Type 304 Round Bar

Type 304 is the most widely used austenitic stainless steel, offering an excellent balance of corrosion resistance, formability, and mechanical strength. With a chromium content of 18-20% and nickel of 8-10.5%, 304 round bar serves as the raw material for countless machined components — shafts, valve stems, pump parts, bolts, fittings, and structural supports.

The 18-8 chromium-nickel composition provides robust resistance to atmospheric corrosion, food acids, and organic chemicals. In the annealed condition, 304 round bar is non-magnetic and cannot be hardened by heat treatment, making it ideal for cold forming and machining operations. Strength can only be increased through cold working.

Our round bars are produced through hot rolling or cold drawing, with surface finishes ranging from hot rolled black to precision centerless ground (CG). Each bar is straight, dimensionally accurate, and fully traceable to the original mill heat number.

Our Quality Guarantee

Every order of 304 round bars comes with full traceability. We provide MTR (Mill Test Report) with chemical composition and mechanical properties for each batch, traceable to the original heat code. Our defect rate has been under 0.02% over the past 3 years — if any bar fails to meet ASTM A276 standards, we replace it free of charge.

For stock sizes (1/4" to 4" diameter), we ship within 48 hours. Custom production orders ship within 7-10 business days. Free 300mm samples available — let your clients test quality before committing to a bulk order.

⚠️ Reference Data Only: Values shown are per ASTM A276 / A479 standards. For critical applications, please contact us to verify specifications or request a Mill Test Report (MTR) for your specific batch.

Chemical Composition (%)

Mechanical Properties (Room Temperature, Annealed, Longitudinal)

Available Diameters & Weights (Solid Round Bar)

Standard Length: 20 ft (6m). Custom lengths available. Larger diameters up to 12" (300mm) available upon request. Weight calculated per ASTM standard formula: W (lb/ft) = D² (in) × 2.67.

Applicable Standards

Available Finishes & Conditions

Cold Drawn Diameter Tolerances (per ASTM A276)

Choosing the right stainless steel grade depends on your corrosion environment, welding requirements, and budget. Below is a direct comparison of the three most common austenitic grades used for round bar applications.

304 vs 304L vs 316L Round Bar Comparison

Which One Should You Choose?

Choose 304 for most general applications — machined components, fasteners, shafts, and food contact parts. It offers the best balance of performance and cost for the widest range of applications.

Choose 304L when extensive welding is required on thick bar sections. The lower carbon content (≤0.035%) prevents carbide precipitation in the heat-affected zone, eliminating the need for post-weld annealing to restore corrosion resistance.

Choose 316L for coastal environments, chemical processing, pharmaceutical, or marine applications where exposure to chlorides makes pitting and crevice corrosion a concern. The addition of 2-3% molybdenum provides significantly improved resistance to chloride-induced corrosion.

Other Related Stainless Steel Grades for Reference

Machined Components & Shafts

Pump shafts, mixer shafts, conveyor rollers, and precision-turned parts. Cold drawn 304 round bar provides tight diameter tolerances (±0.002") and a smooth surface that reduces machining time. For rotating seal applications, centerless ground (CG) bars can be used directly without further surface finishing.

Fasteners & Hardware

Bolts, nuts, studs, threaded rods, and washers. 304 round bar is the standard material for stainless steel fasteners due to its combination of 75,000 psi minimum tensile strength, corrosion resistance in atmospheric and indoor environments, and cold heading ductility. Complies with ASTM F593 fastener specification.

Food & Beverage Processing

Sanitary fittings, dairy processing equipment, brewing components, equipment legs, and support frames. The smooth polished surface (Ra ≤ 0.8 µm) prevents bacterial adhesion and meets FDA food contact requirements under 21 CFR 175.300. Suitable for CIP (Clean-in-Place) sanitation cycles.

Valves & Fittings

Valve stems, ball valve components, and fitting blanks machined from 304 round bar. Good machinability allows for complex seal face geometries and precision threading. Compatible with Class 150 to 600 pressure ratings when properly machined and assembled with appropriate packing materials.

