Understanding the differences between types of aluminum fillers can help determine which aluminum filler is best for your job, or other options may be more appropriate.
Aluminum welding is becoming more common as manufacturers strive to create light and strong products. The choice of aluminum filler metal usually comes down to one of two alloys: 5356 or 4043. These two alloys account for 75% to 80% of aluminum welding. The choice between two or the other depends on the alloy of the base metal to be welded and the properties of the electrode itself. Knowing the difference between the two can help you determine which one works best for your job, or which one works best.
One advantage of 4043 steel is its high resistance to cracking, making it the best choice for crack-sensitive welds. The reason for this is that it is a more liquid weld metal with a very narrow solidification range. The freezing range is the temperature range in which the material is partly liquid and partly solid. Cracking is possible if there is a large temperature difference between the completely liquid and all solid lines. What’s good about 4043 is that it’s close to the eutectic temperature and doesn’t change much from solid to liquid.
The fluidity and capillary action of 4043 when welded makes it more suitable for sealing components. For example, heat exchangers are often welded from 4043 alloy for this reason.
Even if you are welding 6061 (a very common alloy), if you use too much heat and too much fusion in that base metal, the chances of it cracking are greatly increased, which is why 4043 is preferred in some cases. However, people often use 5356 to solder 6061. In this case it really depends on the conditions. Filler 5356 has other advantages that make it valuable for welding 6061.
Another major advantage of 4043 steel is that it gives a very bright surface and less soot, which is the black streak that you can see on the edge of the 5356 weld. This soot should not be on the weld, but you will see a matte line on sock and black stripe on the outside. It’s magnesium oxide. The 4043 cannot do this, which is very important if you are working on parts where you want to reduce post-weld cleaning.
Crack resistance and a lustrous finish are two of the main reasons to choose 4043 for a particular job.
However, color matching between weld and base metal can be a problem with 4043. This is a problem when the weld needs to be anodized after welding. If you use 4043 on a part, the weld will turn black after anodizing, which is usually not ideal.
One disadvantage of using 4043 is its high conductivity. If the electrode is highly conductive, it will take more current to burn the same amount of wire because there won’t be as much resistance built up to create the heat needed for welding. With the 5356, you can generally achieve higher wire feed speeds, which is good for productivity and wire laid per hour.
Because 4043 is more conductive, it takes more energy to burn the same amount of wire. This results in a higher heat input and hence difficulty in welding thin materials. If you’re working with thin materials and are having trouble, use the 5356 as it’s easier to get the right settings. You can solder faster and not burn through the back of the board.
Another disadvantage of using 4043 is its lower strength and ductility. Not generally recommended for welding, such as 2219, a 2000 series heat treatable copper alloy. Generally, if you are welding 2219 to yourself, you will want to use 2319, which will give you more strength.
The low strength of 4043 makes it difficult to feed material through welding systems. If you are considering a 0.035″ diameter 4043 electrode, you will have trouble feeding the wire because it is very soft and tends to bend around the gun barrel. Often people use push guns to solve this problem, but push guns are not recommended because the pushing action causes this bend.
In comparison, the 5356 column has higher strength and is easier to feed. This is where it has the advantage in many cases when welding alloys like 6061: you get faster feed rates, higher strength, and fewer feed problems.
High temperature applications, around 150 degrees Fahrenheit, are another area where 4043 is very effective.
However, this again depends on the composition of the base alloy. One problem that can be encountered with 5000 series aluminum-magnesium alloys is that if the magnesium content exceeds 3%, stress corrosion cracking can occur. Alloys such as 5083 baseplates are not normally used at high temperatures. The same goes for 5356 and 5183. Magnesium alloy substrates typically use 5052 soldered to itself. In this case, the magnesium content of 5554 is low enough that stress corrosion cracking does not occur. This is the most common filler metal welding machine when welders need the strength of the 5000 series. Less durable than typical welds, but still has the necessary strength for applications requiring temperatures above 150 degrees Fahrenheit.
Of course, in other applications, the third option is preferred over 4043 or 5356. For example, if you are welding something like 5083, which is a tougher magnesium alloy, you also want to use a tougher filler metal like 5556, 5183, or 5556A, which have high strength.
However, 4043 and 5356 are still widely used for many jobs. You will need to choose between the feed rate and low conductivity benefits of 5356 and the various benefits offered by 4043 to determine which is best for your job.
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