Cooling Rate and Quenching Media Assignment Help

Heat Treatment Of Steel - Cooling Rate and Quenching Media

Cooling Rate and Quenching Media

Rate of cooling plays a significant role in calculating the last structure subsequent to quenching in case of eutectoid steel. Following figure schematically demonstrates four different structures that are acquired cooling rates while austenitized steel is cooled in four various media.

                                           1765_Cooling Rate and Quenching Media.png

        Figure: Microstructure resulting from Different Cooling Rates Applied to Austenitized Samples of Eutectoid Steel

Just the drastic water quench generates a fully martensite structure. Although quenched in oil the austensite converts into suitably fine pearlite. Accurate pearlite also results if the austenised eutectoid steel is air-cooled. Though, if allowed to cool in furnace coarse pearlite is appearance. These effects have previously been considered beneath the headings of annealing and normalizing. Though, it might be mentioned that properly fine pearlite structure such is acquired from oil quenching is identify primary troostite. Table no.9 illustrates the effects of several cooling media on mechanical properties of eutectoid steels.

                             Table no.9: Mechanical Properties of Eutectoid Steels after Cooling in various Quenching Media

Cooling

Media

Structure

UTS (N/mm2)

Y. S. (N/mm2)

Hardness

(Rc)

Elongation % (50 mm g. L)

Water

Martensite

1700

-

65

Low

Oil

Troostite

1100

550

35

5

Air

Fine pearlite

850

270

25

8

Furnace

Coarse pearlite

520

140

15

12

Water is the expensive quench media for plain carbon steels. Though, while utilizing water care must be exercised that water is appropriately agitated during such treatment or else air bubbles might be trapped on the surface and insulate the spots from that heat flow will be delayed. That type of spots will enhance softness. Brine or Salt water is extra severe quenching media as this removes heat faster. Though, in this condition the steel should be thoroughly cleaned after quenching or else the surface begins to rust. For extremely low carbon steels hydroxide solutions are often utilized instead of brine. If slower cooling rates are preferred, the steel might be quenched in oil along with high flash points. Various type of grades of quenching oil are obtainable. High C steels are invariably quenched in oil as water quenching will improve cracks in such steels.


Expertsmind’s world class education services

We at www.expertsmind.com offer email based assignment help – homework help and projects assistance from k-12 academic level to college and university level and management and engineering studies. Our experts are helping students in their studies and they offer instant tutoring assistance giving their best practiced knowledge and spreading their world class education services through e-Learning program.

- Quality assignment help assistance 24x7 hrs
- Best qualified tutor’s network
- Time on delivery
- Quality assurance before delivery
- 100% originality and fresh work