# Research on Roughness and Microhardness of C45 Material Using High-Speed Machining
## 2 Materials and Methods
The cutting parameters were designed in conjunction with the choice of cutting tool (Figure 3). Since the experiment was oriented to connect the experimental area with practice, an available standard tool--a monolithic face-cylindrical cutter with a diameter of 16 mm--was designed, the substrate of which is nano grain carbide and the coating is multi-layered \"X-5070 blue coated\". \begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**Experiment Alternatives—Cutting Speed [m/min]**} \\ \cline{2-9}  & **700** & **1400** & **2000** \\ \hline Spindle Speed \(n\) [min\({}^{-1}\)] & 13,934 & 27,866 & 39,808 \\ Feed Speed \(v_{f}\) [mm/min] & 5573.6 & 11,146.4 & 15,923.2 \\ Radial depth of cut \(a_{e}\) [mm] & 4 & 4 & 4 \\ Actual chip thickness \(h\) [mm] & & 0.1 & & \\ Medium chip thickness \(h_{m}\) [mm] & & & 0.047 & & \\ Maximum angle of the cutter tooth mesh [\({}^{\circ}\)] & & & 60 & & \\ \hline \multicolumn{9}{c}{**Specification of parameter \"\(a_{p}\)\"**} \\ \hline  & \multicolumn{6}{c}{**Experiment alternatives—cutting speed [m/min]**} \\ \hline  & **700** & \multicolumn{6}{c}{**1400**} & **2000** \\ \hline Axial depth of cut \(a_{p}\) [mm] & 0.5 & 1 & 1.5 & 0.5 & 1 & 1.5 & 0.5 & 1 & 1.5 \\ Section \(S\) [mm\({}^{2}\)] & 0.05 & 0.1 & 0.15 & 0.05 & 0.1 & 0.15 & 0.05 & 0.1 & 0.15 \\ Chip width \(b\) [mm] & 0.5 & 1 & 1.5 & 0.5 & 1 & 1.5 & 0.5 & 1 & 1.5 \\ Maximal section \(S_{\max}\) [mm\({}^{2}\)] & 0.05 & 0.1 & 0.15 & 0.05 & 0.1 & 0.15 & 0.05 & 0.1 & 0.15 \\ Average section \(S_{m}\) [mm\({}^{2}\)] & 0.023 & 0.047 & 0.070 & 0.023 & 0.047 & 0.070 & 0.023 & 0.047 & 0.070 \\ \hline \multicolumn{9}{c}{**Specification of used material—C45**} \\ \hline Tensile strength \(Rm\) [MPa] & & & & & & & 570 & \\ Yield strength [MPa] & & & & & & 325 & \\ Density [kg.m\({}^{-3}\)] & & & & & & 7870 & \\ Thermal coefficient of expansion [K\({}^{-1}\)] & & & & & \(11.6\times 10^{-6}\) & \\ Thermal conductivity [W.m\({}^{-1}\).K\({}^{-1}\)] & & & & & 49 & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Input parameters of the experiment. \begin{table}
\begin{tabular}{c c} \hline \hline Work area x-y-z [mm] & \(1110\times 800\times 600\) \\ \hline Swivel axes (A/B) & –10/+110 \\ \hline Rotary axis (C) & 360 \\ \hline Maximum spindle speed [rpm] & 40,000 \\ \hline Maximum feed rate [mm/min] & 90,000 \\ \hline Maximum tool length [mm] & 300 \\ \hline Maximum tool diameter [mm] & 140 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Selected technical data of DMG HSC 104 Linear [44]. The preparatory phase of the performed experiment was completed by modifying the semi-finished product from C45 material to the required shape and size. The C45 material that was used for the samples was not produced by drawing but by rolling. For drawn materials, it is known that the hardness ranges in the order of \(\pm\)10. However, these materials are characterized by high internal stresses. Rolled material was used for the samples, and one part of the research pointed out the fact that the hardness in the material that was not previously heat-treated in the wide areas of the sample was different. If such material is processed in its original state, the different hardness can be one of the reasons for the rapid wear of the cutting tool, as it is very complicated to optimize the cutting parameters. The modification of the semi-finished product was performed on a band saw for the cutting operation and subsequently roughed on a CNC milling machine in the dimensions 100 \(\times\) 100 \(\times\) 20 [mm] (Figure 4). The prepared test specimens were processed according to the specified cutting conditions listed in Table 1 using high-speed machining technology (Figure 5). Figure 3: Experiment tool—specification (**up**) and geometry (**down**). Analyzes of the influence of cutting parameters on the formation of deformations in the cutting zone were performed on the machined test specimens.