PHYSICAL METALLURGY OF STEEL Chapter II

Like I said before, that Piping & Fabrication will continue this post of Physical Metallurgy of Steel Chapter II, and here we getting more and more of information of piping materials.

It is the effective use by the metallurgist of the knowledge contained on this and similar phase diagrams that allows for the manipulation of properties of engineering materials by varying their chemistry and heat treatment. For steel, the principal phases and their properties are briefly summarized in the following list:

Austenite: A single-phase solid solution of carbon in gamma iron (FCC). It exists in ordinary steels only at elevated temperatures, but it is also found at room temperatures, but it is also found at room temperature in certain stainless steels (e.g., 18 Cr–8 Ni type) classified as austenitic stainless steels. This structure has high ductility and toughness.

FIGURE A3.18 Iron-carbon equilibrium diagram

Ferrite: Alpha iron (BCC), containing a small amount of carbon (0.04–0.05 percent) in solid solution. This phase is soft, ductile, and relatively weak. Cementite: Iron carbide, Fe3C, a compound containing

PHYSICAL METALLURGY OF STEEL (chapter I)

After trying to make this mood back, I mean good mood, now I'll try to make one step ahead, even still I don't where to start but with Piping & Fabrication, I will try to be patient until that chance will comes to me. And now we discuss about Physical Metallurgy of Steel chapter I.

Like all other metals, iron and steel are crystalline in structure, composed of atoms in a fixed lattice. As noted earlier, iron may exist in one of two cubic forms, bodycentered (BCC) or face-centered (FCC).

At room temperature, pure iron is composed of a body-centered cubic lattice. In this form it is known as alpha iron, also called ferrite, which is soft, ductile, and magnetic.When heated above about 1415_F (768_C), alpha iron loses its magnetism but retains its body-centered crystalline structure. This temperature is called the Fermi temperature. The crystal structure changes to face-centered cubic at about 1670_F (910_C), at which temperature alpha iron is transformed to gamma iron, the FCC form, and remains nonmagnetic. As temperature rises further, another phase change occurs at 2570_F (1410_C), when delta iron is formed. This phase is again body-centered like that of the low-temperature alpha iron. It is stable to the melting temperature. In cooling very slowly from the liquid state, the phases reappear in reverse order.

The solid-state transformations of atomic structure,