Clasificación de aceros Flashcards
¿What is alloyed Steel?
Steels with significant amounts of alloy elements, are called alloyed steels. They are usually manufactured more carefully than carbon steels. Alloyed steels structural grade are used especially on the construction industry and transportation, because of their higher resistance. Other alloyed steels are used in appliances that require resistance, hardeness, creep resistance and fatigue, these alloyed steels can be treated thermally to get the desired properties
High strenght and low alloy steels
Multiple high resistance and low alloy steels with low carbon content (usually with less than 0.30 porcent) have been developed (HSLA). They are characterised by a consistent microstructure at a fine ferrite grain stage and a second martensite and austenite stage. Developed in the early 30’s, HSLA steels are commonly manufacured in the form of sheets through microalloying and controlled hotrolling. Plates, bars and structural forms are manufactured from these steels. However, HSLA steels’ ductility, formability and weldability are often inferior compared to conventional low alloyed steels. HSLA steel sheets are typically used in car bodywork components and other transport equipment (to reduce weight, and therefore, fuel consumption), in mining, agriculture and various industrial applications. HSLA plates are also employed in boats, bridges, building construction and many forms, such as “L” beams, gutters and angles used in buildings and other structures.
Microalloyed steel
They have a ferrite pearlite microstructure with dispersed carbon nitride fine particles. Although numerous microalloyed steels have been manufactured, the characteristic one posessess 0.5 porcent of carbon, 0.8 porcent of manganese and 0.1 porcent of vanadium. When they are subjected to a carefully controlled cooling (generally aired), these materials develop an improved and uniform strenght. Tempering manufacturing process, tempering and booster relays are not required, it is also noted that the need for heat treatment can be removed too.
Nannoalloyed steel
These steels have a very small grain size (10 to 100 nanometre) and are manufactured trough amorphous metal as a precursor. The amorphous metal is subjected to carefully controlled vitrification process at a very high nucleation speed, resulting in thin layers at a nanometric scale.
