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Material: Stainless steel ASTM A276, A484, S479
Type: Round bar,Square bar,Hex bar,Flat bar
Tolerance: H7 H9 H10 H11
Surface: Black or Bright or Pickling white
Diameter: 5~500mm
Length: ≦12M or As Per Client's Requirements.
Stainless steel round bars are solid, cylindrical metal bars produced from stainless steel alloys. Stainless steel round bars are manufactured through hot rolling, cold drawing, or forging processes, depending on the desired dimensional tolerance, surface finish, and mechanical properties. The diameter range typically spans from 3 mm to 500 mm, with lengths from 1 meter to 12 meters available in standard and custom sizes.
Type | Round Bar Square Bar Hexagon Bar Flat Bar | ||
Surface | Black or Bright or Pickling white | ||
Standard | SUS, AISI, DIN | ||
Manufacture Technique | Hot Rolling, Cold-drawing | ||
Diameter | 5~500mm | ||
Length | ≦12M or As Per Client's Requirements. | ||
Diameter Tolerance | H7 H9 H10 H11 | ||
Material Grade | Stainless Steel | ASTM/ASME SA 276 /479 | 304/SUS304/UNS S30400, 304L/UNS S30403, 316/UNS S31600, 316Ti/UNS S31635, 316H/UNS S31609, 316L/UNS S31603, 310S/UNS S31008, 321/UNS S32100, 321H/UNS S32109, 347/UNS S34700, 347H/UNS S34709, F51/S31803/2205, F53/S32750/2507, F55/S32760, F44/S31254/254SMO, S31050/1.4466, F904L/N08904,Alloy 800HT/Incoloy 800HT/UNS N08811, Alloy 800/Incoloy 800/UNS N08800, Alloy 800H/Incoloy 800H/UNS N08810 |
ASTM/ASME SA 479 | 304H/UNS S30409 | ||
Stainless steel round bars are classified by their surface condition and manufacturing finish. The five principal types are summarized below.
Bar Type | Surface Roughness (Ra) | Diameter Tolerance | Typical Application |
Hot-Rolled (HR) | 6.3–25 µm | ±1–2% of diameter (h11–h13) | Structural components, forgings, shafts for general service |
Cold-Drawn (CD) | 0.8–3.2 µm | ±0.05–0.15 mm (h9–h11) | Machining blanks, precision shafts, fasteners |
Centerless-Ground (CG) | 0.4–0.8 µm | ±0.02–0.05 mm (h7–h9) | Hydraulic rods, pump shafts, linear guides |
Peeled / Turned | 1.6–6.3 µm | ±0.1–0.3 mm (h10–h12) | Forging stock, large-diameter bars, machining preforms |
Polished (Bright) | 0.1–0.4 µm | ±0.02–0.05 mm (h7–h8) | Decorative, medical, food-contact, architectural |
JN Alloys supplies stainless steel round bars across all major alloy families. The following grades are available as round bars in various diameters, lengths, and surface conditions.
Grade | UNS No. | Cr % | Ni % | Mo % | Key Feature | Primary Applications |
304 / 304L | S30400/S30403 | 18-20 | 8-12 | - | Most popular, good general corrosion resistance | Food processing, chemical tanks, architectural |
316 / 316L | S31600/S31603 | 16-18 | 10-14 | 2-3 | Superior pitting and crevice corrosion resistance | Marine, pharma, chemical equipment |
316Ti | S31635 | 16-18 | 10-14 | 2-3 + Ti | Titanium stabilized for intergranular corrosion | High-temp chemical processing |
317 / 317L | S31700/S31703 | 18-20 | 11-15 | 3-4 | Higher Mo for aggressive chloride environments | Bleach plants, flue gas desulfurization |
321 | S32100 | 17-19 | 9-12 | - + Ti | Titanium stabilized for welding applications | Aircraft exhaust, heat exchangers |
347 | S34700 | 17-19 | 9-13 | - + Nb | Niobium stabilized for high-temp service | High-temperature piping, boiler components |
904L | N08904 | 19-23 | 23-28 | 4-5 | High alloy austenitic, excellent acid resistance | Sulfuric acid, phosphoric acid plants |
254SMO (F44) | S31254 | 19-22 | 17-22 | 6-7 | 6% Mo super austenitic, extreme chloride resistance | Seawater, offshore, desalination plants |
Grade | UNS No. | Cr % | Ni % | Condition | UTS (MPa) | Primary Applications |
17-4PH | S17400 | 15-17.5 | 3-5 | H900 | 1310 min | Aerospace, chemical, pump shafts |
Stainless steel round bars are produced through a sequence of metallurgical and mechanical operations. The five principal production routes are outlined below.
