Research On 4G1 Cylinder Cover Workability By Low Pressure Casting

This thesis adopted method of changing chemistry composition, increasing modification treated, optimizing heat treatment technique, it got the rule how the various parameters influence the rigidity of the casting of 4G1 cylinder cover and found the factor influence machining ability by analyzing microcosmic structure using the NSOM and SEM. The method has been proved by production that it can improve the workability, satisfy user's request.First, it studied how the change of the elements of AC4B alloy influence the rigidity of the homemade casting of 4G1 cylinder cover. The alloy was configured based measuring the chemical composition of the CKD workpiece imported from Japan and the homemade casting of 4G1 cylinder cover, then cast two group of samples, and measured the rigidity, carried contrast test according to the same standard(480±10℃,1-2h) after processing. The result indicated that the chemical composition of Dong'an cylinder cover AC4B alloy was controlled in the filed of set standard composition, but the CKD workpiece imported from Japan was differ from the set standard, for the quantity of the intensifying Mg,Cu was going beyond the limit, it accounted for that the corporation adjusted the chemical composition of the alloy for improving the quality of the casting in the process of production, then the rigidity was improved as adding the quantity of the intensifying phase Mg, Cu, but the result still could not reach the degree of workability request.Secondly, it studied the modification treated of AC4B alloy intensified phase how influence the rigidity of the homemade casting of 4G1 cylinder cover. Point out as a result:the big perfoliate crack in the casting is disappeared after adding the Sr modification, but accompanying with the obvious increase of pinhole and shrink pine, theα(A1) dendritic crystal become more circinal and thin. Si phase become from long acicular structure to erratic granular structure after modification, and Sr modification appeared to an decay state, it was proved through the phenomena of Si phase casting turned into acicular structure in the upper cast; the fracture mode of the inmodification treated fracture appearance is cleavage fracture, it has inferior toughness; the fracture appearance after modification treated appeared majoring in dimple and cleavage fracture, it has better toughness; the rigidity of casting after modification treated improved, but it still could not reach to process the degree of hardness request of 70HB.Finally, it studied adjusting heat treatment influence the rigidity of the homemade casting of 4G1 cylinder cover. It implied: Changing heat treatment parameter, from the quenching + age treatment to 490℃±10℃, insulating 3 hours, and carrying the baking treatment of strengthen air-cooled, the rigidity of casting baked improved as the time went by, but it improved slowly, when the placement time of the casting baked is more than 20 hours, its' brinell hardness is more than 70HB, generally undulates up and down in the 80 HB, it was inferior to the rigidity 85.6HB of the CKD workpiece imported from Japan, but its workability can satisfy the request of Dong An-Mitsubishi company.