Alloy Welding What You Need to Know
I’m sure that some of you have already heard about alloy welding but not sure what it is. Alloy welding is the process of joining alloys or non-alloys with alloys using also alloys in the form of electrodes.
Alloys are kinds of metals that are light, ductile, heat resistant but with high thermal conductivity. They can be described as types of metals that are formed by combining two or more elements wherein at least one of them is metal.
Alloys are utilized in our industries on a variety of applications from fabrications of surgical tools to the manufacturing of aircraft bodies for the aerospace industry. But what are alloys made of? If you want to weld together alloys like aluminium which is a soft metal, can welding aluminium alloy be possible?
Alloys come from different compositions and are generally softer and oxidize much faster. They are, technically speaking, not always easy to weld but still possible by following certain welding processes and by choosing the right materials for fillers.
Considerations When Welding Alloys
Before we could tackle how alloy welding works, we also have to know the kinds of alloys that welders use and these are the “welding alloys” and the “filler alloys”.
The welding alloys are used in filling the gaps between two metals. Examples of these ferrous and non-ferrous welding alloys are bronze, aluminium, steel, titanium, zirconium, copper, nickel and magnesium.
The filler alloys are fillers with pure alloy composition and come in a variety of forms like paste, powder, foil, and sheet. These fillers liquefy quickly with heat and can seep into the space between narrow metal fittings and produce the soldered or a brazed joint.
Because of the growing needs for welding alloys, we are now able to incorporate the welding alloys and the filler alloys into single forms and that is how we’ve come up with the wire electrodes made of alloys. These alloy electrodes are the ones you may be using with your TIG or MIG welders.
Unfortunately, we have a slight problem when it comes to joining alloys because as we have said, alloys can be composed of different elements and this characteristic is what makes them not easily weldable with some forms of alloy fillers or electrodes.
Trying to weld alloys using unmatched fillers can result in a weak integration of joints. This is why when welding alloys, welders ensure that the electrodes or fillers they are using match the chemical composition of the base metal they are welding.
How Two Alloys Could Be Incompatible
There several reasons why two different alloys could be incompatible and cannot be welded together. It could be that they have different melting points which means the other alloy has a high resistance to heat while the other alloy melts easily.
Or they have different brittle phase formation which makes the other alloy to crack after a series of welding. Another reason is their corrosion factors which means one of the alloys oxidizes and corrodes easily with heat than the other.
So going back to the question, is welding alloys with different compositions still possible? The answer is yes, this could still be possible but only on given criteria.
If you happen to recognize the type of alloys you have to deal with so that you’ll know the type of alloy electrodes you need to use, you may still be able to weld incompatible alloys though there is no assurance of quality weld.
However, in some cases when you know there is a total non-weldability between two different metals you want to weld, better abandon the idea of welding them altogether because welding unmatched alloys can produce weak welding joints and may even create toxic fumes during welding due to the burning of alloying compounds.
Yes, it’s still your option if you want to experiment on using different alloy welding materials to get the desired strength of your welding joints but this could mean a lot of experimentation.
Welding Aluminum Alloys – How It Could Be Possible
Aluminium is a kind of alloy that is highly malleable and ductile and possesses high thermal and electrical conductivity. It is classified into two categories – heat treatable and non-heat treatable and this is also the problem with welding aluminium alloys because not all kinds of aluminium alloys can be easily welded.
Aluminium alloys are universally identified by their four-digit numbering system so each type of alloy has its own properties and weldability.
For example, aluminium alloy 3003 has only 1.2% Manganese added but has excellent weldability. Aluminium alloy 6061 has added elements of 0.25% copper, 0.6% silicon, 1.0 Magnesium, and .25% Chromium and earns itself a good weldability characteristic.
On the one hand, aluminium alloy 2024 has an added 4.5% copper, 1.5% Magnesium, and .6% Manganese thus earning the highest percentage of mixed elements which renders it a poor choice for weldability.
So if you have observed, the more elements that an alloy is composed of and the higher percentage of these elements, the poorer its welding capability can become. Likewise, the lesser the elements added to the alloy, the better the results when subjecting it to welding aluminium alloys.
Metals Suitable and Not Suitable for Alloy Welding
We now realized that welding alloys especially aluminium alloys is not a simple task to accomplish considering that aluminium is soft, insulated and can compose of many elements that could make or break your welding work.
Remember that alloys are categorized into families with four digits identification so here is the reference about the families of metal alloys with the right choice of alloy electrodes for their compatibility –
- 1000 alloys – These are 99% aluminum and only 1% of trace elements. This type of alloy is used for corrosion resistance and in carrying electrical current and can be weldable by 1100 types of filler metal.
- 2000 alloys – These are composed of high-strength aerospace alloys but highly sensitive to heat and cracking. The best filler materials for these are the 2319 and the 4043 fillers.
- 3000 alloys – These are composed of medium-strength aluminium alloys which are used for air conditioners and weldable by 4043 and 5356 filler metals.
- 4000 alloys – These alloys can both be used as filler alloys or base metals and can be welded with 4043 filler metal.
- 5000 alloys – Consist mostly of plate alloys and high-strength sheet, this series can be readily welded by 5356 filler metal.
- 6000 alloys – Composed of brittle alloys, these alloys can be prone to cracking unless welding them using 4043 or 5356 filler metals.
- 7000 alloys – These are also composed of high-tensile strength aerospace alloys that are generally unweldable because of their weakness in hot-cracking and corrosion due to stress. Except for 7003, 7005 and 7039, these are compatible with 5356 filler alloy.
Things to Remember With Aluminium Welding
You don’t have to be a metallurgist to know the right kind of alloy filler for your aluminium alloy. If you need to weld aluminium, you can choose the aluminium MIG wire with either the 4043 or the 5356 numbers.
The 4043 is the most popular wire electrode for joining aluminium or any kind of alloys and mostly recommended by MIG welder consumable sellers. The 5356 MIG wire, however, is stiffer and tends to go out from the contact tip of the MIG gun more smoothly.
Another tip I could give you about alloy welding is when, for example, your aluminium wire is .030 diameter, you could go for a bit larger contact tip for your MIG torch like .035 because when aluminum wire expands, this could cause bird caging or jamming of the wire inside the liner if your contact tip is of the same size with your wire.
Also, you may prefer using 100 percent argon for shielding gas which could be perfect in stabilizing the welding pool of the aluminum electrode. You may also want to preheat the aluminum metal base to prevent the formation of bubbles or pores prior to welding.
And this is how you do welding aluminium alloys without the need for much trials.
If you are a beginner welder, it is normal to try to fuse incompatible metals to see if it would work. By experimenting you will learn later on how to choose the right alloy fillers for certain types of alloy metals. Some welders choose stronger alloys as fillers with a combination of aluminum bronze or nickel bronze and sometimes this works with incompatible alloys.
So the point here is, make sure that when welding incompatible metals or alloys, you have to check the properties of the base metals first before choosing your welding alloys to avoid welding defects. Or, I should say it again, try to weld using a variety of alloy electrodes until you get the desired strength of your welding.
To help you out, you can also watch videos about alloy welding and watch the experts how they deal with fusing alloys using techniques and to teach you in choosing the right alloy electrodes for certain types of alloys or metals.