Abstract
The aim of this research is to study the machinability aspects of hardened AISI 4340 High Strength Low Alloy (HSLA) steel (50 ± 2 HRC (Hardness Rockwell C)). The experimental investigation using coated carbide inserts is carried out during the dry hard milling process in a sustainable environment. The input parameters in the study are speed, feed rate and depth of cut and the responses are Average surface Roughness (Ra) and Material Removal Rate (MRR) that are selected through screening. Central Composite Design (CCD) in response surface methodology has been utilized as the experimental design technique with twenty experiments. Analysis of variance has been employed to examine the momentous machining parameters and responses. A mathematical model has been developed to optimize the surface roughness and material removal rate. It has been observed that the most significant factor for Ra is feed rate while for MRR depth of cut is the most significant factor. The results show that the minimum value of Ra ~ 0.098 μm is achieved at speed ~ 1000 RPM, feed rate ~ 300 mm/min and depth of cut ~ 0.2 mm while the maximum value of MRR ~ 6.35 cm3/min is attained at feed rate ~ 500mm/min and depth of cut ~ 0.4 mm regarding less or no effect of speed ~ 500-1000 RPM. The average forecast error for the validation information has been observed to be 3.35%. for Ra and 3.2% for MRR. Further, it is investigated that good surface finish like grinding and dimensional accuracy can be achieved with coated carbide tools.
Highlights
AISI 4340 is a medium carbon low alloy steel in which the combined proportion of all the alloying elements by weight is less than 5 % (HSLA)
Design of Experiment (DOE) matrix has been developed through design expert 7
(i) The outcomes specify that the quadratic model is better for Ra and 2FI model is better for Material Removal Rate (MRR) with maximum prediction accuracy and is confirmed through further experimentations
Summary
AISI 4340 is a medium carbon low alloy steel in which the combined proportion of all the alloying elements by weight is less than 5 % (HSLA). It has the ability to attain high toughness and strength in the heat-treated condition. It is mostly used in the aviation industry and aeronautical applications due to very good corrosion, wear and fatigue resistance [1]. The functional performance such as corrosion resistance, fatigue strength and tribological properties of the machined components is determined by surface characteristics. The quality is determined by the surface finish and integrity attained after machining. Researchers have studied the influence of these control variables on the surface finish, material removal rate and tool wear [3,4,5,6,7,8,9].
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