GB/T 4237 12Cr18Ni9Si3 S30240 Stainless Steel Plate Supplier

12Cr18Ni9Si3 is 302B: 2.00–3.00% silicon on an 18-8 base raises scaling resistance. Annex B states it matches 06Cr25Ni20 for oxidation resistance below 900 °C, which makes it a low-cost option for furnace and exhaust parts.

How to read the name: under GB/T 20878 the leading ’12’ is the carbon code (here C ≤0.15%), then Cr18 = about 18% chromium; Ni9 = about 9% nickel; Si3 = about 3% silicon. S30240 is the unified numeric code (ISC) used in GB/T 4237-2015. Older drawings and Chinese buyers may still write the pre-2007 name 1Cr18Ni9Si3.

SHH STEEL produces and exports austenitic stainless plate from China, works as a sales agent for leading stainless mills, and runs its own processing warehouse for cutting and surface finishing. 12Cr18Ni9Si3 is part of our GB/T 4237 stainless plate range; for comparison, see our AISI 302B page.

For hot service, 12Cr18Ni9Si3 competes with the other heat-resistant austenitics in GB/T 4237. Temperature limits below are typical industry guidance for clean, dry air, not values from the standard; sulfur, vanadium, chlorine and thermal cycling lower them.

Sigma phase forms in all of these grades during long exposure at 650–900 °C. It does not hurt hot strength much, but it makes the plate brittle at room temperature, which matters during shutdowns and maintenance.

Values are maximum unless a range is given. The mill reports the ladle (heat) analysis on the certificate; this is the figure to compare with Table 15.

A check analysis drilled from the finished plate may differ slightly from the heat analysis. GB/T 4237 refers to GB/T 222 for the permitted deviations; the table applies them to the 12Cr18Ni9Si3 limits. Deviations apply to one side of a range only, never to both sides in the same heat.

Where the table says ‘by agreement’, the deviation is not tabulated for that content level and should be agreed in the contract, usually by reference to ASTM A480 Table A1.1.

Values apply to plate in the delivery heat-treated condition, tested transversely per GB/T 228.1. Hardness is checked by one method chosen by the mill.

Recommended heat treatment for 12Cr18Ni9Si3 (GB/T 4237-2015 Annex C): ≥ 1 040 °C, water quench or other rapid cooling.

For hot service the plate is used in the solution-annealed condition; in-service ageing changes properties and is part of the design.

Equivalent grades are close in chemistry and properties but are never identical: limits on carbon, nitrogen and residual elements differ. For dual or multiple certification the heat must meet every standard named on the order, and we confirm that from the heat chemistry before quotation.

Related pages: AISI 302B. See also our ASTM A240/A240M and JIS G4305 plate lists.

Sister grades on the same standard are listed under GB/T 4237; cold-rolled sheet of the same chemistry is ordered to GB/T 3280, and all our plate lines sit in stainless steel sheets and plates.

Weld with matching filler (ER309/309L for 23-13, ER310 for 25-20, Ce-bearing fillers for the rare-earth grades) to keep oxidation resistance across the joint.

Fully austenitic weld metal is prone to hot cracking: keep heat input moderate, use convex beads and clean joints of sulfur, oil and paint. Avoid long holds at 650–900 °C before service where sigma phase can form.

Cutting: we cut 12Cr18Ni9Si3 by plasma (up to about 150 mm), laser (thin plate) or waterjet, and remove the heat-affected edge by machining where the drawing requires it.

The table compares 12Cr18Ni9Si3 with the grades buyers most often weigh it against. Strength values are GB/T 4237-2015 minimums; PREN is calculated from the minimum chemistry.

High silicon reduces hot ductility and makes welding more prone to hot cracking; use low heat input and an Si-tolerant filler such as ER308Si or ER309. Above 900 °C move to 06Cr25Ni20 or 08Cr21Ni11Si2CeN.

Hot-service applications:

• Industrial furnace parts and fixtures
• Automotive exhaust purification devices
• Heat treatment baskets and muffles
• Burner and boiler internals below 900 °C

Buyers specifying 12Cr18Ni9Si3 for these jobs often compare it with GB/T 4237 12Cr18Ni9 S30210 and GB/T 4237 05Cr19Ni10Si2CeN S30450; the comparison table on this page shows the differences.

