X80管线钢焊接粗晶区的模拟研究

本文采用物理模拟技术以及现代工程测试技术和分析技术对X80管线钢焊接粗晶区进行了模拟研究,通过对比法对模拟粗晶区和焊管粗晶区的组织结构特征进行对比和分析,得出模拟组织能较好地反映实际焊接热影响区组织的真实情况。发现焊接热影响区的粗晶区在低焊接热输入条件下可获得较好的韧性值,但在高焊接热输入条件下韧性会严重恶化和韧脆转变温度的升高。在实际焊接生产时外焊预热对内焊再热粗晶区的韧性有一定的改善作用。     

氨合成塔用2.25Cr-1Mo钢的焊接及热处理工艺研究

针对某公司的氨合成塔产品,通过采用厚度为50 mm的SA336 F22 CL3锻件进行了焊接工艺评定.采用埋弧自动焊焊接,通过选择合适的焊材、合理的焊接工艺参数及焊后热处理参数,对焊接接头的拉伸强度、弯曲、冲击等力学性能进行了测试,并对其焊缝及热影响区进行了回火脆化倾向评定试验.测试结果表明,焊接接头的各项力学能和回火...     

分析不同焊接电流下Q235B钢焊接接头金相组织

对12mm厚Q235B试板进行手工电弧焊试验研究,采用3种不同焊接电流参数对3组试板进行焊接,以研究不同焊接电流下焊接接头的金相组织。3组试板均采用双面焊,分别对正面填充焊和盖面层焊采用155A、165A、175A三种电流,焊接完成后首先对焊接接头进行超声、渗透检测,最后采用金相检验方法对其焊接接头组织进行分析,金相测试结果表明:焊接电流175A接头热影响区宽度为4mm,大于155A和165A热影响区宽度(3mm)。随着焊接电流增大,焊缝区上的柱状晶变大、热影响区粗晶区上的铁素体晶粒变大,晶粒越粗大,焊缝质量越不好。综合实验研究结果表明:对于Q235B钢手工电弧焊,155A-165A焊接电流比较合适。     

在役07MnCrMoVR球罐板材组焊再热裂纹敏感性研究

通过热模拟HAZ粗晶区应力释放试验,评价了07MnCrMoVR高强钢400m3球罐焊接时的再热裂纹敏感性,并对该球罐重新组装时的最佳焊后热处理温度进行研究,确定该材料的后热处理再热裂纹敏感区域,保证了现场施工的顺利进行。     

焊后热处理对耐磨堆焊焊接接头组织和硬度的影响

对于耐磨堆焊焊材来说,焊后热处理对焊接接头组织和性能有重要影响。本文采用D256耐磨堆焊焊条对Q235A钢进行手工电弧堆焊,并进行焊后热处理,研究了焊后热处理对耐磨堆焊焊接接头金相组织及硬度的影响。实验结果表明,随着焊接电流的增加,焊缝区和过热区的晶粒将发生一定程度的粗化;焊后热处理使焊接接头组织发生变化并使得接头硬度显著提高。     

换热器管-管板的焊接接头泄漏原因及改进措施

1　管 -管板焊接接头的结构换热器管 -管板焊接接头结构如图 1所示。L1 为伸出长度 ,L2 为焊脚高度图 1　管 -管板焊接接头结构2　管 -管板焊接接头泄漏原因从换热器管 -管板焊接接头的泄漏情况及强度焊接的结构特点来分析 ,焊接接头的泄漏原因主要是应力腐蚀和缝隙腐蚀。2 .1　应力腐蚀换热器管与管板焊接过程中 ,在焊缝两侧形成的热影响区是焊接接头的薄弱环节 ,不锈钢的热影响区组织较细 ,但高温时会产生晶间腐蚀析出碳化铬 ,造成硬度及脆性增大 ,韧性降低 ,且出现应力集中 ,易发生塑性变形 ;而普通碳钢的热影响区宽 ,焊接时由于高温导…     

对几种压力容器热处理的考虑

奥氏体不锈钢制压力容器是否需要焊后热处理 焊后热处理是利用金属材料在高温下屈服极限的降低,使应力高的地方产生塑性流变,从而达到消除焊接残余应力的目的。同时可以改善焊接接头及热影响区的塑性和韧性,提高抗应力腐蚀的能力。这种消除应力的方法在具有体心立方晶体结构的碳素钢、低合金钢制压力容器中被广泛采用。     

