Seam Welding

Essentially, seam welding is the foremost technique being used to join two surfaces. Seam welding is the joining of work pieces made of similar or dissimilar materials along a continuous seam. Seam welding can be classified into two principal techniques, resistance seam welding and friction seam welding.

The seam welding procedure involves the joining of two similar or dissimilar metals. To paraphrase, it is a continuous weld along a joint. Despite the fact that it is distinctive from butt welding, this type of welding could be used to produce butt joints.

It is typical for anyone to mistake seam welding with spot welding. This is because they are comparable in several ways. Both make use of two electrodes commonly produced from copper as opposed to one. In seam welding, the disc-shaped electrodes rotate while the material being welded passes through them. Consequently, the electrodes will be in continuous contact with the materials being welded.

Seam welding is critical for fabrication. This particular welding process is commonly employed to produce steel beverage cans. Additionally, it is a operation utilised in the manufacture of steel tubing. Considering that it is capable of both fillet and butt joints, it is used to make rectangular and round steel tubing.

Furthermore, this particular welding process is frequently employed in vehicle manufacturing. Components which include petrol or diesel tanks are fabricated by using this welding technique. Domestic radiators and even steel drums are likewise fabricated making use of this welding process.

Resistance Seam Welding

Resistance seam welding is a variation of resistance spot welding considering the main difference being the fact that welding electrodes are motor driven wheels ınstead of stationary rods. Well suited for sheet metal fabrication, this particular welding method passes an electric current through the sheets of metals being joined while they are held together using a mechanical force in a lap configuration between shaped copper electrodes. Similarly to other types of resistance welding, fusion is produced at the spot where the sheet surfaces come into contact; for this being the point of highest electrical resistance and as a consequence the place where heat generation is at its greatest. The heat from the disc-shaped electrode wheels generates a continuous weld as the work pieces are fed between them, producing a rolling resistance weld or a non-hermetic seam weld.

Resistance seam welding can either make use of an intermittent motion, in which the speed of the roller isn't predetermined, or continuous motion seam welding in which the speed of the electrode roller is predetermined prior to when the current is supplied. This technique is suitable in order to weld virtually every form of metal, with the exception of copper and copper alloys.

Consumable Wire Resistance Seam Welding

An alternate technique, termed consumable wire resistance seam welding is comparable to standard resistance seam welding, with the exception that the electrode wheel is grooved ın order that a shaped copper wire can be introduced between the wheel and the material being joined. This particular copper wire is fed from a spool and passes around the electrode wheel at welding speed prior to being discharged into a scrap container. This approach makes certain that a clean, uncontaminated surface is constantly presented towards the work.

Appropriate for welding coated and stainless steel, this method is extremely reliable and it is capable of achieving welding speeds in excess of 70 metres per minute. Although the consumable wire increases the cost of this form of welding, the expense can be balanced out through the scrap return value of copper.

The Working Principle

The working principle of resistance seam welding is comparable to the working principle of resistance welding. As per the working principle belonging to the resistance seam welding, the heat necessary for the duration of the welding is produced as a result of the resistance of the material. In straightforward terminology, heat generation arises as a consequence of the resistance of the material. Continuous spot welding is simply seam welding.

In seam welding, electrodes of roller type are employed. The two rollers have an identical size. In this case, these roller type electrodes are brought in contact with the workpiece. Subsequently, electric current is supplied to these rollers. As the supplied current is very high, the interface surface between the roller and the workpiece commences to melt and thereby, a strong weld joint is formed. Following that, these rollers begin to rotate on the surface of the workpiece. As these rollers move, a generation of a continuous joint is accomplished.

The welding speed is normally 60 in/min in this welding technique. This particular speed is usually regarded as being standard, nevertheless, when taking into consideration the practical applications, in that case, there can be possibilities that this speed could increase or decrease.

Despite the fact that there are a few obvious dissimilarities involving seam welding process and other welding processes, it generally follows exactly the same welding principles. Therefore, a power source is required to supply low voltage plus high power AC. The joint is heated to its melting point through the continuous flow of the electric current. The instant the joint attains its melting point, the semi-molten surfaces are joined together. This resultant fusion bond will likely be resulting from welding pressure.

Preferably, there are two different types of joints found in resistance seam welding - fillet weld and butt joint weld. A fillet weld can be described as a triangular joint weld which connects the two surfaces together at right angles. A butt joint weld, in contrast, can be described as a joint weld in which two surfaces butt up against each other. In a butt joint weld, the surfaces connect to create a single plane surface. Such type of joint is the most commonly seen in seam welding.

Types of Seam welding

Seam welding processes may be categorised into two, continuous and intermittent. These specific two types of welding techniques are different.

