The various heat treatment processes are discussed as follows: 1. Annealing 2. Normalising 3. Hardening 4. Tempering 5. Surface Hardening. 1. Annealing: The objects of annealing are: (i) To soften the metals. (ii) To improve machinability. (iii) To refine grain size due to phase recrystallisation. (iv) To increase ductility of metal. (v) To prepare steel for subsequent treatment. (vi) To [...]
In this article we will discuss about:- 1. Definition of Heat Treatment 2. Iron-Carbon Equilibrium Diagram 3. Theory of Heat Treatment of Steel 4. Martensitic Transformation (In Steel) 5. Critical Cooling Rate 6. Retained Austenite 7. Austenite Grain Size and Grain Size Control 8. Heat Treatment of Tool Steels 9. Alloy Steels and their Heat Treatment and Other Details. Contents: [...]
The various heat treatment processes are discussed as follows: 1. Annealing 2. Normalising 3. Hardening 4. Tempering 5. Surface Hardening. 1. Annealing: The objects of annealing are: (i) To soften the metals. (ii) To improve machinability. (iii) To refine grain size due to phase recrystallisation. (iv) To increase ductility of metal. (v) To prepare steel for subsequent treatment. (vi) To [...]
In this article we will discuss about:- 1. Introduction to Heat Treatment 2. Types of Phase Diagrams in Heat Treatment 3. Benefits of Alloy Hardening 4. Variables. Introduction to Heat Treatment: The properties of metals and alloys which are all so important to the engineer and the user, are intimately related to the micro-structure. Micro-structure is defined in a broad [...]
In this article we will discuss about:- 1. Introduction to Heat Treatment of Metals 2. History and Art of Heat Treatment of Metals 3. Process 4. Objectives. Introduction to Heat Treatment of Metals: Heat treatment is an endeavor to obtain the maximum efficiency of the material under the demanding conditions of service. Steel is an outstanding versatile engineering material, with [...]
The first step in any heat treatment cycle is to heat the parts to a predetermined temperature. The following are the principles of heating methods of metals and alloys: 1. Heat the parts in a furnace which has already been heated to the required heat treating temperature. The parts get heated up at a fast rate. Fig. 2.1 (a) illustrates [...]
The most commonly used operations of heat treatment for iron and steel are: 1. Annealing 2. Normalising 3. Hardening 4. Tempering 5. Carburising (Case-Hardening) 6. Cyaniding 7. Nitriding 8. Induction Hardening 9. Flame-Hardening. Operation # 1. Annealing: It is one of the most widely used operations in heat treatment of iron and steel and is defined (according to American Society [...]
Principal defects in steel due to heat treatment and measures for their elimination: Defect # 1. Overheating: Coarse grained micro- structure and fracture. Reduced ductility and specially reduced impact strength Causes: Heating for longer periods at temperatures considerably above the normal values. Prevention: i. For slight overheating, use normal annealing and normalising. ii. For considerable overheating, use double annealing or [...]
In this article we will discuss about the heat treatment of steel equipment in industries. Heat Treatment of Steel Castings: In most of the cases, steel castings must be subjected to a heat treatment. Only low quality castings made of low carbon steel may in some cases be used without being heat treated. Steel castings must be heat treated for [...]
The types of furnaces used for heat treatment depend on the type of heat treatment, the range of composition of steel and its size etc. Furnace may be heated by solid fuel (pulverised fuel), oil, dirty gas (producer gas), clean gas, or by electricity; the choice being wide and governed by economics. Furnace design also changes to meet the requirements [...]