Object
To investigate the changes in properties of medium-carbon steels when subjected to a range of different heat treatments. In addition to this to determine the ‘as-received’ condition of the material.
Part 1 Method
perform simple tensile tests on Hounsfield Tensometers. Specimens should be measured prior to testing and data recorded in the table below. accurately plot load against extension graphs during the tests.
Results
Composition
Code Diameter
mm Description Max Load
kN Yield Load
kN %
C %
Si %
Mn %
S %
P %
Cr %
K Oil Quenched @ 840°C; Tempered @ 550°C
0.54
0.16
0.72
0.033
0.039
L Oil Quenched @ 840°C; Tempered @ 600°C
0.54
0.16
0.72
0.033
0.039
EN 9 As received
Part 2 Method
Bar stock will be prepared for tensile, hardness and impact testing. Some heat treatment procedures will be demonstrated and the pieces will then be tested. Graphs from the tensile tests will be provided. Results should be recorded in the table below:
Results
Condition Specimen #1 Specimen #2
Max Load kN Yield Load kN Charpy
Impact
J Max Load kN Yield Load kN Charpy
Impact
J Hardness
(Scale)
As Received
68.2 5 5 Hv10
235
Annealed @ 900ºC for 2 Hours 39.2
15.5
16
HB170
Water Quench @ 860ºC
3
3.5 Hv10
827
Oil Quench @ 860ºC 18.5 4 Hv10
564
Normalised @ 860ºC 51.7 29 27 Hv10
175
Water Quench @ 860ºC & Tempered @ 550ºC
18
25
Hv10
318
Water Quench @ 860ºC & Tempered @ 680ºC
49.5
55
Hv10
260
Water Quench @ 860ºC & Oil Tempered @ 550ºC
18
18.5
Hv10
310
Water Quench @ 860ºC & Oil Tempered @ 680ºC
6.5
47.5
Hv10
254
Health & Safety
Extreme care should be taken when using heat-treatment facilities. Eye and skin protection must be used. Extractors should be switched on prior to heat-treatment procedures and the area sealed from smoke detectors. Specimens should be treated with caution, ever after heat-treatment they can still cause burns and injuries if touched. Furnaces should be switched off as soon as the procedure is complete.
Discussion & Further Reading
1.Calculate the ultimate tensile strengths and yield strengths (where applicable) of the specimens and bar stock tested.
2.Discuss the nature of the graphs in terms of the heat-treatment performed. Comment on properties such as strength, ductility, toughness. Summarise how the optimum properties can be achieved and deduce what form the ‘as-received’ condition of the material was.
3.Explain the mechanisms behind heat-treatment and why heat-treatment procedures can be used to change the properties of a medium-carbon steel.
Conclusion
Review applications of the steel used in the investigation, justifying the form of it in the ‘as-received’ condition.
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