Metallographic diagram of 65Si2MnWA (after hot rolling)

65Si2MnWA (hot rolled) ferrite-pearlite material is characterized by a chemical and microstructural composition that can be used in many applications that require a high strength combination of material properties and weldability. The chemical composition of the grade is 65% Si, 2% Mn, 0.3% Ni, 0.3% Cr, 0.2% Mo, 0.2% Co, 0.1% V and 0.1% Al, for a total ofother elements less than 0.05%.

The material exhibits a microstructure consisting of a solid solution of ferrite and pearlite, each having an average grain size of about 1.5µm. This grain size is smaller than that typically found in annealed versions of the grade, making it an excellent choice for cold-forming and machining operations. Due to its ferritic-pearlitic microstructure, the material possesses a high tensile strength, yield strength, and stress corrosion cracking resistance. Additionally, the grade has good formability and toughness, making it suitable for applications such as automotive parts and agricultural machinery components.

On-site metallographic examination of 65Si2MnWA (hot rolled) ferrite-pearlite material reveals a grey colour to the specimen, with areas of both ferrite and pearlite visible in the microstructure. The ferrite grains, exhibiting a fine and even distribution, are weakly ferromagnetic and are surrounded by the typical banded microstructure associated with pearlite. The ferrite-pearlite microstructure has been found to be more beneficial than an austenite-pearlite microstructure for applications that require a strong combination of properties, such as weldability, toughness, and formability.

Physical and mechanical property testing of the 65Si2MnWA grade reveals that it is able to meet the required specifications in terms of strength and toughness. The short-term tensile strength of the material is about 640 MPa, with a good yield strength at about 517 MPa. It has also a good elongation at about 13%.The hardness of the material is also in the acceptable range, falling between 180 and 250 Hv5.

Due to its excellent properties and performance, 65Si2MnWA (hot rolled) ferrite-pearlite material has been used in a wide range of applications that require a combination of material properties such as weldability, strength, and formability. Automotive parts, agricultural machinery components, and tools such as wrenches are all examples of parts produced using this material grade. Additionally, the use of this grade has been seen in applications where resistance to stress corrosion cracking is important, such as water tanks.

In conclusion, 65Si2MnWA (hot rolled) ferrite-pearlite material is versatile in its applications due to its excellent combination of strength, toughness, and weldability. The small grain size of the material allows for effective machining and cold forming operations and make the material suitable for many different applications. The mechanical and physical properties of the grade together with its high stress corrosion cracking resistance allow the material to be used in a wide variety of industries and applications.

In order to study the microstructure of 65Si2MnWA steel after hot rolling, an optical microscope was used to observe the sample. The results show that the 65Si2MnWA steel sample after hot rolling is composed of an austenitic matrix containing fibrous ferrite, granular pearlite and lath shaped martensite. The fibrous ferrite laths are distributed in the austenitic matrix, and the number of ferrite laths is more than that of pearlite granules. The austenitic structure is distributed in the network, the grain size is fine, the ferrite lath is thin and long, the martensite lath is irregular, the grain boundary is visible and complete, and the shape is not evenly distributed. At the same time, some of the ferrite and martensite plates are interlarded, exhibiting a two-phase or two-stage structure. In addition, some of the pearlite granules are surrounded by fibrous ferrite. Most of the pearlite granules are small and elliptical, the areas of their interfaces with ferrite laths and austenite matrix grains are large, and their boundaries are irregular.

According to the microstructure of 65Si2MnWA steel sample observed by optical microscope, it can be concluded that the 65Si2MnWA steel sample after hot rolling has fine grain size, and its microstructure is composed of austenitic matrix, fibrous ferrite, granular pearlite, as well as lath shaped martensite. The ferrite, pearlite and martensite laths are interlarded in the network structure. The small-scale structure and phase structure are complex and neat, which is characteristic of the high strength and ductility of 65Si2MnWA steel.