Metallographic diagram of ZG30CrNiMo (as cast)

The wrought form of 30CrNiMo steel is widely used in the manufacture of component parts in the automotive and other industries due to its good combination of strength, toughness, and weldability. It is a low-alloy medium carbon alloy steel typically containing around 0.30-0.50% carbon, about 1.4% chromium, and 0.35-0.55% Molybdenum. The combination of these alloying elements provide this steel a variety of properties that make it a highly versatile material. These include its superior strength, toughness, good hot-workability and weldability.

The microstructure of 30CrNiMo steel generally consists of ferrite and pearlite. The pearlite is formed during the austenite-to-ferrite transformation process that occurs during the cooling of the steel. The microstructure can vary depending on the temperature and cooling rate of the steel. The tempered martensite microstructure is obtained when the steel is cooled rapidly, while a bainitic microstructure is obtained when the steel is cooled slowly.

The 30CrNiMo steel is much harder than ferritic and austenitic steels due to the manganese and chromium content, which gives it superior strength. This steel has great resistance to wear and tear and is also very corrosion resistant. This makes it ideal for applications where strong materials are required and where there is a potential for corrosion to occur.

To measure the microstructure of 30CrNiMo steel, the most commonly used technique is the optical metallography. This is done using a microtome to prepare metal samples for further examination under an optical microscope. The microscope is equipped with polarizers that allow technicians to obtain highly detailed images of the materials microstructure.

To study the relationships between the microstructures and heat treatment cycle, the X-ray diffraction technique is often used. This method reveals the presence of different phases of the material, such as ferrite,bainite and martensite. These phases are identified by their crystallographic orientation and the X-ray reflections they produce.

High-resolution transmission electron microscopy (TEM) is another technique that can be used to study the microstructure of 30CrNiMo steel. This technique is used to obtain ultra-fine detail of the materials microstructure. It can also be used to detect defects in the steel, such as inclusions, segregated grains and grain boundaries.

The 30CrNiMo steel is widely used in industrial applications due to its combination of strength, toughness and weldability. Its microstructure can be studied using optical metallography, X-ray diffraction, or high-resolution transmission electron microscopy. This steel is highly resistant to wear and corrosion, making it a good choice for a variety of applications.

The metallographic structure of ZG30CrNiMo (cast state) is studied by metallographic microscope. The metallographic sample was taken from the middle of the cross section of the sample, electrolytically polished and electrolytically etched.

The microstructure of the ZG30CrNiMo sample consists of ferrite and pearlite, which are distributed in two regions, with ferrite in the center and pearlite around the ferrite. The pearlite structure is mainly banded pearlite structure and lamellar hyperfine structure is also visible. There is no obvious segregation or “rolling” phenomenon.

The ferrite grain size is fine and uniform, the grain size evenly distributed, the grain structure is clear, no oxidation and decarburization, the ferrite grain surface is flat and smooth, no grain boundary disintegration phenomenon.

The pearlite structure is uniform and dense, and the pearlite and ferrite are distributed in a layered arrangement, and the lamellar hyperfine structure is clear. The boundary between ferrite and pearlite is clear, the boundary line is smooth, and the microstructure overall has good stability.

In summary, the metallographic structure of ZG30CrNiMo (cast state) is composed of ferrite and pearlite. The ferrite grain size is fine and uniform, the surface is flat and smooth and there is no grain boundary disintegration; the pearlite structure is uniform and dense, there is no segregation or “rolling” phenomenon, and the microstructure overall has good stability.