The big radiator material test: How much copper and technology is in the Watercool Mo-Ra3 360 Pro? | Part 4

Watercool Mo-Ra3 360 Pro

They advertise copper for the tubes, aluminum (for the fins) and steel (housing), stainless steel (fan mounting frame) and a durable powder coating. And you can see at first glance that the ends of the copper pipes and connections (bends) have been joined on the inlet and outlet side. So not exactly what the good old plumber does when he lays copper pipes and solders them together. At pressures of 5 bar or more and possible temperatures above 110 °C, tin-free brazing solder would certainly be the method of choice, but here? And let me spoil it in advance: I have found neither tin nor lead. You don’t need either…

On the other side of the radiator there are no soldered joints or steps, which indicates that U-tubes have been installed which are only connected to the next U on one side, so that at the end a kind of loop is created from a total of four channels working in parallel, which makes the whole thing less restrictive.

Material analysis

Let’s open the radiator at the pre-chamber (tank). The acetal block sits directly on the four pipe ends for the inlet and is sealed with O-rings. The fins are pressed onto the pipes over a large area so that nothing needs to be soldered here.

The U-tubes used are made of pure copper and disappear into the depths of the radiator universe, only to return to the surface after a 180° bend (U).

But what at first glance looks very much like a simple soldered connection may not be one at all. But it is probably a so-called hard solder, such as a copper-phosphorus solder, where copper can be soldered without flux. The self-fluxing effect would be caused by the alloyed phosphorus, which turns into phosphorus pentoxide when the solder melts with atmospheric oxygen, which then reacts with the copper oxide formed on the copper surface to form copper metaphosphate with a fluxing effect. But I have not found this, nor have I found the corresponding residues. That’s a trick, you can easily get rid of it with diluted sulphuric acid.

I simply cut out this piece and looked at it from the side at a slightly higher magnification. What we see here from the side are two copper tubes of similar diameter, with the inner tube bent open in a trumpet shape and then the tubes pushed together. This increases the surface area and makes it easier to position the whole thing inside each other.

As it looks from the outside, and the supplier will not reveal this, the whole thing is probably hard-soldered. But how exactly? Since all OEMs keep their secrets and you usually don’t find out, I had to crack a somewhat tougher nut this time. That’s why I ask you to consider the following explanations as hypothetical, even if it actually looks clear. However, the following conclusions are logical and technologically plausible, but have not been officially confirmed by the provider.

If you enlarge the whole thing further, you can see the brazing alloy much more clearly, especially as it has a slight discoloration:

From the outside, however, you can’t see any conventional solder joints, apart from the different coloration. This led me to the so-called induction welding with an attached ring made of a special copper alloy. If, for example, the Israeli OEM Lordan were brought into play at this point, it would even be plausible, because it can do this. Even really well.

So how does it actually work? During induction welding, a high-frequency alternating current is passed through an induction coil. When a conductive material such as a copper pipe is brought close to the coil, the magnetic field of the alternating current induces eddy currents in the material. These eddy currents generate heat due to the electrical resistance of the material. If the heat generated is sufficiently high, the parts of the copper pipe to be connected can fuse at their points of contact and form a permanent connection. I have enlarged the connection point a little further here, where you can also see the melted ring (right-hand side), which has a smaller curvature.

When welding copper or other metals in this way, a vacuum is generally not required and the pre-assembled radiator can be used without stress. The need for a vacuum is more common with other specialized welding methods, such as electron beam welding or laser welding, where a vacuum can help prevent oxidation of the material and ensure a clean weld in a controlled environment. Here it then regulates the brazing alloy used in the form of the ring to be melted. At least that’s my conclusion.

Although induction welding takes place in an open environment, it is still important to clean the surfaces of the metals being joined to ensure a high quality weld. Oxidation can still be a factor, especially with metals that oxidize easily, but controlling the environment and using shielding gases such as argon can help minimize oxidation and improve the quality of the weld joint without the need for a vacuum.

Slight potassium residue can be found on the surface of the slightly rougher joint arcs.

Underneath this thin layer is pure copper again.

I’ll take care of the rest and the summary on the next page, so please turn the page again!