The analyses of chips indicate that all of them may be classified as continuous, except those from HSM condition. Figure 4a shows clearly the continuity of chip lamellae for conventional milling condition. The saw-tooth type originating from HSM is confirmed by Figure 4b. Despite its shape, the HSM chip presents segmentation degree of 28% only (percentile band ligament height), indicating an initial adiabatic shear process. Thus, the HSM chip can not be classified as segmented one once there is deformation of the microstructure (ferrite-pearlite) inside lamellae and bands with concentrated shear are not clearly defined. Probably the low hardness of the workpiece limited the segmentation process even at higher cutting speed.
The values of rate constants k, increased with increasing in temperature and this observed from both models. Jianguo et al.  , who study the corrosion oflowcarbonsteel in acid media at different concentrations. The value of slope B is constant up to 1.5 M acid concentration and then it reduced to a lower value for acid concentration grater than 1.5 M. The change in slope (value of B) may be due to the formation of a tightly adsorbed more protective corrosion products layer on metal surface at high acid concentration  . In this study, the values of B approximately constant with temperature changes, with average value of 0.551 and it is constant through acid concentration range, indicating that the mechanism of corrosion reaction is the same at different acid concentrations. The values of n, which obtained from
Due to the complexity of controlling parameters in carburization, there has been relatively little work on process variables during the surface hardening process. This work focuses on the effectsof the carburizing temperature and time on the mechanical properties of mild steel carburized with activated carbon, at 850, 900 and 950 °C, soaked at the carburizing temperature for 15 and 30 minutes, quenched in oil, tempered at 550 °C and held for 60 minutes. Prior carburization process, standard test samples were prepared from the as received specimen for tensile and impact tests. After carburization process, the test samples were subjected to the standard test and from the data obtained, ultimate tensile strength, engineering strain, impact strength, Youngs’ moduli were calculated. The case and core hardness of the carburized tempered samples were measured. It was observed that the mechanical properties of mild steels were found to be strongly influenced by the process of carburization, carburizing temperature and soaking time at carburizing temperature. It was concluded that the optimum combination of mechanical properties is achieved at the carburizing temperature of 900 °C followed by oil quenching and tempering at 550 °C.
and to adsorb on the electrode surface, decreasing the corrosion rate of the low-carbonsteel. The OCP values also shifted to more negative potentials, but a more pronounced effect was observed for the E corr values, indicating that the adsorption could be a potential-dependent process. Indeed, to demonstrate indubitably such dependence with the potential, further experiments would be needed. Besides, the differences between OCP and E corr values were not so high, suggesting that the observed difference can also be due to the different techniques used, since OCP measurements were determined at I = 0 (zero) while E corr
The effectsof quenching temperature on tensile strength and hardness of the MLAWS are shown in Fig.2. When quenching temperature is lower than 900ņ, the hardness increases with the increase of temperature, while the hardness starts to drop with further increase in quenching temperature above 900ņ. The MLAWS has excellent hardenability in the temperature range of 860-940ņ. When the quenching temperature is relatively low, the contents ofcarbon and alloying elements dissolved in high- temperature austenite are also relatively low, which results in the formation of pearlite along with bainite and martensite, leading to low hardness and poor wear resistance  . If the
HSC is a relative term which depends on the workpiece material and on the chip formation process. According to Flom and Komanduri (1989), HSC for a given material can be defined scientifically as that speed above which shear localization develops completely in the primary shear zone. For soft workpieces HSC generates continuous chips, while difficult-to-cut materials develop segmented ones. From an industrial standpoint, HSC is defined in terms of cutting speed ranges, where cutting speed is elevated and feed per tooth and depth of cut are diminished aiming at finishing and semi-finishing operations (Schulz, 1999; Müller and Soto, 1999; Tönshoff et al. 2001). The transition between conventional cutting speed and HSC is still not entirely clear.
On temperature and voltage curves from ATND method one can observe thermal and voltage effects present on the curves in form of characteristic „peaks”. Values of temperature and voltage read outs for those characteristic points have become the base to taking up regression analysis aimed at obtaining mathematical dependencies, illustrating impact of change of those values on mechanical properties of alloys .
3.3 Calibration curve and analytical performance Calibration curve for the determination of Cr(III) on the AuNPs- GCE was achieved by DPSV under optimum conditions. Fig. 3 shows voltammetric performance and calibration curve for different concentrations of Cr(III) at deposition potensial -1.5 V, deposition time 90 seconds, scan rate 0.05 V/s and amplitude modulation 0.05 V. The regression equation and correlation coefficient are y = 0.142 + 0.004x and r = 0.9955, respectively. The resulting calibration plots is linear over the range from 0.5 to 75 ppb. The reproducibility of the AuNPs-GCE was estimated from the response to each 1 ppb of Cr(III) at replicates measurements. This series yield a mean current response, referred to as sensitivity, of 0.14 µA ppb-1 corresponding to a relative standard deviation (RSD) of 2.4%. The detection limit is 0.01 ppb based on three times the standard deviation of the baseline, calculated according to the reference . The calculated detection limit of the proposed method is better than previous reported methods including the Cr(III) determination using sophisticated ICP–MS (Table 1). Usage of AuNPs modified electrode gives at least one order of magnitude better detection limit than previous reported voltrametric methods using film electrodes. Limited publication of Cr(III) voltammetric detection compared with those of Cr(VI), in addition to its relatively poor sensitivity of non-gold electrodes lead us to infer that to obtain high quality of Cr(III) voltammetric profiles require gold or gold-modified electrodes. Previously it is known that high quality voltammetric profiles for Cr(III) oxidation were found to appear only at a gold electrode .
