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This standard is drafted in accordance with the rules given in the GB/T 1.1-2009
This part replaces GB/T 224-2008 Determination of the Depth of Decarburization of Steels in whole.
The following technical deviations have been made with respect to the GB/T 224-2008 (the previous edition):
— deletion of the term “depth of ferritic decarburization” and its definition (Clause 3 of Edition 2008);
— modification of the “Sampling” (see Clause 4; paragraph 3 of 4.1, 4.2.2, 4.4.1 and 4.4.2 of Edition 2008);
— addition of the average method (see 5.2.3);
— addition of the specific method for measuring the micro-indentation Knoop hardness and micro-hardness impressions (see 5.3.1);
— addition of the electron probe microanalysis (see 5.4.4);
— addition of the glow discharge optical emission spectrometry (see 5.4.5);
— addition of the exact decimal places for different measurements of the depth of decarburization (see Clause 6).
This standard has been redrafted and modified adoption of International Standard ISO 3887:2017 Steels — Determination of the Depth of Decarburization.
Compared with ISO 3887:2017, this standard has the following technical differences and causes:
— The adjustments of technical deviations are made for the normative references in this standard so as to adapt to the technical conditions of China. The adjustment is mainly reflected in Clause 2 "Normative References", with the specific adjustments as follows:
ISO 6507-1 is replaced by GB/T 4340.1 which is modified adoption of the International Standard (see 5.3.3);
ISO 4545-1 is replaced by GB/T 18449.1 which is modified adoption of the International Standard (see 5.3.3);
ISO 15349-2 is replaced by GB/T 20126 which is identical with the International Standard (see 5.4.2.2);
ISO 14707 is replaced by GB/T 19502 which is identical with the International Standard (see 5.4.5.1);
addition of references GB/T 30067 (see Clause 3), GB/T 13298 (see 5.2.2), GB/T 15247 (see 5.4.2.3), GB/T 4336 (see 5.4.3.2), GB/T 22368 (see 5.4.5.1);
— addition of the requirements for sample state in Clause 4 "Sampling" (see 4.1), by reason of the sample state has a great influence on the depth of decarburization, so the requirements for sample state are unified to avoid quality disputes;
— addition of requirements of "total test perimeter not less than 35 mm" for large samples and the sampling schematic diagram in Clause 4 "Sampling” (see 4.3 and Figures 2 to 4), which is included in GB/T 224-2008 to improve the operability of sampling;
— addition of the “The depth of total decarburization of bearing steel, tool steel and spring steel shall be measured at the deepest position” (see 5.2.3.1), which had been specified in GB/T 224-2008 and applicable to the national conditions of China;
— deletion of the 5.4.4 of ISO 3887:2017, its contents are included in 5.4.2.3 and 5.4.3.3, respectively;
— modification of treatment method for the test results in 5.4.2 “Chemical analysis” and 5.4.3 “Spectrographic analysis” (see 5.4.2.3), keeping consistent with GB/T 224-2008, and applicable to the national conditions of China.
For the purposes of this standard, the following editorial changes have also been made:
— in order to be consistent with the existing standard series, the standard name is changed to Determination of the Depth of Decarburization of Steels.
— addition of the metallographic structure of surface decarburization of GCr15 (see Figure A.3).
This standard was proposed by China Iron and Steel Association.
This standard is under the jurisdiction of SAC/TC 183 (National Technical Committee on Iron and Steel of Standardization Administration of China).
The previous editions of the standard replaced by this standard are as follows:
Determination of the Depth of Decarburization of Steels
1 Scope
This standard specifies the requirements for sampling, measuring methods and test reports of the decarburization of steel products.
This standard is applicable to the determination of the depth of decarburization of steels (billets) and their parts.
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 4336 Carbon and Low-alloy Steel — Determination of Multi-element Contents — Spark Discharge Atomic Emission Spectrometric Method (Routine Method)
GB/T 4340.1 Metallic Materials — Vickers Hardness Test — Part 1: Test Method (GB/T 4340.1, ISO 6507-1:2005, MOD)
GB/T 13298 Inspection Methods of Microstructure for Metals
GB/T 15247 Microbeam Analysis — Electron Probe Microanalysis — Guidelines for Determining the Carbon Content of Steels Using Calibration Curve Method (GB/T 15247-2008, ISO 16592:2006, IDT)
GB/T 18449.1 Metallic Materials — Vickers Hardness Test — Part 1: Test Method (GB/T -2009, ISO 4545-1:2005, MOD)
GB/T 19502 Surface Chemical Analysis — Glow Discharge Optical Emission Spectrometry (GD-OSE) — Introduction to Use (GB/T 19502-2004, ISO 14707:2000, IDT)
GB/T 20126 Unalloyed Steel — Determination of Low Carbon Content — Part 2: Infrared Absorption Method after Combustion in an Induction Furnace (with Preheating) (GB/T 20126-2006, ISO 15349-2:1999, IDT)
GB/T 30067 Standard Terminology Relating to Metallography
ISO 9556 Steel and Iron — Determination of Total Carbon Content — Infrared Absorption Method after Combustion in an Induction Furnace
ISO 14594 Microbeam Analysis — Electron Probe Microanalysis — Guidelines for the Determination of Experimental Parameters for Wavelength Dispersive Spectroscopy
3 Terms and Definitions
For the purposes of this document, the terms and definitions given in GB/T 30067 and the following apply.
