Casting sharing - What is the "cloud spot" defect of castings?

What are cloud spots?

Cloud spots are caused by the chemical composition and metallographic structure of the casting during the solidification process. Evenly distributed areas of abnormal tissue. These areas may appear water-soaked and are usually light black or another color. Because these areas are unevenly distributed and resemble clouds or streaks, they are called cloud spots. Spots often appear on the inner surface or end face of the casting, especially in thick and large parts such as centrifugally cast cylinder liners.

Yunban is How was it formed?

Chemical composition segregation: During the centrifugal casting process, Due to the centrifugal force, the sinking and floating speeds of particles of different weights in the molten metal (such as sulfur, manganese, phosphorus and other elements) increase, resulting in uneven distribution of these elements in the casting, forming segregation. High, such asP, B, Cr, S, etc.

Graphite Polymerization: Graphite is an important component of cast iron, but under certain conditions, graphite will be segregated, resulting in excessive graphite content in local areas of the casting, forming cloud spots. This segregation may be caused by factors such as cooling rate and metal liquid flow state.

Solidification conditions: The solidification conditions of the casting also have an important influence on the formation of cloud spots. For example, if the cooling speed of thick and large parts of the casting is too slow, or the molten metal is disturbed during the solidification process, it may cause cloud spots.

What impact will cloud spots cause?

The presence of cloud spots will seriously affect the performance and quality of castings. First, the cloud spot area The uneven organizational structure may lead to a decrease in the mechanical properties of the casting, such as a decrease in tensile strength, hardness and other indicators. Secondly, cloud spots may also affect the processing performance and service life of the casting.

How to prevent The appearance of cloud spots?

Optimize chemical composition: By adjusting the chemical composition of the casting, the content of elements that are prone to segregation can be reduced. Increasing the content of infinite solid solution elements can help reduce the occurrence of cloud spots.

Improve the pouring process: reduce pouring Disturbance and inclusions introduced during the process help to improve the uniformity of the casting structure.

Control solidification conditions: By adjusting the solidification conditions such as cooling rate and pouring temperature, the casting can form a uniform and stable organization during the solidification process, reducing the generation of defects such as cloud spots.

Strengthen quality inspection: Strengthen quality inspection during the casting process, promptly discover and deal with defects such as cloud spots, and ensure that the quality of castings meets the requirements.

Casteks has many years of casting experience and will carry out strict quality control in casting design, casting production, heat treatment, machining and other links, aiming to reduce the probability of defects in customers' products. Casteks has always regarded technological innovation and quality monitoring as the driving force for the development of casting, and strives to provide customers from all walks of life with products and services that go hand in hand with quality and efficiency. If you have casting needs, please come to consult.