Investigation of the mechanical properties of annealing heat treated low carbon steel

The mechanical properties of steel materials usually vary under different conditions, thus choosing the suitable heat treatment is needed to obtain acceptable properties. In this research work, investigation of the mechanical properties of heat treated low carbon steel was determined using tensile tests, and hardness measurements.  Also, the microstructure of the samples was characterized by means of optical microscopy. The samples of low carbon steels were sourced at local market in Nigeria. The collected samples were machined using lathe machine to a diameter of 10mm and gauge length of 30 mm. The chemical composition of the steel was determined using X-ray fluorescence spectroscopy. The mechanical properties of the heat treated and untreated samples were investigated at the temperatures of 900 ⁰C, 950 ⁰C, and 1000 ⁰C. The results obtained show that the ultimate tensile strength and percentage elongation of samples increases after heat treatment. Also, yield strength and hardness tend to decrease for all annealed heat treated samples at different temperature as compared to as received samples.  The results of the microstructural analyses of the as received samples showed fine dispersion of coalesced pearlite and ferrite grain. For the annealed samples, the steel microstructures compose of martensite distributed in the ferrite matrix. However, with increase in annealing temperature to 1000 ⁰C and 1100 ⁰C cementite and ferrite grain with partial grain boundary were observed