The Effect of Alloying Elements on the Continuous Cooling Transformation Diagrams and Hardenability of Medium Carbon Si-Mn-Mo-V Steels

The continuous cooling transformation diagrams and hardenability of 40. 40Si2,40Mn2 and 40Si2Mn2 steels have been determined by the end-quenching method.At the same time,the influence of Si or Mn on the hardenability of Si-Mn-Mo-V steels has been investigated and the multiple hardenability factors for half-martensite content in the center of the ideal critical diameters were also calculated.These results semi-quantitatively shows the relationship between hardenability and the Si and Mn contents in the steels.
These experiment results also show that Si raises the temperatures of pro-eutectoid ferrite transformation and pearlite transformation to higher temperatures and also moves the transformation diagram slightly to the right. When Mn or Mo, especially Mn, was added to the carbon steel, the temperature of bainitic transformation is lowered and time of transformation markedly increased.The influence of Si and Mn on the transformation114 diagrams and hardenability is much more pro Bounced when they are added together than added singly.In this case,the transformation diagram will be moved towards the lower-right direction.The effectiveness of alloying elements on increasing hardenability decreases according to the order of Mn Mo and Si.However the hardenability of 40Mn steel can be hardenability of greatly increased by Si addition.The combined effect of Si and Mn on the steel is not on additive basis,but on multiple One.So that in order to keep 40SiMnMoV steel having sufficient hardenability,more than 1.5%Mn,1.3% Si and proper amount of Mo must be added.