Heat Treatment Flashcards
What is the objective of this lab?
The primary objective of this lab is to:
Experience Heat Treatment Methods: Understand and apply different heat treatment techniques (e.g., quenching in water or oil, air cooling, carburizing, and carbo-nitriding) to steel coupons.
Analyze Hardness Variations: Measure and analyze the changes in material hardness and microstructure resulting from these treatments.
Explore Cooling Effects: Study the effects of cooling rate on microstructural transformations (e.g., formation of martensite, ferrite, and cementite) and the corresponding impact on material properties.
Develop TTT Diagrams: Relate observations to theoretical Time-Temperature-Transformation (TTT) diagrams for various treatments.
Through these experiments, students will learn how processing methods influence mechanical properties, enabling a deeper understanding of material behavior under thermal and mechanical treatments.
What is the procedures for this lab? Part 1
- Preparation of Coupons:
Remove burrs from the flat faces of the coupons using a file or sander.
Punch letter marks on both ends of the coupons for identification.
Sequence placement of coupons A, B, C, D, E, F, G, H, I, J, K, L, M in the oven for uniform heat treatment.
Control coupons: Place 4140 coupon (N) and 1018 coupon (O) as controls. - Heat Treatment Process:
Heating: Place coupons in a preset 1700°F oven for about 10 minutes.
Quenching:
Quench 1018 and 4140 carburized coupons (A, B, C, D) in water.
Quench 1018 (E, F) and 4140 coupons (G, H) in water.
Quench 4140 coupons (I, J) in oil (swirl vigorously).
Cool one 4140 coupon (K) in air on a cement block.
Carburizing: Drop 1018 coupon (L) and 4140 coupon (M) in Kasenit powder and quench after 60 seconds.
What is the procedures for this lab? Part 2
- Hardness Testing:
Rockwell Hardness Testing:
Use C Scale for all samples; if hardness is below 20RC, switch to Rockwell A scale.
Take 5 readings: one at the top, one at the bottom, and three on the side (120° apart). Average and discard outliers.
Record HBN from the chart for each reading. - Cutting and Polishing Coupons:
Cutting: Use a cut-off saw to cut carburized coupons (A, B), carbo-nitrided coupon (L), annealed 1018 coupon (P), and control 1018 coupon (O).
Polishing: Polish coupons with a belt sander using progressively finer grits (240, 320, 600).
After sanding, use a rotating polishing unit with fine slurry for a smooth finish. - Etching Coupons:
Etching: Clean coupons and apply Nital solution (a mix of nitric acid and methanol) to reveal the grain structure.
Use the optical microscope to observe and compare grain sizes.
Record images of the coupons at different magnifications. - Micro-Hardness Testing (for Carburized and Nitrided Coupons):
Use a micro-hardness tester to measure hardness along a line from the center to the surface.
Focus the coupon, set the Rockwell C scale, and perform the tests.
Take 10 readings from surface to center in 0.025” increments.
What is the conclusion’s for this lab?
This lab demonstrated how different heat treatment methods affect the hardness and microstructure of 1018 and 4140 steel alloys. Water quenching resulted in higher hardness due to the formation of martensite, while oil and air quenching produced lower hardness because of slower cooling rates. These findings help in selecting the appropriate heat treatment methods based on desired material properties.
