Welding

How Welding in General Serves Industrial Fabrication

Welding is the process of securely joining two materials together using the process of coalescence and often also a filler material. Welding releases heat and energy which in turn liquefies the materials at the intended joint. When the materials re-solidify a secure joint is formed. Typically, the materials joined consist of metals or thermoplastics.

Welding allows advanced fabrication to be undertaken by securely affixing these materials and thus facilitating the creation of a more developed piece of equipment or structure which can then be used accordingly for its intended purpose. In order to accomplish this important role welding must be versatile enough to work with a wide variety of different metals and thermoplastics in a range of varied, often difficult conditions.

How Does Welding Work?

As opposed to brazing and soldering, which do not melt the base metal, welding is a high heat process which melts the base material. Typically with the addition of a filler material.

The high heat causes a weld pool of molten material which cools to form the join, which can be stronger than the parent metal. Pressure can also be used to produce 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 oxidized.

Common Joint Configurations:

Butt Joint

A connection between the ends or edges of two parts making an angle to one another of 135-180° inclusive in the region of the joint.

T Joint

A connection 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.

Corner Joint

A connection 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 connection between the edges of two parts making an angle to one another of 0 to 30° inclusive in the region of the joint.

Cruciform Joint

A connection in which two flat plates or two bars are welded to another flat plate at right angles and on the same axis.

Lap Joint

A connection between two overlapping parts making an angle to one another of 0-5° inclusive in the region of the weld or welds.

Types of Welding Joints:

1)Welds Based on Configuration 

Slot weld

Joint between two overlapping components made by depositing a fillet weld around the periphery of a hole in one component so as to join it to the surface of the other component exposed through the hole.

Plug weld

Weld made by filling a hole in one component of a workpiece with filler metal so as to join it to the surface of an overlapping component exposed through the hole (the hole can be circular or oval).

2)Based on Penetration

Full penetration weld

Welded joint where the weld metal fully penetrates the joint with complete root fusion. 

Partial penetration weld

Weld in which the fusion penetration is intentionally less than full penetration. 

3)Welds Based on Accessibility

Features of Completed Welds

Butt weld

Fillet weld

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.

Weld Metal

All metal melted during the making of a weld and retained in the weld.

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 (eg fatigue cracks, cold cracks).

In order to reduce the stress concentration, toes must blend smoothly into the parent metal surface.

Excess Weld Metal

Weld metal lying outside the plane joining the toes. Other non-standard terms for this feature: reinforcement, overfill.

Note: the term reinforcement, although commonly used, is inappropriate because any excess weld metal over and above the surface of the parent metal does not make the joint stronger.

In fact, the thickness considered when designing a welded component is the design throat thickness, which does not include the excess weld metal.

Run (pass)

The metal melted or deposited during one passage of an electrode, torch or blowpipe.

Layer

Stratum of weld metal consisting of one or more runs.

Energy Sources

Different processes are determined by the energy source used, with a variety of different techniques available.

Until the end of the 19th century, forge welding was the only method used, but later processes, such as arc welding, have since been developed. Modern methods use gas flame, electric arc, lasers, electron beam, friction and even ultrasound to join materials. 

Care needs to be taken with these processes as they can lead to burns, electric shock, damaged vision, exposure to radiation or inhaling of poisonous welding fumes and gases. 

What are the Different Types of Welding Methods and What are They Used for?

There are a variety of different processes with their own techniques and applications for industry, these include:

Arc

This category includes a number of common manual, semi-automatic and automatic processes. These include metal inert gas (MIG) welding, stick welding, tungsten inert gas (TIG) welding, gas welding, metal active gas (MAG) welding, flux cored arc welding (FCAW), gas metal arc welding (GMAW), submerged arc welding (SAW), shielded metal arc welding (SMAW) and plasma arc welding.

These techniques usually use a filler material and are primarily used for joining metals including stainless steel, aluminum, nickel and copper alloys, cobalt and titanium. Arc welding processes are widely used across industries such as oil and gas, power, aerospace, automotive, and more. 

Shielded Metal Arc Welding (SMAW) – Shielded Metal Arc Welding is also known as “SMAW” or as “stick welding.” The stick in question refers to the electrode, which is coated in a protectant flux. An electrode holder holds the “stick” in place and an electric arc is created using either direct or alternating current. This in turn causes the electrode to slowly melt away while also melting the metals to be joined. At the same time the flux coating releases a gas vapor which, together with the slag, creates a shielded environment to protect the weld area from contamination.

