What is Welding?
Welding is a fabrication process whereby two or more parts are fused together by means of heat, pressure, or both forming a join as the parts cool. Welding is usually used on metals and thermoplastics but can also be used on wood. The completed welded joint may be referred to as a weldment.
Some materials require the use of specific procedures and techniques. A number is considered “non-weldable,” a term that does not normally appear in dictionaries but is useful and descriptive in engineering.
The parts that are joined are called the parent material. The material that is added to form the joint is called the filler, or consumable. In the form of these materials, they may be called a base plate or tube, filler wire, consumable electrode (for arc welding), etc.
Consumables are usually chosen so that they have a similar composition to the parent material and thus form a homogeneous weld. However, there are cases, for example when welding brittle cast iron, when a filler with a very different composition and therefore properties is used. These welds are called heterogeneous.
The finished weld joint can be referred to as a weldment.
How Does Welding Work?
As opposed to brazing and soldering, in which the base metal does not melt, welding is a high heat process in which the base material is melted. Typically with the addition of a filler material.
Heat at high temperature causes a weld pool of molten material that cools to form the joint, which can be stronger than the base metal. Pressure can also be used to create a weld, either alongside the heat or by itself.
It can also use a shielding gas to protect the melted and filler metals from becoming contaminated or oxidised.
Plastics welding also uses heat to join the materials (although not in the case of solvent welding) and is accomplished in three stages.
Firstly, the surfaces are prepared before the application of heat and pressure, finally, the materials are allowed to cool to create fusion. Joining methods for plastics can be divided into external or internal heating methods, depending on the exact procedure.
In wood welding, the heat generated by friction is used to bond the materials together. The materials to be joined are subjected to high pressure before a linear frictional movement generates heat to join the workpieces together.
This is a quick process that allows wood to be joined without glue or nails in a matter of seconds.
Different Types of Welding Joint
There are 5 main joints used in welding. These are:
- Butt joint: A joint between the ends or edges of two parts making an angle to one another of 135-180° inclusive in the region of the joint.
- Corner joint: A Joint between the ends or edges of two parts making an angle to one another of more than 30 but less than 135° in the region of the joint.
- Edge joint: A Joint between the edges of two parts making an angle to one another of 0 to 30° inclusive in the region of the joint.
- Lap joint: A Joint between two overlapping parts making an angle to one another of 0-5° inclusive in the region of the weld or welds.
- Tee joint: A Joint between the end or edge of one part and the face of the other part, the parts making an angle to one another of more than 5 up to and including 90° in the region of the joint.
- Cruciform Joint: A Joint in which two flat plates or two bars are welded to another flat plate at right angles and on the same axis.
Read detailed article: Different Types of Welding joint
Types Of Welds
Following are the Different Types of Welds:
- Fillet Welds
- Groove Welds
- Surfacing Weld
- Plug Weld
- Slot Weld
- Flash Weld
- Seam Weld
- Upset Weld
A fillet weld joins two surfaces at an approximate right angle to each other. There are several types of fillet weld:
- Full fillet weld is a weld where the size of the weld is the same as the thickness of the thinner object joined together.
- Staggered intermittent fillet weld refers to two lines of intermittent welding on a joint. An example is a tee joint (see below) where the fillet increments that are in one line are staggered in comparison to the other line.
- Chain Intermittent fillet weld refers to two lines of intermittent fillet welds in a lap joint or T where the welds in one line are approximately opposite those in the other line.
Other terms associated with fillet welds include:
- Boxing: which refers to the continuation of a fillet weld around a corner of a member. It is an extension of the principal weld.
- Convexity: Refers to the maximum perpendicular distance from the face of a convex fillet weld to a line joining the toes.
The second most popular type of weld is the groove weld. There are seven basic types of groove welds, which are shown in figure 6-25.
The groove weld refers to beads that are deposited in a groove between two members to be joined. The type of weld used will determine the manner in which the seam, joint, or surface is prepared.
These are welds composed of one or more strings or weave beads deposited on an unbroken surface to obtain desired properties or dimensions.
This type of weld is used to build up surfaces or replace metal on worn surfaces. It is also used with square butt joints.
Plug welds are circular welds made through one member of a lap or tee joint joining that member to the other.
The weld may or may not be made through a hole in the first member; if a hole is used, the walls may or may not be parallel and the hole may be partially or completely filled with weld metal. Such welds are often used in place of rivets.
NOTE: A fillet welded hole or a spot weld does not conform to this definition.
This is a weld made in an elongated hole in one member of a lap or tee joint joining that member to the surface of the other member that is exposed through the hole.
This hole may be open at one end and may be partially or completely filled with weld metal.
NOTE: A fillet welded slot does not conform to this definition.
Flash welding is referred to as a resistance welding process where fusion is produced over the entire abutting surface.
