What is heat Treatment ?

HEAT TREATMENT

• It is a continuous process of HEATING, HOLDING AT A PARTICULAR TEMPERATURE FOR SPECIFIC TIME AND COOLING AT A PREDETERMINED RATE of metals to change their physical and mechanical properties, without letting it change its shape. . The most common application is metallurgical. Heat treatment could be said to be a method for strengthening materials but could also be used to alter some mechanical properties such as improving formability, machining, etc. It is very important manufacturing processes that can not only help manufacturing process but can also improve product, its performance, and its characteristics in many ways.

• Engineering properties are modified by heat treatment processes so that structural components are able withstand specified operating conditions and have desired useful life.

The properties of steel can be improved by changing its structure at atomic level. This can be achieved through

i) By Alloying Elements
ii) By Heat Treatment

a same type of steel can exhibit different type of properties under different heat treatment conditions. Such type of flexibility helps us to decide various manufacturing processes and ultimate uses of steel.

DETAILS OF HEAT TREATMENT

1. Heating -> Rate of Heating

2. Soaking -> Temp. & time of Soaking

3. Cooling -> Rate & Medium of cooling

- The properties of steel can be influenced by different combinations of the above parameters

- Different composition and initial phases of material can also be influenced the properties after Heat Treatment.

PURPOSE OF HEAT TREATMENT

(1) Soften the metal prior to shaping or cutting / Machining.

(2) Relieve the effects of strain hardening that occurs during cold forming.

(3) Achieve the final strength and hardness required in the finished product as one of the end manufacturing processes.

TYPE OF HEAT TREATMENT

· Body heat treatment

· Surface heat treatment

TYPE OF THERMAL TREATMENT

Annealing.
Normalizing
Hardening & Tempering.
Stress Relieving
Surface Hardening.

Part -2 Most commonly asked Mechanical Interview Questions

Most commonly asked Mechanical Interview Questions 1. What is the difference between Critical Speed and Whirling Speed? Ans. In Solid mechanics, in the field of rotor dynamics, the critical speed is the theoretical angular velocity which excites the natural frequency of a rotating object, such as a shaft, propeller or gear. As the speed of rotation approaches the objects natural frequency, the object begins to resonate which dramatically increases system vibration. The resulting resonance occurs regardless of orientation.Whirling Speed is due to the unbalanced forces acting on a rotating shaft. 2. How a Diesel Engine Works as Generator? Ans. Diesel engine is a prime mover, for a generator, pump,and for vehicles etc. generator is connected to engine by shaft. mostly in thermal power plat ,there is an engine is used to drive generator to generate power. 3. Explain Second Law of Thermodynamics? Ans. The entropy of the universe increases over tim...

VISUAL INSPECTION OF WELDING

VISUAL INSPECTION OF WELDING INTRODUCTION Inspection starts with examination of the material prior to fabrication, scabs, seams, scale or other harmful surface conditions may be detected in visual inspection. The inspector should check the following : Weld preparation, dimensions and finish. Clearance dimensions of backing strips. Alignment and fit up to the pieces being welded. Verification of cleanliness. Visual Inspection During Welding Visual inspection checks details of the work while welding is in progress. Among the details to be checked are : Welding process. Cleaning. Preheat and inter pass temperature. Joint preparation. Filler metal. Flux or shielding gas. Chipping, grinding, or gouging. Post heating temperature and time. Visual Inspection After Welding Visual inspection is useful for finished-product verification of such items as : Profile irregularities of the weldment....

BEND TESTS

BEND TESTS Object: To determine the soundness of weld metal, heat affected zone and weld zone.These tests may also be used to give some measure of the ductility of the weld zone. It is not usual to use transverse and longitudinal bend tests for the same application. Method: All specimens to be removed and prepared without causing significant distortion or heating. The cap and root are ground flush. The specimen is bent by the movement of a former of prescribed diameter, the relevant side of the specimen to be placed in tension. Angle of bend and diameter of former should be as specified in the appropriate standard. Reporting Results: Thickness of specimen Direction of bend (root or face) Angle of bend Diameter of former Appearance of joint after bending e.g. type and location of flaws

Mechanical Engineering

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