Normally, as the tempering progresses, the hardness and the strength decrease, but the ductility and impact strength increase. But in certain steels, there is an unexpected decrease of the impact strength in certain ranges of temperatures as schematically illustrated in Fig. 7.13. This indicates that there are two main types of embrittlement during tempering: 1. Tempered martensite embrittlement (TME), 2. [...]
The following points highlight the seven main types of annealing of steels.They are: 1. Full Annealing 2. Homogenising (Diffusion) Annealing 3. Process Annealing 4. Spheroidisation Annealing 5. Partial Annealing 6. Bright Annealing 7. Stress-Relieving Annealing. Type # 1. Full Annealing: Full annealing, or annealing consists of heating the steel to a temperature above its upper critical temperature, soaking there for [...]
In this article we will discuss about:- 1. Process of Quenching 2. Characteristics of Quenching Media 3. Important Quenching Mediums 4. Quenching Stage. Process of Quenching: In hardening of steels, the rapid cooling rates may be obtained by bringing into contact, the hot surface of the object with some cooler material, which may he gaseous, liquid, or solid. This operation [...]
The following quenching methods are commonly used. The method to be adopted depends on the composition of steel, section thickness, distortion allowed, and properties to be imparted to the steel: 1. Direct Quenching 2. Delay Quenching 3. Interrupted Quenching 4. Bright Hardening. Method # 1. Direct Quenching: This is the most common method used in industrial practice. The properly austenitised [...]
Tempering of steels takes place in four distinct but overlapping stages: 1. First Stage of Tempering: (Though mild steels as a rule are not hardened and tempered in industry, it is of academic interest to see the changes occurring in such steels during tempering after hardening). The tempering reactions in steels, containing carbon less than 0.2%, differ somewhat from the [...]
In this article we will discuss about:- 1. Introduction to Tempering 2. Aim of Tempering 3. Stages 4. Classification 5. Effects 6. Time and Temperature Relationship 7. Calculation of Hardness of Tempered Steels Based on Composition 8. Industrial Practice. Contents: Introduction to Tempering Aim of Tempering Stages of Tempering Classification of Tempering Effects of Tempering Time and Temperature Relationship in [...]
The presence of alloying elements effects substantially, the tempering behaviour of the steels depending on the nature, amount and simultaneous presence of number of alloying elements. Most common elements (except cobalt) shift the CCT curve to longer times, which essentially result in the increase of hardenability of the steels, so that pearlitic transformation can be avoided easily to obtain martensitic [...]
In this article we will discuss about the features and principles of case-hardening of steels. Features of Case-Hardening of Steels: The case-hardening, where the chemical composition of steel surface is changed, has two important features: 1. The chemical composition of the steel is changed when it is in solid state. 2. The chemical composition changes only of the desired surface [...]
In this article we will discuss about:- 1. Introduction to Carburising of Steels 2. Structure and Properties 3. Mechanism of Carburising of Steels 4. Theory 5. Depth 6. Plasma Carburising 7. Carburising Furnaces. Contents: Introduction to Carburising of Steels Structure and Properties of Carburised Steels Mechanism of Carburising of Steels Theory of Carburising of Steels Depth for Carburisation of Steels [...]
In this article we will discuss about:- 1. Introduction to Nitriding 2. Operations before Nitriding 3. Process of Nitriding 4. White Layer or Compound Layer 5. Plain Carbon Steels for Nitriding 6. Effects of Microstructure 7. Advantages and Disadvantages. Contents: Introduction to Nitriding Operations before Nitriding Process for Nitriding White Layer or Compound Layer of Nitriding Plain Carbon Steels for [...]