Lost foam casting process for cast steel valve body

The lost foam casting process of cast steel butterfly valve body was studied and improved by numerical simulation, and ug8 The three-dimensional entities of lost foam casting and gating system of cast steel valve body were drawn by three-dimensional software. The reduction of liquid metal filling and solidification process and the prediction of defect location of cast steel valve body were carried out by ProCAST software. Firstly, the original process scheme of valve body casting is simulated and analyzed, and the simulation results are compared with the production results. The correctness of the software simulation is verified. Then the main process parameters of lost foam casting of cast steel valve body are optimized and improved, and finally the reasonable lost foam casting process of cast steel valve body is determined. Through the above analysis and research, the following conclusions are obtained:

(1) The original process adopts the central bottom pouring system, four risers are placed on the center line of the top large torus and one riser is placed on the small torus. Through the analysis of the mold filling and solidification process of the original process, combined with the solid rate method and direct analysis method, it is known that there are serious shrinkage cavity and porosity defects at the large rotating ring surface and hot joint of cast steel valve body lost foam casting, which shows that the original process pouring scheme is not feasible.

(2) Comparing the simulation results of the original process with the actual production results, it is found that the two results are basically consistent, which shows the rationality of the relevant parameter settings required for ProCAST software simulation, and also verifies the feasibility of using ProCAST software to simulate lost foam casting process.

(3) In view of the problems in the original process scheme, the two process schemes of top injection and bottom injection with inner gate on the side of cast steel valve body lost foam casting are compared. The results show that the top injection gating system will have air entrapment, which is easy to produce gas slag, and the shrinkage cavity and porosity are high. The filling of side bottom injection is normal, there is no air entrapment, and the shrinkage cavity and porosity are low. It is considered that the bottom injection gating system with side inner gate is more reasonable for the lost foam casting of cast steel valve body.

(4) The effects of pouring temperature, pattern density and negative pressure on the formation of shrinkage cavity and porosity defects in lost foam casting of cast steel valve body were analyzed by orthogonal experiment. The order of influence degree is as follows: pouring temperature > negative pressure degree > pattern density. It is concluded that when the pouring temperature is 1620 โ„ƒ, pattern density is 18kg / m3 and negative pressure degree is 0.05Mpa, the shrinkage cavity and porosity defects of cast steel valve body lost foam casting are the least.

(5) Based on the selected gating system and process parameters, the improvement measures of blank holder risers are placed on both sides of the top of the lost foam casting of cast steel valve body. The final simulation results show that the shrinkage cavity and porosity defects in the lost foam casting of cast steel valve body are eliminated.

By using ProCAST software to simulate and analyze the lost foam casting process of cast steel valve body, we can not only understand the mold filling, solidification and cooling process, but also find out and improve the root causes of lost foam casting defects of cast steel valve body, saving manpower and material costs. Its powerful analysis module can more intuitively understand the basic mechanism of lost foam casting of cast steel valve body, It provides convenience for technicians to formulate process.

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