201 Stainless Screw Wire - Nitrogen Strengthened Grade
201 stainless screw wire
,nitrogen strengthened stainless wire
,stainless steel spring wire
201 Stainless Screw Wire with Nitrogen Strengthening
Product Introduction
201 is the grade a screw maker looks at when 304 prices stop fitting the part. It keeps the austenitic structure and the forming behaviour, but it holds less nickel and relies on manganese and nitrogen to do that job instead.
The nitrogen is what makes the substitution work. It stabilises the austenite and raises yield strength at the same time, so a 201 screw wire can be drawn to a higher strength than 304 at the same anneal. What it does not do is replace molybdenum, and it does not restore the corrosion margin that the missing nickel took away.
Available from 0.15 mm to 12 mm, in annealed condition for heading and thread rolling, bright or soap coated.
Product Specifications
| Parameter | Specification |
|---|---|
| Grade | AISI 201, SUS 201, EN 1.4372 |
| Chromium | 16.0–18.0% |
| Nickel | 3.5–5.5% |
| Manganese | 5.5–7.5% |
| Nitrogen | 0.05–0.25% |
| Carbon | ≤ 0.15% |
| Diameter Range | 0.15–12 mm |
| Diameter Tolerance | ±0.02 mm up to 2.0 mm; ±0.03 mm above 2.0 mm |
| Delivery Condition | Soft annealed, bright annealed, or cold drawn light temper |
| Tensile Strength | 600–800 MPa, annealed; higher on request |
| Yield Strength | ≥ 310 MPa, annealed |
| Elongation | ≥ 40%, annealed |
| Hardness | ≤ 95 HRB, annealed |
| Surface | Bright or soap coated |
| Coil Weight | 100–500 kg |
| Reference Standard | ASTM A555, EN 10263-5, JIS G4309 |
What Nitrogen Does in a 201 Wire
Holding the Austenite With Less Nickel
Nickel is an austenite former, and 201 is short of it. Manganese and nitrogen take over that role. Nitrogen is the far stronger of the two per unit of content, which is why the grade can stay fully austenitic at 3.5–5.5% nickel instead of the 8% that 304 carries.
Higher Yield at the Same Anneal
Nitrogen in solid solution pins dislocations, so yield strength sits higher for the same annealing cycle. On a screw this shows up as a stiffer shank and better resistance to thread stripping under torque, without the part becoming brittle.
A Steeper Work Hardening Curve
201 hardens faster than 304 as it is formed. For thread rolling that is an advantage, because the thread flanks reach working hardness quickly. For a long multi-station heading sequence it is the opposite, and the forming plan has to allow for it.
Where 201 Screw Wire Fits, and Where It Does Not
Dry Interior Service
Interior fastening away from standing water and chlorides is the natural home of a 201 screw. Drywall screws, furniture assembly, appliance panels and general hardware all sit inside this window, and the cost difference against 304 is real at volume.
The Wet and Chloride Boundary
Lower nickel means a thinner passive film repair reserve. In continuously damp conditions, in coastal air, or in contact with chloride-bearing cleaners, 201 will show rust spotting where 304 would not. If the part sees those conditions, the grade choice has to be revisited rather than compensated for by a coating.
Magnetic Response
Annealed 201 is essentially non-magnetic, but it becomes noticeably magnetic after heading and thread rolling. Where a magnet test is part of incoming inspection, that behaviour has to be agreed in advance so a sound lot is not rejected on a magnet.
Forming 201 Into Screws
Head Forming
The annealed wire upsets cleanly with tooling set for 304. Because the grade hardens faster, the head-to-shank ratio and the number of blows are usually the first two parameters reviewed when a 304 part is transferred to 201.
Die Wear
Higher yield strength and faster work hardening both raise load on the die. Tool life on a converted line is typically shorter, which is a cost that belongs in the conversion calculation and not in the surprise column of the first production month.
Thread Rolling and Springback
Thread rolling on 201 produces a hard, well-formed flank. Springback after rolling is slightly higher than 304, so a thread ring gauge check on the first parts of each lot is worth keeping in the setup sheet.
Applications
Drywall and Self-Tapping Screws
High-volume interior fasteners where the wire cost dominates the part cost and the service environment stays dry.
Furniture and Appliance Fasteners
Assembly screws and hardware inside cabinets, frames and appliances, where appearance under normal interior conditions is the requirement.
General Interior Hardware
Brackets, clips and small fittings produced on high-speed headers, where a consistent annealed structure matters more than the corrosion margin of a 304.
Product Advantages
- Nitrogen-strengthened austenitic structure at 3.5–5.5% nickel, so the wire cost per part is lower than 304 without giving up formability.
- Yield strength of at least 310 MPa in the annealed condition gives a stiffer shank and better torque performance than a lower-yield substitute.
- Annealed structure and diameter tolerance stated per lot, so heading and thread rolling stay repeatable coil to coil.
- Soap coated option for high-speed headers, reducing die wear on a grade that already loads the tooling harder.
- Chemistry including nitrogen reported on the certificate, so the grade can be verified rather than assumed.
Quality Control
Chemical composition by optical emission including nitrogen, tensile strength and yield, elongation, hardness, diameter and ovality, and surface condition under magnification. Where the part is headed from the wire, an upsetting test is added. A mill test certificate 3.1 is issued with each shipment.
Selection and Ordering Notes
- State the service environment first. Dry interior is where 201 belongs; damp, coastal or chloride contact is where it does not.
- Give the annealing condition and the tensile range needed for your heading sequence.
- Confirm whether the part will be passivated or coated after forming, since that changes the surface requirement on the wire.
- State the diameter and tolerance class, and whether soap coating is needed for high-speed feeding.
- If the part was previously run in 304, send the tooling data so the change in work hardening rate can be reviewed before the first coil.
Tell us the part, the forming sequence and the service environment, and we will confirm whether 201 is the right grade or whether the application needs the nickel back.
