304L Hot Rolled No.1 Stainless Steel Coil 3mm-12mm Low Carbon Welded Structural Pressure Vessel Grade SS Coil

Our 304L (UNS S30403) hot rolled No.1 finish stainless steel coil is engineered specifically for heavy-gauge welded fabrication applications where post-weld corrosion resistance must be guaranteed without post-weld solution annealing. The defining characteristic is the ultralow carbon content of maximum 0.03%, which fundamentally prevents intergranular chromium carbide precipitation (sensitization) that can occur in the weld HAZ of standard 304 during multi-pass welding of thick sections. The No.1 finish characterizes the surface condition after hot rolling, annealing, and pickling (HRAP), presenting a matte gray finish with typical surface roughness of 3-8um Ra, ideally suited for structural, industrial, and pressure vessel applications where subsequent surface finishing will be performed after welding and fabrication. Our 304L coils are produced through EAF with AOD refining for ultralow carbon control, continuous casting, hot rolling on a Steckel mill or continuous hot strip mill, in-line coil cooling, roller hearth annealing at 1050-1100C, and pickling in mixed nitric-hydrofluoric acid to remove scale and restore full corrosion resistance. Complete mechanical property testing per heat in both longitudinal and transverse orientations and hardness testing verify conformance to ASTM, ASME, and EN specifications.

• Guaranteed Freedom from Weld Sensitization: The max 0.03% carbon content ensures that the time-temperature exposure in the weld HAZ (500-850C for several seconds to minutes) is insufficient to nucleate chromium-rich M23C6 carbides at grain boundaries. IGC testing per ASTM A262 Practice E consistently passes without intergranular attack for 304L welded specimens, confirming immunity to sensitization that eliminates post-weld solution annealing requirements for heavy section fabrications.
• ASME Boiler and Pressure Vessel Code Compliance: 304L is fully approved under ASME Section II Part A (SA-240) with allowable stress values of 115 MPa at 100C, 94 MPa at 200C, and 82 MPa at 300C per ASME Section II Part D Table 1A. The combination of low carbon chemistry and ASME code acceptance makes 304L the default austenitic specification for welded pressure vessels, storage tanks, and process equipment where post-weld heat treatment is impractical or uneconomical.
• European PED Compliance: Our 304L coils are produced under EN 10204 Type 3.1 certification supporting compliance with PED 2014/68/EU. Material is fully traceable to PMA or EAM where required for pressure equipment categories II through IV. The combination of ASME and PED compliance facilitates global procurement for multinational EPC projects requiring dual-certified material.
• Excellent Machining and Fabrication Characteristics: The annealed No.1 finish surface provides an excellent starting condition for subsequent machining, grinding, and surface finishing. The hot rolled microstructure features equiaxed austenite grains with uniform size of ASTM 5-7 and no residual cold work, providing consistent machining behavior without the variable work hardening of cold rolled tempers. For heavy-gauge forming, the lower yield strength reduces springback and forming forces.
• Thick-Gauge Availability in Coil Form: Our hot rolling capability enables production of 304L coils in thickness from 3mm to 12mm, bridging the gap between cold rolled sheet/strip (typically up to 6mm) and discrete plate products (starting from 6mm). The coil format provides significant material yield advantages through continuous processing (blanking, slitting, cut-to-length) compared to discrete plate processing, reducing waste and per-unit costs for high-volume production.
• Good Elevated Temperature Properties: 304L maintains useful mechanical properties for non-pressure boundary applications up to 425C continuous service. The minimum 0.2% proof stress at 200C is approximately 130 MPa, declining to ~105 MPa at 400C. For ASME code-stamped pressure vessels, max design metal temperature is limited to 425C due to potential sigma phase embrittlement. For higher temperatures, stabilized grades such as 321 or 347 should be considered.
• Comprehensive Nondestructive Testing Capabilities: Beyond standard mill testing, we offer UT per ASTM A435/A435M (straight beam) and ASTM A577/A577M (angle beam) for internal soundness verification, liquid penetrant testing per ASTM E165 for surface integrity, and portable XRF/OES PMI for on-site chemistry verification. These testing services support material certification requirements of critical welded fabrications in regulated industries.

304L hot rolled No.1 finish coils are the material of choice for heavy-gauge welded fabrication across process industries. Primary applications include pressure vessels and storage tanks (chemical, pharmaceutical, food and beverage, water treatment, cryogenic storage), structural fabrication (building framework in corrosive environments, industrial flooring, chemical plant walkways), heavy equipment manufacturing (reactor bodies, autoclave shells, digester vessels, cement kiln components), shipbuilding (chemical tanker cargo tanks, coastal vessel hull plating, deck equipment), architectural and infrastructure (bridge structural components, tunnel lining panels, water treatment structural steel), and heat exchanger components (tube sheets, baffles, shell bodies, channel heads). The combination of low carbon immunity to sensitization, ASME/PED code compliance, and thick coil format availability makes 304L the preferred specification whenever shop or field welding of heavy sections is the primary manufacturing process.

Heavy-gauge 304L coils receive robust protective packaging with VCI anti-corrosion paper, heavy-duty waterproof polyethylene film with heat-sealed seams, high-tensile steel strapping (minimum 4 circumferential plus radial orientation), and heavy-duty edge protection rings. Coils over 8 tons on welded steel cradles with integrated fork pockets and crane lifting points. Container stowage with engineered timber blocking, pneumatic dunnage bags, and rated lashing chains. Each coil has a weatherproof ID tag. Complete EN 10204 Type 3.1 certification with PMI reports, UT certificates, and Type 3.2 independent inspection agency certification available for critical applications.