Two sides of precision steel casting

Precision steel casting refers to parts made of cast steel, similar to cast iron properties, but better than cast iron strength. The defects of porosity and inaccurate Angle positioning are easy to occur in the casting process of steel casting, and the phenomenon of casing fracture may occur in long-term use.

1. Advantages

One of the advantages of steel casting is the flexibility of the design, the designer has the freedom of design choice for the shape and size of the casting, especially for the parts with complex shapes and hollow sections, and the cast steel can be manufactured using the unique process of core. Its forming and shape change is very easy, and the conversion speed from the drawing to the finished product is very fast, which is conducive to rapid quotation response and shorten the delivery time. The perfect design of shape and quality, the minimum stress concentration coefficient and the strongest overall structure, all reflect the flexibility and process advantages of steel casting design:

1) Steel casting metallurgy manufacturing adaptability and variability, can choose different chemical composition and organizational control, adapt to a variety of different engineering requirements; Mechanical properties and performance can be selected in a large range through different heat treatment processes, and has good welding properties and processing properties.

2) The isotropy of the cast steel material and the overall structure of the cast steel are strong, thus improving the engineering reliability. Coupled with the advantages of lightweight design and short delivery time, it has a competitive advantage in terms of price and economy.

3) The weight of steel castings can vary within a wide range. The small weight can be only tens of grams of investment precision castings, while the weight of large steel castings can reach several tons, tens of tons or even hundreds of tons.

2. Disadvantages

(1) Uneven organization. After the injection of liquid metal into the mold, the first layer of liquid metal in contact with the mold wall has the fastest temperature drop, so it quickly solidifies into finer grains. With the increase of the distance from the mold wall, the influence of the mold wall is gradually weakened, and the crystals grow into parallel columnar crystals along the direction perpendicular to the mold wall phase. In the central part of the casting, the heat dissipation has no significant directionality, and it can grow freely in all directions until it contacts each other, so the equiaxed crystal region is formed. It can be seen that the structure of the casting is not uniform, in general, the grain is relatively coarse.

(2) The tissue is not dense. The crystallization of liquid metal is carried out in the way of tree branch growth, and the liquid metal between the branches finally solidifies, but the branches are difficult to be completely filled by the metal liquid, resulting in the general uncompactness of the casting. In addition, the liquid metal in the injection mold can also form loose or even shrinkage holes if the volume shrinks and is not adequately supplemented during cooling and solidification. Graphite in cast iron often appears in larger sheets, balls or other shapes, and can also be regarded as an undense structure.

(3) Rough surface. The surface is generally rough, can not be compared with the machined surface, and the shape is more complex.