| Die steel is the main material for mold manufacturing,which has been widely used in the modern industry.According to its different working conditions,die steel can be divided into cold-working die steel formed in the cold state and hot-working die steel under hot molding,as the most widely used cold die steel,Cr12MoV steel has good hardenability,small heat treatment deformation,and its hardness reaches to HRC58 after tempering.Dueing to these fine properties,Cr12MoV steel is suitable for the mass production of complex shape cold-working die steel which can bear heavy-load.Because serious network eutectic carbides in the as-cast Cr12MoV steel dissever the substrates,the manufacturing process of cold-working die steel is very complex.We need improving-forging and heat-treating the raw materials to ameliorate the material properties,then maching into the required specific shape. These work will consume a large amount of energy and time,at the same time causing a waste of precious metal raw materials.Consequently,with the intensive study,we wish to develop a new process that is "casting on behalf of forging",which can cancel forging,cast into die or billet directly,reduce the loss of metal,shorten the production cycle,save energy and manufacturing costs.This paper mainly studied the impact of the modification treatment with the rare-earth ferrosilicon on Cr12MoV steel.Adopting EPC to cast Cr12MoV Steel ingots,we added different content of rare-earth ferrosilicon alloys,then observed their metallurgical structure,the change of the hardness and toughness.The results show that,as the modifier,rare-earth ferrosilicon can significantly improve the performance of Cr12MoV steel.Network eutectic carbides in the as-cast Cr12MoV steel fracture by and large,making carbides distribute more uniformly.During the heat treatment, the improvement of the morphology and distribution of the carbides,as well as the obvious fracture of the network,resulting in the increase of the blocky and granular carbides,and their uniform distribution.When the rare-earth additive amount was less than 0.4%,with the increase of the rare-earth additive amount,the microstructure, hardness and homogenization of the materials were obvious improved.On the other hand,when the rare-earth additive amount was higher than 0.4%,the properties of the materials didn't change significantly with the increase of the rare-earth.The modification treatment with the rare-earth ferrosilicon on Cr12MoV steel totally ruptured the net of the eutectic carbides.The hardness and the toughness of Cr12MoV steel were up to HRC60 and 12J/cm~2,respectively,so it could alternate part of forgings basically.The addition of rare-earth ferrosilicon had no influence on the linear shrinkage of Cr12MoV steel.Investigating the casting process of Cr12MoV steel and using InteCast Software to simulate the casting,mold filling and solidification processes of the steel,we found that the shrinkage of the castings was hard to completely eliminate,owing to the limit of casting shape and the material properties.Compared the shapes of the riser-ring and ring modules in different place with different size,we concluded that the optimum design scheme was to set the riser-ring and ring module with the size of 110×85×80mm in the root of the fixed plane,which could keep the size and the quantity of the shrinkage to a minimum.Pouring temperature had little impact on the mold filling.Instead of impacting the casting,the raising of the pouring temperature only increased the number of the shrinkage.Therefore,we only need to select the lowest pouring temperature(1500℃).
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