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AbstractDuring machinability, the combination of machining process parameters and the material properties of the component to be machined plays an important role. Material properties depend upon the type of phase form present and the grain size of the formed phases, which in turn depends upon the prior treatment given to alter the initial room temperature types and form. Accordingly, spheroidization treatment was carried out on medium carbon steel (AISI1040) by altering the initial room temperature structure through normalizing and hardening treatment. Machinability experiments were performed on CNC machine by varying machining process constraints. Tool wear and surface roughness of the machined component obtained by turning were analyzed and correlated. Using Minitab and full factorial design, the ANOVA study was carried out. With the help of regression analysis, residual and main effect plots combined optimization (tool wear and surface roughness) was targeted. ANOVA result shows excellent machinability for the as-bought-spheroidized condition where feed has a 67% contribution to tool wear (TW) whereas the depth of cut has a 71.91% contribution to surface roughness (SR). Also, the optimized regression values obtained for machining parameters are feed (0.39 mm/rev), depth of cut (0.6 mm), and spindle speed (780 rpm) with composite desirability of 0.8174. TW and SR experimental values for the optimized machining parameters are 0.039 mm and 2.89 μm, respectively, and the difference between the actual and optimized values is less than 5%.

In this study, we performed milling machining on carbon-epoxy polymer composites and jute-epoxy composites using a CNC vertical machining center. We focused on spindle speed, feed rate, depth of cut, and flute number and analyzed the cutting force and surface roughness. The optimal parameter combination to reduce cutting force in both composites was as follows: S = 600 rpm, FR = 100 mm/min, DOC = 0.25 mm, and FN = 6. The jute-epoxy composites required less cutting force (11.85 N/m2) compared to the carbon-epoxy composites (18.77 N/m2). The average surface roughness of the carbon-epoxy composites (6.685 µm) is higher than that of the jute-epoxy composites (3.08 µm). The type of reinforced material used greatly affects the cutting force and surface roughness during milling. [ABSTRACT FROM AUTHOR]

AISI4340 steel is the medium carbon low-alloy steel has got excellent prominence as a construction material. This steel is spheroidised on heating to the intercritical temperature range by different time intervals with the objective of increasing the number and fineness of the spheroids of cementite particles. A 9 hours, spheroidisation shows better spheroids of cementite particles. To study the effect of initial room temperature structure on spheroidisation primary heat treatments like normalising and hardening are carried out for as-bought steel. Tensile property (yield strength, ultimate tensile strength and percentage elongation), hardness (Rockwell C scale) and micro-structural features and micro-hardness of micro-phases (ferrite and cementite) are studied. A continuous reduction in the tensile strength, hardness and improvement in ductility, is observed with the increase in spheroidisation time is observed in all the spheroidisation paths. Also, increased spheroidisation time shows a lesser aspect ratio for spheroids. The micro-structure shows partial spheroidisation in all the conditions with more number of spheroids in normalised condition and finer size in hardened. Drastic reduction in strength and hardness values are observed in the hardened condition during spheroidisation.

The importance of medium carbon steels as engineering materials is reflected by the fact that out of the vast majority of engineering grade ferrous alloys available and used in the market today, a large proportion of them are from the family of medium carbon steels. Typically medium carbon steels have a carbon range of 0.25 to 0.65% by weight, and a manganese content ranging from 0.060 to 1.65% by weight. Medium carbon steels are more resistive to cutting, welding and forming as compared to low carbon steels. From the last two decades a number of research scholars reported the use of verity of heat treatments to tailor the properties of medium carbon steels. Spheroidizing is the novel industrial heat treatment employed to improve formability and machinability of medium/high carbon low alloy steels. This exclusive study covers procedure, the effects and possible outcomes of various heat treatments on medium carbon steels. In the present work, other related heat treatments like annealing and special treatments for property alterations which serve as pretreatments for spheroidizing are also reviewed. Medium carbon steels with property alterations by various heat treatment processes are finding increased responsiveness in transportation, aerospace, space, underwater along with other variegated fields. Improved tribological and mechanical properties consisting of impact resistance, stiffness, abrasion and strength are the main reasons for the increased attention of these steels in various industries. In the present scenario for the consolidation of important aspects of various heat treatments and effects on mechanical properties of medium carbons steel, a review of different research papers has been attempted. This review may be used as a guide to provide practical data for heat treatment industry, especially as a tool to enhance workability and tool life.