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Beyond the Weld: Quality Assurance in Pressure Vessel Welding

20 February, 24 9:25 am · Leave a comment · Red-D-Arc
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Quality assurance is a critical factor for any pressure vessel welding job. Pressure vessels pose a significant danger to everyone working or living around them, as they can explode if they aren’t fabricated to meet code criteria. Quality assurance involves weld testing to ensure the welded seams meet the requirements for a safe and long pressure vessel service life.

Pressure Vessel Fabrication and Inspection Codes

Pressure vessels, boilers, and heat exchangers are subject to welding codes and standards. All US states have legislated the requirement to manufacture pressure vessels according to the ASME code. But rules can vary from state to state, depending on many factors like climate. High/low temperatures, moisture, and marine environments influence the design and fabrication requirements, so you should always ensure you are fabricating and testing the pressure vessels to meet your local law requirements on top of meeting your client’s expectations.

ASME Boiler and Pressure Vessel Code (BPVC)

“ASME” is the name in the pressure vessel industry. But, when people say “ASME” in the pressure vessel context, they are actually referring to the American Society of Mechanical Engineers (ASME) and their Boiler and Pressure Vessel Code (BPVC). This massive code consists of over 30 books with over 17,000 pages, but the following are the most important for welding and inspecting the pressure vessel welds:

These standards contain rules for the design, fabrication, welding, and testing of welded pressure vessel assemblies. Likewise, they contain rules for the qualification of personnel and the responsibilities and duties of authorized inspectors.

Being an “ASME code shop,” or an “authorized shop” as many refer to, simply means that you are certified to perform pressure vessel welding according to the ASME code. You would need to enter into a contract with an authorized inspection agency and have a dedicated authorized inspector. The inspector would often interact with your shop as you conduct your business producing ASME pressure vessels. 

Being an authorized shop brings many benefits, including better access to the market and allowing you to stamp the ASME mark on your pressure vessels. However, this requires rigorous quality assurance for every pressure vessel to ensure a high weld quality for safety and compliance with the code.

The National Board of Pressure Vessel Inspectors

Another critical organization for pressure vessel safety is The National Board of Pressure Vessel Inspectors. They develop standards, training programs, and certifications for the construction, installation, repair, inspection, and repair of pressure vessels and boilers. 

There are also other bodies, including the American Petroleum Institute, that develop codes for pressure vessel fabrication and testing. But, the ASME is the most critical code for most applications.

Quality Assurance From The Get Go

“Staying vigilant in the pre-welding phase can save significant resources and prevent rework or penalties”

Quality Assurance Plan (QAP) forms the framework for activities before, during, and after the fabrication process. So, quality is ensured from the very beginning. Some of the most critical pre-welding quality control steps are:

  • Verifying welder qualifications for specific weld types, materials, and positions.
  • Ensuring that the welding equipment is set for meeting the WPS requirements.
  • Reviewing WPS documents to ensure accuracy and completeness.
  • Conducting tests on weld coupons as needed to verify WPS qualification.
  • Ensuring compliance with industry standards and requirements for base metals and welding consumables.
  • Checking joint cleanliness and proper fit-up during the inspection process.
  • Verifying that joint design and weld preparation meet WPS and applicable welding standards (ASME, AWS, API).
  • Reviewing clearance dimensions of rings, consumable inserts, or backing strips as needed.

Staying vigilant in the pre-welding phase can save significant resources and prevent rework or penalties, depending on the situation and the job. Missing a critical error can mean a complete profit loss or worse. That’s why spotting irregularities early on is so important for long-term welding shop success, especially in the pressure vessel industry. 

Welding pressure vessels involves many people: metallurgists, engineers, authorized inspectors, welding personnel, production managers, and the sales department that stands between you and the customer. So, if a critical step is missed or done incorrectly, you might get into a situation where lots of people have to re-do their jobs, inspect the newly present situation, and decide on how to proceed. This can lead to delays and profit loss, which is why quality assurance early in the process not only ensures pressure vessel safety, but hitting the deadlines and achieving the projected profitability.

Non Destructive Testing (NDT) For Pressure Vessel Welds

Welding the pressure vessel is only part of the job. Making sure those welds will actually hold is another thing entirely. 

While quality assurance includes welder, welding procedure, and material qualifications, the produced welds must also be inspected. 

All welds are first inspected visually. An experienced certified welding inspector (CWI) can easily spot many discontinuities and weld flaws from the visual inspection alone, which can save the effort and time of performing the NDT if the welds aren’t up to the visual standards. However, once the welds pass the visual test, they also must pass NDT tests like X-ray, ultrasound, and other NDTs appropriate for the pressure vessel at hand.

All NDT testing should be done with a turning roll system to ensure operator safety and convenience, especially when dealing with very large pressure vessels. The operator must apply radiographic imaging, ultrasound probe, or other equipment over the circumference of the pressure vessel. But, this can require the operator to get underneath the pressure vessel or work at an awkward angle, which can be extremely dangerous with heavy equipment. Welding turning rolls allow the rotation of the pressure vessels so that the relevant part of the wall always faces the operator, ensuring easy and safe welding and testing. 

Radiographic Testing

Radiographic testing is applied to all critical welds on pressure vessels, like butt and seam welds, to ensure weld penetration and quality. Radiography sends X-rays or gamma rays into the weld, creating an image that captures even the tiniest of weld defects. RT can spot voids, dents, cracks, porosity, changes in material thickness, and other weld discontinuities and defects.

Radiation is a safety hazard, and RT requires skilled technicians, but this is the most widely adopted weld NDT method that’s especially useful for pressure vessel testing. RT provides hard evidence in the form of a film rather quickly, while digital radiography can give you results on screen in seconds. 

Ultrasonic Testing

Ultrasonic testing detects weld discontinuities and defects such as cracks, inclusions, and thickness variations in a pressure vessel’s material. It involves sending high-frequency sound waves into the material and measuring the time it takes for the echo to return. As these waves travel through the weld, they will reflect back some energy if they hit a weld discontinuity, which is what the operator is looking for.

UT is more challenging to perform and requires a highly skilled operator. It’s also slower than RT, but it can be a preferred method, depending on various inspection and weld factors.

Magnetic Particle Testing

Magnetic particle testing is only suitable for evaluating ferromagnetic materials. But, the equipment is inexpensive and portable. By subjecting the surface to a magnetic field and introducing magnetic particles, any defects or fissures will attract the magnetic particles. Under proper lighting conditions, even the most minuscule imperfections become visible and easily identifiable. However, operators can use fluorescent magnetic inks to improve visibility and flaw detection. 

MT testing can only detect surface weld discontinuities. It’s not the best way to inspect the weld quality deep in the material. 

Liquid Penetrant Testing

Liquid penetrant testing is also applied to test surface-level weld discontinuities. It’s a great way to quickly inspect for cracks, laps, cold shuts, laminations, porosity, and other weld defects. Results are very easy to read, so less operator training is required. 

PT works by applying a liquid penetrant to the surface, waiting for it to penetrate into discontinuities, and removing it from the surface. Next, another substance is applied, which draws out the penetrant trapped in the cracks and other discontinuities, making them easy to spot visually.

Hydrostatic Testing

Pressure vessels, boilers, storage tanks, and piping systems are also subject to hydrostatic testing after the vessel is completed or repaired. Hydrostatic testing is performed by filling the vessel with water and pressurizing the system up to 1.5 times the design pressure limit. The water can also be dyed to help spot any leaks.

Critical Weld Defects

The NDT methods are used as a part of a quality assurance protocol to prevent critical weld defects from jeopardizing the safety of pressure vessels. Some of the most detrimental weld defects for pressure vessels are described below with their associated dangers.

  • Cracks – It doesn’t get worse than weld cracking for pressure vessels. Transverse, longitudinal, or crater weld cracks can propagate and lead to catastrophic weld failure and pressure vessel explosion. 
  • Burn-through – Excessive welding current or inadequate welding speed can cause the burn-through and deterioration of the welding joint. As a result, the weld can get compromised as not enough root material is left.
  • Inclusions – Tungsten, flux, slag, and oxides can get trapped in the weld as inclusions and negatively affect the weld strength. They are usually easy to spot in NDT. 
  • Excessive weld reinforcement – A highly problematic weld discontinuity because it can cause stress concentration at the toe of the weld, leading to an increased chance of weld rupture.
  • Incomplete fusion and incomplete penetration – Both are severe weld defects that can lead to pressure vessels being unable to withstand operating pressure, causing failure and explosion.
  • Porosity – Usually caused by inadequate shielding from the gas or flux or from the shielding agent contamination. Weld porosity manifests as trapped bubbles deep in the weld or on the surface and weakens the weld’s integrity.
  • Overlap – A condition where a weld metal extends beyond the weld toe or root without fusing and creates a mechanical notch parallel to the weld. This is a serious issue that usually calls for weld rejection. Overlap usually means weak fusion, which is a big problem for vessels experiencing pressure and temperature swings.
  • Undercut – Occurs when the weld face or root surface is below the adjacent base metal surface, which can significantly weaken the joint.

Red-D-Arc – Your Trusted Partner For Industrial Welding

Whether you repair or manufacture pressure vessels or are considering venturing into this highly lucrative industry, we have the equipment you need. Pressure vessel fabrication requires specialized turning rolls, fit-up bed equipment, seam welders, and welding manipulators in order to achieve maximum productivity and fast turnaround times. 

Contact us today, and our team of experts will help you choose the most appropriate weld automation equipment and power sources for the job you are looking to bid or take on. 

