The lost foam casting workshop uses lost foam negative pressure casting to produce the casting while grinding the lining plate with ordinary sand casting raw materials. Lost foam negative pressure casting greatly improves the surface finish, regularity and dimensional accuracy of the casting, and the internal structure is dense, which fully meets the quality requirements of casting assembly and use. The process design of negative pressure lost foam casting manganese steel lining plate is very different from the past. Sanzhuji makes the following summary according to the characteristics of the lost foam casting equipment combined with the design of the raw material grinding lining plate gating system and the vacuum negative pressure system.
1. Foundry Process Design Principles
1.1 Control the pouring system to be full all the time. The pouring process of negative pressure lost foam casting is a process in which molten steel is filled and the plastic mold is vaporized and disappeared. If the runner is not full, due to the limited strength of the coating layer, sand collapse is very likely to occur. , resulting in incomplete castings.
1.2 Control the molten steel to go back and forth from the bottom, which is conducive to smooth filling, and it is not easy to form an empty inner cavity.
1.3 Due to the suction effect of vacuum, under the action of gravity and suction, the filling speed of molten steel is accelerated, and the pouring system is suitable to be larger.
2. Form of gating system
Selection of pouring methods: vertical pouring, bottom pouring, casting spacing 70~100mm, cross-sprue section size 70×60mm, sprue section size 70×70mm, if the pouring head is larger than 200-250mm. Be sure to set the pouring cup. The main function of the sprue cup is to store molten steel, so that the sprue section is filled instantly, and the molten steel flows neatly and stably. According to the size of the castings, it can be selectively arranged and combined to realize multiple castings in one box.
2.1 The difference between negative pressure lost foam casting and sand casting is that general steel castings are open, while negative pressure lost foam casting uses a closed system, and it must be closed at the inner gate. Mainly due to the fact that the runner before the sprue must be kept full.
2.2 The size and opening position of the inner gate
The molten steel enters the mold, the plastic mold begins to burn and vaporize, and a temporary cavity is formed at the front end of the liquid flow. In order to prevent molten steel from high-temperature radiation melting model, forming a larger cavity and collapsing sand, the design speed of molten steel filling is roughly the same as the speed of model disappearance, and the speed of molten steel filling is suitably fast. The inner gate is slightly larger than in previous designs. The location of the inner gate should be 20-30mm from the lowest pouring position of the casting. According to the design of the gating system of ordinary sand casting, the size of the ingate is calculated. After enlarging <1/3, the cross-sectional size of the ingate is 30×20mm. In order to prevent the casting and the runner from being too close, the model is deformed and melted at high temperature, and the inner gate is appropriately lengthened, and the design length is 5Omm.
3. Negative pressure selection
When pouring, pay attention to adjust and control the negative pressure in the range of 0.02-0.03Mpa, and keep the same negative pressure for about 10min after pouring.
4. Pouring Precautions
4.1 Tips for pouring: Instantly fill the pouring cup, fast and continuous flow
At the beginning of pouring, it is necessary to pour in a large mouth to ensure that the pouring cup is filled immediately, so the pouring opening of the bottom pouring ladle is 50% larger than that of the ordinary ladle. The flow must not be interrupted. Keep pouring cups full at all times. If the flow is interrupted, the inhaled gas will cause sand collapse or pores, resulting in the scrapping of the casting.
4.2 The pouring temperature is slightly higher
Due to the effect of vacuum suction, the heat of molten steel in the sand box is dissipated, and the heat is consumed by the melting and gasification of the plastic mold, so the pouring temperature is 30-50°C higher than that of sand casting.
4.3 Packing
Unpack 0.5-1.0 hours after pouring.
4.4 Advantages and disadvantages
The negative pressure lost foam casting raw material grinds the high manganese steel lining plate, which effectively controls the defects such as sand sticking and draping on the surface of the casting. Although the lining plate has no riser feeding, the internal organization is dense, and there are no defects such as pores and shrinkage holes. Achieving the quality grade of high-quality products. At the same time, the batch production efficiency is greatly improved, and a lot of raw materials such as sand boxes, sand, clay and the corresponding manpower are saved. The disadvantage is that the model is deformed, the consumption is large, and the cost is high. Therefore, the random inspection of the model should be strengthened at any time.
Qingdao Sanzhuji Equipment Manufacturing Co., Ltd. specializes in the production of Green Sand Molding Line,Self-hardening sand molding line,foundry machines,Sand molding machine,Sand casting equipment,sand mixer,GS high efficiency rotary mixer,Resin sand mixer,no-bake resin sand mixer,Jolt squeeze molding machine/Jolt-squeezing moulding machines,Multi- Piston Moulding Machine/Hydraulic multi-piston moulding machine,sand casting molding machine,sand reclamation equipment，foundry molding machine,flaskless moulding machine,shot blasting machine,dust collector,according to the amount of old sand recovered Carry out plan customization, and provide sand reclamation equipment installation, commissioning, and training. Welcome guests to visit the factory.
