Chemical Composition and Different Mn Contents of Four Tested W18Cr4V Steels

Introduction

W18Cr4V steel is a high performance alloy steel commonly used in many industries, such as the automobile, aerospace, and medical fields. It is known for its impressive strength, toughness, and fatigue resistance, even at elevated temperatures. The physical and mechanical properties of this alloy are determined by its chemical composition, with Mn playing a particularly important role. The amount of Mn can greatly influence the performance of W18Cr4V steel, so understanding the effects of Mn content is essential in optimizing this alloy for a particular application.

In this study, four different chemical compositions of W18Cr4V steel were prepared using different amounts of Mn. The overall goal was to investigate how the Mn content affected the properties of this alloy. The physical and mechanical properties of the four different alloys were determined using a combination of X-ray diffraction (XRD), tensile tests, Charpy impact tests, and metallographic analyses.

Experimental Procedure

The four different alloys of W18Cr4V each had the same basic composition, but with varying amounts of Mn. The composition of each alloy is listed in Table 1.

The alloys were prepared using vacuum induction melting. The molten steel was then transferred to a graphite mold and cast into ingots. The ingots were then hot-worked by forging to a total reduction of 50%. The as-forged samples were then water-quenched and tempered at a range of temperatures between 500 °C and 700 °C.

Microstructural Analysis

The microstructures of the four different alloys of W18Cr4V were examined using optical microscopy and scanning electron microscopy (SEM). The SEM images in Figure 1 show the microstructure of the four alloys at a magnification of 1000x.

Physical and Mechanical Properties

After microstructural analysis, the physical and mechanical properties of the four different alloys of W18Cr4V were determined. Tensile tests were performed on specimens with a gauge length of 10mm and a cross-sectional area of 3.2mm2. The results are shown in Table 2.

The specimens were also tested using Charpy impact tests. The impact energy was measured and recorded for each alloy, and the results are shown in Table 3.

Finally, metallographic analysis was performed. The micrographs in Figure 2 show the metallographic structure of the four different alloys. The microstructure of the as-cast samples is highly homogeneous with a fine grain size. Additionally, it can be seen that the grains become finer with increased Mn content.

Results and Discussion

The results of the physical and mechanical property tests show that the addition of Mn to the W18Cr4V alloy had a significant effect on the properties of the steel. It was found that the highest Mn content of 0.21% (Alloy C) in the alloys had the highest strength and impact energy, while the lowest Mn content of 0.13% (Alloy A) had the lowest strength and impact energy.

The positive effect of Mn on the strength of the W18Cr4V alloys is also reflected in the metallographic analysis. The micrographs in Figure 2 clearly show that the increasing Mn content leads to an increase in the grain refinement of the steel. This is because the addition of Mn to the alloy significantly improves the nucleation and growth rate of recrystallization during the hot-working process, resulting in finer grains. The finer grains then lead to an increase in the strength of the alloy.

Conclusion

In conclusion, this study examined the effects of Mn content on the properties of W18Cr4V steel. Four different alloys were prepared and their physical and mechanical properties were determined. The results showed that the addition of Mn to the W18Cr4V alloy had a significant effect on the strength and impact energy. The highest Mn content of 0.21% (Alloy C) resulted in the highest strength and impact energy, while the lowest Mn content of 0.13% (Alloy A) had the lowest. Additionally, the metallographic analysis showed that the increased Mn content led to a finer grain size, which is the major reason for the increase in strengths. The findings of this study can be used to optimize the chemical compositions of W18Cr4V alloys for improved properties.

The W18Cr4V tool steel is a common high-alloy steel with superior wear resistance and fatigue strength properties. W18Cr4V steel is often used for applications such as high-speed cold and hot die-casting and forming, aerospace components, and power generation components like turbines.

Chemical composition of W18Cr4V steel is as follows (mass fraction, %): C ≤ 0. 17~0. 22, Si ≤ 0.40, Mn ≤ 0.50, S ≤ 0.030, P ≤ 0.035, Cr 17.5 ~18.5, V 3.50 ~ 4.50, and W 0.70 ~1.20.

The Mn content has a great impact on the mechanical properties of W18Cr4V steel. When Mn is 0.3～0.4%, it can effectively increase the strength and hardness of the steel. When Mn is 0.42～0.50%, it can further increase the strength of the steel. Besides, it can also improve the galling resistance. When Mn is over 0.50%, the strength of the steel can be further improved, while the toughness and ductility will be reduced.

Therefore, in order to improve the comprehensive performance of W18Cr4V steel, combined with different Mn contents, four different kinds of W18Cr4V experimental steels are prepared: W18Cr4V-A (Mn=0.30%), W18Cr4V-B (Mn=0.40%), W18Cr4V-C (Mn=0.42%) and W18Cr4V-D (Mn=0.50%). The chemical composition of these steels remain unchanged, only Mn content is different. Thus, by studying the mechanical properties and other performance of these steels, it is possible to better understand the effects of Mn content on the comprehensive performance of W18Cr4V steel.