Effect of hot-dip galvanizing processes on the microstructure and mechanical properties of 600-MPa hot-dip galvanized dual-phase steel

A C-Mn dual-phase steel was soaked at 800℃ for 90 s and then either rapidly cooled to 450℃ and held for 30 s (process A) or rapidly cooled to 350℃ and then reheated to 450℃ (process B) to simulate the hot-dip galvanizing process. The influence of the hot-dip galvanizing process on the microstructure and mechanical properties of 600-MPa hot-dip galvanized dual-phase steel (DP600) was investigated using optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and tensile tests. The results showed that, in the case of process A, the microstructure of DP600 was composed of ferrite, martensite, and a small amount of bainite. The granular bainite was formed in the hot-dip galvanizing stage, and martensite islands were formed in the final cooling stage after hot-dip galvanizing. By contrast, in the case of process B, the microstructure of the DP600 was composed of ferrite, martensite, bainite, and cementite. In addition, compared with the yield strength (YS) of the DP600 annealed by process A, that for the DP600 annealed by process B increased by approximately 50 MPa because of the tempering of the martensite formed during rapid cooling. The work-hardening coefficient (n value) of the DP600 steel annealed by process B clearly decreased because the increase of the YS affected the computation result for the n value. However, the ultimate tensile strength (UTS) and elongation (A₈₀) of the DP600 annealed by process B exhibited less variation compared with those of the DP600 annealed by process A. Therefore, DP600 with excellent comprehensive mechanical properties (YS=362 MPa, UTS=638 MPa, A₈₀=24.3%, n=0.17) was obtained via process A.     

陶瓷材料及其连接

本文通过对氧化物陶瓷和非氧化物陶瓷材料所具有的优良特性和用途的多样性、可变性等方面的论述,阐明了陶瓷材料将成为一种非常有发展前途的工程结构材料材和功能料。并根据陶瓷材料离子结合键和表面润湿性差等特点,指出了已获得应用和正在研究开发的焊接、固体连接、熔接和表面涂层等陶瓷的各种连接方法的本质及适用条件。     

需求率符合产品寿命周期的库存问题的最优控制

本文给出了用三次函数近似拟合需求率符合产品寿命周期变化规律的库存模型，得到了这一模型的整体最优解，并付诸实际应用.     

1Cr17Ni13Mo2Ti焊缝冷弯及冲击韧性研究

本文进行了A212,A207焊条手工焊接和TIG焊焊接1Crl7Nil3Mo2Ti焊缝的冷弯和冲击韧性试验,分析了焊缝显微组织和冲击断口,测定了焊缝中的δ铁素体和氧含量。研究结果表明,用低氢型A207焊条和TIG焊焊接的焊缝中氧含量降低,夹杂物含量减少,焊缝中δ铁素体含量减少,其分布和形态明显改善。因而焊缝在延性断裂过程中裂纹形核核心减少,韧窝尺寸增大,塑性变形程度增大,断裂吸收功增加,焊缝的冷弯和冲击韧性明显改善。     

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提高电力线路环网供电可靠性对于环网的实际应用具有十分重要的意义，本从一个比较新颖的技术角度出发，提出了一种环网线路的快速故障诊断方法，其具有结构简单、可靠，对线路拓扑结构的适应好等特点。     

分布式图文数据库系统DGRDBMS的设计

探讨了基于关系数据库系统的扩展关系模型的建立，具有统计数据、图形、图象等多种类型的图文数据的存储管理，多种专题图的图形数据组织方法，分布式系统环境下通信方式的实现和数据库操作的并行分布处理等问题，最后建立了分布式图文数据库管理系统ＤＧＲＤＢＭＳ．     

CAN总线通信技术在LTU90A智能摊铺机中的应用

采用EPEC2000系列车用微处理器模块,开发了LTU90A智能摊铺机,实现筑路工程机械自动控制;在通讯硬件平台的支持下,便于筑路机群各机种间通讯和远程故障诊断,有利于提高摊铺机路面施工质量和效率;针对EPEC车用模块,分析了CODESYS编程软件的开发、用户程序的设计及系统函数库的调用;利用CAN总线通讯技术在通讯过程中具有的可靠性、实时性和灵活性的特点,采用CAN网络结构和CAN2.0B数据包的定义,将数据传送分为3种发送级别.由于摊铺机工作环境恶劣,为了提高系统通讯的可靠性,在CAN的MAC层已具有CRC校验的基础上,增加一级求和取模校验措施.实践结果表明,CANBUS系统可靠性高,便于扩充,实时性好.     

低气压等离子喷涂TiO_2涂层机械性能的研究

文本通过实验研究,证明了在低气压等离子喷涂条件下,TiO_2涂层的机械性能不是依赖于涂层结构,而主要由形成涂层前的TiO_2粒子的温度和速度所决定;如果形成涂层前的TiO_2粒子温度越高并且速度越大,就能形成更加扁平状粒子的涂层,增加粒子间结合力,使涂层机械性能提高。因此,喷涂规范中的等离子弧功率、喷涂距离和喷涂室压力对涂层机械性能有较大影响,而等离子弧辅助气氢气流量的影响甚小。     

HF radar sea clutter rejection by nonlinear projections

1.INTRODUCTION Utilizingverticalpolarizedelectromagneticwavethat canfollowthecurvatureoftheearthalongtheair wa terinterfacewithlowpropagationlossonhighlycon ductiveoceansurface,highfrequencyground wave radar(HFGWR)isdesignedtodetectandtracktar getsbeyondthehorizonsuchasvesselsovertheseaor aircraftsatlowaltitude.Thereforemoreandmore countriesdevotemuchenergytodevelopHFGWRin recentyears.However,HFGWRhascontinuedtobe seriouslylimitedbyahighthresholdofdetectionin seaclutter.Dominatingth…     

Ni-Fe-(Zr)-Si-B非晶合金的等温晶化与结构转变

采用旋铸急冷工艺在大气环境中制备出了(Ni0.75Fe0.25)78-xZrxSi10B12(x=0、8)非晶合金带材.X射线衍射分析表明样品为完全非晶.采用Diamond TG/DTA差热分析仪测量非晶薄带的热稳定性及其相关参数Tg、Tx、Tm等.根据DTA结果分析,(Ni0.75Fe0.25)78Si10B12非晶合金退火温度为695、715、7457、65 K.在715 K和745 K退火时,非晶基体上析出单一的-γ(Fe,Ni)固溶体,平均晶粒尺寸分别约为10.3 nm和18.5 nm,在765 K退火后的结晶相为-γ(Fe,Ni)固溶体以及Fe2Si,Ni2Si和Fe3B.(Ni0.75Fe0.25)70Zr8Si10B12非晶合金退火温度为810、825、845、855、865、920 K,退火后不能在非晶基体上析出单一的晶化相,晶化析出相为-γ(Fe,Ni)固溶体以及Ni21Zr2B6,Fe5Si3,Ni3Zr和一些未知相.