Novelty Steel offers high quality welding services with its dedicated and certified welders and quality team

Contents

What is welding ?

Metal welding is a method of connecting two separate metal objects (same or different metals) by bonding through appropriate ways. Although methods will vary, from the thinnest plate to the thickest plate, majority of the metals can be welded by one or more welding methods. The material characteristics (such as melting point, ductility, electrical conductivity, yield strength, and plasticity, etc.) determines the difficulty of welding and appropriate welding method. There are various welding tests to identify welding defects.

Welding works for metal fabrication

Welding Different Metals

Carbon Steel Welding

Carbon steel is one of the most commonly welded materials due to its wide availability, affordability, and versatility. It is categorized into low, medium, and high-carbon steels based on carbon content, each with its specific welding requirements.

Challenges

  • High-Carbon Steel: Increased carbon content can lead to hardening and brittleness in the heat-affected zone (HAZ).

  • Weld Cracking: Rapid cooling can cause cracking in high-carbon steels.

Techniques

  • MIG/MAG Welding: A common choice for welding carbon steel.

  • Stick Welding : Used when Mig/Mag isn’t available, preferred on sites.

  • Post-Weld Heat Treatment (PWHT): Used to relieve stresses and improve toughness in high-carbon steels.

Stainless Steel Welding

Stainless steel offers excellent corrosion resistance and strength, making it ideal for applications in harsh environments. It is classified into three main types: austenitic, ferritic, and martensitic stainless steels.

Challenges

  • Sensitization: High temperatures can lead to chromium carbide formation, reducing corrosion resistance.

  • Distortion: High thermal expansion can cause warping during welding of stainless steel.

Techniques

  • TIG Welding: Preferred for its precision and control.

  • Ferrite Control: Appropriate ferrite content prevents cracking.

  • Back-Purging: Using inert gas to protect the weld’s backside from oxidation.
stick welding

Aluminium Welding

Aluminium is lightweight, corrosion-resistant, and has excellent thermal and electrical conductivity. These properties make it a popular material in automotive, aerospace, and marine industries.

Challenges

  • Oxide Layer: Aluminium forms a strong oxide layer that must be removed before welding.

  • Porosity: High affinity for hydrogen can lead to porosity in welds.

  • Thermal Conductivity: Aluminium dissipates heat quickly, requiring high heat input for effective welding.

Techniques

  • Gas Metal Arc Welding (GMAW/MIG): Common for thicker aluminium sections.

  • Gas Tungsten Arc Welding (GTAW/TIG): Preferred for thin sections and high-quality welds.

  • Preheating: Minimizes thermal stresses and reduces the risk of cracking.

Sheet metal Tig Welding

Comparison of Welding Metals

  • Carbon Steel: Easiest to weld, cost-effective, but less corrosion-resistant.

  • Stainless Steel: Challenging due to heat management but offers excellent strength and corrosion resistance.

  • Aluminium: Requires significant skill and preparation, but it’s lightweight and highly resistant to corrosion.

Property Carbon Steel Stainless Steel Aluminium
Ease of Welding Relatively easy to weld, highly weldable. Moderate difficulty; requires care with heat. Difficult; requires specialized techniques.
Melting Point ~1425–1540°C (2597–2800°F) ~1370–1530°C (2498–2786°F) ~660°C (1220°F)
Common Welding Methods SMAW, GMAW, FCAW, TIG, and MIG. TIG, MIG, and stick welding (SMAW). TIG, MIG, and sometimes resistance welding.
Pre-weld Preparation Moderate prep; cleaning to remove rust, oil. Extensive cleaning to avoid contamination. Extensive cleaning (oxide removal essential).
Thermal Conductivity Low to moderate. Low; retains heat in the weld zone. High; dissipates heat quickly.
Heat Input Control Moderate control needed. Requires precise control to avoid warping. High control due to risk of overheating.
Challenges Risk of porosity and distortion. Susceptible to thermal expansion and warping. Oxide layer requires removal.
Shielding Gas CO₂, or CO₂ + Argon mix. Argon or Helium + Argon mix. 100% Argon (sometimes Helium mix).
Welding Speed Moderate speed, depending on thickness. Slower due to precision requirements. Fast due to low melting point.
Post-Weld Treatment Stress-relieving recommended for thick sections. Cleaning or passivation for corrosion resistance. May require anodizing or finishing.
Durability of Welds Strong and durable; depends on filler material. High strength and corrosion resistance. Lighter but weaker if not heat-treated properly.
Corrosion Resistance Low; prone to rust without coating. High; inherent corrosion resistance. High; forms protective oxide layer.
Cost of Welding Low to moderate. Moderate to high. High due to specialized equipment and skill.
Applications Structural steel, pipelines, machinery. Food industry, medical devices, aerospace. Aerospace, automotive, shipbuilding

Welding Joints

Butt Welding

  • A butt joint refers to two metal pieces located side by side for welding. A preliminary edge preparation is essential for a high quality welding outcome.
  • The butt weld is relatively easier than the other joints and it withstands stress better than the others.
  • It is the most common welding joint in fabricating structures.

