Question

1)

a) Assume that you have two AISI 1045 cylindrical samples with two different diameters: one 1 in. thick and the other 2 in. thick. You astenitize and quench both samples in water. Then you cut a section and measure the hardness at the center of each sample. Would you expect to get the same results? Explain your answer.

b) Assume that you have two cylindrical steel samples with 1 in. diameter, one made out of AISI 1045 and another one made out of AISI 4140. You austenitize and quench both samples in oil. Then you cut a section and measure the hardness at the center of each sample. Would you expect to get the same results? Explain your answer.

Answer 1

A ) AISI1045 is Medium carbon steel so in the above case the hardness will be remain the same irrespective of speciman size ,the microhardness increases with increasing the cooling rate and carbon content due to solid solution hardnening and formation of martensite pahse .and cooling rate is propertional to time .

B ) AISI 1045 and AISI4140 both the materail 98% the chemical compositions are remain the same .only differance in the cooling media .

In AISI 1045 high carbon steel the hardness will be very less than AISI 4140