The problem of sand holes in castings is a problem that many manufacturers of cast iron platforms,motor test platforms,test bench bases,and test iron soleplates have been sick before,and some are still facing or may even face in the future.This problem is the problem of sand holes in castings.So how should we control the problem of sand holes in castings?

 

　　Note:Why can't sand holes in cast iron platforms,motor test platforms,test bench bases,and test iron base plates be eliminated?This is because for sand casting,sand holes are associated with it.As long as there is sand casting,sand holes are a problem that cannot be eliminated for a long time,so the word"control"can only be used instead of"elimination".

 

　　That is to say,it is normal for castings to have sand holes,but when the existence of sand holes affects the performance of the castings,such as strength reduction,casting leakage issues,or customer dissatisfaction,it is a serious problem.You need to take effective measures to control it.

 

　　Once controlled,sand holes in the casting will be greatly reduced,so to what extent?

 

　　The principle is that the minimum number,area,and size of sand holes can meet the acceptance standards without affecting the use of customers;Due to poor control,the number of sand holes is too large,the area is too large,and the scale is too deep.Such sand holes will lead to direct scrapping of the casting.Because this degree of sand holes is very dangerous,it is necessary to strictly prevent and control the sand holes on the cast iron platform,motor test platform,test bench base,and test iron bottom plate casting.Fighting against sand holes is a long-term task for sand mold casting workers.Given this,how should we control sand holes from the source?

 

　　This requires a clear understanding of what sand holes are and what their characteristics are.

 

　　What is a sand hole?

 

　　The so-called sand hole refers to the hole containing sand particles on the surface or inside of the cast iron platform,motor test platform,test bench base,and test iron bottom plate,which is called sand hole.According to its location,it can be divided into surface sand holes and internal sand holes.Surface sand holes can be directly identified with the eyes,and internal sand holes can only be detected through ultrasonic or radiographic testing,or can only be exposed after processing.

 

　　The shape of the sand hole is extremely irregular,and the inner cavity is not as smooth as the pores,nor is there a very irregular and obvious dendritic tip like the shrinkage and porosity holes.Moreover,the sand hole is sometimes very similar to the slag containing holes,and it is often difficult to distinguish between the two.

 

　　Sand holes can exist in isolation and often accompany sand drop,sand inclusion,sand washing,and sand squeezing.They form a one-to-one correspondence with sand holes,that is,sand drop,sand inclusion,sand washing,and sand squeezing.As long as they exist,this is the definition and characteristics of sand holes,and the protruding characteristics of sand holes are the presence of sand particles,sand blocks,or sand masses in the hole.

 

　　Now that we understand the definition and characteristics of sand holes,how should we control sand holes on cast iron platforms,motor test platforms,test bench bases,and test iron base plates?

 

　　Since there are sand particles,sand balls,or sand blocks in the sand hole,it requires casting engineers to find out where the sand comes from,just like public security personnel do when solving a case.Once the source of the sand is found,the method for controlling the sand hole is found.

 

　　How many ways can sand come from?It should be said that there are generally six ways and six sources.

 

　　A good source of sales is the low surface strength of sand molds or sand cores,and the sand on the mold walls or sand cores cannot withstand the erosion of high-temperature liquid metal and peel off.

 

　　The excellent source is due to the unreasonable design of the pouring and pouring system,resulting in sand dropping,sand flushing,sand squeezing,and coating peeling in the pouring and pouring system.

 

　　The third source is sand falling,sand flushing,sand squeezing,and sand caused by coating peeling in the mold cavity,such as sand squeezing due to too small core head gap reservation.

 

　　The fourth source is that the pouring speed is too fast,and the impact force of the liquid metal is too large,causing sand particles to fall off the mold wall or sand core.

 

　　The fifth source is caused by the carelessness of the box closing operator.For example,the floating sand in the mold before and after core lowering cannot be blown clean,or the wall of the open vent hole,as well as the virtual sand and sharp sand in the mold,have not been cleaned in a timely manner,or the virtual sand and sharp sand in the mold and on the pouring riser have not been blown off,resulting in falling down again after box closing or during the pouring process;Or the sand may fall off due to vibration or impact during handling or pressing the box.

 

　　The sixth source is caused by foreign sand falling from the open riser,vent,or sprue after the box is closed.

 

　　It can be said that the six pathways above are sources of sand.Controlling sand particles,especially the source of deadly sand balls and blocks,is the key to solving the problem of sand holes in cast iron platforms,motor test platforms,test bench bases,and test iron soleplates.Due to the shallow size of sand holes formed by isolated loose sand particles,they will not cause scrap of cast iron platforms,motor test platforms,test bench bases,and test iron base plates.Most of the surface is not smooth,and only sand holes formed by sand blocks and agglomerates are fatal to the casting.