標準編號:	GB/T 6394-2017
中文名稱:	金屬平均晶粒度測定方法
英文名稱:	Metal - Methods for estimating the average grain size
中標分類:	H24    金相檢驗方法
行業分類:	GB    國家標準
ICS分類:	77.040.99 77.040.99    金屬材料的其他試驗方法 77.040.99
發布機構:	中華人民共和國國家質量監督檢驗檢疫總局 中國國家標準化管理委員會
發布日期:	2017-03-03
實施日期:	2017-11-1
標準狀態:	valid
替代舊標準:	GB/T 6394-2002 金屬平均晶粒度測定法
翻譯語言:	英文
文件格式:	PDF
中文字符數:	33000 字
翻譯價格(元):	330.0
交付時間:	付款后 1 個工作日

Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative. This standard is developed in accordance with the rules given in GB/T 1.1-2009. This standard replaces GB/T 6394-2002 Metal-Methods for Estimating the Average Grain Size. The following main technical changes have been made with respect to GB/T 6394-2002: ——The terms "grain boundary", "grain boundary intersection count", "grain intercept count" and "intercept length" and their definitions are added (see Chapter 3); ——The heat treatment method, sampling location, specimen orientation, polished surface area, preparation requirements, etc. of specimen forming austenite grains are added (see Chapters 6 and 7); ——Requirements for test parameters, selection of fields and rating details are added in the comparison procedure (see 8.1); ——Requirement of using the Chart IV for outlining the grains with cementite is added (see Table 2 in 8.1.1.3). ——Values of grain diameter and magnification corresponding to 400X and 500X rating charts are modified, and the converted values of 500X and 1,000X rating charts are added (See Tables 3 and 4 in 8.1.2.3); ——Calculation formulae for rectangular test grid are added in planimetric procedure, and methods for selection of fields and precision of counting are added (see 8.2.2); ——Contents of intercept procedure are modified, and calculation formulae of intercept procedure are added (see 8.3.1.8); ——Calculation methods for non-equiaxed grains are added, and the calculation process is defined (see Chapter 9); ——Phase characteristics and proportion determination reporting requirements are added for estimation of two-phase and multi-phase grains, and intercept procedure is added (see 10.4.3); ——Essential data for determination with planimetric procedure and intercept procedure and requirements for contents of reports about non-equiaxed grains and multi-phase grains are added, and report on grain size is improved (see Chapter 11); ——Requirements for precision and bias are added (see Chapter 12); ——Annex C - "Establishing and Outlining of Austenite Grain Size of Ferritic and Austenitic Steels" in the former standard is revised to Annex A - "Establishing and Outlining Methods for Grain Size", the quenching temperature in establishing of austenite grains is all changed from 900℃ to 890℃, fine pearlite outlining procedure is added, the etchants for parts of grain sizes and their application methods are added, and the method for determination of ferrite grain of ferritic steel is added (see A.2); ——Annex B is revised from "Calculation for Confidence Limit and Relative Error of Grain Size Determination Results" to "Statistical Techniques - Calculation for Confidence Interval and Relative Error of Grain Size Determination Results", and the calculation methods are corrected; ——In Annex C, the calculation formulae and derivation process used in various measurement methods for grain size are added (see C.1), the relationship between common measurements, calculation and conversion methods of relative data and the difference between routine measurement methods of grain size are added (see C.2), the relationship between grain size in this standard and ISO grain size and the relationship between micro-grain size number and macro-grain size number are added (see C.3). This standard was proposed by China Iron and Steel Association. This standard is under the jurisdiction of the National Technical Committee on Iron and Steel of Standardization Administration of China (SAC/TC 183). The previous editions of this standard are as follows: ——GB/T 6394-1986; GB/T 6394-2002. ? Introduction In order to determine the average grain size of metal, comparison procedure is primarily used, and intercept procedure and planimetric procedure may also be used. These basic procedures are on the basis of the geometric figures of grains, are independent of the metal or alloy concerned, and may also be used for the estimation of average grain, crystal or cell size in nonmetallic materials. The comparison procedure may be used if the structure of the material approaches to the appearance of one of the standard rating charts. However, the rating charts in comparison procedure cannot not be used for measurement of individual grains. Test methods described in this standard are only used to measure the average grain size of specimens with a unimodal grain size distribution. For the specimens with bimodal (or more complex) size distributions, the grain size shall be measured in accordance with this standard and YB/T 4290 Test Methods for Estimating the Largest Grain Observed in a Metallographic Section (ALA Grain Size), and the grain distribution characteristics shall be characterized in accordance with GB/T 24177 Standard Test Methods for Characterizing Duplex Grain Sizes. For the specimens with individual very coarse grains in a fine grained matrix, the determination of ALA grain size may be carried out in accordance with YB/T 4290. Determination of Estimating the Average Grain Size of Metal 1 Scope 1.1 This standard specifies the representation and determination methods for average grain size of metallic structure, including comparison procedure, planimetric procedure and intercept procedure; these methods are applicable to single-phase structure, but they, with specific requirements, may also be applied to determine the average size of a particular type of grain in a multi-phase or multi-constituent specimen. These methods may also be applied to nonmetallic materials with structures having appearances similar to those of the metallic structures shown in the comparison charts. 