IRON
Pure iron is a metal. It oxides readily in the oxygen and moisture. In order to Bail metallic iron, oxygen must be removed from the naturally occurring ores bY chemical reduction. The property of iron can be modified by alloying it with various other metals ( and some no metals notably carbon and silicon) to form steels. The most common grade is IS 2062
IS 2062 Standard (Rev—2006)
This standard was formerly known as IS 226. Now IS 2062 has replaced this specification. This grade is for "Steel for general structural purposes".
IS (Indian Standard) - product standard of Bureau of Indian Standards. It specifies standards for Hot-Rolled Medium and High Tensile Structural Steel & they are then issued by Bureau of Indian standards to companies.
IS:2062- is a hot rolled structural steel that comes mainly in three qualities, which are A, B and C which are equalant to E250(E-Engineering standard/ grade that has a minimum yield strength of 250 MPa).A,B (BR & BO), C that give the % of carbon i.e. 0.42 max, 0.41 max and 0.39 max respectively. The carbon percentage goes down from A to C grade i.e. if carbon percentage reduces the strength increases and weldability increases. From these grades, our commonly used grade will be IS 2062
Grade B.
Chemical property of IS 2062
The various contents which are added with iron are given below
1. Carbon - is generally considered to be the most important alloying element in steel and can be present up to 2% (although most welded steels have less than 0.5%). Increased amounts of carbon increase hardness and tensile strength, as well as response to heat treatment (hardenability). Increased amounts of carbon will reduce weldability.
2. Sulfur - is usually an undesirable impurity in steel rather than an alloying element. In amounts exceeding 0.05% it tends to cause brittleness and reduce weldability. Alloying additions of sulfur in amounts from 0.10% to 0.30% will tend to improve the machinability of a steel. Such types may be referred to as "resulfurized" or "freemachining". Free-machining alloys are not intended for use where welding is required.
3. Phosphorus - is generally considered to be an undesirable impurity in steels. It is normally found in amounts up to 0.04% in most carbon steels. In hardened steels, it may tend to cause embrittlement. In low-alloy high-strength steels, phosphorus may be added in amounts up to 0.10% to improve strength and corrosion resistance.
4. Silicon - Usually only small amounts (0.20%) are present in rolled steel when it is used as a deoxidizer. However, in steel castings, 0.35 to 1.00% is commonly present. Silicon dissolves in iron and tends to strengthen it. Weld metal usually contains approximately 0.50% silicon as a deoxidizer. Some filler metals may contain up to 1% to provide enhanced cleaning and deoxidation for welding on contaminated surfaces. When these filler metals are used for welding on clean surfaces, the resulting weld metal strength will be markedly increased. The resulting decrease in ductility could resent cracking problems.
5. Manganese - Steels usually contain at least 0.30% manganese because it assists in the deoxidation of the steel, prevents the formation of iron sulfide and inclusions, and promotes greater strength by increasing the hardenability of the steel. Amounts of up to 1.5% can be found in some carbon steels.
6. Chromium - is a powerful alloying element in steel. It strongly increases the hardenability of steel, and markedly improves the corrosion resistance of alloys in oxidizing media. Its presence in some steels could cause excessive hardness and cracking in and adjacent to welds. Stainless steels may contain in excess of 12% chromium.
7. Molybdenum - This element is a strong carbide former and is usually present in alloy steels in amounts less than 1%. It increases hardenability and elevated temperature strength. In austenitic stainless steels it improves pitting corrosion resistance.
8. Nickel - is added to steels to increase hardenability. It often improves the toughness and ductility of the steel, even with the increased strength and hardness it brings. It is frequently used to improve toughness at low temperature.
9. Aluminium - is added to steel in very small amounts as a deoxidizer. It also is a grain refiner for improved toughness; steels with moderate aluminium additions have been made to a "fine grain practice".
10. Vanadium - The addition of vanadium will result in an increase in the hardenability of a steel. It is very effective, so it is added in minute amounts. At greater than 0.05%, there may be a tendency for the steel to become embrittled during thermal stress relief treatments.
Mechanical property of IS 2062
The various test which are using with iron manufacturing is given below
1. Tensile Strength - The maximum amount of stress a material can withstand while being stretched or pulled without breaking is referred to as tensile strength. Mild steel is a relatively ductile material as it contains a smaller amount of the hardening alloy — carbon — than other carbon steels. It has a low tensile strength of around 400MPa. Tensile strength is measured as a force per unit area - the unit being a Pascal (Pa)/mega pascal(MPa), a newton per square meter (N/m2) or pounds-force per square inch (psi).
2. Yield Strength - is defined as being the amount of stress applied to a material that will deform it permanently. It is also referred to as a ‘yield point’ because the material will return to its original shape if the amount of stress does not pass the yield point, but if it does exceed the yield point then the material will not return to its original shape and the deformation will be permanent. Like tensile strength, yield strength is measured in Pascals (Pa) or mega pascals (MPa). Mild steel as an approximate yield strength of 250MPa.
3. Percentage Elongation - is the increase in gauge length compared to the original length. Percentage elongation = (increase in length X 100) / original length
4. Internal Bend Diameter - Bend radius, which is measured to the inside curvature, is the minimum radius one can bend a pipe, tube, sheet, cable or hose without kinking it, damaging it, or shortening its life. The smaller the bend radius, the greater is the material flexibility (as the radius of curvature decreases, the curvature increases).
5. Charpy Impact Test - also known as the Charpy V-notch test, is a standardized high strain-rate test which determines the amount of energy absorbed by a material during fracture. This absorbed energy is a measure of a given material's notch toughness and acts as a tool to study temperature-dependent ductile-brittle transition.