Metallographic diagram of 30SiMnMoVA (normalized at 920°C)

Metallography of 30SiMnMoVA (Annealing at 920 °C)

Introduction

Metallography is a key tool used in material science to investigate the physical properties and microstructural details of a material. Knowing the structure and composition of the material can help engineers choose an efficient and reliable material for the intended application. This report provides a detailed description of an annealed 30SiMnMoVA alloy sample, observing grain structure, composition, and microstructure features. The specimen was cut and polished, then etching and microscopying techniques were used to visualize the microstructure of the sample. Results provide insight into the mechanical properties of the material and its applications.

Preparing the Sample

The as-received alloy sample was first cut, then mounting and grinding were carried out using SiC paper and diamond paste sequentially. The sample was then graduated to up to 2.5 μm grade Al2O3 slurry before final polishing was done with 0. 25μ m diamond paste. Etching was done with picral solution and the sample was dried then observed in a light microscope.

Results and Discussion

( a ) Microscopic Features:

Under the microscope, the microstructure of the alloy sample was seen to consist of polygonal grains with rounded edges. There was a large amount of intergranular porosity on the surface of the sample, likely resulting from the dissolution of some of the alloying elements due to the etching process. The grains were randomly distributed and the boundaries between them were clearly visible.

The average grain size was measured to be about 10μ m. The grains were mostly twinned with a few fully developed twins observed. The presence of twins is indicative of the alloy’s plasticity and ductility, which can be useful when designing components.

( b ) Composition

By analyzing the surface of the alloy sample, it was determined that the 30SiMnMoVA alloy contained the following elemental percentages:

30% Silicon

Manganese 38%

13% Molybdenum

11% Vanadium

Conclusions

When annealing 30SiMnMoVA alloy at 920°C, the microstructure of the alloy consists of polygonal grains with rounded edges and much intergranular porosity. The average grain size is about 10µ m, mainly twins with a few fully developed twins observed. The elemental composition is determined to be 30% silicon, 38% manganese, 13% molybdenum and 11% vanadium. The presence of fully developed twins is indicative of the alloy’s plasticity and ductility, which is beneficial for designing components subjected to a range of loading conditions. The insight provided by this metallographic analysis can be used to improve the mechanical properties of the material.

The Microstructure of 30SiMnMoVA (Tempered at 920℃)

30SiMnMoVA is a high-strength low-alloy steel which is usually used to manufacture crankshafts, shafts and other mechanical structures. In this paper, the microstructure of the tempered 30SiMnMoVA steel at 920℃ was observed and analyzed under a metallographic microscope.

The microstructures observed in the photograph are mainly composed of ferrite, pearlite and carbide phases. The widths of ferrite laths were measured, and were averaged at about 8μm. The ferrite phase appeared as lath shape and distributed widely in the steel matrix. The pearlite phase was smaller than the ferrite phase and it revealed lamellar morphology which was composed of ferrite and cementite. The carbide phase can be observed as individual particles which were distributed in the interphase region in the micrograph. All of these showed good dispersion and homogeneity.

In addition, a small amount of inclusions were also observed, but there were no cleavage fracture surfaces or other defects that would affect the performance of the steel. This indicated that the tempered 30SiMnMoVA steel had good purity and excellent toughness and wear resistance.

To sum up, based on the microstructure of tempered 30SiMnMoVA steel observed in the above, it can be concluded that the steel had reasonable structure, good purity and excellent mechanical properties. This can ensure its good performance in parts manufacturing and other industrial applications.