Typically speaking, Silver soldering offers a semi-permanent type of joint that can easily withstand bending, twisting. It won’t break down while doing regular tasks. Technically speaking, it has a tensile strength ranging from 40,000 to 70,000 psi (pounds per square inch). It means you can put on average 50,000 pound weight on a 1 inch x 1 inch silver solder joint and it won’t break.
Silver solder joins pieces of metal semi-permanently. The process uses heat like welding and brazing. The ideal joinery involves offering the joints tensile strength, which welding does best. However, if you want to solder and get the same results, use silver soldering. Silver solder offers strong tensile strengths similar to welds.
Of course, the technique is equally important as strength. Use the best joinery techniques and know the silver properties to add to your alloy for better joints. In some cases, silver soldering is known as silver brazing. For silver solder, you need flux to clean the metal surfaces during the soldering process.
Why do we use silver?
To lower the melting point of other alloys like copper
Common silver solders have 33%, 40%, and 55% of silver. Consequently, the melting temperature is significantly lower, with the higher silver component alloys having the lowest temperature, i.e., 1328, 1247, and 1202 degrees Celsius, respectively.
The lower melting temperatures enable you to solder your metal piece without risking the melting of joining parts. As much as phosphorous can do the same, silver is better because it gives you more control of the temperature.
Silver increases the melting temperature range
Silver allows you a range of melting temperatures making your work easier. Most alloys melt slowly, so if you have a range of melting temperatures, you can quickly braze the joining pieces inside that temperature range.
Adding silver lowers alloy ductility. The ductility reduces without affecting the melting point of the alloy.
Types of solder based on alloy composition
Based on alloy composition, solders are in four groups discussed below.
Lead alloy solders
These solders have lead to achieve the needed tensile strength and melting point. These solders are commonly called soft solders, and the most common solder comprises tin in a tin/lead ratio of 60/40. The solder has 180-1900 degrees Celsius melting points. Tin is used chiefly because it has a low melting temperature, and the alloy increases the shear and tensile strength of the joint. Lead is added to the mixture to curb the development of tin bristles.
The solder has no lead and has a higher melting temperature than the previous option. Countries like the USA offer tax benefits for those who use lead-free solders. The reason is to curb lead poisoning, which is an environmental hazard and harmful to human health. Also, there are incentives to solder manufacturers of this type of solder. Nowadays, most manufacturers use nickel as an additive. Also, they use confirming coatings to eliminate whiskers.
They come as wires wound on a cylindrical device. These solders have a reducing agent in the core. As you solder, the flux comes off, removing the oxides on the pieces of metal. It leaves you with a clean metal surface for working.
They are usually lead-based or lead-free. Silver was included as an additive to prevent silver migration. The silver solders are comprised of lead, silver, and other alloys in different ratios. The ratios affect the cost of silver alloy solders.
Type of solders based form factor
Silver solder joins most pieces of metal, including stainless steel, cast iron, mild steel, brass, copper, and dissimilar metals. The heat melts the silver solder to fill the gap in the joining pieces of metal. Primarily, silver solder is used in silversmithing and jewelry making. Also, you can join gold, brass, or gilding metals.
Bare wire or fluxless solder
This is the most preferred type. You can use the bare wire with a flux or powder flux by coating the powder on the bare wire, then warm the ends gently using your flame. Dip it in the powder. You can do this process repeatedly as you solder.
A preferred choice for some people. However, these flux-coated wires have three disadvantages. The wires are more expensive compared to bare wires. Besides, the wires need more flux powder. If you have bent wires, your flux powder easily falls off, which is frustrating.
These are only for silver brazing. The wires are more expensive than the last two. Silver brazing here works better if your wires are bent.
Types of solders based on core style
Solders are not just classified by alloy composition; core style matters too. Below are the different solder types.
Acid core solder
This is whereby the solder comes as a wired wound around a hollow core. Mostly, the hollow core is made of acid-based flux.
The acid-based flux is both strong and aggressive. It is very effective in getting rid of metal oxides and prevents further oxidation after the removal. As a result, you get strong solder joints that are unbreakable.
This solder is primarily used in joining stainless steel, mild steel, and other metals. However, clean off the flux residue when finished to prevent corrosion. Also, the solder is used in plumbing applications to join copper pipes and other metal sheets.
