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MIG Gun Welding Diffusers: Copper vs. Brass

Posted by Robin Reips on Feb 19, 2018 11:17:10 AM
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We often see different materials used for welding torches and their consumables. Mostly you can see Brass and Copper or Copper alloy - depending on the needs. Since there are various Copper alloys, we focus on the Copper Alloy: CuCr1Zr. Remember also that Brass, which is known as an alloy from Copper and Zinc, has many variations, as well. We will work with an example here.

Welding Diffuser Material Factors

Factors for choosing the right material for their individual use are mainly:

  • Heat conductivity
  • Electrical conductivity
  • Hardness
  • Yield strength

So let's take a deeper look in the different material properties. For the measurements we use the following formulas:

  • Heat Conductivity:  (W / (m-K) )
  • Resistance: ( (Ω-mm2)/m - at 20o C)
  • Hardness (HV):  Hardness - Vickers Scale
  • Yield Strength: (N/mm2)

Material

Heat Conductivity

Resistance

Hardness

Yield Strength

Copper 384 .0179 110 - 115 200 - 360
Copper Alloy 310 - 330 .0230 165 200 - 420
Brass 123 .05 - .07 Up to 140 360 - 500

These data are strongly dependent on the used alloy. So, how does this impact welding torch effectiveness?  You can reasonably say that Copper may be perfect with it's high heat conductivity and low electrical resistance. But, the low hardness and a faster softening with higher temperatures leads to a higher wear of this material. So, wear parts with this material are only recommended for lower ratings.

Copper Alloy Welding Diffusers

This Copper Alloy has also a high heat conductivity (even if it's a bit lower than copper) and a low electrical resistance. Due to the fact that it has a high hardness and is much more wear resistant (especially for abrasion caused by the moving welding wire), this makes the Copper Alloy tested here very useful for contact tips. For contact tips holders, Copper Alloy again seems to be favorable. Note: We use different Copper Alloys for contact tips and tip holders to prevent it from corrosion due to the same material combination.

Brass Welding Diffusers

Brass is an all-rounder. Because of the higher resistivity, lower heat conductivity and a "medium" hardness, you won't see it as a contact tip. But as a contact tip holder, it's likely to be used. But what's the advantage of Brass against Copper Alloy? On the one hand it's a matter of price. Brass is much cheaper, and so are Brass contact tip holders in comparison to Copper Alloy tip holders. On the other hand, it's also a matter of the yield strength. There is almost no wear of the contact tip holder due to abrasion caused by the welding wire. But the tip holder must withstand crashes and, more more commonly, the automated reamer cleaning. So the lifetime of the contact tip holder can be increased by Brass.

But how does it really impact welding performance? Well, we have tested many different kinds of materials due to design changes, material changes, etc.

When testing the heat behavior of the contact tip in a test with a tin bath, we used a Brass and a Copper Alloy as material for contact tip holders.

 Measuring Point Copper Alloy Tip Holder (Celsius)  Brass Tip Holder (Celsius)
 Contact Tip  161  178
 Inner Tube  102  98
 Tin Bath  250 250

The Brass tip holder causes the contact tip to become hotter. That's because of the lower heat conductivity.

That's also why the inner tube stays cooler.

Summary

Brass as a contact tip holder is okay as a cheaper alternative that can withstand the effects of automatic reamer cleaning better. It's thermal and electrical behavior is good for the use as contact tip holder, but cannot be used as a contact tip material.

Copper Alloy is a very good material for welding. It can be used for tips and holders. It has a very good electrical and thermal behavior, which leads to lower temperatures and reduce voltage drops. It can withstand the abrasion of the welding wire very good.  Lower contact tip temperatures lead to higher lifetimes and can prevent thermal overload of the wear parts. It's only weakness is the lower yield strength.

Topics: Welding Consumables