When it is necessary to reliably fasten various solid compounds together, then soldering is most often chosen for this. This process is widespread in many areas of industry. We have to solder and home masters.
This operation helps not only when the TV or computer fails, and to restore it is necessary to replace a burned-out microcircuit or chip. Using this process, refrigeration equipment and industrial systems are restored. Soldering helps in the event that it is necessary to obtain a tight connection. In addition, some materials simply cannot be combined in any other way.
Aluminum, copper, brass cannot be joined by welding. In order to get a high-quality and reliable, as well as a tight connection, you need to have not only good equipment and special skills, but also suitable consumables - solders and
fluxes for soldering.Alloys of solders and types of flux are chosen depending on the materials with which you have to work. For example, when working with aluminum products, a different flux is needed, different from what is suitable for copper or silver. Below we will consider the main characteristics of each of them and choose the most optimal option for work.
Solder for soldering: main characteristics
As it is used, various metal alloys. There are also compounds based on pure metal. In order to be able to create high-quality compounds with the help of one or another solder, these materials must differ in some qualities.
Wettability
First of all, any type of solder should have excellent wettability. Without this feature, soldered parts simply cannot reliably contact each other. What is wettability? This is such an interesting phenomenon when the strength of the bonds between the particles of a solid substance and a liquid is higher than that of a liquid molecule. If there is wettability, then the liquid spreads over the surface and enters all cavities. So, if the solder for soldering does not wet, for example, copper, then it can not be used with this metal. Pure lead is not used for soldering. Its wetting characteristics are very low and one cannot count on a high quality compound.
Melting temperature
Whatever the type of solder, the temperature at which it begins to melt must necessarily be lower than the melting of the soldered materials. It should also be higher than the operating temperatures of the parts.
Speaking about the melting point, they mean two points. This is the value at which the low-melting components begin the melting process, and the minimum, where the alloy turns into a liquid. The difference in these two temperatures is called the crystallization interval. If the place of soldering is within this difference, then even small mechanical loads on the part can completely destroy the structure of the solder. In such a connection, high fragility and resistance will be noted. Remember the main thing: do not in any way act on the connection until the solder for soldering is not completely crystallized.
Important properties of solders
Whatever the type and type of alloy, with whatever material it is used, it should not contain heavy metals or any other toxic substances above the established norm. The composition of the solder maximally matches the material of the parts. Otherwise, you will not be able to get a reliable connection. Excessive fragility will be observed.
Any solder, regardless of type and purpose, should be thermostable. Also, the solder for soldering should have electrical stability. The coefficients of thermal expansion and thermal conductivity should be taken into account. They should not differ significantly from those values that apply to soldered products.
Types of solders for soldering
All existing alloys for this operation are divided into soft, or fusible, where the melting temperature is up to 450 degrees Celsius, and hard. Here it significantly exceeds the above value.
Soft solders
Tin-lead alloys with different component contents are considered one of the most popular and widespread. In order to give the material the necessary characteristics, various additional ingredients can be added to the solder for soldering. For example, bismuth and cadmium are used to lower the melting point. Adding antimony allows you to increase the strength of the soldered seam.
Lead and tin alloys are characterized by a low melting point and low strength. They should not be used for parts whose operation involves a serious load. Also, these solders are not recommended if the working temperatures of the parts are above 100 ° C. If you have to solder the loaded parts with soft solders, you should try to increase the contact area of the two products.
Among the most popular soft materials can be identified POS-18, POS-30, POS-40, POS-61, POS-90. The numbers here are for a reason. This is the percentage of tin in the alloy. In industry, it is more often used in the manufacture of electronics, instrument making. In everyday life, they can combine a variety of details: circuitry for televisions, microwave ovens, electric kettles and other small appliances.
The appointment of soft solders
POS-90 is designed to work with parts that will then be processed using galvanic technology. POS-61 can be used to repair high-precision equipment. Also, the alloy is ideal for connecting parts of high responsibility from a variety of materials. POS-61 has proven itself as a solder for brazing copper and brass. Solder is suitable when it is necessary to achieve strong joints with a high degree of electrical conductivity.
POS-40 is widely used for operations with irresponsible and inaccurate parts. In this case, the working area can be heated to high temperatures. POS-30 is suitable for soldering copper or brass, steel alloys and iron.
Solid
Among refractory alloys, only two groups are distinguished and widely used. These are mainly copper or silver alloys.
