Study On Repair Of Process And Performance For Cylinder Block By Laser Technology

Cylinder block,which occupy an important position in the engine,is the main body and frame of the engine.Recently,with the requirement of lightweight,the wall thickness of cylinder blocks is further reduced,which undoubtedly increases the casting difficulty for the cylinder block with casting difficulties.So,the leakage phenomenon is appeared in the casting cylinder block,which directly leads to the failure of the cylinder block,casing huge property loss and resource waste to enterprises.Therefore,it is necessary to seek the new method to process the cylinder block to reduce the cost.The traditional repair methods and process methods are subjected to the poor weldability of the cylinder block material.From the point of the composition,the gray cast iron material has the characteristics of high carbon,high sulfur and high phosphorus;From the point of the mechanical property,it has the characteristics of low strength and basically no plasticity.Combined on the two characteristics,welding method and the welding stress caused by rapid cooling rate in welding process and uneven heating of welded parts,the repaired cylinder block has a large amount of repaired area,brittle and hard structure and cracks,which affects the use of the cylinder block.Laser repair method has the advantages of small heat-affected zone,high energy density,small beam diameter and little influence on the matrix.The laser repair method,which is superior to conventional repairs method,determines the small heated-affected zone,the metallurgical bonding with the matrix and reduces the influence on the matrix in the case of ensuring the strength.The way of adding inoculant makes the laser repair method combined with inoculant,reduces the difference between matrix powder and cladding powder,exerts inoculant effect in the molten pool produced by laser,changes the structure composition,refines the grain and reduces the content of carbide.The paper mainly studies the matching of laser repair method and hole size and the role of the inoculants in the repair process.In this paper,through the continuous improvement of repair methods,holes are divided by three part according to three repair methods,three repair methods:laser melting,laser additive repair and laser core filling are matched with the size of the holes.For each repair method,by studying the fusion process of the hole and the effect of repair process parameters on the repair quality,the optimal repair process parameters for each hole under this repair method were determined,and the microstructures are analyzed and the sealing property is verified.Additionally,in the improvement of laser repair,the effect of repairing performance on the repair performance is investigated by means of adding different contents inoculants.The inoculant changes the hardness and the tensile property of the specimens repair layer by grain refinement and variety in morphology and content of the carbide.When the content is 0.9 wt.%75ferrosilicon,the grain density is 58844/mm~2,the grain is smallest;the carbide content is reduced by 12.1%,the carbide is fine,uniform and rounded;the hardness is lowered 9.2%,the difference in hardness from the matrix is the smallest;the tensile performance is the best,and the elongation is the highest.