1.2 This standard is applied to determine the average grain size of specimens with a unimodal distribution (similar to lognormal distribution) of grain areas, diameters or intercept lengths, and is not applicable to the grain size in bimodal distribution. Characterization of duplex grain size is described in GB/T 24177. Test methods for determining individual very coarse grains in a fine grained matrix are described in YB/T 4290. 1.3 This standard deals only with determination of planar grain size. Determination of spatial grain size, that is, measurement of the size of the three-dimensional grains, is beyond the scope of this standard. 1.4 This standard deals only with the recommended test methods and nothing in it should be construed as defining or establishing limits of acceptability or fitness of purpose of the materials tested. 2 Normative References The following documents for the application of this document are essential. Any dated reference, just dated edition applies to this document. For undated references, the latest edition (including any amendments) applies to this document. GB/T 4335 Determination of Ferrite Grain Size for Cold Rolled Low Carbon Steel Sheets GB/T 13298 Inspection Methods of Microstructure for Metals GB/T 24177 Standard Test Methods for Characterizing Duplex Grain Sizes GB/T 30067 Standard Terminology Relating to Metallography YB/T 4290 Test Methods for Estimating the Largest Grain Observed in a Metallographic Section (ALA Grain Size) 3 Terms and Definitions For the purposes of this document, the terms and definitions defined in GB/T 30067 and the following apply. 3.1 grain boundary a very narrow region in a polycrystalline material corresponding to the transition from one crystallographic orientation to another, thus separating one adjacent grain from another 3.2 grain a whole area enclosed by grain boundary, that is, the area within the original grain boundary observed on two-dimensional plane or the volume enclosed by the original grain boundary planes on three-dimensional body. Twin-plane boundary is not considered for materials with twin-plane boundary 3.3 grain size a magnitude of grain size. Generally, length, area, volume or grain size number are used for representing the grain size estimated or determined with different methods, while the grain size represented by grain size number is unrelated to the measurement method and unit 3.4 micro-grain size number G the micro-grain size number G is defined as: N100=2G-1 (1) 3.5 macro-grain size number Gm the macro-grain size number Gm is defined as: (2) 3.6 grain boundary intersection count Pi determination of the number of times a test line cuts across, or is tangent to grain boundaries, which is called the intersection count for short 3.7 grain intercept count Ni determination of the number of times a test line cuts through individual grains on the plane tested, which is called the intercept count for short 3.8 intercept length l the distance between two grain boundary intersection points on a test line segment that crosses the grain 4 Symbols The symbols adopted in this standard and their descriptions are given in Table 1. Table 1 Symbols and Descriptions Symbol Unit Name and description α — Matrix grains in a two-phase structure A mm2 Test area mm2 Average grain area in test grid at 1X AIl — Elongation ratio (or anisotropy coefficient for a longitudinally oriented plane) of non-equiaxed grain mm Average planar grain diameter mm Average spatial grain diameter G — Micro-grain size number Gm — Macro-grain size number G0 — ISO grain size number G′ — Grain size number estimated with a nonstandard magnification for comparison rating chart during determination of micro grain size — Grain size number estimated with a nonstandard magnification for comparison rating chart during determination of macro grain size l — Intercept length mm Average intercept length at 1X lO mm Average intercept length at the magnification Mb mm Average intercept length of the α matrix phase in a two-phase microstructure mm Average intercept length on a longitudinally oriented surface for a non-equiaxed grain structure mm Average intercept length on a transversely oriented surface for a non-equiaxed grain structure mm Average intercept length on a planarly oriented surface for a non-equiaxed grain structure mm Average intercept parallel to the deformation direction on a longitudinally oriented surface mm Average intercept perpendicular to the deformation direction on a longitudinally oriented surface mm Average intercept perpendicular to the deformation direction on a transversely oriented surface mm Average intercept perpendicular to the deformation direction on a planarly