Mechanical Properties and Microstructures of Warm-Extruded 0.43% Carbon Steels

Abstract

Carbon steels for mechanical structural use, S 43 C(0.40∼0.46%C), have been extruded in the temperature range from 300° to 900°C and at the reduction in area from 20 to 80% to investigate the effects of working temperature and reduction in area on the mechanical properties of the products and microstructures of the products.
The results obtained were as follows:
(1) In case of the as-rolled materials with the reduction of 65% in area, the toughness of the extruded products remarkably increased for the temperature rise from 500° to 700°C. But this phenomenon was not observed for the spheroidized materials. For fully annealed materials, the increase toughness was not so high as in the case of the as-rolled materials.
(2) As the reduction in area became higher, the toughness of the products increased and the range of the working temperature where a high toughness could be obtained became wider.
(3) The impact value depended largely on the reduction in area, but not so much on other mechanical properties.
(4) When the materials were extruded at the reduction of 80% in area and at 300∼600°C, the strength-toughness of the products were almost equal to that of quenched-tempered materials.
(5) When the structures of materials composed of ferrite and pearlite become fibrous like fiber-reinforced composite materials by means of extrusion, the toughness of the products seems to become higher. On the contrary, when the structures composed of ferrite and spheroidized cementite do not become fibrous by means of extrusion, the toughness of the products do not seem to become higher.