奥氏体不锈钢DP-TIG焊接工艺及接头性能研究

通过焊接工艺试验研究了各工艺因素对奥氏体体不锈钢DP-TIG焊缝成形的影响,并按照压水堆核电厂机械设备焊接工艺评定的要求对成形良好的焊接接头进行了金相分析和力学性能分析.试验结果表明焊接电流、焊接电压、焊接速度是影响DP-TIG焊缝成形的关键因素,母材厚度、种类及装配质量也影响DP-TIG焊缝成形,焊接接头的各项性能均...     

薄壁碳钢A—TIG单面焊双面成形试验研究

A—TIG焊接方法能显著增加焊接熔深。通过对薄壁碳钢进行堆焊试验，研究活性剂涂层、焊接电流、焊接速度对薄壁碳钢A—TIG焊焊缝成形的影响。选取优化后的焊接参数进行A—TIG对接焊接单面焊双面成形的工艺试验，从而实现了单面焊双面成形。     

基于PLC控制的恒流充电电流发生器设计

设计了一种基于PLC控制的恒流充电冲击电流发生器。该发生器是由一台三菱PLC作为控制器,通过控制可控硅导通角,调节输出电压,输出电压经过整流对脉冲电容器进行充电,实现恒流控制。最后通过调波电路进行参数调整,触发放电球,形成放电回路。试验结果证明,该方案达到了恒流充电的效果,并实现了8/20 us冲击电流波形。     

脉冲埋弧焊技术在膜式水冷壁管屏拼接中的试验及应用

使用埋弧焊(SAW)进行锅炉水冷壁管屏生产时,如何在保证焊接质量的前提下,提高焊接速度是需要解决的技术难点.上海锅炉厂有限公司采用脉冲埋弧焊[1～2]技术,对水冷壁管屏拼接工艺进行了焊接试验和产品试生产.实践证明,脉冲埋弧焊相比常规的直流埋弧焊能提高焊接速度13%～25%,改善水冷壁管屏生产中因速度提高而产生的咬边等成形不良问题,使焊缝质量更加优良,有效地提高了焊接生产率.     

CO2气体保护焊在吊杆上的运用

通过采用CO_2气体保护焊焊接吊杆工艺性试验,对试件进行熔深、硬度、力学性能实验。试验结果表明,控制好焊接参数能保证CO_2气体保护焊的焊缝质量,能满足吊杆产品的质量要求。CO_2气体保护焊对比焊条电弧焊焊缝成形美观、焊接效率大幅度提升。     

BFe30-1-1凝汽器管子与管板焊接方法试验研究

介绍了BFe30-1-1凝汽器管子与管板一种较实用焊接方法,自熔不填丝全位置脉冲自动钨极氩弧焊焊接方法,以及以白铜BFe30-1-1为管子与管板的凝汽器材料焊接特性.通过对BFe30-1-1管子与管板,在纯氩、氢一氩混合两种不同气体保护条件下的焊接工艺试验,以及在不同气体保护下的焊接工艺参数的选择与优化,结果表明,采用自熔不填丝全位置脉冲氩弧焊焊接方法,在氢-氩混合气体保护条件下,BFe30-1-1凝汽器管子与管板焊接,焊缝成型好,质量高;以合理工艺参数匹配焊接的试验件,经各项检验均已合格,完全达到设计要求.     

锅炉集箱管座内孔脉冲钨极氩弧焊封底

本文提出的锅炉集箱管座内孔脉冲钨极氩弧焊封底,可以获得“全焊透”的管座角焊缝,能在根本上避免泄漏事故,提高角焊缝的承压强度,也是解决管座角焊缝内外全自动焊的基础。这一工艺方法的采用,具有很大的技术经济意义,以年产150万千瓦电站锅炉的工厂计算,仅在大幅度降低返修和免除泵水所带来的收益即可达数十万元。至于为电厂提高运行可靠性,减少事故停炉带来的利益更以千万元计。所介绍的焊机机头和电气控制线路,能达到集箱管座角焊缝焊接的程序控制要求。本文讨论了脉冲氩弧焊焊接规范主要参数的选择,引用了等值电流的概念。收弧裂缝是一种较为独特的热裂缝,近似于弧坑裂缝而又不同于通常阐述的弧坑裂缝。收弧裂缝主要发生在脉冲氩弧焊双面成形焊缝的背面,且正对主脉冲所形成的弧坑。提出了解决收弧裂缝的主要工艺措施是选用一种脉冲衰减的焊接规范。本文还列举了集箱管座内孔脉冲氩弧封底焊在电站锅炉生产中的应用实例。     

