Effect Of Conduction Mode On Solidification Quality And Performance Of Electroslag Remelting S136 Die Steel Used For Plastic Mold

With the continuous attention paid to the plastics industry in China in recent decades,a large number of mold processing and manufacturing factories with professional qualifications have appeared,and plastic products have been widely used.Higher and higher quality for plastic mold steel are required.Due to uneven microstructure of large ingots,segregation of alloying elements,massive precipitation of carbides and segregation,the S136 corrosion-resistant plastic mold steel produced by the traditional process affects the later performance seriously,and has not been able to meet the need for the large-scale,high-end and market development of current mold industry.Therefore,to develop technology and new products of high-quality plastic mold steel is the top priority for the plastic mold industry.In this paper,a new conductive mold electroslag remelting technology was used to smelt traditional S136 steel under the laboratory conditions of Northeastern University,comparing the influence of different conduction modes on solidification quality and comprehensive performance of S136 die steel for plastic mold.Main conclusions are as follows:(1)The oxygen content of the S136 ingots produced by the double-circuit electroslag remelting technology is lower,20.33×10-6 in the ingot core and 14.66×10-6 in the edge.The oxygen content in the core and the edge is 25.37×10-6 and 17.03×10-6 for traditional circuit ingot respectively.(2)By analysing the secondary dendrite spacing of ingots,it can be known that the secondary dendrite spacing of the double-circuit ingot is smaller than that in the conventional circuit ingot.At the same time the concentration difference of C and Cr elements on the secondary dendritic arms and among the secondary dendritics is smaller,and the segregation is smaller.Furthermore,the segregation ratios of C and Cr elements are 1.2364 and 0.8362 for double circuit samples,while those in traditional circuit samples are 1.5736 and 0.3568.(3)By analysing ingot inclusions,it can be known that the new process is more conducive to removing inclusions in the ingot,especially for the inclusions in the core and edge,but the new process has little effect on the composition and morphology of the inclusions.(4)By analysing the microstructure and carbides of the ingot,it can be concluded that the conduction mode has no effect on the microstructure type,but has a great influence on the content,size and distribution state of the precipitated phase.and the precipitated phase is M23C6 carbide.Double-circuit electroslag remelting technology is more conducive to obtaining smaller and more dispersed carbides.(5)By analysing the mechanical properties and polishing properties of ingots,it can be concluded that combined with the analysis of the resistance strength,the ductile toughness of the double circuit process sample is better,so the double circuit sample has better mechanical properties.At the same time,the double-circuit process sample has better polishing performance,The surface roughness is 0.034?m for double circuit sample,and that of traditional loop sample is 0.045 ?m.(6)By analysing corrosion resistance of ingot,it is known that the pitting potential in tempering state of double-loop specimens is 165mV and the traditional circuit specimens is 153mV.Double-loop specimens are more resistant to pitting corrosion,while it's discovered that the chromium-depleted region exists around the precipitated phase,and the pitting source preferentially occurs in the chromium-depleted region.