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  • Basic Metals & Alloys : Properties and Applications
    • Manufacturing Engineering
    • Manufacturing Process
    • Product Simplification and Standardisation
    • Computer Aided Manufacturing(CAM)
    • Product Development
    • Material Properties
    • Toughness and Ductility
    • Torsion
    • Fatigue and Creep
    • Ferrous Metals
    • Cast Iron
    • White cast iron
    • Malleable cast iron
    • Wrought Iron
    • Plain carbon steel
    • Heat resisting steels
    • Non-Ferrous metals
    • Brasses
    • Bronzes
    • Nickel and its Alloy
    • Transformation During Heating and Cooling of Steel
    • Normalizing and Annealing
    • Hardning and Tempring
    • Hot chamber die-casting

  • Introduction to Metal Forming & Casting Process and its applications
    • Introduction of Casting
    • Permanent Mold or Gravity Die Casting
    • Shell Mold Casting
    • Probable Causes and Suggested remedies of Various Casting Defects
    • Plastic Molding Processes
    • Introduction of forging
    • Forgeability and Forgable Matrials
    • Heating Devices
    • Open fire and stock fire furnace
    • Control of Heating Devices
    • Forging Operations
    • Hot Working of Metals
    • Hot Working
    • Classification of Hot Working Processes
    • Hot Extrusion
    • Hot Drawing and Hot Spinning
    • Comparison of Hot Working with Cold Working
    • Cold Working
    • Cold Working Process
    • Wire Drawing

  • Introduction to Machining & Welding and its applications
    • introduction to metal cutting
    • Cutting Tool
    • Mechanics of Metal Cutting
    • Introduction to Lathe Machine
    • Construction of Lathe Machine
    • Accessories and Attachments of Lathe
    • Specification of Lathe
    • Lathe Operations
    • Taper and Tapers Turning
    • Thread Cutting
    • Introduction to Drilling Machine
    • Types of Drilling Machine
    • Types of Drills
    • Twist Drill Geometry
    • Operations Performed on Drilling Machine
    • Operations Performed on Drilling Machine-Tapping
    • Shaper
    • Types of Shapers
    • Principal Parts of Shaper
    • Specification of a Shaper
    • Shaper Operations
    • Planer
    • Principle parts of a Slotter
    • Introduction to Milling
    • Types of Milling Cutters
    • Types of Milling Machines
    • Column and Knee Type Milling Machine
    • Indexing and Dividing Heads
    • Introduction to Welding
    • Welding joints
    • Welding Positions
    • Classification of Welding and Allied Processes
    • Gas Welding Processes
    • Gas Welding Equipments
    • Arc Welding Processes
    • Arc Welding Equipment
    • Resistance Welding
    • Resistance Seam Welding
    • Brazing

  • Manufacturing and Non-Metallic Materials
    • Plant layout
    • Types of Layouts
    • Line or Product Layout
    • Comparison of Line or Product Layout and Process or Functional Layout
    • Hard and Soft Wood
    • Felling, Conversion and Seasoning of Wood
    • Defects in Timber
    • Characteristics of a Good Timber
    • Ceramics materials
    • Powder-metallurgy process
    • Characteristic of Metal Powders
    • Advantages of powder Metallurgy
    • Electroplating
    • Galvanization
    • Plastics
    • Comparison Between Thermo Plastic and Thermosetting Plastic

Branch : First Year-Engineering Syllabus
Subject : Basic Manufacturing Process
Unit : Basic Metals & Alloys : Properties and Applications

Normalizing and Annealing


NORMALIZING: Normalizing is a defined as softening process in which iron base alloys are heated 40 to 50°C above the upper-critical limit for both hypo and hyper eutectoid steels and held there for a specified period and followed by cooling in still air up to room temperature. Fig 1 shows the heating temperature ranges for normalizing process of both hypo and hyper carbon steel. Fig. 2 shows the structure obtained after normalizing of medium carbon steel.

Objectives

  • To soften metals
  • Refine grain structure
  • Improve machinability after forging and rolling
  • improve grain size
  • Improve structure of weld
  • Prepare steel for sub heat treatment

Fig. 1 Heating temperature ranges for various heat treatment processes

ANNEALING: It is a softening process in which iron base alloys are heated above the transformation range held there for proper time and then cool slowly (at the of rate of 30 to 150°C per hour) below the transformation range in the furnace itself. Heating is carried out 20°C above upper critical temperature point of steel in case of hypo eutectoid steel and the same degree above the lower critical temperature point in case of type eutectoid steel. Fig 1 shows the heating temperature ranges for annealing or softening process of both hypo and hyper carbon steel. Fig. 3 shows the structure obtained after annealing of medium carbon steel. The structure of steel on slow cooling changes into ferrite and pearlite for hypo eutectoid steel, pearlite for eutectoid steel and pearlite and cementite for hyper eutectoid steel. The time for holding the article in furnace is ½ to 1 hour. As ferrous metals are heated above the transformation range, austenite structure will be attained at this temperature.
For a particular type of structure specific cooling rate is required to have good annealing properties for free machining. As metal is slowly cooled after heating and holding in and with the furnace and buried in non conducting media such sand, lime or ashes, carbon steels are cooled down at particular rate normally 150-200°C per hour while alloy steel in which austenite is very stable and should be cooled much lower (30°C to 100°C per hour). Very slow cooling is required in annealing to enable austenite to decompose at two degrees of super cooling so as to form a pearlite and ferrite structure in hypo-eutectoid steel, a pearlite structure in eutectoid steel and pearlite and cementite structure in hyper eutectoid steel. In successfully annealed steel, the grains of ferrite are large and regular while pearlite consists of cementite and ferrite. Hypo-eutectoid hot worked steel may under go full annealing to obtain coarse grain structure for free machining. When steel is cold worked the hardness (Brinell hard) considerably increases and ductility decreases slightly. The ductility of steel may be then restored by so called recrystallisation or process annealing.

Fig. 2 Structure of normalized Fig. 3 Structure of annealed
medium carbon steel medium carbon steel

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