Experimental Research On The Surface Strengthening Technology Of Copper Crystallizer Surface

With China steel production increased, continuous casting productiondevelopment advance rapidly, crystallizer consumption is more and morethan before. Copperplate as one of the key parts of the crystallizerconsumption is also increasing rapidly. This is not only increasing the cost ofcontinuous casting, but also consuming a lot of copper alloy. It is necessary todevelop a new surface strengthening technology to improve crystallizercopperplate surface properties for prolong its work life. Through lasercladding technology preparation an excellent high temperature wearresistance cladding layer on copperplate surface, which can lay thefoundation for the application of new technology on crystallizer copperplatesurface.The different materials formation cladding layers have differentproperties, and the copperplate work area is so very large that temperaturedistribution is different in different area when it works. For selecting theoptimal laser cladding process and cladding materials, the finite elementnumerical simulation is used to calculate the temperature field distribution oncrystallizer copperplate surface during its normal working process. The results show that: width and narrow crystallizer copperplate hot surface, coldsurface and cooling water channel temperature field distribution trend are thesame, but their specific temperature are different. The temperature of thecooling water not reached boiling point, so it is not boiling in the channel.According to the results of the work surface temperature field, it can bedivided into three regions, which are meniscus zone, close contact zone andair gap zone. They are located in100mm-250mm,250mm-450mm and below450mm from the top surface of copperplate. Width copperplate highesttemperature is312.51℃located at the contact line, and the narrowcopperplate highest temperature is399.27℃located at distance30mm tothe contact line.The microstructure, physical-chemical properties and work principle ofcrystallizer copperplate used in Baosteel Company are investigated withmuch physical, chemical and electrochemical detecting means. Throughanalysis the difficulties of laser cladding on copperplate surface, severalmethods to improve the interface bonding quality between cladding layer andcopper substrate are researched, like using different light laser, substratepreheating and copper substrate surface pretreatment three methods. Thecrack is a serious defect because that crack once produced and extended willcause the cladding layer performance greatly decreased. Appropriatesubstrate preheating temperature and certain ultrasonic vibration powermethods can control crack generation.Based on the optimum process parameters, Fe-based、Ni-based andCo-based self-fluxing alloy powder are used to clad on the Cu-basedsubstrate surface. The macro morphology, microstructure, chemical composition and mechanical properties are analyzed. The relationshipbetween microstructure and performance of the laser cladding has also beenexplored. At the same time the plating process on copperplate is introduced.The cladding layer and plating layer properties are compared, such asmicro-hardness, softening and thermal shock properties. The results showthat: Ni-based cladding layer hardness is1.5times high than Ni-based platinglayer,6.5times high than Cu-based substrate. Ni-based cladding layer softentemperature is higher than600℃,while Ni-based plating layer softentemperature is about350℃~400℃.Through thermal shock test, Ni-basedcladding layer hardness is almost the same as before, but Ni-based platinglayer hardness is change tremendously, which has decrease about46.4%.Laser cladding layer has better excellent thermal shock property, and moresuitable for large temperature gradient work conditionsLaser cladding is very agile and easy to realize the method of differentdistrict cladding different materials. Cladding layer has high hardness andsoftening temperature, excellent wear resistance and thermal shock resistanceproperties. So laser cladding process as crystallizer copperplate surfacestrengthening treatment technology is an ideal choice.