AWS G2.5/G2.5M pdf free download

AWS G2.5/G2.5M pdf free download.Guide for the Fusion Welding of Zirconium and Zirconium Alloys.
3. Terms and Definitions
AWS A3.OM/A3.O. Standard Welding Terms and Definitions, Including Terms for Adhesive Bonding, Brazing, Soldering. Thermal Cutting, and Thermal Spraying, provides the basis for terminology used herein. However, the following terms and definitions are included below to accommodate usage specific to this document.
alpha grades or alloys. The alpha a) grades or alloys are generally weldable and nonheat treatable. They are materials with relatively large amounts of alpha stabilizers and low concentrations of beta (3) stabilizers. They are sometimes referred to as having predominantly an alpha phase. A common alpha alloy is commercially pure (CP) zirconium.
allotrope. An allotrope isa structurally different form of an element; graphite and diamonds are allotropes of carbon. As can be seen with the example of carbon allotropes. certain physical properties can vary dramatically from allotrope to allotrope. Alpha and beta allotropes of zirconium have very different properties. Alpha and beta allotropes are also referred to as phases.
alpha phase. The low-temperature allotrope of zirconium with a hexagonal close-packed (HCP) crystal structure.
alpha stabilizer. An alloying clement that dissolves preferentially in the alpha phase and raises the alpha-beta transformation temperature. Typical alpha stabilizers, such as aluminum, oxygen. tin, and nitrogen. increase the temperature at which the alpha phase is stable.
beta phase. The high-temperature allotrope of zirconium with a body-centered cubic (11CC) crystal structure that occurs above the beta transus.
beta transus. The minimum temperature above which equilibrium alpha does not exist.
body-centered cubic (BCC). A unit cell that consists of atoms arranged at cube corners with one atom at the center of the cube. This is the typical crystalline structure of the beta phase of zirconium.
embrittled (or enibrittlenient). The severe loss of ductility andlor toughness of a material, usually a metal or alloy. An example of embrittlement is when too much oxygen is introduced into the weld during welding causing the weld to become embrittled.
hexagonal close-packed (HCP). A unit cell that consists of a hexagonal arrangement of atoms on a plane and surrounding an atom followed by three atoms in the next horizontal plane. This last plane is otIset from the initial plane atoms. followed by an identical planar location of atoms above this. If the first plane is A and the second is B, then the repetitive arrangement of atom planes is A-B-A-B-A-B and so on. This is the typical crystalline structure of the alpha phase of zirconium.
interstitial elements. An element with a relatively small atom IhaL can assume a position in the interstices of the zirconium lattice. Common examples are oxygen, hydrogen, nitrogen, and carbon.
substitutional elements. To increase the strength of zirconium metal and still maintain useful ductility, substitutional elements are employed. These elements replace zirconium atoms in the lattice structure rather than situate in the voids between them, as do the interstitial elements.
Common CPI applications include pressure vessels, heat exchangers, piping, tanks, mixers, valves, pumps, and tower packings. Zirconium is available in many wrought product configurations, and it can be readily cast and formed to produce various shapes. With proper cleaning procedures and ample gas shielding coverage, zirconium can be welded into structures with traditional processes such as gas tungsten arc welding (GTAW), plasma arc welding (PAW), and gas metal arc welding (GMAW).AWS G2.5/G2.5M pdf download.