oriented surface L mm Length of a test line M — Magnification used Mb — Base magnification, that is, magnification used by a standard rating chart (100X, 75X or 1X) n — Number of fields measured N — Number of grain cross sections on a known test area A at the specified magnification M — Average value of the number N of several fields NL — Number of intercepts per unit length (mm) of test line crossing the grain at 1X Nα — Number of α matrix grains intercepted by the test line in a two-phase (constituent) microstructure NA — Number of grain cross sections per mm2 test area at 1X N1 — Number of grains per 645.16mm2 at 1X N100 — Number of grains per 645.16mm2 at 100X NAα — Number of α matrix grains per mm2 at 1X in a two-phase microstructure NAO — Number of grains per unit area (mm2) at the magnification Mb NAl — NA on a longitudinally oriented surface for a non-equiaxed grain structure NAt — NA on a transversely oriented surface for a non-equiaxed grain structure NAp — NA on a planarly oriented surface for a non-equiaxed grain structure Ni — Number of intercepts on a test line of known length L NInside — Number of grains completely within a test grid NIntercepted — Number of grains intercepted by the test grid NL — Number of grain intercepts per unit length (mm) of test line at 1X NiO — Number of grains intercepted by the test line at the magnification Mb NLl — NL on a longitudinally oriented surface for a non-equiaxed grain structure NLt — NL on a transversely oriented surface for a non-equiaxed grain structure NLP — NL on a planarly oriented surface for a non-equiaxed grain structure Pi — Number of grain boundary intersections with a test line PL — Number of grain boundary intersections per unit length (mm) of test line at 1X PLO — Number of intersections per unit length (mm) of test line at the magnification Mb PLl — PL on a longitudinally oriented surface for a non-equiaxed grain structure PLt — PL on a transversely oriented surface for a non-equiaxed grain structure PLp — PL on a planarly oriented surface for a non-equiaxed grain structure Q — Correction factor for comparison rating chart using a nonstandard magnification for microscopically determined grain size Qm — Correction factor for comparison rating chart using a nonstandard magnification for macroscopically determined grain size S — Standard deviation SV — Grain boundary surface area to volume ratio for a single-phase structure SVα — α matrix grain boundary surface area to volume ratio for a two-phase (constituent) structure t — Measurement times-related multiplier coefficient for determination of the confidence limit VVα — Volume fraction for α matrix in a two-phase structure AAα — Area fraction for α matrix in a two-phase structure 95%CI — 95% confidence interval of count 95%CL — 95% confidence interval of grain size %RA — Percent relative error Note 1: The average values are represented by aforesaid symbols with a transversal line (-). Note 2: The letter O is used as subscript to represent the number of grains (NAO), the number of intercepts (NiO), the number of intersections (PLO) or the intercept length (lO) in test at the base magnification Mb. 5 Generalities and Application 5.1 This standard specifies the basic procedures for determination of average grain size, including comparison procedure, planimetric procedure and intercept procedure. 5.2 Comparison procedure: The comparison procedure does not require counting of either grains, intersections or intercepts but involves comparison of standard rating charts, either in the form of a standard wall chart or an eyepiece reticle. There appears to be a general bias (size ±0.5) in estimating the grain size with comparison procedure. Repeatability and reproducibility of comparison chart ratings are generally ±1 grain size number. A minimum rating error can be realized if the grain appearances are completely similar to those shown in the standard rating charts. 5.3 Planimetric procedure: The planimetric procedure involves an actual count of the number of grains within a known area. The number of grains per unit area, NA, is used to determine the grain size number, G. The precision of the procedure is a function of the number of grains counted. A precision of ±0.25 grain size units can be attained with a reasonable amount of effort. Results are free of bias; repeatability and reproducibility are less than ±0.5 grain size units. An accurate count does require marking off of the grains as they are counted. 5.4 Intercept procedure: The intercept procedure involves an actual count of the number of grains intercepted by or the number of grain boundary intersections with a test line segment (or grid) of known length, used to calculate the number of intercepts, NL, or the number of intersections, PL, per unit length. NL or PL is used to determine the grain size number, G. The precision of the procedure is a function of the number of intersections or intercepts counted. An precision of better than ±0.25 grain size units can be attained with an effective amount of effort. Results are free of bias; repeatability and reproducibility are less than ±0.5 grain size units. Because an accurate count can be made without need of marking off intercepts or intersections, the intercept procedure is faster than the planimetric procedure for the same level of precision.

