Sand sticking to malleable cast iron parts is a casting defect caused by metal penetration. It is the result of the destruction of the balance of dynamic pressure, static pressure, friction and capillary force at the interface between the mold and the metal. This is one of the common defects of malleable cast iron parts. For negative pressure solid plastic casting, due to the effects of vacuum suction and high temperature pouring, the permeability of liquid metal is much stronger than that of sand casting, and it is easy to penetrate into the mold through the coating. Therefore, the following points should be noted during the pouring process:

(1) The vacuum is too high or the density of the mold sand near the pattern is poor;

(2) The pouring temperature is too high;

(3) When the coating is too thin or the coating is uneven, malleable cast iron parts are prone to sand sticking. Especially when iron balls are used as molding materials, due to their low fire resistance, it is more likely to produce sand sticking on large planes, inner holes or other dead corners of malleable cast iron parts.

Due to the particularity of the molding principles of processes such as negative pressure molding and dry sand molding, metal penetration defects are more serious. Some malleable cast iron parts have not been solved for a long time, which brings difficulties to production. People have conducted a lot of research on the formation mechanism of metal penetration defects in ordinary sand mold malleable cast iron parts. The magnitude of various forces on metal penetration defects in sand casting was quantitatively analyzed, and the criterion for metal penetration defects – metal permeability coefficient – was proposed. The problem of metal penetration defects caused by more pores in the sand mold was studied and solved; the failure mechanism of the coating showed that the physical and chemical dissolution and erosion of the coating by liquid metal and the thermal stress caused by the different thermophysical properties of the simulated material were the two main reasons for the high-temperature failure of the coating. The problem of porosity was solved.

There are two differences between negative pressure full-mold casting coatings and ordinary sand casting coatings:

(1) Negative pressure full-mold casting coatings are in point contact with the molding sand, while sand casting coatings penetrate into the sand mold to a certain depth. After drying, the coating is nailed into the sand mold and is in close contact with the molding sand particles.

(2) The outside of the coating is dry sand and does not contain adhesive.

At present, the market size of malleable cast iron parts is getting bigger and bigger. Malleable cast iron parts are part of engineering machinery. Many construction workers know little about some characteristics of steel fasteners. They only know that steel fasteners are indispensable parts, but they don’t know what characteristics they have. The following editor will briefly introduce them to you.

The wholesale factory of steel fasteners is an important part of ensuring the safety of construction machinery and protecting personnel and equipment. It is an indispensable part of construction with its low cost and great effect. Steel fasteners have different characteristics in different models, and their tensile strength is also different. Under different conditions of use, different types of steel fasteners can be selected to ensure their efficiency.

First of all, the fasteners of malleable cast iron parts have a safety guarantee function. In terms of anti-slip function, it also ensures that the steel pipe will not slip when it is bonded with the building fastener. In terms of the maintenance of malleable cast iron parts, the whole building fasteners adopt double anti-rust treatment of galvanizing passivation, which has strong anti-rust ability and long service life. Therefore, it will not rust and damage, and the maintenance after construction is also very convenient, which greatly reduces the maintenance cost.