430 Ferritic Stainless Steel Technical Material Specification
Comprehensive technical specification for 430 ferritic stainless steel, covering Canadian stock sizing, machinability, common defects, and handling guidelines for fabrication, woodworking, and machining operations.
Material Overview & Common Uses
430 ferritic stainless steel is a straight-chromium, non-hardenable stainless steel containing approximately 16-18% chromium and minimal nickel. It is magnetic, exhibits good corrosion resistance in mild atmospheres, and offers excellent formability and thermal conductivity compared to austenitic grades. Common applications include automotive trim, appliance panels (dishwasher liners, range hoods), kitchen equipment, heat exchangers, and architectural cladding. In Canadian fabrication shops, 430 is often chosen for its lower cost relative to 304 and its ability to be deep drawn without intermediate annealing. It is not recommended for severe corrosive environments or where weld strength is critical.
Core Technical Properties & Sizing
| Property | Value | Notes |
|---|---|---|
| Chemical Composition (wt%) | Cr 16.00-18.00, C ≤0.12, Mn ≤1.00, P ≤0.040, S ≤0.030, Si ≤1.00, Ni ≤0.75 | Balance Fe |
| Tensile Strength (annealed) | 450–600 MPa | Per ASTM A240 |
| Yield Strength (annealed) | ≥205 MPa | 0.2% offset |
| Elongation in 2 in. | ≥22% | Annealed condition |
| Hardness | ≤89 HRB | Annealed condition |
| Density | 7.80 g/cm³ | — |
| Modulus of Elasticity | 200 GPa | — |
| Thermal Conductivity (100°C) | 26.1 W/m·K | — |
| Electrical Resistivity | 0.60 μΩ·m | — |
| Standard Stock Sizing | Sheet: 48×120 in, 48×96 in; Gauges 16, 18, 20, 22, 24 Plate: 3/16, 1/4, 3/8 in up to 60 in wide Coil: slit 0.5–48 in, thickness 0.020–0.125 in |
Canadian standard |
| Thickness Tolerance (gauges 16–24) | ±0.005 in | ASTM A240/A480 |
| Width / Length Tolerance | ±0.125 in / ±0.250 in | ASTM A240/A480 |
| Flatness Tolerance (stretcher-leveled) | 0.5 in in any 48 in | ASTM A240/A480 |
| Surface Finish Options | No. 1 (HRAP), No. 2B (cold rolled), No. 4 (brushed), No. 8 (mirror) | Floor stock: No. 2B or No. 4 |
Machinability, Tooling & Feeds
430 stainless steel has a machinability rating of approximately 60–70% of AISI 1212 free-machining steel. It is gummy and tends to form built-up edge (BUE) at low speeds. Use generous amounts of water-soluble coolant or heavy-duty cutting oil to reduce heat and prevent work hardening.
| Operation | Tooling | Speed (SFM) | Feed | Notes |
|---|---|---|---|---|
| Turning (Carbide) | C-2 grade carbide inserts | 200–300 | 0.005–0.015 in/rev | Sharp edges, positive rake geometry |
| Turning (HSS) | High-speed steel | 80–120 | 0.005–0.015 in/rev | Reduce speed to control BUE |
| Drilling | HSS or cobalt, 118° point angle | 80–120 | Pecking cycles | Heavy-duty web; clear chips frequently |
| Milling | Carbide | 200–300 | 0.004–0.010 in/tooth | Climb milling preferred to minimize edge burr |
| Tapping | Spiral point taps, 10–15° helix | 30–50 | — | Use thread-forming tap if possible |
| Sawing (solid bar) | Bi-metal blades | 80–120 | 4–6 teeth per inch | — |
| Sawing (sheet/plate) | Bi-metal blades | 100–150 | 10–14 teeth per inch | — |
| Shearing | — | — | Blade clearance 5–10% of thickness | — |
| Forming | — | — | Bend radii 2–3× thickness | Good ductility; avoid sharp radii |
| Welding | 308L filler rod | — | Interpass temperature <300°F | Preheat not required; avoid grain growth |
Common Defects & Quality Control
QC protocol: sample 5% of each lot; perform visual, dimensional, and hardness checks. For critical orders, perform bend test (180° over 2T radius) and ferrite check (magnet test).
| Defect | Description | Inspection Method | Rejection Criteria |
|---|---|---|---|
| Surface scratches & roll marks | From handling or coil processing | Bright light, 10× loupe | Deeper than 10% of gauge |
| Edge cracks & slivers | From slitting operation | Calipers measure crack length | Crack length exceeds 0.125 in |
| Waviness / oil canning | Sheet distortion | Feeler gauge on flat table | Deviation >0.030 in over 12 in |
| Pitting or rust spots | Improper storage or ferrous contamination | Magnet test for contamination; depth gauge | Pitting depth >0.002 in |
| Lamination / delamination | Internal separation in plate | Ultrasonic testing (critical applications) | Detectable delamination |
| Heat tint / oxidation | From annealing process | Visual inspection, depth measurement | Acceptable if ≤0.001 in depth per side |
| Dimensional out-of-tolerance | Thickness, width, or length deviation | Calibrated tape and micrometer | Beyond ASTM A480 limits |
Storage, Handling & Racking Guidelines
Store indoors in a dry, climate-controlled environment (relative humidity <60%, temperature 15–25°C). Keep away from chemical fumes, chlorides, and airborne particulates. Use dedicated racks with rubber or plastic-coated supports to prevent galvanic corrosion. For sheet and plate, store flat on pallets with interleaving paper or plastic film between sheets to prevent scratching. For coil, store on A-frames or cradles with protective wrapping. Do not store carbon steel or copper alloys in the same rack without separation. Use lifting magnets or vacuum lifters for handling; avoid steel slings that can mar the surface. For long-term storage (>30 days), apply a light rust-preventive oil (e.g., LPS-3) and cover with breathable plastic. Implement FIFO (first-in, first-out) inventory rotation. Label each bundle with grade, gauge, finish, lot number, and date received. For racking, maximum load per shelf: 2,000 lbs for sheet, 4,000 lbs for plate. Ensure racks are anchored to floor and rated for seismic zone per Canadian building code.