17 April

Five GTAW Aluminum Welding Tips for Success

Aluminum is one of the most abundant elements on earth and one of the most widely used nonferrous metals. Alloyed aluminum is popular in manufacturing industries such as transportation, aerospace, automotive, power transmission, and construction in large part because it is lightweight yet strong, corrosion-resistant, can be machined easily, is a good conductor of electricity, and it has an aesthetically pleasing appearance.

Much like titanium, aluminum has garnered a reputation for being difficult to weld, especially when using gas tungsten arc welding (GTAW). And just like with titanium, all you really need for successful aluminum GTAW is an understanding of the metal’s unique properties and the welding preparation techniques and tools you’ll need to address those properties.

1.Remove the Oxide Layer from the Aluminum

A thin layer of oxide coating, also known as a skin, occurs on aluminum naturally and melts at a higher temperature than the metal under it, which makes proper preweld base metal preparation crucial. While your AC GTAW power source does offer cleaning during the electrode-positive weld cycle, you still need to take additional steps to ensure that your metal is as clean as possible and that you’ve removed as much of the oxide layer as you can before you weld. First, start by wiping your base metal down with a soft, lint-free cloth. Next, attack that oxide layer chemically or mechanically.

Acetone was once the chemical of choice for metal cleaning. It has since been deemed unsafe to breathe even for short periods of time by the U.S. Department of Health’s Agency for Toxic Substances and Disease Registry. Other alternatives such as denatured alcohol and heavy-duty degreasers have taken its place.

To remove the oxide layer mechanically, use a stainless steel or brass wire brush to scrub the surface of the aluminum. While a stainless steel brush is often recommended, it can cause surface scarring. A brass brush cleans just as well and has softer bristles, which help minimize surface scarring. Whichever brush you use, be sure to use it for your aluminum work only. Also, store your aluminum-only brushes separately to ensure you’re not introducing contaminants into your weld.

Don’t forget to clean your filler rod as well. If you don’t take the time to prepare your base metal and filler rod, you’ll find discoloration along the outside or within the puddle itself. The weld may look smoky or have a black residue, and the weld bead won’t have that aesthetically pleasing, shiny appearance normally associated with aluminum (see Figure 1).

2.Choose the Right Shielding Gas, Blend

You probably already know that argon is the gas of choice for most GTAW applications, but did you know that helium used to hold that position? In fact, that’s why GTAW was at one time referred to as heliarc welding.

Helium provides you with a hotter arc that ionizes at a higher temperature; in other words, more power for your amperage setting and better control. But over the last several years, improvements in welding power source technology and performance, not to mention GTAW torches and flowmeters, have made welding with pure argon possible.

For thick aluminum applications in which you need an intense amount of heat but are limited by your torch’s amperage range, an argon/helium blend is the best option. Combining argon and helium can help you achieve your desired penetration, stabilize your arc, and increase your arc voltage range. Premixed cylinders of 75 percent argon/25 percent helium are available, but one drawback is that the gas inside the cylinder stratifies, minimizing the benefits of helium. A gas mixer can fix this by giving you the ability to customize the mix for your welding application, maintain the blend at your torch, and provide a consistent flow rate.

3.Learn the Truth About Tungsten

At one time pure tungsten (AWS classification EWP, color code green) and thoriated tungsten (EWTh-2, color code red) were the preferred choices for aluminum GTAW. That is no longer the case, especially because of thorium’s radioactive properties. Today rare-earth tungsten (EWG, color code sky blue) is an excellent choice for welding aluminum or any other metal. The tungsten provides good arc starting at low amperage and burnoff rates. A low burnoff rate means the tip geometry lasts longer and the tungsten won’t melt as easily, thereby minimizing contamination of the weld zone. Highly specialized welding applications may call for zirconiated tungsten (EWZr-1, color code brown), but it is expensive and not necessary unless specified in the procedure.

Whichever tungsten you select, be sure to buy from a trusted supplier. Manufacturing techniques can affect everything from the alloy blending process to the extrusion of the electrodes. Poor manufacturing quality may manifest itself as varying diameter; bent electrodes (especially in the smaller diameters); inconsistent finish; and flaking paint, which can contaminate your weld and ultimately render the tungsten electrode color-coding system useless.

