When you're welding, you must get to know the different types of welds there are. The seam weld is one of those weld types that people don't get too familiar with. In this article, you will not only get acquainted with this welding technique but also learn all there is to know about the seam welding process, techniques, and types of welding.
Before then, let's run through a brief intro on what this welding is.
What is seam weld?
Seam welding is a process of resistance welding in which two or more overlapping sheets of metal are joined progressively by local fusion. This fusion is conducted along a joint thanks to the operation of two circulating electrodes.
Copper electrodes apply pressure to the intended point of contact between two metal sheets to get ideal seams. This will create relatively high resistance to the flow of electric current between both sheets, generating heat. As a result of the heat generated, fusion takes place, and a seam weld is created.
Seam welds are produced from the rotatory motion of two electrodes instead of the conventional tipped electrodes.
Anatomy of Seam Welding
Seam welding is fusing similar or dissimilar metal sheets at the seam. It is facilitated by applying heating heat from electric current resistance. This popular type of resistance welding is easy to operate and gives few instances of overlapping.
The process of resistance seam welding primarily results in two distinct types of welds formed near the edge (seam) of two overlapping metal sheets; the intermittent/stitch weld and the continuous weld (you'll learn about both types later on in this article).
With this welding process, the roller electrodes are directed towards the metal sheets intended to be joined. Both workpieces are put under pressure, and an electric current is allowed to pass through them. As explained earlier, this process will give off heat, melting both metal sheets. This is sometimes known as "seam spot welding" because all the action happens in a single spot.
Precautions for Resistant Seam Welding
Before diving right in to create seam welds for your company or DIY projects, here is a list of precautions to be taken:
- Like any other process that uses electric current, you should be extra careful about the amount of current you supply to your workpieces.
- When the current provided is too high, the contact point between the metal sheet and the electrode will become too hot and dangerous.
- Washing the weld area with water can help mitigate too much heat. This also helps to maintain cool rollers while welding.
- Always ensure you keep an eye on the welding speed.
Techniques of Seam Welding
Seam welds are achieved using different techniques. In this section, you will learn about the three significant ways to accomplish this welding type.
For you to quickly understand the concept behind each technique, let's look at them individually rather than collectively.
The three techniques to weld these:
Resistance Seam Welding
Resistance seam welding is the most common technique of seam welding, which doubles as a variation of resistance spot welding. The main difference in electrical resistance is that the electrodes are motor-powered compared to the stationary rod in resistance spot welding.
This welding technique is suitable for metal fabrication as it allows the free flow of electric current through metal sheets for merging while they are held in place by mechanical force. As you have in other types of welding, resistance seam welding produces fusion at the point of contact of both metal sheets.
This happens because the point of contact is the spot with the highest resistance to electrical flow, generating more heat than other metal parts. The heat produced from the motor-driven electrodes creates a continuous weld as the metal sheets are placed between them. This results in a non-hermetic weld or a rolling resistance weld.
Types of Resistance Seam Welding
There are two significant types of resistance seam welding. One process can make use of intermittent motion, where the roller speed is not predetermined, while another method can make use of continuous motion where the electrode roller speed is predetermined before supplying the current.
Both types of electrical resistance seam welding have their importance and individual contribution to your project. Below is a comprehensive explanation of the distinctiveness of both intermittent and continuous resistance seam welding.
Intermittent Seam Welding
During intermittent or stitch seam welding, the weld is created at strategic spots rather than have them continue as in a straight line. This resistance seam welding is best for joining thick metals when a continuous weld does not apply.
This seam welding is a practical way to diminish the unnecessary effects of intense heat. Furthermore, intermittent seam welding gives you the advantage of less filler material consumption, reducing cost.
Benefits of intermittent the seam welding process
- The process takes less time to complete because it involves less effort than continuous seam welding.
- There is enhanced productivity and expedited welding due to less welding time.
On the other hand, intermittent seam welding has some disadvantages that are worth taking note of. Because of the short overall weld time, the weld point strength is relatively low. This could be a significant setback when handling projects prioritizing weld strength over completion time.
Continuous Seam Welding
Continuously seam welding is quite the opposite of intermittent seam welding. It takes more time to achieve, and welds go on along a straight line without breaking. Two things characterize this type of resistance seam weld; first, the uninterrupted supply of electric current flowing through the electrodes to the metals to be joined. Secondly, the speed of the rolling electrodes is predetermined.
You can create a continuous seam weld where the workpieces are kept under constant pressure to produce a uniform overlapping weld.
Consumable Wire Resistance Seam Welding
Consumable wire resistance seam welding is an alternative technique to traditional resistance seam welding, except for the rolling electrode wheel, which is grooved to allow the introduction of a shaped copper wire between workpieces and the wheel.
The copper wire is passed around the wheel during welding just before discharging it to a scrap container. This is to ensure a clean surface when working on your projects. Consumable wire resistance seam welding is ideal for stainless and coated steel in a very reliable process.
