The causes of tungsten electrode cracking are complex, usually related to multiple factors such as the characteristics of the material itself, usage conditions, and welding environment, and the specific reasons are as follows:
1.Thermal Stress And Temperature Gradient Are Too Large
Tungsten has a very high melting point and low coefficient of thermal expansion, but its brittleness is high, and it is easy to generate thermal stress when the temperature changes drastically, causing microcracks or macroscopic cracks. In particular, cracking is prone to the following situations:
During rapid heating or cooling of electrodes, the temperature of the surface and the inside of the electrode vary greatly.
Arc suffocation or frequent arcing leads to local thermal shock.
2.Internal Stress And Structural Defects Of Materials
Tungsten materials may residue internal stresses during processing, which can be released during use if not adequately annealed or heat treated, causing cracks.
Defects such as microscopic cracks, inclusions or holes on the surface layer will become the starting point of crack initiation.
Uneven particle size or large grains can also reduce toughness and increase crack susceptibility.
3.Poor Gas Protection Or Impurity Pollution
Insufficient gas protection during welding, tungsten electrode exposure to oxygen, nitrogen, water vapor and other active gases, will cause oxidation or nitriding, reducing its crack resistance.
Tungsten is easy to react with oxygen at high temperatures to form WO₃, which is easy to volatilize and destroy the surface structure, inducing cracks.
Excessive hydrogen or moisture in the gas can also cause hydrogen embrittlement or micro-bursts.
4.Short Circuit Between The Electrode And The Workpiece Or Brazing Material
If the tungsten electrode accidentally adheres to the workpiece or comes into contact with the melt pool, it can cause local melting or tearing of the tip, leading to micro-cracks or even fractures.
5.The Current And Voltage Settings Are Unreasonable
Excessive current can cause the electrode tip to overheat, resulting in localized melting and gasification, reducing mechanical strength.
Abnormal voltage can cause arc instability or violent electrode oscillation, leading to structural faTIGue.
6.Improper Grinding Or Mechanical Damage
Using a rough grinding wheel or a misdirected grinding method can introduce microcracks or scratches to the surface of the tungsten electrode.
Rough handling or improper clamping can also cause mechanical damage to the electrodes.
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