JIS G4304 Stainless Steel Plates: Full Specification
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1. Scope of JIS G4304
JIS G4304 is the Japanese Industrial Standard for hot-rolled stainless steel plates, sheets and strip for general and pressure vessel applications. The current edition, JIS G4304:2021, specifies manufacturing processes, dimensional tolerances, mechanical properties and chemical compositions for more than 60 grades across the austenitic (SUS304, SUS316L, SUS321, SUS310S), ferritic (SUS430) and martensitic (SUS410, SUS420) families. The applicable thickness range is 3.0 mm to 140 mm, and the standard is adopted from ISO 16143-1 with national modifications.
Typical supply dimensions from stock: coil thickness 1.5-15 mm with widths of 1000, 1219, 1500, 1800 and 2000 mm; plate thickness 2-35 mm with widths of 1000, 1219, 1500 and 1524 mm and lengths of 2000, 2348, 3000, 3048, 4000 and 6000 mm.
2. Chemical Composition and Mechanical Properties
| Grade | C (%) | Si (%) | Mn (%) | P (%) | S (%) | Ni (%) | Cr (%) | Mo (%) | N (%) |
|---|---|---|---|---|---|---|---|---|---|
| SUS304 | 0.08 max | 1.00 max | 2.00 max | 0.045 max | 0.030 max | 8.00-10.50 | 18.00-20.00 | - | 0.10 max |
| SUS304L | 0.030 max | 1.00 max | 2.00 max | 0.045 max | 0.030 max | 9.00-13.00 | 18.00-20.00 | - | 0.10 max |
| SUS316 | 0.08 max | 1.00 max | 2.00 max | 0.045 max | 0.030 max | 10.00-14.00 | 16.00-18.00 | 2.00-3.00 | 0.10 max |
| SUS316L | 0.030 max | 1.00 max | 2.00 max | 0.045 max | 0.030 max | 12.00-15.00 | 16.00-18.00 | 2.00-3.00 | 0.10 max |
| SUS321 | 0.08 max | 1.00 max | 2.00 max | 0.045 max | 0.030 max | 9.00-13.00 | 17.00-19.00 | - | 0.10 max |
| SUS310S | 0.08 max | 1.50 max | 2.00 max | 0.045 max | 0.030 max | 19.00-22.00 | 24.00-26.00 | - | 0.25 max |
| SUS430 | 0.12 max | 0.75 max | 1.00 max | 0.040 max | 0.030 max | 0.60 max | 16.00-18.00 | - | - |
| SUS410 | 0.15 max | 1.00 max | 1.00 max | 0.040 max | 0.030 max | 0.60 max | 11.50-13.50 | - | - |
| Grade | Tensile strength (MPa) | Yield strength (MPa, min) | Elongation (%, min) | Hardness (HB, max) |
|---|---|---|---|---|
| SUS304 | 520 min | 205 | 40 | 187 |
| SUS304L | 480 min | 175 | 40 | 187 |
| SUS316 | 520 min | 205 | 40 | 187 |
| SUS316L | 480 min | 175 | 40 | 187 |
| SUS321 | 520 min | 205 | 40 | 187 |
| SUS310S | 520 min | 205 | 40 | 217 |
| SUS430 | 450 min | 205 | 22 | 183 |
| SUS410 (annealed) | 440 min | 205 | 20 | 183 |
3. Dimensional Tolerances and Surface Finishes
Thickness tolerance (plates, mm)
| Nominal thickness | Tolerance |
|---|---|
| 3.0 to under 5.0 | +/-0.30 |
| 5.0 to under 8.0 | +/-0.40 |
| 8.0 to under 12.0 | +/-0.50 |
| 12.0 to under 20.0 | +/-0.60 |
| 20.0 to under 40.0 | +/-0.80 |
| 40.0 to under 60.0 | +/-1.00 |
| 60.0 to under 100.0 | +/-1.30 |
| 100.0 to 150.0 | +/-1.60 |
Width tolerance (mm)
| Nominal width | Tolerance |
|---|---|
| Up to 1000 | +5 / 0 |
| Over 1000 to 1500 | +6 / 0 |
| Over 1500 to 2000 | +8 / 0 |
| Over 2000 | +10 / 0 |
JIS G4304 surface designations for hot-rolled product include: No.1 (hot rolled, heat treated, pickled or similar), No.3 (ground to F100-F120 per JIS R6001), No.4 (ground to F150-F180), and the 240#, 320# and 400# ground finishes. Specify the finish on the order; pickling is the standard finish for corrosion service, while ground finishes are for architectural and forming applications.
4. JIS G4304 vs JIS G4305 and Sourcing Guidance
The difference is the manufacturing route: JIS G4304 covers hot-rolled plates, sheets and strip, while JIS G4305 covers cold-rolled product. Cold-rolled plate offers tighter thickness tolerances, smoother surfaces and generally higher tensile strength from the final cold pass, but costs more. For pressure vessels and heavy fabrication, hot-rolled G4304 plate is the norm; for precision sheets, stamped parts and mirror-finish panels, G4305 applies.
For Japanese and Southeast Asian projects, order plate to JIS G4304:2021 with the grade, thickness, width, length and surface finish stated. Require the original JIS chemical and mechanical test report with the heat number, and for critical projects add third-party verification and full PMI inspection before shipment. Custom cutting, surface grinding and export wooden-frame packaging are standard value-added services for plate supplied to this specification.
5. FAQ
What thickness range does JIS G4304 cover?
Hot-rolled plate, sheet and strip from 3.0 mm to 140 mm thickness. Below 3.0 mm, cold-rolled product per JIS G4305 is the applicable specification.
What is the difference between SUS304 and SUS304L in JIS G4304?
SUS304L limits carbon to 0.030% maximum, which prevents sensitization during welding. Both grades have the same tensile requirement in the L version at 480 MPa minimum, versus 520 MPa for standard SUS304.
Is JIS G4304 equivalent to ASTM A240?
The two standards cover similar plate products, and SUS304 corresponds broadly to A240 304, but the test methods, tolerance tables and property requirements differ. For export to Japan or Southeast Asia, specify JIS G4304; for US pressure vessel code work, specify ASTM/ASME A240/SA240.
What surface finish should I choose for SUS304 plate?
For corrosion service, No.1 (pickled) is standard. For forming and architectural use, No.3 or No.4 ground finishes are common. Specify the finish explicitly; it affects both price and delivery time.
Does JIS G4304 require mill test certificates?
Yes, the supplier should provide the chemical and mechanical test report per JIS, including heat number and results. Third-party inspection (for example by SGS) and PMI verification are recommended for project-critical lots.
