Metallographic diagram of 45 steel (after quenching and tempering, 680°C gas nitrocarburizing treatment)

Microscopic Examination of Alloy Steel 45 After Gas Nitrogen Carbon Co-Impermeated Treatment of 680℃

Alloy Steel 45 is a low-alloy and high-strength structural steel, mainly used to manufacture various structural parts of various engineering vehicles and engineering machinery. In order to improve the comprehensive mechanical properties and wear resistance of the steel, surfacing or quenching and tempering (annealing) processes are often required before welding. In order to further improve the comprehensive performance of the steel, it is necessary to carry out gas nitrogen-carbon co-impermeation treatment at 680℃. In order to evaluate the improvement of the microstructure of the steel after such treatment, a microscopic examination was conducted.

The microstructure of Alloy Steel 45 before nitrogen-carbon co-impermeation treatment at 680℃ is shown in Figure 1. It can be seen that the matrix of the steel is fine ferrite. The Ferrite grains are relatively small, and the intergranular boundaries are relatively clear, indicating good thermal stability. In addition, the matrix is dispersed with a small amount of carbide particles, which generally take the form of laths and blocks, and are evenly distributed. This shows that Alloy Steel 45 has a good uniformity and good corrosion resistance.

Figure 1: Microstructure of Alloy Steel 45 Before Treatment

After undergoing nitrogendue to nitrogen-carbon co-impermeation treatment at 680℃, the microstructure of Alloy Steel 45 is shown in Figure 2. It can be seen that after nitrogen-carbon co-impermeation treatment, the overall microstructure of Alloy Steel 45 is significantly refined. The Ferrite grains are significantly refined, the intergranular boundaries are relatively clear, and the grain size is uniform and stable. In addition, the distribution of the carbide particles remains almost unchanged after treatment, and there are no obvious changes in the shape and size of the particles.

Figure 2: Microstructure of Alloy Steel 45 After Treatment

In conclusion, through nitrogen-carbon co-impermeation treatment of Alloy Steel 45 at 680℃, the overall microstructure can be significantly refined, which can further improve the comprehensive performance of Alloy Steel 45 and improve the wear resistance of the steel.

GB 45 steel is medium carbon steel for machine structural use. After quenching and tempering, it can be used for producing mechanical parts and tools such as connecting rods, screws, nuts and bolts, valves, valve stems, spindles, disks, pins, couplings and other power transmission components.

The golden phase diagram of GB 45 steel (after tempering and then through 680℃ nitrogen-carbon co-permeation treatment) uses light microscope to observe its metallographic structure. It is found that the matrix is ferrite and the structure lath is not obvious, and the surface of the grain is clean and uniform, indicating that the hardening surface of GB 45 steel is successful. At the same time, in the martensite area of the grain, there is no coarse pearlite structure, which proves that the GB 45 steel after nitrocarburizing treatment has a strong nitrogen diffusion effect, which dissolves the cementite to some extent and improves the fatigue strength of GB 45 steel.

In addition, GB 45 steel can also be used for welding, surface hardening, hot and cold stamping, core or billet rolling and drawing, and other processing of mechanical parts. With its excellent comprehensive performance, it is widely used in the manufacturing of heavy-duty industrial, agricultural and vehicle parts, hydraulic components and other equipment.