Spray arc is a spatter-free mode of metal transfer during welding through MIG. In this process, the electrode or wire melts in a fine mist with a metal drop smaller in diameter than the wire’s diameter. This high voltage and high amperage welding require a continuous arc supply as well. Welders idealize this process for thicker metals especially for welding butt and filler joints. The other welding methods usually yield sparks and spatter, but you’ll be pleased to know that this process is somewhat a ‘clean’ process.
List of Contents
- Spray Arc Welding Process
- Shielding Gas for Spray Arc Welding
- Pulsed Spray Arc Welding
- Thermal Spray Arc Welding
- Applications of Spray Arc Welding
- Tips for Spray Arc Welding
- Spray Arc Welding Vs Short Circuit Welding
- Spray Arc Welding Vs Globular Arc Welding
- Spray Arc Welding Vs Flux Core Welding
- Frequently Asked Questions FAQ’s
Spray Arc Welding Process
The process is quite simple, i.e., the wire is brought close to the base metal or workpiece. Because of high voltage and amperage, high-current travel in the wire, which melts it. A spray of molten metal droplets moves along the arc and lays on the base metal. Therefore, this contact-less metal transfer is called the spray method.
If welders apply a wise combination of shielding gas, metal, and wire radius, they can achieve high metal deposition rates. The wire or electrode diameter is of great significance because the metal droplets must be in the specific range for professional welds. A high transition current can also be gained by modifying these conditions in view, which is the minimum current required for spray arc welding.
For different metal types and filler electrodes, there are different transitions current. Let me tell you; transition current is a threshold; you need to have more welding current value to have a ‘spray’ arc.
Apart from efficiency and good impact strength, spray arc welding has many perks. Some of them are as follows:
- High metal deposition rates
- Minimum or no spatter
- Fine weld bead appearance
- Larger diameter electrode wires can be used
- Superb metal fusion and penetration
You might be quite satisfied to use this method, but wait, it has some limitations.
- Spray arc welding is suitable for thick metal sheets. (about 1/8 inches or 3mm).
- Moreover, the weld pool forms because of high heat levels. Hence, you can use this method for horizontal or flat fillet weld positions.
- Unfortunately, there are no available open capabilities in this welding. Hence, you cannot join complete penetrations joints.
One of my fellow welders applied 28 Volts and 200A current for spray transfer with 0.035 inches wide wire. High current makes the arc extremely hot, so thin materials are probable to melt. The large weld pool also limits this welding’s scope, so various joint types and positions are impossible.
Shielding Gas for Spray Arc Welding
Mostly, spray arc MIG welding is used for welding aluminum and stainless steel. And we can not use CO2 for these metals. Stainless steel can easily rust, and welders face embrittlement issues because of the formation of chromium carbide. The same is the case with aluminum, and it is also sensitive to air because of aluminum oxide formation.
As a result, pure Argon gas is used as a shielding gas for spray arc welding. You have to keep your budget accordingly because pure argon tanks are a bit expensive. To combat this financial problem, welders prefer to use tanks with combinational ratios of CO2 and Oxygen but not more than 25%.
Here are the following gas combinations that we used for spray arc welding from my and my mate welders’ experiences.
- Any gas mixture with more than 75% Argon tanks can be used for shielding while welding carbon steel.
- And C2 gas or 98% pure Argon with 2% CO2, or a tri-mix gas like 90% Argon, 2% to 10% CO2, and up to 5% oxygen for stainless steel welding.
- Pure Argon or Helium suits best as a shielding gas for aluminum or heavy metals.
- Shielding gas for some flux core wires is pure CO2 while for others 75% Argon and 25% CO2 mixtures.
How to choose the right shielding gas
Now, keep the following factors in mind as well while choosing the gas for you:
- Required efficiency and filler metal deposition rate
- Bead profile
- Desired penetration
- Weld positions
- Other weld process technicalities
Pulsed Spray Arc Welding
Pulsed Spray is a modified spray arc welding. In this process, the welding current or voltage values are varied between the peak values and low background current or voltage with a frequency of 30 to 400. As a result of this variation, the molten metal spray is done periodically, while in spray arc welding, it is continuous.
