Today, with manufacturers trying to create lighter and more durable products, the use of aluminium and aluminium welding is becoming quite predominant. And, usually, in the case of aluminium welding, the selection of the alloy as the filler is between 5356 and 4043. More than 75%-80% of aluminium welding jobs make use of one of these two alloys. The choice of the filler essentially depends on the material of the base that is being welded and the electrode properties. And, appreciating the difference can help to decide which is right for the job and if any other option is more well-suited.
The main advantage is that the crack resistance of 4043 is high and it is more suitable for welding metals that are sensitive to cracking. This is because it has a narrow freezing range and the because it is close to the eutectic temperature, where the 4043 changes from a solid to a liquid directly, it is ideal. The capillary action and fluidity of the 4043 make it more suitable for the purpose of sealing components, which is why it is used in the welding of heat exchangers. However, for some applications, 5356 is more well-suited.
Another benefit of using 4043 for welding is that the finish produced is significantly brighter and there is much lesser of sooting, which are the black lines that are seen on the edging when 5356 is used for welding. The lack of sooting allows reduced after-welding clean-up.
A drawback of using 4043 for welding is that there may be a problem with the matching of the colour between the metal and the weld. This is especially a problem if the workpiece needs anodizing after welding, as the weld turns black while anodizing if 4043 is used.
A major drawback of making use of 4043 is its high conductivity. When the electrical conductivity of the electrode is very high, it requires a higher amperage in order to burn the same length of wire. This results in the higher input of heat, which makes it quite difficult to weld thinner materials. However, 5356 allows you to achieve greater speeds of wire feed, which results in greater weld laid per hour and also the throughput. With 5356, the welding is comparatively faster and also the back of the workpiece will not get burnt through.
Ductility and Strength
4043 has low ductility and is not very strong and not really recommended for the purpose of welding. Since the 4043 is not very strong, it is difficult to feed it through the welding systems, as it becomes very soft and may fold up inside the liner of the gun. 5356 on the other hand, is smpler to feed, as the column strength of the 5356 is much higher.
4043 is extremely effective when it comes to high-temperature applications involving 150oF or higher temperatures. However, this essentially depends on the alloy of the base. Usually, when using aluminium/magnesium alloys of the 5000 series, if the content of magnesium is more than 3%, there may be a problem of stress corrosion cracking. In such cases, using 5554 is ideal, as it has a very low magnesium content and does not crack.
However, there are some applications such as welding 5083, a high strength alloy, which requires some other filler instead of 5356 or 4043, as it requires a filler metal that is stronger and you could consider high-strength options such as 5183, 5556 or 5556A.
Nevertheless, for many jobs using 5356 and 4043 is ideal. And, you need to consider both in terms of the low conductivity and feed speed benefits of 5356 vis-à-vis the benefits of 4043 and determine the one that is best-suited for your job requirements.