There are several varieties of contact tips to choose from. These come in different types of material and different shapes. For the purpose of this article we are going to discuss the two most popular contact tips used in industry today. These contact tips are either copper (E-CU) or copper chrome zirconium (CuCrZr).
The function of the contact tip is to transfer the welding current to the wire as it passes through to create the arc. The wire should feed through with minimal resistance, while still maintaining electrical contact.
Like all equipment it is important to purchase a quality contact tip. A quality tip will typically cost a little more but the long-term advantage will offset any price differences. Higher quality contact tips will last longer due to the fact that they are machined to tighter tolerances — the bore size maintains a consistent tolerance resulting in less friction as the welding wire passes through, improving feedability. The result will be fewer burn-backs and a consistent arc due to superior electrical conductivity.
Standard copper (E-CU) tips are the most common tip used in welding, and has the highest electrical conductivity compared to other alloys of copper. The result of the higher conductivity is better arc starts, and a very stable arc. The disadvantage to a standard copper tip is that it has a lower melting point and is softer than other alloys, meaning they may have to be changed more frequently. To offset frequent changes many companies offer a heavier walled contact tip that may help with heat dissipation if paired with a heavy diffusor and nozzle.
Chrome Zirconium (CuCrZR) contact tips are a harder copper alloy offering very good wear resistance. Many times these are used in robotic applications since the arc on time is typically higher than manual applications. The disadvantage to this alloy is that the electrical conductivity is lower than standard copper and, in some cases, may cause arc starting issues along with an increase of weld spatter due to a less stable arc.
- E-CU (Copper): Hardness 110 HV, electrical conductivity approximately 57 m / Ωmm2
- CuCrZr (Copper Zirconium): Hardness 160 HV, electrical conductivity approximately 40 - 50 / Ωmm2
Welding engineers have several choices when it comes to which contact tip is best for their application. Cost conscious companies should consider conducting studies to determine which type of contact tip is the most cost effective.
Choosing the correct contact tip and understanding how to keep it performing at its best are just as critical as choosing all the other components and parameters needed to produce a quality weld.