Heat treatment is sometimes done inadvertently due to manufacturing processes

Heat treatment is sometimes done inadvertently due to

This preview shows page 16 - 19 out of 73 pages.

Heat treatment is sometimes done inadvertently due to manufacturing processes that either heat or cool the metal such as welding or forming. Heat Treatment is often associated with increasing the strength of material, but it can also be used to alter certain manufacturability objectives such as improve machining, improve formability, and restore ductility after a cold working operation. Thus it is a very enabling manufacturing process that cannot only help other manufacturing process, but can also improve product performance by increasing strength or other desirable characteristics. Major Reasons/Objectives for Heat Treatment Steels are particularly suitable for heat treatment, since they respond well to heat treatment and the commercial use of steels exceeds that of any other material. Steels can be softened, hardened and have their surface properties altered by heat treatment. Steels are heat treated for one of the following major reasons/objectives: 1. Softening Softening is done to reduce strength or hardness, remove residual stresses, improve toughness, restore ductility, refine grain size or change the electromagnetic properties of the steel. Restoring ductility or removing residual stresses is a necessary operation when a large amount of cold working is to be performed, such as in a cold-rolling operation or wiredrawing. Annealing — full Process, spheroidising, normalizing and tempering — austempering, martempering are the principal ways by which steel is softened. 2. Hardening Hardening of steels is done to increase the strength and wear properties. One of the pre-requisites for hardening is sufficient carbon and alloy content. If there is sufficient Carbon content then the steel can be directly hardened. Otherwise the surface of the part has to be Carbon enriched using some diffusion treatment hardening techniques. 3. Material Modification Heat treatment is used to modify properties of materials in addition to hardening and softening. These processes modify the behaviour of the steels in a beneficial manner to maximize service life, e.g., stress relieving, or strength properties, e.g., cryogenic treatment, or some other desirable properties, e.g., spring aging. The following are some of the inherent important objectives of heat treatment: 1. To relieve internal stresses which are set up in the metal due to cold or hot working. 2. To soften the metal. 3. To improve hardness of the metal surface. 4. To improve machinability. 5. To refine grain structure.
Image of page 16
~ Page 17 of 73 ~ 6. To improve mechanical properties like tensile strength, ductility and shock resistance, etc. 7. To improve electrical and magnetic properties. 8. To increase the resistance to wear, tear, heat, corrosion, etc.
Image of page 17
~ Page 18 of 73 ~ HEAT TREATMENT PROCESSES Plain carbon steels and alloy steels are among the relatively few engineering materials which can be usefully heat treated in order to vary their mechanical properties.
Image of page 18
Image of page 19

You've reached the end of your free preview.

Want to read all 73 pages?

  • Fall '19

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Stuck? We have tutors online 24/7 who can help you get unstuck.
A+ icon
Ask Expert Tutors You can ask You can ask You can ask (will expire )
Answers in as fast as 15 minutes
A+ icon
Ask Expert Tutors