Introduction

303 free machining stainless steel round bar (also 303 machinable stainless steel bar, 303 austenitic stainless steel round bar, 303 high machinability stainless steel, 303 sulfur added stainless steel) is an austenitic grade specifically designed for high‑speed automatic machining. The addition of sulfur (0.15‑0.35%) creates chip‑breaking inclusions, delivering excellent machinability and easy cutting performance with improved machinability vs 304 (by approximately 40‑50%). This 303 stainless steel for automatic machining reduces tool wear, allows faster feed rates, and produces superior surface finishes, making it the preferred choice for precision machining and high‑volume turned components where welding is not required.

Chemical components(%)

Mechanical properties

Physical properties

303 Stainless Steel Round Bar Available Products and Standard

1. ASTM A582 / ASME SA582 

(Standard Specification for Free‑Machining Stainless Steel Bars and Wire Rods)

Type:

• 303 Free Machining Stainless Steel Round Bar

• 303 Machinable Stainless Steel Bar

• 303 High Machinability Stainless Steel Wire Rod

Size Range:

• Round bar: 1.5 – 150 mm dia (cold drawn or hot rolled)

• Hex bar: 3.0 – 100 mm across flats

• Square bar: 3.0 – 100 mm

• Flat bar: up to 150 mm thick × 500 mm wide

• Wire rod: 1.5 – 15.0 mm dia (coils)

• Length: 2000 – 6000 mm (random or fixed)

Surface: Cold drawn (bright), Hot rolled (descaled), Ground, Peeled, Turned

Testing: Chemical analysis (C ≤0.15%, Mn ≤2.00%, P ≤0.20%, S 0.15‑0.35%, Si ≤1.00%, Cr 17‑19%, Ni 8‑10%), tensile test (Rm 500‑750 MPa depending on condition), elongation (≥30% for annealed), hardness (≤262 HB or ≤90 HRB for annealed), flattening test (for wire), eddy current test (optional), dimensional inspection

2. ASTM A276 

(Standard Specification for Stainless Steel Bars and Shapes)

Type: 

• 303 Austenitic Stainless Steel Round Bar

• 303 Stainless Steel Shafts

• 303 Stainless Steel Bolts and Nuts

• 303 Stainless Steel Precision Parts

• 303 Stainless Steel Fasteners

Size Range:

• Round bar: 3.0 – 355 mm dia (hot rolled or cold finished)

• Hex bar: up to 100 mm

• Square bar: up to 100 mm

• Length: up to 8000 mm

Surface: Annealed (Condition A), Hot rolled, Cold drawn, Ground, Peeled, Turned

Testing: Chemical analysis, tensile test (Condition A: Rm ≥500 MPa, Rp0.2 ≥205 MPa, elongation ≥30%; Condition B (cold finished): Rm ≥690 MPa, elongation ≥12%), hardness (Condition A: HB ≤262; Condition B: HRC ≤25), flattening test (for bar), ultrasonic test (for large diameters), dimensional inspection

Applications

(1)Shafts – 303 stainless steel for shafts (pump shafts, motor shafts, actuator shafts, light‑duty transmission shafts) leverages its excellent machinability and easy cutting performance, enabling fast turning, grooving, and key seating while maintaining good corrosion resistance in mild environments.

(2)Bolts and nuts – 303 stainless steel for bolts and nuts (screws, threaded rods, hex bolts, wing nuts) benefits from sulfur‑added chip control during thread rolling and cutting, producing clean, burr‑free threads without excessive tool wear.

(3)Precision parts – 303 stainless steel for precision parts (instrument components, sensor housings, medical device fittings, pneumatic connector bodies) provides superior surface finish and dimensional accuracy, meeting tight tolerances on CNC lathes and Swiss‑type automatic screw machines.

(4)CNC machining – 303 stainless steel for CNC machining (high‑volume turned parts, custom fittings, adapters, bushings, spacers) offers improved machinability vs 304, reducing cycle times and extending tool life for cost‑effective production on automated lathes.

(5)Fasteners – 303 stainless steel for fasteners (machine screws, set screws, studs, threaded inserts) combines easy cutting performance with good corrosion resistance in atmospheric and mild chemical service, ideal for electronic enclosures, hardware assemblies, and food machinery.

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