Last Updated on November 14, 2020 by Gary Hargrave
Metal joinery is an important part of the fabrication process where welding is often considered as the best course of action for its ability to produce the strongest and most efficient of all joints. But the use of electricity, need for skilled labor, and susceptibility to poor penetration, slag inclusion, and porosity bring other bonding methods into perspective.
Is there really another way to join more than one metal part while keeping up the strength and integrity of the bond? From what I’ve learned all these years, I would say there are six different ways to do that. However, each of these methods is subject to certain considerations.
In this article, I’ll discuss each bonding process covering their basics and enlighten you with details about their relative usability in comparison with welding. But let me tell you which things about welding tip the scale in favor of other choices.
Topics Covered in This Article
- Problems with Welding: Why Look For Another Way To Join Metal Without Welding
- 6 Most Effective Ways To Join Metal Without Welding
- 1. Brazing: The Most Relevant Alternative to Welding
- 2. Soldering: An Alternative to Brazing
- 3. Riveting: A Reliable Alternative to Welding
- 4. Adhesive Bonding: A New Approach to Join Metals
- 5. Mechanical Fastening: A Good Choice for Temporary Joints
- 6. Joining with Nanoparticles: An Innovation Underway
- Can Spot Welding Be an Option?
- Final Thoughts
Problems with Welding: Why Look For Another Way To Join Metal Without Welding
Before proceeding to learn how to bond metal to metal without welding, I think you should find out why you want to look beyond welding in the first place.
- Lack of filler materials in the right proportion and other factors may cause the joints to be brittle and lose fatigue strength.
- Uneven distribution of heat and cold temperatures across the metals being joined may cause distortion and extreme stress in the joints.
- Since welded joints get no provision for contraction or expansion which often occur with time and usage, racks are likely to appear.
- Inspecting welded joints is costlier and more difficult than the joints by other techniques.
6 Most Effective Ways To Join Metal Without Welding
Here is a list of different ways to join metal effectively without welding –
- Adhesive Bonding
- Mechanical Fastening
- Joining with Nanoparticles
I’ll start with brazing and then proceed with other methods which have some benefits over welding but not without their inevitable limitations.
1. Brazing: The Most Relevant Alternative to Welding
Compared with soldering, fastening, and other options for joining metal, welding and brazing are more effective when the joints are expected to be permanent and strong. Both methods are commercially viable, but they work differently.
Welders melt and fuse metals to join them adding a specific filler material. Concentrated heat is directly applied to the joint to achieve fusion as the temperatures rise above the melting point of both the filler in use and metals being joined. The strength of the joints either becomes equal to or greater than that of your base metals.
Brazing doesn’t involve melting or fusion. Temperatures during this process are lower than the base metal’s melting point. You can use the same base metal for both brazing and welding. Temperatures and energy requirements during the former are considerably lower than the latter’s.
How Brazing Works?
Brazing produces a metallurgical bond between your base metal surfaces and the filler metal. The base metals receive heat broadly and are brought into a direct contact with the filler material. As the filler contacts the heated parts, it gets instantly melted and then drawn through the joint by the capillary action. Thus, you get a brazed joint.
Advantages over Welding
There are several considerations that dictate the choice between these two methods. Let me explain each of those situations where brazing proves to be more viable than welding.
Metal sections that are 0.5 inch or thicker can be handled with almost equal efficiency by both methods. Thinner sections are better joined by brazing. Here is an example.
You want to adopt brazing when you’re working to create a T-joint bonding a piece of sheet metal to metal stock where the thickness of both pieces is 0.5 inch.
I don’t suggest welding in this particular case because the intense heat generated in the process may burn right through the thin section. Even if you are too careful to let that happen, you’ll still have worries about warping.
Brazing may not eliminate warping, distortion, and stress in the metal joint completely, but those defects are often minimal with the heat being distributed across a broad area. In addition, lower temperatures result in the use of less energy, which makes brazing an affordable choice.
In welding, one particular end of an interface is heated to a melting temperature. Then, the heat travels slowly along the line of the joint with the filler metal being deposited in synchronization.
In brazing, there is no need for manual tracing as the filler metal gets drawn into curved or straight joint configurations. It is possible to ensure the equal distribution of the filler material, no matter the irregularity in the joint structure.