 

How to Weld Cast Iron: MIG, TIG, Stick, and Arc Welding

08 December, 23 9:21 am · Leave a comment · Red-D-Arc
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When you think about welding, you likely think primarily about steel. Steel welding is by far the biggest use case for welding around the world, but it’s also far from the only kind of metal being joined with welding.

Cast iron is also common, but it presents its own unique challenges.

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Tips for Mechanical Contractors: Choosing the Right Welding Equipment for Your Projects

18 October, 23 1:41 pm · Leave a comment · Red-D-Arc
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Mechanical contractors weld everything from HVAC sheet metal to process piping and pressure vessels. Welding mechanical equipment and piping systems requires the utmost precision and quality to meet code requirements and client expectations. At the same time, contractors must be highly efficient and productive to stay competitive and improve their bottom line.

This article will help you choose the best welding and cutting equipment for your mechanical contracting projects. With the right gear, you can be more productive and achieve exceptional results for your clients.

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Mig vs. Pulsed Mig vs. Doubled Pulsed: What’s The Difference?

12 June, 23 9:05 am · Leave a comment · Peter Germanese
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Metal Inert Gas welding, also known as MIG, has seen some great innovations over the last 40+ years.

Modern technology facilitates some excellent new techniques to help with making the process cleaner, more effective, faster, and stronger. What’s not to love? 

Let’s dig in.

MIG Welding: How it Works

Basic MIG welding is fairly simple. You have a torch with a wire feeder, and the wire acts as the electrode for an electric current. The electrode conducts the arc into the workpiece, melting in the process and becoming part of the weld pool along with the workpieces. Together, they solidify into a weld, ideally free of pocks or inclusions, and stronger than the original materials.

Image source: https://technologystudent.com/despro_flsh/mig1.html

MIG comes in two forms: short circuit and spray. In order to understand pulsed MIG, you need to know how these two variations work and their pros and cons.

Short Circuit MIG Welding

Short circuit MIG welding is the simplest kind of MIG welding. With this form of the process, the workpiece is grounded by using a ground clamp.

 

Electricity pushed into the welding torch flows to the electrode and, when the electrode touches the workpiece, short circuits through the ground. This flash of arc heats up and melts the electrode until enough of it melts away that the circuit breaks, leaving a molten pool of metal where the electrode contacts the workpiece.

In another process, like stick welding, you would then need to manually adjust the position of the welding torch and the stick of filler metal and tap again to create the circuit arc and melt more metal into the next bit of joint. However, with MIG machines, the wire electrode is fed in automatically, creating a constant, repeated short circuit and allowing you to weld much more quickly and evenly.

Image source: https://www.sciencedirect.com/topics/engineering/short-circuiting-transfer

All of this is protected from inclusions and contamination via the use of shielding gas. The result is, ideally, a solid weld with metal free of inclusions and other problems.

The biggest benefit of short circuit MIG is that it can be used in any position, including vertical and overhead. Because each “tap” of the circuit is brief, the weld pool doesn’t stay molten for long, and there’s no continuous arc that can make things more dangerous for an operator.

Unfortunately, short circuit MIG has one significant problem: it’s messy. Each short circuit is a tiny explosion of power and that creates an outward force, creating a spatter. This kind of MIG welding is very easy to learn and is a common “basic” protocol, but it requires a bunch of cleanup and rarely looks good in its base form.

It’s very functional, though, and can be used on any thickness of steel.

Spray MIG Welding

The alternative to short circuit MIG welding is spray MIG welding. It was first developed when someone asked the question: “What happens if you crank up the speed of the wire and the voltage of the welding machine?”

The answer: the arc is created before the electrode even has a chance to contact the workpiece due to the higher voltage. Faster wire feed speed causes the electrode to melt almost before it leaves the torch, and the resulting molten metal is literally sprayed via the powers of electricity, the shielding gas, and gravity to the location of the weld.

In a way, you can think of the difference between these two as sort of like the difference between painting a surface using a brush versus using spray paint, though the analogy isn’t actually very accurate when you consider the mechanics behind them.

Spray transfer MIG has a number of distinct advantages over short circuit MIG welding. Primarily, it’s much cleaner; there’s no spatter to deal with, and it can be used on aluminum because of the comparatively lower heat at the site of the weld. It requires a more-pure shielding gas (usually 90%+ Argon) to achieve a quality and consistent spray.

There are, unfortunately, a few downsides to this process as well. Though it is cleaner and more effective on certain materials than short circuit transfer, the fact that the molten metal from the electrode is literally spraying across open air means that the process can’t be used in vertical or overhead positions. Trying to do so will result in poor quality transfer as much of the molten metal falls back down or drips, leaving shallow, inconsistent welds and risking burns or injuries to the operator.

