Experimental investigation on boring of HSLA ASTM A36 steel under dry, wet, and cryogenic environments

Abstract

ABSTRACTAn endeavor has been made to bailiwick cryogenic, wet, and dry boring of HSLA ASTM A36 steel, which is predominantly used in armor material and oil and gas pipelines. To ensure a direct coolant supply (controlled flow rate) at the cutting zone and palpable ciphering of cutting temperature, a transmogrified boring bar is exercised. Electrical discharge machining (EDM) was availed to create for the accommodation of a thermocouple slot, in an axial hole boring bar. Reduction of 16.1–59.8% and 4.3–16.7% in cutting force, 53.38–78.36% and 25.31–64.89% in cutting temperature, and 27.76–70.23% and 4.22–28.30% in surface roughness is ascertained in cryogenic milieu boring in correlation to dry and wet milieu boring, respectively. It is discerned for cutting force, speed of 88.59 m/min and 0.055 mm/min is the ideal cutting parameter for cryogenic, wet and dry boring conditions. For cutting temperature, ideal cutting parameter is speed of 88.59 m/min and 0.048 mm/min for dry and wet, respectively, and speed of 88.59 m/min and 0.055 mm/min for cryogenic boring. Additionally, speed of 88.59 m/min and 0.055 mm/min is the ideal cutting parameter for surface roughness in all three different cutting environments. From ANOVA, it is determined that speed plays a vital role in all three conditions of boring. For dry and wet boring, speed personates a notable semblance in ascertaining the cutting temperature, but in the case of cryogenic boring, feed plays an imperative part. Additionally, for surface roughness, feed is the most prominent parameter in cryogenic, wet, and dry boring. Furthermore, cryogenic machining surges the hardness of ferrite culminating in curtailed chip lengths and deficient built-up edge evolution on the cutting tool. An abatement in flank wear by 36.58% and 53.65% is ascertained in the cryogenic boring of ASTM A36 HSLA steel correlated to wet and dry boring, respectively. Boring under cryogenic condition, the crater wear reduces by 88.30% and 90.10% with respect to wet and dry boring, respectively. Scanning electron microscopy observations of bored surfaces in wet and dry boring show a network of microcracks which is absent in cryogenic boring of ASTM A36 HSLA steel. Compressive residual stress has increased by 9.5% and 31.83% in boring under cryogenic medium with respect to wet and dry boring of ASTM A36 HSLA steel. There is an overall increase in hardness value in bored surface in cryogenic medium over wet and dry bored surface by 22.26%–30.06% and 21.06–39.43%, respectively. The corrosion resistance in cryogenic boring increases by 65.26% and 29.33% with respect to wet and dry boring of ASTM A36 HSLA steel, respectively. High repercussions of geometrical features are ascertained in abatement of circularity and cylindricity of hole profile bestowing cryogenic medium of boring.