本文件规定了飞行时间衍射（TOFD）技术在最小厚度为6mm的金属材料熔焊接头半自动或全自动超声波检测中的应用。 它适用于板材、管道和容器中几何形状简单的全熔透焊接接头，其中焊缝和母材均为低合金钢。在规定和适当的情况下，TOFD也可用于其他类型的超声波衰减低的材料（尤其是由于散射引起的材料）。 如果本文件中规定了与材料相关的超声波参数，则这些参数基于纵波声速为（5920±50）m/s，横波声速为（3255±30）m/s的钢材。 在以不同速度测试材料时，有必要考虑这一事实。 本文件参考了ISO 16828，并就TOFD在熔焊接头不连续性检测、定位、尺寸确定和表征方面的具体能力和局限性提供了指导。TOFD可作为一种独立的方法，或与其他无损检测（NDT）方法或技术结合使用，用于制造检验和在役检验。 本文件根据ISO 17635规定了四个测试级别（A、B、C、D），并相应地提高了测试可靠性。提供了关于测试级别选择的指导。 本文件允许出于验收目的对TOFD指示进行评估。该评估基于对生成的TOFD图像中的透射、反射和衍射超声信号的评估。 本文件不包括不连续性的验收等级。

This document specifies the application of the time-of-flight diffraction (TOFD) technique to the semi- or fully automated ultrasonic testing of fusion-welded joints in metallic materials of minimum thickness 6 mm. It applies to full penetration welded joints of simple geometry in plates, pipes, and vessels, where both the weld and the parent material are low-alloyed carbon steel. Where specified and appropriate, TOFD can also be used on other types of materials that exhibit low ultrasonic attenuation (especially that due to scatter). Where material-dependent ultrasonic parameters are specified in this document, they are based on steels having a sound velocity of (5 920 ± 50) m/s for longitudinal waves and (3 255 ± 30) m/s for transverse waves. It is necessary to take this fact into account when testing materials with a different velocity. This document makes reference to ISO 16828 and provides guidance on the specific capabilities and limitations of TOFD for the detection, location, sizing and characterization of discontinuities in fusion-welded joints. TOFD can be used as a stand-alone method or in combination with other non-destructive testing (NDT) methods or techniques, for manufacturing inspection, and for in-service inspection. This document specifies four testing levels (A, B, C, D) in accordance with ISO 17635 and corresponding to an increasing level of testing reliability. Guidance on the selection of testing levels is provided. This document permits assessment of TOFD indications for acceptance purposes. This assessment is based on the evaluation of transmitted, reflected and diffracted ultrasonic signals within a generated TOFD image. This document does not include acceptance levels for discontinuities.