301 303 304 309S and 310S Stainless Steel Cold Drawn Coils: Grade Guide

What Cold Drawing Does to Austenitic Stainless Steel

Cold drawn coils are produced by drawing annealed stainless strip, wire or bar through a die at room temperature. The deformation raises tensile and yield strength, improves dimensional accuracy and gives a bright, consistent surface, but it also consumes ductility and leaves residual stress in the material. That is why a cold drawn product is normally supplied in a defined temper, or is annealed after drawing when maximum formability is needed.

Grades 301, 303, 304, 309 and 310S are the five grades most often requested as cold drawn or cold rolled coil and wire, and each brings a different balance of formability, machinability and heat resistance. Relevant specifications include ASTM A666 for austenitic flat-rolled products, ASTM A580 and ASTM A313 for wire, and ASTM A582 for free-machining bar.

Grade Comparison Table

The table below lists typical composition ranges and the properties that drive grade selection for cold drawn coil and wire.

Grade	Cr %	Ni %	C % max	Key properties	Typical applications
301	16.0-18.0	6.0-8.0	0.15	Strong work hardening, high strength in cold worked tempers	Springs, clips, structural sections, automotive parts
303	17.0-19.0	8.0-10.0	0.15	Free-machining, sulphur-bearing, best machinability	Fasteners, fittings, precision machined parts
304	18.0-20.0	8.0-10.5	0.08	General-purpose corrosion resistance, excellent weldability	Food equipment, kitchenware, architecture, medical parts
309S	22.0-24.0	12.0-15.0	0.08	High-temperature oxidation resistance, good weldability	Furnace parts, heat exchangers, high-temperature equipment
310S	24.0-26.0	19.0-22.0	0.08	Superior high-temperature strength and oxidation resistance	Boiler components, heat treatment fixtures, chemical processing

Note the deliberate split between type 309 and 309S. The low-carbon 309S variant is the grade normally stocked for welded components, because its 0.08 % carbon maximum reduces the risk of carbide precipitation during high-temperature service.

Mechanical Properties and Tempers

Annealed 304 coil typically shows tensile strength around 515-700 MPa and yield strength near 205 MPa, with elongation above 40 %. Cold drawing changes those figures sharply. Grade 301 is the grade that develops the most strength, and it is supplied in tempers from quarter hard to full hard:

Annealed 301: tensile strength about 758 MPa minimum, good ductility.

Quarter hard 301: tensile strength about 862 MPa, yield strength about 517 MPa.

Half hard 301: tensile strength about 1034 MPa.

Full hard 301: tensile strength about 1275 MPa, yield strength about 965 MPa.

Grade 303 is normally supplied annealed or cold drawn for machining rather than for spring properties, because its sulphur additions reduce ductility and corrosion resistance. Grades 309S and 310S are usually supplied annealed, since their purpose is heat resistance rather than cold worked strength.

Corrosion and High-Temperature Behaviour

Cold work has a measurable effect on corrosion resistance. Heavy deformation can make the material more susceptible to stress corrosion cracking, and in chloride service cold worked 304 will crack before annealed 304 does. Where a component combines cold forming with chloride exposure, a post-forming anneal or the selection of a molybdenum-bearing grade is the safer route.

Grades 309S and 310S are chosen for their resistance to oxidation and scaling at high temperature rather than for strength. Their high chromium and nickel content keeps a protective oxide layer stable in continuous furnace and heat-treatment service, while lower-alloyed grades scale and lose section.

Quality Checks on Incoming Cold Drawn Coils

Confirm grade and temper on the mill certificate, not just the grade.

Check hardness and tensile test results against the ordered temper.

Verify dimensions and ovality against the agreed tolerance.

Look for draw marks, laps or surface defects on the coil face.

Confirm freedom from embedded iron to protect corrosion performance.

Selecting the Right Grade

The decision usually follows three questions. If the part must be machined in volume, 303 is the practical answer. If the part must form and weld into a corrosion-resistant assembly, 304 is the default. If the part must carry load as a spring or clip in the cold worked state, 301 gives the highest strength from the same drawing operation. When the service temperature rises above the range that 304 can survive, 309S and 310S take over.

Frequently Asked Questions

Q: What is the difference between cold drawn and annealed coil?
Cold drawn coil has been deformed at room temperature to raise strength and tighten tolerance, while annealed coil has been heat treated for maximum softness and ductility.

Q: Why is 301 used for springs rather than 304?
Grade 301 work hardens faster than 304, so a single drawing pass delivers higher strength without a separate heat treatment.

Q: Can cold drawn 304 coil be welded after forming?
Yes, but welding partially anneals the cold worked material, so strength drops locally and heat input should be controlled.

Q: Is grade 303 suitable for welded assemblies?
No. Its sulphur content improves machining but reduces weldability and corrosion resistance, so 303 is normally used for machined parts only.

Q: When should 309S be replaced by 310S?
310S is selected when service temperature and oxidation severity are higher than 309S can tolerate, and when greater creep resistance is needed.

Q: Does cold drawing change corrosion resistance?
It can. Heavy cold work reduces resistance to stress corrosion cracking, so heavily drawn parts in chloride service often need an anneal.