GB/T 38786-2020 English PDF (GB/T38786-2020)

GB/T 38786-2020: Testing method for cleanliness of magnesium and magnesium alloy ingots
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GB/T 38786-2020
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.99
H 21
Testing method for cleanliness of magnesium and
magnesium alloy ingots
(ISO 16374:2016, Evaluation method for cleanliness of magnesium
and magnesium alloy ingots, MOD)
ISSUED ON: JUNE 02, 2020
IMPLEMENTED ON: APRIL 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 5 
2 Normative references ... 5 
3 Appearance inspection ... 5 
4 Chemical composition ... 6 
5 Cleanliness testing ... 6 
6 Test report ... 9 
Annex A (informative) Comparison on chapter number between this Standard
and ISO 16374:2016 ... 10 
Annex B (informative) Technical differences between this Standard and ISO
16374:2016 and their reasons ... 11 
Annex C (informative) Assessment criteria for cleanliness of magnesium and
magnesium alloy ingots ... 14 
Testing method for cleanliness of magnesium and
magnesium alloy ingots
1 Scope
This Standard specifies appearance inspection, chemical composition,
cleanliness testing and test report for magnesium and magnesium alloy ingots.
This Standard is applicable to cleanliness testing of magnesium and
magnesium alloy ingots.
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 3499, Magnesium ingots
GB/T 5153, Designation and composition of wrought magnesium and
magnesium alloys
GB/T 8170, Rules of rounding off for numerical values and expression and
judgement of limiting values
GB/T 19078, Magnesium alloys ingots for castings
ISO 2470-1, Paper, board and pulps - Measurement of diffuse blue
reflectance factor - Part 1: Indoor daylight conditions (ISO brightness)
ISO 8287, Magnesium and magnesium alloys - Unalloyed magnesium -
Chemical composition
ISO 16220, Magnesium and magnesium alloys - Magnesium alloy ingots and
castings
3 Appearance inspection
Visually inspect the impurities or surface contamination on the surface of
magnesium and magnesium alloy ingots.
4 Chemical composition
The chemical composition of magnesium and magnesium alloy ingots shall
meet the requirements of GB/T 3499, GB/T 5153, GB/T 19078, ISO 8287 and
ISO 16220. Unspecified alloy designations or the composition range of alloying
elements shall be negotiated between the supplier and the purchaser.
5 Cleanliness testing
5.1 Principle of cleanliness testing
The principle of cleanliness testing is based on the provisions on brightness
testing in ISO 2470-1. Diffuse reflection light from a standard testing machine
illuminates the fracture. The beam reflected from the fracture surface, through
a designated glass filter, is measured by a photodetector that responds to
different effective wavelengths OR photodiode array. Then from the
photodetector or from the photodiode array that uses the appropriate weighting
function, directly test the fracture brightness. For the samples prepared with the
same material under standard experimental conditions, use that the brightness
of the fracture surface of the sample measured by the brightness tester is
inversely proportional to the number of defects on the fracture, through the
tested fracture brightness value, to access the cleanliness of materials.
5.2 Equipment
5.2.1 Equipment for sample processing: lathe or milling machine.
5.2.2 Sampling mould: is made of steel or cast iron; no pores, rust and residue
on the surface of the cavity; the shape of the inner cavity shall be cast with a
smooth, uniform surface and a size that meets the requirements of brightness
testing; the mould-taking mould shall adopt the size and shape as shown in
Figure 1; except for the 29.5mm diameter of the neck area (the minimum size
required for testing by the tester), the remaining dimensions can be modified
but it shall ensure the sample feeding.
5.2.3 Fracture tool: a tool to interrupt the brightness testing sample at the neck
area. The tool can be freely designed. But it shall ensure that the sample can
be interrupted at the neck area. The fracture tool shall adopt the shape shown
in Figure 2.
5.2.4 Brightness tester: a brightness tester that can meet the testing
requirements shall be selected, in accordance with the requirements of ISO
2470-1.
5.3.2 Sample preparation: The sample shall be taken directly from the ingot or
molten metal. When the sample is taken directly from the ingot, avoid areas
with casting defects such as holes, porosity, shrinkage holes. When the sample
is taken directly from the molten metal, ensure that the molten metal is poured
into the preheated sampling mould (5.2.2) at a uniform and gentle flow rate.
The preheating temperature of the sampling mould is not less than 150°C. After
the sample is completely solidified, take out the sample.
5.3.3 Number of samples: The number of samples is at least 3, or it is stipulated
in the contract by the supplier and the purchaser.
5.4 Test steps
Use the fracture tool (5.2.3) to break the sample at the neck area. Then
immediately perform the brightness testing of sample fracture on the brightness
tester. The number of measurements depends on the rotation angle, as shown
in Table 1. The brightness value of each sample is the average of the brightness
testing results obtained at various angles.
Table 1 -- Number of measurements corresponding to rotation angles
Number of measurements Rotation angle at each testing
8 0°, 45°, 90°, 135°, 180°, 225°, 270°, 315°
5.5 Test data processing
Fracture brightness value is the average value of fracture brightness values of
all tested samples. It is rounded off according to the numerical rounding rules
specified in GB/T 8170. See Annex C for the assessment of cleanliness of
magnesium and magnesium alloy ingots.
5.6 Others
If it is difficult to obtain full-size samples by machining or casting, agreed
between the supplier and the purchaser, brightness testing can be carried out
by directly breaking the ingot or casting. In this case, the diameter of the neck
fracture shall meet mm and be recorded in the inspection report.
