EFFECT OF THE ACCESS OF AMBIENT AIR IN DRILLING OF STEEL
EDER SILVA COSTA1; MATHEUS CARRARA MARTINS1; WISLEY FALCO SALES1; ÁLISSON ROCHA MACHADO1; JAMES WALLBANK (in memorian)2
1 Faculty of Mechanical Engineering - Federal University of Uberlândia; 2 School of Engineering - University of Warwick, Coventry, Reino Unido, UK
doi:10.20906/CPS/COB-2015-2373
Resumo
The aim of this work is to analyse how the ambient air restriction, which surrounds the workpiece-tool-chip system, influences the surface roughness Ra, the thrust force and torque, in drilling of AISI 1010 steel with HSS twist drills. This research was developed in the laboratories of Warwick Manufacturing Group - WMG - School of Engineering - University of Warwick, Coventry, England, UK. The workpiece was a plate with dimensions of 200x100 mm and 50 mm thick. Tests consisted of machining holes of 10 mm diameter and 40 mm deep, pre-drilled with 3 mm diameter in two conditions: 1) pre-drilled with 45 mm depth, but non through holes; 2) pre-drilled through holes - in this case it was intended to facilitate the entry of ambient air during the drilling of the holes. Sixteen (16) tests were performed and for each trial was used a fresh drill for each set of 5 holes. The tests were carried out under the following atmospheres: ambient (dry machining) and application of nitrogen gas at pressures of 300 bars, in order to create a protective atmosphere in the inlet region of drilling, and thereby inhibit the presence of oxygen. The results obtained, using a Design of Experiments - 24, indicated that the situation that facilitates the access of air during machining worsened the surface roughness and increased the thrust force and torque.
Palavras-chave: Drilling; HSS drills; Quality of holes; Oxygen restriction; N2 Protective atmosphere