Enter Pulsed MIG Welding

This is where pulsed MIG welding comes into play. What is it, though?

Imagine if you could get flexibility in the positioning of short circuit welding but the cleanliness and speed of spray transfer out of one single process. It’d be great, right? Well, luckily, you can.

Pulsed MIG welding was first developed in the 1980s using advancements in electronic control technologies.

Instead of having one solid amperage across the board while you’re welding and controlling the frequency of contact/arc via the speed of wire feeding, pulsed MIG uses electronic components to set two amperages; a peak amperage and a background amperage.

The background amperage is a lower amperage that is the baseline minimum your machine puts out at all times. This “flickering” of the voltage has a few effects.

First, the background amperage never dips below a determined minimum. This provides a solid baseline and enforces a constant arc while reducing the overall amount of heat going into the weld puddle. This is how it can be used in positions other than horizontal, and it makes it flexible enough to use overhead.

The peak amperage, meanwhile, is the higher amperage necessary to flash-melt and spray the electrode as you would in spray transfer. This gives your weld bead the cleanliness and consistency of a spray transfer without the limitations caused by high heat in a standard spray.

Unlike traditional spray transfer that is primarily controlled by rapid wire feed speed, pulsed MIG welding uses electronic components to create a square wave in the electrical current, with a frequency (measured in hertz) of anywhere from a few times per second to hundreds of times per second.

The biggest drawback to pulsed MIG is that it requires a highly skilled operator. While the process itself is not difficult, knowing how to set the base and peak amperages, feed speed, gas flow rate, and other settings requires a lot of experience or a solid reference document for consistent projects.

At least, that was the case in the 80s, 90s, and early 2000s. In modern times, the operator doesn’t need to have an encyclopedic knowledge of various factors and configurations to use pulsed MIG as a process.

Modern MIG machines have a wide range of programs that can be selected based on key attributes of a configuration, essentially allowing an onboard computer to do the thinking for you.

This has made pulsed MIG infinitely more accessible to casual operators and has made it often a go-to process today.

What is Double Pulsed MIG Welding?

If pulsing the current is good at making a welding process more effective, what if you pulsed it again?

While this might sound like pseudoscience nonsense, it’s actually easily achievable with signal alterations and is done in a wide variety of settings with a wide range of technologies. It’s not limited just to welding, not by a long shot.

One of the features of a square wave is that an additional square wave of another frequency will add and remove from the base square wave. While in uncontrolled signals, this amounts to noise, it can be highly beneficial when carefully controlled.

For example, check out this signal diagram. In this diagram, you can see the primary square pulse, with the blue upper amperage and the orange lower amperage. However, throughout the entire signal, there’s a smaller square wave at a higher frequency that adds and removes from the base signal.

To put it in numerical terms, you might have patterns like these:

  • Single Pulsed: 10, 5, 10, 5, 10, 5, 10, 5…
  • Double Pulsed: 10, 9, 10, 9, 10, 5, 6, 5, 6, 5, 10, 9, 10…

This additional pulsing of the electrical current allows the welding machine to give the operator even more exceptional control over the weld bead. In fact, the welds it makes can look almost like TIG welds, with that characteristic “stack of dimes” appearance that is so sought-after aesthetically in many welds.

Unlike TIG, a double-pulsed MIG still uses a consumable electrode and still results in the basic spray transfer operation, along with the faster transfer speeds of MIG over TIG.

This leaves you with a strong, solid, and highly aesthetically pleasing final weld bead.

The greatest downsides to double-pulsed are similar to what single-pulsed used to be; that is, it’s very complicated and requires a lot of knowledge to set properly. With so many settings and configurations that need to be exactly right, it’s very easy for a project to fail because of an improper setting.

As such, many double-pulsed machines actually “fix” some of the settings. The secondary pulsing, for example, might be locked or might only be toggled between a couple of standard settings as designed by the developers of the machine.

Of course, the development that goes into creating these settings, and the computerization required to control the configuration, means that welding machines capable of double-pulsed MIG welding tend to be much more expensive than machines capable of single-pulsed or basic no-pulsed MIG welding. The increases in efficiency and speed can be worth that added cost, but the startup costs and training required to do it are much steeper.

Why Isn’t Double-Pulsed MIG The Standard?

Given all of the advantages of double-pulsed MIG, you might wonder why it isn’t standardized yet.

The answer comes from several different angles.

The first is that, as a relatively new development in MIG technology, it’s both somewhat expensive and in need of more testing and development. That’s not to say it’s dangerous – no more so than any welding process, and less than some – but that companies still aren’t entirely sure of what the best configurations are for specific tasks. Some tasks may also fall outside of standard configurations, which means operators might want unlocked machines, which have many more potential points of failure.