细丝小马鞍型埋弧焊试验及其在汽包管座角焊缝上的应用

为了实现锅炉汽包骑坐式管座角焊缝的机械化、自动化,达到高效、高质量焊接的目的,从设备选型、焊材匹配试验、接头性能试验、工艺参数的确定等方面进行了系统的工艺试验工作。试样结果表明：选用合理的工艺参数,采用细丝马鞍形埋弧焊工艺方法焊接汽包骑座式管座角焊缝,与焊条电弧焊对比,可以较大幅度提高焊接效率,同时更利于保证焊接质量。     

伸出15mm SA-213 T22换热管与堆焊Inconel 600管板焊接工艺研究

换热管材质SA-213 T22,管板基材为SA-336 F22Cl3,管板堆焊层为Inconel 600,管端伸出长度15mm,管孔开45°坡口,坡口深2.5mm,对于此结构形式的管子管板焊相关研究较少,本文针对此种结构形式管子-管板焊进行焊接工艺研究。分析主要工艺参数对焊接质量的影响,进行渗透检查、宏观检查,焊脚尺寸测量。最终得出最优焊接工艺参数,钨极伸出长度约17mm、保护气流量25-30L/min时可同时解决焊接可达性和熔池保护效果的矛盾。首层焊缝采用自熔焊可保证根部焊透,其余焊层采用填丝焊接,焊缝成形美观,焊接质量稳定。角焊缝焊脚尺寸满足相关标准要求。     

海水主冷凝器焊接材料及焊接工艺试验研究

对841焊条、Ni102焊条和Cu307焊条进行研制,通过材料焊接性试验,焊缝金属化学成分的调整和力学性能试验,焊接工艺试验及焊接工艺评定等工作,最后确定焊接工艺规范和编制工艺规程指导生产。     

Plasma arc welding of pipelines: A study to optimise welding conditions for horizontal fixed joints of mild steel pipes

A plasma arc process was applied to the welding of mild steel pipes (thickness: 6·4 mm, outside diameter: 406·4 mm) and the effect of different welding parameters on the shape of welds and consistency of defects was studied in the flat, vertical and overhead positions.In conventional plasma arc welding conditions, full penetration and continuous bead formation were obtained in a range of conditions which tended towards lower plasma gas flow rates and higher travelling speeds as the welding current was increased. In the overhead position, the penetration bead presented deep continuous concaves.In the vertical-up position, it was not possible to obtain a range of welding conditions assuring full penetration and continuous bead formation.The experiment relating to the effect of the pulsating welding current on the shape and defects of welds disclosed that the use of pulse frequencies lower than 4 Hz makes the penetration bead less uniform than the use of higher pulse frequencies. It was also found that the use of high pulse frequencies results in a remarkable effect in the vertical-up position.Welding using argon gas back shielding made the penetration bead more uniform in height and width. By decreasing the atmospheric pressure inside the pipe, concaves in the penetration bead could be reduced, particularly in the overhead position.From the results described above, it is considered that pulsating welding current and the backing method are effective in obtaining a good bead over the entire circumference of mild steel by plasma keyhole welding.The experiment also revealed that when plasma arc welding is applied, mild steel pipes can be welded at four times the productivity that can be expected of the conventional GMA welding.Therefore plasma arc welding equipment and appropriate jigs will be made shortly for practical application.     

Genetic algorithm for optimisation of A-TIG welding process for modified 9Cr–1Mo steel

Abstract

It is essential to set up the activated tungsten inert gas (A-TIG) welding process parameters to produce the desired weld bead geometry and heat affected zone (HAZ) width in modified 9Cr–1Mo steel weld joints. Therefore, it becomes necessary to develop a tool for optimisation of A-TIG welding process. Genetic algorithm (GA) based model has been developed to determine the optimum process parameters. In this methodology, first independent ANN models correlating depth of penetration, weld bead width and HAZ width with current, voltage and torch speed respectively were developed. Then, GA code was developed in which the objective function was evaluated using the ANN models. There was good agreement between the target and actual values of bead geometry and HAZ width obtained using the GA optimised process parameters. Thus, a methodology using GA has been developed for optimising the A-TIG process parameters for modified 9Cr–1Mo steel.     

Optimal parameters for pulsed gas tungsten arc welding in partially and fully penetrated weld pools

In the present paper, a numerical model of spot pulsed current GTA welding for partially and fully penetrated weld pools is presented. Heat transfer and fluid flow in the weld pool driven by the combination of electromagnetic force, buoyancy force, surface tension gradient and latent heat are included in our model. A new formulation of the electromagnetic problem is introduced to take into account eddy current in the weld pool. The shape of the free deformable surface under the action of pulsed arc force is also handled after the magneto-hydrodynamic calculation.The numerical model was applied to 304 stainless steel welding. We compare the influence of various pulsed welding parameters such as pulse frequency and current ratio on the weld quality. Experimental study is conducted to compare our numerical prediction with welding macrographies. It shows a good agreement of the model.     

