Analyzing Optimum Process Parameters in Laser Cutting of EN10025-2 Steel Plate

Abstract

Keywords: Laser Cutting; Surface Roughness; Radius Error; Steel Plate; Optimum Parameters

1. Introduction

Laser cutting operations have been used in many industrial areas and many research works have been performed in literature. Belic [1] investigated the laser power in CO2 laser cutting operation and established an equation based on material thickness, cutting speed and cut width. Yilbas [2] examined the effects of cutting parameters on kerf size variations in CO2 laser cutting of thick sheet metals. According to the researcher’s work, gas pressure and laser power intensity was found as significant factors on the percentage of kerf width variation. As increasing the gas pressure and the laser power resulted an increment in thermal erosion around the cut section. Eltawahni [3] studied the optimization of process parameters in high power CO2 laser cutting of advanced materials. The most significant factor affecting the operating cost was found as cutting speed followed by assist gas pressure and laser power. Furthermore, the influence of all parameters was established at their different levels for all thicknesses and materials. The upper kerf width was inversely proportional to the cutting speed and the focal point position and directly proportional to the other factors. In general, the lower kerf was characterized similarly, however, in this case, the lower kerf width was directly proportional to the focal position. The surface roughness increased with increasing the cutting speed and decreased as increasing the other process parameters. The heat affected zone decreased as the gas pressure and the cutting speed increased and increased as the laser power and the focal position increased. In addition it was found that the nozzle diameter had no significant effect on the surface roughness. Hashemzadeh [4] presented a study about key characteristics of fiber laser cutting and found that the surface roughness for the oxygen laser cut edge was less than that for the nitrogen cut edge. During oxygen laser cutting, the striation patterns were much smoother than those observed in the nitrogen laser cutting. Ürgüplü and Köksal [5] studied the effects of laser cutting process parameters on the quality of metallic components. Based on the study, it was found that each process parameter was needed to be arranged according to the purpose of manufacturing importance as surface roughness, cut edge quality, processing time. Chen et al. [6] investigated the relationship between temperature at cut front

edge and kerf quality in fiber laser cutting of Al-Cu alloy. The experimental results showed that there was a close relationship between kerf quality and the temperature at cut front edge. An optimal range of the temperature at cut front edge for accepted kerf quality was found approximately 1800~1950°C. Yilbas et al. [7] presented an investigation on kerf width size analysis and life cycle assessment of cutting process during laser cutting of various materials. According to the results, an increment in laser output power or a reduction in laser cutting speed caused an increment the percentage of kerf width size. Kotadiya et al. [8] performed a parametric analysis of process parameters during laser cutting process on AISI 304 stainless steel. Based on the results of analyzes, laser power was found as the most significant parameter. Joshi et al. [9] studied optimized the process parameters during laser cutting of Ni-based superalloy thin sheet by using response surface methodology. The researchers found that both linear and regression analyses were significant to develop the models. Sharma and Yadava [10] performed an experimental analysis on Nd-YAG laser cutting of sheet materials. Based on the experimental results, it was found that the important input process parameters were laser parameters (laser power, wavelength, mode of operation), sheet material (type, thickness) and process parameters (duration or pulse width, pulse frequency, cutting speed, current, travel direction, assist gas type and pressure, focal plane position, pulse energy,). Sharifi and Akbari [11] presented the effects of process parameters on cutting region temperature and cut edge quality in laser cutting of Al6061-T6 alloy. According to the results, there was a clear dependency between laser power and simultaneous selection of optimum cutting speed to achieve the desired results. It was suggested to select maximum cutting speed while considering the laser power limitation to reach the desired temperature to perform cutting. Oh et al. [12] investigated the cut quality in fiber laser cutting of carbon fiber reinforced polymer (CFRP). During laser irradiation, the pressure inside the kerf increased substantially and formed a fused-cut surface. Thus, the carbon fiber at the kerf edge could undergo a phase change to liquid. Moreover, as the number of passes increased, carbon fibers became fused together, and this phenomena of fusing prevented carbon fibers from delamination and pull-out. In this experimental study, laser cutting experiments were carried out on EN10025-2 (S235JR) cold rolled scoured steel plate. The experiments were designed based on Taguchi method and the effects of process parameters on the surface roughness and the radius error were analyzed. Thus, it was aimed to obtain optimum cutting parameter combinations for this material, which is widely used in laser cutting applications.

