Glossary of terms used in galvanizing of steel...

Glossary of terms used in galvanizing of steel Galvanizing is carried out to protect steel against corrosion. The process is carried out in several steps as shown in Fig 1. Fig 1 Steps in the process of galvanizing  The common terms used in galvanizing of steel are given below. Abrasion resistance – It is the ability of the galvanized coating to resist damage caused by contact with hard, rough, or coarse media or objects. Abrasive blasting – It is the process of using a forceful stream of particles, available in varying hardness, to remove residue and contaminants from steel surfaces to prepare for galvanizing. Adherence – It is the act, action, or quality of zinc bonding to steel, measured in grams/Sq mm. Aggressive environment – It is an environment that is particularly corrosive. Alloy layers – It is the interior layers of the galvanized coating which comprised of iron/zinc intermetallics formed when molten zinc reacts with iron in the steel. Aluminum – It is the element found in the galvanizing bath (added to molten zinc through a product commonly called “brightener bar”) that gives the hot-dip galvanized coating a shiny appearance. Amphoteric – It is having the characteristics of an acid and a base and capable of reacting chemically either as an acid or a base. Anion – It is a negatively charged ion, especially the ion that migrates to an anode in electrolysis. Anode – It is the electrode of an electrolytic cell at which corrosion (oxidation) occurs, positive current flows from the anode through the electrolyte to the cathode. With respect to hot dip galvanizing, anode refers to zinc, which corrodes sacrificially to protect steel. Anodic – exhibiting of the properties of an anode. Zinc is anodic to steel. Application – It...

Glossary of terms used in heat treatment of steel...

          Glossary of terms used in heat treatment of steel Various terms used in the heat treatment of steels are described below: Ageing – It describes a time temperature dependent change in the properties of certain alloy steels. It is a change in properties that may occur gradually at atmospheric temperature (Natural ageing) and more rapidly at higher temperature (Artificial ageing). Quench ageing – It is a change in properties that may occur gradually at atmospheric temperature and more rapidly at higher temperature following rapid cooling (Precipitation hardening). Strain ageing – It is a change in properties that may occur gradually at atmospheric temperature and more rapidly at higher temperature following plastic straining. Annealing – It is a term denoting a treatment, consisting of heating to and holding at a suitable temperature followed by cooling at a suitable rate, used primarily to soften but also to simultaneously produce desired changes in other properties or in microstructure. The purpose of such changes may be, but is not confined to: Inducing softness Improving machinability Improving cold working properties Improving mechanical or electrical properties Increasing stability of dimensions Obtaining a desired structure Removing stresses The time temperature cycle used vary widely both in maximum temperature attained and in cooling rate employed, depending on the composition of the steel, its condition, and the result desired. Various types of annealing processes are as follows: Bright annealing– It is annealing in a protective medium to prevent discoloration of the bright surface. Cycle annealing – It is an annealing process employing a predetermined and closely controlled time temperature cycle to produce specific properties or microstructure. Flame annealing – It is an annealing process in which the heat is applied directly by a flame. Full annealing – It is heating to and...