CB/T 1209-1992: Metallographic Testing Standard for 0Cr17Ni4Cu4Nb (17-4PH) Stainless Steel
CB/T 1209-1992: Metallographic Testing Standard for 0Cr17Ni4Cu4Nb (17-4PH) Martensitic Precipitation Hardening Stainless Steel
This article provides a comprehensive translation and overview of the Chinese Shipbuilding Industry Standard CB/T 1209-1992, which specifies the metallographic testing requirements for 0Cr17Ni4Cu4Nb (17-4PH) martensitic precipitation hardening stainless steel — a material commonly used in marine engineering, flange manufacturing, and high-performance applications.
Standard Information:
- Standard Number: CB/T 1209-1992
- Approval Date: July 4, 1992
- Implementation Date: March 1, 1993
- Issuing Authority: China State Shipbuilding Corporation (CSSC)
1. Subject and Scope
This standard specifies the basic requirements for metallographic testing of 0Cr17Ni4Cu4Nb martensitic precipitation hardening stainless steel, including:
- Metallographic microstructure examination
- Grain size grading and evaluation methods
- δ-ferrite content evaluation
This standard applies to the inspection of microstructural state, grain size grade, and δ-ferrite content of 0Cr17Ni4Cu4Nb martensitic precipitation hardening stainless steel.
2. Referenced Standards
- GB 6394 — Metal Average Grain Size Determination Method
3. Designations
| Designation | Description |
|---|---|
| TS1 | Annealed condition |
| TS2 | Hot-rolled condition |
| TS3 | Solution-treated condition |
| TS4 | Aged condition |
| G | Grain size |
| F | δ-ferrite |
4. Metallographic Sampling and Result Reporting
4.1 Sampling
Metallographic test specimens shall be taken from actual parts or from test bars of the same material and heat-treated together with the parts.
- For δ-ferrite content measurement: the test surface shall be parallel to the rolling direction.
- For microstructural state and grain size evaluation: the test surface shall be perpendicular to the rolling direction.
4.2 Result Reporting
- 4.2.1 If the evaluation result matches a reference grade chart, the result is expressed by that grade level, e.g., G1, G2, etc.
- 4.2.2 If the result falls between two grades, it is expressed as both grades, e.g., F2/3, F3/4. The dominant grade is indicated by a short underline below its number — e.g., F2/3 means the δ-ferrite content falls between Grade 2 and Grade 3, with Grade 2 being dominant.
5. Evaluation Methods
5.1 Microstructure Examination
Microstructure examination is performed on the polished and etched (or electrolytically etched) specimen surface. Recommended etching reagents are listed in Appendix A (reference). Magnification: 400×. The observed field of view should be representative of the entire specimen’s microstructure.
5.2 Grain Size Evaluation
Grain size evaluation is performed on the polished and etched specimen surface.
5.2.1 Comparison Method
When using the comparison method to evaluate grain size grade, the prepared specimen is examined at 100× or 400× magnification. Select a representative field of view and compare it with the reference grain size charts (Section 6.2). The closest matching grade is assigned as the specimen’s grain size grade.
If the grain size exceeds the standard’s grading range, observe at an appropriate magnification and then convert to the standard grain size grade.
At least 5 fields of view shall be evaluated, and the grade of the majority of fields shall be used. Individual fields that differ significantly shall be noted separately.
5.2.2 Direct Measurement Method
The direct measurement method for grain size shall follow the procedures and requirements described in GB 6394.
5.3 δ-Ferrite Content Evaluation
- 5.3.1 The δ-ferrite content is expressed as the percentage of the total area of δ-ferrite phase within the field of view relative to the entire field of view area.
- 5.3.2 Evaluation is performed on the polished and etched specimen surface at 100× magnification. δ-ferrite appears as strip-like distributions along the rolling direction. Select a representative field of view and compare with the reference charts (Section 6.3).
- 5.3.3 At least 5 fields of view shall be evaluated, and the arithmetic mean shall be taken.
6. Metallographic Evaluation Grade Charts
6.1 Microstructural State Evaluation
0Cr17Ni4Cu4Nb martensitic precipitation hardening stainless steel typically exhibits four microstructural states, as listed below:
| State Code | Condition | Magnification |
|---|---|---|
| TS1 | Annealed | 400× |
| TS2 | Hot-rolled | 400× |
| TS3 | Solution-treated | 400× |
| TS4 | Aged | 400× |
Abnormal structures:
- Figure 5: Burned (overheated) structure — characterized by δ-ferrite precipitating along grain boundaries.
- Figure 6: Severely burned (severely overheated) structure — similar characteristic but more pronounced.
6.2 Grain Size Evaluation Charts
Grain size is divided into 8 grades (G1–G8). Evaluation charts are provided at both 100× and 400× magnification (Figures 7–14).
6.3 δ-Ferrite Content Evaluation Charts
δ-ferrite content is divided into 7 grades (F1–F7), representing the percentage of δ-ferrite phase area. Evaluation charts are provided at 100× magnification (Figures 15–21).
Original Standard Document (PDF)
The original Chinese standard document can be downloaded below:
📄 Download Original PDF: CB/T 1209-1992 (17-4PH Metallographic Testing Standard)
Summary
The CB/T 1209-1992 standard provides a comprehensive framework for the metallographic quality assessment of 17-4PH stainless steel — a critical material in marine, flange, and high-performance engineering applications. Understanding and properly applying these evaluation methods ensures material quality and structural integrity in critical service environments.
This translation is provided for reference purposes. For official and authoritative interpretation, please refer to the original Chinese standard document published by China State Shipbuilding Corporation.
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