Carburizing and Heat Treatment of Carburizing Grade Steel Parts

The article discusses the results of investigations performed during a thermo-mechanical treatment of forgings made of chromium-molybdenum 42CrMo4 grade steel. The treatment was realized during a regular series production. The forging process was combined with a heat treatment carried out directly after forging on a specially adapted station. Such a production technology will make it possible to eliminate the step of repeated heating of the forgings. On the example of an element of a steering gear, it was demonstrated how it is possible to perform an isothermal annealing process starting from the temperature at which the trimming of the forgings ends. During the cooling of the forgings, it is enough to maintain the temperature at the proper level in order for the exothermal phase transformation of austenite into pearlite to take place. With an appropriate design of the processing line, the heat released during the transformation could be used to maintain the applied temperature, thus limiting the consumption of energy needed to power the devices. The test results show that, with the properly selected temperature of isothermal annealing, it is possible to obtain an equilibrial ferritic-pearlitic structure in the required hardness scope. Introducing such a solution into the industrial practice would allow significant savings of the energy used for the heat treatment.

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Development of Hardening and Tempering Cycle for High Strength Low Alloy Fastener Grade Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.710.506 ◽

2012 ◽

Vol 710 ◽

pp. 506-510

Author(s):

M. K. Kathikeyan ◽

R.K. Gupta ◽

V. Anil Kumar ◽

P. Ramkumar

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Microstructural Analysis ◽

High Strength ◽

Strength Level ◽

Martensitic Structure ◽

Medium Carbon ◽

Aerospace Fasteners ◽

Heat Treated ◽

Grade Steel

Medium carbon low alloy Ni-Cr-Mo steel is used in the fabrication of aerospace fasteners. It finds application in different heat treated conditions to meet the desired strength level. The alloy was realized through double melting route. Heat Treatment studies have been carried out by following different tempering temperatures to obtain varying strength levels ranging from 1200MPa to 1400MPa. Microstructural analysis has been carried out to find out reasons for variation in mechanical properties. Tempering cycle has been suggested to obtain fully tempered martensitic structure. This paper presents the different hardening and tempering cycles studied to obtain the desired strength level for the intended application.

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