ASTM A480 is a key specification for stainless steel flat-rolled products, including plates, sheets, and strips. One critical aspect of this standard is thickness tolerances, which define the allowable variation in the thickness of stainless steel plates during manufacturing.Thickness tolerances ensure that the stainless steel plates meet the required dimensional accuracy, which affects fit, strength, and performance in final applications.
ASTM A480 Thickness Tolerances
ASTM A480 classifies thickness tolerances for stainless steel plates based on production processes (hot-rolled/cold-rolled) and product types (medium plates/thin plates), as follows:
Cold Rolled Plates
Thickness range: Typically 0.30–3.00 mm (0.012–0.118 inches).
Tolerance standards:
Thickness (mm)
Width ≤ 1000 mm
1000 mm < Width ≤ 1300 mm
1300 mm < Width ≤ 2100 mm
0.30
±0.03
—
—
0.40
±0.04
±0.04
—
1.00
±0.06
±0.06
±0.08
2.00
±0.10
±0.10
±0.11
3.00
±0.13
±0.13
±0.15
Measurement position: Measured at ≥9.52 mm (3/8 inch) from the edge.
Hot Rolled Plates
Thickness range: Typically 4.76–25.4 mm (3/16–1 inch).
Tolerance standards:
Thickness (mm)
Width ≤ 2134 mm
2134 mm < Width ≤ 3048 mm
3048 mm < Width ≤ 3658 mm
4.76
+1.35/-0.25
+1.78/-0.25
+2.29/-0.25
6.35
+1.52/-0.25
+1.91/-0.25
+2.41/-0.25
12.7
+2.29/-0.25
+2.79/-0.25
+3.30/-0.25
Unified negative deviation: For thickness ≤25.4 mm, the negative deviation is fixed at -0.25 mm (0.010 inch).
2.Width and Length Tolerances
Width tolerances:
Cold rolled plates: ±1.0 mm for width ≤1000 mm; ±1.5 mm for width >1000 mm.
Hot rolled plates: +6.35/-0 mm for width ≤2134 mm; +9.52/-0 mm for width >2134 mm. Length tolerances:
Cold rolled plates: ±2.0 mm for length ≤3048 mm; ±3.0 mm for length >3048 mm.
Hot rolled plates: +9.52/-0 mm for length ≤3048 mm; +12.7/-0 mm for length >3048 mm
3.Flatness Tolerances 36-inch rule: When a 36-inch (914 mm) straightedge is placed on the plate surface, the maximum gap shall not exceed the following limits:
Thickness (mm)
Allowable Gap (mm)
< 6.35
≤ 11.11
6.35–12.7
≤ 7.94
≥ 12.7
≤ 6.35
Applicable scope: For plates with width ≥600 mm, and must comply with ASTM A480 Table A2.20.
4.Edge Tolerances
Slit Edge: Edge straightness deviation ≤1.5 mm/m, with no burrs or curls.
Mill Edge: Slight waviness is allowed, but the height ≤3.0 mm, and no more than 2 occurrences per meter length.
5.Negotiation of Special Tolerances
Precision tolerances: Tighter tolerances can be negotiated between suppliers and buyers (e.g., cold rolled plate thickness tolerance can be reduced to ±0.02 mm, which must be clearly specified in the order).
Certification requirements: If third-party testing (e.g., SGS, BV) is required, it must be noted in the order, and tolerances shall comply with EN 10204 3.1/3.2 standards.
6.Implementation Standards and Testing
Compliance: Tolerances must conform to ASTM A480/A480M-25 and referenced standards (e.g., ASTM A240).
Testing methods:
Thickness: Measured with a micrometer at ≥9.52 mm from the edge, with at least 5 measurement points per plate.
Flatness: Tested with a 36-inch straightedge and feeler gauge, with at least 3 measurement points per square meter.
Summary
The ASTM A480 tolerance system balances standardization and flexibility, providing both general tolerance ranges and supporting customized requirements. In practice, the appropriate tolerance level should be selected based on material type (e.g., 316 stainless steel), processing technology (hot-rolled/cold-rolled), and application (e.g., pressure vessels, construction), with traceability ensured through Material Test Certificates (MTC).
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