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What is welding?
Welding Technologies: A Comprehensive Guide
Welding is the process of joining together two or more pieces using heat and/or pressure to form a high-strength joint. There are many ways to perform a weld, each requiring different skill levels and utilizing various levels of technology in the equipment.
Heat Sources for Welding
To perform a weld, a heat source is required. These sources fall into three main categories:
- Thermochemical energy: Produced using a combination of gases such as oxygen and acetylene to create a flame. This traditional process requires a high level of manual skill and dexterity.
- Electrical energy: Establishes an arc between the electrical source (Arc welding power source) and the workpiece. This process produces heat at temperatures from 3,000°C to 20,000°C.
- Mechanical energy: Includes processes like friction welding, where heat is generated through mechanical means.
Key Metrics:
- Arc welding temperatures: 3,000°C to 20,000°C
- Plasma arc temperatures: In excess of 20,000°C
- Plasma velocity: Approaches the speed of sound
Arc Welding and Cutting Processes
The following are the main arc welding and cutting processes covered in this guide:
- Manual metal arc (MMA)
- MIG (Metal inert gas)
- MAG (Metal active gas)
- FCW (Flux cored welding)
- TIG (Tungsten inert gas)
- Plasma arc cutting
- Resistance welding
- Laser welding
- Submerged arc welding
In addition to these processes, other methods include ultrasound and friction welding, which will be covered in related units.
Materials and Process Selection
Commonly Welded Materials
The most commonly welded materials include:
- Aluminum and its alloys
- Mild steel
- Stainless steel and its alloys
- Various plastics (in today's rapidly changing manufacturing environment)
Process Selection Criteria
The welding process is chosen based on three primary factors:
- Material type and composition
- Material thickness
- Production requirements (rate and visual aesthetics)
Welding Processes Explained
Manual Arc (MMA)
One of the oldest welding processes still in common use today, particularly suited for outdoor welding and repair work.
- Slower process requiring high skill level
- Usable on a wide range of materials
- Effective in confined areas (electrodes can be bent)
- Lower equipment costs compared to other processes
Metal Inert/Active Gas (MIG/MAG)
A versatile welding process providing high deposition rates, suitable for various material thicknesses from thin to thick.
- Minimal weld finishing required (minimal spatter, no electrode slag)
- Requires low to medium skill level
- Creates narrow heat-affected area
- Often automated for higher production rates
- Torch components subject to wear (contact tips, nozzles, liners)
Flux Cored Welding (FCW)
A type of MIG/MAG welding using a standard power source but with a self-shielding consumable core.
- No additional gas shield supply required
- Ideal for outdoor welding with draughts
- Provides high deposition rates and productivity
- Produces slag coating requiring post-weld cleaning
- Uses standard MIG/MAG equipment with specialized wire
Tungsten Inert Gas (TIG)
An arc welding process using a non-consumable tungsten electrode to produce high-quality welds.
- Protected by inert shielding gas (argon or helium)
- Filler metal normally used (except for autogenous welds)
- Produces high-quality welds with excellent finish
- Generally slower process requiring higher skill level
- Uses constant-current welding power supply
Plasma Cutting
Uses an arc constricted by a fine bore nozzle, increasing the temperature and velocity of the plasma jet.
- Temperatures exceed 20,000°C
- Velocity approaches the speed of sound
- High plasma gas flow creates deeply penetrating jet
- Arc force removes molten material as dross
- Effective for cutting metals with refractory oxides
- Often the only practical or cost-effective solution
Resistance Welding (Spot)
One of the oldest electric welding processes, creating joints through a combination of heat, pressure, and time.
- Uses material resistance to current flow for localized heating
- Different materials create varying heat levels with the same current
- Electrode pressure maintains intimate contact between parts
- Current flow time determined by material properties and contact area
- Widely used in automotive and sheet metal industries
Process Comparison
| Criteria | TIG Welding | MMA Welding | MIG Welding |
|---|---|---|---|
| Skill level required | High | High - Especially for high quality and non-ferrous material | Low - Medium |
| Quality | Requires high skills for good quality | Requires high skills for good quality | Less problems to achieve good quality compared to TIG/MMA |
| Distortion/heat input | High | High | Low-narrow heat affected area |
| Ease of mechanization | Some difficult positions | Difficult | Simple |
| Equipment maintenance | Needs training | Needs basic training | Needs training |
| Consumable parts | Negligible | Negligible | Torch components such as contact tips, nozzles, liners etc. |
Industry Applications
Welding and cutting processes are utilized across numerous industries, organized into three main sectors:
Manufacturing
- Automotive assembly and components
- Aerospace structures and systems
- Shipbuilding and marine equipment
Construction and Infrastructure
- Structural fabrication
- Pipeline construction
- Offshore installations
Repair and Maintenance
- Vehicle repair
- Equipment maintenance
- DIY and home repair
The applications range from small-scale DIY projects to nuclear facilities, demonstrating the versatility and importance of welding technologies across all industrial sectors.