Skip to main content

Influence of various constituents or elements in Steel.

The properties of steel are dependent primarily on the carbon content and to a large extent upon silicon, manganese, Sulphur and Phosphorus. Therefore, an understanding of the effect of each of the chemical elements on the properties of steel is necessary in the selection of steel for definite purposes.




Carbon Increases strength, elasticity (determined by yield point) and hardness, and lowers the ductility (characterized by elongation) and Impact strength. An Important fact is that 0.3 per cent carbon , the steel can be hardened by heating and quenching in water or oil.

Silicon in the finished steel usually ranges from 0.05 to 0.30 per cent. Silicon is put in carbon steels to prevent them from becoming porous. It acts as a very good deoxidizer and removes the gases and oxides, prevents blowholes, and thereby makes the steel tougher and harder. 

Manganese also serves as a valuable deoxidizing and purifying agent. Manganese also combines with Sulphur and thereby decreases the harmful effect of this element remaining in the steel. When uses in ordinary low carbon steels, manganese makes the metal ductile and of good bending qualities. The manganese content of carbon steel is usually less than 1.00 per cent and commonly ranges from 0.30 to 1.00 per cent.

Sulphur occurs in steel either as iron-sulphide or as manganese sulphide. Iron sulphide, because of its low melting point, produces red - shortness, i.e, increased brittleness at elevated temperatures, whilst manganese sulphide does not affect so much. Therefore, manganese sulphide is less objectionable in steel than iron sulphide. The presence of a substantial amount of Sulphur ( Sulphur Inclusion ) in steel unfavorably affects other properties of steel, e.g., tensile strength, yield point, fatigue limit , etc., and decreases its corrosion resistance.

Phosphorous imparts cold-shortness, i.e., high brittleness at normal and especially low temperatures. It increases the tensile strength but at the same type reduces the impact strength and the ductility. At a phosphorous content of slightly over 0.2 per cent the impact strength has a zero value. The embrittlement effect of phosphorus increases with an increase in the carbon content of steel. The sum of carbon and phosphorus usually does not exceed 0.25 per cent. Tool steels of the best quality do not contain more than 0.2 per cent.

The content of  Sulphur and Phosphorous is strictly limited because of their harmful effect on quality of the steel.    

Labels:

Comments

Post a Comment

Popular posts from this blog

Advantages And Disadvantages Of Air Refrigeration System :

 Advantages Of  Air Refrigeration : 1. The refrigerant used namely air is cheap and easily available. 2. There is no danger of fire or toxic effects due to leakages. 3. The weight to ton of refrigeration ratio is less as compared to other systems. Disadvantages Of Air Refrigeration : 1. The quantity of  Refrigerant used per ton of refrigeration is high as compared to other systems. 2. The COP of the system is very low. Therefore running cost is high. 3. The danger of frosting at the expander valves is more as the air contains moisture content. 
Post a Comment
Read more

SIMPLE CARBURETOR - CONSTRUCTION AND WORKING

CONSTRUCTION OF SIMPLE CARBURETOR :  The main Components of Simple Carburetor are : Float Chamber, float, nozzle, venturi, throttle valve, inlet valve, and metering jet . In the float chamber, a constant level of petrol is maintained by the float and a needle valve.  The float chamber is ventilated to atmosphere.  This is used to maintain atmospheric pressure inside the chamber. The float which is normally a metallic hollow cylinder rises and closes the inlet valve as the fuel level in the float chamber increases to certain level. The mixing chamber contains venturi, nozzle and throttle valve. The venturi tube is fitted with the inlet  manifold. This tube has a narrow opening called venturi. A nozzle is provided just below the centre of this venturi. The nozzle keeps the same level of petrol as that of the level in the float chamber. The mixing chamber has two butterfly valves.  One is to allow air into the mixing chamber known as choke valve. The other is to al...
Post a Comment
Read more

MELTING FURNACES FOR FERROUS METALS : CUPOLA AND ITS WORKING

Various types of melting furnaces are used in different foundry shops, depending upon the quantity of metal to be melted at a time, and the nature of work that is carried out in the shop.  The primary objective in cupola is to produce iron of desired composition, temperature and properties at the required rate in the most economical manner. Besides, this furnace has many distinct advantages over the other types, e.g., simplicity of operation, continuity of production, and increased output coupled with a high degree of efficiency.  Description Of a Cupola : The Cupola Furnace consists of a vertical, cylindrical steel sheet, 6 to 12 mm thick, and lined inside with acid refractory bricks or acid tamping clay. The refractory bricks or the tamping clay used consist of  silicon oxide acid (SiO2) and alumina (Al2O3). The lining is generally thicker in the lower where the temperatures encountered are higher than in the upper region. The shell is mounted either on a brick work fo...
Post a Comment
Read more