Foreword II Introduction IV 1 Scope 2 Normative References 3 Terms and Definitions 4 Symbols 5 Generalities and Application 6 Sampling 7 Specimen Preparation 8 Determination Procedures 9 Specimens with Non-equiaxed Grain Shapes 10 Grain Size of Specimens Containing Two- or Multi-phase Structure 11 Report on Grain Size 12 Precision and Bias Annex A (Normative) Establishing and Outlining Method of Grain Size Annex B (Normative) Statistical Techniques - Calculation for Confidence Interval and Relative Error of Grain Size Determination Results Annex C (Informative) Measurement Foundation of Grain Size

金屬平均晶粒度測定方法 1 范圍 1.1 本標準規定了金屬組織平均晶粒度的表示及測定方法，包含有比較法、面積法和截點法，適用于單相組織，但經具體規定后也適用于多相或多組元試樣中特定類型的晶粒平均尺寸測定。非金屬材料如組織形貌與比較評級圖中金屬組織相似也可參照使用。 1.2本標準利用晶粒的面積、直徑或截線長度的單峰分布(近似于對數正態分布)來測定試樣的平均晶粒度，不適用于雙峰分布的晶粒度。雙重晶粒度的評定見GB/T 24177。分布在細小晶粒基體上個別非常粗大的晶粒的測定方法見YB/T 4290。 1.3本標準僅適用平面晶粒度的測量，不適用于三維晶粒度，即立體晶粒尺寸的測量。 1.4本標準僅作為推薦性試驗方法，不能確定受檢材料是否接收或適合使用的范圍。 2規范性引用文件 下列文件對于本標準的應用是必不可少的，凡是注日期的引用文件，僅注日期的版本適用于本文件。凡是不注日期的引用文件，其最新版本(包括所有的修改單)適用于本文件。 GB/T 4335低碳鋼冷軋薄板鐵素體晶粒度測定法 GB/T 13298金屬顯微組織檢驗方法 GB/T 24177雙重晶粒度表征與測定方法 GB/T 30067 金相學術語 YB/T 4290金相檢測面上最大晶粒尺寸級別(ALA晶粒度)測定方法 3術語和定義 GB/T 30067界定的以及下列術語和定義適用于本文件。 3.1 晶界 grain boundary 對于多晶材料，從其一個結晶方向至另一個結晶方向過渡的很窄的區域，從而將相鄰的晶粒分離。 3.2 晶粒grain 晶界所包圍的整個區域。即是二維面上所觀察到的原始晶界范圍內的面積，或是三維物體上原始晶界面內所包圍的體積。對于有孿晶界面材料，孿晶界面不予考慮。 3.3 晶粒度grain size 晶粒大小的量度。通常使用長度、面積、體積或晶粒度級別數來表示不同方法評定或測定的晶粒大小，而使用晶粒度級別數表示的晶粒度與測量方法和使用單位無關。 3.4 顯微晶粒度級別數micro-grain size number G 顯微晶粒度級別數G定義為： N100=2G-1 …………………………(1) 3.5 宏觀晶粒度級別數macro-grain size number Gm 宏觀晶粒度級別數Gm定義為： …………………………(2) 3.6 晶界截點的計數grain boundry intersection count Pi 測量試驗線與晶界交截點或相切點的計數。簡稱截點數。 3.7 晶粒截線的計數grain intercept count Ni 被測量的平面上試驗線穿切過單個晶粒的次數。