3.1
decarburization
reduction of carbon content from the surface zone of the steel The reduction of carbon include:
a) partial decarburization, measured as the distance from the point at which the carbon content exceeds the solubility limit in ferrite, becoming visible as e.g. pearlite, to the point at which there is no more visible difference to the core carbon concentration;
b) complete decarburization, also called ferrite decarburization, measured as the distance between the surface of the product and the point up to which the carbon content is below the solubility limit of carbon in ferrite so that only ferrite is present.
Note: The depth of complete decarburization as described in b) is determined by examination of the microstructure.
3.2
depth of functional decarburization
distance between the surface of the product and the point at which the carbon content or hardness is at the level where the performance of the product would be unaffected by a reduction in carbon content (i.e. at the minimum level specified in the product standard)
3.3
depth of total decarburization
distance between the surface of the product and the point at which the carbon content is that of the unaffected core, the sum of the partial and the complete decarburization
The various bands of decarburization are shown diagrammatically in Figure 1.
Note: If the product has undergone a process involving carburization, the definition of the “core” shall form the subject of an agreement between the parties concerned. The permissible depth of decarburization shall be specified in the appropriate standard covering the product or shall be the subject of an agreement between the parties concerned.
Key:
d1 — the depth of complete decarburization, in millimetres (mm);
d2 — the depth of functional decarburization, in millimetres (mm);
d3 — the depth of partial decarburization, in millimetres (mm);
d4 — the depth of total decarburization, in millimetres (mm);
a — the minimum carbon content specified in the product standard;
b — core carbon content.
Note: The boundaries separating the various types of decarburization are shown as hatched bands with the width of the band illustrating the practical variability in measurements due to the uncertainty of interpretation.
Figure 1 Schematic representation for a typical decarburization
4 Sampling
4.1 Samples shall be inspected in the state of delivery without further heat treatment. If additional heat treatment is required as agreed by the parties concerned, attention should be paid to the prevention of changes in carbon distribution and mass fraction, such as the use of small samples, short austenitization time, neutral protective atmosphere, etc.
4.2 Samples should be taken at locations that are representative of the bulk specimen. The location and number of samples taken depend on the nature of the material to be tested and are defined by agreement between the parties concerned.
Foreword II 1 Scope 2 Normative References 3 Terms and Definitions 4 Sampling 5 Measuring Methods 6 Test Report Annex A (Informative) Examples of Typical Decarburization Microstructure Measured by Metallographic Method
