FabDigitFabDigit

Cast Steel

Cast steel is carbon or low-alloy steel poured to shape — sand, shell or investment cast — and then normalized or quenched and tempered like the equivalent wrought grade. It fills the gap cast iron cannot: valve bodies and pump casings that must be welded and pressure-tight (WCB, WCC, GP240GH), impact-loaded crane, rail and mining parts (A27 Grade 70-36, ZG270-500, G20Mn5), and heavy gear blanks and housings in alloy grades (ZG42CrMo, G42CrMo4) heat-treated to 300–400 HBW. Typical carbon cast steel gives about 250–300 MPa yield and 20 % elongation; alloy castings reach 700 MPa and above.

Popular cast steel grades

Compare in the explorer
GradeYield, MPaTensile, MPaDensity, g/cm³MachinabilityWeldabilityBest for
WCB2905207.85GoodVery goodGeneral-purpose valve and pump castings to 425 °C
WCC3155407.85GoodVery goodHigher-strength, more weldable WCB
LCB2855007.83GoodVery goodLow-temperature valve bodies to −46 °C
WC93305307.85FairFair2¼ Cr-1 Mo castings for hot steam service
CA6NM6908307.7FairVery good13 Cr-4 Ni turbine runners and pump impellers
A27 Grade 70-362905157.85GoodVery goodCarbon machinery castings, 250 MPa yield
ZG270-5003005407.83GoodVery goodGB carbon casting for general machinery

All 105 cast steel grades

Choose cast steel for

Valve bodies, pump casings and pressure-retaining housings that must be welded and code-certified; crane hooks, rail bogie parts, mining and crushing components that see impact; large gear blanks, wheels, sprockets and machine frames whose shape is too complex to forge and whose loads are too high for cast iron.

Look elsewhere when

The part is a base, housing or bracket loaded in compression with no impact (Gray Iron is cheaper, damps vibration and machines better), it needs steel-like ductility without weldability (Ductile Iron at 60-40-18 or 80-55-06 is the usual answer), the quantity justifies forging (a forged 4140 or 42CrMo4 blank has no porosity and better fatigue life), or it must resist corrosion (cast stainless CF8M or CA6NM).

Yield strength against elongation at break, Cast steel among every steel grade

No materials in view have both of these properties.

Loading the library…

Cast steel by application

Valves, pumps and flanges
WCB for most; WCC where weld repair is expected; LCB / LCC for cold, WC6 / WC9 / C12A for hot lines. All are bought to ASTM A216, A352 or A217 with pressure-tightness and radiographic acceptance levels stated on the drawing.
Impact-loaded machinery
A27 Grade 70-36, ZG270-500, G20Mn5 and GS240 normalized carbon castings for hooks, brackets, bogie frames and crusher parts; ASTM A148 or ZG310-570 when yield above 350 MPa is needed.
Heat-treated gears, wheels and shafts
ZG35CrMo, ZG42CrMo, G42CrMo4 and G34CrMo4 quenched and tempered to 28–40 HRC; carburize G20CrMo / ZG20CrMo for hardened teeth on a tough core.
Water turbines and wet abrasion
CA6NM (13 Cr-4 Ni) for runners, impellers and wicket gates; ZG30CrMnSi and ZG35CrMnSi for high-strength wear parts that still need weld repair.