Route | Process Steps | Typical Output |
Hot Rolling | Billet heating → Rough rolling → Finish rolling → Cooling → Straightening → Cutting | HR round bars, 10–500 mm dia., No.1 finish |
Cold Drawing | HR bar → Pickling → Pointing → Drawing through die → Straightening → Cutting | CD round bars, 3–100 mm dia., h9–h11 tolerance |
Centerless Grinding | HR or CD bar → Centerless grinder → Straightening → Inspection | CG round bars, 5–150 mm dia., h7–h9 tolerance |
Forging | Billet heating → Press or hammer forging → Trimming → Heat treatment → Machining | Forged bars, 50–800 mm dia., as-forged or machined |
Peeling / Turning | HR bar → Lathe/peeling machine → Straightening → Inspection | Peeled bars, 20–500 mm dia., h10–h12 tolerance |
Melting and Casting
All stainless steel round bars begin as raw materials — iron ore, chromium, nickel, molybdenum, and other alloying elements — melted in an Electric Arc Furnace (EAF) or Argon Oxygen Decarburization (AOD) vessel. The AOD process is critical for achieving the ultra-low carbon content required in L-grades (e.g., 304L, 316L) and for precisely controlling nitrogen in duplex grades. After refining, the molten steel is continuously cast into billets (typically 130–300 mm square) or round blooms for subsequent rolling.
Hot Rolling
Billets are reheated to 1,100–1,250 °C and passed through a series of rolling stands that progressively reduce the cross-section to the target diameter. The bar emerges at 850–1,000 °C and is cooled on a cooling bed before straightening and cutting to length. Hot-rolled bars carry a characteristic oxide scale (No.1 finish) and are the baseline product from which all other bar types are derived.
Cold Drawing
Cold drawing pulls a pointed hot-rolled bar through a carbide or diamond die at room temperature. Each pass reduces the diameter by 0.5–3.0 mm, improving surface finish, dimensional accuracy, and mechanical properties through strain hardening. Multiple draws may be applied for very tight tolerances. Between draws, bars are annealed to relieve residual stress and restore ductility if further drawing is required.
Forging
Forged round bars are produced by pressing or hammering heated billets between dies. Forging aligns the grain flow with the bar axis, resulting in superior mechanical properties — particularly impact toughness and fatigue resistance — compared to rolled bars of the same grade. Forged bars are essential for high-integrity applications: pressure vessel components, offshore connectors, and power generation shafts. They are available in larger diameters (up to 800 mm) that cannot be economically produced by rolling.
Heat Treatment
Heat treatment is the final critical step that determines the mechanical properties of the finished bar. The most common treatments are:
•Solution annealing (austenitic and duplex grades): Heat to 1,020–1,150 °C, hold, then water-quench. Dissolves carbides and restores maximum corrosion resistance.
•Quench and temper (martensitic grades): Austenitize at 950–1,050 °C, oil- or air-quench, then temper at 400–700 °C to achieve target hardness.
•Precipitation hardening: Solution treat at 1,020–1,060 °C, then age at 480–620 °C. Achieves ultra-high strength (up to 1,310 MPa UTS for 17-4PH H900).
Stainless steel round bars are governed by a comprehensive set of international standards that define chemical composition, mechanical properties, dimensional tolerances, surface quality, and testing requirements. Understanding which standard applies is essential for correct material specification and procurement.
