1.1 本规程涵盖了通过磁响应或磁导率测量估算铸造不锈钢微观结构铁素体含量所用仪器的校准程序。本程序涵盖一次仪表和二次仪表。 1.1.1 主要仪器是使用美国国家标准技术研究所标准参考材料（NIST-SRM）厚度涂层标准进行校准的仪器。它是一种用于测试样本的实验室工具。一些主要仪器可用于直接测量铸件的铁素体含量。 1.1.2 二次仪表是指使用二次标准进行校准的仪表，二次标准由校准的一次仪表测量。二次仪表用于直接测量铸件的铁素体含量。 1.2 以国际单位制或英寸-磅单位表示的数值应单独视为标准值。每个系统中规定的值可能不是精确的等效值；因此，每个系统应相互独立使用。将两个系统的值合并可能会导致不符合标准。 1.2.1 在文本中，国际单位显示在括号中。 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 奥氏体不锈钢中存在的铁素体数量已表明会影响这种铸造合金的强度、韧性和耐腐蚀性。铁素体的数量往往与钢的磁导率密切相关。本标准中描述的方法涵盖了通过钢的磁导率估算铁素体的校准实践。这种方法在铸件的大面积上使用成本低廉，并且是无损的。 4.2 该实践已用于研究、合金开发、质量控制和制造控制。 4.2.1 许多仪器具有不同的设计和不同的工作原理。当探头放置在所研究的材料上时，形成闭合磁路，允许测量磁导率。当使用已知铁素体含量的标准进行校准时，磁导率表示所分析材料的铁素体含量。估计的铁素体含量从校准的刻度盘或数字读出刻度盘读取。按照制造商的说明正确校准仪器。 4.3 由于本规程测量的是磁力而不是铁氧体，因此它受影响磁导率的所有变量的影响，例如铁氧体相的形状、尺寸、取向和成分。这些反过来又受到热历史的影响。用磁性方法测量铁素体也被发现受到所分析材料表面光洁度的影响。 4.4 除非制造商和买方同意，否则不得使用磁性方法仲裁铁素体含量的冲突。

1.1 This practice covers the procedure for calibration of instruments to be used for estimating the ferrite content of the microstructure of cast stainless steels by magnetic response or measurement of permeability. This procedure covers both primary and secondary instruments. 1.1.1 A primary instrument is one that has been calibrated using National Institute of Standards and Technology-Standard Reference Material (NIST-SRM) thickness coating standards. It is a laboratory tool to be used with test specimens. Some primary instruments may be used to directly measure the ferrite content of castings. 1.1.2 A secondary instrument is one that has been calibrated by the use of secondary standards that have been measured by a calibrated primary instrument. Secondary instruments are to be used to directly measure the ferrite content of castings. 1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard. 1.2.1 Within the text, the SI units are shown in brackets. 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 The amount of ferrite present in an austenitic stainless steel has been shown to influence the strength, toughness, and corrosion resistance of this type of cast alloy. The amount of ferrite present tends to correlate well with the magnetic permeability of the steel. The methods described in this standard cover calibration practice for estimating ferrite by the magnetic permeability of the steel. The practice is inexpensive to use over large areas of the cast part and is nondestructive. 4.2 This practice has been used for research, alloy development, quality control, and manufacturing control. 4.2.1 Many instruments are available having different designs and different principles of operation. When the probe is placed on the material being investigated, a closed magnetic circuit is formed allowing measurement of the magnetic permeability. When calibrated with standards having known ferrite content, this permeability indicates the ferrite content of the material being analyzed. The estimated ferrite content is read from a calibrated dial or from a digital readout dial. Follow the manufacturer's instructions for proper calibration of the instrument. 4.3 Since this practice measures magnetic attraction and not ferrite directly, it is subject to all of the variables that affect magnetic permeability, such as the shape, size, orientation, and composition of the ferrite phase. These in turn are affected by thermal history. Ferrite measurements by magnetic methods have also been found to be affected by the surface finish of the material being analyzed. 4.4 Magnetic methods should not be used for arbitration of conflicts on ferrite content except when agreed upon between manufacturer and purchaser.