Parts poured from molten stainless steel into sand or ceramic moulds, used where a shape is too complex to forge or machine economically — pump casings and impellers, valve bodies, marine and food machinery parts. The cast grades (CF8M, CF3M, duplex 4A and 5A, CA6NM) are the counterparts of the wrought ones and are specified by ASTM A351, A743, A744, A890 and EN 10283.
Casting lets a designer put metal exactly where it is needed — curved water passages in a pump, the internal shape of a valve body, a ship's fitting with bosses and lugs — with little machining. Stainless castings are poured from steel melted in induction or arc furnaces, often refined by argon-oxygen decarburisation (AOD) to bring the carbon down, then solution annealed and quenched to dissolve carbides and restore corrosion resistance.
Two moulding methods dominate. Investment (lost-wax) casting builds a ceramic shell round a wax pattern, melts the wax out and pours into the hot shell; it gives fine detail, thin walls and a good surface, and suits small parts such as impellers, fittings and hardware. Sand casting uses bonded sand moulds and cores and is used for larger valve and pump bodies. Centrifugal casting spins the mould and is used for rings, sleeves and pipe.
Cast grades have their own names. The Alloy Casting Institute system used in ASTM standards starts with C (corrosion resistant) or H (heat resistant), then a letter for the nickel level, then the maximum carbon in hundredths of a per cent, then letters for other elements: CF8M is the cast counterpart of 316, CF3M of 316L, CF8 of 304. Cast austenitic grades are designed with some ferrite in them, which improves weldability and strength but makes them slightly magnetic — a CF8M casting is not supposed to behave like a wrought 316 sheet under a magnet.
In the GCC, stainless castings go mainly into pumps and valves for desalination, water transmission and district cooling, into oil and gas equipment, and into food processing and architectural hardware. Seawater duty usually calls for duplex (ASTM A890 grade 4A or 5A) or super-austenitic CK3MCuN castings rather than CF8M. Most castings are imported from foundries in China, India and Europe, either as finished pumps and valves or as castings for local machining.
Castings are made to the buyer's drawing. The order states the grade and specification, the pattern (who owns it), dimensional tolerances, machining allowances, the heat treatment and the inspection level.
| Region | Standard | What it covers |
|---|---|---|
| USA | ASTM A351/A351M ASTM |
Castings, austenitic, for pressure-containing parts — CF3, CF3M, CF8, CF8M, CF8C, CN7M, CK3MCuN |
| USA | ASTM A743/A743M ASTM |
Castings, iron-chromium, iron-chromium-nickel, corrosion resistant, for general application — includes CA15 and CA6NM |
| USA | ASTM A744/A744M ASTM |
Castings, iron-chromium-nickel, corrosion resistant, for severe service |
| USA | ASTM A890/A890M ASTM |
Castings, iron-chromium-nickel-molybdenum corrosion-resistant, duplex (austenitic/ferritic) for general application — grades 1B, 4A, 5A, 6A |
| USA | ASTM A995/A995M ASTM |
Castings, austenitic-ferritic (duplex) stainless steel, for pressure-containing parts |
| USA | ASTM A781/A781M ASTM |
Castings, steel and alloy, common requirements, for general industrial use |
| Europe | EN 10283 CEN-CENELEC |
Corrosion resistant steel castings — GX5CrNi19-10 (1.4308), GX5CrNiMo19-11-2 (1.4408), GX2CrNiMo19-11-2 (1.4409) and others |
| Europe | EN 10213 CEN-CENELEC |
Steel castings for pressure purposes — includes austenitic and duplex stainless grades |
| International | ISO 8062-3 ISO |
Dimensional and geometrical tolerances for moulded parts — casting tolerance grades |
| Japan | JIS G5121 JSA |
Corrosion-resistant cast steels for general applications — SCS13 (CF8), SCS14 (CF8M), SCS16 (CF3M) |
Grade equivalents and the standards bodies: Steel grades & standards
Steel Mills - Agents & Traders · Stockist - Distributor · Other Steel Users · Riyadh
Steel Mills - Agents & Traders · Stockist - Distributor · Other Steel Users · Riyadh
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