簡稱截線數。 3.8 截線長度intercept length l 測量線段通過晶粒時，與晶界相交的兩個交點之間的距離。 4 符號 本標準采用的符號與說明見表1。 表1 符號及其說明 符號 單位 名稱及說明 α — 兩相組織中的基體晶粒 A mm2 測量面積 mm2 1倍下測試網格內平均晶粒面積 AIl — 非等軸晶粒伸長率(或縱向平面各向異性系數) mm 平面晶粒平均直徑 mm 立體晶粒平均直徑 G — 顯微晶粒度級別數 Gm — 宏觀晶粒度級別數 G0 — ISO晶粒度級別數 G′ — 測定顯微晶粒度時，對比較評級圖使用非標準放大倍數評定的晶粒度級別 G′m — 測定宏觀晶粒度時，對比較評級圖使用非標準放大倍數評定的晶粒度級別 l — 截線長度 mm 1倍下的平均截距長度 lO mm 放大倍數Mb的平均截線長度 表1(續) 符號 單位 名稱及說明 mm 兩相顯微組織中基體α相的平均截線長度 mm 非等軸晶粒組織中縱向面上的平均截線長度 mm 非等軸晶粒組織中橫向面上的平均截線長度 mm 非等軸晶粒組織中法向面上的平均截線長度 mm 縱向面上平行變形方向的平均截距 mm 縱向面上垂直于變形方向上的平均截距 mm 橫向面上垂直變形方向的平均截距 mm 法向面上垂直變形方向的平均截距 L mm 試驗線長度 M — 所用的放大倍數 Mb — 基準放大倍數即標準評級圖所用的放大倍數(100倍、75倍或1倍) n — 測量視場數 N — 規定放大倍數M下，在已知試驗面積A上的晶粒截面計數 — 幾個視場計數N的平均值 NL — 1倍下單位長度(mm)試驗線穿過晶粒的截線數 Nα — 在兩相(組元)的顯微組織中，試驗線交截基體α晶粒的個數 NA — 1倍下每平方毫米試驗面積內的晶粒截面個數 N1 — 1倍下645.16 mm2內晶粒個數 N100 — 100倍下645.16 mm2內晶粒個數 NAα — 在兩相顯微組織中，1倍下每平方毫米內的基體α晶粒個數 NAO — 放大倍數Mb下的單位面積(mm2)內晶粒數 NAl — 非等軸晶粒組織中縱向面上的NA NAt — 非等軸晶粒組織中橫向面上的NA NAp — 非等軸晶粒組織中法向面上的NA Ni — 在已知長度L試驗線上的截線計數 N內 — 完全落在試驗網格內的晶粒個數 N交 — 被試驗網格所交截的晶粒個數 NL — 1倍下單位長度(mm)試驗線上晶粒截線數 NiO — 放大倍數Mb下試驗線所交截的晶粒數 NLl — 非等軸晶粒組織中縱向面上的NL NLt — 非等軸晶粒組織中橫向面上的NL NLP — 非等軸晶粒組織中法向面上的NL Pi — 晶界與試驗線的交點數 PL — 1倍下單位長度(mm)試驗線與晶界相交的截點數 表1(續) 符號 單位 名稱及說明 PLO — 放大倍數Mb下單位長度(mm)試驗線上的截點數 PLl — 非等軸晶粒組織中縱向面上的PL PLt — 非等軸晶粒組織中橫向面上的PL PLp — 非等軸晶粒組織中法向面上的PL Q — 測定顯微晶粒度時，對比較評級圖使用非標準放大倍數的修正系數 Qm — 測定宏觀晶粒度時，對比較評級圖使用非標準放大倍數的修正系數 S — 標準偏差 SV — 單相組織中晶粒晶界表面積與體積比 SVα — 兩相(組元)組織中基體α晶界表面積與體積比 t — 測定置信限用的與測量次數相關的乘積系數 VVα — 兩相組織中基體α的體積分數 AAα — 兩相組織中基體α的面積分數 95％CI — 計數的95％置信區間 95％CL — 晶粒度的95％置信區間 ％RA — 相對誤差百分數 注1：平均值以上述符號上面的加橫線表示。 注2：使用字母O作腳標，代表基準放大倍數Mb下檢驗的晶粒數NAO、截線數NiO、截點數PLO或者截線長度LO。 5概述與應用 5.1本標準規定了測定平均晶粒度的基本方法：比較法、面積法和截點法。 5.2 比較法：比較法不需計數晶粒、截點或截矩。與標準系列評級圖進行比較，評級圖有的是標準掛圖、有的是目鏡插片。