As we all know, welding is a highly versatile technique and there are a lot of types of forms in which you can perform the task. The variations in welding are usually caused by different types of metals that you would come across during a routine welding job. So, you will always have a suitable welding method that will offer satisfying results according to the type of metal you are working on as well as the type of joint you wish to create.
There is a subcategory of metals called white metals, which are known to be considerably hard to weld. Today, we are going to take a deeper dive into the concept of white metals and the most efficient way to weld them. In this guide, we will explain white metals, their properties, their welding method, and some important aspects that can alter the quality of white welding. So, make sure you stay in touch until the end of this guide.
What Are White Metals?
White metals have gained their nomenclature from appearance since most white metals are light-colored alloys of metal. And as a result, white metals are widely used for many applications where appearance is important such as utensils, silverware, or many other types of decorative metal objects.
White metals are basically metal alloys where Zinc plays an important role in the composition along with some other elements such as Copper, Tin, Magnesium, etc. Aluminum alloys also fall under white metals category. However, there are few properties that make Aluminum a preferred choice such as higher temperature resistance and stronger physical properties.
Based on the primary element used in the composition of the alloy, white metals are classified into 3 subcategories, Magnesium alloys being one of them. Another important characteristic of white metals is that they have a pretty low melting point. For example, a white metal Zinc-based alloy can offer as low as 725°F melting point.
Why White Metals Are Preferred?
Apart from Aluminum, Copper, and Magnesium, white metals are also formed by adding some other distinct elements into the alloy composition, such as Antimony, Cadmium, Lead, Tin, etc. However, most of these results turn out to be toxic once they come in contact with atmospheric air. Thus, the applications of such alloys are comparatively limited.
However, white metals that are based on Magnesium, Zinc, and Aluminum are quite common. By adding some other elements into the composition, the toxicity of the alloy can be completely eliminated, offering a wide range of beneficial properties.
The most preferred white metals are the ones that are based on Zinc. There are several reasons for choosing Zinc-based white metals for applications such as low melting point and overall low temperature of the element. Even within that, there are few variations such as Cast Rolled Zinc or Cast Zinc that are preferred for white metals. And to further improve white metal’s physical properties, there are other elements added to the mix, such as Silicon, Manganese. These elements along with Zinc are also added to Aluminum alloys to achieve desired properties.
Important Characteristics Of White Metals
Now that you know that white metals are highly preferred for a wide range of applications, let us try to understand the properties for which these metals are so popular. There are few qualities of white metals such as increased material softness and high ductility, which improves its range of applications. On top of that, the internal structure of white metals is hard and brittle, making the topmost surface resistant to external wear and tear.
Here are some important qualities that you should know before you deal with white metals.
- White metals may be considerably fragile at room temperature. But, it can be heated to increase the mechanical properties.
- White metals are lightweight compared to other alloys.
- Wear resistance is one of the most important qualities of white metal.
- White metals offer a low melting point, but still manage to keep high thermal as well as electrical conductivity.
- White metals have a low coefficient of friction.
- White metal may appear rigid from the outside, but they are highly ductile.
Welding of White Metals
White metals might have a lot of benefits, including affordability and effectively lower operating costs, but it is quite difficult to weld white metals. Since the internal structure is pretty fragile and they have a low melting point, it is nothing short of a challenge to weld white metals with a strong and reliable joint. Since Zinc or Aluminum have a higher percentage in the composition of white metals, we can simply treat them as Zinc or Aluminium while welding them.
In comparison, Aluminum-based white metals are a bit simpler to weld compared to Zinc-based variants. Therefore, there are a lot of factors that need to be considered before selecting the best process and parameters for the job. So, we have gathered some important things that you can consider before welding on a white metal. These factors include some basic parameters such as selection of welding rod or flame management along with some important parameters such as suitable welding technique.
But before that, make sure that the surface which is to be welded is clean and beveled before you start the process. It will simply increase the chances of creating a strong joint without damaging the rest of the surface. Also, it is important to introduce epoxy resins to the cracks in the white metals.
Factors That Affect White Welding
1. Proper Flame Control
One of the first things that you should do is create a carburizing or reducing flame before you start working with white metal. As you may already know, there are 3 types of welding flames that are carburizing, oxidizing, and neutral. Out of the 3, carburizing flame offers the lowest temperature levels, about 5252°F which is nearly 700°F less than an oxidizing welding flame. Such temperature would be perfect for welding on white metals due to their low melting point. It is also recommended to use a small-tip welding gun while working with white metals to keep the heat restricted to the weld bead. The best option would be soldering at a low-temperature, or using a superalloy for welding.
2. Selection of Welding Rod
While working with a welding rod, make sure you choose the right one while working with white metals. There are special welding rods available on the market that are purely made of Zinc. And if you want to ensure the best welding result as per the composition of the white metal you are working with, you can use a die-casting process to create a welding rod of identical composition. The best composition for a welding rod would be 50% Zinc chloride, Ammonium chloride, and a little bit of welding flux. Some welding rod suppliers also offer such options which is worth looking into before spending a serious amount of time and effort into the die-casting process for a welding rod.
3. Welding Technique
Since welding is somewhat problematic with white metals, the best method for the majority of welders is simply trial and error. In such a case, a welder would simply go with the welding method available at their expense and hope for the best. You can imagine how that can be an ineffective methodology, and can potentially cost damage to raw material. Because of the low melting point of the element, a lot of users prefer metal repair kits or creating castings since the white metal is pretty cheap.
As for creating castings with white metal, it is ideal to heat the workpiece, converting the base metal into liquid form. As for the flame, it should be kept parallel to the welding surface. This way, you can keep the temperature of the base metal equal to that of the welding rod for best results. With that, the metal will not over-harden after the welding is performed.
What Is Resistance Welding?
In resistance welding, the metal workpieces are joined together by applying pressure from both sides, and then passing current for a long time through the joint. While the process might appear lengthy and tedious, it creates reliable results when it comes to white metals. It also reduces the need of any type of additive such as welding flux for the welding rod needed for the job.
Unlike gas or arc welding, resistance welding is probably the best option for welding white metals. Resistance welding requires a lot less heat and is best suited for white metals such as Cast Zinc or Rolled Zinc. A great example would be spot welding since it also does not generate excessive heat. However, it is only applicable for creating lap joints and works with thin sheets of metal. There are many other forms of resistance welding such as seam welding, projection welding, upset welding, etc. that differ on the basis of type of electrode used for the process and also the shape of said electrodes.
Applications For Resistance Welding
As we just saw, resistance welding is a great option for welding on white metals. So, you can call it to be one of the most popular welding technologies for working with brittle materials to create aesthetically attractive and intricate objects. It also has a wide range of applications in the aerospace and automotive industry. Since resistance welding can be easily automated as there is little to no manual skill required, it becomes an ideal candidate for mass production industries.
Conclusion
We hope that you have understood white metals, their characteristics, and suitable welding methods for white metals from our guide today. Since white metals are so much cheaper and offer such a wide range of benefits, they are widely used in many different applications. Though, some physical and chemical properties make them problematic for welding. Therefore, welding or repairing a white metal object can be a challenge. But by considering all of the facts that are specified on this guide, you can easily weld white metals using one of the resistance welding techniques. If you need any more info, make sure you reach us via the comment section below.