ICS 77.040.99 H 24 中华人民共和国国家标准 GB/T 224—2019 代替GB/T 224—2008 钢的脱碳层深度测定法 Determination of the depth of decarburization of steels (ISO 3887：2017，Steels—Determination of the depth of decarburization，MOD) 2019-06-04发布 2020-05-01实施 国家市场监督管理总局 中国国家标准化管理委员会 发布 前言 本标准按照GB/T 1.1—2009给出的规则起草。 本标准代替GB/T 224—2008《钢的脱碳层深度测定法》。 本标准与GB/T 224—2008相比，主要技术内容变化如下： ——删除了术语“铁素体脱碳层深度”及其定义(2008年版第3章)； ——修改了“取样”(见第4章，2008年版的4.1第三段、4.2.2、4.4.1和4.4.2)； ——增加了平均法(见5.2.3)； ——增加了显微努氏硬度法和显微硬度压痕的具体打法(见5.3.1)； ——增加了电子探针法(见5.4.4)； ——增加了辉光光谱法(见5.4.5)； ——增加了不同测量方法对应脱碳层深度的精确位数(见第6章)。 本标准使用重新起草法修改采用ISO 3887：2017《钢 脱碳层深度的测定》。 本标准与ISO 3887：2017的技术性差异及其原因如下： ——关于规范性引用文件，本标准做了具有技术性差异的调整，以适应我国的技术条件，调整的情况集中反映在第2章“规范性引用文件”中，具体调整如下： ●用修改采用国际标准的CB/T 4340.1代替了ISO 6507-1(见5.3.3)； ●用修改采国际标准用的GB/T 18449.1代替了ISO 4545-1(见5.3.3)； ●用等同采用国际标准的GB/T 20126代替了ISO 15349-2(见5.4.2.2)； ●用等同采用国际标准的GB/T 19502代替了ISO 14707(见5.4.5.1)； ●增加引用了GB/T 30067(见第3章)、GB/T 13298(见5.2.2)、GB/T 15247(见5.4.2.3)、GB/T 4336(见5，4.3.2)、CB/T 22368(见5.4，5.1)； ——增加了第4章“取样”中试样状态的要求(见4.1)，试样状态对脱碳层深度影响很大，统一试样状态要求，避免质量纠纷； ——增加了第4章“取样”中大试样“总检测周长不小于35 mm”的要求和取样示意图(见4.3及图2～图4)，GB/T 224—2008版本有这部分内容，提高了取样的可操作性； ——增加了“轴承钢、工具钢、弹簧钢测量最深处的总脱碳层深度”(见5.2.3.1)，GB/T 224—2008版本有这部分内容，适用于中国国情； ——删除了ISO 3887：2017的5.4.4，其内容分别列入5.4.2.3和5.4.3.3； ——修改了5.4.2化学分析法和5.4.3直读光谱分析法中试验结果的处理方法(见5.4.2.3)，保持与GB/T 224—2008版本一致，适用于中国国情。 本标准做了下列编辑性修改： ——为与现有标准系列一致，将标准名称改为《钢的脱碳层深度测定法》； ——增加了GCr15表面脱碳的金相组织(见图A.3)。 本标准由中国钢铁工业协会提出。 本标准由全国钢标准化技术委员会(SAC/TC 183)归口。 本标准所代替标准的历次版本发布情况为： ——GB 224—1963、GB 224—1978、GB/T 224—1987、GB/T 224—2008。 钢的脱碳层深度测定法 1范围 本标准规定了钢的脱碳层取样、测定方法和试验报告的要求等。 本标准适用于测定钢材(坯)及其零件的脱碳层深度。 2规范性引用文件 下列文件对于本文件的应用是必不可少的。凡是注日期的引用文件，仅注日期的版本适用于本文件。凡是不注日期的引用文件，其最新版本(包括所有的修改单)适用于本文件。 GB/T 4336碳素钢和中低合金钢 多元素含量的测定 火花放电原子发射光谱法(常规法) GB/T 4340.1 金属材料 维氏硬度试验 第1部分：试验方法(GB/T 4340.1—2009，ISO 6507—1：2005，MOD) GB/T 13298金属显微组织检验方法 GB/T 15247微束分析 电子探针显微分析 测定钢中碳含量的校正曲线法(GB/T 15247—2008，ISO 16592：2006，IDT) GB/T 18449.1 金属材料 努氏硬度试验 第1部分：试验方法(GB/T 18449.1—2009，ISO 4545-1：2005，MOD) GB/T 19502表面化学分析 辉光放电发射光谱方法通则(GB/T 19502—2004，ISO 14707：2000，IDT) GB/T 20126非合金钢 低碳含量的测定 第2部分：感应炉(经预加热)内燃烧后红外吸收法(GB/T 20126—2006，ISO 15349-2：1999，IDT) GB/T 22368低合金钢 多元素含量的测定 辉光放电原子发射光谱法(常规法) GB/T 30067 金相学术语 ISO 9556钢铁 总碳含量的测定 感应炉燃烧后红外吸收法(Steel and iron—Determination of total carbon content—Infrared absorption method after combustion in an induction furnace) ISO 14594微束分析 电子探针显微分析 波长离散分光计实验参数的设定导则(Microbeam analysis—Electron probe microanalysis—Guidelines for the determination of experimental parameters for wavelength dispersive spectroscopy) 3术语和定义 GB/T 30067界定的以及下列术语和定义适用于本文件。 3.1 脱碳decarburization 钢表层上碳的损失。这种碳的损失包括： a)部分脱碳partial decarburization，钢材试样表面含碳量减少到低于基体含碳量，并且大于室温时碳在铁素体中固溶极限； b)完全脱碳complete decarburization，也叫铁素体脱碳层，试样表层碳含量水平低于碳在铁素体中最大固溶度，只有铁素体存在。 注：b)中所描述的完全脱碳层只有铁素体组织存在，应用金相法测定。 3.2 有效脱碳层深度depth of functional decarburization 从试样表面到规定的碳含量或硬度水平的点的距离，规定的碳含量或硬度水平应以不因脱碳而影响使用性能为准(例如：产品标准中规定的碳含量最小值)。 3.3 总脱碳层深度depth of total decarburization 从试样表面到碳含量等于基体碳含量的那一点的距离，等于部分脱碳和完全脱碳之和。 不同的脱碳带见图1。 注：如果制品经过渗碳处理，“基体”的定义由有关各方商定。允许的脱碳层深度将被列入产品技术标准中，或者由有关各方商定。
