15-01-2013, 10:02 AM
TO STUDY THE EFFECT OF QUENCHED AND INTERCRITICAL HEAT TREATMENT ON MECHANICAL PROPERTIES OF PLAIN LOW CARBON STEEL
TO STUDY THE EFFECT.pptx (Size: 613.28 KB / Downloads: 41)
INTRODUCTION
Low carbon steel contains up to 0.30% C.
It is used where ductility and softness are important .
Dual phase can be easily developed with low carbon steel by intercritical heating.
The desire to produce high strength steels with formability greater than micro alloyed steel led the development of DPS in 1970s.
Dual phase steels are preferred in the automotive industry due to their low density and high load bearing capacity.
PROBLEM FORMULATION
In recent years, the search and application of new advanced materials have been much in demand by the automotive industries.
Approximately 85% of Advanced High Strength Steel (AHSS) should be used for different construction parts of a vehicle that could lead to a weight reduction up to 25% compared with a common model.[3]
The distinctly attractive feature of the AHS steels is the excellent combination of high strength property and good formability.
Dual phase(DP) steel is one of the most important types of the AHS steel.[3]
It has been observed that very few study are found on Strain rate dependence of tensile ductility of DP steel.
Intercritical Heat Treatment
When low-carbon steel are annealed between the AC1 and AC3 and then water quenched, due to partial transformation taking place, a dual phase structure, i.e., an mixture embedded martensite islands within the grains of ferrite is usually obtained.
(a). Intercritical Heating at 750 ºC
(b). Intercritical Heating at 850 ºC
Annealing
In this heat treatment the material will be heated above upper critical line and allowed to cool in the furnace.
The temperature range for annealing is shown in the figure.
Oil Quenching
Oil quenching is the rapid cooling of a work piece to obtain certain material properties.
Upon being rapidly cooled, a portion of austenite will transform to martensite, a hard, brittle crystalline structure.
Microstructure Study
Microstructure will be studied by the help of Scanning electron microscope.
It images a sample by scanning it with a beam of electrons in a raster scan pattern.
The electrons interact with the atoms that make up the sample producing signals that contain information about the sample's surface topography, composition, and other properties such as electrical conductivity.
HEAT TREATMENT PROCESSES
We have completed Annealing process on two tensile specimen.
Heating is done in the muffle furnace.
The temperature range for this process is 940˚C- 960˚C
The soaking time given is ½ hour.