Sains Malaysiana 46(5)(2017): 755–762

http://dx.doi.org/10.17576/jsm-2017-4605-10

Laser Cutting of Square Blanks in Stainless Steel-304 Sheets: HAZ and Thermal Stress Analysis

(Pemotongan Laser Segi Empat Kosong dalam Lembaran Keluli Kalis Karat-304: HAZ dan Analisis Tegasan Termal)

A.M. SIFULLAH¹, KHALED I. AHMED², Y. NUKMAN¹*, M.A. HASSAN¹ & A. HOSSAIN¹

¹Department of Mechanical Engineering, Faculty of Engineering, University of Malaya

50603 Kuala Lumpur, Federal Territory, Malaysia

²Mechanical Engineering Department, Assiut University, Assiut 71615, Egypt

Diserahkan: 9 Mac 2016/Diterima: 17 Oktober 2016

ABSTRACT

Laser cutting is a non-traditional cutting process and cutting of square blank in stainless steel-304 sheets cause heat affected zone (HAZ) and thermal stress. Formation of HAZ is undesirable and excessive stress cause surface defects. Thus, it is necessary to analyze them intensively. The process of laser cutting is a complex thermo-mechanical process. Hence, in this study a thermo-mechanical finite element model has been introduced by ANSYS to predict the temporal variation together with thermal stress and width of heat affected zone (HAZ). CO₂ laser is used to cut 10 × 10 mm square blank in a 3 mm thick stainless steel-304 sheet. Optical microscope and SEM are used to analyse the parametric effect on surface quality at the cutting edge. The results showed that maximum temperature at the cutting edge is about to melting temperature and independent to laser power and cutting speed. Importantly, cutting speed has significant effect on rate of temperature variation. Moreover, the width of HAZ increases with the increase of laser power and decrease of cutting speed. However results of ANOVA suggested that laser power is the most significant parameter having 64.21% of contribution to width of HAZ. Furthermore, maximum stress is observed at the corner; which is supported by SEM analysis.

Keywords: Finite element analysis; heat affected zone; laser blanking; stainless steel-304; thermal stress

ABSTRAK

Pemotongan laser adalah satu proses pemotongan bukan tradisi dan memotong kepingan keluli kalis karat-304 segi empat kosong boleh menyebabkan terjadinya zon terjejas haba (HAZ) dan tekanan termal. Pembentukan HAZ tidak diingini dan tekanan berlebihan akan menyebabkan kecacatan permukaan. Oleh itu, adalah perlu untuk menganalisis perkara ini secara intensif. Tetapi proses pemotongan laser adalah proses termo-mekanik kompleks. Oleh itu, dalam kajian ini, model unsur terhingga termo-mekanik telah diperkenalkan menggunakan ANSYS untuk meramalkan perubahan variasi sementara bersama dengan tekanan termal dan lebar zon terjejas haba (HAZ). CO₂ laser digunakan untuk memotong 10 × 10 mm kepingan keluli kalis karat-304 segi empat kosong dengan kelebaran 3 mm. Mikroskop optik dan SEM digunakan untuk menganalisis kesan parametrik pada kualiti permukaan di pinggir pemotongan. Keputusan menunjukkan bahawa suhu maksimum di pinggir pemotongan adalah berkadaran dengan suhu takat lebur dan berkadaran dengan kuasa laser dan kelajuan pemotongan. Oleh itu, kelajuan pemotongan mempunyai kesan yang besar ke atas kadar perubahan suhu. Tambahan pula, lebar HAZ meningkat dengan peningkatan kuasa laser dan penurunan kelajuan pemotongan. Walau bagaimanapun, keputusan ANOVA mencadangkan bahawa kuasa laser adalah parameter yang paling penting mempunyai 64.21% daripada sumbangan untuk lebar HAZ. Tambahan pula, tekanan maksimum diperhatikan berlaku di bahagian sudut juga disokong oleh analisis SEM.

Kata kunci: Analisis model terhingga; kalis karat-304; pemblankan laser; tegasan termal; zon terjejas haba

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*Pengarang untuk surat-menyurat; email: nukman@um.edu.my