交变间歇励磁电源的研制及在TIG焊接中的应用

发布时间：2018-05-20 01:15

本文选题：磁控焊接 + 励磁电源　；参考：《南昌航空大学》2017年硕士论文

【摘要】：磁控焊接技术是近年来逐渐完善起来的一种新型焊接技术,通过励磁电源产生的外加磁场可以改变焊接电弧、熔池的形态以及熔滴过渡等,能有效地细化焊缝晶粒,减少化学成分不均匀性,降低结晶裂纹和气孔的敏感性,从而提高焊接接头的力学性能,改善焊缝质量。施加不同的外加磁场,是磁控焊接技术的关键,因此,研制一种新型的外加交变间歇磁场发生电源,并将其应用于TIG焊接,为磁控焊接技术的研究提供一些理论依据,对磁控焊接技术的发展具有一定的理论意义与实际价值。本文研制了一种新型的能产生交变间歇方波的励磁电源,该电源采用键盘输入参数的方式调节交变频率及占空比,参数调节直观方便。电源由主电路、控制电路、放大驱动电路以及逆变电路组成,对电路的组成结构进行了设计,并对各电路的工作原理进行了详细的分析。主电路由变压器、整流器、稳压器等组成,将交流电降压整流为稳定的直流电。控制电路中,由单片机作为主控芯片产生数字交变间歇脉冲方波信号,并采用键盘输入参数的方式,调节电源的交变频率及占空比。控制电路的程序通过软件编程来实现,对软件编程的四个方面(主程序、键盘输入程序、交变间歇方波产生程序以及液晶显示输出程序)进行了设计。放大驱动电路以L298N驱动芯片为核心,将单片机产生的交变间歇方波信号进行功率放大。通过对比分析几种逆变电路的结构,选择了全桥式的逆变形式作为该电源的逆变电路。对电源研制过程中遇到的问题提出了解决的方法。结果表明:研制的电源能稳定地输出交变间歇方波,电源的频率、占空比、电压及电流幅值均可调节,电源的设计结构合理,性能基本满足磁控焊接的要求。利用该电源产生的交变间歇磁场作用于低碳钢TIG焊接过程,探索有外加交变间歇磁场及交变间歇磁场的交变频率对焊接电弧的形态以及焊缝熔宽、熔深的影响,并对磁场作用于焊接的机理进行了探讨。试验结果表明有外加交变间歇磁场作用TIG焊接过程时,焊缝熔宽明显增加,熔深明显减小,电弧上部收缩,下部扩张,形态变为钟罩形,且随着交变频率的增大,焊缝熔宽逐渐减小,熔深逐渐增大,电弧发生收缩的现象。
[Abstract]:Magnetic controlled welding (MAW) is a new welding technology which has been gradually improved in recent years. The welding arc, the shape of molten pool and the droplet transfer can be changed by the external magnetic field generated by the excitation power source, which can effectively refine the weld grain. The mechanical properties and weld quality of welded joints can be improved by reducing the chemical inhomogeneity and reducing the sensitivity of crystal cracks and pores. Applying different applied magnetic fields is the key of magnetically controlled welding technology. Therefore, a new type of applied alternating intermittent magnetic field generator is developed and applied to TIG welding, which provides some theoretical basis for the research of magnetically controlled welding technology. It has certain theoretical significance and practical value for the development of magnetic controlled welding technology. In this paper, a new type of excitation power supply which can produce alternating intermittent square waves is developed. The input parameters of the keyboard are used to adjust the alternating frequency and duty cycle, and the adjustment of parameters is intuitionistic and convenient. The power supply consists of main circuit, control circuit, amplifier drive circuit and inverter circuit. The structure of the circuit is designed, and the working principle of each circuit is analyzed in detail. The main circuit is composed of transformer, rectifier, regulator and so on. In the control circuit, the digital alternating intermittent pulse square wave signal is generated by the single chip microcomputer as the main control chip, and the frequency and duty cycle of the power supply are adjusted by keyboard input parameters. The program of control circuit is realized by software programming. Four aspects of software programming (main program, keyboard input program, alternating batch square wave generation program and LCD output program) are designed. L298N driving chip is the core of the amplifier drive circuit, which amplifies the alternating intermittent square wave signal generated by single chip microcomputer. By comparing and analyzing the structure of several inverter circuits, the full-bridge inverter is chosen as the inverter circuit of the power supply. The solutions to the problems encountered in the development of power supply are put forward. The results show that the power supply can output the alternating intermittent square wave stably, the frequency, duty cycle, voltage and current amplitude can be adjusted, the design structure of the power supply is reasonable, and the performance basically meets the requirements of magnetically controlled welding. The alternating intermittent magnetic field produced by this power supply is applied to the TIG welding process of low carbon steel. The effects of the alternating frequency of the applied intermittent magnetic field and alternating intermittent magnetic field on the shape of welding arc and the weld width and penetration are explored. The mechanism of magnetic field acting on welding is also discussed. The experimental results show that the weld width increases obviously, the penetration depth decreases obviously, the upper arc shrinks, the lower part expands, and the shape becomes bell-shaped with the increase of alternating frequency. The weld width decreases gradually, the penetration increases and the arc shrinks.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG444.74

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