03利用图像自动分析确定金属的夹杂物或者第二相组成的标准做法

2024年2月27日发(作者：汪晴画)

Standard Practice for Determining the Inclusion or Second-Phase

Constituent Content of Metals by Automatic Image Analysis

利用自动图像分析确定金属的夹杂物或第二相组成内容的标准做法

This standard is issued under the fixed designation E1245; the number immediately following the

designation indicates the year of original adoption or, in the case of revision, the year of last

revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (e)

indicates an editorial change since the last revision or reapproval.

本标准发布指定E1245,该号码立即指定显示原始,如出现修订的情况,指定为今年的最后修订版本。一个数字括号内表示,去年reapproval。上标ε(e)的一篇社论指出改变自上次修订或reapproval。

INTRODUCTION

This practice may be used to produce stereological measurements that describe the amount,

number,size, and spacing of the indigenous inclusions (sulfides and oxides) in steels. The method

may also be applied to assess inclusions in other metals or to assess any discrete second-phase

constituent in any material.

1. Scope

1.1 This practice describes a procedure for obtaining stereological measurements that describe basic

characteristics of the morphology of indigenous inclusions in steels and other metals using automatic

image analysis. The practice can be applied to provide such data for any discrete second phase.

NOTE 1—Stereological measurement methods are used in this practiceto assess the average

characteristics of inclusions or other second-phase particles on a longitudinal plane-of-polish. This

information, by itself, does not produce a three-dimensional description of these constituents in

space as deformation processes cause rotation and alignment of these constituents in a preferred

manner. Development of such information requires measurements on three orthogonal planes and is

beyond the scope of this practice.

1.2 This practice specifically addresses the problem of producing stereological data when the features

of the constituents to be measured make attainment of statistically reliable data difficult.

1.3 This practice deals only with the recommended test methods and nothing in it should be construed

as defining or establishing limits of acceptability.

1.4 The measured values are stated in SI units, which are tobe regarded as standard. Equivalent

inch-pound values are in parentheses and may be approximate.

1.5 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 and health practices

and determine the applicability of regulatory limitations prior to use.

2. Referenced Documents

2.1 ASTM Standards:

E 3 Methods of Preparation of Metallographic Specimens

E 7 Terminology Relating to Metallography

E 45 Test Methods for Determining the Inclusion Contentof Steel

E 768 Practice for Preparing and Evaluating Specimens for Automatic Inclusion Assessment of Steel2

3. Terminology

3.1 Definitions:

3.1.1 For definitions of terms used in this practice, see Terminology E 7.

3.2 Symbols:

A¯=the average area of inclusions or particles, μm2.

AA = the area fraction of the inclusion or constituent.

Ai = the area of the detected feature.

AT = the measurement area (field area, mm2).

H T = the total projected length in the hot-working direction of the inclusion or constituent in the

field, μm.

L¯= the average length in the hot-working direction of the inclusion or constituent, μm.

LT = the true length of scan lines, pixel lines, or grid lines (number of lines times the length of the

lines divided by the magnification), mm.

n = the number of fields measured.

N A = the number of inclusions or constituents of a given type per unit area, mm2.

Ni = the number of inclusions or constituent particles or the number of feature interceptions, in

the field.

NL = the number of interceptions of inclusions or constituent particles per unit length (mm) of

scan lines, pixel lines, or grid lines.

PPi = the number of detected picture points.

PPT = the total number of picture points in the field area.

s = the standard deviation.

t = a multiplier related to the number of fields examined and used in conjunction with the

standard deviation of the measurements to determine the 95 % CI

VV = the volume fraction.

X¯= the mean of a measurement.

Xi = an individual measurement.

λ= the mean free path (μm) of the inclusion or constituent type perpendicular to the hotworking

direction.

ΣX = the sum of all of a particular measurement over n fields.

ΣX2 = the sum of all of the squares of a particular measurement over n fields.

95 % CI = the 95 % confidence interval.

% RA = the relative accuracy, %.

4. Summary of Practice

4.1 The indigenous inclusions or second-phase constituents in steels and other metals are viewed with a

light microscope or a scanning electron microscope using a suitably prepared metallographic specimen.

