不锈钢激光焊接头质量超声波检测研究
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摘要
激光焊接作为一种较精密的连接方法，具有功率密度高、速度快、焊接热影响区窄等优点，被越来越多的应用在汽车和轨道客车的薄板焊接中。为了满足车体的外观要求，薄板激光焊接一般采用搭接的方式，并且控制下层不锈钢板为半熔透状态。薄板搭接激光焊接过程容易受到很多因素的影响，如焊接冷却速度过快、工件装卡精度不够、焊接参数波动等都会在焊缝产生未焊透或气孔等缺陷。这些缺陷的存在将大大降低焊缝的强度和寿命，因此提高不锈钢薄板激光焊接质量以保证结构的安全是十分有必要的。
焊接接头的质量检测分破坏性检测和无损检测两大类。在实际生产中以破坏性检测为多，但它只能给予参考性的信息，因为实际工作的焊接接头仍然是未经过检测的。随着人们对焊接质量要求越来越高，对焊件进行大批量的无损检测，以确保焊件的安全可靠性，也显得越来越重要。超声波检测技术是工业无损检测技术中应用最广泛的技术之一，也是无损检测领域研究最为活跃的技术之一。但传统的超声波无损检测仪器就存在操作复杂、不直观、无记录和人为因素影响大等缺陷，无法满足现代工业对超声波无损检测可靠便携的要求。
为了满足汽车、航天等现代工业领域激光焊缝质量检测的要求，本文以不锈钢薄板搭接激光焊缝为研究对象，深入研究了焊缝质量与超声波无损检测特征信号的关系，运用信号分析与处理技术，建立了不锈钢薄板搭接激光焊缝的超声波无损检测系统。在硬件方面采用工业计算机为超声波无损检测的控制核心，运用全功能超声卡（超声波脉冲发射/接收和A/D模数转换集成设计在一块PCI总线主板上）、速度控制器和自动扫查器（微型直线电机平台和超声波探头组成）完成超声波信号的发射与采集，该硬件系统简单可靠，测量精度高，适合在工业生产环境中使用。基于Visual C++平台开发了不锈钢薄板搭接激光焊缝超声波无损检测软件系统，该软件系统具有回波数据采样、存储和焊缝质量信息预测等功能，实现了超声波检测的数字化、智能化、可视化及缺陷的定量和定性分析，同时该软件也实现了对焊缝质量信息的智能化管理，具有抗干扰能力强、检测分析速度快、可靠性高等优点。
针对不锈钢薄板搭接激光焊缝进行大量试验，确定影响超声波无损检测因素的工艺参数。介绍了本超声波检测系统“超声设置”、“扫描设置”主菜单的内容，从提高检测系统的灵敏度、可靠性出发，对C扫描的主要参数如采样频率、增益、检测步长等，做出合理的设置。
分析不锈钢薄板搭接激光焊缝不同区域的超声波A扫描信号的时域特征，总结出用A扫描信号测量激光焊缝宽度的原理，并且根据这一信息编写激光焊缝A扫描信号测量法软件。同时，分析不锈钢薄板搭接激光焊缝不同区域的超声波回波信号的频域幅度谱图特征，总结出振幅主频率的变化与探头是否靠近焊缝有着良好的对应关系。频谱中的高频成分随距离和晶粒尺寸的衰减比低频成分快的多，使回波的振幅主频率向低频移动，根据这一信息特征编写超声波FFT信息测量法软件。
最后，通过金相试验验证上述两种超声波无损检测测量方法的准确性和稳定性，统计这两种超声波无损检测方法的误差范围，并分析这两种超声波无损检测方法的优缺点。试验结果表明，对于A扫描信号测量法，当门槛值为40%时，测量结果的相对误差很小，但方差相对于超声波FFT信号测量法偏高，说明A扫描信号测量法测量的稳定性还有待提高；超声波FFT信息测量法得到的测量值和实测值吻合很好，相对误差正态分布曲线的均值为0.01417，方差为0.06986，数值都很小，说明在本试验条件下超声波FFT信号测量法的精度和稳定性都很高。
Laser welding as a precision connected method, have power density, high speed,narrow welding heat affected zone etc, It is more and more used in lapped sheet ofcars and railway vehicle. But thin lapped sheet laser welding is a complicated physicaland chemical process, the welding process is easily affected by many factors, such aswelding, the fast cooling speed and improper protection. Not complete fusion or gascavity will be produced in the weld. The existence of these defects will greatly reducethe strength and lifetime of weld. Serious accident may occur. In order to improve thestability and reliability of the stainless steel laser welding, it is necessary to inspect.Inthis way we can ensure the safety of the structure.