To prepare your tungsten properly, use a grinder dedicated to tungsten with a diamond wheel for a consistent taper and a consistent finish on your electrode. You’ll want to prepare a 45-degree angle with a 0.010- to 0.015-in. land, or flat tip, on the end. If you don’t knock off that sharp point, that tip can easily burn off and drop into your weld (see Figures 2 and 3).

4.Select AC for GTAW Aluminum

Be sure to select AC for aluminum GTAW to take advantage of the cleaning property of the power source to remove that oxide layer. DC doesn’t offer the cleaning properties necessary to break through that oxide layer.

Newer welding machines with AC balance controls allow you to fine-tune the current depending on the thickness of the material, weld penetration, and desired cleaning area, which will affect the bead profile and the appearance of the weld itself.

5.Invest in a High-quality Welding Torch for GTAW Aluminum

With AC, not only is energy in the form of heat directed from the torch to the workpiece, it also returns to the torch. The thicker the material or the longer the bead, the more energy is returned and the hotter the torch is going to get.

An air-cooled torch works just fine on thin sheet and for short runs. A water-cooled GTAW torch operates cooler in your hand even if you are running upwards of 500 amps, depending on the torch. In other words, you won’t have to keep putting your torch down.

For the front end of your torch, a gas lens collet body with a No. 8 ½-in. gas lens nozzle is a good setup for most aluminum welding applications. The gas lens provides improved gas coverage, improved torch cooling because of the additional material (better heat transfer) in the gas lens collet body, and increased gas flow over the components (more surface area to dissipate the heat). As a bonus, the improved heat transfer contributes to longer electrode life.

Be sure you invest in a quality GTAW torch. From the copper alloy to the type of Teflon® used to make the gaskets and the silicon rubber used for the torch body, the quality of those materials affects the torch’s ability to handle heat and the lifespan of the torch itself. In addition to material quality, the manufacturing process is also important. Look for a torch manufactured with a high-temperature silver brazing process rather than soldered. Also check that the torch adheres to industry standards for fittings.

powerwelds Welding Tips

16 April

What Are The Techniques And Tips For Pulse MIG Welding?

In the world of metal fabrication, where precision and efficiency converge, a welding technique has emerged to revolutionize the industry: Pulsed MIG Welding.

With the rhythmic dance of controlled energy pulses, this cutting-edge method has taken welding to new heights, defying conventional limitations.

Seamlessly blending the power of MIG welding with the finesse of TIG, Pulsed MIG Welding has unlocked a realm of possibilities. Imagine unparalleled control, reduced heat input, minimal spatter, and flawless welds on a wide range of materials. Join us as we delve into the captivating world of Pulsed MIG Welding, where craftsmanship meets innovation, and the boundaries of metal fusion are shattered.

What Is Pulsed MIG Welding?

Pulsed MIG (Metal Inert Gas) welding is an advanced welding technique that combines the benefits of both traditional MIG and TIG (Tungsten Inert Gas) welding processes. It involves the use of a power source that rapidly switches between a high peak current for melting the metal and a lower background current for cooling and solidifying the weld. This pulsing action allows for precise control over the heat input and weld pool, resulting in several advantages.

One of the key benefits of pulsed MIG welding is its ability to reduce heat input compared to traditional MIG welding. By pulsing the current, the welder can deliver short bursts of energy, allowing the metal to cool between pulses, resulting in a cooler weld puddle. This controlled heat input minimizes distortion and heat-affected zone (HAZ) while maintaining excellent fusion.

How Does Pulsed MIG Work?

Simply put, pulsed MIG represents a modified spray transfer mode. This is a non-contact method, meaning that at no time does the electrode ever touch the weld puddle. The pulsed MIG process works by forming one droplet of molten metal at the end of the electrode per pulse.

Then, just the right amount of current is added to push that one droplet across the arc and into the weld puddle. The metal transfer of these droplets occurs through the arc, with one droplet per pulse.

During the process, the current rises to a peak when the droplet is formed. Then, in the background current phase, the current is lowered to reduce the overall heat input. It is the height and the width of the peak that is important for proper transfer.

