Steel casting and molding - General

Today, steel is the most widely used material in the world, consuming almost a billion tonnes a year. Traditionally, a distinction is made between wrought and cast steel. Cast steel, which accounts for around 10% of total production, is a relatively recent material whose industrialization corresponds broadly to the industrial revolution of the 19th century.

In steel casting, parts are obtained directly by solidifying the liquid metal in impressions (or molds) made of refractory or metallic material, which reproduce as closely as possible the final shapes and dimensions of the parts requested by users. This "near-net-shape" practice is both technically and economically advantageous, as it eliminates the need for costly subsequent machining operations, while preserving the raw foundry skin, which generally features a fine microstructure conducive to good part life. Wrought products, on the other hand, are made from liquid steel cast in the form of ingot or continuous casting blanks. These blanks are then shaped by rolling or forging, before being machined and assembled to produce the final product.

Cast steels are characterized by a wide variety of chemical compositions. They are made from alloys based on iron, carbon, silicon and manganese, to which other alloying elements such as chromium and nickel may be added to give them special properties, and they are used in a wide variety of applications. Standardization defines three main families of cast steels:

• carbon steels (generally 0.15 to 0.50% C);

• low-alloy steels in which the content of each alloying element is less than 5% (Mn, Ni, Cr, Mo, or even V, Cu, Nb, etc.);

• high-alloy steels in which the content of at least one alloying element exceeds 5% (Cr, Ni, Mn).

Nickel- and cobalt-based cast alloys are often classified as cast steels, as they are generally produced in steel foundries.

Another feature of cast steel is the structure of the foundries and the diversity of the production facilities, which make the manufacturing process highly flexible and adaptable, enabling parts of complex shapes and dimensions to be produced, individually or in series, as close as possible to the final dimensions.

For example, the following features are particularly noteworthy:

• dimensions: a few centimetres to ten metres;

• weight: from a few grams to several hundred tons;

• design, with the aim of improving aesthetics (architecture);

• Progressive shapes to reduce stress concentrations compared...