Research On Defects And Process Optimization Of Stainless Steel Precision Casting

In the process of investment casting for stainless steel,defects such as cracks,shrinkage,shrinkage holes,and sand sticking are common,leading to a significantly higher scrap rate of castings.Traditional optimization measures often rely on trial and error and empirical methods that lack theoretical support.This approach fails to achieve the desired production efficiency for castings.Therefore,the present study aims to investigate the causes of defects and proposes optimization methods by analyzing the flow and solidification behavior of 304 stainless steel alloy liquid during the investment casting process.The findings of this study will provide theoretical references and effective guidance for optimizing the actual production of stainless steel investment casting.The main research content is summarized as follows.(1)Establishing a mathematical model for the flow and solidification process of 304 stainless steel high-temperature alloy liquid.Based on the fluid mechanics theory of 304 stainless steel alloy liquid and an analysis of its physical properties,the filling process is described using continuity,momentum conservation,and energy conservation equations.In conjunction with numerical simulation techniques,analyze casting defects.(2)Investigating the causes of casting defects such as cracking,shrinkage,porosity,and sand adhesion.The formation of cracks is primarily attributed to stress exceeding the ultimate yield strength of the material,while the inhomogeneous internal shrinkage of the casting is the main factor contributing to shrinkage and porosity defects.Sand adhesion defects are primarily associated with pouring temperature,alloy impurity content,and static pressure.(3)Defect control and process optimization for various casting types.Two optimization strategies were devised for stainless steel elbow fitting castings.A comparative analysis revealed that optimizing the gating system and incorporating process aids led to effective mitigation of cracks at threaded hole locations.Shrinkage defects were identified in spherical ball valve castings,and a combination of shrinkage remediation measures,gating system structure optimization,and orthogonal test method-based process parameter adjustments reduced the maximum porosity to 2.29%.The casting’s flow and solidification processes were analyzed,and the gating system structure was enhanced by adding a riser and vent channel.Parameters,such as riser dimensions,minimum static pressure head,critical solidification fraction,and maximum shell shrinkage,were determined to eliminate defects.