Vermicular graphite cast iron: features, production principle and technical characteristics

Vermicular graphite cast iron - This is a metal with mechanical properties superior to those of gray cast iron. The structure of this alloy does not contain lamellar graphite, but spheroidal graphite does. The mass fraction of spheroidal graphite inclusions is approximately 20%, while vermicular inclusions make up the majority of the graphite component, accounting for approximately 80% of the total graphite inclusions.

Vermicular graphite cast iron It has superior mechanical properties to gray cast iron, but occupies a middle ground between lamellar and spheroidal graphite materials. This metal (commonly known as vermicular graphite cast iron) is more easily cast than gray cast iron.

The graphite inclusions make the metal stronger and more ductile, improving its resistance to impact loads. Furthermore, the alloy has high thermal conductivity, making it suitable for use in heating system circuits. Thus, the combination of excellent mechanical properties and good thermal conductivity allows this cast iron to be used for castings used in applications subject to temperature fluctuations.

Vermicular graphite cast iron It is obtained by processing the melt of rare earth metals in the form of many alloying components, which are introduced into the ladle onto the metal stream.

To prevent the formation of ledeburite or cementite in the final product, secondary modification is performed after treatment with alloying elements, most commonly with 75% ferrosilicon. This type of cast iron is primarily cast in sand molds. The technology is similar to that used for gray castings, at temperatures of 1360-1400 degrees Celsius. Given this metal's low sensitivity to changes in wall thickness, it is possible to produce larger cross-sections (approximately 500 mm) while maintaining good mechanical properties. Vermicular graphite cast iron It is smelted in a similar manner to ductile iron. This metal is used in heavy and light engineering, and is also used in many housing parts and blocks (internal combustion engine blocks, etc.).

Marking of cast iron with vermicular graphite according to GOST

According to GOST, there are four main grades of this alloy. These designations are governed by the interstate standard GOST 28394-89 "Vermicular Graphite Cast Iron for Castings. Grades." This standard distinguishes:

• ChVG 30;
• ChVG 35;
• ChVG 40;
• ChVG 45.

The abbreviation "ЧВГ" stands for compacted graphite cast iron. The numbers in the designation convey information about the minimum tensile strength under tensile conditions. For example, ЧВГ 40 has a value of 400 MPa.

Additional information on the main brands of CVG is presented in the table below.