This paper presents subsurface hardening results of the low-carbonsteel plate, deformed under industrial test conditions by punches manufactured in quenched and tempered AISI D2 steel, with and without TiN coating. The punches are 12º double shear angle shaped. A longer tool life was obtained in tools with TiN coatings applied by Physical Vapor Deposition (PVD) process. The depth of hardened layer generated through punching was different for the work piece and slug. In the workpieces, this layer was about 1.5 mm wide, whereas in the slugs no hardness stabilization values were observed up to 4 mm. Moreover, the presence of the TiN coating did not affect the subsurface hardening produced by punching. The results were discussed regarding the wear mechanisms and the role of TiN coating at the interface. Therefore, the thermal effects were not relevant during the punching tests.
Today’s industry aims at such situation, where number of defective products, so called defects shall approach to zero. Therefore, one introduces a various changes in technology of production, introduces improvements which would help in accomplishment of this objective. Another important factor is introduction of different type of testing, which shall help in assessment which factor has significant effect on quantity of rejects, and which one could be neglected. Existence of casting rejects is unavoidable; therefore a new ideas, technologies and innovations are necessary in the entire widely understood foundry branch, in order to minimize such adverse effect. Performance of tests aimed at unequivocal determination of an effect of vibrations during crystallization on mechanical properties and porosity of the AlSi13Cu2 alloy was the objective of the present work. To do this, there were produced 36 castings from AlSi13Cu2 alloy. All the castings underwent machining operations. Half of the casting was destined to strength tests, the other half served to determination of an effect of vibrations on porosity of the alloy. The specimens were divided into 12 groups, depending on amplitude of vibrations and tilt angle of metal mould during pouring operation.
The growth rate of austenite is believed to be controlled by either volume diffusion ofcarbon or by boundary diffusion of substitutional alloying elements. If the growth rate of austenite is controlled by the bulk diffusion of atoms in austenite ahead of the interface, the diffusion ofcarbon may play a more important role than that of the substitutional alloying elements. Diffusivity of the substitutional alloying elements in austenite is far slower than that ofcarbon, and the substitutional alloying elements may not diffuse a long distance during the reaction. However, as described by Porter and Easterling , at the lower temperatures, boundary diffusion of substitutional alloying elements is the dominant mechanism in the diffusion process. It can be supposed that for the heating rate of 1.0 °C/s the growth rate of austenite is primarily controlled by the volume diffusion ofcarbon in austenite, due to the fact that the transformation takes place mostly at higher temperatures (parameter K = 2 × 10 − 3 ). Conversely, at
This component presents a geometrically complex structure made from AISI 4130 tubular steelof different dimensions and TIG welded in several angles [5, 6]. For the Brazilian aircrafts T-25 Universal and T-27 Tucano, for example, besides supporting the motor in balance, the motor-cradle also maintains the nose landing gear fixed at the other extremity. Since the motor cradle is a component critical to the flight-safety, the aeronautic standards are extremely rigorous in its manufacturing, by imposing a "zero-defect index" on the final weld seam quality (Safe-Life philosophy), which is 100% inspected by non-destructive testing/NDT [5, 6]. For this reason, welded aeronautic structures are frequently subjected to successive repairs in accomplishment to current standards. As a consequence, components approved by NDT may contain a historic record of welding repairs whose effectson their structural integrity are not computed. In addition, these structures are also submitted to weld repairs along their operational life, turning this question more complex. An investigation on 157 motor-cradles fracture reports of the T25- Universal aircraft model indicates that all of them occurred at welded joints as a result of fatigue cracks, reducing the “Time-Before-Fail” from 4.000 h to 50 h of flight . Motivated by high fracture incidence of this particular component, an extensive research program to evaluate the manufacturing and maintenance weld repair effectson the structural integrity, mechanical properties and microstructural changes has been conducted . The aim of this study is to analyze the effectsof the TIG welding repair on the structural integrityof the AISI 4130 aeronautical steel by means of experimental fatigue crack growth tests in base material (BM), heat affected zone (HAZ) and weld metal (WM).
Nanoparticles as a new generation of materials are used in many fields. The basic methods for their preparation are the top- down and bottom-up techniques. The essence of the top-down technique consists in grinding the material to particles with nano dimensions, while the bottom-up technique assumes making structures from molecules or single atoms [1,2]. According to a method recently developed, the nanoparticles of metal oxides are produced through anodic dissolution of metals . There are also thermal methods of obtaining metal nanoxides [4-7].