Joints Between two Dissimilar Metals
Brazing ensures that the strength of the joint is greater than that of the metal parts. Temperatures can be anywhere from 1,150 to 1,600°F, but most of the physical properties of the joint remain unaffected.
Less alteration of the properties of the base metals means a stronger joint with the use of a filler material that has a lower melting point than the base metals and metallurgical compatibility with them.
Let’s put this into a comparative instance using copper and steel in the process. Welding melts both of these base metals. As you attempt to join copper with a melting point at 1,981°F to steel with a melting point at 2,500°F, you can’t do it without expensive and well-practiced techniques.
In addition, you can barely do anything to prevent the copper from melting before seeing that the steel has approached a welding temperature. Brazing lets you choose metals according to your requirements without worrying about the differences in their melting temperatures.
Automation and Manual Actions
Whether your job involves hundreds of assemblies or just a few, brazing allows you to choose between automation and manual ways. If the demand of production is low or moderate, you can get away with basic automation techniques.
However, manual welding is okay as long as your production volume is limited to a few assemblies. A higher volume means you’ll be looking at a more advanced and expensive setup for any level of automation. There is nothing ‘simple’ or ‘basic’ in this particular case.
Without being very good at welding, you can only expect something short of a regular bead profile. Brazing lets you get a small fillet that looks neat as well. So, brazing gives you an upper hand on jobs that require the appearance to be good. Brazed joints are also usable without any additional finishing task.
Despite the benefits brazing brings, welding becomes indispensable at times. I’m pointing out two of those circumstances when welding beats practically all methods including brazing.
Both methods are ideal for making spot joints, but welding uses localized heat which brings some advantages. For instance, you’ll benefit more from welding while joining metal strips at any single point. Electrical-resistance welding is arguably the fastest and most economical means to create strong and permanent joints by large volumes of strip joints.
For larger assemblies, welding is a better choice than brazing as it brings heat to the entirety of the base metals or at least a broad area. The tendency of larger metal assemblies to dissipate heat often prevents the heat from reaching the filler’s flow point. With improved efficiency to trace a metal joint, welding applies intense, localized heat to overcome this limitation.
Choice of Metals and Rods
To achieve the optimal results from brazing operations on different metals, you’ll need the following rods depending on the metal you want to join.
|Base Metals||Brazing Technique and Rods|
|Brass, Bronze, and Copper||Welding Rods, Copper Phosphorus|
|Mild Steel, Cast Iron, Stainless Steel, Copper, and Nickel Alloys, and Tungsten Carbide||Welding Rods, Nickel Silver Brazing|
|Galvanized Iron and Nickel||Welding Rods, Bronze Brazing|
|Aluminum||Welding Rods, Bernzomatic AL3 Brazing|
2. Soldering: An Alternative to Brazing
In soldering, two metal pieces are joined together using a third metal alloy, often softer with a lower melting point than those being joined. You can use an alloy of lead and tin which we call a soft solder or an alloy of zinc and copper which we call a silver or spelt solder.
How Soldering Works?
The solder is melted over the joint by the use of a soldering iron which is a piece of hot metal having a pointed tip. A heating element that relies on electricity generates heat inside the iron.
You need to clean the base metals’ surfaces thoroughly with a flux before joining them. Flux removes grease, oxides, or other contaminants from those surfaces and allows a solder to flow smoothly and unit those surfaces firmly. Workshops use acidic fluxes including acid paste, hydrochloric acid, zinc chloride, etc.
You may need to think of non-corrosive fluxes instead of acidic fluxes in applications like electrical projects due to the corrosive nature of those acidic elements. As this method bonds metals by melting certain filler materials into the joint, alloys that are free of lead are popular with people working in the electronics and plumbing industries.
Advantages over Welding
So, how soldering compares to welding? Principal differences lie in the heat requirements, metal thickness, and joint types.
Welding requires the temperatures to be 6500 ℉. You should provide some heat treatment. Also, you need a certain level of familiarity with the job. For soldering, the heat requirement is pretty low, only 840 ℉. You won’t need to worry about any kind of heat treatment. With just a few hours of practice, you can master the process.
Soldering is a popular practice in jewelry and plumbing businesses. While welding allows plumbers to create some of the strongest joints, soldering helps plumbers make some permanent yet reversible joints that are both waterproof and mechanically robust.
The biggest drawback that soldering involves is in the strength of the joint. You can expect strong joints but not as much as what welding ensures. You’ll take some cleaning actions before soldering. In addition, soldering is extremely limited to thin metals where welding works on both thick and thin metals.
Solder doesn’t make a mechanical bond between metals. So, you must create a solid mechanical bond before soldering on top. A soldered joint that fails to conduct electricity properly is a poor one.
Choice of Metals
Some metals come with better solderability than others. I’m putting a list here, so you can choose considering your flexibility and quality requirements.
- Most Suitable: Cadmium, Gold, Palladium, Rhodium, Silver, and Tin
- Good Solderability: Brass, Bronze, Beryllium Copper, Copper, Lead, and Nickel Silver
- Fairly Suitable: Carbon steel, Nickel, Zinc, and Low Alloy Steel
- Not Recommended: Aluminum Bronze, Cast Iron, Aluminum, Chromium, Stainless Steel, High Alloy Steel, Magnesium, and Titanium
3. Riveting: A Reliable Alternative to Welding
A rivet looks like a metal pin and is a better metal joint component than a typical mechanical fastener. A standard rivet has a head on one of its ends and a tail on another, which is basically a cylindrical stem.
How Riveting Works?
Riveting involves the drilling and punching of a rivet into a hole. The tail is then deformed through smashing or pounding while keeping the rivet in its place. Such actions flatten the material and expand the size of the tail by about 1.5 times its original diameter.
You’ll notice that the shape of the tail looks like a dumbbell as the riveted joint is created. You can follow this method to create butt or lap joints maintaining different configurations such as single or double formations, zigzag shapes, etc.
Advantages over Welding
It is a relatively safe way to join metals as you won’t be using any gas or getting exposed to fumes. Making riveted joints in flat, vertical, and overhead positions is easier than the welded ones. The composition of rivets comes from tough materials which result in little deformation of their structure.
The riveted parts suffer no thermal effects and very minimal damage as you take one apart from another. Quality inspection of riveted joints is easier and less expensive than that of welded parts. Even a beginner can get away with the rigors of the process with an hour of training.
Despite the many benefits of riveting, it is not without some serious limitations. Welding is a faster method and produces joints that are more aesthetically appealing than riveted parts. Modifying welded joints is significantly easier than riveted ones.
The hole you have to create may have stress concentration. To place a rivet, you’ll use a metal material which loses its original integrity in the process. All these factors may compromise the strength of the joint eventually.
When it comes to cylindrical shapes, welding makes it easier than riveting. You might have seen that welding is performed to make pipe joints. Moreover, riveting is not a silent process. So, keep your work away from places where there should be no noise.
Corrosion is one of the most annoying riveting issues which can be minimized by painting both base metals as the paint helps reduce the reaction between them. To improve the aesthetics of riveted parts, you can apply some coatings which also add to corrosion resistance.
Choice of Metals and Rivet Materials
Non-ferrous materials are ideal for being joined with rivets. Make sure the mechanical properties of the rivets you’re using are the same to those of the metals being joined. For instance, plastic rivets are recommended when soft materials will be joined.
Now, I’m presenting a table to show you which rivet materials work well for which metals. Note that the environment in which you’re performing this needs to be free from any form of extremities.
|Metal to Be Joined||Rivet Material|
|Brass and Copper, and Stainless Steel||Copper, Nickel Copper, and Stainless Steel|
|AluZinc Coated Steel||Aluminum and Steel ZP|
|Zinc-Coated Steel||Steel ZP|
4. Adhesive Bonding: A New Approach to Join Metals
Following this method, you actually take one step to bond and seal the metals. All you do is fasten the surfaces of two metals together producing a strong and smooth bond. Common bonding materials include epoxies, glues, or plastic agents.
How Adhesive Bonding Works?
These materials create bonds by evaporating a solvent or curing a specific bonding agent in the presence of pressure, time, and heat. Traditional glues used for this purpose were not very reliable in terms of the integrity and strength of the joints. The innovation of plastic-based agents or super glues has changed the perspective as they are manufactured to cure with the heat on their own and allow strong adhesion.
Epoxy glues are known for their excellent composition which helps form pretty strong joints. These special glues are quickly becoming safer choices in aerospace, automotive, structural, and a lot of other applications where metal joints are not frequently exposed to weathering or heat.
Advantages over Welding
In view of safety concerns, down time, and structural degradation or integrity, adhesive bonding or gluing offers some benefits and presents a few drawbacks too.
In this technique, stress concentration points in the joint can be reduced. Discoloration, distortion, corrosion, or other deformations are less likely even though thin or dissimilar metals with various shapes, dimensions, or masses are joined.
Since you won’t be performing any process that requires an extreme level of heat or other factors, the galvanized coatings on your base metals (if any) won’t be damaged. The appearance of the finished joints comes better with adhesive bonding that it does with welding.
Welding can be an ideal technique for high-volume production requirements, but adhesive bonding, if applied to the right metals, lets you make even a higher volume. You don’t have to take much of any cleanup action after the process.
This bonding technique distributes stress across the bonded area to increase the fatigue strength. Also, the joint design may change to properly accommodate the surface contact. Maybe, you’ve realized another benefit that this process doesn’t require you to have much training as you would have for welding.
The cure time required for a strong joint ranges from several minutes to a few hours. Depending on the applications, you may experience delays in the work process. Surface preparation might be required, and this is where you could use some training. Disassembly of the bonds or joints can be very challenging.
Adhesives don’t do their job very well in tension applications. It means your options can be limited to only those joints where adhesives are kept in compression. Also, avoid trying this while being in an atmosphere with high temperatures exceeding 150°F.
Choice of Adhesives
So far, the market has brought seven adhesive families to create bonds between two metal parts. Look at the table below.
|Adhesive Families||Characteristics of Joints||Limitations|
|Two-Part without Acrylics||Strength and durability with fast bonding||Low depth of cure|
|Two-Part with Acrylics||Durability and better depth of cure||Long cure time|
|Two-Part Epoxies||Durability, strong, excellent temperature resistance, and depth of cure||Long cure time|
|Polyurethanes||Toughness and flexibility||Slower cure than most other families|
|Cyanoacrylates||Excellent shear strength||Low depth of cure and peel strength|
|Light-Cure Acrylics||Fast and strong bonding||Extremely limited applications|
|Silicones||Excellent temperature resistance and retention of strength properties||Slow cure and poor cohesive strength|
5. Mechanical Fastening: A Good Choice for Temporary Joints
As a useful alternative to popular joining methods, fastening with a bolt or pin following a direct-tension technique is getting popular with the industry that manufactures heavy equipment and machinery.
How Mechanical Fastening Works?
A mechanical fastener fastens or joins two metals or objects together. These devices are designed to transmit mechanical loads keeping two or more parts of a metal assembly in a relative position. Its job is to ensure mechanical strength, stability, and continuity as required.
This joining method is carried out by two distinct types of processes such as integral joints and fasteners. Fasteners include bolts, nuts, pins, and screws. Crimps, seams, shrink-fits, and snap-fits fall into the category of integral joints.
Advantages over Welding
Unlike welding, this technique is ideal for any material regardless of the shape, but you need to use some ingenuity. Joining dissimilar metals also comes easy. You have virtually no better choices around where multiple parts are required to move in relation to each other.
You can achieve excellent joint quality with some operational skills. I think you might emphasize the non-permanence of some fasteners as one of the major drawbacks. This idea makes sense, but you’ll love the feature when you need to disassemble the joined metal parts for repairing or accessing their interior, especially if you ever need to check for corrosion.
Fasteners are usually installed at joints maintaining equal distances. It means each joint gets the same strength without undergoing any significant change. So, weight distribution occurs appropriately and equally. You can also adjust the devices to compensate for shrinking, swelling, or other changes in the joined materials without a laborious attempt.
Speaking of safety, you just need to take a few swaging actions which are almost free of jolts and noise. This flexibility helps you overcome the potential for issues like repetitive stress syndrome, sparks, explosions, debris, etc.
Finally, the economic advantages cannot be ignored when there is a need for mass production. In terms of the skill and time required for a successful operation, mechanical fastening beats welding by many a mile.
