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、管和容器中简单几何形状的全熔透焊接接头，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材料，这些材料表现出低超声衰减（特别是由于散射）。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和横波声速为（3255±30）m/s的钢。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，并对TOFD的具体功能和限制提供了指导熔焊接头不连续性的检测、定位、尺寸和特征。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规定了四个测试等级（A、B、C、D），对应于不断提高的测试可靠性等级。提供了选择测试级别的指导。本文件允许为验收目的评估TOFD显示。此评估基于对生成的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.