CO2气田用X65管线钢焊缝的电化学腐蚀行为研究

X65管线钢具有良好机械性能及焊接性,但在CO2气田使用时,常常在焊缝和热影响区发生电化学腐蚀,严重情况下可能造成焊接失效。本文通过对X65管线钢焊缝的电化学腐蚀行为研究,筛选并推荐了合适的焊接工艺。     

AZ31铸轧镁合金脉冲TIG焊接工艺研究

粗晶是造成铸轧镁合金AZ31焊接接头发生严重弱化的主要原因,合理的焊接工艺方案是解决焊接性问题的关键。通过研究交流TIG和脉冲TIG焊接工艺对铸轧镁合金拉伸性能的影响。结果表明:脉冲焊接熔池两侧区域的冷却速度快,晶粒更均匀,晶粒度更小;通过拉伸试验,脉冲TIG焊焊接接头的抗拉强度、屈服强度和延伸率均高于交流TIG焊,具有更好的焊接性。     

Q345R双面埋弧焊接头组织分析

采用双面埋弧焊方法焊接了20mm厚的Q345R钢,分析了接头焊缝区及热影响区的组织并进行了显微硬度测试。组织分析表明,焊接接头焊缝区为柱状晶,组织为先共析铁素体、少量针状铁素体和珠光体;热影响区靠近焊缝处为等轴晶,组织为先共析铁素体+少量珠光体,离焊缝较远处为铁素体与珠光体相间的带状组织,珠光体有一定程度的减少。显微硬度分布表明,接头热影响区硬度最高,焊缝硬度高于母材硬度。     

Numerical analysis on optimal zone lengths for each pass in multipass zone-refining processes

The effect of zone length on the separation efficiency in multipass zone-refining processes has been investigated theoretically. The optimal zone length for maximum separation efficiency in each zone pass has been determined. As a well known fact (Davies, 1959), the best performance in the first pass is achieved by normal-freezing operation. In multipass operations, the optimal zone lengths in each pass and their corresponding maximum fraction of solute removal were obtained with distribution coefficients k and number of passes n as parameters. The results showed the optimal zone lengths for all passes increase with distribution coefficient, but decrease with pass number.     

乙烯裂解炉对流段 P91炉管焊接工艺评定及其应用

对于P91钢,焊前预热是必要的,通过试验研究了焊接线能量对P91钢焊接接头冲击韧性的影响,焊接线能量控制在12～15kJ／cm以内,控制层问温度,能获得良好的焊接接头。根据焊接接头的力学性能检验,规定回火参数[P]等于21是合理的。并依此制定工艺,成功地完成了该钢种在三台乙烯裂解炉中的焊接应用。     

双机头双工位CO2气体保护全自动焊装置研制与应用

利用现有的焊接装备,进行了控制系统、摆动系统的设计,实现筒体两道外环缝的同时打底、填充、盖面,极大的提高了焊接效率,降低了劳动强度,并在生产实践中成功应用。     

组焊圆柱壳在轴向载荷和局部热载荷共同作用下屈曲数值研究

对大型直立设备安装过程中的现场焊接热处理过程中在轴向载荷和局部热载荷共同作用下的屈曲问题进行数值研究。研究结果表明,在焊后热处理过程中加热部位的边缘附近区域存在很大的温度梯度,导致该部位有很大的热应力。在热处理过程中焊缝部位的热应力很小,与加热部位边缘附近区域相比几乎可以忽略不计。组焊圆柱壳在轴向载荷和局部热载荷共同作用下屈曲最先发生在加热部位的边缘附近区域;热处理过程中加热部位边缘存在的局部热应力是导致组焊圆柱壳发生屈曲的关键因素。最后分析了热处理过程中几个关键参数对组焊圆柱壳,临界屈曲载荷的影响。     