GB/T 38786-2020
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.99
H 21
Testing method for cleanliness of magnesium and
magnesium alloy ingots
(ISO 16374:2016, Evaluation method for cleanliness of magnesium
and magnesium alloy ingots, MOD)
ISSUED ON: JUNE 02, 2020
IMPLEMENTED ON: APRIL 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 5 
2 Normative references ... 5 
3 Appearance inspection ... 5 
4 Chemical composition ... 6 
5 Cleanliness testing ... 6 
6 Test report ... 9 
Annex A (informative) Comparison on chapter number between this Standard
and ISO 16374:2016 ... 10 
Annex B (informative) Technical differences between this Standard and ISO
16374:2016 and their reasons ... 11 
Annex C (informative) Assessment criteria for cleanliness of magnesium and
magnesium alloy ingots ... 14 
Testing method for cleanliness of magnesium and
magnesium alloy ingots
1 Scope
This Standard specifies appearance inspection, chemical composition,
cleanliness testing and test report for magnesium and magnesium alloy ingots.
This Standard is applicable to cleanliness testing of magnesium and
magnesium alloy ingots.
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 3499, Magnesium ingots
GB/T 5153, Designation and composition of wrought magnesium and
magnesium alloys
GB/T 8170, Rules of rounding off for numerical values and expression and
judgement of limiting values
GB/T 19078, Magnesium alloys ingots for castings
ISO 2470-1, Paper, board and pulps - Measurement of diffuse blue
reflectance factor - Part 1: Indoor daylight conditions (ISO brightness)
ISO 8287, Magnesium and magnesium alloys - Unalloyed magnesium -
Chemical composition
ISO 16220, Magnesium and magnesium alloys - Magnesium alloy ingots and
castings
3 Appearance inspection
Visually inspect the impurities or surface contamination on the surface of
magnesium and magnesium alloy ingots.
4 Chemical composition
The chemical composition of magnesium and magnesium alloy ingots shall
meet the requirements of GB/T 3499, GB/T 5153, GB/T 19078, ISO 8287 and
ISO 16220. Unspecified alloy designations or the composition range of alloying
elements shall be negotiated between the supplier and the purchaser.
5 Cleanliness testing
5.1 Principle of cleanliness testing
The principle of cleanliness testing is based on the provisions on brightness
testing in ISO 2470-1. Diffuse reflection light from a standard testing machine
illuminates the fracture. The beam reflected from the fracture surface, through
a designated glass filter, is measured by a photodetector that responds to
different effective wavelengths OR photodiode array. Then from the
photodetector or from the photodiode array that uses the appropriate weighting
function, directly test the fracture brightness. For the samples prepared with the
same material under standard experimental conditions, use that the brightness
of the fracture surface of the sample measured by the brightness tester is
inversely proportional to the number of defects on the fracture, through the
tested fracture brightness value, to access the cleanliness of materials.
5.2 Equipment
5.2.1 Equipment for sample processing: lathe or milling machine.
5.2.2 Sampling mould: is made of steel or cast iron; no pores, rust and residue
on the surface of the cavity; the shape of the inner cavity shall be cast with a
smooth, uniform surface and a size that meets the requirements of brightness
testing; the mould-taking mould shall adopt the size and shape as shown in
Figure 1; except for the 29.5mm diameter of the neck area (the minimum size
required for testing by the tester), the remaining dimensions can be modified
but it shall ensure the sample feeding.
5.2.3 Fracture tool: a tool to interrupt the brightness testing sample at the neck
area. The tool can be freely designed. But it shall ensure that the sample can
be interrupted at the neck area. The fracture tool shall adopt the shape shown
in Figure 2.
5.2.4 Brightness tester: a brightness tester that can meet the testing
requirements shall be selected, in accordance with the requirements of ISO
2470-1.
5.3.2 Sample preparation: The sample shall be taken directly from the ingot or
molten metal. When the sample is taken directly from the ingot, avoid areas
with casting defects such as holes, porosity, shrinkage holes. When the sample
is taken directly from the molten metal, ensure that the molten metal is poured
into the preheated sampling mould (5.2.2) at a uniform and gentle flow rate.
The preheating temperature of the sampling mould is not less than 150°C. After
the sample is completely solidified, take out the sample.
5.3.3 Number of samples: The number of samples is at least 3, or it is stipulated
in the contract by the supplier and the purchaser.
5.4 Test steps
Use the fracture tool (5.2.3) to break the sample at the neck area. Then
immediately perform the brightness testing of sample fracture on the brightness
tester. The number of measurements depends on the rotation angle, as shown
in Table 1. The brightness value of each sample is the average of the brightness
testing results obtained at various angles.
Table 1 -- Number of measurements corresponding to rotation angles
Number of measurements Rotation angle at each testing
8 0°, 45°, 90°, 135°, 180°, 225°, 270°, 315°
5.5 Test data processing
Fracture brightness value is the average value of fracture brightness values of
all tested samples. It is rounded off according to the numerical rounding rules
specified in GB/T 8170. See Annex C for the assessment of cleanliness of
magnesium and magnesium alloy ingots.
5.6 Others
If it is difficult to obtain full-size samples by machining or casting, agreed
between the supplier and the purchaser, brightness testing can be carried out
by directly breaking the ingot or casting. In this case, the diameter of the neck
fracture shall meet mm and be recorded in the inspection report.