2. Experimental Procedure

In the laser cutting operations, EN10025-2 (S235JR) cold rolled scoured steel plate was selected as workpiece material due to widely used in the construction of buildings and bridges, vehicle structures, and shipbuilding. Its chemical composition and mechanical properties are seen in Table 1 and Table 2, respectively. Table 1. The chemical composition of EN10025-2 (S235JR) cold rolled scoured steel plate C Si Mn P S Ni Cr Mo V Cu Al (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%)

3. Results and Discussions

Based on Taguchi’s analysis, the response table of the S/N ratios are given in Table 5 for both surface roughness and radius error. According to the analysis results, the optimum process parameters for surface roughness were determined as feed rate of 5000 mm/min, laser power of 3000 W, frequency of 4000 Hz and focus of -0.8. And the optimum process parameters for radius error were determined as feed rate of 5000 mm/min, laser power of 4000 W, frequency of 4000 Hz and focus of -0.8. These results are also seen in Figure 3 and Figure 4. Based on the results, the optimum results were obtained at the highest laser power due to the fact that thermal efficiency decreased with increasing reducing laser power [2]. Thus the minimum surface roughness and radius error were obtained. The highest delta values in Table 5 refer to the most effective process parameters on the surface roughness and radius errors. The most effective parameters were determined as feed rate and laser power for surface roughness and radius error, respectively. Additionally, the least effective parameters were found as frequency and focus for surface roughness and radius error, respectively.

Table 5. Response table for S/N ratios Feed rate Laser power Level (mm/min) (W) 1 -8.960 -9.905 2 -7.855 -8.192 3 -9.779 -8.497 1.924 1.713 Delta 1 -4.6596 9.2965 2 10.6850 -8.3772 3 4.9777 10.0839 15.3447 18.4611 Delta

Frequency (Hz) -8.982 -8.637 -8.975 0.345 4.8365 8.8150 -2.6483 11.4633

Focus -9.122 -8.438 -9.034 0.684 3.0442 7.3360 0.6230 6.7130

Figure 4. S/N graphs for radius error The determined optimum process parameters are not included in the design of experiment. Therefore, confirmation experiments were performed for both outputs. The optimum process parameters for the surface roughness caused to 2.031 which corresponded to the minimum value. In addition, the optimum process parameters for the radius error caused to 0.08% with the edge radius of 2.502 mm as seen in Figure 5 which also corresponded to the minimum value.

Figure 5. The results of confirmation experiment for edge radius error

4. Conclusion

In this study, the effects of process parameters on the surface roughness and the edge radius errors were investigated and optimum process parameters were determined during laser cutting of EN100252 (S235JR) cold rolled scoured steel plate. Feed rate, laser power, frequency and focus were selected as process parameters with 3 (three) different values. In the experimental design, Taguchi method was used. Based on the analysis results, the most and the least effective parameters on the surface roughness were found as feed rate and frequency, respectively whereas those were laser power and focus, respectively, for radius error. The optimum parameter combination was found as feed rate of 5000 mm/min, laser power of 3000 W, frequency of 4000 Hz and focus of -0.8 for the surface roughness. And the optimum parameter combination was determined as feed rate of 5000 mm/min, laser power of 4000 W, frequency of 4000 Hz and focus of -0.8 for the edge radius error. These results were confirmed by performing confirmation experiments.

Belic, I. (1989) A method to determine the parameters of laser cutting, Optics and Laser Technology 21(4), 277-278. Yilbas, B.S. (2008) Laser cutting of thick sheet metals: Effects of cutting parameters on kerf size variations, Journal of Materials Processing Technology 201(1-3), 285-290. Eltawahni, A. (2011) Optimization of process parameters of high-power CO2 laser cutting for advanced materials, Dublin City University, PhD thesis, Dublin City University, Ireland. Hashemzadeh M. (2014) Investigations into fibre laser cutting, PhD thesis, University of Nottingham, England. Ürgüplü, M., Köksal, S. (2015) The effect of laser cutting process parameters on the quality of metallic components, 3rd International Symposium on Innovative Technologies in Engineering and Science, pp. 866-876, 3-5 June 2015, Valencia, Spain. Chen, C., Gao, M., Zeng, X. (2016) Relationship between temperature at cut front edge and kerf quality in fiber laser cutting of Al-Cu aluminum alloy, International Journal of Machine Tools and Manufacture, 109, 58-64. Yilbas, B.S., Shaukat, M.M., Ashraf, F. (2017) Laser cutting of various materials: Kerf width size analysis and life cycle assessment of cutting process, Optics and Laser Technology 93, 67-73. Kotadiya, D.J., Kapopara, J.M., Patel, A.J., Dalwadi, C.G., Pandya, D.H. (2018) Parametric analysis of process parameter for laser cutting process on SS-304, Materials Today: Proceedings 5(2), 5384-5390. Joshi, P., Sharma, A., Modi, K. (2018) Optimization of process parameters during laser cutting of Nibased superalloy thin sheet using response surface methodology, Materials Today: Proceedings 5 (11), 24231–24239. Sharma, A., Yadavai V. (2018) Experimental analysis of Nd-YAG laser cutting of sheet materials - A review, Optics and Laser Technology 98, 264-280. Sharifi, M., Akbari, M. (2019) Experimental investigation of the effect of process parameters on cutting region temperature and cutting edge quality in laser cutting of AL6061T6 alloy, Optik 184, 457-463. Oh, S., Lee, I., Park, Y.B., Ki, H. (2019) Investigation of cut quality in fiber laser cutting of CFRP, Optics and Laser Technology, 113, 129-140.

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