Continuous seam welding

In continuous seam welding technique, the electrodes rotate with a consistent and predetermined speed. This is carried out to create an overlapping weld. To accomplish this form of weld, timed current impulses are needed to generate an overlapping weld

The same can be achieved by means of moving the workpieces at a consistent speed between the electrodes. In this type of weld, sheets are arranged in small overlaps over the other. The sheets are subsequently mashed together.

Considering the fact that in this approach the current is switched at regular time intervals, it becomes easier to obtain the required spacing with the welds so as to generate overlapped spots of the weld.

The outcome is generally a joint which is 10 to 50 percent thicker ın comparison to the original sheet. It could be required to do some post-weld planishing to reduce the thickness of the joint.

Intermittent seam welding

In intermittent seam welding, the current pulses are passed intermittently. The current pulses combined with pressure created by the wheels generate separate spot welds. Such type of welding enables the workpiece to advance from one weld position to another. Intermittent seam welding is suitable for welding thicker materials and specifically those that are resistant to continuous seam welding.

Intermittent resistant welding method is fairly distinctive from continuous weld method for the reason that the workpieces continue moving or continue to be active until the moment weld position stops. This permits the welding process to occur automatically, permitting the position of the weld to advance to the next place. This type of technique of joining the metals is definitely well suited for sheets which are too thick in character and cannot be welded, for instance, flange welds which are prominently found in watertight tanks.

Advantages of Resistance Seam Welding

Resistance seam welding process offers the advantage of producing clear welds without any gas formation or welding fume. Additionally there is no requirement to make use of filler materials for making the join, which can be made to be both gas and liquid tight, offering a number of applications. The process is often fully automated, rendering it a highly repeatable process. Additionally, resistance seam welding can produce both a single seam weld and a parallel seam weld simultaneously.

This justifies an in depth look at the advantages of this particular welding process:

• Resistance seam welding is well known with regard to forming the clear weld.
• There are only a few types of the welding processes where no gas formation takes place or no other type of fumes are emitted. And in resistance seam welding is one such type of the welding process.
• An additional advantage of resistance seam welding process is that there is no requirement of filler material during this welding method.
• Resistance seam welding is usually conveniently automated consequently there' no requirement of addition of labours for accomplishing this process. Resulting from the process being automated, it is faster as compared to other similar processes including spot welding.
• In case the simultaneous formation of single seam weld and parallel seam weld becomes necessary, in that case, resistance seam weld process is the only option. Resistance seam welding process produces parallel seam weld and single seam weld concurrently.
• The process of seam welding is fairly simpler and involves reduced operator skills as compared with arc or spot type of welding process. Employing this technique, an increased rate of production is possible combined with the advantage of excellent repeatability and reliability.
• With the assistance of the continuous spot welding gas - tight along with liquid tight joints can be produced. This produces watertight and airtight seals which is most effective for fabricating components that require air or water leakage protection
• Besides the different benefits, seam welded objects experience reduced overlapping when compared to spot or projection welds.
• The joints created using this particular welding technique are typically strong and robust

Disadvantages of Resistance Seam Welding

Whereas resistance seam welding is okay with regard to producing joins in a straight line, the rollers are unable to produce more complicated curved welds. Welding is additionally impossible at internal corners or where other component features obstruct access for the wheel electrodes.

This technique is furthermore unsuitable for joining sheets of metal of in excess of 3mm in thickness. As a consequence of the speed of the roller, an experienced operator is usually needed to ensure the quality of the weld, while the welding machinery is in addition expensive.

• This kind of welding process is incredibly complicated to execute for sheets of metals that have a thickness larger than 3 mm. Consequently, it is strongly recommended that employ this technique in case the sheets of metals possess a thickness smaller than 3 mm.
• Simply stated, it isn't intended for metal pieces exceeding a specific thickness.
• As a consequence of the equipment utilised, only straight or uniformly curved lines are attainable utilizing this type of welding process
• You have to follow a particular path in this welding process. Which means that rollers consistently move in a straight line. Hence, in cases where a weld is required to be created at some complex place in that case, this process isn't applicable.
• Experienced operators or machines are essential which can handle the speed of the roller according to the situations.
• The machinery which is utilised in this particular welding carries a very high price tag. On account of excessive equipment cost, it happens to be employed in an exceedingly small proportion.

Resistance Seam Welding Applications

As a consequence of the capability to create gas or liquid-tight joins, this technique is suitable for producing items that include steel fuel tanks for vehicles, in addition to tin cans, radiators or steel drums. Resistance seam welds are additionally found on various types of barrel and exhaust systems.

Widespread for joining aircraft tanks, refrigerators and oil transformers, this technique can be employed for welding stainless steel, nickel alloys, and magnesium alloys.

• It performs an essential role in the manufacturing of all types of the barrels in addition to nearly all type of the exhaust system.
• There are multitude of applications of this technique in the case of aircraft tanks, refrigerators, oil transformers, etcetera.
• It is additionally employed in the welding of the stainless steel, nickel alloys, and magnesium alloys.

