In engineering metallurgy, heat treatment of steels is one of the most important factors as it enhances various physical and mechanical properties which are considered handy in numerous structural applications. Heat treatment is basically the combination of operations involving the heating and cooling of a metal or alloy in solid state for obtaining required microstructures by refining the grain size and a combination of properties. The prime object of this investigation is to illustrate the effect of heat treatment on low carbon steel (AISI 1020) to expose its mechanical (hardness) and microstructural (microstructures) properties. For this purpose, cylindrical shaped AISI 1020 steel specimens were used. The samples were polished using a specimen polishing machine and heated in a heat treatment furnace at approximately 950°C for almost 2 hours and then cooled by different quenching media (Water, Air, Ash). After heat treatment (Hardening, Normalizing, Full Annealing) the Brinell hardness number (B.H.N) was determined using a Universal testing machine (U.T.M) and the microstructures were examined using a metallurgical microscope. It was observed that, due to hardening the resultant structure was a super saturated solid solution of carbon trapped in a body centered tetragonal structure called martencite which increased the hardness number of the steel specimens drastically making an extreme harder steel. Moreover, full annealing provided lower hardness value due to the presence of ferrite structure and normalizing provided moderate hardness value and ductility due to slow cooling.

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This is a study of the suitability of preheat flame electrical resistance as a potential method for measuring the standoff distance an oxyfuel cutting torch and a work piece. Careful scrutiny of forty seven (47) individual experiments demonstrate that when cut quality is good, there is a linear repeatable relationship between the two with uncertainty about ± .3mm (.015in). As the cut quality degrades, the formation of top-edge dross reduces the electrical path length in the flame, and momentary reduction in the reaction rate in the kerf reduces the free electrons in the flame, causing rises in flame resistance. In these conditions, measurement uncertainty reduces to ± 1mm (.040in) or worse.

A three-dimensional (3D) computational model is presented in this paper that illustrates the detailed electrical characteristics, and the current-voltage (i-v) relationship throughout the preheating process of premixed methane-oxygen oxyfuel cutting flame subject to electric bias voltages. As such, the equations describing combustion, electrochemical transport for charged species, and potential are solved through a commercially available finite-volume Computational Fluid Dynamics (CFD) code. The reactions of the methane-oxygen (CH4 – O2) flame were combined with a reduced mechanism, and additional ionization reactions that generate three chemi-ions, H3O+, HCO+, and e−, to describe the chemistry of ions in flames. The electrical characteristics such as ion migrations and ion distributions are investigated for a range of electric potential, V ∈ [−5V, +5V]. Since the physical flame is comprised of twelve Bunsen-like conical flame, inclusion of the third dimension imparts the resolution of fluid mechanics and the interaction among the individual cones. It was concluded that charged ‘sheaths’ are formed at both torch and workpiece surfaces, subsequently forming three distinct regimes in the i-v relationship. The i-v characteristics obtained out of the current study have been compared to the previous experimental and two-dimensional (2D) computational model for premixed flame. In this way, the overall model generates a better understanding of the physical behavior of the oxyfuel cutting flames, along with a more validated i-v characteristics. Such understanding might provide critical information towards achieving an autonomous oxyfuel cutting process.