Solution to slag inclusion in lost foam casting(1)

Lost foam casting is currently one of the most advanced casting processes in the world. It is hailed as a revolution in the history of casting, and it plays an increasingly important role in casting production. Lost foam casting does have a wide range of adaptability, but not all castings are suitable for lost foam casting. Some castings can barely be made, but the process yield rate is low or the rejection rate is high. It also has technological limitations. For example, the foam pattern is easy to be deformed by force; compared with the traditional casting method, it also has the problem of pyrolysis and gasification of the foam mold. The defects of lost foam casting also need to be fully understood and eliminated. Common casting defects in lost foam casting include wrinkles, carbon black, deformation, sand sticking, collapse, pores, slag inclusion, cold partition and surface seepage of steel castings. Carbon, etc., combined with the welt of the lost foam casting process, Sanzhuji summed up the following points on slag inclusion defects:

1. Slag inclusion defects in lost foam casting
Slag inclusion defects refer to defects formed by dry sand, paint and other inclusions as molten iron enters the casting during the pouring process. On the surface of the machined castings, you can see spots of white or black-gray inclusions, distributed individually or in pieces. The white is quartz sand particles, and the black-gray is slag, paint, foam model residues and other inclusions after pyrolysis. . This kind of defect is commonly known as "sand ingress" or "slag inclusion", and it is a very common defect in the production of lost foam casting. Almost all factories using lost foam casting are widespread, and it is difficult to completely eradicate them. Only by taking a variety of measures and careful operation in each process can the "slag inclusion" be reduced to a very low level and satisfactory results can be achieved. After the lost foam castings are cooled and boxed before being cleaned, according to the surface conditions of the castings and the pouring system, it can be judged whether there are sand and slag inclusion defects. If the sprue cup, sprue, cross sprue, sprue and gate surface or connection, and the surface of the casting are severely sanded or have cracked sand, it is basically certain that the casting has slag inclusion and sand ingress defects. Smash the sprue rod or sprue bead, you can see white spots on the fracture, and in severe cases, the fracture will form a circle of white spots. Such castings, especially plate-shaped and round cake-shaped castings, will have white and black-gray spots on the processing surface after machining. If the process operation procedures are not strictly controlled, the castings produced will seriously affect the quality of the castings and the progress of the order completion.

2. Causes of slag inclusion and sand ingress defects
Sanzhuji combines the characteristics of sand casting equipment with the foundry. Long-term observations have proved that from the sprue cup, sprue, cross runner, inner runner to the casting, all parts may cause sand ingress, especially the pouring system and castings. The binding site. In the whole production process, the paint peeling and cracking on the surface of the white mold of the gating system, the paint peeling and cracking at the bonding part of the white mold, the paint peeling and cracking on the surface of the foam white mold, the sprue is not tightly closed and other factors are caused by slag inclusion and sand ingress. The most important cause of defects. Secondly, the selection of process parameters, such as the size of the net pressure head of the pouring system, the pouring temperature, the degree of negative pressure, the particle size of dry sand, etc., as well as the transportation process of the model and the packing operation, all have an impact on the slag inclusion and sand ingress defects of the castings. Great influence. Only by adopting systematic measures and careful operation in these links can the slag inclusion defects of castings be reduced and basically eliminated, and high-quality castings can be obtained. Overcoming the defects of slag inclusion is a systematic project.

3. Methods and measures to reduce and overcome slag inclusion defects
Sand ingress and slag inclusion defects are a major problem in lost foam casting production. At present, there are mainly three types of products that have been successfully produced by lost foam casting, namely, wear-resistant parts, pipe fittings and box castings, all of which are rarely processed or not processed. For castings with many processing surfaces and high requirements, the slag inclusion defect is a key problem that needs to be solved. Our experience is that measures can be taken from the following aspects to reduce and eliminate slag inclusion defects:

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.