The strength of joints that welding provides is good enough to outperform just about any result you can expect from other methods including fastening. But it presents a few other limitations.
The potential for creating holes is one of the reasons you shouldn’t adopt this joining process for composites and ceramics. Moreover, fastening may reduce the fatigue life of objects being joined.
6. Joining with Nanoparticles: An Innovation Underway
Alloys used for soldering and other joining methods come with low melting points which make them susceptible to remelting at temperatures above their respective melting points. So, the joints created with them may break at some points.
Nanoparticles overcome the issues regarding melting points of those alloys. The melting points of some nanoparticles decrease with changes to their sizes. So, you can perform bonding metal to metal at low temperatures without the susceptibility I mentioned above.
How Nanomaterials Work?
The surfaces of the metals being joined need to be roughened by a specific etching technique using 3D printing and electro-chemicals. Doing this, you’ll get a hook-like structure on a very small scale. Then, the surfaces are joined using adhesive. The operation results in a solid bond.
In this fairly recent practice, copper and silver nanoparticles are the two most popular options where silver proves to be a more suitable choice than copper due to its excellent chemical stability and thermal & electrical conductivity. Copper nanoparticles are more affordable than their silver counterparts but they oxidize so pretty easily in air.
Advantages over Welding
Besides joining light components, nanomaterials can be used for large parts too, particularly the ones you need for shipbuilding and automotive applications.
After the bonding is finished, the nanoparticles turn into metal bulk with a higher melting point than that of the nanoparticles used. So, the joined metal parts do not become separated despite being used at a lower melting point.
Due to high temperatures being absent or unnecessary, this process doesn’t cause damages to metal surfaces. Thus, welding seems less advantageous than this process. Again, you don’t need to take a lot of safety precautions as you would while welding.
In terms of the strength and properties of joints, silver beats copper quite easily as the latter undergoes quick oxidation that weakens its properties. It means the joints won’t be quite as strong or concentrated as required.
With silver nanoparticles, you can make strong joints, but operating costs and ionic migration of atoms can be very high. Copper nanoparticles can be made suitable by enhancing their chemical stability which can be done by reducing the amount of oxide nanoparticles in an aqueous solution using stabilizers.
But then, you need to find a reducing atmosphere where oxidation is unlikely to occur. The presence of nitrogen and air doesn’t make your atmosphere bad, but all other gases will complicate the bonding process.
After all, I don’t think it is the first path you want to take in an attempt to bond objects for there are lots of questions which even experts are still seeking answers to. More importantly, the bonds don’t work very well for various metals including the ones frequently required by professionals and fabrication workshops.
Can Spot Welding Be an Option?
Spot welding requires electric resistance instead of an electric arc to make metal joints. This process applies heat and pressure obtained from a current flow to the welding area. So yes, it can be an alternative to arc welding, but I am afraid you won’t be able to avoid welding completely.
Guess what I’ve missed. That is the entirety of what I believe should be enough for you to get started. However, I’ll recap the key distinctions between welding and the other ways for you.
Brazing is preferable to welding for variable joint configurations, thinner or dissimilar materials, small assemblies, and projects involving the need for flexibility, minimal distortion, warping, and stress.
Without any heat treatment, soldering comes handy as you want to tackle jewelry projects or a plumbing assemblies which require mechanically strong yet reversible joints for a prolonged period of time.
Riveting allows you to make joints from different positions without having to cause much damage or bring thermal effects. It is one of the easiest and most affordable methods as to quality inspection and disassembly of the joined parts for repair or maintenance.
Adhesive bonding doesn’t produce the strongest joints, but distortion or deformation of metals remains at the lowest possible level. It is a safer and less demanding metal bonding method that results in excellent fatigue strength.
Joining metals with fasteners lets you use them in a way that they can be adjusted to any level of shrinkage or swelling of the bonded objects. The overall cost of skilled labor for a project like this is just a fraction of what is required by some of the processes discussed here.
Bonding metal objects with nanomaterials is not much of a labor-intensive job, but you cannot simply start and finish it precisely without a learning curve. So, I think you’ll be better off trying the other methods whenever welding doesn’t seem very appealing.
Did I skip something that you think is essential to your understanding of these procedures? Feel free to inform me, so I can write you back. Stay safe!