If this deformation is done below the recrystallization temperature the process is known as cold wor. The grains within the structure recrystallise into many fine grains. Metal forming processes indian institute of technology. Hot working refers to the process where metals are deformed above their recrystallization temperature and strain hardening does not occur. Microstructure and mechanical properties of structural metals and alloys. Hot working of metals free download as powerpoint presentation. As a guideline, the lower limit of the hot working temperature of a material is 60% its melting temperature on an absolute temperature scale. The isodisc contributes to special heat tretment to improve the quality of the steel as wel as special forging technique to maintain the quality in the steel.
Metal forming is the main method of making metal products and semifinished products. Effect of hot working process on the mechanical properties of. Difference between hot working and cold working compare the. The division is on the basis of the amount of heating applied to the metal before applying the mechanical force.
In this case, forming is performed at temperatures just above room temperature but below the recrystallization temperature. Mechanical working processes which are done above recrystallisation temperature of the metal are know as hot working processes. Pdf microstructure and mechanical properties of structural. In hot forging steel, the weak and ductile fcc facecentered cubic austenite is deformed instead of the strong bcc bodycentered cubic ferrite which would deform at lower forging temperatures. During hot forging the metal is deformed plastically at elevated temperatures above recrystallization temperature into desired shapes by application of successive blows or continuous squeezing. Hot working hot working refers to the process where metals are defromed above their recrystallizat. The knowledge of metal forming rules permits to realize the forming at optimum deformation regimes. The ingot used for mw may contain defects pores, microcracks or inclusions which may remain as such or get aggravated during working operation. Following this are descriptions of heat treating, hot and cold working processes, and protection for metals.
Hot working hot working is the plastic deformation of metals above their recrystallization temperature. Free kindle book and epub digitized and proofread by project gutenberg. The work hardened metal is heated to a temperature which is about half its melting point. Hot working, as all metal forming processes, also has a set of disadvantages. Often, relatively small variations in inclusion contents or distributions may determine whether a steel can be successfully worked without cracking. Hot working is usually performed at elevated temperatures. Plastic deformation of metal carried out at temperature above the recrystallization temperature, is called hot working. Crane hook, connecting rod of ic engine, spanner, gear blanks etc. Hot working of metals extrusion rolling metalworking. Lead, however, is hot worked at room temperature because of its low melting temperature. You must have concluded that we cannot group elements according to their physical properties alone, as there are many exceptions. Cold working workpart shape can be significantly altered lower forces and power required metals that usually fracture in cold working can be hot formed strength properties of product are generally isotropic no strengthening of part occurs from work hardening advantageous in cases when part is to be. Forging is one of the oldest methods of working and can be done in hot, warm and cold modes.
Some metals, such as lead and tin, have a low recrystallisation temperature and can be hot worked even at room temperature, but most commercial metals require some heating. That is the ability to change without damage the shape and dimensions in hot and cold condition under the pressure of machining tools. Effect of hot working on the formation of structure and. The ultimate goal of metal hot working is to produce metal components of the required structural orientation and geometrical shape. The influence of stacking fault energy sfe on the mechanism of dynamic recrystallization drx during hot deformation of fcc metals is examined in the light of results from the power dissipation maps. Hot working occurs under conditions of temperature and strain rate such that recrystallization occurs simultaneously with deformation. Chapter 4 hot working and cold working explain the differences between cold, warm and hot working of metals the process for hot working is above the recrystallization temperature of the metal, meanwhile for cold working is below the recrystallization temperature of the metal. The upper limit for hot working is determined by various factors, such as. There are many other differences between these processes which are described as below. May 17, 2017 if this deformation is done below the recrystallization temperature the process is known as cold working. When plastic deformation of metal is carried out at temperature above the recrystallization temperature the process, the process is known as hot working. This mode is typical the material flow from the flange towards the. Apr 04, 2016 comparison between hot working and cold working processes can be done in aspects like carried out temperature, stress set up, tolerances, hardening, deformation, surface finish, improved properties, cracks formation. Introduction mechanical working of metal is defined as an intentional deformation of metals plastically under the action of externally applied force.
Defects metal working and rolled products defects in metal working process defects in the final product of mechanically worked metal may have originated from any one or a combination of the following. The drx domain for high sfe metals like al and ni occurred at homologous temperature below 07 and strain rates of 0001 s. Some examples of shapes obtained by forging process. Both hot and cold working methods are employed to work the metal however, hot working is different from cold working in the way that the end product of hot working is more ductile and less hard. Abstractthe detrimental effects of nonmetallic inclusions on the ductility of steel at hot working temperatures are well known. In comparison with the pwn, grains in pwr were much more elongated into a fiberlike structure with a very narrow grain width of. The process chosen for a particular application depends upon the metal involved and the part required, although in some instances you might employ both hot and cold working methods in making a single part. Involves deformation above recrystallization temperature, between 0.
Work hardened metals can be made more malleable and ductile again by a process called annealing. Metal casting process can be described as the process of making object by melting metal then poured into the desired mould. The metal working processes are derived into hot working and cold working processes. Metal forming processes indian institute of technology guwahati. Initially the definition and characteristics of warm working as pertaining to steels is discussed. Od1643 us army correspondence course program 6 credit hours general the purpose of this subcourse is to introduce the student to the properties of metals, their characteristics, uses and identification codes. Cold working and hot working of metals marine notes. This voltage is referred to as an emf electromotive force and can be measured and in turn used to indicate temperature. Those processes working above the recrystallization temperature are hot working processes where as the below or termed as cold working processes. This is followed by explanations of steel and nonferrous metals and their alloys which are now being used. Cast iron the cast irons are the ferrous alloys with greater that 2. Forging is a metal working process in which useful shape is obtained in solid state by hammering or pressing metal. Plastic properties of metals are used during the process of metal forming.
A section on the physical testing of aircraft metals completes the text. Download free acrobat reader dc software, the only pdf viewer that lets you read, search, print, and interact with virtually any type of pdf file. Effect of hot working on the formation of structure and properties in sintered metals. For example i all metals except mercury exist as solids at room temperature. Under the action of heat and force, when the atoms of metal reach a certain higher energy level, the new crystals start forming. Working in metals by charles conrad sleffel free ebook project gutenberg. Plastic deformation is a permanent deformation, and obtained by applying forces great enough to exceed.