用比較法評估晶粒度時一般存在一定的偏差(±0.5級)。評級值的重現性與再現性通常為±1級。當晶粒形貌與標準評級圖的形貌完全相似時，評級誤差最小。 5.3面積法：面積法是計數已知面積內晶粒個數，利用單位面積內晶粒數NA來確定晶粒度級別數G。該方法的精確度是晶粒計數的函數。通過合理計數可達到±0.25級的精確度。面積法的測定結果是無偏差的，重現性與再現性小于±0.5級。面積法精確度關鍵在于計數時一定要標記出已計數過的晶粒。 5.4截點法：截點法是計數已知長度的試驗線段(或網格)與晶粒截線或者與晶界截點的個數，計算單位長度截線數NL或者截點數PL來確定晶粒度級別數G。截點法的精確度是截點或截線計數的函數，通過有效的計數可達到優于±0.25級的精確度。截點法的測量結果是無偏差的，重現性和再現性小于±0.5級。對同一精度水平，截點法由于不需要標記就能準確的計數，因而較面積法測量快。 5.5對于等軸晶組成的試樣，使用比較法，評定晶粒度既方便又實用。對于批量生產的檢驗，其精度已足夠了。對于要求較高精度的平均晶粒度的測定，可以使用面積法和截點法。截點法對于拉長的晶粒組成試樣更為有效。 5.6在有爭議時，以截點法為仲裁方法。 5.7低碳鋼冷軋薄板鐵素體晶粒度的測定按GB/T 4335的規定執行。 5.8不能以標準評級圖為依據測定單個晶粒。因為標準評級圖的構成考慮到截平面與晶粒三維排列關系，顯示出晶粒從最小到最大排列分布所反映出有代表性的正態分布結果。所以不能用評級圖來測定單個晶粒。 5.9測定晶粒度時，應認識到晶粒度的測定并不是一種十分精確的測量。因為金屬組織是由不同尺寸和形狀的三維晶粒堆積而成。即使這些晶粒的尺寸和形狀相同，通過該組織的任一截面(檢驗面)上分布的晶粒大小，將從最大值到零之間變化。因此，在檢驗面上不可能有絕對尺寸均勻的晶粒分布，也不能有兩個完全相同的檢驗面。 5.10顯微組織中晶粒尺寸和位置都是隨機分布。不帶意向的移動視場，放置測量網格，隨機測量平均晶粒度才有代表性。在試樣某一部分移動視場，集中測量會產生不良的代表性。所謂“代表性”即意味著試樣所有的部分對結果都有貢獻，而不是帶有推測地挑選平均晶粒度的視場。 注：不帶有偏見的檢驗者進行測定時，看著挑選視場，或者排除極端值，這樣做，可能不是有意偽造平均值，但對于整體結果，可能得出高精度的錯覺。選取有代表性的試樣，可在心里將試樣劃分為幾個相等的互相連接的小區域，載物臺預先放置在每個小區域大約中心處。連續地將載物臺放置到每一個這樣的位置，盲目地施加測量網格，即關掉光源、關閉視頻或將眼睛移開，放置測量網格。放好位置不允許再觸碰。只有按照這樣方式選擇視場，進行測量才是有效的，檢驗結果才能不帶有偏見，滿足精度的要求。 6取樣 6.1 測定晶粒度用的試樣應在交貨狀態材料上切取。取樣部位與數量按產品標準或技術條件規定。如果產品標準或技術條件未規定，則在鋼材半徑或邊長1/2處截取。推薦試樣尺寸為10 mm×10 mm。 6.2切取試樣應避開因剪切、加熱影響的區域。不能使用有改變晶粒結構的方法切取試樣。 7試樣制備 7.1 有加工變形晶粒的試樣檢驗平行于加工方向的檢驗面(縱截面)，必要時還應檢驗垂直于加工方向的檢驗面(橫截面)。等軸晶粒可以隨機選取檢驗面。 7.2檢驗鐵素體鋼的奧氏體晶粒度，需要對試樣進行熱處理(見附錄A)，具體方法按產品標準或技術條件的規定。如果產品標準或技術條件未規定，滲碳鋼采用滲碳法，其他鋼可以采用直接淬硬法或者氧化法。檢驗鐵素體晶粒度和奧氏體鋼晶粒度，一般試樣不需要熱處理。 7.3 晶粒度試樣不允許重復熱處理。 7.4用于滲碳處理的試樣應去除脫碳層和氧化皮。 7.5試樣的磨拋和浸蝕按GB/T 13298規定執行。試樣的浸蝕應使大部分晶界完全顯示出來(見附錄A)。 8測定方法 8.1 比較法 8.1.1 一般要求 8.1.1.1 比較法是通過與標準評級圖對比來評定平均晶粒度。適用于評定具有等軸晶粒的再結晶材料。 