Austenitic stainless steel / Grade data sheet

Z3CND18-12-02 Forgings Rings, flanges, bars, discs and shafts, open-die forged to drawing from steel melted on site

Z3CND18-12-02 is a French AFNOR grade name for a low-carbon, molybdenum-bearing austenitic stainless steel listed in NF A 35-574. The composition runs carbon 0.030 % max, chromium 16.50 to 18.50 %, nickel 10.00 to 13.00 % and molybdenum 2.00 to 2.50 %. The European cross reference is X2CrNiMo17-12-2 (1.4404), and for forgings in pressure service it is X3CrNiMo18-12-3 (1.4449). The grade is also written Z3CND18.12.02.

Jiangyin Jiangnan Metal Co., Ltd. melts and forges this grade in one works at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. Stainless heats run through the electric arc furnace, ladle furnace and vacuum oxygen decarburisation, then move to the presses, the ring mill, the heat-treatment furnaces and the machine shop without leaving the site, so traceability runs from melt number to shipped part.

Z3CND18-12-02 follows the older French AFNOR naming rules rather than the EN number system. The leading Z marks a high-alloy steel. The figure 3 stands for roughly 0.03 % carbon. C, N and D are the French initials for chromium, nickel and molybdenum, and the figures that follow give their nominal levels of 18, 12 and 2 %. So the grade is an 18Cr 12Ni 2Mo low-carbon austenitic stainless steel. Buyers write it both with hyphens and with dots, and both spellings mean the same material.

Sulphur here carries a minimum as well as a maximum, 0.015 to 0.030 %, which points to a free-machining variant. If low-sulphur material is needed for welding or for a polished finish, state the sulphur maximum you require. Because the steel is melted on site, the heat can be aimed at the tighter range rather than accepted as delivered.

The split matters at order stage. For bar, plate and general product, 1.4404 and 316L data applies closely. For a pressure-retaining forging the cross reference moves to 1.4449, which sits at a slightly higher carbon and molybdenum band, so the two are not interchangeable on a pressure-vessel order without checking the governing code. EN 10222-5 is the European standard for stainless steel forgings for pressure purposes and covers 1.4404 within its scope. Which route your order is certified against is confirmed in writing before billet is cut.

Property requirements under NF A 35-574 are not published in the open grade databases in a form worth quoting as acceptance values. The table below gives the ASTM A240 Type 316L minimums instead, as a working reference for the matching 1.4404 and 316L composition in the solution-annealed condition.

Published 1.4404 data gives a typical as-delivered range of 170 to 230 MPa yield, 480 to 620 MPa tensile and 40 % or more elongation. The values a given forging is accepted against depend on section size, the governing standard and where the test piece is taken, and are fixed in the approved inspection and test plan. Tensile testing runs in-house on 600 kN and 300 kN machines to ASTM A370 and ISO 6892.

Melting

Stainless and duplex grades run through a 25 t electric arc furnace, are refined in 25 t and 50 t ladle furnaces, and are decarburised under vacuum in 30 t or 60 t VOD units where low carbon and tight nitrogen control are needed, which is exactly the case for a Z3 grade held at 0.030 % carbon. Protective-atmosphere electroslag remelting at 3 t and 6 t is available where the drawing or the code calls for better cleanliness and less segregation. Maximum heat size is 60 tonnes.

Forging and ring rolling

Billets are upset and drawn on 6,300 t, 4,000 t and 2,000 t hydraulic presses, backed by 5 t, 3 t, 2 t, 1 t and 750 kg hammers for drawing out and small-batch work. Ring blanks are pierced and expanded on radial-axial mills of 6 m, 3 m and 1 m, giving a maximum rolled outside diameter of 6,000 mm. Rings smaller than the mill range are made by the upset-and-punch route from OD 50 mm. Austenitic stainless grades work-harden quickly and have a narrower hot-working window than carbon steel, so finish temperature is controlled and the piece reheated between passes rather than forcing the reduction through in one heat.

Heat treatment

Supply condition is solution annealed, written +AT in the EN delivery-condition system, with rapid cooling in water or air. Published 1.4404 data gives a solution-annealing range of about 1030 to 1110 degrees C, and where your specification states a range the works follows that range. Fourteen furnaces cover the grade, including car-bottom furnaces up to 8,000 x 2,000 x 2,000 mm working chamber and two 15,000 mm deep well-type furnaces that allow long shafts to be quenched vertically. With carbon held at 0.030 % max, chromium-carbide precipitation at grain boundaries during welding is much reduced compared with standard-carbon 18-12-2 material.

Work is made to drawings rather than to a catalogue. Minimum order is 10 kg with no minimum piece count, so a single small part is quotable and so is a one-off large ring. Forgings can be supplied as-forged with machining allowance, rough-machined to a proof-machined condition suitable for ultrasonic testing, or finish-machined to drawing.

A low-carbon 18Cr 12Ni 2Mo austenitic stainless steel gets specified where chloride-bearing or mildly acidic media would attack a plain 18-8 grade, and where parts are welded without a solution treatment afterwards. Forgings in this grade go into chemical and petrochemical plant, covering pressure vessels, tanks, heat exchangers and piping systems. Other common areas are petroleum refining and catalytic recovery equipment, pulp and paper plant such as digesters, liquor tanks and paper machine parts, food processing and storage equipment, pharmaceutical production, waste-treatment thermal oxidisers, and offshore and onshore oil and gas hardware including compressor, generator and nitrogen-generator components. In valve work the grade is used for bodies, bonnets, seat rings, stems and blocks in ball, gate, globe, check and plug valves.

The works holds CCS, BV, DNV, LR and NK classification society approvals and runs its own laboratory. Because the steel is melted here, chemistry is verified at the furnace rather than taken from a supplier certificate.

Supporting records supplied with the certificate include heat-treatment charts, NDT reports, dimensional reports and PMI records, with traceability from melt number through forging, heat treatment and machining to shipment.