E45 - Lab 4 - Heat Treatment of Steel

E45 - Lab 4 - Heat Treatment of Steel - Engineering 45...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
E E n n g g i i n n e e e e r r i i n n g g 4 4 5 5 P P r r o o p p e e r r t t i i e e s s o o f f M M a a t t e e r r i i a a l l s s L L a a b b o o r r a a t t o o r r y y © Copyright 2001 Professor Ronald Gronsky the Arthur C. and Phyllis G. Oppenheimer Chair in Advanced Materials Analysis University of California Berkeley, California 94720-1760
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
E 45 2 Lab 4 Heat Treatment of Steel Objective To understand how the processing (heat treatment) of steel affects both microstructure and properties (hardness) Overview This lab is designed to illustrate the versatility of steel as a structural material. One sample of a single grade of steel will be subjected to heat treatments similar to those employed in industry. Students will monitor the changes resulting from these simple inexpensive treatments, noting the dramatic changes in both microstructure and hardness that result. References G. Krauss, Principles of Heat Treatment of Steel , American Society for Metals, Metals Park, OH, (1980). W.T. Lankford, et.al. , Eds., The Making, Shaping, and Treating of Steel , 10 th edition, Association of Iron and Steel Engineers, Pittsburgh, PA, (1985). Metals Handbook , 9 th edition, Vol. 4 , Heat Treating , American Society for Metals, Metals Park, OH, (1981). Background Steel is an alloy of iron (Fe) and carbon (C), with concentrations of carbon from 0.1 to 2.0 weight percent. Carbon is soluble in Fe because the C atoms are small enough to fit into interstitial locations between Fe atoms without too much distortion of the lattice. Carbon is soluble in the fcc phase of Fe (called austenite or gamma-Fe, or ) up to approximately 2%. However, in the bcc phase of Fe (called ferrite or alpha-Fe or ), the maximum solubility is only about 0.02%. When austenite is cooled below a critical temperature called the eutectoid temperature (727°C), it becomes unstable. Most of the Fe tends to precipitate as nearly pure ferrite and most of the C tends to come out as the intermetallic compound Fe 3 C ( cementite ). The transformation of austenite requires redistribution of C atoms from a random solid solution to one in which nearly all of the C is contained in the Fe 3 C precipitates. At temperatures just below the eutectoid decomposition temperature the driving force for the transformation is low, and nucleation of the two new phases, ferrite and cementite, is slow. It is therefore necessary to hold the specimen at temperature for a considerable time to allow the transformation to take place in those regions of the specimen that are just
Background image of page 2
E 45 3 below 727°C. The lower the temperature, the greater the driving force for the reaction to occur, causing a higher nucleation rate. At temperatures below about 540°C, however, the rate of transformation again becomes slower. This is due to the decreasing mobility of C
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/26/2010 for the course ENGLISH 45 taught by Professor Morris during the Spring '10 term at University of California, Berkeley.

Page1 / 8

E45 - Lab 4 - Heat Treatment of Steel - Engineering 45...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online