Find the weight percent of austenite present in the steel, Mechanical Engineering

Find the weight percent of austenite present in the steel:

A 0.4% C hypoeutectoid plain carbon steel is slowly cooled from 1540oC to

(i) slightly above 723oC and (ii) slightly below 723oC.

Calculate the weight percent

1.      austenite present in the steel,

2.      ferrite present in the steel in case (i),

3.      proeutectoid ferrite prevent in the steel, and

4.      eutectoid ferrite and eutectoid cementite % present in the steel in case (ii).

Solution

Refer to Figure 8. Point 1 above the liquidus represents the state of liquid steel. The cooling occurs along the line xx and an equilibrium cooling is assumed. Freezing begins at point 2 which is intersection of liquidus and line xx. Temperature at 2 is 1510oC. The steel solidifies completely at point 3 where temperature is 1471oC. Now the entire alloy is composed of austenite (γ-phase) as indicated by first of Figure 19. No change occurs until point 4 on line A3 is reached. At this point the precipitation of ferrite begins out of solid austenite. Further cooling increases the amount of ferrite and austenite decreases. The amount of austenite varies along with IK. The composition of the ferrite varies along with the line IL.

Calculation of % content will be made by lever rule.

The amount of austenite slightly above 723oC is calculated from the line LK itself. i.e. taking LK as tie line.

 (a)       Weight % of austenite =   L5/ LK= ( 0.4 - 0.0250)/(0.8 - 0.025)

                                                       =  0.375/0.775  = 0.484 or 48.4%         ---------- (i)

                     Weight % of ferrite    = 5K / LK       =     0.8 - 0.4/0.8 - 0.025

                                                               =     0.4/0.775 = 0.516 or 51.6%        -------- (ii)

 (b)       Weight % of proeutectoid ferrite slightly below 723oC is same as that slightly above, that means 48.4%. ----------- (iii)

For calculating eutectoid ferrite, the weight of carbide will have to be subtracted form total mass of ferrite and cementite. Just below isothermal line LKM ferrite and pearlite are present and lever arm will extend up to ordinate representing 6.67% C.

Weight % of total (ferrite + cementite) just below 723oC

=     6.67 - 0.4/6.67 - 0.025

 =   6.37/6.645

  = 0.96 or 96%

Weight % of Fe3C just below 723oC

=   0.4 - 0.025/6.67 - 0.025

=  0.375/6.645

= 0.0564 or 5.64%      

Weight % of eutectoid cementite = total ferrite - proeutectoid ferrite

                                                              = 96 - 51.6 = 44.4%

Weight % of eutectoid cementite (by difference)

= 100 - 48.4 - 5.64 - 44.4 = 1.56%                                         --------- (iv)

Posted Date: 1/22/2013 1:31:10 AM | Location : United States







Related Discussions:- Find the weight percent of austenite present in the steel, Assignment Help, Ask Question on Find the weight percent of austenite present in the steel, Get Answer, Expert's Help, Find the weight percent of austenite present in the steel Discussions

Write discussion on Find the weight percent of austenite present in the steel
Your posts are moderated
Related Questions
a) Illustrate principal of magneto hydro dynamic system (MHD) with diagram? b) a thermal power plant has two 60 MW units each running for 8000hrs and one 30MW unit running for 2


i need help in my assignment it''s due few days

Norma l Temperature and Pressure (N.T.P.): The conditions of temperature and pressure at 0°C (273K) and 760 mm of Hg respectively are called normal temperature and pressure (

Determine the angle of twist - solid steel shaft: A solid steel shaft 6 m long is fixed at each of the end. A torque of 3 kN-m is applied to the shaft at a section 2 m from on

Q. Mechanical Properties of high temperature strength of metals? The high temperature strength of metals is related to their melting points, but many other factors limit the pr

A cycle stream power plant is to be designed for stream temperature and turbine 350

What are the Technical Limitations of screw conveyer Technical Limitations: ? Turning limitation of this mechanism Actually the Maximum Turning of U-joint is 18° to 2

Point of inflexion: Define the term point of contraflexure or point of inflexion. Also define point of zero shear force?  Sol.: The points (other than extreme ends of beam)

Compute the intensity of normal stress: A uniform steel bar of 2 cm × 2 cm area of cross section is subjected to axial pull of 40000 kg. Compute the intensity of normal stres