Cast Steel And Forged Steel: Main Differences

Steel products can be manufactured by casting or forging steel. Cast steel is the process of heating a metal until it reaches a liquid state and then pouring it into a mold to form the desired product. Forged steel implies the application of mechanical force to heated solid steel blocks (such as ingots and/or billets) that are permanently formed into the desired product.

Steel Forging VS.The casting

Both manufacturing processes require the steel raw material to be subjected to high temperatures (to liquefy it or to make it malleable) and require CNC machining to be performed at the end of the process to obtain the final product.

The final product may also undergo surface treatment, such as spray painting, powder coating, polishing, various types of coating (e.g. galvanizing), and wear protection/hardening (for tungsten carbide overcoat applications).

Last but not least, castings and forgings can be assembled, soldered, brazed, and hard-faced before the final product leaves the factory.

Casting and forging processes produce products with different characteristics in terms of surface porosity (generally better than forged products), grain structure (finer for forged products), and tensile strength (generally better for forged products).

Therefore, these alternative manufacturing processes are used (and suitable) for different situations and applications.

The casting process is optimized for:

Parts and assemblies that are too complex or expensive to be forged from steel (e.g., large valve bodies);

Parts with a cavity;

Large parts (there is almost no size limit on the weight of parts that can be produced in the casting process);

Parts of special alloys (some special alloys are more difficult to forge than casting, for example, alloys with a high nickel and molybdenum content have considerable resistance to mechanical forces);

Parts that need to be produced in large quantities and in small quantities.

The forging process is suitable for:

Parts requiring extremely high strength, toughness, and resistance (in fact, during the forging process, the grain structure of the steel is modified to match the shape of the final product - with high composition uniformity and metallurgical recrystallization);

Parts that must withstand greater impact and mechanical force;

The risk of pores, bubbles, cavitation, and the possibility of forming cavities (or even particles) is not acceptable;

Producing mechanically strong parts without the use of expensive alloys;

Parts requiring high wear resistance;

Parts that bear high loads and stresses;

In high-end applications, part integrity and quality are the primary objectives in the production process, not time and cost.

The development of casting technology has narrowed the gap between the physical properties of casting products and forged products, making modern casting products extremely competitive in terms of quality, strength, and wear resistance: however, in many fields, steel forging still exists, preferred manufacturing options (e.g., small valves, such as forged or high-pressure valves).

According to the temperature applied to the raw material in the forging process, forging can be divided into:

Cold Forged Steel: When not heated, i.e. the forging process takes place at room temperature (higher mechanical force is required and the formability of the metal is lower than that of hot forging or warm forging methods).

Warm Forging Steel: The raw material is heated to a temperature between 800 and 950/1000 C°

Hot Forging Steel: When heated to temperatures above 950/1000 C° (usually below 1300 C°), metals have high ductility and can be forged even with moderate mechanical pressure.