it is about heat treatment process. types, advantages, disadvantages, Summaries of Metallurgy

Download it is about heat treatment process. types, advantages, disadvantages and more Summaries Metallurgy in PDF only on Docsity! Heat Treatment Processes Name ~: Himanshu Verma Year/Sem : 3% Year/5"Semester Branch =: Mechanical 1* Shift Roll No. : 13EEBME020 College : Govt. Engineering College Bikaner. Introduction . Heat Treatment * Heat Treatment process is a series of operations involving the Heating and Cooling of metals in the solid state. * Its purpose is to change a mechanical property or combination of mechanical properties so that the metal will be more useful, serviceable, and safe for definite purpose. * By heat treating, a metal can be made harder, stronger, and more resistant to impact, heat treatment can also make a metal softer and more ductile.  1. Annealing * Annealing is the process for softening materials or to bring about required changes in properties, such as machinability, mechanical or electrical properties, or dimensional stability. * The annealing process consists of heating the steel to or near the critical temperature (temperature at which crystalline phase change occurs) to make it suitable for fabrication. * A material can be annealed by heating it to a specific temperature and then letting the material slowly cool to room temperature in. an oven. ¢ When an annealed part is allowed to cool in the furnace, it is called a "full anneal" heat treatment. Austenite uF nealing range 00 02 04 66 08 10 12 14 16 18 20 Carbon, wit 2. Normalizing * It is a type of heat treatment applicable to ferrous metals only. * It differs from annealing in that the metal is heated to a higher temperature and then removed from the furnace for air cooling. * The purpose of normalizing is to remove the internal stresses induced by heat treating, welding, casting, forging, forming, or machining. * One drawback of using this method by itself is that the metal becomes brittle. This treatment is therefore typically followed by a tempering process which is a heating process at another lower specific temperature to stress relieve the material and minimize the brittleness problem. g 8 Temperature, °F 8 oO 123 45 6 7 8 9 OM 2 BD M4 15 16 Time, seconds Typical cooling curve for a small cylinder quenched in warm water  4. Case Hardening * Case Hardening is the process of hardening the surface of a metal, often a low carbon steel, by infusing elements into the material's surface, forming a thin layer of a harder alloy. * Case hardening improves the wear resistance of machine parts without affecting the tough interior of the parts.  5. Austempering * Austempering is heat treatment that is applied to ferrous metals, most notably steel and ductile iron. * In steel it produces a bainite microstructure whereas in cast irons it produces a structure of acicular ferrite and high carbon, stabilized austenite known as ausferrite. ¢ It is primarily used to improve mechanical properties or reduce / eliminate distortion.  7. Surface Hardening « Surface hardening, treatment of steel by heat or mechanical means to increase the hardness of the outer surface while the core remains relatively soft. * Surface-hardened steel is also valued for its low and superior flexibility in manufacturing. * The oldest surface-hardening method is carburizing, in which steel is placed at a high temperature for several hours in a carbonaceous environment. The carbon diffuses into the surface of the steel, rendering it harder. * Another method of surface hardening, called nitriding, utilizes nitrogen and heat. Cam shafts, fuel injection pumps, and valve stems are typically hardened by this process. * Flame hardening and induction hardening, in which high heat is applied for a short time (by gas flame or high-frequency electric current, respectively) and then the steel is immediately quenched, are used generally for larger implements. * Martempering also reduces or eliminates susceptibility to cracking. * Another advantage of martempering in molten salt is the control of surface carburizing or decarburizing. Temperaises g. Ausforming + Ausforming also known as Low and High temperature thermomechanical treatments is a method used to increase the hardness and stubbornness of an alloy by simultaneously tempering, rapid cooling, deforming and quenching to change its shape and refine the microstructure. Atmosphere furnace tempering ~. {using conventional heat treatment on eee furnace) ~ Ausforming & HOP rapid heating ‘and tempering (using HOP)