1.1 本试验方法包括铁素体钢无延性转变（NDT）温度的测定， 5. / 8. 英寸（15.9mm）和更厚。 1.2 当询价、合同、订单或规范规定钢材应符合落锤试验确定的断裂韧性要求时，可使用该试验方法。 1.3 以英寸-磅单位表示的值应视为标准值。括号中给出的值是对SI单位的数学转换，仅供参考，不被视为标准值。 1.4 本标准并不旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者有责任在使用前建立适当的安全、健康和环境实践，并确定监管限制的适用性。 1.5 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《国际标准、指南和建议制定原则决定》中确立的国际公认标准化原则制定的。 =====意义和用途====== 5.1 在缺口条件下使用的铁素体钢的断裂强度转变受到温度的显著影响。对于给定的“低”温度，缺陷（缺口）的大小和锐度决定了脆性断裂开始所需的应力水平。该试验方法的重要性与确定该温度有关，该温度在本文中定义为无损检测温度， 图1 ，随着温度的降低，降至标称屈服强度应力水平，即标记为NDT的点 图1 . 图1 广义断裂分析图，显示了在不同标称应力水平下断裂起始所需的缺陷尺寸的大致范围，由无损检测温度参考 3. , 4. CAT（裂纹止裂温度）–扩展脆性断裂的止裂温度。因此，CAT曲线是与裂纹停止相关的应力-温度曲线。 FTE（断裂过渡弹性）温度——应力水平等于屈服强度时的裂纹止裂温度，因此标志着纯弹性载荷下断裂扩展的最高温度。 FTP（断裂转变塑性）温度——高于断裂完全剪切的温度，即不显示解理断裂的中心区域，断裂所需的应力接近钢的抗拉强度。 5.2 可通过使用广义缺陷尺寸、应力-温度图（如 图1 该图来源于多种试验，包括断裂起始和断裂停止试验，与落锤试验确定的无损检测温度相关。通过与船舶、压力容器、机械部件、锻件和铸钢应用中遇到的许多服务故障的相关性，已记录了无损检测温度的验证。 5.3 落锤试验发展相关参考文献列表。与NDT温度与服务故障的相关性相关的参考文献和与中子辐照脆化相关的参考参考文献如下 17 关于精度和偏差。

1.1 This test method covers the determination of the nil-ductility transition (NDT) temperature of ferritic steels, 5 / 8 in. (15.9 mm) and thicker. 1.2 This test method may be used whenever the inquiry, contract, order, or specification states that the steels are subject to fracture toughness requirements as determined by the drop-weight test. 1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard. 1.4 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. 1.5 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 ====== 5.1 The fracture-strength transitions of ferritic steels used in the notched condition are markedly affected by temperature. For a given “low” temperature, the size and acuity of the flaw (notch) determines the stress level required for initiation of brittle fracture. The significance of this test method is related to establishing that temperature, defined herein as the NDT temperature, at which the “small flaw” initiation curve, Fig. 1 , falls to nominal yield strength stress levels with decreasing temperature, that is, the point marked NDT in Fig. 1 . FIG. 1 Generalized Fracture Analysis Diagram Indicating the Approximate Range of Flaw Sizes Required for Fracture Initiation at Various Levels of Nominal Stress, as Referenced by the NDT Temperature 3 , 4 CAT (crack arrest temperature)–the temperature of arrest of a propagating brittle fracture. CAT curve is thus a stress versus temperature curve as related to crack arrest. FTE (fracture transition elastic) temperature–the crack arrest temperature for a stress level equal to the yield strength thus marks the highest temperature of fracture propagation for purely elastic loads. FTP (fracture transition plastic) temperature–the temperature above which fractures are entirely shear, that is, show no center regions of cleavage fracture, and the stress required for fracture approximates the tensile strength of the steel. 5.2 Interpretations to other conditions required for fracture initiation may be made by the use of the generalized flaw-size, stress-temperature diagram shown in Fig. 1 . The diagram was derived from a wide variety of tests, both fracture-initiation and fracture-arrest tests, as correlated with the NDT temperature established by the drop-weight test. Validation of the NDT temperature has been documented by correlations with numerous service failures encountered in ship, pressure vessel, machinery component, forged, and cast steel applications. 5.3 Lists of Selected References Relating to Development of Drop-Weight Test. Selected References Relating to Correlation of NDT temperature to Service Failures, and Selected References Relating to Neutron Irradiation Embrittlement are presented following Section 17 on Precision and Bias.