Standard | Scope | Key Details |
ASTM A276 | Stainless steel bars and shapes — general purpose | Covers hot-finished and cold-finished bars in austenitic, ferritic, martensitic, and duplex grades. The most commonly cited standard for SS round bars. |
ASTM A479 | Stainless steel bars for boilers and pressure vessels | Similar to A276 but with additional requirements for intergranular corrosion testing and tensile testing. Mandatory for ASME pressure vessel applications. |
ASTM A484 | General requirements for stainless steel bars and billets | Umbrella specification covering tolerances, quality, marking, and testing. Referenced by A276 and A479 for supplementary requirements. |
ASTM A564 | PH stainless steel bars | Covers precipitation-hardening grades (17-4PH, 15-5PH, 13-8Mo, etc.) with detailed aging condition designations and property tables. |
ASTM A582 | Free-machining stainless steel bars | Covers grades 303, 416, 430F, and other free-machining alloys with sulfur or selenium additions for enhanced machinability. |
Source: ASTM International, 2024–2026 editions
Standard | Scope | Key Details |
EN 10088-3 | Chemical composition and mechanical properties of stainless steel long products | Defines grades by material number (e.g., 1.4404 = 316L) and specifies property requirements for bars, wire rod, and profiles. |
EN 10278 | Dimensional tolerances for bright steel products | Specifies h-tolerance classes for cold-drawn, ground, and polished bars. Replaces DIN 668 and DIN 671. |
EN 10060 | Dimensional tolerances for hot-rolled round bars | Covers diameter, out-of-roundness, and straightness tolerances for HR bars. |
EN 10204 | Inspection documents (MTC types) | Defines 3.1 (mill certificate) and 3.2 (third-party validated) material test certificate formats. |
Source: CEN — European Committee for Standardization, 2023–2025 editions
Standard | Origin | Scope |
JIS G 4303 | Japan | Stainless steel bars — Japanese Industrial Standard; widely used in Asia-Pacific procurement |
GB/T 1220 | China | Stainless steel bars — Chinese national standard; required for domestic market sales in China |
ISO 286-2 | International | GPS — Tolerance grades for linear dimensions; defines h7, h9, h11 etc. tolerance classes |
ASTM A314 | USA | Stainless steel billets for forging; upstream specification for forged bar production |
Source: JSA, SAC, ISO, ASTM International
Specifying the correct tolerance class is essential for ensuring that the round bar will fit, machine, or assemble as intended. The table below maps the standard ISO tolerance classes to their corresponding bar type and applicable standard.
Tolerance Class | Bar Type | Diameter (mm) | Max Deviation (mm) | Standard |
h7 | Centerless-ground / Polished | 6–80 | ±0.009 to ±0.030 | EN 10278 / ISO 286 |
h8 | Centerless-ground / Polished | 6‘80 | ±0.013 to ±0.046 | EN 10278 / ISO 286 |
h9 | Cold-drawn | 3–100 | ±0.025 to ±0.087 | EN 10278 / ISO 286 |
h10 | Peeled | 20–500 | ±0.084 to ±0.32 | EN 10060 |
h11 | Hot-rolled (fine) | 10–500 | ±0.13 to ±0.52 | EN 10060 / ASTM A484 |
h13 | Hot-rolled (standard) | 10–500 | ±0.27 to ±1.15 | ASTM A484 |
Source: ISO 286-2:2010; EN 10278:2003; ASTM A484/A484M-23
Q: What is the difference between hot-rolled and cold-drawn stainless steel round bars?
A: Hot-rolled bars are produced at high temperature (1,100+ °C) with a rough, scaled surface and wide tolerances (h11–h13). Cold-drawn bars are pulled through a die at room temperature, yielding a smooth surface (Ra 0.8–3.2 µm) and tight tolerances (h9–h11). Cold drawing also increases yield strength by 10–30% through work hardening. Use hot-rolled bars for structural and forging applications; specify cold-drawn for machining and precision parts.
