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The Basics of Ferrous Metallurgy

102 Articoli

Carbide Free Bainitic (CFB) Steels: Part Two

Development of third generation, advanced high strength steels (AHSS) is well underway and is focused on advancements to provide even more superior strength-ductility ratios than in the currently available materials such as dual phase or TRIP steels.
One of the key features of carbide free bainitic steels is the numerous processing options such as drawing potential that are possible because of the increase in wear resistance and surface hardness that directly linked to the microstructural characteristics.

Characteristic of alloying elements

Very important elements for alloy steels are manganese, nickel, chromium, molybdenum, vanadium, tungsten, silicon, copper, cobalt and boron. All commercial steels contain 0,3-0,8% manganese, to reduce oxides and to counteract the harmful influence of iron sulphide. There is a tendency nowadays to increase the manganese content and reduce the carbon content in order to get a steel with an equal tensile strength but improved ductility. Nickel and manganese are very similar in behaviour and both lower the eutectoid temperature. Nickel steels are noted for their strength, ductility and toughness, while chromium steels are characterized by their hardness and resistance to wear.

Clean Steel: Part One

Steel cleanliness is an important factor of steel quality and the demand for cleaner steels increases every year. The so-called clean steel generally is the steel in which the content of impurity elements, such as phosphorus, sulphur, total oxygen, nitrogen, hydrogen (including carbon sometimes) and inclusions are very low. The improvement of steel cleanliness has therefore become a more and more important subject in the development of ferrous metallurgical technology, and also an important task for the iron and steel producers.

Clean Steel: Part Three

The presence of non-metallic oxide inclusions is a major cause of incompatibility between the attainable and desirable level of cleanliness in many grades of commercial steel. Generally, inclusions degrade the mechanical properties of the steel and thereby reduce the ductility of the cast metal and increase the risk for mechanical and/or corrosion failure of the final product.

Clean Steel: Part Two

Non-metallic inclusions, which are undesirable components of all steels, play an important role with respect to their effect on the steel properties. Controlling inclusions in steel is closely connected with the concept of "clean steel".
The improvement in steel properties by control of non-metallic inclusions plays an important part in defending the applications of steel against newer competitive materials.

CMnAlSi TRIP Steels: Part One

Continued material development in the automotive has given rise to a new generation of HSLA grades which are characterized by excellent strength and high ductility levels.
Studies of microstructure changes in high strength CMnAlSi steel after austenitization show that it is not possible to obtain a fully austenitic region with the addition of Al or Si higher than about 1.5% and actually these two elements strongly stabilize ferrite.