Microstructure And Properties Of Ball Milling Liner Materials Produced By Squeeze Casting

In this paper,the problems of shrinkage defects,coarse structure and short service life of the ball milling liner produced by sand casting are discussed,a new method is proposed to make the lining board,which can refine the grain,eliminate the shrinkage and porosity,improve the mechanical properties and prolong the service life of the lining board,that is,squeeze casting(SC).For this purpose,two typical materials are selected as the studying object,which are low alloyed wear resistant steel ZG60Cr4MnMoCu and improved high manganese steel material ZGMn13Cr2.Using SEM,EDS,XRD,MLD-10B impact abrasive wear tester and other testing equipment,the characteristics of the structure,wear resistance and other mechanical properties of the lining material of SC are studied.The effect of specific pressure on the microstructure and properties of SC ball milling lining material and the advantage of SC ball milling liner compared with sand and metal gravity casting is obtained.In addition,the design scheme of SC process in ball milling lining is carried out.The complete SC ball milling linear process,the design of a special SC die,the SC machine and related ancillary equipment are designed.Finally,the numerical simulation and the virtual orthogonal experiment of the SC ball milling linear are carried out by using PROCAST.ANSYS is also used to check and optimize the SC mould.Conclusions are as follows:(1)The impact abrasive wear resistance of the chromium manganese molybdenum alloyed steel produced by SC is better than that of the metal gravity casting,the wear rate is only about 74%of the metal casting.The wear resistance of the SC chromium molybdenum manganese alloyed steel increases non-linearly with pressures increasing.When the pressure is low,the wear resistance increases significantly,while the pressure is higher than 130MPa,the wear resistance improves not obviously.(2)The wear mechanism of SC chromium manganese molybdenum alloyed steel is adhesive and abrasive wear at the beginning.Gradually,it develops into only abrasive wear.Finally it develops into a mixed process of abrasive wear and surface fatigue wear.(3)At the casting state,the wear resistance of SC ZGMn13Cr2 samples increases by 14.8%and 15.3%compared with the sand casting and metal casting samples respectively.After the heat treatment,This value becomes 8%and 14.8%respectively.(4)The squeezing pressure plays an important role in improving the grain size of ZGMn13Cr2.The larger the specific pressure,the finer the grain.However,the refining effect will gradually weaken with the increasing of the pressure.When the pressure increases to 228MPa,grain size will not continue to be refined.(5)The pressure has an inhibition effect on the carbide precipitation,the bigger the pressure,the smaller the precipitation of carbides.When the pressure increases to 140MPa,the M3C carbide will no longer appear and the appearing M7C3 carbide will be mainly distributed in the grain boundaries.(6)The processes for SC ball mill linear includes slag pouring scheme which consists of a flip package,a filter and a circular buffer chute pouring chamber.The pressurization scheme consists of the main cylinder pressurization mode and the lower cylinder and the pressure cylinder feeding.The exiting scheme is the lower pressure head drives the ejector rod to push the linear out of the mould.(7)The optimum technological parameters for the SC ball milling liner are as follows:the squeezing pressure is 230MPa,the filling speed is 46.167mm/s,the pouring temperature is 1500 ? and the mold preheating temperature is about 600 ?.Through the study on microstructure and properties of two kinds of typical liner materials,it shows that the ball milling liner produced by SC has great advantage in improving wear resistance,reducing casting defects and prolonging the service life.Besides,by the means of the analysis of the numerical simulation technology for liner design and scheme,it is doubtless that the SC can be used to manufacture the liner,which expands the scope of application of SC in black metal products.Furthermore,these efforts also play a positive role in promoting the application of SC in industrial production.