Carbonsteel C120U grade is largely used on the tools for cutting, for dies and knives, for stamping and drawing tools, hobs, thread rolling tools and in many other applications due to her typical properties - high hardness, good toughness and compressive strength. The surfaceof the steel can be modified by using surface engineering's techniques. Remelting of the surface layer by the source of concentrated energy is promising technique to improve properties of the materials [1-6]. Laser or electron beam use to melting of the surfaceof tool steels aims to obtain a modified layer with increased microhardness and abrasion resistance [7,8]. The surface remelted layer has usually a finer and more homogenous structure than its original base material. The remelting with the arc plasma (TIG- tungsten inert gas or GTAW - gas tungsten arc welding) used as an economical and easily
This article examines the effect of prolonged time of holding at the temperature of 620 0 C on the processes of secondary phase precipitation and mechanical properties oflow-alloy cast steel with an addition of vanadium subjected to two variants of heat treatment, i.e. U:1150 0 C+H:950 0 C+O:620 0 C and H:950 0 C+O:620 0 C. To determine an impact of the applied heat treatment operations, testing of mechanical properties and microstructural examinations of the cast steel with 0,21 and 0,27%C were carried out.
seeds weight, samples were taken randomly from harvested seeds of each subplot, the samples were weighed and the mean weight was obtained. On the other hand, weed population and percent ground cover were measured four weeks after emergence using 0.1 m 2 quadrant at six random positions per plot, two days before the scheduled weeding. 2.5 Performance of Chisel Plow and Disc Harrow Technical performance was conducted to compare chisel plow, the newly introduced implement in the irrigated schemes, and the disc harrow the widely used in the Gezira scheme, the comparison included measurement of draft, travel reduction (slippage), drawbar power determination, measurements of actual field capacities and efficiencies, and measurement of fuel consumption rates. For draft measurement, two tractors with the same horse-power were used as a test and auxiliary to estimate draft requirement for the chisel and the tandem disc harrow using hydraulic dynamometer at the assigned depths (10 cm and 20 cm), the measurements were performed according to Bukhari et al.
Ot can be observed in the grain boundaries map (Figure 2) the evolution from a regular and well-designed grain shape microstructure in as-received steel (Figure 2a) to a iner and less regular one in the sample submitted to thermomechanical treatment (Figure 2b). It can be seen, from histograms in Figure 3a, b, that as-received steel has a misorientation frequency close to normal distribution, while for sample deformed at 10% an increase of frequency at low angles (2 ° to 15 °) as well as at high angle (50 ° to 60 °) is observed (Figure 3b). This tendency is maintained in other treatment conditions, with the occurrence of the highest frequency oflow angle in the sample deformed at 25%. This result, reinforced by SEM images, shows that change
In 2010, buildings accounted for 32% of the total global final energy use and 19% of energy-related greenhouse gas (GHG) emissions (LUCON et al., 2014). The Brazilian residential buildings were responsible for 21% of the country’s electricity consumption in 2015 (M INISTÉRIO…, 2016). Brazil is a developing economy, a factor that influences the building sector. There is a housing deficit in the country and to overcome this problem, the Brazilian government has developed housing programs in recent decades such as “My house, My Life” (Minha Casa, Minha Vida) (PAULSEN; SPOSTO, 2013). Despite failures and criticism mainly related to the quality of the houses built, this program was responsible for the construction of thousands of new homes for people in need, thus alleviating the housing deficit in the country. These social housing programs mainly used the brick masonry system. However, new building systems, which may be more rational and productive, are being considered, such as precast and prefabricated concrete, concrete walls and light steel framing. The latter has been imported from the USA and its use is becoming widespread in the country, due to higher productivity and the dry construction process (LIMA, 2016).
Suppose that the subunit denoted 1 of bainitic ferrite forms without diffusion, but any excess carbon is soon rejected into the residual austenite. Consequently, all the subunits denoted 1 were formed at the early stage of transformation from austenite whose carbon concentration is initially identical to that of bulk alloy (region of upper bainite). The subunits denoted 2 and 3 were formed from enriched austenite as a consequence ofcarbon redistribution occurring after the growth event (region of lower bainite). The transition between these two regions is not sharply defined. There is then the possibility of the reaction beginning with the growth of upper bainite but decomposing to lower bainite from the enriched austenite at the later stages of reaction. This explains why both upper and lower bainite sometimes can be found in the same temperature.
During cooling, the crystallisation of cast iron deviates from the equilibrium state. This means that the austenite gets supersaturated with carbon and chromium, which greatly reduces the temperature of its transformation. Under these conditions, it is possible to obtain at room temperature the matrix of austenitic or austenitic-pearlitic character, as shown by respective microstructures. Total content of the carbide phase can be determined from F. Maratray’s  formula, namely: