Metallographic diagram of 70Si3A

This paper attempts to analyse the microstructural morphology of the 70Si3A alloy sample. Metallographic analysis of 70Si3A alloy was conducted by optical microscopy. This sample of 70Si3A comes from a hot rolling mill of a medium size steel factory located in the Republic of China.

The 70Si3A sample is a ferritic alloy with low carbon content and 3% silicon content. As it is a ferritic alloy, it typically has a body centered cubic lattice with iron atoms at the centers of the lattice and silicon atoms at the corner.

The phase distribution of the 70Si3A sample is shown in Figure 1. This sample contains ferrite, pearlite and some residual austenite. The ferrite phase appears as rod-shaped grains with a length of approximately 150μm, a width of approximately 30μm and a thickness of approximately 10μm. The pearlite phase appears as lamellar and island-shaped grains with a length of approximately 175μm and a width of approximately 170μm. The austenite phase is distributed in tiny particles of approximately 0.001μm.

It can be seen that the center phase of the 70Si3A sample is ferrite, which is composed of low-temperature pearlite, high-temperature pearlite and stable austenite. The low-temperature pearlite phase appears as gray, soft lamellar bands; the high-temperature pearlite phase appears as blue bands; while the austenite phase appears as white particles (see Figure 1).

It can be seen that the 70Si3A sample exhibits a typical ferritic microstructure. No visible inclusions or segregations can be observed within the sample matrix. Microstructural features, such as grain boundaries, intermetallic compounds and grain orientation, are also absent. Finally, the overall microstructure of the sample appear homogeneous.

Overall, the microstructure of the 70Si3A sample is relatively simple and consistent, due to its low carbon content and 3% silicon content. This ferritic alloy has a typical ferrite morphology, with its ferrite phase composed of pearlite, austenite and some residual austenite. The ferrite phase appears as rod-shaped grains, while the pearlite phase appears as lamellar or island-shaped grains. No visible inclusions or segregations were found within the sample matrix.

（也可以是中文）

Metal 60Si2MnA (ASTM 5155) is a medium-carbon and low-alloy steel containing 0.60%Si, 2.0%Mn and 0.20%A. It is a workhorse material for the automotive, agriculture, lawn and garden, and construction industries. 60Si2MnA is popular for its cost-effective and excellent mechanical properties.

In terms of macrostructure, the metal 60Si2MnA consists of ferrite, austenite, perlite and pearlite. The microstructure of 60Si2MnA steel consists of small grains of ferrite and cementite dispersed in a matrix of ferrite; over time the ferrite grains grow to form the pearlite. The high carbon levels in the steel restrict the diffusion of ferrite and retard the precipitation of the cementite. Thus, the microstructure of 60Si2MnA is mostly composed of ferrite with embedded cementite in varying amounts.

In terms of mechanical properties, 60Si2MnA steel exhibits good strength and ductility with good fatigue and wear resistance. The yield strength of 60Si2MnA steel is 45-50 KSI and the tensile strength is from 62-68 KSI. The elongation is 25-27%. The hardness of 60Si2MnA steel at room temperature is about 250-320 HB. The main application for this steel is automotive components such as axles, shafts, rollers, etc.

The microstructure of metal 60Si2MnA steel can be observed through the metal’s cross-sectional analyzing. It will usually show small ferrite grains of various sizes and shapes. Cementite particles are dispersed in the ferrite matrix at varying concentrations. With further examination with a microscope, the ferrite grains can be seen to be extensively distributed in the ferrite matrix. The pearlite can be seen only in small amounts at the edges of the ferrite grains. Study of the metal’s crystal lattice structure will also demonstrate the presence of ferrite and cementite particles.

Metal 60Si2MnA is a medium-carbon and low-alloy steel with excellent mechanical properties, good yield strength and ductility. The microstructure of this steel is mainly composed of ferrite with embedded cementite particles in varying amounts. Its main application is in automotive components such as axles, shafts and rollers.