{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Experiment_04-Heat_Treatments_of_Steels_-_Quenching_Tempering

Experiment_04-Heat_Treatments_of_Steels_-_Quenching_Tempering

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
ME 3701, Materials of Engineering Laboratory, LSU 1 Experiment: Heat Treatment of Steels- Quenching & Tempering Objectives 1) To investigate the conventional heat treatment procedures, such as quenching and annealing, used to alter the properties of steels. SAE 1040 steel standard Charpy type impact specimens will be used. 2) To study the effects of heat treatment on the microstructure and mechanical properties of steels; impact strength and hardness will be measured for heat treated specimens. 3) To quantitatively evaluate the hardenability, or depth of hardness, of a steel rod through application of the standard (ASTM A255) Jominy End-Quench Test. Abstract Conventional heat treatment procedures for producing martensitic steels generally involve continuous and rapid cooling of an austenitized specimen in some type of quenching medium, such as water, oil, or air. The properties of a steel that has been quenched and then tempered depends largely on the rate of cooling and tempering times and temperatures. During the quenching heat treatment, the specimen can be converted to a variety of microstructures including soft and ductile spheroidite to hard and brittle martensite. The production of pearlitic and bainitic steels is lower in cost and suffices for most applications. Martensitic steels must be tempered prior to use due to their extreme brittleness. A range of heat treatments producing a variety of microstructures and mechanical properties will be investigated in this experiment beginning with a set of initially equivalent samples of SAE 1040 steel. Pearlite, Bainite and Martensite will all be produced through variations in the cooling rates of initially austenized samples. The second experiment involved in the study of the heat treatment examines "Hardenability". The Jominy End-Quench Test is a widely utilized standard test procedure for determining the hardenability of ferrous alloys. The term "Hardenability" is not the same as hardness, "Hardenability" refers to an alloy's ability to be hardened by the formation of Martensite as a result of a given heat treatment. High "Hardenability" alloys are those that not only harden on the surface, but to a great extent harden throughout the part's interior. Hardenability may also be thought of as a measure of the depth to which a specific alloy may be hardened. Background Heat treatment is a combination of timed heating and cooling operations applied to a metal or alloy in the solid state in such ways as to produce certain microstructures and desired properties. Annealing, Normalizing, Quench Hardening, Tempering, and Austempering are five of the important heat treatments often used to modify the microstructure and properties of steels. The microstructure produced by any of the above heat treatments can be deduced using Continuous Cooling Transformation (CCT) diagrams, which are directly related to the Time Temperature Transformation (TTT) diagrams for the specific steel being treated. Such a TTT diagram for eutectoid steel is shown in Figure 1. The microstructures that
Background image of page 1

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

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}