Nodular cast iron manhole cover is the most widely used metal nodular cast iron manhole cover in more and more mechanical equipment. However, different quality nodular cast iron well covers will have different results when used, which we must face up to. We can root out many factors affecting the quality of nodular cast iron well covers to formulate more effective correction methods, so that we can get the best use effect.

There are many factors affecting the quality of nodular cast iron well cover. The first is the design technology of nodular cast iron well cover. During the design, in addition to determining the geometry and size of the nodular cast iron well cover according to the working conditions and metal material properties, the rationality of the design must also be considered from the perspective of casting alloy and casting process characteristics, that is, obvious size effect and solidification, shrinkage, stress and other problems, so as to avoid or reduce the component segregation, deformation Crack and other defects.

Second, there should be a reasonable casting process. That is, according to the structure, weight and size of nodular cast iron well cover, casting alloy characteristics and production conditions, select appropriate parting surface, modeling and core making methods, and reasonably set up casting reinforcement, cold iron, riser and gating system. To ensure high-quality nodular cast iron manhole cover. The third is the quality of raw materials for casting. The quality of metal charge, refractory, fuel, flux, modifier, casting sand, molding sand binder, coating and other materials is not up to standard, which will cause defects such as pores, pinholes, slag inclusion and sand sticking on the nodular cast iron well cover, affect the appearance quality and internal quality of the nodular cast iron well cover, and scrap the nodular cast iron well cover in serious cases. The fourth is process operation. It is necessary to formulate reasonable process operation procedures, improve the technical level of workers and correctly implement the process procedures.

Cleaning of several parts on the surface of nodular cast iron manhole cover

1. Dust on the surface of nodular cast iron manhole cover

Steel castings are often made in dusty sites. There is often a lot of dust in the air, which constantly falls on the equipment surface. They can be removed with water or alkaline solution. However, dust with adhesion needs to be cleaned with high-pressure water or steam

2. Floating iron powder or embedded iron on the surface of nodular cast iron manhole cover

On any surface, free iron will rust and corrode stainless steel. Therefore, it must be removed. Floating powder can generally be removed with dust. Some have strong adhesion and must be treated as embedded iron. In addition to dust, there are many sources of surface iron, including cleaning with ordinary carbon steel wire brush and sand previously used on ordinary carbon steel, low alloy steel or nodular cast iron well covers, Glass beads or other abrasives shall be shot peened, or non stainless steel products mentioned above shall be polished near stainless steel parts and equipment. If stainless steel is not protected during blanking or lifting, steel wire rope, spreader and iron on worktable are easy to embed or stain the surface

Ordering requirements and post fabrication inspection can prevent and find the existence of free iron. ASTM standard A380 [3] specifies the rust test method for inspecting iron or steel particles on the surface of stainless steel. When it is required that there must be no iron, this test method should be used. If the results are satisfactory, the surface should be washed with clean pure water or nitric acid until the dark blue disappears completely

As pointed out in standard A380 [3], if the rust test solution cannot be completely removed, this test method is not recommended on the process surface of the equipment, that is, the direct contact surface used to produce human consumer goods

1: It is the design process of nodular cast iron well cover. In addition to determining the geometric shape and size of nodular cast iron well cover according to working conditions and metal material properties, the rationality of design must also be considered from the perspective of casting alloy and casting process characteristics, that is, obvious size effect, solidification, shrinkage, stress and so on

2: It is necessary to have a reasonable casting process, that is, according to the structure, weight and size of nodular cast iron well cover, casting alloy characteristics and production conditions, select the appropriate parting surface, modeling and core making method, and reasonably set the casting rib, cold iron, riser and gating system, so as to ensure the high-quality nodular cast iron well cover. In the casting production, It is necessary to control and inspect the quality of nodular cast iron well covers. First, the process rules and technical conditions from raw materials and auxiliary materials to the control and inspection of each specific product shall be formulated. Each process shall be controlled and inspected in strict accordance with the process rules and technical conditions. Finally, the quality of finished nodular cast iron well covers shall be inspected. Reasonable testing methods and appropriate testing personnel shall be equipped. I Generally, for the appearance quality of nodular cast iron well cover, the surface roughness of nodular cast iron well cover can be determined by comparing sample blocks

3: It is the quality of raw materials, metal charge, refractory, fuel, flux, modifier, casting sand, molding sand binder, coating and other materials for nodular cast iron well cover, which will cause defects such as pores, pinholes, slag inclusion and sand adhesion, affect the appearance quality and internal quality of nodular cast iron well cover, and scrap the nodular cast iron well cover in serious cases. The fourth is process operation, It is necessary to formulate reasonable process operation procedures, improve the technical level of workers and implement the process procedures correctly