物理研究所为2016年6月25日长征七号运载火箭的成功发射所作出的贡献表示感谢。
简介:Inthisessay,westudiedhowheatinputaffectedthemicrostructure,hardness,grainsizeandheat-affectedzone(HAZ)dimensionofWCX355ultra-finegrainsteelwhichwasweldedrespectivelybytheultranarrow-gapwelding(UNGW)processandtheoverlayingprocesswithCO2asprotectiveatmosphereandlaserweldingprocess.Theexperimentalresultsshowwhentheheatinputchangedfrom1.65kJ/cmto5.93kJ/cm,thewidthofitsHAZrangedfrom0.6mmto2.1mm.Theaveragegrainsizegrewupfrom2~5μmofbasemetalto20~70μmandfoundnoobvioussoftenphenomenoninoverheatedzone.Thewidthofnormalizedzonewasgenerallywideas2/3asthatofthewholeHAZ,andthegrainsizeinthiszoneissmallerthanthatinbasemetal.Underthecircumstanceofequalheatinput,theHAZwidthofUNGWisnarrowerthanthatofthelaserwelding.
简介:Theultra-finegrain(UFG)steelisweldedbyusingresistancespotweldingtechniquewithorwithoutrequirementofupsettingforce.Metallographicinspectionshowsthatthegrainsizeofweldnuggetislargerthanthatofthebasemetalandthemicrostructureisalteredsignificantly.Inaddition,contractingdefectssuchasairholescanbefoundinthenuggetcenter.Theexperimentsshowthatthedefectscanbeeffectivelyavoidedbythetechniqueofaddingupsettingforceduringthenuggetcoolingandcrystallizingprocesses.Intensilesheartests,theweldingjointstartstocrackfromtheinneredgeofthecoronabond.Theresultsofmicro-hardnesstestsshowthatthenewlybornmartensitestructuredramaticallyimprovesthehardnessofthejoint.Undertheinteractionsbetweenresidualstressesandregeneratedfinegrains,themicro-hardnessoftheheat-affectedzone(HAZ)islowerthanthatofthenugget,butevidentlyhigherthanthatofthebasemetal.
简介:93W-4Ni-2Co-1Fe的微观结构和性质(集体部分,%)重合金由机械alloying和电流准备了的钨从混合元素的粉末激活sintering被调查。在15hmilling以后,在粉末的平均W谷物尺寸被减少到120nm。为为15h,密度,坚硬和横向的破裂的粉末milled,仅仅由集中的脉搏电流的合金sintered的力量是最大值。当全部的sintering时间保持不变时,sintered合金的性质能被优化脉搏水流的sintering时间显然改进并且经常水流。体积有大约340nm的一种平均W谷物尺寸的极其细小的合金能被在全部的sintering的15工厂h的粉末6min预定的sintering获得。相应sintered密度,坚硬和横向的破裂力量分别地到达16.78g/cm3,HRA84.3和968MPa。
简介:深圳雷地科技实业公司收到中国人民解放军总装备部航天医学工程研究所的感谢信,感谢雷地公司“协作配套研制的产品参加了我国首次载人航天飞行任务。在神舟五号飞船测试、发射、运行和回收的各个阶段,产品性能稳定,工作正常,有力地配合了我所圆满完成本次意义重大的参试任务。”原来,航天员杨利伟头盔面罩上的“保护膜”及宇航服上金属部件的表面处理,就是雷地公司研制完成的。