GB/T 41080-2021Metallographic inspection method for molybdenum and molybdenum alloys (English PDF)
钼及钼合金金相检验方法
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Issued by
SAMR; SAC
Level / Type
National · Recommended
Issue date
December 31, 2021
Implementation date
July 1, 2022
Scope
GB/T 41080-2021 is the English-translated version of 钼及钼合金金相检验方法.
GB/T 41080-2021 describes how to carry out metallographic inspection and grain evaluation of sintered, hot-worked and cold-worked molybdenum and molybdenum alloys.
Samples are ground on progressively finer sandpaper, polished mechanically or electrolytically, etched to reveal the grain boundaries and then observed and photographed under the microscope.
The document lists the reagents, including oxalic acid, sodium hydroxide, potassium ferricyanide and polishing agents, the grinding, electrolytic polishing and microscope equipment, and the sample size, with an inspection surface generally below 300 mm² and a height under 15 mm.
Test data processing covers calculations from the number of grains in the field of view and the intercept point method for non-uniform equiaxed grains. Annex A shows typical microstructures and Annex B gives the molybdenum grain size grading chart. It was issued on 31 December 2021 and has applied since 1 July 2022.
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Document preview — GB/T 41080-2021
National Standard of the People's Republic of China
- ICS
- 77.120.99
- Classification
- H 24
Issued by: State Administration for Market Regulation; Standardization Administration of the PRC
Contents
- Foreword3
- 1 Scope4
- 2 Normative references4
- 3 Terms and definitions4
- 4 Principle4
- 5 Reagents or materials4
- 6 Instruments and equipment5
- 7 Sample5
- 8 Test steps5
- 9 Test data processing6
- 10 Test report8
- Annex A (informative) Typical microstructure types of molybdenum and molybdenum alloys9
- Annex B (normative) Molybdenum grain size grading chart11
1 Scope
This document describes the methods for metallographic inspection and grain evaluation of molybdenum and molybdenum alloy materials.
This document applies to the metallographic inspection of sintered, hot-worked, cold-worked molybdenum and molybdenum alloys.
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 6394, Determination of estimating the average grain size of metal
GB/T 13298, Inspection methods of microstructure for metals
3 Terms and definitions
For the purposes of this document, the terms and definitions defined in GB/T 6394 apply.
4 Principle
The samples are ground and polished to reveal grain boundaries by etching. Observe and photograph under the microscope.
5 Reagents or materials
5.1 Oxalic acid (H2C2O4·2H2O), chemically pure.
5.2 Sodium hydroxide, chemically pure.
5.3 Potassium ferricyanide, chemically pure.
5.4 Metallographic water sandpaper.
5.5 Polishing agent: alumina polishing powder or emery polishing liquid (paste). The particle size range is generally 1.5µm~9µm.
6 Instruments and equipment
6.1 Metallographic grinding and polishing machine.
6.2 Electrolytic polishing machine.
6.3 Metallographic microscope.
7 Sample
The sample shape and size shall be easy to grind in hand. The sample size is generally less than 300mm² with the inspection surface area. The height of the sample shall be less than 15mm. It can be cut when the sample is too large. When the sample is not suitable for holding, it can be inlaid according to the provisions of GB/T 13298.
8 Test steps
8.1 Grinding of samples
Grind the samples sequentially from coarse to fine on sandpaper with different grit sizes.
During the grinding process, it is necessary to continuously rinse with running water.
For each next step of grinding, the grinding inspection needs to be rotated 90° until all the wear scars from the previous step are removed.
8.2 Polishing of samples
Remove wear marks from samples to achieve a mirror finish. There shall be no grinding defects. The polishing method can be mechanical polishing or electrolytic polishing:
a) Mechanical polishing: Polish with polishing compound on a metallographic polishing machine equipped with nylon, fine canvas or wool. Polishing time is 2min~5min;
b) Electrolytic polishing: Use electropolishing machine to polish. The recommended parameters are shown in Table 1.
9 Test data processing
9.2.3 Intercept point method
The intercept point method shall be used for non-uniform equiaxed grains. The intercept point method includes the straight line intercept point method and the circular intercept point method.
The number of intercept points PL on the calculated unit length of each field of view is calculated by formula (3): Where, M - the magnification of the microscope;
Pi - the number of intercept points on the total length, in pieces; L - the total length, in millimeters (mm).
The number of stubs NL per unit length of each field of view is calculated using formula (4): Where, M - the magnification of the microscope;
Ni - the number of stubs on the total length, in pieces; L - the total length, in millimeters (mm).
Calculate the average intercept length value according to formula (5) for each field of view: […]
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This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 15 pages — is available in the English PDF.
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Related Standards
GB/T 13298-2015 — Inspection Methods of Microstructure for Metals
GB/T 6394-2017 — Determination of estimating the average grain size of metal
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