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The Basics of Ferrous Metallurgy

102 Articoli

Relation between CE structure and mechanical properties

A useful first attempt to relate composition and structure was shown in Fig. 3 of the article Cast Irons but it had limited use in the foundry. Figure 1 shows a more useful relationship between CE value, structure, tensile strength in 30 mm dia bars and section size. A cylindrical test bar of given dia cools more rapidly than a flat plate of equivalent thickness, hence the section is expressed as bar diameter or section thickness. Line H is the boundary of unmachinable irons while line P is the boundary between soft and pearlitic irons. Thus an iron of carbon equivalent 4,35 should not be made thicker than 20 mm as a bar or 10 mm as a plate to attain a pearlitic iron. To avoid an unmachinable chilled casting the bar should not be less than 8 mm dia or plate less than 4 mm thick.

Reoxidation of Steels

The internal cleanliness of steel is determined by the composition, size, number and distribution of its inclusions. It should be strictly controlled to ensure the castability of the liquid steel as well as the functional properties of the final product. The inclusions are formed during converter tap, ladle treatment and continuous casting of the steel and they can be oxides, sulfides and nitrides.
The oxides are formed by the reaction of dissolved reactive metals and oxygen, either dissolved in the steel or originating from the atmosphere, refractories or slags. Erosion of the refractories and slag dispersion can also be sources of new inclusions.

Residual Elements in Steel

Residual elements in steel—such as Cu, Ni, As, Pb, Sn, Sb, Mo, and Cr—are unintentionally present contaminants that cannot be eliminated through conventional metallurgical processes. These elements significantly influence mechanical properties and processing parameters throughout steel production. This article examines how residual elements affect steel processing conditions from casting to final annealing, distinguishing between elements that function in solid solution versus those that segregate at interfaces.

Semi-Austenitic Stainless Steels

Semi-austenitic stainless steels are just one of three groups of materials which are precipitation hardened steels, the others being martensitic and austenitic.
Some key characteristics of semi-austenitic stainless steels are high strengths, as well as high toughness, and corrosion resistance along with less favorable traits such as low fracture toughness in high strength conditions and low (subzero) temperatures.

Stainless steel

The stainless steels owe their resistance to corrosion to the presence of chromium. Brearley discovered this fact more or less accidentally in 1913. Today, there is a range of steels from the plain chromium variety to those containing up to six alloying elements in addition to the usual impurities.

Steel Deoxidation: Part One

This comprehensive examination of steel deoxidation processes explores the fundamental principles and practical applications of oxygen removal from molten metal. The article details various deoxidation methods, focusing on common deoxidizers such as manganese, silicon, and aluminum, while also discussing specialized deoxidants. It analyzes the paradoxical nature of deoxidation processes, equilibrium constants, and their practical implications in different steel grades.