12CrNi2 (1100℃×20min+500℃×1s water cooling) metallographic diagram

Microstructure Analysis of 12CrNi2 Steel after Quenching and Tempering

The microstructure of 12CrNi2 steel after high temperature quenching and tempering treatment, which was subjected to 1150℃×20min+500℃×1s water cooling, was investigated using a metallographic microscope. The results showed that the iron grain size of the sample had been refined significantly after quenching and tempering so that the grain size was visible to the naked eye. There were visible boundaries of each grain, with the borders being rough and uneven, indicating that the grains were distributed relatively uniformly. The boundaries of the grains were irregularly curved and they were composed of ferrite and pearlite structures.

The boundaries between the ferrite and pearlite structures were very clear and neat, indicating that the two were completely independent of each other. The pearlite structure was composed of alternating layers of ferrite and iron-cementite. Each iron-cementite layer had an obvious elliptical distribution, indicating the presence of so-called needle-like cementite particles. The area fraction of ferrite in the sample was about 78.4%, and that of pearlite about 21.6%.

In the ferrite structure, the shape of the single iron grains was irregularly curved, and the distribution and orientation of the grains were relatively uniform. The average size of the ferrite grains was 1.32μm and the space between the fircoalac particles was wide. However, a few nitrides and carbides were found in some places between the ferrite matrix. These compounds tended to be distributed along the grain boundaries or occasionally in the grains, indicating that they had a significant effect on the strength and other mechanical properties of the steel.

In summary, the microstructure of 12CrNi2 steel after high temperature quenching and tempering treatment can be described as a ferrite structure with a significant refinement of the grain size, a neat and clear pearlite structure, and a small amount of carbides and nitrides in some places between the ferrite matrix. These indicate that the quenching and tempering process has had a significant role in improving the mechanical properties of the steel.

Metallographic analysis of 12CrNi2 (1100℃x20min+500℃x1s water-cooling)

The 12CrNi2 alloy is a high-chromium and low-nickel structural alloy steel, which is used in the manufacture of steel structural components and mechanical parts. The 12CrNi2 alloy is a heat treatment process of normalizing, annealing and quenching and tempering, and a metallographic analysis.

The metallographic analysis of the 12CrNi2 alloy is taken as the sample. The sample is cut into a cylindrical shape of 50 mm long, 20 mm in diameter and 2 mm in thickness. Put it in a water-cooled furnace after preheating, heat to 1100℃ and heat insulation for 20 minutes, then add 500℃ water-cooled quenching 1s.

When analyzing the sample with a metallographic microscope, a large number of primary phase particles and tempered sorbite phase particles can be observed in the matrix of the sample. There are obvious equiaxed austenite grains in the grain size, and the grains are fairly coarse, with an average size of about 10 microns. The primary phase particles generally extend along the grain boundary and are mainly composed of δ-Fe3C. There are a large number of carbides distributed in the austenite grain boundary and cross-grain boundary, and most of them are to form a fish eye and lamp oil structure.

The overall microstructure of the 12CrNi2 alloy sample is basically equiaxed cementite and tempered sorbite. The study and understanding of the metallographic structure of this alloy is beneficial to further understand and master its characteristics, so as to obtain the best heat treatment process and enhance the service life and reliability of the alloy parts.