Lab-Research On The Formation Of ADI From Horizontal Continuous Casting Ductile Iron Bar

Based on the lab research work, the paper, which gives a brief introduction to the advantages of producing ADI from Ductile Cast Iron Bar, will focus on the study of the producing process, the microstructure and the properties of ADI obtained from horizontal continuous casting ductile iron. In the paper, firstly, a comprehensive analysis of impact exerted by various chemical elements upon ADI will be made to determine the proper chemical composition, which will result in producing some samples. Secondly, in line with the advantages of horizontal continuous casting ductile iron bar, the parameters of austempering will be put forward to be applied in heating treatment, which is based on the curve of Time Temperature Transformation as well as curve of continuous cooling transformation. Thirdly, mechanic properties (tensile strength, hardness, etc.) of samples will be measured and changes in the microstructure will be observed and analyzed. At the same time, X ray will be employed in observation of microstructure and in determination of impact exerted by ADI techniques in different groups of samples to build up the process-microstructure-properties relation. The goal of research is to realize the parametrical design in the technique of austempering and to control the mechanical performance of ADI.The chemical composition of samples used in lab work: carbon 3.55%, silicon 3.28%,manganese 0.22%, sulphur 0.022%, nickel 1.02%, copper 0.75%, molybdenum 0.10%, phosphorus 0.034%.The research indicates that the stability of retained-austenite is affected by austenizing temperature and time while the content of retained-austenite and the extent of bainite change are affected by austempering temperature and time. Comparatively, the effect of time is stronger than that of temperature. For instance, a rise in the temperature of austempering is advantageous to upgrading extension rate, but not to improving hardness and tensile strength while a rise in the temperature of austenite conditioning is advantageous to upgrading tensile strength and hardness, but not to improving extension rate .Therefore, the conclusion can be safely drawn that if the parameters of austempering technique will stay at (890±5 ) ℃ × 2h+ (330±5 ) ℃ × 2h, ADI with comparatively good comprehensive mechanical performance will be made.