Gas Tungsten Arc Welding (GTAW)– Gas Tungsten Arc Welding, also known as “GTAW” or “TIG welding” uses a tungsten electrode to produce the weld. Unlike SMAW welding the electrode is not consumed during the welding process. Instead the weld area is protected from atmospheric contamination by an inert gas, often Argon or Helium gas. The acronym “TIG” refers to “Tungsten Inert Gas.”

Gas Metal Arc Welding (GMAW) – Gas Metal Arc Welding, also known as “GMAW” or “MIG welding” uses a consumable wire electrode that is fed through a welding gun. An inert shielding gas such as Argon or a mixture of Argon and Carbon Dioxide is also sprayed over the welding puddle to protect it from contamination. MIG welding has become the most common welding method in industrial settings because of its versatility and relative ease. However, it is not ideal for use outdoors or in other areas with high air volatility.

Flux-Cored Arc Welding (FCAW) – Flux-Cored Arc Welding, or “FCAW,” is very similar to MIG welding; however, it features the use of a special tubular wire that is filled with flux. The flux may be sufficient by itself to protect the welding puddle from contamination or a shielding gas may also be used, depending on the filler material and other circumstances.

Submerged Arc Welding (SAW)– Submerged Arc Welding, or “SAW,” uses a consumable electrode that is fed automatically. It also uses a characteristic blanket of granular fusible flux, consisting of several compounds including silica, lime, calcium fluoride, and manganese oxide among others. This blanket of granular flux thus completely “submerges” the welding area thereby protecting it. 

Together these, and other welding services, do an outstanding job of servicing the industrial fabrication industry, especially when they are performed by highly qualified, experienced welders. 

Friction

Friction welding techniques join materials using mechanical friction. This can be performed in a variety of ways on different welding materials including steel, aluminum or even wood.

The mechanical friction generates heat which softens the materials which mix to create a bond as they cool. The manner in which the joining occurs is dependent on the exact process used, for example, friction stir welding (FSW), friction stir spot welding (FSSW), linear friction welding (LFW) and rotary friction welding (RFW).

Friction welding doesn’t require the use of filler metals, flux or shielding gas.

Friction is frequently used in aerospace applications as it is ideal for joining otherwise ‘non-weldable’ light-weight aluminium alloys.

Friction processes are used across industry and are also being explored as a method to bond wood without the use of adhesives or nails.

Electron Beam

This fusion joining process uses a beam of high velocity electrons to join materials. The kinetic energy of the electrons transforms into heat upon impact with the workpieces causing the materials to melt together.

Electron beam welding (EBW) is performed in a vacuum (with the use of a vacuum chamber) to prevent the beam from dissipating.

There are many common applications for EBW, as can be used to join thick sections. This means it can be applied across a number of industries from aerospace to nuclear power and automotive to rail.

Laser

Used to join thermoplastics or pieces of metal, this process uses a laser to provide a concentrated heat ideal for barrow, deep welds and high joining rates. Being easily automated, the high welding speed at which this process can be performed makes it perfect for high volume applications, such as within the automotive industry.

Laser beam welding can be performed in air rather than in a vacuum such as with electron beam joining.

Resistance

This is a fast process which is commonly used in the automotive industry. This process can be split into two types, resistance spot welding and resistance seam welding.

Spot welding uses heat delivered between two electrodes which is applied to a small area as the workpieces are clamped together.

Seam welding is similar to spot welding except it replaces the electrodes with rotating wheels to deliver a continuous leak-free weld.

Fabrication

Fabrication is the act of taking raw stock material and turning it into a part for use in an assembly process. Metal fabrication is the creation of metal structures by cutting, bending, welding and assembling processes. It is a value-added process involving the creation of machines, parts, and structures from various raw materials. Metal fabrication usually starts with drawings with precise dimensions and specifications. Typical projects include loose parts, instrument enclosures, structural frames for buildings and heavy equipment, and stairs and hand railings, etc.. 
There are many different types of fabrication processes. The most common are:

Cutting.

Folding.

Machining.

Punching.

Shearing.

Stamping.

Welding.