There are two kinds of method to inspect laser welding joint quality, destructivetesting and nondestructive testing. In the actual production, destructive testing canonly provide reference information, because the practical work of the welding joint isstill without detection. As welding quality requirements is more and more needed, onehundred percent nondestructive testing of weldment to ensure the safety andreliability is more and more important. Ultrasonic testing technology is most widelyapplied in industry of nondestructive testing technology. It is also the most activetechnology of nondestructive testing field study. But the traditional ultrasonicnondestructive testing instrument operates complexly, it is not intuitive, no recordsand large influence defects of human factors. These can not satisfy the modernindustrial of ultrasonic nondestructive testing reliable portable requirements.
In order to adapt laser welding quality detection requirements of modernindustrial fields such as auto and aerospace, the subject researches the stainless steellapped sheet laser welding, studies relationship between weld quality and ultrasonicnondestructive testing characteristic signal. Signal analysis and processing technologyis used to set up the stainless steel lapped sheet laser welding ultrasonicnondestructive testing system. The industrial computer is the core control, it apply the full function ultrasound card (ultrasonic pulse launch/receiving and A/D conversionare integrated on one PCI bus board).Speed controller and automatic scanning device(miniature linear motor platform and ultrasonic probe) accomplishes launch andreceiving of ultrasonic signal. The hardware system is simple, reliable, high accuracyand is suitable for application in industrial production environment. We develop thestainless steel lapped sheet laser welding ultrasonic nondestructive testing softwaresystem based on Visual C++platform. The software system can collect the echo data,store information and predict welding quality information. It realizes digitalization,intelligent, visualization and quantitative and qualitative analysis of defect in theultrasonic testing. At the same time the software also completes intelligentmanagement of weld quality information, it has the strong anti-interference, highspeed testing analysis and reliability etc.
We ascertain parameters affecting the ultrasonic nondestructive inspection by alot of the stainless steel laser welding testing. The paper Introduces the ultrasonictesting system" ultrasonic settings" and "scanning settings", In order to improve thesensitivity and reliability of testing system, reasonable settings of C scan mainparameters will be made such as sampling frequency, gain, detection step length etc.
In the time domain, we analyze the characteristics of A signal on the stainlesssteel laser welding in different areas. We sum up with principle about measuring laserweld width by A scanning signals. According to the information, we can writesoftware with measurement method of A scanning signal laser welding. Meanwhile, inthe frequency domain we analyze the ultrasonic echo signal amplitude spectrumcharacteristics on the stainless steel lapped sheet laser welding in different area. Wesum up with whether the main frequency amplitude change and the distance betweenprobe and weld have corresponding relation. The high frequency component spectrumattenuates faster than low frequency components when distance and grain size havechanged. The main amplitude frequency of the echo move to the low frequency.According to this information features, we can write software with ultrasonic FFT measurement method.