Corner Welding

  • Corner joints are very similar to Tee joints.
  • The main difference is the location of the metal is positioned.
  • In Tee joint, one metal is positioned in the center of the other, whereas in corner joints work pieces meet in the corner forming an ‘L’ shape.

Tee Welding

  • Tee welding joints are created when two metal parts intersect at a 90° angle.
  • This results in the edges getting together in the centre of a component in a ‘T’ shape.
  • Tee joints are also a type of fillet weld.
Steel Welder welding

Lap Welding

  • Lap joint refers to a joint when one part laps onto the other one.
  • The welding between the two parts is done by a fillet weld.
  • The major shortcoming of the lap joint is that some area below the weld pool is prone to rust.

Edge Welding

  • The edge welding joint is used to join parts that are parallel to each other.
  • Edge joints are often used for sheet metal welding
  • A cleaner and smoother weld surface than a butt joint.
Steel Welding Works

Welding Types

  • MIG Welding

MIG welding is generally used for thick materials. It uses a consumable wire that acts as both the electrode and the filler material. Compared to TIG welding, it is much faster, resulting in shorter lead times and lower production costs. MIG welding provides high quality welds, and it’s very common for most sheet metals, such as mild steel, aluminium and stainless steel.

  • TIG Welding

TIG Welding uses a non-consumable tungsten electrode that delivers the current to the welding arc. The tungsten and weld puddle are protected and cooled with an argon gas.

TIG welding is most commonly used for welding non-ferrous metals like aluminium, titanium, chromium, etc.

  • Stick Welding

Stick welding is the most frequently used welding method among arc welding procedures. To join metals, it uses an electric current and an anode at the weld pool. Its simplicity and versatility makes it one of the most popular.

The electric current creates an electric arc between the work pieces and the electrode. This spot is known as the weld pool.

Stick welding is mainly used in welding mild steel and is widely used in the repair and maintenance works.

  • Gas Welding

Gas welding is one of the conventional forms of welding by heat. The heat generated from burning the fuel, oxygen is used to join work pieces by melting them. Gas welding has a broad scope of application and it can be used for both ferrous and non-ferrous metals. Gas welding is very effective for pipe welding and maintenance works of ventilation and air conditioning systems.

Welding Quality Tests

Pros:

  • Simple, quick, and inexpensive.
  • Does not require specialized equipment.
  • Can identify surface defects like cracks, porosity, undercuts, and overlaps.

Cons:

  • Limited to surface defects; cannot detect subsurface flaws.
  • Requires skilled inspectors for accurate assessments.
  • Cannot quantify the depth or severity of a defect.

Pros:

  • Detects surface and near-surface defects effectively.
  • Quick and relatively inexpensive.
  • Portable and simple equipment.
  • Works well on ferromagnetic materials.

Cons:

  • Limited to ferromagnetic materials (e.g., steel, iron).
  • Cannot detect deeply embedded flaws.
  • Surface preparation may be needed for effective results.
  • Requires interpretation by a skilled operator.

Pros:

  • Detects surface defects on any non-porous material (metals, plastics, ceramics).
  • Inexpensive and simple to perform.
  • Highly portable.

Cons:

  • Limited to surface defects; cannot detect subsurface flaws.
  • Requires thorough cleaning before and after testing.
  • Not suitable for porous materials.
  • Relies on proper application of the dye and inspection under appropriate lighting.

Pros:

  • Can detect internal defects (e.g., cracks, porosity, inclusions).
  • Provides a permanent record (film or digital image).
  • Effective for complex weld geometries.

Cons:

  • Expensive and requires specialized equipment.
  • Involves health and safety risks due to radiation exposure.
  • Requires skilled personnel for interpretation of images.
  • Not effective for very thick materials without increased radiation power.

Pros:

  • Highly accurate in detecting subsurface defects.
  • Provides precise location, size, and shape of flaws.
  • Can be used on thick materials.
  • Portable equipment.

Cons:

  • Requires skilled operators to interpret results accurately.
  • Difficult to use on very thin materials or rough surfaces.
  • Limited effectiveness on irregularly shaped welds or coarse-grained materials like cast iron.

Pros:

  • Highly effective for detecting leaks in sealed or pressurized systems.
  • Methods like helium leak testing are extremely sensitive.
  • Can identify even small leaks.

Cons:

  • Some methods require expensive equipment (e.g., helium leak detection).
  • Time-consuming for large systems.
  • Surface preparation or pressurization may be necessary.
  • May not identify the exact location of the defect without additional inspection.