Unlike CV (constant voltage), where current is represented by a straight line, pulsed MIG drops the current at times when extra power is not needed, therefore cooling off the process. It is this “cooling off” period that allows pulsed MIG to weld better on thin materials, control distortion, and run at lower wire feed speeds.

Why Welders Use Pulsed MIG Welding

Pulsed MIG (Metal Inert Gas) welding offers several advantages over traditional welding techniques. Most notable advantages of pulsed MIG welding:

Lower Heat Input: Pulsed MIG welding allows for precise control over the heat input. By pulsing the current, the welder can deliver short bursts of energy, followed by cooling periods. This controlled heat input minimizes distortion, heat-affected zone (HAZ), and the risk of material warping. It is particularly beneficial when working with heat-sensitive materials like aluminum.
Enhanced Control and Precision: Pulsed MIG welding provides superior control over the weld pool and allows for precise bead placement. The pulsing action creates a “stacked dimes” appearance, where each pulse creates a small, controlled weld deposit. This level of control is desirable in industries where aesthetics and precise weld profiles are crucial.
Minimized Spatter: The lower background current in pulsed MIG welding reduces the risk of spatter formation. Spatter, which is the unwanted metal splatter that can occur during welding, is minimized in pulsed MIG welding due to the controlled heat input and shorter arc-on time. This results in cleaner welds, reducing the need for post-weld cleanup and saving time and effort. Additionally, there is a significant reduction in the welding fumes creates.
Improved Arc Stability: Pulsed MIG welding offers excellent arc stability, even at low amperage settings. The controlled pulsing action ensures a stable arc throughout the welding process, reducing the likelihood of arc outages or arc wandering. This stability contributes to consistent and high-quality welds.
Versatility: Pulsed MIG welding can be applied to a wide range of materials, including carbon steel, stainless steel, aluminum, and other non-ferrous metals. It is suitable for various thicknesses and can accommodate different weld joint configurations. Its versatility makes it a preferred choice in industries such as automotive manufacturing, aerospace, construction, and more.
Increased Welding Speed: Pulsed MIG welding can result in faster wire feed speed compared to traditional MIG. The controlled pulsing action allows for higher travel speeds while maintaining excellent MIG weld quality. This increased productivity is advantageous in high-volume production environments.
Improved Weld Quality: The combination of reduced heat input, precise control, minimized spatter, and superior arc stability in pulsed MIG welding contributes to improved weld quality. The welds produced with this technique often exhibit excellent fusion, minimal weld defects, and enhanced mechanical properties.

What Materials And Sizes Can Be Welded MIG Pulse Welding?

Pulse MIG is ideal for metals and applications where controlling heat is difficult when using conventional MIG welders. As a result, pulsed MIG (Metal Inert Gas) welding can be used to weld a wide range of metals, including aluminum, non-ferrous metals, stainless steel, and mild steel. Pulsed MIG welding offers versatility in welding various metals and can accommodate different thicknesses, making it suitable for a wide range of applications in industries such as automotive, manufacturing, construction, and more.

The specific size or thickness that can be welded using pulsed MIG welding depends on various factors, including the equipment used, welding parameters, joint design, and material characteristics. However, pulsed MIG welding is commonly employed to deal with delicate and thinner metals of 5/32 inch or up to 1/4 inch.

MIG Welding Aluminum With Pulse

Pulsed MIG (Metal Inert Gas) welding is a highly advantageous option for aluminum welding. Aluminum has high thermal conductivity, which makes it sensitive to excessive heat. Pulsed MIG welding allows for precise control over the heat input. This controlled heat input minimizes the risk of distortion, burn-through, and heat-affected zone (HAZ) issues commonly associated with aluminum welding.

Aluminum welding can produce more spatter compared to other metals. Pulsed MIG welding helps in reducing spatter formation.

Pulsed MIG welding creates a visually appealing weld bead profile known as the “stacked dimes” appearance. This is particularly desirable in applications where the weld appearance plays a significant role, such as architectural structures or automotive components.

Pulsed MIG welding can improve productivity in aluminum welding. The controlled heat input and reduced spatter minimize the need for extensive post-weld cleanup, saving time and effort.