Similarly, many companies are coming at the process from different angles and with different forms of development. That means machines you get from one company may not share settings or configurations with other company machines, and even the terminology is different. In part, this is due to different development processes, but it’s also in part just companies trying to find a name that catches on so they can claim it as their trademark.

At the same time, welding as an industry is rarely quick to embrace change. There are many old hand operators out there who insist on stick welding as the best process. Whether it’s resistance to change, resistance to the expense of new machines, or simply a desire to wait to see what settles out as the “best” option, many shops are hesitant to invest in the newest technologies.

That said, double-pulsed MIG, used in conjunction with welding automation systems and even computerized fabrication machines, can create exceptionally consistent end products with fast throughput, efficient use of electrode wire and other consumables, and other benefits.

How to Get Started with Pulsed MIG Welding

The best way to get started with pulsed MIG and double-pulsed MIG is to obtain a welding machine that can handle it and simply give it a try. You don’t have to outright buy a new welding machine, however.

That’s where we come in. Our welding equipment rentals offer the option to try anything before you spring for a full purchase. And, if you like what you try, you can even buy our used welding equipment.

Whether you need small-scale welding equipment for a single shop or a complete, automated solution for spinning up a fabrication facility, we’ve got you covered. Reach out and talk to our sales and service teams to set you up with the solution to any welding needs you may have at any scale.

Weld Aluminum with a MIG Welder

01 February, 23 2:16 pm · Leave a comment · Red-D-Arc
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 is not the only process capable of producing high-quality welds on aluminum alloys. The high degree of control that the process provides makes it well-suited to tackling very thin materials, but as material thickness increases, the relatively slow speed of the process becomes more apparent. When ease-of-use and cost-effectiveness are prime considerations in an aluminum welding application, many fabricators choose to implement MIG (GMAW). While the process fundamentals are unchanged from MIG welding steel, MIG welding aluminum requires some specialized equipment and additional care to achieve high-quality results with minimal frustration.

Delivering the Aluminum Wire

Much of the additional care required is focused within the wire delivery system, since the lower columnar strength of aluminum wire makes it susceptible to burn-back and bird’s nesting. MIG welding aluminum typically requires fabricators to choose between “push-pull” or “spool gun” welding torches.

The Push Pull Gun:

  • Ideal when the workpiece can be brought within 15-25 feet of the power source 
  • Advantages: Lighter and more maneuverable; can utilize wire packaging of any size (meaning reduced changeover cost)
  • Disadvantages: Reduced forgiveness to compounding issues in the feeding system
  • Example: Spoolmatic 30A Spool Gun

The Spool Gun:

  • Ideal when the workpiece cannot be brought close to the power source
  • Advantages: Improved forgiveness in the wire feeding system
  • Disadvantages: Less ergonomic; use is limited to 2# spools (meaning increased changeover cost).
  • Example: Miller XR-Aluma-Pro Push-Pull Gun

Regardless of the MIG welding gun being used, it is critical to ensure that the MIG consumables used are properly sized and in good condition. For example, both gun types require contact tips. Ensure that the wire diameter stamped on the contact tip matches the wire diameter being used and that the contact tip is inspected periodically for the formation of a keyhole shape at either end that is an indicator of wear. As the contact tip wears, micro-arcing between the contact tip and wire can lead to costly burn-backs that are prevented by a quick change of consumables.

A typical carbon steel MIG welding setup will typically use steel liners, brass inlet and intermediate wire guides, and either V-groove or V-knurled drive rolls. Users of a push-pull gun will need to go beyond simply changing contact tips. When MIG welding aluminum, it is important to use ALL the following: U-groove drive rolls, Teflon inlet and intermediate wire guides, and Teflon liners. Ensuring that these components are properly installed (and dedicated for aluminum use only) will help to minimize the potential for wire shaving that can cause the liner to become clogged and complicate wire feeding. Likewise, users of bulk wire packaging such as drums should carefully read the drum’s set up instructions and carefully consider the drum placement and conduit routing to help keep the overall “drag” in the system as low as possible.

Selecting Aluminum Welding Parameters

As with welding steel, it is possible to weld aluminum using one of several “transfers” depending on the specific wire feed speed and voltage combinations used. 

  • Thin materials typically require a short circuit transfer that is the result of low wire feed speed and low voltage. These “low” settings help to minimize penetration to prevent burn-through from occurring. Attempting to use short-circuit on thick material without proper base metal preparation may lead to lack-of-fusion defects.
  • Thicker aluminum is best welded using a spray transfer. The higher wire feed speeds and voltages required to achieve the stable spray transfer provides additional penetration. Attempting to use spray transfer on thin aluminum will require significantly higher travel speeds than when welding using short-circuit.