8.1.1.2本標準有下列四個系列標準評級圖： a)評級圖I：無孿晶晶粒(淺腐蝕)100倍； b)評級圖Ⅱ：有孿晶晶粒(淺腐蝕)100倍； c)評級圖Ⅲ：有孿晶晶粒(深腐蝕)75倍； d)評級圖Ⅳ：鋼中奧氏體晶粒(滲碳法)100倍。 8.1.1.3表2給出常用材料推薦使用的標準評級圖片。 表2 常用材料推薦使用的標準評級圖片 標準評級圖 適用范圍 圖I 1)鐵素體鋼的奧氏體晶粒即采用氧化法、直接淬硬法、鐵素體網法及其他方法顯示的奧氏體晶粒； 2)鐵素體鋼的鐵素體晶粒； 3)鋁、鎂和鎂合金、鋅和鋅合金、高強合金 圖Ⅱ 1)奧氏體鋼的奧氏體晶粒(帶孿晶的)； 2)不銹鋼的奧氏體晶粒(帶孿晶的)； 3)鎂和鎂合金、鎳和鎳合金、鋅和鋅合金、高強合金 圖Ⅲ 銅和銅合金 圖Ⅳ 1)滲碳鋼的奧氏體晶粒； 2)滲碳體網顯示的晶粒； 3)奧氏體鋼的奧氏體晶粒(無孿晶的) 8.1.1.4觀測者需要正確的判斷需要選擇所使用的放大倍數、合適的檢驗面的尺寸(晶粒數)、試樣代表性截面的數量與位置和測定特征或平均晶粒度用的視場。不能憑視覺選擇出似乎是平均晶粒度的區域評定。推薦按5.10選取視場。 8.1.1.5晶粒度的評定應在試樣截面上隨機選取三個或三個以上的代表性視場測量平均晶粒度，以最能代表試樣晶粒大小分布的級數報出。 8.1.1.6若試樣中發現晶粒不均勻現象，經全面觀察后，如屬偶然或個別現象，可不予計算。如較為普遍，則應計算出不同級別晶粒在視場中各占面積百分比。若占優勢晶粒所占的面積不少于視場面積的90％，則只記錄此一種晶粒的級別數。否則，應用不同級別數來表示該試樣的晶粒度，其中第一個級別數代表占優勢的晶粒的級別。出現雙重晶粒度，按GB/T 24177評定，出現個別粗大晶粒可以按照YB/T 4290評定。 8.1.1.7使用比較法時，如需復驗，可改變放大倍數，以克服初驗結果可能帶有的主觀偏見。 8.1.2顯微晶粒度的評定 8.1.2.1 通常使用與相應標準系列評級圖相同的放大倍數，直接進行對比。通過有代表性視場的晶粒組織圖像或顯微照片與相應表2的系列評級圖或標準評級圖復制透明軟片比較，選取與檢測圖像最接近的標準評級圖級別數或晶粒直徑，記錄評定結果。介于兩個整數級別標準圖片之間，以兩個圖片級別的平均值記錄。 8.1.2.2如將檢測的晶粒圖像與標準系列評級圖投影到同一熒屏上，可提高評級精確度。 8。1.2.3 當待測晶粒度超過標準系列評級圖片所包括的范圍，或基準放大倍數(75倍或100倍)不能滿足需要時，可采用其他的放大倍數，通過表3、表4或按8.1.2.4給出的式(3)進行換算處理。通常，所選用的放大倍數是基準放大倍數的簡單整數倍。 8.1.2.4若采用其他放大倍數M進行比較評定，將放大倍數M的待測晶粒圖像與基準放大倍數Mb(75倍或100倍)的系列評級圖片比較，評出的晶粒度級別數G′，其顯微晶粒度級別數G為： G=G′+Q …………………………(3) 式中： Q=6.643 9 lg(M/Mb)，保留0.5單位。 8.1.2.5在晶粒度圖譜中，最粗的一端即00級一個視場中只有幾個晶粒，在最細的一端晶粒的尺寸非常小，準確評定級別很困難。當試樣的晶粒尺寸落在圖譜的兩端時，可以變換放大倍數使晶粒尺寸落在靠近圖譜中間的位置。 表3 評級圖Ⅲ在不同放大倍數下測定的顯微晶粒度的關系 放大 倍數 評級圖Ⅲ圖片編號 (75倍) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 25 0.015 (9.2) 0.030 (7.2) 0.045 (6.0) 0.060 (5.2) 0.075 (4.5) 0.105 (3.6) 0.135 (2.8) 0.150 (2.5) 0.180 (2.0) 0.210 (1.6) 0.270 (0.8) 0.360 (0) 0.451 (0/00) 0.600 (00+) 50 0.007 5 (11.2) 0.015 (9.2) 0.022 5 (8.0) 0.030 (7.2) 0.037 5 (6.5) 