HW6 - 4 ) to be carburized (hardened). The carburization...

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Louisiana State University Mechanical Engineering Department Professor Meletis ME 2733 Fall 2004 Materials of Engineering Homework Assignment #6 (due: Friday, 11/19/04) 1. The TTT diagram for eutectoid steel is shown in the text. Describe a thermal cooling procedure (temperature and time) to produce a final steel microstructure composed of (a) 50% bainite and 50% martensite and (b) 50% fine pearlite and 50% martensite. 2. A eutectoid steel is quenched from 800 o C to 500 o C instantaneously and is held at this temperature for 3 seconds. Then is cooled (instantaneously) to 300 o C, held at this temperature for 1 hour and cooled to room temperature. What is the produced microstructure? 3. If the same cooling treatment as above (Question 2) is applied to a 4340 steel what would be the final microstructure? 4. A thick low carbon steel plate (composition 0.1 wt% C) is heated to 1000 ° C in a carbonaceous atmosphere (CH
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Unformatted text preview: 4 ) to be carburized (hardened). The carburization conditions keep the carbon surface concentration constant at 0.8% C (assume that only one surface of the plate is exposed). A minimum hardness of R C = 60 is desired for a 2 mm depth from the surface. Describe a procedure that will produce this surface hardening (processing time, cooling procedure, etc.) and state any concerns that you might have. 5. A thick plate of plain carbon steel (composition 0.6 wt%C) is heated to 1000 o C in a dry hydrogen atmosphere to be decarburized. The hydrogen reacts with the carbon to reduce the carbon content at one surface to zero (assume that only one surface of the plate is exposed to hydrogen). After 5 hours the plate is cooled slowly to room temperature and the microstructure is examined. At what depth would one expect to find a microstructure of 35% pearlite and 65% pro-eutectoid (or primary) ferrite?...
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