Aluminum & Modern Pulsed Waveforms

“Pulse” is a feature found on many modern power sources where the output of the power source is “pulsed” between a low “background” and high “peak” current. By offering the “best of both worlds”, pulsed waveforms are beneficial when welding a wide range of common aluminum thicknesses. Using thinner material as an example: the “peak” current maintains a stable arc when welding at the “low” settings needed for thin material while the “background” current helps to keep overall heat input low to further minimize the risk of both distortion and burn-through.

Looking through a welder rental supplier’s catalog will reveal that there are many choices to be made when selecting aluminum MIG welding equipment. Consult with these experts to learn which combinations are best for your application; they may even have MIG welding packages which can help to alleviate some guesswork by bundling popular options together.

Before pulling the trigger, make sure to purchase some 100% Argon (or 75% Helium/25% Argon shielding gas for a little extra “punch”), set the flow rate to 35-50 cubic feet per hour, and always remove the oxide layer from the weld zone! With some modern technology and a little knowledge, achieving great results when MIG welding aluminum doesn’t necessarily have to be difficult.

Can You MIG Weld Mild Steel to Stainless Steel

30 January, 23 9:04 am · Leave a comment · Red-D-Arc
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Can you MIG weld mild steel to stainless steel? The short answer is, in most cases, yes and an ER309L filler metal is typically used. However, understanding the nature of stainless steel and MIG is helpful to best tackle this dissimilar-metal joining application. In this article we will discuss how this process is possible and what its applications are. 

Why Join Mild Steel to Stainless Steel

Mild steel, as used in this article, refers to a wide range of steel grades/compositions having a relatively low overall alloy composition. On the other hand, stainless steel has a chromium content above 11% so that the surface of the steel forms a protective layer of chromium oxide. The chromium oxide layer provides enhanced corrosion resistance compared to mild steel in many applications. Despite this benefit, there are many applications where you might mix mild steel and stainless steel. 

Cost is often the driving force behind the dissimilar joining: stainless steel is significantly more expensive than mild steel. Combining mild steel and carbon steel is one way to control the cost of a component while still ensuring that corrosion resistance is available in key areas. However, dissimilar-metal welding can sometimes be used to better allow components to carry required stresses, and in some cases, do so at a minimal component weight.

An Introduction to MIG

MIG is an acronym that represents Metal Inert Gas welding. MIG is one of many arc welding processes—processes that utilize an electric arc to melt the base metal and filler metal. A defining feature of the process is that it is a “wire-fed process” meaning that a continuously fed wire is used to maintain the electrical arc and provide filler metal into the weld joint. As the acronym suggests, MIG is also defined by the use of a shielding gas having generally inert characteristics that displaces the atmosphere from the weld zone to protect against detrimental reactions.

MIG is a very common process for welding mild steel, welding stainless steel, and welding these two metals to each other. MIG can be used with a range of shielding gasses and wire diameters to fine-tune performance for a wide range of material thicknesses. Because there is no slag, deposition efficiency (the ratio of filler metal consumed versus completed weld weight) is quite high. Because there is limited need for stop/starts and post-weld cleanup, operator factor (time spent welding versus total project time) can be much higher than other processes. These factors combine with the ability to achieve high travel speeds to produce a productive process. If you don’t currently own the equipment needed for MIG welding, welder rentals can be a way for you to become familiar with the process or tackle short-run production with limited investment.

How to Weld Mild Steel to Stainless Steel

Typically, ER309L filler metals are used to join mild steel to stainless steel. ER309L is a filler metal classification that designates:

  • That the filler metal can be used as an electrode for MIG or as a rod for TIG
  • That the filler metal has a 309 nominal alloy composition
  • That the filler metal is a low-carbon variant of the 309 nominal composition

ER309L is an austenitic stainless steel that is high in both chromium and nickel. The presence and quantity of nickel in this alloy helps to form a ductile weld microstructure. ER308/308L is a popular choice for joining 304/304L stainless steel to itself, but attempting to use this alloy for steel to stainless steel instead of ER309L may result in a crack-susceptible microstructure.

Shielding gas selection can influence the ease of welding and the quality of the results. Typically high-argon shielding gasses are used. 98% Argon/2% Oxygen or 98% Argon/2% Carbon Dioxide (CO2) are used for welding thicker materials, since these gasses help to achieve a smooth, stable spray transfer with minimal chemical interaction. Three-component gas mixtures, known as “tri-mixes”, typically consist primarily of helium with varying additions of argon and carbon dioxide. While not required for thin materials, they can offer improved performance when welding using the “short-circuit” mode of transfer commonly employed to help prevent burn-through or weld out of position.

Selecting parameters for steel to stainless steel weld joints is very similar to selecting parameters for welding stainless. The stainless filler metal requires a lower current to melt-off than mild steel filler metal, so expect to utilize lower wire feed speeds than you may be used to. Likewise, the weld pool will be more “sluggish” than when welding using mild steel filler metal, and penetration will be reduced. This means that you may need to use a wider included/bevel angle depending on the application to ensure good root and sidewall fusion. Try to avoid excessive heat input to minimize the risk of sensitization of the stainless steel base metal that can negatively affect corrosion resistance of that base metal.