With this welding technique, you can achieve more than 70 meters per minute welding speed. Although the consumable wire contributes to the overall cost of this welding type, the copper scrap you get gives a compensating equivalent.
- Friction Seam Welding
The friction seam welding technique of joining metals uses friction as a heat source to create seam welds rather than electrodes. Workpieces are joined without melting (in their solid phase) as with another welding process involving friction. This implies no interdiffusion between the substrate and the consumable bar—literally, no fusion occurs.
Friction seam welding is best for joining metals that are naturally difficult to weld by conventional arc welding methods. Heat in friction seam welding is created by a consumable bar that is pressed axially into a U or V-shaped groove. The workpieces to be joined are moved under the consumable bar, leaving a deposit in the groove.
Procedures of Seam Welding
In seam welding, the primary parameter is the welding current. The amount of electric current allowed to pass through the rolling electrodes to the interface between the workpieces determines the amount of heat generated.
You'll find helpful seam welding procedures below:
- Make sure the materials to be joined are well cleaned, ideally overlapped, and placed between the electrodes to hold the pieces together.
- Turn on the coolant supply. Sometimes, the electrodes are cooled by spraying water on them or allowing refrigerated fluid to flow into the electrodes.
- Turn on the current supply. The first impulse electric current sets the electrodes in rotatory motion, moving the workpieces forward.
- Quickly switching on and off the current supply creates overlapping nuggets known as stitch welding.
- It is known as spot welding if each spot weld is made from a timed interruption in the welding current.
Advantages of Seam Welding
Seam welding is a popular method of joining metal sheets in a continuous weld. Seam welding is used practically on stainless steel, aluminum, tungsten, and titanium as a preferred welding process for welders. Most seam welding helps fabricate automobile mufflers and metal containers.
Small Overlapping Instances
Seam welding is your best bet if you're ever concerned about the weld overlapping. It leaves fewer instances of overlapping than spot and projection welding. Weld overlap produced in seam welding rarely goes beyond 10 mm.
It's a no-brainer
Seam welding is easy to operate and only requires basic skills of operation. Because of the simplicity of seam welding, welders can achieve a high production rate. In addition to joining similar and dissimilar metals, seam welding is reliable and has few challenges.
The cost of these welding machines is a little much for most small shops and DIY welders.
Current is Fully Utilized
There is less heat distortion in seam welding because the heat is directed to a small spot. The current is also turned on at intervals to minimize wastage. Electrodes can also have an extended life due to low current use compared to spot welding.
Best for Gas and Liquid Tight Containers
Seam welding works best for gaseous and liquid joints. Radiators, tin cans, and steel drums are produced through this welding process as they can create both airtight and watertight seals. It is also the best welding approach for fabricating metal welds that require protection against air or water leakage.
Fast Weld Process
Seam welding is the go-to process if you're in for a fast approach to welding. Because the entire process is fully automated, seam welding is more rapid than projection and spot welding. The transfer, loading, and unloading of components is automatic, making the entire process very fast and easy. You can also set the welding speed to enhance productivity.
Pollution reduction
The seam welding process does not involve gas formation or the emission of fumes. This is because the filler material can cause pollution when not in use.
Durable and Clear Welds
Resistance seam welding gives you durable welds with top-notch reliability. In addition, seam welds have a better appearance due to no indentations. The joints are formed by pressure and heat to give a sturdy weld.
Tools that are produced via seam welding are seen to always have better mechanical properties.
Applications of Seam Welding
Aside from the fabrication of liquid and airtight containers, resistance seam welding has several other applications, especially in the automotive industry.
Firstly, seam welding is used to manufacture car fuel tanks. Car manufacturers also use seam welding to produce chassis for sports cars. Because seam welds are sturdy, they make the chassis of racing cars durable and safe.
Resistance seam welding is also used in fabricating heat exchangers. Many heat exchangers made to undergo seam welding come out of excellent quality. They provide high corrosion resistance and are also a cost-effective way of fabrication.
Seam welding can also be applied broadly in the following respect:
- It helps make lap joints.
- Seam welding is used in manufacturing several oil switches, leakproof tanks, aircraft, and transformer tanks.
- Comes in handy in welding vessel parts that need to be water and airtight
- Welds tubes and pipes excellently
Conclusion
Seam welds are the consequence of seam welding, which is a process that involves the application of mechanical pressure to your workpiece to create a resistance to electrical flow. The resistance to electrical flow causes heat to be generated at a specific spot joining the two metals together.
The most common technique of seam welding is resistance seam welding, which may be intermittent or continuous. Seam welding is beginner-friendly, fast, and cost-effective.
All its processes are automated, giving it an edge over projection and spot welding. Lastly, the application of seam welding cuts across industries where durable, liquid, and airtight welds are required to reduce leakage.
If you're new to welding or just interested in seeing what we're learning on welding, check out our other welding articles.
