EFFECTS OF BORON ALLOYING ON THE PROPERTIES OF A LOW-CARBON LOW-ALLOYED STEEL .1. THE MECHANICAL-PROPERTIES

The effects of boron alloying on the mechanical properties of a low-carbon low-alloyed steel were studied. The high purity laboratory steels alloyed with titanium and different amounts of boron were austenitised, quenched in brine, and tempered at 200°C or 500°C. The tensile and impact properties were investigated. The initiation and propagation of fracture was studied with a scanning electron microscope. In the steels studied the cleavage fracture is initiated by cracking of Ti(C,N) precipitates which thus control the impact toughness. Boron alloying did influence tensile or impact properties. Four alloys with a basic chemical composition corresponding to the German steel standard 20 MnCr 5 (DIN 17210) were used in the study.