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Fabrication Technology and Problem Solution of Ductile Iron Castings

In the past, in the process of processing ductile iron castings, because some technologies have not been applied, the quality of castings can not meet the reasonable requirements. But with the surface microporous infiltration technology, many problems have been solved properly, so that the ideal ductile iron castings can be produced.

The higher the technology content, the better the performance of the products. For example, nodular iron castings, the quality of finished products has been improved significantly since the application of microporous sealing technology in the production process. Whether it is physical properties such as hardness, strength, toughness or chemical properties such as wear resistance, high temperature resistance and corrosion resistance, it has been greatly enhanced by this technology. In fact, this technology is easy to operate, as long as the reasonable use of vacuum infiltration hot water solidified microporous sealant, can make nodular graphite castings thin-walled, can withstand the role of various conditions. At present, surface microporous infiltration technology is generally used in the processing of ductile iron castings in order to obtain appropriate production results.

When talking about the manufacturing process of ductile iron castings, we have to mention the technology of liquid metal filtration. Especially in the field of medium and Small Ductile Iron castings, the application of filters provides a strong guarantee for good casting quality, which is the relationship between ductile iron castings and filters. The following is a brief introduction to the production process of ductile iron castings.

1. Weak links in the manufacturing process of ductile iron castings

In casting production, when liquid metal is injected into the mould cavity by an insulating furnace, any turbulence will lead to thin oxide scales on the surface of nodular iron castings. This is an irreparable defect, which not only reduces the surface quality of ductile iron castings, but also prevents pressure testing due to the leakage between the two walls.

2. Purpose of using filter in forming process of ductile iron castings

It is important to know that turbulence occurs largely because of the presence of impurities. To avoid the formation of oxide scales, turbulence must be prevented. In the final analysis, impurities in metal solutions must be removed. The use of filters plays a role in this respect. It can filter out the residues formed in the environment of each working procedure. Only when the metal solution is poured with high purity, can it be possible to obtain high quality ductile iron castings.

3. Filters for ductile iron should be selected as foam filters.

During the casting process, the foam filter can not only reduce the content of non-metallic inclusions in ductile iron, but also significantly reduce the amount of sand used. In this way, not only the quality of ductile iron castings is improved, but also the cleaning capacity of castings is reduced.

On the other hand, the reason for choosing foam filters is that only it has the ability to prevent the formation of oxide scales. In the gating system, turbulence often occurs at the front end of the gate and the runner bar, so if a foam filter is placed across the runner bar, a metal stream will be blocked until the gate is filled.

In the production process of ductile iron castings, it is inevitable to encounter some technical problems which are difficult to solve, thus seriously affecting the quality of castings. For the problem technicians put forward some solutions, and then to verify the actual effect.

Sometimes the ductile iron castings will be seriously deformed and cracked. On the basis of checking its structure, the reinforcement and reinforcement plate can be placed in the place where the ductile iron castings are changeable and cracked. At the same time, the fillet size at the transition point can be appropriately increased without affecting the geometric size and performance requirements of the castings. In the design of casting system, more than two direct runners can be set up for heavy and bulky castings, so that the liquid metal can enter the mould quickly and smoothly, thus forming with high quality.

In addition, the ductile iron castings will also have serious sand sticking, resulting in a decline in the quality of the castings. The solution must start with the coating, because the fire resistance, strength and adhesion of the coating have a direct impact on the phenomenon of sand sticking. Careful inspection should be carried out before painting. At the same time, increasing vibration force, negative pressure and adjusting pouring temperature are helpful to improve the problem of bonding sand.

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