The first group includes solders made of copper and zinc. They are well suited for those connections that will only be affected by static loads. The fragility of these alloys does not allow them to be used in nodes that will experience shock or any vibration.
The solders made of copper or zinc-based compounds include PMC-36 and PMC-54. The first is the perfect solder for brazing brass and any other copper compounds. The second is suitable for working on copper parts, bronze or steel.
If it is necessary to connect two steel parts together, then you can use pure copper, brass grades L-62, L-62, L-68. These brass based solders allow you to create more durable and ductile joints. Copper alloys do not have such characteristics.
Silver alloys are considered the highest quality. It may also contain zinc and copper. PSR-70 - solder for brazing copper, for working with brass or silver parts. This element is suitable if the junction should conduct electricity. PSR-65 is used in the manufacture of jewelry, fittings, water pipes. PSR-45 is necessary for connecting those parts that work under conditions of vibration and shock loads.
Other species
There are other, less popular solders. Often they are used for rare metals or for work in special conditions. For example, nickel-based formulations are intended for products that operate at elevated temperatures. They also solder stainless alloys. Gold based solders are used for working with vacuum tubes. There are appropriate solders for magnesium.
Release form
Soldering materials and compositions are available in a variety of forms. So, it can be wire, thin foil, tablets, powder. In addition, solder is available in the form of paste or granules. How the solder will be delivered to the work area depends on the shape.
Features of aluminum brazing
The connection of aluminum parts by soldering is used in industry and in everyday life. For example, the frames of modern bicycles are made of aluminum alloys - during extreme riding, they often break. The question arises: what solder to choose?
It is believed that brazing aluminum is a very complex process. But in fact this is so if the process uses materials for stainless steel or brass, steel, copper. The reason for this is the oxide film. It does not give the necessary level of wettability, and the base metal does not dissolve.
How to solder aluminum and alloys based on it
In order for the work to be carried out at the proper level, the aluminum solder must contain silicon, aluminum, as well as copper, zinc and silver. Today on sale you can find compounds where all these components are in different proportions.
When choosing a reliable solder, it is important to consider the following. The maximum resistance to corrosion and high strength will have the connection that was made with solder, which contains a lot of zinc.
Also for aluminum, compounds based on tin and lead can be used. But it is important to qualitatively prepare the work surface, brush it with a stainless steel brush and use active fluxes. But experts do not recommend using such an element.
Any high temperature aluminum solder. The most optimal, which allow to obtain a reliable connection, are aluminum-silicon and aluminum-copper-silicon.
How to solder copper?
As already noted above, it is possible to work with most of the compositions. You can use both low-temperature fusible and solid solders. Also used are compounds based on tin with lead, tin, silver, copper with silver and zinc.
If you need to repair the computer's motherboard or fix the TV in the country, any fusible elements will do. If it is necessary to solder the fittings on the pipes or repair the water supply or the refrigerator, then only solid solder for brazing copper will do. This is how you can get a quality result.
Stainless steel
If it is necessary to connect stainless steel parts, then professionals recommend using tin and lead rods. Cadmium materials are also well suited. It is possible to use low-melting alloys based on zinc. However, they should not be used together with carbon or low alloy steels. The best solder for brazing stainless steel is a composition based on pure tin. In addition, only tin is allowed if the soldering point is in contact with food.
If the work will be carried out in a dry or furnace atmosphere, then silver with manganese, chromium-nickel solders or pure copper (and even better brass) should be used. When it is necessary to solder under corrosive conditions, silver tinols with a small part of nickel are used.
Soldering steel
It is not difficult to connect two such parts together. Affordable and effective solder for steel brazing - POS-41. There is also POS-60 and others, you can even use pure tin. But zinc compounds do not work well. Especially when it comes to carbon or low alloy materials.
Soldering fluxes
During the operation, flux plays no less role than solder. It is a chemical solvent and an absorber of oxides. It also protects metals from oxidation and increases wetting.
To work with elements based on lead and tin, hydrochloric acid and zinc chloride can be used as a flux. Borax, ammonium chloride, is also suitable. These are active fluxes. Inactive include rosin, petroleum jelly, olive oil and many other substances.
For example, hydrochloric acid solutions can be used with soft solders. Zinc chloride is used with brass, copper, steel. Ammonia sleep perfectly dilutes and dissolves fatty substances. For aluminum, a composition of tung oil, rosin, calcined zinc chloride is used. Concentrated phosphoric acid may also be used.
So, we found out what solders exist, and which one is better to use in different cases.