Heat is created by the resistance to the current flow between two surfaces and by the application of pressure after heating is mostly complete.
Flashing is accompanied by the expulsion of metal from the joint.
A weld made by arc seam or resistance seam welding where the welding process is not specified.
This term infers resistance seam welding.
A spot weld is a weld made by arc spot or resistance spot welding where the welding process is not specified.
This term infers a resistance spot weld.
An upset weld is a resistance welding process where fusion occurs progressively along a joint of over the entire abutting surface.
The application of pressure before heating is required and occurs during the heating period.
Heat comes from the resistance to the flow of electric current in the area of contact between the surfaces.
What Is a Welding Position?
A welding position is a technique that allows a welder to join metals in the position in which they are found or the position in which a specific component will be used.
Often that may be on the ceiling, in the corner, or on the floor.
Techniques have been developed to allow welding in any position. Some welding processes have all-position capabilities, while others may be used in only one or two positions.
All welding can be classified according to the position of the workpiece or the position of the welded joint on the plates or sections being welded.
Why Are There Different Welding Positions?
Those who’ve never taken welding classes or fused metal in the field might assume a welder simply sits at a workstation and fuses the metal components in front of them, moving freely around the table and repositioning the workpiece as needed.
But in everyday work environments, joining metal can be much trickier. Workpieces may be attached to the ceiling, the corner or the floor.
Welders need techniques to be able to weld in any position. So the four common welding positions were developed.
Different Welding Positions
There are four main types of welding positions as per American Welding Society(AWS):
- Flat position
- Horizontal position
- Verticle position
- Overhead position
Flat position (1G Or 1F)
Also referred to as a “downhand” position, the flat position weld is the easiest and often the first weld that new students learn. The metals to be joined are placed flat, and the welder passes the electric arc over them, moving across the workpiece in a horizontal direction. The joint’s top side is welded together allowing the molten material to move downward into its edges or groove.
Note: The axis of a weld is a line through the length of the weld, perpendicular to the cross section at its center of gravity.
Horizontal Position (2F Or 2G)
The horizontal position is considered an out-of-position weld. Along with the vertical and overhead, the horizontal position can be more challenging to perform and require a higher level of skill.
The weld axis is horizontal. How the position is executed depends on the type of weld. For a fillet weld, the weld bead is placed where a vertical and a horizontal piece of metal meet at a 90-degree angle. When performing a groove weld, the weld face will be along a vertical plane.
Vertical Position (3F Or 3G)
For a vertical position weld, both the weld and plate will lie vertically. One of the major problems when performing this weld is the molten metal flowing downward and piling up. Welding in a downhill or upward vertical position can prevent this issue.
The flow of metal can be controlled by pointing the flame upward at a 45 degree angle to the plate, and holding the rod between the flame and the molten puddle (see above).
The manipulation of the torch and the filler rod keeps the metal from sagging or falling and ensures good penetration and fusion at the joint.
Both the torch and the welding rod should be oscillated to deposit a uniform bead. The welding rod should be held slightly above the centerline of the joint, and the welding flame should sweep the molten metal across the joint to distribute it evenly.
Overhead Position (4F Or 4G)
The overhead position weld is the most difficult position to work in. The welding will be performed with the two pieces of metal above the welder, and the welder will have to angle him or herself and the equipment to reach the joints.
One major issue can be the metal sagging from the plate. When the metal sags, it creates a crown. To avoid this issue, the puddle of molten metal should be kept small.
As you can see, the welding position is essentially the location of the welder in relation to the workpiece. One of the major considerations with each position is the direction the welding consumable will flow due to gravity.
The position of the welded joint on the plates or sections to be joined forms the basis for all welding classifications, which are represented by welding symbols.
Before we discuss the different welding classifications, it may help you to first understand the types of welds and weld joints on which these positions are typically performed.
Parts of Welding(Features of Completed Welds)
- Machine: Welding machine is the main parts of this process, because without machine certainly, we can not do welding process.
- Electrode Cable: The function Electrode cable connects the current from welding machine to electrode which we use to weld the base metal.
- Massa Cable: Massa Cable has a function for connecting current from machine to base metal, after that base metal and electrode touch then will welding process is happening.
- Welding Power Source: Have to function for supply current from electrical source to welding machine.
- Current Control: For control current output which uses for the welding process, big or little the current dependent form type or thickness of material (base metal).
- Electrode Holder: For hold the electrode so we can do welding process easily. Otherside holder too has a function for an electric current to the electrodes.
- Earth Cramp: To connect the machine to the base metal.
- Switch:For on or off the welding machine.
- Electrode: As a filler metal, after the welding process finish then the electrode will change be weld metal. The electrode has a flux which the function is to protect steel melting when the welding process takes place.
- Parent Metal: Metal to be joined or surfaced by welding, braze welding or brazing.
