JPH07115143B2 - Mold coating agent for centrifugal casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides a base material for preventing seizure between a metal to be cast in a casting mold and a mold, and for preventing quenching of molten metal. The present invention relates to a coating agent for a centrifugal casting mold in which a refractory aggregate and a binder are mixed in a solvent.

[Conventional technology]

The above-mentioned conventional coating agents have mainly used diatomaceous earth as an aggregate and have exerted a heat insulating function due to the porous structure of diatomaceous earth. However, when casting a high temperature metal, since diatomaceous earth is insufficient in terms of fire resistance, on the first coating layer made of diatomaceous earth, zircon, alumina, mullite, chamotte, etc. having higher fire resistance can be used. A coating layer was formed by using an aggregate to form a coating layer.

[Problems to be Solved by the Invention]

However, it takes a lot of man-hours to form a two-layer coating mold composed of the first and second coating layers, and the second
Poor air permeability of the coating layer makes it difficult for the adhered water of diatomaceous earth to dry, and it has the drawback of easily inducing casting defects such as pinholes and scratches.Because it is necessary to use diatomaceous earth, There is a problem that the degree of fire resistance tends to be insufficient, and casting defects such as penetration and baking occur. Particularly, in centrifugal casting, which is the object of the present invention, the coating die is pressed due to the molten metal pressure during casting, and the pressure resistance of the first coating layer is insufficient, resulting in an extremely thin thickness. As a result, there is a problem that the heat insulating property is lowered.

An object of the present invention is to make it possible to improve heat insulation performance while maintaining high fire resistance of the coating agent.

[Means for Solving the Problems]

The characteristic composition of the mold coating agent for the centrifugal force casting mold in the present invention is that the refractory aggregate is composed of at least one of zircon, alumina, mullite, and chamotte, and 0.2 in the total amount.
The heat-resistant fiber material is contained in an amount of ˜37% by weight, and its effects are as follows.

[Action]

In other words, the refractory aggregate is zircon, alumina, mullite,
Consists of at least one chamotte and
By applying the mold coating agent containing 0.2 to 37% by weight of the heat-resistant fiber material to the inner surface of the mold, among the heat-resistant aggregate particles that withstand a large molten metal pressure due to centrifugal force, the fiber materials are A layer that is complicatedly overlapped and connected by a binder is formed on the inner surface of the mold, so that it is easy to create many voids between the overlapping fibrous materials, and many are formed in the applied coating agent layer. The voids formed form an air-containing layer.

Moreover, the drying of the coating mold is promoted through many voids, and the air permeability is improved.

〔The invention's effect〕

Therefore, the combination of the aggregate particles having high heat resistance and the heat resistant fiber material can withstand a large molten metal pressure in centrifugal casting and can obtain high heat insulation performance without being crushed.

In addition, the air permeability of the coating mold is improved, and it is possible to prevent the occurrence of casting defects (pinholes, scratches, etc.) due to water in the coating mold.

In addition, since the fiber material exerts a cushioning effect that absorbs vibration during centrifugal force casting, the molten metal in the mold can be gradually cooled without applying undue stress. It has become possible to manufacture higher quality cast products.

〔Example〕

 Next, examples of the present invention will be described.

A binder is added to a cylindrical mold for centrifugal force casting as the mold coating material for forming a mold coating agent layer by spraying the inner surface of the mold with a nozzle while rotating the mold around its axis. And the high temperature refractory aggregate in a weight ratio of 1: 0.
It is set to be 5 to 1.5.

Then, in an aqueous solution containing the binder, 0.3 to 20 wt
% Fibrous material is added as part of the aggregate. The fibrous material is preferably a refractory inorganic fiber, for example, alumina, mullite, chamotte, silica, made of at least one kind of refractory fiber such as zirconia or carbon fiber, the length of 5mm or less is used. . That is, in the work of spraying the mold coating agent onto the mold, if fibers having a length of 5 mm or more are mixed in the mold coating agent, the spraying tends to be difficult.

The aggregate contains, in addition to the fiber material, a refractory powder or granular material made of at least one of alumina, zircon, silicon oxide, chromite, mullite, chamotte, and the like.

The binder is water containing at least one of bentonite water obtained by swelling bentonite of about 0.5 to 7 wt% in water, kibushi clay, sodium aluminate, water glass, colloidal silica and the like. .

In the end, the coating agent was prepared by mixing the materials in the weight ratios shown in the following table.

That is, when water (solvent) is 100 parts by weight, the solution containing the binder is 100.5 to 107 parts by weight, the aggregate is 50.15 to 160.5 parts by weight, and the total amount is 150.45 to 267.5 parts by weight. Is 0.2 to 37%.

An appropriate amount of anti-settling agent, surfactant, dispersant and the like may be added to the coating agent.

[Another embodiment]

As the binder, in addition to a material containing bentonite as a main material, a material containing kaolinite clay as a main material or a material containing a relatively heat-resistant synthetic resin as a main material may be used.

The refractory powder particles in the aggregate may be silicon nitride powder or graphite powder.

The coating type may be a multilayer coating type in which the refractory powder particles in the aggregate are the same and fibers are added only to the undercoat, or conversely, a multilayer coating type in which fibers are added to the topcoat only. In addition to water, alcohol-based and ester-based solvents are also conceivable.

Claims (1)

[Claims] 1. A mold coating agent for a centrifugal force casting mold in which a refractory aggregate and a binder are mixed in a solvent as a base material, wherein the refractory aggregate is at least zircon, alumina, mullite or chamotte. It consists of one kind and 0.2 in the total amount.
Mold coating agent for centrifugal force casting mold containing ~ 37% by weight of heat resistant fiber material.