| Effect of electrode covering on the mechanical properties of high tension steel weld has been investigated with domestic covered electrodes and prepared electrodes with various ingredients. Fluxing materials in the heavily covered electrode give the arc considerable stability, help to float out impurities from within the molten puddle, and develop inert gases which keep the outer surfaces of the molten weld from oxidizing. An addition of 1∼2% graphite in the electrode covering increases strength of the weld metal resulting from carburizing effect, whereas a larger amount of graphite (3∼5%C) makes it brittle causing CO gas blow hole formation. Excess amount of manganese in the covering materials may cause harmful effect, forming fish eye. Addition of iron also results in strength increment and gives the arc stability. Molybdenum produces superior strength and appearance of the weld metal and gives better weldability. It is, therefore, suggested that an addition of ferro-molybdenum to the covering materials would help to produce sound weld for high tension steel. |
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