GB/T 41706-2022 PDF in English
GB/T 41706-2022 (GB/T41706-2022, GBT 41706-2022, GBT41706-2022)
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Metallic powders - Test method for determination of non-metallic inclusions in metal powders for powder forging
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Standards related to (historical): GB/T 41706-2022
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GB/T 41706-2022: PDF in English (GBT 41706-2022) GB/T 41706-2022
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.160
CCS H 16
Metallic powders - Test method for determination of non-
metallic inclusions in metal powders for powder forging
(ISO 13947:2011, Metallic powders - Test method for the determination of non-
metallic inclusions in metal powders using a powder-forged specimen, MOD)
ISSUED ON: OCTOBER 12, 2022
IMPLEMENTED ON: OCTOBER 12, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 6
4 Principles ... 6
5 Significance and function ... 7
6 Instruments and equipment ... 8
7 Samples ... 8
8 Test steps ... 9
9 Test report ... 10
10 Precision and deviation ... 10
Metallic powders - Test method for determination of non-
metallic inclusions in metal powders for powder forging
Safety precautions -- This document does not specifically point out all safety issues.
If safety issues are involved, it is also proposed in combination with the usage
situation. It is the responsibility of the user of this document to establish
appropriate safety and health protection measures and to clarify the applicability
of relevant provisions prior to use.
1 Scope
This document specifies a metallographic method for determining the content of non-
metallic inclusions in metallic powders by using powder-forged samples. This
measurement method requires that the powder-forged sample has as little lateral flow
as possible (< 1%) during forging, and requires that the central area of the powder-forged
sample has no visible pores under the magnification of 100×.
This document applies to the detection of non-metallic inclusion content in powder-
forged parts. In parts with a large amount of lateral flow of material, the separation
distance between nearest neighbors needs to be adjusted, or the size of inclusions that
need to be adjusted can be determined through negotiation between relevant parties.
This document does not apply to the determination of the level of non-metallic
inclusions in internal porous forgings. Residual porosity is difficult to distinguish from
inclusions during the magnification in the test. Too much residual porosity makes
inclusion distribution determination difficult.
This document can be applied to the detection of materials containing manganese
sulfide (pre-mixed or pre-alloyed). In order to meet the test of this type of material, the
nearest neighbor separation distance needs to be adjusted from 30 μm to 15 μm.
2 Normative references
The following documents contain the provisions which, through normative reference in
this document, constitute the essential provisions of this document. For the dated
referenced documents, only the versions with the indicated dates are applicable to this
document; for the undated referenced documents, only the latest version (including all
the amendments) is applicable to this document.
ASTM B796 Standard test method for nonmetallic inclusion content of powders
-- The powder used for forming the sample (part) does not meet the requirements
of the quality standard for the content of non-metallic inclusions;
-- The following reactions occur during the processing of the sample (part):
oxidation and/or reduction.
5.4 The use of the nearest neighbor concept will provide a more conservative
assessment of inclusions: usually, their contents are overestimated rather than
underestimated.
6 Instruments and equipment
6.1 Sample preparation equipment: it is used for the preparation of samples for
metallographic testing.
6.2 Metallographic microscope: It can be used for observation and measurement with
a magnification of 100×; the wavelength of light is 544 nm (green filter), the
magnification of the objective lens is 8×~12.5×, and the numerical aperture is 0.16~0.20.
NOTE: The designated optical element is very important as it determines the object features that can be
resolved by the microscope, which is used for assessing inclusion sizes.
7 Samples
7.1 In order to evaluate the non-metallic inclusion content of powders for powder
forging, the powders shall be mixed with appropriate quantities of graphite and
lubricant and pressed to a specified green density. The test method requires as little
lateral flow as possible (< 1%) during forging, so the diameter of the green compact
relative to the diameter of the forging die shall meet this requirement accordingly.
7.2 The metallographic sample shall be removed from the powder-forged sample (part)
for austenitizing and quenching treatment. The heat treatment of the sample can avoid
the smearing effect and scratches caused by the soft inclusions, which is beneficial to
the sample preparation.
7.3 The area of the polished surface of the sample (part) to be inspected shall not be
less than 350 mm2. For small parts, multiple sections are allowed to be inspected to
obtain the required area for measurement.
7.4 The polished surface shall be parallel to the direction of force, that is, the forging
direction, and shall be able to represent the central area of the sample (part).
8 Test steps
8.1 Sample preparation
When polishing samples, it is very important to obtain a clean polished surface and that
the inclusions are not pitted, tailed, or obscured. Therefore, the procedures specified in
ASTM E3 and ASTM E768 shall be followed. An automatic grinding and polishing
program is recommended. Samples are examined in polished condition and must not be
affected by any prior corrosion (if any).
8.2 Determination of non-metallic inclusion content
8.2.1 The measurement area of the surface of the polished sample shall not be less than
350 mm2, measured at a magnification of 100×; the wavelength of light used is 544 nm
(green filter), the magnification of the objective lens is 8×~12.5×, and the numerical
aperture is 0.16~0.20.
8.2.2 Measure the size of inclusions according to the principle of nearest-neighbor
separation.
Two inclusions within a distance of 30 μm (0.03 mm) (within 3 mm at 100×
magnification) are regarded as the same inclusion.
8.2.3 According to the principle of nearest neighbor separation, three inclusions whose
individual size is less than 30 μm and whose distance is less than 30 μm each other are
regarded as an inclusion cluster.
8.2.4 According to the principle of nearest neighbor separation, if the distance between
two inclusions is within 30 μm, then the individual inclusion with a size smaller than
30 μm is regarded as a part of the inclusions larger than 30 μm. An example is shown
in Figure 2.
8.2.5 Detect and record the number of inclusion particles according to the principle of
nearest neighbor separation, and use the maximum Feret diameter to determine the size,
namely:
-- the length that is greater than or equal to 30 μm,
-- the length that is greater than or equal to 100 μm,
-- the length that is greater than or equal to 150 μm.
In addition to using the concept of nearest-neighbor separation to determine the size of
inclusions, the size of individual inclusion particles can also be measured.
8.2.6 If the size of the inclusion is determined separately, the maximum Feret diameter
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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