The Research Of Roll Remanufacturing Based On Plasma Transferred Arc Welding Technology

As one of the key components in metallurgical industry,roll has high added value and is prone to failure in service.How to prolong the service life of roll and reduce the loss of materials has always been a concern of rolling enterprises.As an advanced surface engineering technology,plasma transferred arc welding(PTAW)has broad application prospects in the field of remanufacturing and repairing failed rolls.Therefore,the research of roll remanufacturing based on PTAW was carried out in this paper,and two key problems restricting the further development of roll remanufacturing industry,such as thermal damage and fatigue cumulative damage,were explored and analyzed.The forms and causes of roll damage and failure was analysed and the optimal process scheme of roll remanufacturing was discussed.Then,the comprehensive mechanical properties of cladding coating under the optimal process parameters was verified and analysed.Last,the optimal process parameters was applied to remanufacture failed roll.The results show that the powder feed rate is the significant factor which affects microhardness and wear volume loss of the coatings within the range of the tested process parameters.With the increase of powder feed rate,the microstructure of coatings is changed from columnar crystal to dendrite and equiaxed crystal,and the microstructure properties,microhardness and wear properties are also significantly improved.The optimal process parameters are given as below: main arc current is 100 A,travel speed is 70 mm/min,powder feed rate is 22 g/min.Under these parameters,the structure of cladding coating is equiaxed crystal,the hardness and wear resistance are improved remarkably,and the bonding property between cladding coating and substrate is good.The surface quality of the roll remanufactured and repaired by PTAW is good,and has no cracks and other defects.The influence of thermal damage on the microstructure and properties of substrate materials in remanufacturing and the effect of fatigue cumulative damage on the life of remanufactured samples caused by loading service history before remanufacturing were studied.The results show that The initial thermal damage causes the microstructure of the substrate material to be roughly divided into remelted zone,overheated zone,recrystallized zone,incomplete recrystallized zone,and the original substrate without phase transformation.Secondary thermal damage in the remanufacturing process has no significant effect on the width of each region in the heat affected zone,but has a certain influence on the grain size.The grains in the overheated zone will grow further,while those in the recrystallized zone will refine further.On the other hand,there is no significant difference in the crack initiation and propagation of cladding coatings for remanufactured samples with different loading history,which shows the substrate has high remanufacturing value.The fatigue resistance of the substrate decreases slightly with the existence of loading history,which is mainly related to the decrease of the average grain size in the overheated zone of the remanufactured sample due to cumulative fatigue damage.