Soldering stainless steel at home: solders, fluxes, video

Soldering stainless steel is a rather labor-intensive procedure, but it will not cause any special problems if you know all the features of its implementation. With significantly less labor, it is possible to solder stainless steel alloys that contain no more than 25% chromium and nickel. Moreover, soldering stainless steel with such a chemical composition allows you to obtain reliable connections of products from dissimilar metals, excluding alloys with magnesium and aluminum.

Solder repaired bicycle frame

Soldering stainless steel, which contains a significant amount of nickel, can be difficult. This is due to the fact that in such alloys, when heated to a temperature of 500–700°, carbide compounds appear. The intensity of the formation of such connections depends on the duration of heating, so soldering should be performed as quickly as possible.

To minimize the risk of the formation of carbide compounds in the stainless steel structure during soldering, titanium is added to the alloy composition, and after the joint is formed, the product is subjected to heat treatment. You should be very careful when soldering cold-worked stainless steels, the surface of which may become cracked under the influence of heated solder. To avoid such consequences, it is necessary to eliminate the load on the parts being connected during the soldering process. In addition, it is possible to pre-anneal the products being joined.

Use a gas torch for annealing.

The choice of solder with which to solder stainless steel is influenced by both the chemical composition of the alloy and the process conditions. So, if this process is carried out at high ambient humidity, then silver alloys should be used, which contain a small amount of nickel. Soldering in an oven, as well as in a relatively dry atmosphere, is performed using chromium-nickel and silver-manganese solders.

The most common type of flux used when soldering stainless steel is borax, applied to the future joint in the form of a paste or powder. Melting borax on the surface of the parts being joined contributes to uniform and most accurate heating of the area of the future seam to the required temperature - 850°. Only after the required heating temperature has been reached, which can be determined by the color change of the future joint to light red, is solder introduced into the joint between the parts.

The flux is applied in an even layer over the entire surface, which must first be cleaned.

After soldering is completed, flux residues are present at the joint, which are removed by washing with water or sandblasting. To perform this procedure, you cannot use nitric or hydrochloric acids, which, although they effectively clean the flux remaining on the surface of the parts, have a negative effect on both the base metal and the used solder.

How to do soldering at home

Problems such as joining stainless steel parts using soldering and soldering stainless steel to copper are often encountered at home. Products made of stainless steel have been actively used in everyday life for many years, therefore, when for some reason they become unusable, any home craftsman has a natural desire to repair them himself. It should be said right away that soldering stainless steel parts is not so difficult, the main thing is to strictly adhere to the technology, as well as stock up on the appropriate tools and consumables.

Master the soldering technique on simple connections, and then try working with more critical parts

Before you start soldering stainless steel, it is very advisable not only to study the theoretical material on this issue, but also to become more familiar with the rules for its implementation using training videos.

To solder stainless steel products, you will need the following tools and consumables:

a soldering iron powered by electricity with a power of at least 100 W;
special soldering acid, which will be used as a flux;
file or sandpaper;
solder, specially designed for joining steel parts, based on tin and lead;
cable made of steel;
metal tube.

Soldering materials and tools

When choosing a soldering iron for working with stainless steel, you should opt for a tool with a power of 100 W. Using a more powerful device to perform such work is simply not practical.

The process of soldering stainless steel parts is carried out according to the following algorithm.

First of all, it is necessary to thoroughly clean the area of the future connection, for which sandpaper or a file is used.
After preparing the surfaces of the parts to be joined, it is necessary to apply flux to them, which, as mentioned above, uses soldering acid. The main task of the flux is to ensure high-quality tinning of the parts to be joined.
After the surfaces of the parts to be joined are treated with flux, it is necessary to tinning them, which consists of applying a thin layer of solder consisting of tin and lead to them. If tinning was not successful the first time, then it is necessary to repeat this procedure, preheating the parts to be joined.
Even after heating the products and re-processing them with flux, tinning may not be successful - the solder will simply roll off the surface of the parts, rather than lie on them as a thin film. In this case, you need to use a brush with metal wires, which can be easily made from a tube and steel cable. Before using such a brush, it is also necessary to apply flux (soldering acid) to the surface of the parts and only then, heating the future joint with a soldering iron, clean it with a metal brush. This simple technique allows you to effectively clean the surface of a stainless steel from an oxide film, which, as a rule, is the main obstacle to high-quality tinning.
Once a thin layer of tin has been applied to the products to be joined, you can begin to solder them. This procedure is performed using a soldering iron and solder, which is used to fill the joint between the parts.

The most common mistakes

There are a number of mistakes that a person can make when carrying out work:

Solder may not adhere to the material due to poor cleaning of the work surface.
Contamination of the part with greasy fingers before applying flux.
Insufficient heating. Solder does not always have time to fill the seam for reliable bonding.

It is important to remember to clean the soldering iron tip.
It is advisable to refrain from using solders with a high percentage of lead. Soldering stainless steel is a difficult process, but it can be done. To successfully connect parts, you need to choose the right consumables and use high-quality tools.

Solder Types

Stainless steel products can be soldered with both soft solders made on the basis of tin and lead, and hard types of filler material, which includes more refractory metals.

