Papers by Keyword: Stainless Steel (SS)

Abstract: This investigation concerns the influence of key parameters of laser welding on the geometry and microstructural properties of the weld bead. The study is intended to restrain the interval field of the welding parameters and to investigate the welded joints achieved through this technique. A 3,3 kW Nd:YAG laser together with a Rofin welding head and an ABB 6-axes robot were used for this investigation. The tests highlight the major influence of the laser spot diameter on the geometry of weld bead. The experiments were made on various samples of AISI 304 thin sheets. In depth characterization of the weld area was conducted by means of optic and electronic microscopy and EDS analyses.

Abstract: The purpose of the study was to investigate the microchemical, morphological, mechanical and anticorrosive characteristics of the metallic brackets by using energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), electrochemical and shear tests. The changes resulted from the exposure of the metallic brackets to artificial saliva and debonding forces were investigated under orthodontic appliances. The results have shown that metallic brackets studied in this paper present a good design, great electrochemical behaviour in artificial saliva for different pH values (2, 5 and 7), and also great mechanical properties. In the case of shear stress the obtained values were higher than the clinical accepted value. The metallic brackets studied in this paper present a good behaviour in artificial saliva, and good mechanical characteristics. The ARI investigation revealed that most of the adhesive was left on the bracket.

Abstract: The main purpose of this paper is to study the carbide tip's surface temperature and the cutting forces of milling stainless steel with nose radius worn tools. A new cutting temperatures model incorporating tool worn factor and using the variations of shear and friction plane areas occurring in tool worn situations are presented in this paper. The frictional forces and heat generation on elementary cutting tools are calculated by using the measured cutting forces and the oblique cutting analysis. The tool tip and cutting edges are treated as a series of elementary cutting tips. The carbide tip’s temperature distribution is solved by finite element analysis (FEM) method. Keywords: Milling, stainless steel, cutting temperatures, nose radius tools, FEM

Abstract: This paper describes the applicability of air jet assisted (AJA) machining to stainless steel and titanium alloy at high cutting speeds in terms of tool wear and tool life. A specially designed tool holder with an air nozzle very close to the tool tip was prepared for turning stainless steel. From the experimental results, it was found that the application of flood coolant from the side of the end flank face leads to better result in tool life in AJA machining of stainless steel than that from the side of the side flank face. The assistance of air jet can improve the tool life of the M35 CVD coated insert in machining of the stainless steel by 36 to 100% under the optimal conditions in comparison with wet machining. It was also found that the air jet assistance extended the tool life of the S10 PVD coated insert by 48% in turning titanium alloy. The tool life extension of the coated insert in AJA machining titanium alloy is much longer than that of an uncoated carbide insert.

Abstract: Machine tool chatter is a type of intensive self-excited vibration of the individual components in a machine-tool-fixture-work system. Chatter affects the cutting process and may lead to negative effects concerning surface quality, cutting tool life, and machining precision. However, modern manufacturing industries and their end users demand fine surface finish, high dimensional accuracy as well as low operation costs which include the cost of tooling. Therefore, any effective damping technique, which reduces or eliminates chatter, will significantly improve tool life and will be a profitable technique to implement in the industry. This paper presents a novel chatter control method in turning of (AISI 304) stainless steel by using permanent magnets. The study compared tool wear under two different cutting conditions: normal turning and turning with magnetic damping. A specail fixture made of mild steel was designed and fabricated in order to attach a powerful neodymium permanent magnet (4500 Gauss) to the carraige of a Harrison M390 engine lathe. The arrangement ensured that the magnet was placed exactly below the tool shank. The main idea was that the magnet will provide effective damping by attracting the steel tool shank and restricting its vertical vibratory motion during cutting operations. A Kistler 50g accelerometer, placed at the bottom front end of the tool shank was used to sense vibration. The data was then collected using a Dewetron DAQ module and analyzed using Dewesoft (version 7) software in a powerful Dell workstation. Response surface methodology (RSM) in Design Expert software (version 6) was used to design the sequence of experiments needed based on three primary cutting parameters: cutting speed, feed, and depth of cut. The tool overhang was kept constant at 120 mm in order to facilitate the attachment of the magnet fixture. Analysis of the recorded vibration signals in the frequency domain indicated that significant reduction in the vibration amplitude, as much as 86%, was obtained with magnetic damping. Next tool wear was analysed and measured using a scanning electron microscope (SEM). It is found that tool wear is reduced considerably by a maximum of 87.8% with the magnetic damping method. Therefore, this new magnetic damping method can be very cost effective, in terms of vibration reduction and tool life extension, if applied to industrial turning operations of metals.