Working with cast steel

Machining
Normalized carbon castings machine like hot-rolled 1020–1030 once through the skin, but the surface carries sand, scale and hard spots — take a first cut of at least 3 mm and expect variable stock from pattern allowance. Alloy castings are machined in the annealed or normalized state and finished after heat treatment; CA6NM is tough and gummy and cuts like a martensitic stainless.
Welding
One of the main reasons to choose cast steel: WCB, WCC and the carbon machinery grades weld like their wrought equivalents (ER70S-6 / E7018, preheat above about 25 mm), and foundries routinely weld-repair shrinkage and inclusions before heat treatment. Cr-Mo castings need matched filler, preheat and post-weld heat treatment; CA6NM is welded with ER410NiMo and tempered at about 600 °C afterwards.
Heat treatment
Almost every cast steel is heat-treated — normalize (or normalize and temper) for the carbon grades to refine the coarse as-cast structure, quench and temper for the Cr-Mo and alloy grades. The casting is heat-treated before final machining; section thickness varies across the part, so the heat-treater needs the drawing, not just the grade.
Inspection and quality
Specify the acceptance level, not just the grade: radiography (ASTM E446 / E186 severity level), magnetic particle or dye penetrant on machined faces, and a hydrostatic test for pressure parts. Porosity that opens up in machining is the common failure; state whether weld repair is allowed.

Other steel series

Cast Steel — frequently asked

What is cast steel?

Cast steel is carbon or low-alloy steel poured to shape — sand, shell or investment cast — and then normalized or quenched and tempered like the equivalent wrought grade. It fills the gap cast iron cannot: valve bodies and pump casings that must be welded and pressure-tight (WCB, WCC, GP240GH), impact-loaded crane, rail and mining parts (A27 Grade 70-36, ZG270-500, G20Mn5), and heavy gear blanks and housings in alloy grades (ZG42CrMo, G42CrMo4) heat-treated to 300–400 HBW. Typical carbon cast steel gives about 250–300 MPa yield and 20 % elongation; alloy castings reach 700 MPa and above.

Which grade of cast steel should I use?

WCB (ASTM A216) is the general-purpose pressure casting for valves, pumps and flanges to about 425 °C; WCC is its higher-strength, lower-carbon sibling with better weldability. For service below −29 °C move to LCB or LCC (ASTM A352 LCC, impact-tested at −46 °C), and to ASTM A352 Grade LC3 (3½ % Ni) near −100 °C. Hot service uses the Cr-Mo grades WC6 (1¼ Cr) and WC9 (2¼ Cr) to about 590 °C and C12A (9 Cr, the cast counterpart of P91) beyond that; CA6NM is the 13 Cr-4 Ni martensitic casting for hydro turbines and pump impellers. General machinery castings are A27 Grade 70-36, ZG270-500, GS240 or SC450 — plain carbon, normalized, weldable — with ZG310-570 and the ASTM A148 grades when higher strength is needed, and ZG35CrMo, ZG42CrMo or G42CrMo4 for quenched-and-tempered gears, wheels and shafts.

Which grade of cast steel is the strongest?

ZG55SiMnMo has the highest yield strength in the series at 1,300 MPa; G32NiCrMo8-5-4 follows at 880 MPa. Values are for each grade's default condition.

Which grade of cast steel is easiest to machine?

A216 WCA (machinability good, 68/100), then GE200 (65/100).

Is cast steel heat-treatable?

Yes. These grades gain their strength from heat treatment; the conditions and their properties are listed on each grade page.

WCB or LCB?

Same class of carbon casting, different tests: WCB (ASTM A216) is specified for service from −29 °C to 425 °C with 250 MPa minimum yield and no impact test; LCB (ASTM A352) has the same strength but is normalized and Charpy-tested at −46 °C for cold service such as refrigeration, cryogenic liquids and arctic pipelines. LCC and WCC are the lower-carbon, higher-strength (275 MPa yield) versions with better weldability. Choose by the minimum design metal temperature on the data sheet.

Cast steel or ductile iron for a housing?

Ductile Iron (65-45-12 or 80-55-06) is cheaper to cast, machines faster and damps vibration, and its 310–380 MPa yield covers most housings and brackets. Cast steel wins when the part must be welded (to itself or into a fabrication), when impact or fatigue loading at low temperature is severe, when the section is very thin or very thick and the iron would not form graphite uniformly, or when a pressure code requires a steel grade. For a gearbox housing or machine base, ductile or gray iron is normally the better answer.