V.K. Bafna, MD TCR Engineering and Paresh Haribhakti, MD, TCR Advanced presented a paper at ASM’s Heat Treat Show 2010 on "Metallurgical Quality Control for Heat Treatment Industries."
Abstract:
Varieties of heat treatment are done on metallic engineering components to achieve desired mechanical properties and enhanced service life. Improved designs and engineering practices, rising production cost which has compelled industries to opt for high production volumes at a lower cost has propelled the heat treatment industries to reduce rejection and achieve perfection. In this present context a well-organized modern in-house quality control is a must for any heat treatment shop. Conventional practice of Hardness Test in vogue is often misleading as it does not reflect all the metallurgical parameters that the new design aspects demand more and more. Microstructure Examination, Magnetic Particle, ultrasonic and Dye Penetrant Testing, Mechanical Testing, micro hardness testing are gaining ground besides Dimensions and Hardness Measurements.
Microstructure can draw inferences with regard to metal cleanliness, prior austenite grain size, soaking time, effectiveness of hardening and tempering, solution annealing, precipitation hardening, etc. With radical changes in demands from the design with regard to surface engineering aspects, surface treatment like carburizing, nitriding, induction hardening and others require micro structural interpretation through subject quality control methods.
Normal practice is to place a sample test bar that has undergone same manufacturing process that would be later on used for carrying the prescribed tests to ensure quality after heat treatment. Nevertheless, In-Situ Metallography, Online Ultrasonic and Magnetic Particle Testing are getting more popular. Even more sophisticated tests like residual stress measurement are demanded for certain critical components after heat treatment. Good database created based on the various test results will act as useful guide to solve any problem which may crop up from time to time. Nowadays, heat treatment shop requires hardness testing machine, metallographic facilities, software's like image analyzer, micro-hardness testers and NDT facilities like UT and MP Testing equipment's.