Transformation Temperature notations in Iron and Steel (Heating)

i. Acm – In hypereutectoid steel, the temperature at which the solution of Cementite in             Austenite is completed during heating.
ii. Ac1 – Temperature at which Austenite begins to form during heating (around 723°C).
iii. Ac2 – Temperature at which α-iron changes to non-magnetic β-iron (around 768°C).
iv. Ac3 -- Temperature at which transformation of α-iron to Austenite is completed.
v. Ac4 -- Temperature at which Austenite transforms to δ-ferrite during heating               (around 1492°C).

[A- arrest, c- heating]

Classification of Metallurgy

Metallurgical field can be divided into the following groups:
1.Processed or Extracted Metallurgy --- As the name suggests, it is the science of obtaining metals from their ores.
2.Physical metallurgy --- It is the science concerned with the physical and mechanical properties of metals.

    Physical Metallurgy can be classified as follows:
                i. Chemical composition.
               ii. Mechanical Treatment (Rolling, Forging, Extrusion, Wire Drawing, etc.)

              iii. Thermal or heat Treatment (It measures the effect of temperature and rate
                   of heating and cooling).
              iv. Testing of Metals.
                    a. Destructive Testing (Tensile testing, Fatigue Testing, Hardness Testing).
                    b. Non-destructive testing (Micro-hardness Test, Dye-Penetrant Test,
                         Magna-Flux Test, Radiographic Test, Ultrasonic Test).
               v. Metallography (Determination of metallographic structures with the help of
                   microscopes having high power).

A brief introduction to Metallurgy --- Now & Then

The science and technology of metals can be called as Metallurgy. It includes all physical, chemical, mechanical, allotropic and many other properties of metals and their alloys. In ancient China and Egypt, the art of smelting, refining & shaping was first developed using precious Gold for making ornaments, plates, utensils, seats and even beds. By the time Microscope was invented, it was not possible to find out the microstructure of a metal. American steel companies first started the use of microscope in early twentieth century. Although the process of X-Ray diffraction and introduction of wave mechanics was applied in 1922, the modern metallurgists had already developed.

In the past, machines, bridges and other metal works used to be very heavy and large due to the unawareness of craftsmen about the mechanical, physical, electrical properties of the particular metal. So as a matter of safety, they used to make them large enough. In modern automobile and aircraft industries metallurgists take into consideration the strength weight ratio, which has ultimately led us to a new era of Alloys.