International grade pages for the alternatives mentioned above: AISI 302, ASTM A240 Type 310S, ASTM A240 Type 309S, ASTM A240 Type 304H.

Our warehouse cuts plate to size (plasma, laser, waterjet, saw), bevels weld edges, polishes and applies PVC protective film. Processed plate ships with the original mill heat number marked. Ask for cut pieces of other stainless steel products at the same time to consolidate freight.

Weight: plate mass in kg/m² = thickness (mm) × density (7.98 g/cm³). A 10 mm 12Cr18Ni9Si3 plate weighs about 79.8 kg/m²; a 1 500 × 6 000 × 10 mm plate about 718 kg.

• Heat chemical analysis on every heat; product analysis by agreement
• Tensile test (Rp0.2, Rm, A) per batch
• Hardness test
• Ultrasonic testing (NB/T 47013.3 or ASTM A578) when specified
• Positive material identification (PMI) on every plate leaving our warehouse
• Visual and dimensional inspection; third-party inspection (SGS, BV, TÜV, Intertek) at the buyer’s request

Certificates follow EN 10204 3.1 as standard. Where plate is also certified to ASME SA240 or ASTM A240, both standards are shown on one certificate.

• Standard and edition: GB/T 4237-2015
• Grade and code: 12Cr18Ni9Si3 (S30240); add the equivalent if dual certification is needed
• Thickness × width × length, quantity in pieces or tonnes
• Thickness tolerance class and flatness if tighter than standard
• Surface finish and protective film
• Tests beyond the standard (IGC, UT, impact, ferrite, PMI, grain size)
• Certificate type (EN 10204 3.1 / 3.2) and inspection body
• Marking, packing (wooden cases, steel pallets) and delivery terms

Send the list to SHH STEEL and we return a quotation with mill, lead time and stock options. Other grades from the same standard can be combined in one shipment; browse GB/T 4237 plate grades.

12Cr18Ni9Si3 is produced by a small number of Chinese mills with the melting and heat treatment capability for it. We place mill orders for it through the producers we represent and do not usually hold it in stock. Expect about 45–90 days, with minimum quantities per thickness; we can combine small quantities into one rolling where the mill allows.

Every plate is traceable to its heat number, and copies of the mill certificates stay on file for repeat orders and audits. The same mills also supply our ASTM A240, ASME SA240, JIS G4305 and AISI plate ranges, so mixed-standard orders can ship together.

• Mill-direct prices with our own export documentation
• Own processing warehouse: cutting, bevelling, polishing, PVC film
• PMI and dimensional check before packing
• Mixed-grade shipments across our AISI stainless and GB/T plate ranges
• Technical answers from people who read the standard, not just the price list

SHH STEEL has exported stainless and carbon steel plate to buyers in Asia, the Middle East, Africa, Europe and the Americas.

GB/T 4237 12Cr18Ni9Si3 (S30240) is a heat-resistant austenitic plate grade, known internationally as 302B. It is defined by Table 15 chemistry (C ≤ 0.15, Cr 17.00 – 19.00, Ni 8.00 – 10.00, N ≤ 0.10, Si 2.00 – 3.00) and Table 20 properties of at least 205 MPa proof strength and 515 MPa tensile strength. Typical uses include industrial furnace parts and fixtures, automotive exhaust purification devices and heat treatment baskets and muffles. High silicon reduces hot ductility and makes welding more prone to hot cracking; use low heat input and an Si-tolerant filler such as ER308Si or ER309.

Before ordering, state the standard edition, the grade name with its code, and any extra tests, so that the mill certificate matches your design documents. SHH STEEL supplies 12Cr18Ni9Si3 plate by mill order through the producers we represent, cut to size and finished in our own warehouse, with EN 10204 3.1 certificates. For related grades see GB/T 4237 12Cr18Ni9 S30210 and GB/T 4237 06Cr25Ni20 S31008, our GB/T 4237 category and the AISI 302B page. Send your sizes and quantities for a quotation.