The image is detected using a television-type scanner tube (solid-state or tube camera) and displayed

on a high resolution video monitor. Inclusions are detected and discriminated based on their gray-level

intensity differences compared to each other and the unetched matrix. Measurements are made based

on the nature of the discriminated picture point elements in the image.3 These measurements

are made on each field of view selected. Statistical evaluation of the measurement data is based on the

field-tofield or feature-to-feature variability of the measurements.

5. Significance and Use

5.1 This practice is used to assess the indigenous inclusions or second-phase constituents of metals

using basic stereological procedures performed by automatic image analyzers.

5.2 This practice is not suitable for assessing the exogenous inclusions in steels and other metals.

Because of the sporadic, unpredictable nature of the distribution of exogenous inclusions,

other methods involving complete inspection, for example, ultrasonics, must be used to locate their

presence. The exact nature of the exogenous material can then be determined by sectioning into the

suspect region followed by serial, step-wise grinding to expose the exogenous matter for identification

and individual measurement. Direct size measurement rather than application of stereological methods

is employed.

5.3 Because the characteristics of the indigenous inclusion population vary within a given lot of

material due to the influence of compositional fluctuations, solidification conditions and processing,

the lot must be sampled statistically to assess its inclusion content. The largest lot sampled is the heat

lot but smaller lots, for example, the product of an ingot, within the heat may be sampled as a separate

lot. The sampling of a given lot must be adequate for the lot size and characteristics.

5.4 The practice is suitable for assessment of the indigenous inclusions in any steel (or other metal)

product regardless of its size or shape as long as enough different fields can be measured to obtain

reasonable statistical confidence in the data. Because the specifics of the manufacture of the product do

influence the morphological characteristics of the inclusions, the report should state the relevant

manufacturing details, that is, data regarding the deformation history of the product.

5.5 To compare the inclusion measurement results from different lots of the same or similar types of

steels, or other metals, a standard sampling scheme should be adopted such as described in Practice

E45.

5.6 The test measurement procedures are based on the statistically exact mathematical relationships of

stereology4 for planar surfaces through a three-dimensional object examined using reflected light (see

Note 1).

5.7 The orientation of the sectioning plane relative to the hot-working axis of the product will influence

test results. In general, a longitudinally oriented test specimen surface is employed in order to assess

the degree of elongation of the malleable (that is, deformable) inclusions.

5.8 Oxide inclusion measurements for cast metals, or for wrought sections that are not fully onsolidated,

may be biased by partial or complete detection of fine porosity or micro-shrinkage cavities and are not

recommended. Sulfides can be discriminated from such voids in most instances and such

measurements may be performed.

5.9 Results of such measurements may be used to qualify material for shipment according to agreed

upon guidelines between purchaser and manufacturer, for comparison of different manufacturing

processes or process variations, or to provide data for structure-property-behavior studies.

6. Interferences

6.1 Voids in the metal due to solidification, limited hot ductility, or improper hot working practices

may be detected as oxides because their gray level range is similar to that of oxides.

6.2 Exogenous inclusions, if present on the plane-of-polish, will be detected as oxides and will bias the

measurements of the indigenous oxides. Procedures for handling this situation are given in 12.5.9.

6.3 Improper polishing techniques that leave excessively large scratches on the surface, or create voids

in or around inclusions, or remove part or all of the inclusions, or dissolve water-soluble inclusions, or

create excessive relief will bias the measurement results.

6.4 Dust, pieces of tissue paper, oil or water stains, or other foreign debris on the surface to be xamined

will bias the measurement results.

6.5 If the programming of the movement of the automatic stage is improper so that the specimen moves

out from under the objective causing detection of the mount or air (un-mounted specimen),easurements

will be biased.

6.6 Vibrations must be eliminated if they cause motion in the image.

6.7 Dust in the microscope or camera system may produce spurious indications that may be detected as

inclusions. Consequently, the imaging system must be kept clean.

7. Apparatus

7.1 A reflected light microscope equipped with bright-field objectives of suitable magnifications is

used to image the microstructure. The use of upright-type microscope allows for easier stage control

when selecting field areas; however, the specimens will require leveling which can create artifacts,

such as scratches, dust remnants and staining, on the polished surface (see 12.2.1). The use of inverted

microscopes usually result in a more consistent focus between fields, thereby, requiring less focussing

between fields and a more rapid completion of the procedure. A scanning electron microscope

also may be used to image the structure.

