Technical Specification · Free Download

304 / 304L Stainless Steel

Comprehensive technical specification for 304 and 304L austenitic stainless steel, covering Canadian stock sizes, tolerances, machinability, common defects, and handling guidelines for fabrication, woodworking, and machining operations.

Material Overview & Common Uses

304 / 304L is the most widely used austenitic stainless steel, offering excellent corrosion resistance, formability, and weldability. The low-carbon variant (304L) minimizes carbide precipitation during welding, making it preferred for heavy-gauge welded assemblies. Common applications in Canadian fabrication include food processing equipment, kitchen counters, chemical storage tanks, architectural cladding, heat exchangers, and structural components in mildly corrosive environments. It is non-magnetic in the annealed condition but may become slightly magnetic after cold working.

Core Technical Properties & Sizing

Parameter	Value / Specification
Chemical Composition (wt%)	18.0–20.0 Cr, 8.0–10.5 Ni, ≤0.08 C (304) / ≤0.03 C (304L), ≤2.0 Mn, ≤1.0 Si, ≤0.045 P, ≤0.03 S, balance Fe.
Mechanical Properties (annealed)	Tensile strength ≥ 515 MPa (75 ksi), Yield strength ≥ 205 MPa (30 ksi), Elongation ≥ 40% in 2 in.
Hardness	Rockwell B ≤ 92 (typical 70–90 HRB).
Density	8.00 g/cm³ (0.289 lb/in³).
Thermal Conductivity	16.2 W/m·K at 100°C.
Modulus of Elasticity	193 GPa (28 × 10⁶ psi).
Standard Sheet/Plate Sizes (Imperial)	48 in × 96 in (4×8 ft), 48 in × 120 in (4×10 ft), 60 in × 120 in (5×10 ft). Thicknesses: 16 ga (0.060 in / 1.52 mm), 14 ga (0.075 in / 1.90 mm), 12 ga (0.105 in / 2.67 mm), 10 ga (0.135 in / 3.43 mm), 3/16 in (4.76 mm), 1/4 in (6.35 mm).
Standard Bar/Rod Sizes (Round)	1/4 in to 6 in diameter, 12 ft or 20 ft lengths. Hex: 3/8 in to 2 in across flats. Square: 1/4 in to 4 in.
Tolerances (ASTM A240 Sheet/Plate)	Thickness ±0.005 in for ≤0.060 in, ±0.007 in for 0.061–0.125 in, ±0.009 in for 0.126–0.187 in. Flatness: ≤1/4 in in 48 in for annealed sheet. Width/Length: +1/4 in, -0 in for sheared edges; +1/2 in, -0 in for plasma cut.
Surface Finishes	2B (cold rolled, bright), No. 4 (brushed), BA (bright annealed), #8 (mirror), 2D (dull cold rolled).

Machinability, Tooling & Feeds

Parameter	Recommendation / Value
Machinability Rating	~45% of free-machining 1212 steel.
Tooling Material	Sharp, positive-rake carbide inserts (C2 or C3 grade) with chip breakers.
Cutting Speed (Turning) – Carbide	150–250 SFM (45–75 m/min).
Cutting Speed (Turning) – HSS	80–120 SFM (24–36 m/min).
Feeds – Finishing	0.005–0.015 in/rev (0.13–0.38 mm/rev).
Feeds – Roughing	0.015–0.030 in/rev (0.38–0.76 mm/rev).
Depth of Cut – Finishing	0.020–0.100 in (0.5–2.5 mm).
Depth of Cut – Roughing	Up to 0.250 in (6.35 mm).
Coolant	Use generous water-soluble oil or synthetic coolant to control heat and work hardening.
Drilling	135° split-point HSS or carbide drills, peck cycle recommended.
Tapping	Spiral-point or spiral-flute taps with high lubricity (e.g., molybdenum disulfide paste).
Sawing (Solid Bars)	Bimetal blades with 4–6 teeth per inch, running at 80–120 SFM (24–36 m/min) with moderate feed pressure.

Common Defects & Quality Control

Defect / Issue	Description / Mitigation
Surface Scratches / Die Marks	Minimize with protective film and clean work surfaces during handling and forming.
Heat Tint / Oxide Scale (Welding)	Must be removed by pickling, passivation, or mechanical abrasion to restore corrosion resistance.
Work Hardening Cracks (Forming)	Avoid sharp radii. Minimum bend radius ~1T for sheet. Maintain constant feed during machining.
Pitting Corrosion (Chlorides)	Ensure proper passivation and avoid carbon steel contamination.
Weld Decay (Intergranular Corrosion)	Mitigated by using 304L or post-weld annealing.
Dimensional Distortion (Welding)	Use proper fixturing and heat input control.
Lamination / Inclusion Streaks (Plate)	Detectable by ultrasonic testing.
Orange Peel Surface (Forming)	Reduce strain or use finer grain material.
Quality Control Checks	Verify mill certificate (ASTM A240/A276), check thickness with micrometer (3 points per sheet), confirm flatness on granite table, perform spark test or PMI for grade verification, and inspect surface finish with comparator plates.

Storage, Handling & Racking Guidelines

Guideline	Detail
Environment	Store indoors in a dry, climate-controlled environment (relative humidity <60%) to prevent surface staining.
Contamination Prevention	Keep away from carbon steel storage areas to avoid iron contamination. Use dedicated stainless steel racks or line carbon steel racks with wood, rubber, or plastic.
Sheet Storage	Store vertically in A-frame racks with padded supports to prevent scratching.
Plate Storage	Stack flat with interleaving paper or plastic film between layers.
Bar/Rod Storage	Store horizontally on racks with adequate support to prevent sagging.
Handling	Handle with clean, dry gloves. Use suction lifters or padded clamps for moving large sheets. Avoid dragging sheets across each other.
Long-Term Storage	Apply a light oil or protective wax coating.
Incoming Inspection	Inspect for damage and contamination. Reject material with rust spots, embedded iron, or deep scratches.
Inventory Rotation	Rotate stock FIFO to avoid age-related surface degradation.