MIG Welding Stainless Steel With Pulse

Stainless steel is sensitive to overheating, which can lead to issues such as distortion, grain growth, and reduced corrosion resistance. Pulsed MIG welding provides precise control over the heat input. The pulsed current alternates between high peak currents and lower background currents, allowing the stainless steel to cool between pulses. This controlled heat input helps prevent overheating and minimizes the risk of detrimental effects on the material.

Pulsed MIG welding is versatile and suitable for various stainless steel grades, including austenitic, ferritic, and duplex stainless steels. It can be applied to different thicknesses and joint designs, making it a preferred choice in industries such as automotive, food processing, pharmaceuticals, and construction.

MIG Welding Non-ferrous Metals With Pulse

Bronze wires, typically composed of copper and tin or other alloying elements, are commonly used in pulsed MIG welding for applications where properties such as high strength, corrosion resistance, and thermal conductivity are required. Bronze wires are available in various compositions to suit specific welding needs.

Pulsed MIG is used on thin materials (eg car body panels) where low-temperature welding is essential to avoid distortion. Also commonly used on galvanized or zinc-coated steels because the weld metal does not rust, and the lower application temperature prevents disturbance (evaporation) of the zinc coating. The ability to control and reduce heat makes pulse an ideal process for brazing wires.

Can you MIG Weld Mild Steel With Pulse?

Mild steel does not present the same “thermal challenges” as other metals like aluminum or stainless, and therefore pulse does not necessarily offer the same advantages. For this reason, conventional MIG (rather than pulse MIG) is still the best process for welding mild steel in many applications – especially in the material thickness range that is achievable with single-phase machines.

Double Pulse MIG (Pulse-On-Pulse)

Double pulse MIG welding, also known as pulse-on-pulse MIG welding, is an advanced welding technique that involves the use of two pulses during the welding process. Here’s an explanation of how double-pulse MIG works:

Advancements in MIG/MAG Pulse Welding: Techniques, Benefits, and Applications

Initial Pulse: The first pulse, known as the initial pulse, is a relatively high current pulse that creates a deep penetration into the base metal. This pulse provides the necessary energy to melt the base metal and initiate the formation of the weld pool.

Background Current: After the initial pulse, a lower background current is applied. This background current maintains the arc and allows the weld pool to partially solidify. It also helps in controlling the heat input and reducing the overall heat-affected zone (HAZ).

Interpulse Time: Between the initial pulse and the second pulse, there is a brief interval called the interpulse time. During this time, the weld pool solidifies to a certain extent, ensuring stability and preventing excessive melting or distortion.

Second Pulse: The second pulse, also known as the fill pulse, follows the interpulse time. It has a lower current compared to the initial pulse and is aimed at completing the fusion of the weld pool. The fill pulse adds additional metal to the weld pool, allowing for better sidewall fusion and overall weld bead shape.

The advanced welders with douple pulse or pulse can help you with advanced settings. These pulsed MIG power sources are capable of adjusting primary and background amps, voltage, and wire feeding speed, pulse frequency, pulse balance, arc length, start and ending current, and other settings.

MIG Vs TIG Pulsed Welding

Pulse welding can be used in both MIG (Metal Inert Gas) and TIG (Tungsten Inert Gas) welding processes, but there are some key differences in how it is applied in each method. Even though the base of the pulse is the same in both processes, in MIG welding, the pulse is just a modified spray transfer process, that compliments other welding transfer modes.

TIG welding is traditionally the go-to process when there is a need to weld materials to a higher standard (quality and/or appearance) than conventional MIG. Aluminum and stainless steel are commonly welded with TIG, as these materials are often used in projects where the finish of the final product is critical

Compared to TIG, MIG pulse typically requires less skill and is easier to learn, which reduces training time. The weld quality and finish are comparable or very close to TIG in many applications.