光伏模拟器用死区消除PWM整流器运行方式

针对光伏模拟器用单相脉宽调制（PWM）整流器提出电压平方外环电流内环的控制策略,同时揭示直流侧存在2倍基波频率的纹波电压以及此纹波电压对网侧电流的影响。PWM整流器采用的基于H桥死区消除SPWM,在网侧电流非过零区域,各桥臂上下两开关管中,必定存在其中一个开关管驱动信号为低电平,而在电流过零处推导出存在的天然死区时间。由微控制器（MCU）与现场可编程门阵列（FPGA）相结合的控制系统可实现提出的运行方式。实验结果验证了理论推导的正确性以及提出运行方式的有效性。     

Effectiveness of active noise and vibration cancellation for switched reluctance machines operating under alternative control strategies

The effectiveness of active vibration cancellation by inducing antiphase vibration of the stator to reduce the acoustic noise emitted from a switched reluctance machine is evaluated under typical operating modes, viz., single pulse excitation, pulsewidth modulation (PWM) voltage control, and PWM current control. Measurements in both the frequency and time domains are complemented by sound pressure level measurements. It is shown that active vibration cancellation is most effective in reducing a single mode of vibration when a switched reluctance (SR) machine is operated under single-pulse excitation, and becomes less effective when more than one dominant vibration mode exists within the audible frequency range. In general, it also works relatively well when the machine is operated under fixed frequency PWM voltage control, although less effectively than for single pulse control. Further, it is shown that the technique is ineffective when the machine is operated under PWM current control since the duration of the zero voltage period varies significantly from the optimal value due to the random nature of the PWM.     

移动式比相法配电网接地故障定位同步采集的实现

根据移动式比相法的定位原理,提出应用北斗导航系统的秒脉冲(1 pulse/s)及UTC来实现零序电压电流的异地同步采集。1 pulse/s及UTC可为采集工作分别提供同步触发信号及时间标定。为验证1 pulse/s信号的同步性,设计了一种基于ARM(Advanced RISC Machines)技术的软硬件平台,实现了不同北斗授时模块1 pulse/s接口精度的测试。选用2.4 GHz射频收发芯片nRF2401来实现移动式零序电流互感器高压端和低压端间数据的无线传输,提出一种预备-触发模式的程序设计方案,以实现三相电流的同步采样。实验室试验验证了所述方法的可行性。     

变阻值Crowbar电路及其在提高双馈式风电机组低电压穿越能力中的应用

双馈风力发电机的低电压穿越能力较差,Crowbar技术是提高双馈风力发电机低电压穿越能力的有效手段。分析了DFIG机端短路时Crowbar阻值对转子电流和暂态过程的影响,指出传统Crowbar电路采用固定的阻值,无法兼顾低电压穿越过程中各阶段对该阻值的不同要求。为此提出了一种变阻值Crowbar的电路,采用这种电路只要控制脉宽就可以改变Crowbar电路的等效电阻,在电网发生地电压故障后,可以根据保护过程不同阶段的特点及时调整Crowbar电路电阻,提高双馈风力发电机的低电压穿越能力。为了验证调整效果对新设计的Crowbar电路的调整效果进行了仿真。仿真结果表明,变阻值Crowbar能够通过控制脉宽实现对Crowbar等效电阻的有效控制。     

Discriminating between the effect of pulse width and duty cycle on the hydrogen generation performance of 3-D electrodes during pulsed water electrolysis

The present study investigates the effect of applying voltage and current pulses during alkaline water electrolysis using 3-D Ni-based electrodes. The pulses had a square shape and alternated hydrogen production and resting time. When voltage pulses were applied, it was observed that the current at on-time was systematically higher than the current during DC electrolysis. However, during off-time, a change in polarization was observed, which decreased the overall voltage pulse performance. For pulses with a 50% duty cycle and a pulse width of 1 ms, the current response was mainly capacitive and almost no hydrogen production occurred. Current pulses on the other hand were proven to be much more promising in improving the energetic process efficiency. In that case, a pulse period of 2 ms resulted in an overpotential reduction of 17% for a 50% duty cycle. This reduction further increased to 28% when decreasing the duty cycle to 20%. Finally, in all cases where faradaic processes were dominant, applying a forced electrolyte flow was shown to be beneficial.     

在锅炉水冷壁焊接生产中MPM焊机的应用

介绍了引进的12头MPM焊机。该焊机采用脉MAG焊工艺,12把焊枪上下同时对管屏进行焊接,管屏一次焊成。对该机的设备、焊枪及焊接程序、焊接电源特点、焊接参数调整及管屏焊接工艺措施作了介绍。