Investigation of Effects of Mig Welding on Corrosion Behaviour of AISI 1010 Carbon Steel
This paper presents the corrosion behaviour of welded low carbon steel at different welding voltages and filler materials. The welding process was conducted on butt joint 
specimens using the metal inert gas (MIG) technique at a welding voltage range of 19 to 21 V with 1 V interval, and the filler materials used were ER 308L and ER 70S-6 with 
1.2 mm diameter. Heat treatment through full annealing was done to the welded low carbon steel, and the corrosion behaviour was tested using a synthetic seawater 
environment with 3.5 wt% NaCl. Microstructure changes were observed using a scanning electron microscope (SEM). The results showed that the corrosion rate decreased when the welding voltage increased, as it directly affected the welding heat input. The welding heat input was found to have a significant effect on the corrosion rate as it changed the ferrite content in the microstructure of the specimens. Decrease in the corrosion rate was also found when the full annealing process was done to the 
specimens and ER 308L filler material was used. From a metallographic study, iron oxides and pitting were found on the surface of the exposed area after the corrosion test. 
It is apparent that the combination of higher welding voltage, heat treatment and the use of ER 308L filler material can reduce the corrosion rate of AISI 1010 carbon steel.
Characterization of Spot Weld Growth on Dissimilar Joints with Different Thicknesses
A sound weld from spot welding is what most of the manufacturers desired and preferred for mechanical assemblies in their systems. The robustness is mainly relied on the joining mechanism of mechanical parts. This paper focuses on the effect of parametric changes for dissimilar joints using 304 austenitic stainless steel and carbon steel with two different thicknesses. The pneumatic based spot welder was used to accomplish the entire welding process. The parameters varied throughout the experiments are the welding current and welding time while the electrode pressing force and electrode tips size are kept constant. The welding process was started from poor weld and move on to better weldment by increasing the process parameters. However, this study is limited to the basic parametric variation to find optimum parametric set up for 1 mm and 2 mm base metals. The welded specimens are later undergone the tensile test, hardness test and metallurgical test to characterize the spot weld growth for both thicknesses.
Hygroscopic Expansion of some Casting Investments
CREDIT is generally given to Taggart1 for introducing the cast gold inlay to the dental profession. Although he realized that gold shrinks when cooled from molten state to solid state of room temperature, the investment available to him did not supply sufficient compensation. In 1910, Van Horn2 published a paper dealing with a method by which he obtained the compensation by means of wax expansion. The next major research in connection with this problem was the work of Coleman3 at the National Bureau of Standards. He determined the gold shrinkage to be 1.25 per cent and presented a casting technic with compensation values of quantitative nature. The total compensation for the gold shrinkage was obtained by the combination of the setting and thermal expansion of the mold. This procedure is the general practice followed at the present time for compensation. There are some disadvantages to this method. Skinner has indicated the difficulty of obtaining smooth castings and the improper compensation for the casting shrinkage.4 It has been found by Hollenback5 and Scheu6a that castings made at a high temperature are rougher than those made at a low temperature (450° C.), depending upon the great difference in thermal expansion between plaster of Paris and silica, which causes a poor union of the fine particles. This may also result in friability and there may be some warpage due to the differential expansion. A method which provides sufficient compensation at a low mold temperature is the hygroscopic casting technic.b Wilson7 showed that certain plasters expand as much as 0.0044 inch to the inch by taking up moisture from the air. With this information at hand, Scheula, b tested some commercial investment to determine what results the addition of moisture would have. He found6b: (1) All of the casting investments that were tested expanded. (2) The thicker the mix, the greater the expansion. (3) A mix with hot water expanded more than one with cold water. (4) The time at which the mix is placed in the water is of great importance. It was found that if the mix is placed in the water early, it would not expand so much as when placed in a little later. It was also found that if the mix was placed in the water after a certain time, it could not expand to the maximal amount. (5) The temperature of the water in which the mix is placed is important, for two reasons; (a) the temperature of the water controls slightly the expansion of the investment, and (b) water at a temperature of 1000 F. slightly softens the wax pattern so that the fine margins are not marred while expansion is taking place. The mix should remain in the water at least 20 minutes to obtain the full expansion, after which time no further expansion is obtained.