- Filler Metal: Metal added during welding, braze welding, brazing or surfacing.
- Heat Affected Zone (HAZ): The part of the parent metal metallurgically affected by the weld or thermal cutting heat, but not melted.
- Fusion Line: Boundary between the weld metal and the HAZ in a fusion weld. This is a non-standard term for weld junction.
- Weld Zone: Zone containing the weld metal and the HAZ.
- Weld Face: The surface of a fusion weld exposed on the side from which the weld has been made.
- Weld Root: Zone on the side of the first run furthest from the welder.
- Weld Toe: Boundary between a weld face and the parent metal or between runs. This is a very important feature of a weld since toes are points of high-stress concentration and often they are initiation points for different types of cracks
Types of Welding
Different types of welding include:
- Metal inert gas (MIG) Welding
- Stick Welding
- Tungsten inert gas (TIG) welding
- Metal Active Gas (MAG) Welding,
- Flux-cored arc welding (FCAW),
- Submerged arc welding (SAW),
- Shielded metal arc welding (SMAW)
- Plasma arc welding.
- Energy Beam Welding (EBW)
Metal inert gas (MIG) Welding
MIG welding is one of the easier types of welding for beginners to learn. MIG welding is actually two different types of welding. The first uses bare wire and the second flux core.
Bare wire MIG welding can be used to join thin pieces of metal together. Flux core MIG welding can be used outdoors because it does not require a flow meter or gas supply. MIG welding is usually the welding of choice for DIY enthusiasts and hobby welders who don’t have the money to spend on expensive equipment.
Stick welding, also known as Arc welding, is doing it the old fashioned way. Stick welding is a bit harder to master than MIG welding, but you can pick up a stick welding equipment for very little if you want to have a go at home. Stick welding uses a stick electrode welding rod.
Tungsten inert gas (TIG) welding
TIG welding is extremely versatile, but it is also one of the more difficult welding techniques to learn and Lincoln Electric TIG welders are skilled individuals.
Two hands are needed for TIG welding. One hand feeds the rod whilst the other holds a TIG torch. This torch creates the heat and arc, which are used to weld most conventional metals, including aluminum, steel, nickel alloys, copper alloys, cobalt and titanium.
Metal Active Gas (MAG) welding
Metal Inert Gas (MIG) and Metal Active Gas (MAG) welding are gas metal arc welding (GMAW) processes that use heat created from a DC electric arc between a consumable metal electrode and a workpiece which melt together to create a weld pool that fuses to form a join.
Flux cored arc welding (FCAW)
Flux cored arc welding (FCAW) is a semi-automatic arc welding process that is similar to metal active gas (MAG) welding. FCAW uses a continuous wire fed electrode, a constant-voltage welding power supply, and similar equipment to MAG welding.
Submerged-arc welding (SAW)
Submerged-arc welding (SAW) is a common arc welding process that involves the formation of an arc between a continuously fed electrode and the workpiece. A blanket of powdered flux generates a protective gas shield and a slag (and may also be used to add alloying elements to the weld pool) which protects the weld zone.
Shielded metal arc welding (SMAW)
Shielded metal arc welding (SMAW), also known as manual metal arc welding (MMA or MMAW), flux shielded arc welding or informally as stick welding, is a manual arc welding process that uses a consumable electrode covered with a flux to lay the weld.
Plasma Arc Welding
Plasma arc welding is a precision technique and is commonly used in aerospace applications where the metal thickness is 0.015 of an inch. One example of such an application would be on an engine blade or an air seal. Plasma arc welding is very similar in technique to TIG welding, but the electrode is recessed and the ionizing gases inside the arc are used to create heat.
Electron Beam and Laser Welding
Electron beam and laser welding are extremely precise, high energy welding techniques.
Frequently Ask Question
Welding is a fabrication process whereby two or more parts are fused together by means of heat, pressure or both forming a join as the parts cool. Welding is usually used on metals and thermoplastics but can also be used on wood. The completed welded joint may be referred to as a weldment.
There are five basic welding joint types commonly used in the industry, according to the AWS:
1. Butt joint.
2. Tee joint.
3. Corner joint.
4. Lap joint.
5. Edge joint.
Different Types of Welds:
1. Fillet Welds
2. Groove Welds
3. Surfacing Weld
4. Plug Weld
5. Slot Weld
6. Flash Weld
7. Seam Weld
There are four main types of welding positions:
1. Flat position
2. Horizontal position
3. Vertical position
4. Overhead position
Different types of welding include:
1. Metal inert gas (MIG) Welding
2. Stick Welding
3. Tungsten inert gas (TIG) welding
4. Metal Active Gas (MAG) Welding,
5. Flux-cored arc welding (FCAW),
6. Submerged arc welding (SAW),
7. Shielded metal arc welding (SMAW)
8. Plasma arc welding.
9. Energy Beam Welding (EBW)