The bottom line is that this welding process is known for a wide variety of applications. There are several advantages in addition to disadvantages nevertheless it is fairly superior as compared to alternative welding techniques. Although there are numerous drawbacks, it is typically employed when uniform welding becomes necessary in a straight line.

Friction Seam Welding

This particular joining method makes use of friction to generate heat for the weld joint ınstead of using electrodes. Similar to various other friction welding processes, the workpieces are joined in the solid phase without the need of melting the materials, which means that there's no fusion and as a consequence virtually no interdiffusion involving the consumable and the substrate.

Suitable for joining materials which are challenging to weld by using conventional arc welding techniques, friction seam welding generates heat through a rotating consumable bar that is axially pressed into a V or U shaped groove. The workpieces are moved under the rotating consumable as a deposit is laid down in the groove.

Like other friction welding techniques, friction seam welding joins workpieces together in the solid phase without the need of melting either of the materials. Heat is generated by friction between the workpieces and a rotating consumable bar, which happens to be axially pressed into a V or U shaped groove. A deposit is laid into the groove even while moving the workpieces underneath the rotating consumable.

There exists a possibility of joining materials, which are generally challenging to weld using conventional arc welding techniques. Among the many process advantages is that there is no fusion. Consequently, there is virtually no interdiffusion involving the consumable and substrate.

Types of Friction Welding

There are numerous variations in the process that fundamentally work on the identical principle as mentioned previously which are the following:

• Continuous Induce Friction Welding: In this welding process, the rotor is connected with a band brake. In the event the temperature attains the limit of plastic temperature, then this band brake comes into action whose purpose is to stop the rotor although the pressure applied on the workpiece increases until the weld is formed.
• Inertia Friction Welding/Spin Welding: In this welding process, as opposed to the band brake, there are engine flywheel and shaft flywheel. These kind of flywheels connect the chuck to the motor. To start with both flywheels are connected with each other. In the event the speed or friction attains its limit, the engine flywheel will become detached from the shaft flywheel. The shaft flywheel carries a low moment of inertia which stops automatically without any assistance of a brake. The pressure force is continuously applied to the workpiece until the weld is formed.
• Linear Friction Welding: This process is equivalent to the spin welding process however in this process, the chuck rotates circularly as opposed to in linear friction welding it oscillates instead of spinning. It includes a considerably slower speed in comparison to spin welding which happens to be beneficial for the job in linear friction process considering that oftentimes the quality of the weld is superior to that of spin welding.
• Linear Vibration Welding: In linear vibration welding, the materials are placed in contact with each other and placed under high pressure. An external vibration force is subsequently applied to rub the pieces against each other, perpendicular to the pressure being applied. Both the workpieces are vibrated at 200 Hz frequency. Principally this technique is employed in the automotive industry.
• Friction Surfacing: This technique is derived from a friction welding process in which a coating material is applied to a substrate. Essentially this is the surface coating process. A rod composed of the coating material which is called mechatrode. Subsequently it is rotated under pressure, generating a plastic-type layer in the rod at the interface with the substrate. As a result of moving a substrate across the face of the rotating rod, a plastic-like layer is deposited.

Advantages of Friction Welding

Only some welding techniques ensure the same joint results. For this reason, the type of welding is selected based on the properties imparted to the joint by the welding process.

Enables joining dissimilar metals: Among the significant advantages of friction welding is that it is useful to join dissimilar metals. Examples of the common bimetallic friction joints are:

• Aluminium to steel
• Copper to aluminium
• Titanium to copper
• Nickel alloy to steel

Typically, every forgeable metal can be friction welded. This provides more versatility to the engineers because they can produce bimetallic structures as a result of friction welding. Copper to aluminium joints are ordinarily regarded as unwieldable, however, using friction welding, it is possible.

There isn't any external application of heat or flux: Friction welding doesn't require any external heat or flux, maintaining the procedure convenient and significantly less messy.

Minimal or no defects: Among the several advantages of solid-state welding is that it carries minimal or no defects in comparison to fusion welding. Identical effects are carried over to friction welding.

Very fast process: Friction welding is recognised as one of the fastest welding methods, clocking nearly twice or even 100x faster than normal fusion welds.

Doesn’t require considerable surface preparation: Machined, saw cut or sheared surfaces can be joined using friction welding. On the other hand, the presence of lubricants or oils is not permitted for optimal weld conditions.

Numerous industries depend upon friction welding to make otherwise unwieldable joints. It happens to be fast, efficient, and one of the most widely used options in regards to solid-state welding.

Disadvantages of Friction Welding

• This process is restricted to angular and flat butt joints.
• The preparation of the workpiece is more critical when compared to making a weld.
• The expense of the setup of the machine is very high.
• It can only be used for smaller parts of machines, big parts are not compatible with it.