Be aware that the finished weld is a mixture of alloys; the corrosion resistance of the weld metal will not be equivalent to the stainless steel base metal, and it may be important to locate these dissimilar weld joints away from sources of corrosion in some situations. Also be aware that not all stainless alloys are created equal. Stainless steel can be austenitic, martensitic, or ferritic which provides insight into their microstructure and typical compositions. Austenitic stainless steels—one of the most common types by tonnage—are generally easy to weld, while martensitic and ferritic stainless steels can be more of a challenge.

Next Steps

Contact us today to find the MIG welder that is best suited for the stainless to mild steel welding that you are looking to perform. “Sizing” a machine to your application can help you to get the feature set you need without unneeded expense. Our knowledgeable team can also provide guidance into the world of stainless steel and dissimilar-metal welding to help you select the best consumables, accessories, and knowledge.

 

Common Industry Applications of MIG Welding

19 December, 22 10:11 am · Leave a comment · Red-D-Arc
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Pound for pound of filler metal used, MIG welding (Metal Intert Gas, also known as GMAW) is one of the most popular welding processes. A key contributor to the success of the process is its versatility: it can produce high-quality welds with good productivity on a range of material thicknesses and compositions.

MIG welding uses a continuously fed wire electrode to transmit the welding arc and provide filler metal into the weld joint. The weld is protected from the atmosphere by an external shielding gas whose specific composition is often determined by the application, although as the name implies, it is largely inert.

Shop Fabrication & Manufacturing

Because shielding gas is required, MIG is not commonly used for field fabrication and repair since providing protection from draft and breeze is time-consuming and can be difficult. Instead, self-shielded processes such as FCAW-S or stick welding (SMAW) are more popular.

The welding filler metal used may be solid or tubular. Tubular MIG welding wires/electrodes are often known as metal cored wires: they are a hollow tube filled with metal alloys. These tubular filler metals have some advantages over solid wires, such as potential deposition rate/productivity, although at the expense of per-pound filler metal cost. Metal cored wires are especially common in the fabrication of heavy equipment components and structural members.

Both solid and metal cored wires produce little to no slag, post-weld clean-up time is minimal, meaning parts can often be sent to downstream processes such as painting using only a light scrub with a wire brush. This makes the process very attractive for applications that demand high productivity, such as manufacturing. (more…)

Lincoln’s Dual Maverick Diesel Engine Driven Welder

31 May, 22 12:11 am · Leave a comment · Red-D-Arc
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Lincoln’s Dual Maverick Diesel Engine Driven Welder

 

Dual Maverick 450 Engine Driven Welder

How did the Dual Maverick 200/200X get its name? When you glance at the front panel of this diesel engine-driven welder, you might start seeing double: two front panels and two sets of output lugs. As the name implies, the Dual Maverick 200/200X is a dual-operator welding power source. The 24.8 horsepower water-cooled Kubota diesel engine in the Dual Maverick has the capacity to allow two welding operators to weld independently of one another.

The alternative is to supply each welding operator with their own engine-driven welding machine, but this approach has drawbacks. Placing this extra equipment on the jobsite creates additional clutter and requires additional maintenance. Likewise, the one welder/one welding machine approach is less fuel-efficient. Lincoln Electric claims that a multi-user welding machine like the Maverick Dual 200/200X can reduce fuel and maintenance expenses by up to 33% per 1000 hours, which equates to approximately one year of “typical” use.

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Choosing the Right Welding Method When Renting a Welder

25 April, 22 3:57 pm · Leave a comment · Red-D-Arc
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Selecting the Right Welding Method

guy getting ready to mig weld
When thinking about renting welding equipment, many contractors imagine visiting a local hardware shop with a small selection of soil compactors and other basic items. In reality, today’s rental solutions are nothing like that. You can find high-quality precision machinery maintained in optimal condition, from plasma cutters to TIG rentals

With professional welder rental, companies in countless industries are able to reach their goals on time and within budget:

  • Construction
  • Manufacturing
  • Aviation
  • Oil drilling
  • Industrial pipe welding
  • Transportation
  • Automotive assembly and repair
  • Specialty production and prototyping

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MIG vs TIG Welding: Which Method Is Right for Your Application?

25 April, 22 3:28 pm · Leave a comment · Red-D-Arc
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Many businesses perform welding tasks every day, including parts manufacturers, vehicle makers, construction businesses and repair shops. People who enjoy do-it-yourself projects can handle automotive tasks or home repairs with a good arc welder. Thanks to welder rental options, you don’t even need to purchase welding equipment to get the job done.

Two popular types of arc welding equipment are metal inert gas (MIG) welding and tungsten inert gas (TIG) welding. What are the differences? How can you decide whether MIG or TIG welding is the right method for your application.

