1.1 本规程涵盖了通过计算机断层扫描（CT）技术检查铸件的统一程序。本规程中提出的要求旨在控制CT无损检测的质量，而不是控制铸件的可接受性或质量。这一做法暗指使用穿透辐射，特别是X射线和γ射线。 1.2 本规程为铸件的CT检查提供了统一程序，用于以下一个或多个目的: 1.2.1 检查不连续性，如孔隙度、夹杂物、裂纹和收缩； 1.2.2 进行计量测量并确定尺寸一致性；和 1.2.3 确定逆向工程数据，即创建计算机- 辅助设计（CAD）数据文件。 1.3 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 4.1 当物体处于铸态、中间或最终加工状态时，可以对其进行CT。 CT检查可作为一种设计工具，用于改善蜡的形状和成型，确定工艺参数，随机检查工艺控制，执行零件验收或拒收的最终质量控制（QC）检查，分析故障并延长部件寿命。 4.2 铸件CT最常见的应用是:定位和表征不连续性，如气孔、夹杂物、裂纹和收缩；测量铸态零件尺寸，以与设计尺寸进行比较；以及提取用于逆向工程的尺寸测量值。 4.3 CT图像再现物体或物体内特征的程度在很大程度上取决于空间分辨率、对比度辨别、物体本身的特定几何形状和材料以及成像系统的伪影的竞争影响。 操作参数在图像质量、检查时间和成本之间达成整体平衡。 4.4 伪影通常是CT图像质量的限制因素。（参见实践 E1570 对于工件的深入讨论。）伪影是图像中与对象中的实际特征无关的可再现特征。伪影可以被视为相关噪声，因为它们在给定条件下形成可重复的固定模式，但不携带任何对象信息。对于铸件，必须认识到什么是和什么不是人工制品，因为人工制品可能会模糊或伪装为不连续。伪影最常见于具有长直边或复杂几何形状的铸件中，或两者兼有。

1.1 This practice covers a uniform procedure for the examination of castings by the computed tomography (CT) technique. The requirements expressed in this practice are intended to control the quality of the nondestructive examination by CT and are not intended for controlling the acceptability or quality of the castings. This practice implicitly suggests the use of penetrating radiation, specifically X rays and gamma rays. 1.2 This practice provides a uniform procedure for a CT examination of castings for one or more of the following purposes: 1.2.1 Examining for discontinuities, such as porosity, inclusions, cracks, and shrink; 1.2.2 Performing metrological measurements and determining dimensional conformance; and 1.2.3 Determining reverse engineering data, that is, creating computer-aided design (CAD) data files. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 4.1 CT may be performed on an object when it is in the as-cast, intermediate, or final machined condition. A CT examination can be used as a design tool to improve wax forms and moldings, establish process parameters, randomly check process control, perform final quality control (QC) examination for the acceptance or rejection of parts, and analyze failures and extend component lifetimes. 4.2 The most common applications of CT for castings are for the following: locating and characterizing discontinuities, such as porosity, inclusions, cracks, and shrink; measuring as-cast part dimensions for comparison with design dimensions; and extracting dimensional measurements for reverse engineering. 4.3 The extent to which a CT image reproduces an object or a feature within an object is dictated largely by the competing influences of spatial resolution, contrast discrimination, the specific geometry and material of the object itself, and artifacts of the imaging system. Operating parameters strike an overall balance between image quality, examination time, and cost. 4.4 Artifacts are often the limiting factor in CT image quality. (See Practice E1570 for an in-depth discussion of artifacts.) Artifacts are reproducible features in an image that are not related to actual features in the object. Artifacts can be considered correlated noise because they form repeatable fixed patterns under given conditions yet carry no object information. For castings, it is imperative to recognize what is and is not an artifact since an artifact can obscure or masquerade as a discontinuity. Artifacts are most prevalent in castings with long straight edges or complex geometries, or both.