Generally canoes are the most popular boat in leisure activity on the water. Recently, its demand has been continuously increased, furthermore, the recent users hope that those canoes are high degree of quality, mass production and cheap cost etc.. For solving this problems, the wooden canoe manufactured by the strip construction method has been commonly used for leisure activity of various field. However, this method mentioned above is not suitable for mass production which needs a effective operation, managements as well as cheap product cost. In this paper, the new construction method, called the piling-up laminated construction method which is composed with new both 3D design system and manufacturing technology to satisfy all the canoe shape accepting previous user's various needs and the need of mass production is studied with using the laminated wooden plates. The manufacturing technology of the laminated plate kit type could be applied flexibly in both the mass production and small production by user's order. Furthermore, the laminated plate kit type compared to the strip construction method could be decreased to about 1/3 the time required for production, manpower and cost. Consequently, it could be verified that the laminated plate kit type was able to make a major contribution to improve the reliability of product.
Aluminum is on active metal, but it is well known that its oxide film plays a role as protective barrier which is comparatively stable in air and neutral aqueous solution. Thus, aluminum alloys have been widely applied in architectural trim, cold & hot-water storage vessels and piping etc., furthermore, the aluminum alloy of AC8A have been widely used in mold casting material of engine piston because of its properties of temperature and wear resistance. In recent years, the oil price is getting higher and higher, thus the using of low quality oil has been significantly increased in engines of ship and vehicle. Therefore it is considered that evaluation of corrosion resistance as well as wear resistance of AC8A material is also important to improve its property and prolong its lifetime. In this study, the effect of solution and tempering heat treatment to corrosion and wear resistance is investigated with electrochemical method and measurement of hardness. The hardness decreased with solution heat treatment compared to mold casting condition, but its value increased with tempering heat treatment and exhibited the highest value of hardness with tempering heat treatment temperature at 190 ℃ for 24hrs. Furthermore, corrosion resistance increased with decreasing of the hardness, and decreased with increasing of the hardness reversely. As a result, it is suggested that the optimum heat treatment to improve both corrosion and wear resistance is tempering heat treatment temperature at 190 ℃ for 16hrs.
Two types of welding methods were performed on austenitic 304 stainless steel: laser welding and TIG welding. The differences of the corrosion characteristics of the welded zones from the two welding methods were investigated with electrochemical methods, such as measurement of the corrosion potential, polarization curves, cyclic voltammogram, etc. The Vickers hardness of all laser-welded zones (WM:Weld Metal, HAZ:Heat-Affected Zone, BM:Base Metal) was relatively higher while their corrosion current densities exhibited a comparatively lower value than those which were TIG welded. In particular, the corrosion current density of the TIG-welded HAZ had the highest value among all other welding zones, which suggests that chromium depletion due to the formation of chromium carbide occurs in the HAZ, which is in the sensitization temperature range, thus it can easily be corroded with an active anode. Intergrenular corrosion was also observed at the TIG-welded HAZ and WM zones. Consequently, we can see that corrosion resistance of all austenitic 304 stainless steel welding zones can be improved via the use of laser welding.
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