Effect of solution annealing on weldability of aged alloy 800/25Cr–35Ni steel dissimilar welds

Abstract

Dissimilar welding of the aged alloy 800 and the as cast 25Cr–35Ni (wt-%) heat resistant steel was investigated. Microstructures, mechanical properties and weldability of the dissimilar welds were characterised using optical microscopy, scanning electron microscopy and transition electron microscopy equipped by energy dispersive X-ray spectroscopy, and Varestraint test. Since such dissimilar welding was susceptible to crack formation in the heat affected zone of the aged part, the effects of a preweld solution annealing, heat input, interpass temperature and type of filler metal on the weldability of two alloys were investigated. It was found that during the solution treatment, the precipitates produced in the service stage were decomposed and that TiC was formed. In addition, tensile strength and hardness were reduced, but ductility and toughness increased. It was concluded that the most important step to improve weldability and to reduce cracking susceptibility was solution annealing. A suitable annealing treatment was then proposed. The best weldability was found under conditions of solution annealing, low heat input, low interpass temperature and using Inconel 82 or 617 for filler metals.     

Passivation degradation of Alloy 800 on nucleate boiling surface

In this work, the passivation degradation of Alloy 800 on nucleate boiling surface was studied by using polarisation curve, electrochemical impedance spectroscopy and secondary ion mass spectrometry. Experimental results indicated that boiling bubble would significantly degrade the passive film, as indicated by a decreased pitting potential and increased passive current density. Under boiling condition, the mass transfer of electrolyte is accelerated and the temperature of Alloy 800 was increased, as a result, the cathodic reaction and the dissolution rate of the passive film were increased. The passive film was Cr-depleted but Ni- and Fe-enriched, and the decreased Cr content in the passive film led to a degraded passive film.     

800H合金长时间蠕变下的显微组织

对低负荷长时间蠕变试验下800H合金显微组织的研究表明:空洞在晶界M_(23)C_6碳化物的一侧形成,微裂纹通过一连串这样的小空洞而发展;晶界M_(23)C_6碳化物和相邻两晶粒之一有共格关系而与另一晶粒无共格界面,共格界面强化了晶界,这一强化作用可用蠕变激活能的提高来说明,晶界还有G相析出,但未发现合金中有γ'相的形成。合金能长时间保留网状的位错结构,晶界碳化物附近有位错塞积,亚晶界结构发展不充分,这与典型的回复蠕变是不同的。     

SUPMAX800在轨道交通通信系统中的应用

城市轨道交通通信系统是一个庞大复杂的系统,它包含了电源、电视、广播、传输等子系统,其每一个子系统都包含一个独自的监控系统。基于SUPMAX800分散控制系统平台,将通信系统的各个子系统的数据和告警通过各种不同的方式接入到系统平台,构成了轨道交通通信系统的集中监视和统一告警系统。控制中心值班员通过一台终端,就可以监视到整个通信系统的重要数据和告警。该套系统目前已经应用于上海轨道交通四号线通信系统。     

ACS800在3400／250三叠网多缸纸机负荷分配中的应用

介绍了ACS800直接转矩控制变频器在3400/250三叠网多缸纸机负荷分配中的应用,就通讯、联锁、参数设置及使用中的注意事项等问题进行了讨论。     

VxWorks下数据采集卡设备驱动程序开发

在Tornado环境下,开发了盛博ADT800数据采集卡在PC104下的VxWorks驱动程序。描述了嵌入式实时操作系统Vx-Works中的字符设备驱动体系结构,开发过程,驱动中的查询、中断模式。该驱动统一了编程接口,极大地方便了其它人员的进一步开发。     

Incoloy 800H合金的应用和性能分析

通过对耐热耐蚀合金Incoloy 80 0H的性能分析 ,指出它与普通奥氏体不锈钢相比具有较优的抗氧化性能、耐蚀性和高温蠕变强度。针对催化裂化装置同轴式沉降再生器内部所用Incoloy 80 0H焊件易出现裂纹的问题进行分析 ,认为在施焊过程中由于合金凝固时有低熔点金属或化合物的液态膜残留在晶界区 ,该合金具有高的焊接热裂纹敏感性 ,若焊材选择不当 ,焊丝填充不充分、缺少保护气等将导致晶间裂纹产生。提出了该合金采用TIG焊接防止热裂纹产生的措施。     

ACS800多传动系统在纸机速度控制中的应用

对ACS800多传动系统的组成、原理和优点进行了介绍,重点分析了整流及逆变单元,研究了ACS800多传动控制系统在1.0×105t瓦楞纸机传动控制系统中的应用.     

800MW机组水燃比控制方案

介绍了某800MW直流炉机组协调控制系统水燃比控制方案，并对燃料校正模糊PID控制器及最小二乘煤质校正方法进行了详细分析．