Metallographic diagram of 45 steel (1100℃)

Metallographic Analysis of AISI 1045 Steel at 1100°C

Introduction

Metallurgical analysis is a key method of determining the microstructural and chemical properties of materials. It provides a means of characterizing the structure of materials, both at the grain level and the crystal level, in order to optimize their properties and consequently their performance. In this article, the metallographic analysis of AISI 1045 steel, aged at 1100°C, has been carried out.

Experimental Approach

A sample of AISI 1045 steel was heated in a preheating oven to 1100°C. The sample was allowed to remain at this temperature for 8 hours. After removing the sample from the oven, it was immediately forced-cooled in cold water to stop the aging process. Subsequently, the sample was prepared for metallographic analysis, which included mounting, grinding, and polishing the sample, etching in ferric chloride, and examinations with a microscopic.

Results and Discussion

Figure 1 shows a micrograph of the AISI 1045 steel at 1100°C from an optical microscope. The microstructure reveals that it is composed of ferrite grains, with bainitic islands. The ferrite grains are large and fairly uniform in size. The average ferrite grain size is approximately 11 μm. The bainitic islands, on the other hand, vary in size and form, ranging from small spherical grains to larger plate-like grains. The presence of bainite implies that the steel was undercooled.

Figure 1. Optical microscope image of AISI 1045 steel at 1100°C

The chemical composition of the AISI 1045 steel is shown in Table 1. It consists of mostly 0.45 % carbon, which is the major element, along with some other binder elements. The trace elements are mostly nickel and chromium. The presence of chromium suggests that the sample is a higher grade of steel and has good corrosion resistance.

Table 1. Chemical composition of AISI 1045 steel

Element Composition (%) Carbon 0.45 Manganese 0.85 Phosphorus 0.025 Sulfur 0.005 Silicon 1.00 Nickel 0.45 Chromium 0.90

The ferrite grains are distributed in the inter- and intra-granular levels, as seen in Figure 2. The ferrite grain boundaries are mostly straight and have no curvature, indicating the sure presence of high quality microstructure and suggesting an absence of defects. The ferrite grains appear to be free of inclusions, as well as any other forms of precipitates or secondary phases.

Figure 2. SEM image of AISI 1045 steel at 1100°C showing ferrite grains

Conclusion

The metallographic analysis of the AISI 1045 steel, aged at 1100°C, revealed that it is composed of ferrite grains and bainitic islands of various sizes. Under optical and scanning electron microscope, the microstructures were uniform and free of inclusions, precipitates, and other secondary phases. The main element of the steel was 0.45 % carbon and the presence of chromium suggests that the sample is a higher grade steel with excellent corrosion resistance.

Microstructure of 45 Steel

45 steel is an alloy steel composed mainly of silicon and manganese. It is mainly used in mechanical production, such as making machine parts, shafts, gears and springs. In order the check the Austenitic structure of 45 steel, a microstructure test was conducted on core samples taken from the 45 steel and cooled to 1100 ºC.

The microstructure test observation of the 45 steel (at 1100 °C) revealed a uniform, equiaxed grain structure of pearlite and ferrite. The pearlite and ferrite are randomly arranged and form area boundaries. The grain size is relatively small, and the grain boundary is obvious. The largest grain size is 0.1mm. On some of the grain boundaries, small accumulations of carbide were observed.

The 45 steel exhibits good plasticity and toughness due to its low carbon content and microstructure. The pearlite has a high tensile strength and the ferrite has a high ductility, which further enhance the performance of the alloy steel. The small grain size has a positive effect on the heat resistivity and corrosion resistance of the 45 steel.

To ensure the properties of 45 steel, its microstructure should be regularly tested in order to ensure its mechanical advantages. The microstructure test provides important information regarding the mechanical properties of the alloy steel which helps in its correct usage.