Architectural & Structural

Handrail posts, balusters, support brackets, and decorative hardware. Polished 304 round bar offers both structural integrity and an attractive finish for visible installations. 304's natural weathering resistance provides a service life of 30+ years in most urban and suburban environments.

Automotive & Transportation

Exhaust system hangers, engine brackets, and trim components. 304 resists intermittent operating temperatures up to 1500°F (815°C) and road salt corrosion. Cold formed bars can be used for decorative trim and luggage rack components.

Petrochemical & Process Industry

Pipe supports, grating substructures, skid base frames, and instrumentation components. 304 provides cost-effective corrosion resistance in mild chemical environments where organic acids, alcohols, and mild oxidizing agents are present.

Medical Equipment (Non-Implant)

Instrument handles, equipment cart frames, table supports, and lab fixtures. 304's cleanability, sterilization resistance (autoclave, chemical), and non-reactive surface make it suitable for non-implantable medical and pharmaceutical facility applications.

Marine & Coastal (With Caution)

Boat fittings, dock railing, and deck hardware. Note: 304 has limited resistance to continuous saltwater exposure. For components below the waterline or in constant chloride spray, 316L grade should be used instead to prevent pitting corrosion.

Machining

304 stainless steel has a machinability rating of approximately 45% compared to AISI 1212 free-cutting steel. The primary challenges are rapid work hardening and low thermal conductivity (about one-third of carbon steel), which concentrates cutting heat at the tool edge.

Recommended Parameters (Carbide Tooling):

Tooling: Use sharp C-2 or C-3 grade carbide inserts with positive rake angles (5° or more). TiAlN or AlTiN coated grades improve tool life. Avoid high-speed steel (HSS) tools for production work.

Coolant: Flood coolant with water-soluble oil (5-10% emulsion) is essential. The low thermal conductivity of 304 requires adequate cooling to prevent work hardening and maintain surface finish.

Key Tips: Never let the feed rate drop below 0.003 in/rev — a light feed causes the tool to rub against the work-hardened surface rather than cut. Use chip breakers to control long, stringy chips. Maintain constant cutting load; avoid stopping the tool on the workpiece surface.

Welding

304 stainless steel round bar exhibits excellent weldability by all standard fusion methods. The following parameters apply for joining 304 bars or attaching them to other components.

Preheat: Not required for sections under 1" (25mm) thickness. For heavy sections over 2" (50mm), a slight preheat of 200-300°F (93-149°C) may help reduce thermal stress. Interpass temperature should not exceed 350°F (175°C).

Post-Weld Treatment: Post-weld annealing is not typically required to restore corrosion resistance for most applications. For 304L, the low carbon content (≤0.035%) eliminates the risk of sensitization in the heat-affected zone. If maximum corrosion resistance is required after welding 304, full solution annealing at 1850-2050°F followed by rapid cooling is recommended.

Heat Treatment

Important: As an austenitic stainless steel, 304 has no phase transformation and cannot be hardened by heat treatment. Strength can only be increased through cold working (cold drawing, cold rolling, or cold forming).

Cold Forming

304 round bar can be bent and formed in the annealed condition. It offers good ductility (40% elongation minimum in 2") but work hardens more rapidly than carbon steel.

Forming Notes: Use fully annealed bar stock for bending and cold heading operations. Cold drawn bars have reduced ductility due to prior work hardening. Account for springback — 304 typically rebounds 2-3° more than carbon steel in bending. For complex forming sequences, intermediate annealing may be needed between stages to restore ductility.

Q: What is the difference between 304 round bar and 304 round tube?

A: Round bar is solid throughout its cross-section, used when you need material strength and mass for machining into components, fasteners, and shafts. Round tube is hollow with a defined wall thickness, used when weight reduction or fluid flow is required. Bar is specified by diameter alone; tube is specified by outside diameter (OD) and wall thickness. They serve different applications and are not interchangeable.

Q: Can 304 stainless steel round bar rust?

A: 304 is highly resistant to atmospheric corrosion, food acids, and most organic chemicals. However, in environments with high chloride content — such as coastal salt spray, deicing salts, or chlorinated cleaning agents — 304 can develop surface pitting or staining. This surface discoloration is typically superficial and can be removed by passivation or acid cleaning. For continuous marine or chloride exposure, 316L grade is recommended for its molybdenum-enhanced pitting resistance.

