Deformation Problems of Lost Foam Casting and Anti-deformation Measures of Typical Castings


Lost foam casting production methods because of the white mold and molding, which brings a lot of convenience, such as white mold molding, mold closing convenience, no sand core and other issues, but also because of the white mold and casting has brought a lot of problems. Such as deformation, pores, slag, wrinkled skin and other defects. Therefore, it is often said that lost foam casting is also a white mold and a white mold. How to coordinate the interests between the two is a problem in front of the foundry personnel.

Introduction of manhole cover manhole ring: maximum contour size ¢694mm, main body wall thickness 11mm, single weight 46kg, material QT500-7.

Acceptance criteria for manhole covers: large plane deformation control inWithin 1mm, the manhole cover is installed in the manhole ring, GB/T23858-2009 standard is installed, and the working load of 400KN is not damaged and the deformation meets the requirements. Figure1As shown:

Figure1

First of all, 1. we talk about the causes of deformation problems through the various links of lost foam casting.

1: The white die is deformed due to improper operation of the white die during the die-out process, that is, the initial deformation.

2: white mold in the drying on the drying rack when the deformation. Due to the strength and structure of the white mold itself, as well as the uneven drying rack, there is no necessary shaping measures to cause the deformation of the white mold.

3. The white mold is painted with paint and dried and placed unevenly, resulting in deformation of the appearance.

4: the deformation problem caused by the vibration of the yellow mold buried box.

No matter which link is deformed, it will lead to the scrapping of the final casting.

2. paper introduces several common anti-deformation measures.

1: Use white mold to punch it out and put it into the shaping room for shaping to prevent deformation. This measure requires a special shaping room to be placed after the white mold is placed. The disadvantage is that it occupies a large area. Even if the deformation of this link is controlled, it cannot be guaranteed that the following process will not be deformed. And this kind of casting in the production process of the operation process will be worried, everywhere beware of deformation problems.

2: Wooden bar or white mold tie bar, using wooden bar or white mold tie bar to prevent deformation, control the corresponding size, suitable for use in the pulling force position. It can effectively prevent the deformation of castings of certain structures. The disadvantage is that the cast castings will produce iron nodules in the wood strip, which is difficult to clean. As shown in Figure 2:

Figure2

3: For castings with large plane deformation problems, white mold tie bars are added to the mold, and two back-to-back pull anti-deformation measures are adopted. This method looks good, but it often fails to achieve the desired results in practice. For example, one of them is deformed and cannot be corrected, and even the other will follow.

4: runner anti-deformation measures, the use of the runner bonding to prevent deformation of the white mold.

5: the production of appropriate white mold bonding and anti-deformation tooling, so as to control the deformation problem.

3. the above deformation reasons and anti deformation measures, the following requirements are put forward for the deformation of manhole cover:

1: It can correct the deformed white mold just out of the mold.

2: Avoid bringing iron that is difficult to clean up like wooden bars.

3: It can well control the deformation problem in the whole process from white mold to yellow mold to buried box.

4: practice is relatively simple and practical.

Therefore, we use the combination of steel frame and resin sand block to achieve the anti-deformation and deformation correction of the well ring manhole cover.

4. specific production operation details

1: The steel structure bracket is made according to the structure of the casting, and the problem of convenient operation and placement should be considered. The steel frame material is 30x 30 3mm thick square steel.

As shown in the figure

2: Select the specified position on the bracket and stick the resin sand block. Cold glue is used for bonding in the middle. After the bonding is completed, put it into the drying room for drying for more than 3h to reach a certain strength.

3: Place a grinding wheel on a horizontal plane, and press the dried resin sand block on the grinding wheel to grind a large plane. As shown in Figure 3:

Figure3

4: resin sand block coated with cold glue, and then coated with a layer of heavy anti-corrosion epoxy curing agent. Place the white mold on the resin sand block and compact it with pressure iron. Check that there is no place where it is not tightly attached and pressure deformation occurs. Put it into the drying room and dry for more than 3h to ensure that the cold glue is firmly bonded. As shown in Figure 4:

Figure4

5: at this time can be brush paint drying. As shown in Figure 5:

Figure5

 

The deformation is well controlled after molding pouring, and there is no obvious sand sticking defect on the surface after shot blasting.

SummaryThis paper summarizes the deformation measures in the process of lost foam casting, from which a very practical anti-deformation measures of steel structure resin sand block support are recommended, hoping to solve the practical problems of the vast number of lost foam casting plants and realize the benefits.

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