The effects of the mold preheating and the silicon content of ductile iron on the percentage of carbides,graphite nodule counts and shrinkage volume were investigated.The results showed that the percentage of carbides...The effects of the mold preheating and the silicon content of ductile iron on the percentage of carbides,graphite nodule counts and shrinkage volume were investigated.The results showed that the percentage of carbides and the shrinkage volume decreased when the mold preheating increased.The ductile iron with the carbon equivalent of 4.45 % and the silicon content of 2.5% without any porosity defects was achieved when the mold preheating was 450 ℃.Increasing the silicon content in the range of 2.1%-3.3% led to the increase in graphite nodule count and graphite size and the decrease in percentage of carbides.It is due to the increase in induced expansion pressure during the graphite formation with the increasing of silicon content.The suitable condition for casting a sound product of ductile iron without the riser at the mold preheating temperature of 300 ℃ is the silicon content of 3.3% and carbon equivalent of 4.7%.展开更多
The void evolution of large-section plastic mold steel during multi-directional forging(MDF)was investigated using multiscale analysis.To simulate the forging process of the plastic mold steel(SDP1 steel)and realize m...The void evolution of large-section plastic mold steel during multi-directional forging(MDF)was investigated using multiscale analysis.To simulate the forging process of the plastic mold steel(SDP1 steel)and realize micro-void reconstruction in a representative volume element(RVE),MDF experiment and void-characteristic evaluation of the SDP1 steel were carried out.Traditional upsetting and stretching forging(TUSF)and MDF were simulated to comparatively analyze the evolution of temperature,effective stress,and effective strain.By embedding RVE with a micro-void and using boundary condition by point tracking into the forging process,the single-void evolution in TUSF and MDF was studied.The effect of void orientation on single-void evolution was also investigated.The multi-scale analysis revealed the following results.(1)Compared with TUSF,MDF achieved a higher efficiency in void closure.(2)The closing efficiency of the void increased with the increase in angle h(the angle between the Z and long axes of the void).(3)The closing efficiency increased with the increase in the orientation angle during the forging process.On the basis of the important role of the main stress in each forging step on the void closure,an integral formula of the main stress was proposed.When main compressive-stress integration reached-0.4,the closed state of the void could be accurately determined.展开更多
文摘The effects of the mold preheating and the silicon content of ductile iron on the percentage of carbides,graphite nodule counts and shrinkage volume were investigated.The results showed that the percentage of carbides and the shrinkage volume decreased when the mold preheating increased.The ductile iron with the carbon equivalent of 4.45 % and the silicon content of 2.5% without any porosity defects was achieved when the mold preheating was 450 ℃.Increasing the silicon content in the range of 2.1%-3.3% led to the increase in graphite nodule count and graphite size and the decrease in percentage of carbides.It is due to the increase in induced expansion pressure during the graphite formation with the increasing of silicon content.The suitable condition for casting a sound product of ductile iron without the riser at the mold preheating temperature of 300 ℃ is the silicon content of 3.3% and carbon equivalent of 4.7%.
基金This work is supported by National KeyR&D Program of China(Gran Nt oS.2016YFB0300400 and 2016YFB0300404).
文摘The void evolution of large-section plastic mold steel during multi-directional forging(MDF)was investigated using multiscale analysis.To simulate the forging process of the plastic mold steel(SDP1 steel)and realize micro-void reconstruction in a representative volume element(RVE),MDF experiment and void-characteristic evaluation of the SDP1 steel were carried out.Traditional upsetting and stretching forging(TUSF)and MDF were simulated to comparatively analyze the evolution of temperature,effective stress,and effective strain.By embedding RVE with a micro-void and using boundary condition by point tracking into the forging process,the single-void evolution in TUSF and MDF was studied.The effect of void orientation on single-void evolution was also investigated.The multi-scale analysis revealed the following results.(1)Compared with TUSF,MDF achieved a higher efficiency in void closure.(2)The closing efficiency of the void increased with the increase in angle h(the angle between the Z and long axes of the void).(3)The closing efficiency increased with the increase in the orientation angle during the forging process.On the basis of the important role of the main stress in each forging step on the void closure,an integral formula of the main stress was proposed.When main compressive-stress integration reached-0.4,the closed state of the void could be accurately determined.