Q: Is 304 stainless steel round bar magnetic?

A: In its annealed condition, 304 is essentially non-magnetic (relative permeability μ ≤ 1.02). However, cold working — including cold drawing, machining, bending, or cutting — can induce partial transformation to martensite, producing slight magnetism. This is a normal characteristic of austenitic stainless steel and does not affect corrosion resistance or mechanical properties. The degree of magnetism increases with the amount of cold work applied.

Q: What surface finishes and conditions do you offer for 304 round bar?

A: We supply four standard finishes: Hot Rolled (HR) — as-rolled with mill scale, suitable as raw machining stock; Cold Drawn (CD) — smooth surface with tight tolerances, the most popular choice for general machining; Centerless Ground (CG) — precision ground to exact diameter (±0.0005" tolerance) for piston and seal applications; and Polished — bright surface finish (Ra ≤ 0.8 µm) for food contact, medical, and decorative uses. Contact us for specific finish, roughness, or tolerance requirements.

Q: What is the minimum order quantity (MOQ)?

A: For stock diameters (1/4" to 4"), our MOQ is typically 500 lbs (approx. 225 kg) per size per grade. For non-stock or custom diameters, and for large-volume production orders, MOQ varies by availability. Contact our sales team for a quote specific to your size, quantity, and delivery requirements.

Q: Can you cut round bars to custom lengths?

A: Yes. Our standard length is 20 ft (6m). We can precision-cut to any custom length with a typical tolerance of ±1/8" (±3mm). We also offer secondary machining services including turning, threading, drilling, chamfering, and keyway cutting to your specifications.

Q: Do you provide Material Test Reports (MTR)?

A: Yes. Every order of 304 round bars is accompanied by a Mill Test Report (MTR) certifying the chemical composition and mechanical properties per ASTM A276, traceable to the original heat number and mill. Third-party inspection by SGS, TÜV, or BV can also be arranged upon request (additional charges apply).

Q: What diameter tolerances do you hold on cold drawn 304 round bar?

A: Cold drawn 304 round bar is supplied to ASTM A276 dimensional tolerance standards. Typical tolerances are: ±0.002" for diameters under 1", ±0.003" for diameters 1" to under 2", ±0.005" for diameters 2" to 4" inclusive, and negotiated tolerances for diameters over 4". Centerless ground bars can be held to ±0.0005" for precision applications.

Q: Can I get a sample before ordering?

A: Yes. We provide free 300mm (approximately 12") samples so you can evaluate surface quality, dimensional accuracy, and machinability before committing to a production order. You only need to cover the shipping cost. Contact us with your required diameter, finish, and delivery address.

Q: What is the maximum operating temperature for 304 round bar?

A: 304 can be used at continuous service temperatures up to approximately 1650°F (900°C) in air, and intermittent service up to 1500°F (815°C). Beyond these temperatures, significant oxidation and scaling may occur. For sustained high-temperature applications such as furnace parts or heat exchangers, consider 310S or 321 grades which offer superior high-temperature performance.

Q: Are 304 and 18-8 stainless steel the same thing?

A: "18-8" is an industry shorthand referring to the family of austenitic stainless steels containing approximately 18% chromium and 8% nickel. This family includes grades 302, 304, 304L, and others. Grade 304 (with its standard composition of 18-20% Cr and 8-10.5% Ni) is the most common 18-8 grade. While the terms are sometimes used interchangeably in practice, "18-8" is not a formal ASTM or SAE grade designation — specifications and mechanical properties should always reference the specific ASTM grade (e.g., 304 per ASTM A276).

Q: What shipping and payment terms do you support?

A: We support FOB, CIF, CFR, and EXW trade terms. Standard payment terms are T/T (telegraphic transfer, 30% deposit with 70% balance before shipment) and L/C (irrevocable letter of credit at sight). Long-term contract pricing is available for volume commitments. Contact our sales team to discuss your specific logistics requirements.