The original 304J1 (7.5% Ni) steel grade is used instead of 304 (high Ni) as a steel grade for deep processing (DDQ), but the domestically produced 304J1 modified steel grade (6.5% Ni) on the market can only be used as an ordinary 304 replacement Steel grades are generally not recommended for DDQ use. Most of the following content introduces the characteristics of authentic 304J1 (7.5% Ni), and some comparisons with 304J1 modified steel.
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1. Summary
Reduce the amount of nickel and add copper to improve the molding performance.
2. Features
1) Compared with 304, excellent formability (excellent composite formation, deep processing, etc.)
2) Excellent resistance to aging cracking
3) Excellent welding performance;
4) Non-magnetic in solid solution state;
5) The cold-rolled products have good gloss and beautiful appearance.
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3. Scope of application
Vacuum cups, vacuum flasks, second-class tableware, sinks, gas stoves, combustion parts, etc., especially for deep processing purposes.
4. Chemical composition (JIS G 4305-2005) (wt%)
Chemical composition | C | Si | Mn | P | S | Cr | Ni | Cu |
Standard | ￡0.08 | ￡1.70 | ￡3.0 | ￡0.045 | ￡0.030 | 15.0~18.0 | 8.0~9.0 | 1.0~3.0 |
| General | 0.035 | 0.5 | 1.1 | 0.025 | 0.002 | 16.85 | 7.60 | 2.1 |
| Modification | 0.048 | 0.6 | 1.8 | 0.031 | 0.002 | 17.0 | 6.4 | 2.3 |
5. Performance (JIS G 4305-2005)
Distinguish | Mechanical properties | Processing performance | ||||||||
Ys (Mpa) | Ts (Mpa) | El (%) | Hv | CCV | LDR | Er（mm） | Aging cracking limit | |||
304J1 | Standard | ≥ 155 | ≥ 450 | ≥ 40 | ≤ 200 | – | – | – | – | |
| General | 255 | 595 | 60 | 140 | 26.3 | 26.3 | 12.5 | 3.3 | ||
| Modification | 267 | 621 | 55 | 147 | ||||||
| 304 | 290 | 670 | 57 | 175 | 27.0 | 1.98 | 12.8 | 2.6 | ||
6. Physical properties
Density (g/cm3) | Magnetic | Specific heat 250C(J/kg.0C) | Thermal conductivity 1000C(W/m. 0C) | Thermal expansion rate 20~1000C(10-6/0C) |
| 7.93 | None | 500 | 16.3 | 17.3 |
7. Heat treatment
Melting point: 1400~14500C;
Solution treatment: 1010~11500C.
8. Use status
1) Annealing and solid solution state:
No. 1, 2D, 2B, No. 4, HL, BA, Mirror, and various other surface treatment states.
9. Precautions for use
Magnetic phenomenon will appear after cold working;
The surface of 304J1 is relatively rough after deep processing, and the polishing performance is generally worse than that of 304;
The general price of 304J1 modified steel is obviously lower than the previous normal 304JI;
304J1 modified steel grade can replace part of the use of 304, but generally can only be used for relatively low use.