Performance of coated carbide tool in low speed milling of stainless steel under flood and mist lubrication

Siow , Ping Chuan (2009) Performance of coated carbide tool in low speed milling of stainless steel under flood and mist lubrication. Masters thesis, Universiti Malaysia Sabah.

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Abstract

Most of the research works on the milling of stainless steel in the past were carried out at cutting speeds of higher than 100 m/min and had reported that the optimum speeds for milling steel were in the range of 100 m/min to 150 m/min. In some cases, milling at low speeds is inevitable. Some solid end-mill tools used to produce small features such as pockets and slots have a diameter of less than 2 mm. If a tool with diameter of 2 mm is used, milling cannot be performed at speeds higher than 100 m/min if the machine employs a spindle with a maximum rotational speed of less than 16,000 rpm. However, many milling machines use spindles with rotational speeds much less than this value. The aim of the work described in the dissertation is to provide an improved understanding of the performance of AIN/TiN nano-coated solid carbide ball nose end-mill tool in milling stainless steel at low speed (below 100 m/min) under conventional flood and mist lubrication condition. The tool wear behaviour and the morphology of the surface finish obtained under different lubrication conditions were examined. In particular, the effect of the hardness of the workpiece, helix angle of the cutting tool and the effectiveness of mist and flood lubrication in low-speed milling of stainless steel were investigated. The machining were carried out at the cutting speed of 50 m/min and 88 m/min, depths of cut of 0.2 mm and 0.4 mm and feeds rate of 0.04 mm/tooth, 0.01 mm/tooth and 0.004 mm/tooth. The machining tests were performed on STAVAX (modified AISI 420 stainless steel) with the hardness of 35 and 55 HRC using Okuma milling machine under conventional flood and mist lubrication conditions. Abrasion, chipping and catastrophic failure are the wear modes encountered during machining under flood lubrication condition. The abrasive wear and the likeliness of the cutting tool to chip and fail prematurely increased with an increase in the hardness of the workpiece and a reduction in the helix angle of the tool. Small quantity of natural oil sprayed in mist form was effective in reducing the tool wear and severity of abrasion wear, and preventing catastrophic failure. Throughout the entire duration of machining of 35 and 55 HRC of stainless steel under mist lubrication condition, the cutting edge of the 25⁰ and 40⁰ helix angle tools only suffered small-scale edge chipping and abrasive wear. The ductility of the workpiece had Significant influence on the surface finish of the workpiece. In particular, it was found that in milling STAVAX with a hardness of 55 HRC, despite the tool was being subjected to a more severe wear, the surface finish was more superior than that of the workpiece with the hardness of 35 HRC.

Item Type:Thesis (Masters)
Uncontrolled Keywords:stainless steel, mist lubrication, conventional flood, low-speed milling, STAVAX
Subjects:T Technology > TJ Mechanical engineering and machinery
Divisions:SCHOOL > School of Engineering and Information Technology
ID Code:9520
Deposited By:IR Admin
Deposited On:11 Dec 2014 14:28
Last Modified:11 Dec 2014 14:28

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