Soft solder, due to the fact that it is based on tin, is a low-melting material characterized by high ductility and fluidity in the molten state. What is especially important when soldering stainless steel products is that it has good deoxidizing ability.

Properties of soft solders

More reliable connections both in production and at home can be achieved by soldering using hard solders. The metals from which they are made melt at a higher temperature than tin, which makes it possible to obtain reliable and durable connections with their help. Very often, materials of this type are produced on the basis of technical silver, which can contain up to 30% in their composition.

Main brands of silver solders

One of the popular types of hard solder is the HTS-528 material, which is successfully used for soldering not only stainless steel, but also copper, brass, bronze, nickel and other metals. Conveniently, it is produced in the form of a rod, the surface of which is already covered with a layer of flux. When working with such solder in a production environment or at home, you should keep in mind that its melting point is 760°.

HTS-528 solder is a rod coated with red flux. In addition to stainless steel, it is suitable for cast iron and non-ferrous metals

Soldering stainless steel with copper and brass | Soldering stainless steel pipes

Soldering stainless steel is a complex and time-consuming procedure. The fact is that a number of nickel-plated alloys can release carbides when heated to 500 degrees. The amount of release depends on the duration of the soldering process.

The resulting carbides negatively affect stainless steel elements, as they can destroy its anti-corrosion properties. In order to prevent their appearance during soldering of stainless steel, it is necessary to add titanium or carry out additional temperature treatment of the elements.

Soldering of stainless steel must be done after annealing, since when reacting with molten solder, the hardened steel elements may begin to crack.

Work technology

Soldering thin stainless steel has its own characteristics. So, it is necessary to choose solder for stainless parts based on a number of factors:

steel composition;
conditions of the soldering process.

Borax is used to process stainless steel. It should be applied to the seam in the form of a powder or paste. When soldering thin stainless steel, the borax begins to melt, and the rest of the material begins to heat up. As soon as the hot temperature is reached - 850 degrees, it is time to introduce solder.

After soldering is completed, it is necessary to remove any material adhering to the stainless steel. To do this, the part must be washed in water or subjected to sand blasting. Similar procedures are carried out during soldering of food-grade stainless steel. However, in this case it is necessary to exclude the use of hydrochloric or nitric acids. They can corrode the base metal or remain on the elements. Soldering food-grade stainless steel is a responsible process that is directly related to the health of people who will subsequently use the soldered product.

Flux preparation

When soldering stainless steel, you should be very careful about choosing a ready-made flux or the recipe for making it yourself. The classic flux composition, which can be prepared at home, includes the following components:

borax (70%);
boric acid (20%);
calcium fluoride (10%).

For soldering small-sized products, you can prepare a flux that will consist only of borax and boric acid mixed in equal proportions. Having mixed the components of the flux in dry form, it must be diluted with water and treated with the resulting solution at the site of the future connection.

Useful tips

To perform stainless steel soldering efficiently, you should use the recommendations of experienced specialists.

The power of a soldering iron, which must effectively heat the metal being joined, is in the range of 60–100 W, but it is better to opt for a 100-watt device. To solder large parts, such as stainless steel pipes, you will need a gas torch rather than an electric soldering iron.
When choosing an electric soldering iron, it is better to opt for models equipped with tips that do not burn.
The most economical and universal type of solder, which makes it possible to obtain high-quality connections for stainless steel products, is tin-lead rods. If you are soldering dishes that will come into contact with food or liquids, it is better to use pure tin as solder, which does not contain harmful impurities.
The room in which soldering work is carried out must be well ventilated.
When performing soldering, be sure to use personal protective equipment so as not to harm your health.

What else you should know about soldering stainless steel

In cases where special requirements are imposed on soldered joints of stainless steel products, special grades of solders can be used, which include materials based on nickel and phosphorus, as well as nickel, chromium and manganese. Solders of the second group are used, in particular, in cases where soldering is performed in a protective gas environment consisting of a mixture of argon and boron trifluoride. When performing soldering using this technology, pure copper can be used as solder, which wets the metal well and forms a reliable connection.

When using copper solder, the soldering area will differ from stainless steel in a characteristic yellow color

Nickel-based solders make it possible to obtain joints with high strength. However, such materials also have disadvantages, which include low ductility. That is why such filler material is not used to connect stainless steel structural elements that will be subject to shock and vibration loads during their operation. In addition, a soldered seam made of such a material is very critical to low temperatures. Soldering with nickel group solders, which melt at temperatures exceeding 1000°, can be performed in dry hydrogen, argon and vacuum.

Thus, soldering stainless steel products (large pipes operated under pressure, dishes, pieces of furniture or interior design) has its own nuances, which must be taken into account when choosing both soldering modes and consumables. There are many reference books, guided by which, you can optimally select all the necessary materials and obtain a high-quality, reliable and beautiful soldered connection.

Connection with other metals

The connection of two different metals, for example, the soldering of copper and stainless steel, must be approached from the position of studying their properties. Metals have different melting points, so the soldering process is considered one of the most difficult.

Joining copper and stainless steel at home includes processing the workpieces, tinning the edges and the soldering process itself.