Submerged Arc Welding (SAW) is a specialized welding method that delivers high-quality, efficient welds. It’s commonly used in industries like shipbuilding and pipeline construction.
This guide provides an in-depth look at SAW, including its equipment, materials, and advantages.
What is Submerged Arc Welding?
Submerged arc welding (SAW) was invented back in 1935 by the E. O. Paton Electric Welding Institute in Kyiv, Ukraine. This method gained significant attention for its application in the construction of the T34 military tank.
SAW is an arc welding process using a continuously fed consumable wire. Here, the welding arc and the molten zone are protected by a powdered granular flux.
The technique is known for its high-quality welds that are incredibly consistent and repeatable. This high-speed method provides a smooth, uniform finish, making it ideal for specific positions like flat or horizontal-vertical (HV) welding.
It’s essential to note that this method is not the same as underwater welding—two very different procedures.
Health and Safety Advantages
One of the best things about submerged arc welding is its safety features.
Since the arc is not visible, the risk of experiencing “arc eye,” a painful condition, is significantly reduced. Moreover, the process produces minimal fumes, making it a healthier option compared to other methods like carbon arc welding.
Equipment Needed for Submerged Arc Welding
Before you can begin submerged arc welding, there’s a checklist of essential equipment you need to collect. Ensuring you have the right tools will significantly streamline the process and yield better results.
- Welding Power Source: You’ll ideally want something with over 600 Amps and a 100% duty cycle. The duty cycle is crucial here—it represents the time the equipment can operate continuously without overheating.
- Wire Feed Unit with Control Unit: This is the heart of your operation. The wire feed unit controls the rate at which the wire is fed into the weld. If you’re looking for quality and repeatability, don’t skimp on this piece of equipment.
- Mechanized Travel System: Whether you’re using a welding tractor or a column and boom welder, having a mechanized system ensures consistent movement and thus, a uniform weld. More on types of mechanized systems later.
- Flux Hopper: A container for holding your flux. This piece of equipment will feed the flux into the weld as you go along, so make sure it’s dependable.
- Voltage Sensing Wire Feeder for Constant Current: This wire feeder is designed to keep your welding current steady, which is particularly useful for long welds.
- Soft Switch to Initiate the Weld: A soft switch makes it easier to start the welding process without a jolt, ensuring a smoother weld from start to finish.
- Magnetically Operated Valve Controlled by a System: This valve controls the flow of shielding gas or other elements and is usually automated to match the current and speed of your weld.
Types of Mechanized Travel for Submerged Arc Welding
Options for Mechanized Travel:
- Welding Tractor: Ideal for linear welding applications. The welding tractor follows a track or guide to maintain straight lines.
- Column and Boom Welder: Best for larger projects where vertical and horizontal movement is needed. The boom allows for precise placement of the welding head.
- Travel Carriage: Similar to the welding tractor but often lighter and more portable. Suitable for smaller jobs with linear welding requirements.
- Flux Recovery Unit: While not strictly a travel mechanism, this unit collects unused flux for recycling. Not only does it save materials, but it also keeps the workspace clean.
Each of these options has its advantages and drawbacks.
For instance, a welding tractor will offer excellent linear movement but might not be suitable for a project requiring a lot of vertical or horizontal adjustments.
Understanding the needs of your project will help you select the most effective travel mechanism.
Materials You Can Weld Using Submerged Arc Welding
|Material Types||Suitable for SAW?||Alternative Methods|
|Steel and Nickel Alloys||Yes||–|
|Mild Steels||Yes||Carbon Arc Welding|
|Low Alloy and Stainless Steels||Yes||–|
|High Nickel Alloys (Hastelloy, Inconel)||Yes||–|
|Materials under 10mm thickness||No||Plasma Welding, Spot Welding|
While submerged arc welding is incredibly versatile, it’s crucial to know when to use it and when to opt for alternative methods like plasma welding or spot welding.
The table above should give you a quick overview of its suitability for various materials.
Consumables in Submerged Arc Welding
Types of Wires:
- Solid Wires: These are generally used for non-ferrous metals and are straightforward with no special filler material.
- Filled Tubular Wires: These contain a flux or metal powder in a thin metal tube. This design brings a combination of filler metal and flux to the weld, making it quite efficient.
Types of Fluxes:
- Acid Rutile, Semi-Basic, and Fully Basic: These flux types correspond to the acidity or alkalinity of the flux, affecting its stability and suitability for different metals.
- Fluxes for Specific Metals: Some fluxes are designed specifically for Mild Steel, Low Alloy Steel, Stainless Steel, and Nickel Alloys. Matching your flux to your material will significantly improve weld quality.
- Current: Adjusting the current can affect penetration and the amount of heat introduced into the metal.
- Voltage: This controls the length of the arc. A higher voltage will lead to a longer arc and vice versa.
- Travel Speed: This determines how fast the welding is completed. Faster travel speed can be efficient but risks lack of fusion.
- Electrical Stick Out (ESO): ESO is the length of the unwelded electrode extending from the tip of the contact tube. This can affect weld quality significantly.
- DC+/DC- or AC: DC+ results in deeper penetration, while DC- yields less penetration but more electrode melt-off. AC is somewhere in between and can be more forgiving.
- Constant Voltage (CV) Mode: Provides a stable arc but requires more manual intervention.
- Constant Current (CC) Mode: Adjusts the voltage automatically to maintain a steady current, offering a more controlled weld.
Areas Where SAW Shines:
- Shipbuilding: Given the size and scale, submerged arc welding is often the method of choice.
- Offshore Wind Turbines: The need for high-quality, long-lasting welds makes SAW ideal here.
- Automotive and Aviation: These industries require high-strength, reliable welds, and submerged arc welding often fits the bill.
- Nuclear Power Industries: Here, the quality and consistency of the welds are paramount, and SAW offers just that.
- Pipes and Penstocks
- Boilers and Pressure Vessels
- Structural Shapes
Limitations and Tips
What to Watch For
- Limited Positions: Unlike some other welding methods, SAW is limited to flat or HV positions.
- High Costs for Small Jobs: Because of the equipment involved, SAW can be costly for small-scale jobs.
- Quality of Flux: Always opt for high-quality flux to avoid issues like electrode wire curvature, size maintenance, and centerline cracking.
- Suitable for circular welds and allows one-side welding for complete root penetration.
- Mind the duty cycle to avoid overheating your equipment.
Advantages and Disadvantages
- High-quality welds.
- Faster operation.
- Minimal welding fume and spatter.
- Positional limitations.
- Not ideal for thin materials.
|Weld Quality||Excellent||Not suitable for all positions|
|Material Types||Highly Versatile||Limited to thicker materials|
|Speed||Fast||Slow for small, intricate jobs|
|Safety||Lower risk of “arc eye”||Requires additional flux management|
This table should give you a quick comparative understanding of the strengths and weaknesses of submerged arc welding.
Cladding Using Submerged Arc Welding
Types of Materials Commonly Used
- Chromium Carbide: Highly wear-resistant and ideal for applications where durability is required.
- Nickel-based Alloys: These offer excellent corrosion resistance and are often used in chemical processing industries.
Submerged arc welding offers a reliable and efficient welding process ideal for heavy-duty projects. While it has some limitations, its benefits in speed and quality make it a valuable method in various industries.
This guide aims to provide you with comprehensive insights into SAW, equipping you to make informed decisions for your welding needs.