Welding in a Fabrication Cell

Let’s look at the types of fabrication processes in greater detail here:

  1. Cutting. There are many ways to cut nowadays. The old standby is the saw. Others now include plasma torches, water jets, and lasers. There is a wide range of complexity and price, with some machines costing in the millions.
  2. Folding. Some parts need to be bent. The most common method is a press brake (or brake press). It has a set of dies that pinches the metal to form a crease. This operation can only be performed in very specific cases due to the movement of the part and the possible shape of the dies. Designing for Lean manufacturing, though, can help prevent complex shapes that slow down production. Sometimes using two different types of fabrication processes or two different pieces fastened together work better than one complicated piece.
  3. Machining. This is the process of removing metal from a piece of material. It might be done on a lathe, where the material rotates against a cutting tool, or in some other cutting machine where a rotating tool is moved in a variety of ways against a stationary piece. Drills fall into this latter category. The range of motion of the cutting head is defined by the number of axes (i.e. a 3-axis machine).
  4. Punching. Punching is the act of a punch and a die forming a ‘scissor’ effect on a piece of metal to make a hole in it. Obviously, the punch and die must be the same shape and size of the desired hole. In some cases, the main piece of material is kept, as in when holes are added for fasteners. In other cases, the piece that is removed is the desired product-this is called ‘blanking’.
  5. Shearing. Shearing is the process of making a long cut on a piece of metal. It is, in effect, just like the action of one of those paper cutters with the long chop-handle. This is done on sheet metal.
  6. Stamping. Stamping is very similar to punching, except the material is not cut. The die is shaped to make a raised portion of material rather than penetrating.
  7. Welding. Welding is the act of joining two pieces of metal together. A variety of types of welding exist for use in different applications and for the range of metals used in manufacturing.
  8. Bending. Bending is done via press brakes, tube benders and similar tools. Modern metal fabricators use press brakes to coin or air-bend metal sheet into form. CNC-controlled backgauges use hard stops to position cut parts to place bend lines in specific positions.
  1. Assembling. Assembly (joining of pieces) is done by welding, binding with adhesives, riveting, threaded fasteners, or further bending in the form of crimped seams. Structural steel and sheet metal are the usual materials for fabrication; welding wire, flux and/or fasteners are used to join the cut pieces
  1.  Coating. Surface finishing is an industrial processes that alter the surface of a manufactured item to achieve a certain property. Finishing processes may be employed to: improve appearance, corrosion resistance, tarnish resistance, chemical resistance, hardness, remove burrs and other surface flaws, and control the surface friction.

There are many other types of fabrication processes that are less common than the ones in the list above. There are also constantly new types of fabrication methods being developed.

One such new type is called additive technology. In effect, a machine layers materials to form a part-something like a three dimensional printer that prints in plastic or other materials.

Application of Custom Metal Fabrication

Metal fabrication is the process of turning raw metals into pre-made shapes for assembly use. For example, Electrical enclosures and any type of metal enclosures require sheet metal fabrication. Look around you. Many people never notice it, but many of the products and components we take for granted have some aspect of precision sheet metal fabrication. From desk bracket to construction steel form, and all types of finished products and parts in between start out as sheet metal or heavy steel. The sheet metal fabricator machines punch, cut, drill, bend, shape and assembly metal sheet into an endless number of forms.
Fabricators use their experience and mastery of a variety of processes, including welding, heat treating, adhesive joining, brazing and soldering, stamping and rolling, tumbling, buffing, polishing and honing. Fabricators take the customers’ desired material, the rate of production, the desired geometry and other physical requirements of the part to create an optimized, cost-efficient manufacturing process. Companies across a broad spectrum of industries, products and service offerings require the expertise and services of companies that specialize in sheet metal fabrication. the sheet metal processing services cover the following industries:

– Containers, Equipment 
– Food and Beverage applications
– Modules and Parts for Motor Vehicles
– Power system
– Shipbuilding and Repair
– Construction, Civil Engineering
– Tubes and Other Semi-Finished Metallic Products
– Oil, and Coal and LNG Transportation
– Utilities and Waste Management
– Maintenance and Turnaround Operations
– General Fabrication
– Custom Fabrication


Although commercial and industrial companies typically use metal fabrication services, they purchase customized metal parts for plants, warehouses, office buildings and other spaces. Some residential homeowners also have a need for customized metal fabrication services.