Rosin core solder
It also has a hollow core in the soldering wire. However, it differs from acid-core solder in that it uses rosin made mild flux. The residue doesn’t bring corrosion which is another plus. Mainly, rosin core solder is used in electrical appliances because the residue doesn’t come off in those connections.
This solder has a solid wire having the solder alloy, unlike the previous two, which have a hollow core. However, solid-core solder doesn’t have flux, meaning you have to apply flux when using the solder separately.
Grades of silver solder
Silver solder comes in four main grades; easy, extra-easy, medium, and hard. All the grades are available in strip form but with different melting temperatures. Hard silver solder can sustain prolonged heating during joining, mainly because it has the highest melting temperature.
The melting temperatures are as follows; extra easy 655-710, easy 705-725, medium 720-765, and hard 745-780; the temperatures are degrees Celsius.
What is soldering flux?
Soldering flux is a cleaning solution used during joining before heating. No solder can run without flux, which makes it a crucial part of the soldering process. Most fluxes are in liquid forms, but some are in paste or powder form. Application is mainly done using a paintbrush.
After soldering, you can use the pickle, a special cleaning solution designed to remove dirt and oxides. If you are soldering jewelry, just dip it in the cleaning solution until the jewelry piece is clean.
How to Solder
Silver soldering process is similar to other soldering techniques. Observe safety and have strong torches to get a strong joint. Follow the steps below.
- Clean the pieces of metal and de-grease them using files. Use a wet rag, Emery, or dry paper to clean the surface.
- Position the metal surfaces closer to each other to ensure no space is left.
- Apply your flux gently to the joint before heating using the gas torch until it’s dry.
- Apply silver solder coils or pieces along the joint. Ensure your solder has no grease and is clean.
- Evenly heat the pieces of metal. Use a fine-gas torch and keep your flame moving even as you monitor as your metal pieces glow a dull red.
- Watch out for the silver flush. It means it’s time to remove your blowtorch because you have made a successful joint.
- Leave the joints to cool off before you can use your pickling solution to remove the oxides and other dirt.
- In case the joint is not a success, clean off the metal surfaces before repeating the process.
Understanding the soldering process allows you to form strong silver solder joints. Plus, you can use other tools to accomplish the same task and handle complex tasks. The key to successful soldering has a well-equipped workshop that can handle any project. This requires knowing the essential soldering tools and techniques that will be invaluable to your projects.
Frequently Asked Questions
No. Silver solder has about 45% silver and can be lead-free or lead alloy solder. Silver solder is highly effective and prevents silver migration. Plus, silver solder gives a stronger joint than when you use regular solder. However, you can’t use it to join metals with a lower melting temperature.
In most cases, there are oxides and flux residues after you finish soldering. Use a cleaning solution or pickle to remove those oxides from your finished joint. These oxides accumulate as you solder. Pickle solution is applied when cold or warm by immersing the metal in the solution until all oxides are gone.
Do your soldering on a working area with a heat-resistant surface. This ensures the intense heat is absorbed. If you don’t have this surface, construct one using nicks and heat-resistant sheets. Some people use charcoal, asbestos, or magnesia. The three are ideal for small soldering projects. For large soldering projects, you need to construct a soldering hearth that is well ventilated and observes safety guidelines.
Most welders use gas torches or blowtorch to heat the metals. Gas torches are portable and easy to use in confined spaces. Besides, the blowtorch gives hot flames that can heat the metal.
When buying silver solders, you will have to pick from four grades that are hard, medium, extra-easy, and easy. all of which are in strip form with different melting points.
Yes. Silver solders are brazing fillers. However, silver solders are more fluid, and the joints should overlap if you want a strong joint. Silver solder is simply silver brazing.
I recommend SSF-6 silver solder as it gives you stronger bonds with stronger tensile strength and better ductility. This silver solder high-strength gives you reliable and better soldering.
Picking a solder for your projects is a matter of the kind of joint you want.
Also, consider the pieces of metal you are dealing with and the joint strength. You can pick a fluxless silver solder and choose a flux that will give you better results.
Alternatively, you can opt for a silver solder with a better alloy composition to improve physical properties.
Silver solders give you increased metal joint strength but not as strong as those of welded joints. Silver has a visible impact on reducing alloy melting temperature, which is helpful in silver brazing.