Research On The Influence Of Process Factors On The Shrinkage Defects Of Large Castings And Anti-shrink Process

Large castings due to the unique structure and process,the probability of casting shrinkage and shrinkage defects is much higher than other castings,Based on the practical problems of shrinkage defects of large gray iron castings,large tonnage of castings(generally more than 10t),high production costs,such as the existence of shrinkage defects,resulting in considerable economic losses.Therefore,the large gray iron castings for the appropriate process design,to meet the use of performance,based on the reduction of shrinkage defects is very important.This article from the company's large gray iron castings column shrinkage defects of reality,the relevant factors of shrinkage cavity and shrinkage porosity are analyzed.The relationship between the factors and the shrinkage defect depth and the area of the cast iron is obtained from the aspects of the composition of the molten metal,the temperature of the molten iron and the mold condition.The test results are analyzed and summarized,and it is concluded that increasing the carbon and silicon content in a certain range,the appropriate increase of sulfur content,reducing the temperature of the molten iron and phosphorus content can reduce the depth of shrinkage defects of castings,increasing the tensile strength of the sand can reduce the shrinkage depth and area of the castings.According to the domestic and foreign material and our factory reality,it is dicussed that the relationship between the operating performances and anti-shrink process factors including the aspects of the composition of the molten metal,baked hot metal and pouring temperature,the mold condition.Combined with the analysis of the test results,based on the purpose of shrinkproof and it is determined that related factors of shrinkproof process control range ensuring the use of performance under the premise:carbon equivalent of 3.6%to 3.8%,silicon-carbon ratio of 0.75;non-frangible parts of the sulfur content of 0.06%?0.08%more appropriate,easy to crack pieces of sulfur is minimized;phosphorus content is generally taken 0.03%0.06%,easy to sticky sand and low-compactness requirement can select an upper limit;baked hot metal temperature as far as possible in 1400?,casting temperature in 1260?-1360? or so;To ensure that the tensile strength of sand is not less than 6Kg/cm2 but not more than 11Kg/cm,the amount of resin control in the 0.9%to 1.3%;at the same time,improving the sand compaction and the use of A+B curing agent,can improve the casting surface and shrinkproof performance requirements.Through the study of domestic information and the actual production of our plant,you can cast system type selection and riser settings,to improve the performance of casting shrink-proof.Through the use of rain and staircase pouring system and special riser,such as Insulating riser and Heat insulation riser can improve the filling effect;for the casting riser design wall thickness smaller and more uniformly distributed follow the sequential solidification principle,while the larger wall thickness and wall thickness changes larger castings reference equilibrium solidification principle,can improve the design efficiency and accuracy of riser,reduce the tendency of shrinkage defects of castings.Finally,taking the typical large-scale cast iron ingot mold and beam as an example,combining the research results of this paper,the relevant anti-shrink process plan is designed to discuss the design steps and methods of the large-scale iron castings shrink-proof process,taking into account the large-scale cast iron beam anti-shrink process design Complexity,the use of InteCAST analysis software,the beams of the existing process optimization program simulation,after repeated tests verify that the final shrinkage of the program,the effect is good.