Finally, we analyze the accuracy and stability of above two kinds of ultrasonicnondestructive testing method by metallographic experiment. Statistics suggest therange of error about this two kinds of ultrasonic nondestructive testing method. Thepaper analyzes the advantages and disadvantages of two methods. The experimentresults show that A scanning signal measurement method is not stable enough. Whenthe threshold value of40%, the relative error of measurement results is very small, butthe variance is a little higher compared with ultrasonic FFT signal measuring method.Ultrasonic FFT information measuring method is accurate and stable enough atexperimental condition.The measured value agrees with the actual measured valuewell, the average value of the relative error normal distribution curve is0.01417, thevariance is0.06986, both number are small.
焊接接头的质量检测分破坏性检测和无损检测两大类。在实际生产中以破坏性检测为多，但它只能给予参考性的信息，因为实际工作的焊接接头仍然是未经过检测的。随着人们对焊接质量要求越来越高，对焊件进行大批量的无损检测，以确保焊件的安全可靠性，也显得越来越重要。超声波检测技术是工业无损检测技术中应用最广泛的技术之一，也是无损检测领域研究最为活跃的技术之一。但传统的超声波无损检测仪器就存在操作复杂、不直观、无记录和人为因素影响大等缺陷，无法满足现代工业对超声波无损检测可靠便携的要求。
为了满足汽车、航天等现代工业领域激光焊缝质量检测的要求，本文以不锈钢薄板搭接激光焊缝为研究对象，深入研究了焊缝质量与超声波无损检测特征信号的关系，运用信号分析与处理技术，建立了不锈钢薄板搭接激光焊缝的超声波无损检测系统。在硬件方面采用工业计算机为超声波无损检测的控制核心，运用全功能超声卡（超声波脉冲发射/接收和A/D模数转换集成设计在一块PCI总线主板上）、速度控制器和自动扫查器（微型直线电机平台和超声波探头组成）完成超声波信号的发射与采集，该硬件系统简单可靠，测量精度高，适合在工业生产环境中使用。基于Visual C++平台开发了不锈钢薄板搭接激光焊缝超声波无损检测软件系统，该软件系统具有回波数据采样、存储和焊缝质量信息预测等功能，实现了超声波检测的数字化、智能化、可视化及缺陷的定量和定性分析，同时该软件也实现了对焊缝质量信息的智能化管理，具有抗干扰能力强、检测分析速度快、可靠性高等优点。
针对不锈钢薄板搭接激光焊缝进行大量试验，确定影响超声波无损检测因素的工艺参数。介绍了本超声波检测系统“超声设置”、“扫描设置”主菜单的内容，从提高检测系统的灵敏度、可靠性出发，对C扫描的主要参数如采样频率、增益、检测步长等，做出合理的设置。
分析不锈钢薄板搭接激光焊缝不同区域的超声波A扫描信号的时域特征，总结出用A扫描信号测量激光焊缝宽度的原理，并且根据这一信息编写激光焊缝A扫描信号测量法软件。同时，分析不锈钢薄板搭接激光焊缝不同区域的超声波回波信号的频域幅度谱图特征，总结出振幅主频率的变化与探头是否靠近焊缝有着良好的对应关系。频谱中的高频成分随距离和晶粒尺寸的衰减比低频成分快的多，使回波的振幅主频率向低频移动，根据这一信息特征编写超声波FFT信息测量法软件。
最后，通过金相试验验证上述两种超声波无损检测测量方法的准确性和稳定性，统计这两种超声波无损检测方法的误差范围，并分析这两种超声波无损检测方法的优缺点。试验结果表明，对于A扫描信号测量法，当门槛值为40%时，测量结果的相对误差很小，但方差相对于超声波FFT信号测量法偏高，说明A扫描信号测量法测量的稳定性还有待提高；超声波FFT信息测量法得到的测量值和实测值吻合很好，相对误差正态分布曲线的均值为0.01417，方差为0.06986，数值都很小，说明在本试验条件下超声波FFT信号测量法的精度和稳定性都很高。
Laser welding as a precision connected method, have power density, high speed,narrow welding heat affected zone etc, It is more and more used in lapped sheet ofcars and railway vehicle. But thin lapped sheet laser welding is a complicated physicaland chemical process, the welding process is easily affected by many factors, such aswelding, the fast cooling speed and improper protection. Not complete fusion or gascavity will be produced in the weld. The existence of these defects will greatly reducethe strength and lifetime of weld. Serious accident may occur. In order to improve thestability and reliability of the stainless steel laser welding, it is necessary to inspect.Inthis way we can ensure the safety of the structure.
