GJB 935A-2021
Specification for 45Mn17Al3 low magnetic steel sections (English Version)
- Standard No.
- GJB 935A-2021
- Language
- Chinese, Available in English version
- Release Date
- 2021
- Published By
- Military Standard of the People's Republic of China-General Armament Department
- Latest
- GJB 935A-2021
- Introduction
Analysis of Standard Technology Evolution
Technical Indicators GJB 935-1990 GJB 935A-2021 Impact of Changes Phosphorus and Sulfur Content P≤0.030%, S≤0.025% P≤0.025%, S≤0.020% Improve Steel Purity Delivery Status Hot Rolled Only Add Hot Extrusion Status Expand Processing Technology Adaptability Magnetic permeability test Remanent magnetism data must be provided Remanent magnetism requirement can be cancelled Simplify the testing process
Analysis of core technical requirements
Chemical composition control
The melting composition requirements of 45Mn17Al3 steel are: Mn content 16.00-18.00%, Al content 2.40-3.60%, the manganese content in the finished product can fluctuate within ±0.15%, and the aluminum content can have a negative deviation of 0.20%.
Mechanical properties
- Tensile strength ≥600MPa
- Specified plastic extension strength 300-450MPa
- Elongation after fracture ≥25%
Magnetic properties requirements
Under three magnetic field intensities of 4000A/m, 8000A/m and 16000A/m, the relative magnetic permeability μr is ≤1.2, and the test method specified in GJB 937 is adopted.
Implementation and application suggestions
Material selection plan for ship degaussing equipment
No. 10 bulb flat steel (cross-sectional area 8.67cm2) is recommended for the main load-bearing structure. Its XX-axis moment of inertia reaches 84.08cm?, and its density of 7.66g/cm3 can optimize the magnetic shielding effectiveness.
Key points of quality control
- Arc furnace smelting requires supporting LF refining equipment
- Hot extrusion process temperature is controlled at 1050±20℃
- Demagnetization treatment is required before magnetic permeability testing
Standard reference system
Test items Reference standards Key clauses Chemical composition analysis GB/T 223 series Manganese content potentiometric titration method Mechanical properties test GB/T 228.1-2010 R4 Sample Preparation Requirements Magnetic Property Testing GJB 937 Weak Magnetic Material Measurement Method
GJB 935A-2021 history
- 2021 GJB 935A-2021 Specification for 45Mn17Al3 low magnetic steel sections
- 1990 GJB 935-1990 45Mn17Al3 low magnetic steel section