AN INVESTIGATION OF CARBURISING GRADE BORON STEEL

It was found that the addition of a minute amount of boron(0.0005-0.005%)as an alloying element can greatly increase the hardenability of steel.So it wasrecognised that boron can be used as a substitute for the more expensive alloyingelements such as nickel,chromium and molybdenum,and greatly lowering the costof steel production.The aim of this investigation was to find a substitute for steel 18 ХΓТ,in orderto save the expenditure of the alloying element chromium.By comparison of hardenability properties and core properties of the carburizedboron steel and the carburized 18 ХΓТ,a carburizing grade boron steel was finallychosen,which contained less than 0.30% chromium,0.30% nickel and 0.15%molybdenum.The boron hardenability factor decreases with increase of carbon content;itwas found in the present investigation that a linear relationship exists betweencarbon content and boron hardenability factor,expressed asF_B=1+1.88(0.97-C%).In order to obtain the best properties of the carburized boron steel,the maxi-mum carbon content of the carburized surface should be maintained below 1%.