7.2 A programmable automatic stage to control movement in the x and y directions without operator

attention is recommended (but not mandatory) to prevent bias in field selection and to minimize

operator fatigue.

7.3 An automatic focus device may also be employed if found to be reliable. Such devices may be

unreliable when testing steels or metals with very low inclusion contents.

7.4 An automatic image analyzer with a camera of adequate sensitivity is employed to detect the

inclusions, perform discrimination, and make measurements.

7.5 A computer is used to store and analyze the measurement data.

7.6 A printer is used to output the data and relevant identification/background information in a

convenient format.

7.7 This equipment must be housed in a location relatively free of airborne dust. High humidity must

be avoided as staining may occur; very low humidity must also be avoided as static electricity may

damage electronic components. Vibrations, if excessive, must be isolated.

8. Sampling

8.1 In general, sampling procedures for heat lots or for product lots representing material from a

portion of a heat lot are the same as described in Practice E 45 (Microscopical Methods) or as defined

by agreements between manufacturers and users.

8.2 Characterization of the inclusions in a given heat lot, or a subunit of the heat lot, improves as the

number of specimens tested increases. Testing of billet samples from the extreme top and bottom of the

ingots (after discards are taken) will define worst conditions of oxides and sulfides. Specimens taken

from interior billet locations will be more representative of the bulk of the material. Additionally, the

inclusion content will vary with the ingot pouring sequence and sampling should test at least the first,

middle and last ingot teemed. The same trends are observed in continuously cast steels. Sampling

schemes must be guided by sound engineering judgment, the specific processing parameters, and

producer-purchaser agreements.

9. Test Specimens

9.1 In general, test specimen orientation within the test lot is the same as described in Practice E 45

(Microscopical Methods). The plane-of-polish should be parallel to the hot-working axis and, most

commonly, taken at the quarter-thickness location. Other test locations may also be sampled, for

example, subsurface and center locations, as desired or required.

9.2 The surface to be polished should be large enough in area to permit measurement of at least 100

fields at the necessary magnification. Larger surface areas are beneficial whenever the product form

permits. A minimum polished surface area of 160 mm2

(0.25 in.2) is preferred.

9.3 Thin product forms can be sampled by placing a number of longitudinally oriented pieces in the

mount so that the sampling area is sufficient.

9.4 Practice E 768 lists two accepted methods for preparing steel samples for the examination of

inclusion content using image analysis. The standard also lists a procedure to test the quality of the

preparation using differential interference contrast (DIC).

10. Specimen Preparation

10.1 Metallographic specimen preparation must be carefully controlled to produce acceptable quality

surfaces for image analysis. Guidelines and recommended practices are given in Methods E 3, and

Practices E 45 and E 768.

10.2 The polishing procedure must not alter the true appearance of the inclusions on the plane-of-polish

by producing excessive relief, pitting, cracking or pullout. Minor fine scratches, such as from a 1-μm

diamond abrasive, do not usually interfere with inclusion detection but heavier scratches are to be

avoided. Proper cleaning of the specimen is necessary. Use of automatic grinding and polishing devices

is recommended.

10.3 Establishment of polishing practices should be guided by Practice E 768.

10.4 Inclusion retention is generally easier to accomplish if specimens are hardened. If inclusion

retention is inadequate with annealed, normalized, or low hardness as-rolled specimens, they should be

subjected to a standard heat treatment (hardening) cycle, appropriate for the grade. Because inclusion

retention and cracking at carbides may be a problem for certain steels in the as-quenched condition,

tempering is recommended; generally, a low tempering temperature, for example, 200–260°C

(400–500°F), is adequate.

10.5 Mounting of specimens is not always required depending on their size and shape and the available

equipment; or, if hand polishing is utilized for bulk specimens of convenient size and shape.

10.6 The polished surface area for mounted specimens should be somewhat greater than the area

required for measurement to avoid edge interferences. Unmounted specimens generally should have a

surface area much greater than required for measurement to facilitate leveling using the procedure

described in 12.1.1.

10.7 Etching of specimens is not desired for inclusion assessment.