There are two kinds of method to inspect laser welding joint quality, destructivetesting and nondestructive testing. In the actual production, destructive testing canonly provide reference information, because the practical work of the welding joint isstill without detection. As welding quality requirements is more and more needed, onehundred percent nondestructive testing of weldment to ensure the safety andreliability is more and more important. Ultrasonic testing technology is most widelyapplied in industry of nondestructive testing technology. It is also the most activetechnology of nondestructive testing field study. But the traditional ultrasonicnondestructive testing instrument operates complexly, it is not intuitive, no recordsand large influence defects of human factors. These can not satisfy the modernindustrial of ultrasonic nondestructive testing reliable portable requirements.
In order to adapt laser welding quality detection requirements of modernindustrial fields such as auto and aerospace, the subject researches the stainless steellapped sheet laser welding, studies relationship between weld quality and ultrasonicnondestructive testing characteristic signal. Signal analysis and processing technologyis used to set up the stainless steel lapped sheet laser welding ultrasonicnondestructive testing system. The industrial computer is the core control, it apply the full function ultrasound card (ultrasonic pulse launch/receiving and A/D conversionare integrated on one PCI bus board).Speed controller and automatic scanning device(miniature linear motor platform and ultrasonic probe) accomplishes launch andreceiving of ultrasonic signal. The hardware system is simple, reliable, high accuracyand is suitable for application in industrial production environment. We develop thestainless steel lapped sheet laser welding ultrasonic nondestructive testing softwaresystem based on Visual C++platform. The software system can collect the echo data,store information and predict welding quality information. It realizes digitalization,intelligent, visualization and quantitative and qualitative analysis of defect in theultrasonic testing. At the same time the software also completes intelligentmanagement of weld quality information, it has the strong anti-interference, highspeed testing analysis and reliability etc.
We ascertain parameters affecting the ultrasonic nondestructive inspection by alot of the stainless steel laser welding testing. The paper Introduces the ultrasonictesting system" ultrasonic settings" and "scanning settings", In order to improve thesensitivity and reliability of testing system, reasonable settings of C scan mainparameters will be made such as sampling frequency, gain, detection step length etc.
In the time domain, we analyze the characteristics of A signal on the stainlesssteel laser welding in different areas. We sum up with principle about measuring laserweld width by A scanning signals. According to the information, we can writesoftware with measurement method of A scanning signal laser welding. Meanwhile, inthe frequency domain we analyze the ultrasonic echo signal amplitude spectrumcharacteristics on the stainless steel lapped sheet laser welding in different area. Wesum up with whether the main frequency amplitude change and the distance betweenprobe and weld have corresponding relation. The high frequency component spectrumattenuates faster than low frequency components when distance and grain size havechanged. The main amplitude frequency of the echo move to the low frequency.According to this information features, we can write software with ultrasonic FFT measurement method.
Finally, we analyze the accuracy and stability of above two kinds of ultrasonicnondestructive testing method by metallographic experiment. Statistics suggest therange of error about this two kinds of ultrasonic nondestructive testing method. Thepaper analyzes the advantages and disadvantages of two methods. The experimentresults show that A scanning signal measurement method is not stable enough. Whenthe threshold value of40%, the relative error of measurement results is very small, butthe variance is a little higher compared with ultrasonic FFT signal measuring method.Ultrasonic FFT information measuring method is accurate and stable enough atexperimental condition.The measured value agrees with the actual measured valuewell, the average value of the relative error normal distribution curve is0.01417, thevariance is0.06986, both number are small.
引文
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