0.053 (5.6) 0.067 5 (4.8) 0.075 (4.5) 0.090 (4.0) 0.105 (3.6) 0.135 (2.8) 0.180 (2.0) 0.225 (1.4) 0.300 (0.5) 75 0.005 (12.3) 0.010 (10.3) 0.015 (9.2) 0.020 (8.3) 0.025 (7.7) 0.035 (6.7) 0.045 (6.0) 0.050 (5.7) 0.060 (5.2) 0.070 (4.7) 0.090 (4.0) 0.120 (3.2) 0.150 (2.5) 0.200 (1.7) 100 0.003 7 (13.2) 0.007 5 (11.2) 0.011 2 (10.0) 0.015 (9.2) 0.019 (8.5) 0.026 (7.6) 0.034 (6.8) 0.037 5 (6.5) 0.045 (6.0) 0.053 (5.6) 0.067 (4.8) 0.090 (4.0) 0.113 (3.4) 0.150 (2.5) 200 0.001 9 (15.2) 0.003 7 (13.2) 0.005 6 (12.0) 0.007 5 (11.2) 0.009 (10.5) 0.013 (9.6) 0.017 (8.8) 0.019 (8.5) 0.022 5 (8.0) 0.026 (7.6) 0.034 (6.8) 0.045 (6.0) 0.056 (5.4) 0.075 (4.5) 400 — 0.001 9 (15.1) 0.002 8 (14.0) 0.003 8 (13.1) 0.004 7 (12.5) 0.006 7 (11.5) 0.008 4 (10.8) 0.009 (10.5) 0.012 (10.0) 0.013 3 (9.5) 0.016 8 (8.8) 0.022 5 (8.0) 0.028 (7.3) 0.037 5 (6.5) 500 — — 0.002 2 (14.6) 0.003 (13.7) 0.003 75 (13.1) 0.005 25 (12.1) 0.006 7 (11.5) 0.007 5 (11.1) 0.009 (10.6) 0.010 (10.3) 0.013 3 (9.5) 0.018 (8.7) 0.022 5 (8.0) 0.03 (7.1) 注：括號外為晶粒平均直徑d (mm)；括號內為相應的顯微晶粒度級別數。 表4與標準評級圖I、Ⅱ、Ⅳ等同圖像的晶粒度級別數 圖像的 標準評級圖編號(100倍) 放大倍數 No.1 No.2 No.3 No.4 No.5 No.6 No.7 No.8 No.9 No.10 25 -3 -2 -1 0 1 2 3 4 5 6 50 -1 0 1 2 3 4 5 6 7 8 100 1 2 3 4 5 6 7 8 9 10 200 3 4 5 6 7 8 9 10 11 12 400 5 6 7 8 9 10 11 12 13 14 500 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 14.5 800 7 8 9 10 11 12 13 14 15 16 1 000 7.5 8.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 8.1.3宏觀晶粒度的評定 8.1.3.1 對于特別粗大的晶粒使用宏觀晶粒度進行的測定，放大倍數為1倍。直接將準備好的有代表性的晶粒圖像與評級圖I(非孿晶)和圖Ⅱ及圖Ⅲ(孿晶)進行比較評級。由于標準評級圖是在75倍和100倍下制備的，待測宏觀晶粒不可能完全與系列評級圖的級別一致。為此，宏觀晶粒度可用平均晶粒直徑或表5所列的宏觀晶粒度級別數Gm來表示。 8.1.3.2 當晶粒較小時，最好選用稍高的放大倍數M進行宏觀晶粒度的評定。若評出的晶粒度級別數為G′m，其宏觀晶粒度級別數Gm按式(4)計算：