Q: Which stainless steel round bar grade is best for marine environments?
A: For marine and seawater service, duplex grade 2205 (PREN ≈ 36) or super duplex 2507 (PREN ≈ 43) is recommended. Grade 316L (PREN ≈ 26) is acceptable for splash-zone and brackish-water applications but may suffer crevice corrosion under prolonged seawater immersion. Avoid austenitic grades without molybdenum (e.g., 304) in any chloride-containing environment.
Q: What is PREN and why does it matter for stainless steel round bars?
A: PREN (Pitting Resistance Equivalent Number) = %Cr + 3.3×%Mo + 16×%N. It predicts resistance to chloride pitting — the dominant corrosion mechanism for stainless steel in marine and chemical service. A PREN below 22 indicates susceptibility to pitting in warm seawater; PREN 30+ is required for reliable seawater service; PREN 40+ is specified for subsea and H2S environments per NACE MR0175/ISO 15156.
Q: What standards apply to stainless steel round bars?
A: The primary standards are: ASTM A276 (general-purpose bars), ASTM A479 (pressure vessel bars), ASTM A564 (PH grades), ASTM A582 (free-machining grades), and ASTM A484 (general requirements including tolerances). In Europe, EN 10088-3 covers chemical composition and properties, EN 10278 covers bright bar tolerances, and EN 10060 covers hot-rolled bar tolerances. Japanese JIS G 4303 and Chinese GB/T 1220 are common in Asia-Pacific markets.
Q: Can stainless steel round bars be machined directly without heat treatment?
A: Austenitic grades (304, 316, 316L) are typically supplied in the solution-annealed condition and can be machined directly. However, they are gummy and work-harden rapidly, so sharp tools and positive feeds are essential. For high-volume CNC machining, free-machining grade 303 (sulfur-added) reduces cutting forces by 25–40% and significantly extends tool life. Martensitic grades (410, 420, 440C) and PH grades (17-4PH) should be machined in the solution-treated (soft) condition and hardened afterward.
Q: What diameter range is available for stainless steel round bars?
A: Standard production ranges are: hot-rolled bars 10–500 mm diameter, cold-drawn bars 3–100 mm, centerless-ground bars 5–150 mm, peeled/turned bars 20–500 mm, and forged bars 50–800 mm. Polished (bright) bars are typically 3–80 mm. Custom diameters outside these ranges may be available as special orders. Lengths are typically 3–6 m random, with cut-to-length services widely offered.
Q: How do I choose between 316 and 316L stainless steel round bars?
A: The key difference is carbon content: 316 has ≤0.08% C, while 316L has ≤0.030% C. The lower carbon in 316L prevents sensitization (carbide precipitation) during welding, which otherwise degrades intergranular corrosion resistance in the heat-affected zone. For welded construction and pressure vessels, 316L is the standard choice. For non-welded applications where higher as-annealed strength is beneficial, 316 may be preferred. Both grades have nearly identical PREN (≈ 26).
JN Alloys (Jinie Technology Jiangsu Co., Ltd.) is a leading manufacturer and supplier of stainless steel, duplex, and nickel alloy products based in Wuxi, China. With extensive inventory, advanced processing capabilities, and strict quality control, we deliver round bars that meet the most demanding international standards.
•Comprehensive grade selection: Austenitic, duplex, martensitic, PH, and nickel alloy round bars in stock
•Full dimensional range: 3 mm to 500 mm diameter, hot rolled, cold drawn, centerless ground, and polished
•Strict quality assurance: EN 10204 Type 3.1 certificates, full traceability, PMI, ultrasonic testing
•International standard compliance: ASTM, EN, AMS, GB/T certified products
•Custom processing: Cut-to-length, peeling, grinding, polishing, and heat treatment services available
•Global logistics: Reliable worldwide shipping with export packaging per standard requirements
•Technical support: Experienced team providing grade selection guidance, material recommendations, and documentation