MIG Welding Process

MIG welding utilizes a welding gun with a machine-fed consumable wire. This metal wire serves as the electrode and provides the filler material for the weld at the same time.

While you work, the MIG welder delivers inert gas (usually argon) to shield the weld pool and protect the metal from contamination. The MIG welding gun automatically feeds more wire into the molten pool as you advance, so this option provides “what-you-see-is-what-you-get” welds that are easy to start, direct and control.
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Full-Featured Spool Gun for Pulse Aluminum Welding (GMAW-P) with Red-D-Arc’s New GX330XL Portable Gas Drive Welder

05 October, 21 1:55 pm · Leave a comment · Red-D-Arc Welderentals
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GX330XL Gas Engine Welder with Spool Gun for Aluminum Welding
If you’re looking for a portable, hassle free, full-featured spool gun solution for your steel or aluminum welding projects, look no further than Lincoln’s Magnum PRO 250LX GT K3569-2 spool gun for you next in-field welding job. The Magnum PRO 250LX GT connects directly to Red-D-Arc’s new GX330XL (and Lincoln’s Ranger 330MPX) without the need for additional adapters or control boxes. It’s simply a matter of attaching the gas hose, attaching the 7-pin control cable, and attaching the power cable to the output studs for .025”, .035” steel wire welding or .030”-.035” and 3/64” aluminum wire welding. (more…)

9 Tips to Help Prevent Wire Feed Problems in MIG Welders and Flux-Cored Welding

15 July, 19 12:49 pm · Leave a comment · Colin Brown
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How do I prevent wire feeding problems when using MIG welders (GMAW) or flux-cored arc welding (FCAW) processes?

Wire feed problems with a MIG welder can be caused by a variety of circumstances.  Some of the most common reasons for wire feeding issues include:

  1. Drive roll tension with the MIG Welder:  The drive rolls that push or pull the wire through the system have a tension that is either too great or too little.  Adjust the spring pressure until the tension is appropriate.
  2. Drive roll size: The drive rolls may be the wrong size.  For instance, if 1.3 mm drive rolls are being used to move 0.9 mm wire, slipping will most likely occur.
  3. Drive roll type:  Some wire requires specific kinds of grooves for optimal feeding.  Flux-cored and metal-cored arc welding wires typically require V-groove drive rolls that are knurled.  Aluminum wires require a smooth U-shaped groove.
  4. Drive roll condition:  Worn drive rolls will be ineffective at moving a wire through the MIG welder system.
  5. Liner size:  If a liner is too small for the wire it will not feed.  If the liner is too big, the wire may have too much freedom to twist inside of it, causing an unpredictable feed.
  6. Liner type:  For most wires, steel liners work excellent.  However, some wires, such as aluminum, require a nylon liner to help ensure proper feeding.
  7. Liner condition:  A worn liner will be detrimental to wire feeding.  Replace the liner if it is worn or damaged.
  8. Contact tip size:  A proper contact tip size should be used.  If the tip is too small, the wire will not feed; if the tip is too large, wire feeding and electrical conductivity may be negatively affected.
  9. Wire condition:  Not all wire manufacturers put out the same quality product.  Some wires may have thin and thick spots as well as lubricants that can cause poor wire feeding.

 

Heerema Fabrication (HFG) increases efficiency with Red-D-Arc MIG/MAG Multi-Operator Welding Packages

03 December, 14 2:42 pm · Leave a comment · Colin Brown
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 Red-D-Arc MIG/MAG Multi-Operator Welding Packages
Earlier this year, Red-D-Arc delivered several of our MIG/MAG 4-pak and 6-pak multi-operator welding packages to Heerema Fabrication (HFG) for their yards in Zwijndrecht and Flushing, Holland. HFG manufactures complex steel structures for use in the offshore oil and gas industry.
In addition to maintaining high-quality welding standards, HFG was able to increase both worker productivity and safety by employing Red-D-Arc’s multi-operator packs for the welding processes at their fabrication yards. The packs include six welding power sources and wire feeders with gas lines to accommodate up to six individual welders – and each welder has his own 115VAC power supply as well as an airline that provides filtered breathing air to the welder’s helmet. All input power, shielding-gas and breathing-air connections are made via single connections in the pak’s enclosure in order to simplify hook up as well as enhance portability.
“With the multi-packs our operators can get set up faster and start welding immediately. The time savings and increased efficiency easily covers the cost of the packs.”
After receiving their initial order of 6-paks, HFG placed a second order for 4-paks, having recognized the benefits of the system.
Red-D-Arc 4-Pak and 6-Pak MIG/MAG Multi-Operator Welding Packages are available for rent, lease or purchase. Contact Sales to learn more.

 Heerema Fabrication (HFG)

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