Abstract: The The basic hypothesis of this article focuses on the study of accompanying phenomenas in the cutting zone of the stainless steels, with regard to the elimination of occurrence of poor-quality holes when drilling into new austenitic ELC (Extra Low Carbon) stainless steels. The problem of drilling holes with diameter D=1 to 9 mm resides in the fact that 20 to 28 % of these holes do not comply with prescribed requested requirements. The result of the deformation is very often the unforeseen destruction of the cutting tools; therefore their operational tool life is reduced. This article presents the results of experiments focusing on the study of the plastic deformation of the chips, at drilling with diameter d=5 mm when drilling into a new austenitic ELC stainless steels. This study also includes an analysis of accompanying phenomena in the cutting zone by measuring some selected parameters. The results of the experiments were compared with Cr18Ni8 steel and then verified when drilling holes into specific products.

Abstract: The basic hypothesis of this article focuses on the changes in the plastic deformation under the machined surface during drilling. For experiments applied a new Cast Iron GTW 35-04, Stainless steels DIN 1.4301 and ISO C45 carbon steel. The problem of drilling holes with diameter D=2 to 15 mm resides in the fact that 20 to 30% of these holes do not comply with prescribed requested requirements. This article presents the results of experiments focusing on the study of the damage process in helical drills with diameter d=6.0 mm. This study also includes an analysis of accompanying phenomena in the cutting zone by measuring some selected parameters.

Abstract: Electropolishing is a process for the surface finishing of metals and alloys, achieving brilliant surface finish with very low surface roughness values. The most common electrolytes for the electropolishing of stainless steel are varying concentrations of phosphoric and sulphuric acid, and occasionally additives such as chromic acid. The objective of this study was to assess the performance of three commonly used industrial electrolytes in terms of the surface finish of electropolished stainless steel. Each electrolyte had different concentrations of phosphoric acid, sulphuric acid, and chromic acid. The following electropolishing conditions were assessed: current density, bath temperature, electropolishing time, initial textures, and electrode positions. This study on the performance of three industrial electrolytes for the polishing of stainless steel AISI 316L revealed that adding chromic acid does not significantly enhance surface finish, and electropolishing ranges were quite similar for all three electrolytes.

Abstract: 316L stainless steel is a well known advanced material for its good corrosion resistance in many aggressive situations. As the quality of different manufacturer of the stainless steel may vary in some degree, this paper studied the corrosion resistances of three 316L stainless steels which supplied by three manufacturers. The results show that the difference of the corrosion rates of the three 316L stainless steels in 5% H₂SO₄ or 3.5%NaCl solutions is one time in quantity. The reasons for the difference can be explained by compositional and metallographic factors.

Abstract: Stainless steel sheets are successively heated to a temperature of 1150°C and cooled until ambient temperature during the production process. Requirements for high cooling rates of stainless steel sheets producers lead to use water as a cooling medium. The information about cooling intensity (heat transfer coefficient) of different nozzles configurations is necessary for designing cooling sections. Although many researchers deal with water spray cooling, actually a general correlation for predicting heat transfer coefficient for wide range of nozzles configurations does not exists. That is the reason why heat transfer coefficient for different nozzles configurations can be only obtained by laboratory measurements. Heat transfer coefficient is mostly influenced by water impingement density and impact velocity. However other factors e.g. water temperature and velocity of the sheet can influence the heat transfer coefficient. Optimized design of the cooling unit with high cooling intensity and low water consumption was achieved by appropriate choice of these parameters. The moving experimental sheet was cooled from a temperature of 900°C to a temperature of 50°C with various configurations of nozzles. The tests shown that heat transfer coefficient was increasing with water impingement density and impact velocity. Increasing water temperature from 20 °C to 80 °C caused a decrease of the heat transfer coefficient and Leidenfrost temperature. The effect of velocity is negligible when velocities are between 25 and 100 m/min. The cooling unit was designed according to laboratory measurements to fulfill the stainless steel producer's requirements. The measurements which were done in an industrial plant confirmed the accuracy of heat transfer coefficient obtained in the laboratory. The maximum difference between laboratory and plant measurements was 15%.