In this work, the effect of heat input on the mechanical properties of low-carbon steel was studied using two welding processes: Oxy-Acetylene Welding (OAW) and Shielded Metal Arc Welding (SMAW). Two different edge preparations on a specific size, 10-mm thick low-carbon steel, with the following welding parameters: dual welding voltage of 100 V and 220 V, various welding currents at 100, 120, and 150 Amperes and different mild steel electrode gauges of 10 and 12 were investigated. The tensile strength, hardness and impact strength of the welded joint were carried out and it was discovered that the tensile strength and hardness reduce with the increase in heat input into the weld. However, the impact strength of the weldment increases with the increase in heat input. Besides it was also discovered that V-grooved edge preparation has better mechanical properties as compared with straight edge preparation under the same conditions. Microstructural examinations conducted revealed that the cooling rate in different media has significant effect on the microstructure of the weldment. Pearlite and ferrite were observed in the microstructure, but the proportion of ferrite to pearlite varied under different conditions.
The anti-corrosion properties of paints can be optimised when adequate proportion of the paint constituents are used. Effect of zinc powder addition to Villa Gloss and Silka Lux Marine Enamel paints on corrosion resistance of mild steel was studied. Quantitative Analysis and Potentiodynamic Polarisation Technique were used to evaluate the samples. The results indicate that zinc powder addition between 15 and 25 % significantly reduced the corrosion rate. The corrosion rate stabilized at approximately 0.10 mmpy when zinc powder added was above 15 %, independent of the exposure time. Potentiodynamic anodic polarization curves of the samples immersed in seawater showed that sample with 25% zinc powder addition exhibited highest corrosion potential and the least corrosion current density. Microstructural analysis of the samples also revealed the presence of pitting corrosion at the surfaces of the samples and their geometry, volume fraction and distribution vary with the zinc powder addition.Keywords: zinc powder, inhibition efficiency, potentiodynamic, weight loss, corrosion rate, pit corrosion NOMENCLATURE A1 uncoated sample. A2 sample coated with 10ml of white paint + 0% zinc powder. A3 sample coated with 10ml of red paint + 0% zinc powder. B1 sample coated with 10ml of white paint + 5% zinc powder. B2 sample coated with 10ml of red paint + 5% zinc powder. C1 sample coated with 10ml of white paint + 10% zinc powder. C2 sample coated with 10ml of red paint + 10% zinc powder. D1 sample coated with 10ml of white paint + 15% zinc powder. D2 sample coated with 10ml of red paint + 15% zinc powder. E1 sample coated with 10ml of white paint + 20% zinc powder. E2 sample coated with 10ml of red paint + 20% zinc powder. F1 sample coated with 10ml of white paint + 25% zinc powder.F2 sample coated with 10ml of red paint + 25% zinc powder. Cr corrosion rate (mmpy) Wt weight loss (milligrams) A Surface area of the sample (cm 2 ) T time of exposure of the samples in hour(s) metal density (g/cm 3 ) L length of the sample (cm) B breadth of the sample (cm) T thickness of the sample (cm)
Steels are used widely for production of machine components due to their versatility, low cost, ease of production and modification of their properties through heat-treatment. ST60Mn Steel is one of the common high strength steel produced in Nigeria and utilized for machine building purposes. Components made from this materials failed by wear, corrosion or both mechanism. The aim of this paper is to determine the influence of austempering heat-treatment on the corrosion-wear resistance of ST60Mn steel in cassava juice. The heat-treatment was performed by varying the austenitizing temperature, austempering temperature and time. The corrosion wear resistance was investigated under an instrumented pin-on-disc wear testing machine with the steel samples dipped in the cassava juice. The results obtained showed that the austempered ST60Mn steel has a wear rate of 3.0µg/cycle. While, the un-heat-treatment sample possess 70.1µg/cycle. This is a tremendous improvement in corrosion wear rate through the austempering heat treatment.
AISI 1018 mild steels are widely used for engineering applications in machine components and for structural purposes. These materials suffer mechanical damages especially when used under critical conditions of extreme load. In this study, the effect of austempering heat-treatment on the hardness, tensile strength, impact energy and the microstructure of AISI 1018 steels were evaluated. The steel specimens were subjected to austempering heat-treatment by austenitizing at a temperature of 830°C, maintained at this temperature for a period of 1 hour 30 minutes, before rapidly cooled down in a NaNO3 salt bath maintained at 300°C for isothermal transformation for a further 50 minutes before finally cooled down to room temperature. Microstructural analysis using Scanning Electron Microscope (SEM) shows transformation from ferrite/pearlite to bainite microstructure. The tensile strengths of the specimen increased from 400 MPa to 500 Mpa; hardness increased from an average value of 140Rc to 162Rc; while impact energy increased from 15.6 Joule to 30.6 Joule by the austempering heat-treatment. Keywords—Austempering, hardness, tensile strength, impact energy, microstructure
The mechanical properties as well as microstructure of Cu-30.6 wt% Zn alloys containing 0.01 wt% lead has been investigated. The brass alloy was cast and then cold rolled at various percentage reductions: 20%, 25%, 30%, 35% and 40% followed by stress relieving annealed at 450˚C. Hardness, ultimate tensile strength (UTS) and impact toughness values were evaluated at every stage of reduction. It was discovered that the strength, hardness and impact energy all increased with increased percentage reduction. Finally, the optical microscope of the samples was done and the result achieved correlated with the mechanical properties.
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