Inter-tablet coating variability: Residence times in a horizontal pan coater

This paper investigates inter-tablet coating variability, specifically, tablet residence times within the spray zone. Discrete element method computer simulations, experiments, and analytical investigations are performed to measure the residence time per pass, the circulation time, and appearance frequency of spherical shaped tablets for a range of pan speeds and tablet loads. In addition, the fractional residence time, defined as the ratio of time spent by a tablet in the spray zone to the total coating time, is measured. The average fractional residence time (averaged over all the tablets in the bed) is found to be equal to the ratio of the time-averaged number of tablets exposed to the spray to the total number of tablets in the pan, a result that is consistent with analyses. The average fractional residence time is observed to be independent of pan speed and total coating time. Furthermore, the fractional residence time is shown to be related to the residence time per pass and circulation time per pass. Appearance frequency is defined as the number of appearances a tablet makes in the spray zone per pan rotation. Simulations and analyses show that appearance frequency decreases with increasing pan speed. Circulation time per pass for a tablet is defined as the average time between successive appearances in the spray zone and residence time per pass is defined as the average time spent in the spray zone per pass. These various measures are all related, but from the standpoint of developing an analytical model for coating variability, fractional residence time is a more useful and intuitive parameter as it determines the fraction of total run time that a tablet spends in the spray. This paper concentrates on determining average fractional residence times and residence time per pass, while the inter-tablet variability is more closely related to the standard deviation of the fractional residence time.     

压力容器筒体与平封头多级焊缝残余应力数值模拟

采用有限元软件ANSYS中生死单元技术对压力容器筒体与平封头单面焊焊接过程进行数值模拟,得出焊缝焊接残余应力、温度场及位移场的分布情况。经过分析可以得出：在焊缝区及熔合区温度极高;远离焊缝,温度峰值急剧下降。在熔舍区焊接残余应力达最大值;焊根处残余应力较小;在热影响区,沿焊缝方向多为拉应力,垂直焊缝方向多为压应力。     

合成氨装置低压蒸汽发生器的设计

介绍合成氨装置低压蒸汽发生器的设备结构、选材、结构设计及制造检验等设计思路和方法,分析探讨管程堆焊结构、焊接方式及焊环式密封结构的设计,为合成氨装置中高温高压容器设计总结出一套可行的方法。     

Applications of pressure balance in large scale distillation tower (Ⅰ)A new approach to estimating gas distributions on large scale valve trays

针对目前缺乏有效的大型塔板气速分布测试方法的现状,利用塔板压降的加和模型和塔板压力平衡,推导出沿塔板液流方向上不同区域的局部气速模型。在6400 mm×800 mm大型双溢流、16分区空气/水冷模试验塔上对所推导出的公式进行验证。结果表明,该模型依据塔板压降和持液分布数据能够对塔板上的气相分布进行很好的表征和量化。     

塔板压力平衡的应用(Ⅰ)一种推算塔板气相分布的新方法

针对目前缺乏有效的大型塔板气速分布测试方法的现状,利用塔板压降的加和模型和塔板压力平衡,推导出沿塔板液流方向上不同区域的局部气速模型。在6400 mm×800 mm大型双溢流、16分区空气/水冷模试验塔上对所推导出的公式进行验证。结果表明,该模型依据塔板压降和持液分布数据能够对塔板上的气相分布进行很好的表征和量化。     

TRANSFER PLASMAS DESTROY PCB FLUIDS

High voltage, ac transfer arcs were used as a reaction zone to destroy polychlorinated biphenyls dissolved in transformer fluid. The extremely high temperature of the arc is of sufficient magnitude that it destroys both the PCB's and the oil in which the PCB's are dissolved.

Although fast pyrolysis is the major destructive mechanism, several other features of the process are unique. For example, the transfer arc discharge is submerged. The arc is created beneath the surface of the transformer oil at a water interface. Furthermore, the water phase is part of the electrical circuit; but it also participates in the reaction chemistry of the plasma arc. Water vapor created by the discharge reacts with the carbon and acetylene formed by pyrolysis to produce hydrogen and carbon monoxide. This retards carbon buildup within the system.

The presence of the water phase also provides a convenient adsorption medium for acid gases (HC1) which are formed by pyrolysis of the PCB's, These gases are infinitely more soluble in the water phase than they are in the transformer oil through which they would have to pass to escape the submerged reaction zone. As a result, this new technology provides a convenient small-scale destruction for oils contaminated with PCB