| Chemical Composition | Chromium (Cr) | Typically 16.0–18.0% under common JIS SUS201 specifications | Supports the passive oxide layer that provides corrosion resistance. | Review the heat-specific mill test certificate and verify by PMI when required. |
| Nickel (Ni) | Typically 3.5–5.5% | Influences austenitic structure, formability, toughness, and corrosion performance. | Check the actual chemistry against the applicable standard and purchase specification. |
| Manganese (Mn) | Typically 5.5–7.5% | Partially substitutes for nickel and helps stabilize the austenitic structure. | Confirm the heat analysis because excessive variation can affect forming and magnetic response. |
| Carbon (C) | Maximum commonly specified level: 0.15% | Higher carbon can reduce weld corrosion resistance and affect ductility. | Check the certified heat chemistry, especially for welded applications. |
| Silicon (Si) | Maximum commonly specified level: 1.00% | Affects deoxidation, strength, and forming behavior. | Compare the mill certificate with the stated standard. |
| Phosphorus (P) | Maximum commonly specified level: 0.060% | Excess phosphorus may reduce toughness and weldability. | Require heat-level chemical analysis. |
| Sulfur (S) | Maximum commonly specified level: 0.030% | Low sulfur generally supports better ductility, weldability, and corrosion performance. | Verify against the selected standard and end-use requirements. |
| Nitrogen (N) | Often controlled to approximately 0.25% maximum, depending on the specification | Can influence strength, phase stability, and forming behavior. | Confirm whether nitrogen is included in the selected standard or purchase order. |
| Mechanical Properties | Tensile strength | Common annealed reference minimum: approximately 655 MPa | Indicates resistance to breaking under tension. | Request tensile-test results taken in the rolling direction and transverse direction where applicable. |
| 0.2% proof stress / yield strength | Common annealed reference minimum: approximately 275 MPa | Helps predict permanent deformation during stamping and forming. | Compare the certificate values with the forming design limits. |
| Elongation | Common annealed reference minimum: approximately 40% in a standard tensile test | Higher elongation generally indicates better formability. | Use the test direction, gauge length, and applicable standard when comparing values. |
| Hardness | Common annealed reference: up to about 100 HRB | A practical indicator of temper, work hardening, and process consistency. | Check hardness using the test method specified in the purchase order. |
| Temper condition | Annealed, quarter-hard, half-hard, or full-hard, according to the required application | Cold reduction increases strength and hardness but normally reduces ductility. | State the temper explicitly; do not evaluate coils by grade alone. |
| Dimensions and Shape | Thickness | Specify the nominal thickness and permitted tolerance; typical commercial coil ranges vary by mill and process. | Thickness affects weight, stiffness, forming force, and dimensional fit. | Measure multiple points across the strip width and along the coil length. |
| Width | Specify the required slit or mill width and edge tolerance. | Correct width reduces trimming, scrap, and downstream setup time. | Verify width with calibrated gauges at the coil head, middle, and tail. |
| Flatness and shape | No unacceptable edge wave, center buckle, coil set, or crossbow for the intended line. | Poor flatness can cause feeding, welding, blanking, and stamping problems. | Inspect a released sample or conduct a trial on the actual processing equipment. |
| Coil inner diameter and outer diameter | Must match the uncoiler, slitting line, or storage system. | Incorrect dimensions can prevent safe loading or cause line downtime. | Confirm dimensions, maximum coil mass, and lifting requirements before ordering. |
| Edge condition | Choose slit edge, mill edge, or deburred edge according to the process. | Edge quality affects safety, cracking, burr height, and tool life. | Define maximum burr height and inspect the first and last wraps. |
| Surface and Finish | Surface finish designation | Common options include 2B, BA, No. 1, and other specified finishes. | Finish influences appearance, reflectivity, roughness, cleanability, and further processing. | Specify the finish standard and use visual inspection plus roughness testing where needed. |
| Surface defects | No unacceptable scratches, pits, roll marks, scale, rust staining, dents, or laminations. | Defects may remain visible after forming or reduce corrosion resistance. | Inspect under controlled lighting and document acceptance limits with photographs. |
| Surface roughness | Set a project-specific Ra limit because allowable roughness depends on the finish and application. | Controls friction, appearance, coating adhesion, and cleanability. | Use a calibrated surface-roughness tester when numerical control is required. |
| Protective packaging | Use moisture-resistant, impact-resistant packaging suitable for the transport route. | Prevents transit damage, condensation staining, and contamination. | Check packaging, coil identification, and moisture condition on arrival. |
| Performance and Application | Corrosion environment | SUS201 is generally more economical than 18-8 stainless grades but is less suitable for severe chloride, marine, or highly corrosive environments. | Material selection should reflect humidity, salt exposure, chemicals, temperature, and cleaning conditions. | Perform application-specific corrosion testing or consult the governing design standard. |
| Weldability | Suitable welding procedure, heat input, filler, and post-weld cleaning must be established. | Welding can affect distortion, strength, surface condition, and localized corrosion resistance. | Require a qualified welding procedure and test representative samples. |
| Magnetic response | Annealed austenitic SUS201 is normally low-magnetic, while cold working can increase magnetic response. | Important for sensors, appliances, decorative parts, and applications with magnetic limits. | Define an acceptance method; use a magnetic permeability test when necessary. |
| Density for weight estimation | Approximately 7.86 g/cm³ as a commonly used engineering reference | Supports coil-mass estimates, logistics planning, and material utilization calculations. | Calculate using actual dimensions and confirm the shipped mass with a calibrated scale. |
| Quality and Purchasing | Applicable standard | State the exact standard and product form, such as JIS G4304 or an equivalent agreed specification. | “SUS201” alone does not define every dimensional, mechanical, surface, or testing requirement. | Include grade, standard, finish, temper, dimensions, tolerances, and inspection requirements in the purchase order. |
| Traceability | Every coil should have a heat number, coil number, specification, dimensions, and production or inspection records. | Enables nonconformance investigation and consistent replenishment. | Match coil markings, packaging labels, and mill certificates before acceptance. |
| Inspection plan | Define sampling frequency for chemistry, dimensions, mechanical properties, finish, and surface condition. | A documented plan reduces disputes and confirms suitability before full production. | Use calibrated instruments and retain inspection records linked to the heat number. |
| Total delivered cost | Evaluate price, yield, freight, packaging, inspection, storage, processing loss, and rejection risk together. | The lowest purchase price may not produce the lowest overall manufacturing cost. | Compare suppliers using the same specification, tolerances, quantity, delivery term, and quality requirements. |
