Analysis on the causes of Tungsten defects in Weld Weld
1. Under the condition of tungsten electrode type and tungsten electrode diameter, the bearing capacity of tungsten electrode to current is limited. Excessive welding current will lead to tungsten electrode burning loss, and finally lead to tungsten inclusion defect. When the gas purity is not enough or the active mixture gas is selected as the protective gas, the protective effect will be reduced and the tungsten electrode will not be well protected and oxidized. DC reverse polarity or AC negative half cycle welding during TIG welding will increase the temperature of tungsten electrode, burn seriously and make tungsten particles enter the molten pool.
2. The operation factor welderundefineds operation skill is not high, the technique is not skillful, will cause the tungsten pole to touch with the workpiece or the welding wire often; when the weld seam is affected by the space position or the welding torch obstacle, will increase the operation process difficulty, increases the tungsten pole and the weld pool or the welding wire contact probability.
3. 3. At present, tungsten materials include pure tungsten electrode, thorium tungsten electrode, cerium tungsten electrode, lanthanum tungsten electrode, zirconium tungsten electrode and so on. The stability of pure tungsten electrode is not high and is rarely used at present. Thorium tungsten electrode is rarely used because of its certain radioactivity. The more tungsten materials are cerium tungsten electrode and lanthanum tungsten electrode. Cerium-tungsten materials have the advantages of non-radiation, low melting rate, long welding life, good arc initiation and so on. Lanthanum and tungsten have the advantages of better mechanical cutting performance, better creep resistance, higher recrystallizing temperature, good extensibility and so on. Due to the alternation of cold and hot temperature difference during welding, the end angle of tungsten electrode is small, so it is easy to produce stress concentration, which leads to the stress fracture at the tip of tungsten pole and the tungsten electrode falls into the molten pool to form tungsten inclusion. If the surface of tungsten electrode is rough, when welding, the oxide produced by high temperature accumulates locally in the movement to the tip, which leads to the accumulation of local oxide, which is easy to produce cracking phenomenon and leads to the formation of tungsten inclusion.
