Abstract
The effect of tempering on mechanical properties of cold rolled 42CrMo4 steel pipes was studied. The production of pipes consisted of hot rolling + annealing at 700 °C + cold rolling + quenching with subsequent tempering. By annealing of seamless pipes at 700 °C under industrial conditions and using protective atmosphere and cold rolling, the tempered bainite microstructure was observed. Quenching and tempering of pipes in laboratory conditions resulted in a high yield strength (986-1230 MPa), combined with a high impact toughness value at 20 °C (46.1-66.9 J.cm^-2). The strength of pipes shows a continuous decrease with the increase in tempering parameter. Decrease in strength is due to the spheroidization of carbides and the recovery of the microstructure. The most important observation is that it is possible to use this technique for the production of pipes in order to optimize the strength and toughness of 42CrMo4 steel pipes.

Key words
steel, cold rolling, pipes, tempering, mechanical properties, microstructure

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