The peak current produces metal spray, and the low background current produces a low heat input at which metal transfer does not occur. Moreover, during the low current, the weld pool also gets a little time to freeze, hence preventing burn-through.
Advantages of Pulsed Spray Arc Welding
This technique, being a modified version of spray arc welding, provides the following facilities:
- Control on weld pool
- lower heat input
- Almost no spatter
- Aesthetically improved welds and better weld beads
Thermal Spray Arc Welding
Thermal spray arc welding is similar in process to spray arc welding. Welders use this process to repair material surfaces. Thermal spray welding is also called ‘metalizing’. In thermal Spray, a fine mist of molten metal drops on the metal as a coat. For better and professional results, multiple coating is a good idea. This process’s main purpose includes repairing worn-out components and machine parts and providing resistance to wear, corrosion, abrasion, or heat.
Applications of Spray Arc Welding
Spray Arc Welding includes many industrial applications.
- Manufacturing of molds for plastic components
- Making of electronics component housing with a conductive coating
- Arc sprayed coatings are useful in large structures to protect them from corrosion or other hazards.
Tips for Spray Arc Welding
- Always remember you need to set your machine at high voltage and amperes to get spray arc welding. The maximum ampere value for this welding is 220A. Welders recommend keeping voltage above 25V for spray transfer to occur.
- Select your gas mixture according to the base metal and electrode wire datasheet.
Spray Arc Welding Vs Short Circuit Welding
A short circuit is also a method of metal transfer in MIG welding. This transfer happens at low voltage and current of few amperes. In this mode, the wire electrode comes in contact with the base metal, and excessive heat is released as a short circuit occurs.
This heat melts the electrode to form the joint. At the same time, spray arc welding is a contact-free process and occurs at high voltage and amperes. The former one involves messy spattering, while spray transfer produces less spatter. Additionally, the arc is continuously on during the spray type transfer.
Spray Arc Welding Vs Globular Arc Welding
In globular arc welding, gravity helps in metal transfer by accelerating the large globules of molten metal electrodes into the bead. Prompt short circuits occur with the weld pool during short-circuiting metal transfer. The rate of globular transfer depends on welding current, applied voltage, shielding gas, and electrode type.
On the other hand, no gravitational effect is needed for metal transfer in spray arc welding. Because of the recursive short-circuiting with weld pool, the spatter probability is comparatively higher in globular arc welding.
Spray Arc Welding Vs Flux Core Welding
The flux core welding involves a tabular wire which is hollow and fills with flux during the process. In contrast, the spray transfer process uses a solid wire as an electrode. Both of these welding methods are suitable for welding thick materials. Flux core welding is used for heavy-duty and industrial applications.
Frequently Asked Questions FAQ’s
What is spray transfer in MIG welding?
Spray transfer is a metal transfer mode from the electrode to the base metal in a fine mist. The high amperage provides enough heat to melt the electrode before its contact with the base metal. Therefore, the molten droplets travel through the arc and lay down on the workpiece.
What is the best shielding gas for Spray arc welding?
Pure Argon is the best shielding gas for spray arc welding. Usually, welders recommend using gas mixtures with a high percentage of Argon or Helium with a smaller ratio of other gases. According to statistics, the gas mixture must contain at least 80% Argon.
How do you perform spray transfer welding?
Spray transfer welding is also known as spatter-free axial Spray. Set your machine at high voltages and amperage enough to produce a metal spray. Try to prefer this welding technique for butt and fillet joints with considerable thickness. This spray welding is best for vertical and horizontal positions.
conclusively, spray arc welding is the most suitable metal transfer method in MIG for stainless steel and aluminum. It produces minimum spatter as compared to other welding processes. Welding thick materials are way easier with spray arc welding, but it limits welding positions because of its high heat inputs.