Conclusion

Overall, pulsed MIG welding has revolutionized the welding industry by providing welders with greater control, improved efficiency, and high-quality results. Pulsed MIG machines have advantages in heat control, reduced distortion, minimized spatter, deep penetration, versatility, and aesthetics, making them a preferred choice for many welding applications. As technology continues to advance, pulsed MIG welding techniques are likely to evolve further, offering even greater capabilities and expanding their applications in the field of welding.

powerwelds Welding Tips

16 April

Advancements in MIG/MAG Pulse Welding: Techniques, Benefits, and Applications

Take an in-depth look at MIG/MAG pulse welding with this comprehensive article. Learn about the technology, benefits and various applications of MIG/MAG pulse welding that enable welders to improve the precision, efficiency and quality of their welds.

MIG Welding Aluminum With Pulse

Advantages and disadvantages of the pulsed arc compared to the standard arc

Cruising along at high speed on the freeway – in a modern sedan, you feel as if you are simply gliding along rather than putting up a fight against the centrifugal forces. It mirrors the lightness of being, and enables greater distances to be covered with ease. But what would it be like if these driving dynamics and lightness were transferred to country roads or even urban traffic?

In terms of welding technology, the spray arc corresponds to gliding along on the freeway. Its arc properties would be desirable in all power ranges and for numerous applications. However, if welders move into the dip transfer arc or intermediate arc range, depending on the power, then they will suddenly find themselves in urban traffic or back on the country roads. Welding speeds fall, penetration decreases, and any rework that might be needed increases, sometimes enormously, due to welding spatter. It gets complicated. And this is where pulse welding (impulse welding) comes to the rescue…

How the standard arc works – a technical history of pulse welding

If you want to understand the technical principles of pulse welding, first you need to understand how the standard arc variants work. What makes work easier or more difficult?

In general: When the wire electrode touches the workpiece, a short circuit occurs. To avoid a longer short-circuit phase, the current is increased, which causes the arc to ignite. The resulting heat melts the parent material and the wire end – this leads to material transfer, i.e., droplet detachment. In the low to medium power range, each detached droplet is based on a short circuit. However, over the entire power range, the characteristics of the droplet detachment vary greatly:

Dip transfer arc: In this case, droplet detachment takes place in the high current phase of the respective short circuit. As a result, the short-circuit break, i.e., the arc ignition, is explosive, which can lead to the formation of spatter. However, this is usually so fine in the lower power range that it does not stick to the parent material. Skilled welders can also exert excellent control of the dip transfer arc, as they can constantly feel direct contact with the weld pool.
Intermediate arc: The principle behind short-circuit-based droplet detachment in the high current phase remains the same in this case too. Since significantly higher amperages are already being used here, the explosions during droplet detachment are also more pronounced. Larger droplets are also formed, which are detached from the wire end without a short circuit and may therefore land next to the weld seam. As a result welding spatter is more frequent as well as larger and inevitably sticks to the workpiece – significantly increasing the amount of rework. For the welder, the intermediate arc can only be mastered with great difficulty.
Spray arc: When you eventually reach the spray arc range, the wire end is heated up more due to the high power. The droplets are also constricted around the wire end by the magnetic field generated by the current (pinch effect), becoming smaller and smaller as well as more numerous as a result, and are thus directed into the weld pool as if on a thread. The material transfer is then almost short-circuit-free. This results in a super-clean material transfer, especially at high deposition rates, which goes hand in hand with maximum reduction of spatter.

The arc thus gives welders a feeling of extreme balance and easy handling – guiding the arc, and thus joining the metals, feels “super soft”.

The pulsed arc – an electrotechnical trick

The weld properties of the spray arc would be preferable, ideally over the entire power range: super flat, isosceles seams, perfect penetration, low spattering, and of course high welding speeds. However, projecting the whole thing onto the dip transfer and intermediate arc would be impossible in the standard arc range. Instead, a little bit of electrotechnical ingenuity is required… and the result goes by the name of pulse welding.

In contrast to the standard arc, the pulsed arc is ideally short-circuit free. There is therefore no direct contact between the wire and the weld pool. The real secret lies in the oscillation between an extremely low base current and a pulse current – which has very high current values (pulse intervals). Essentially, the base current’s task is to prevent the arc from breaking and to keep the weld pool liquid. The pulse current then generates enough heat to detach the droplet and thus result in penetration.

How exactly does pulse welding work?

Important: Pulsing uses the so-called pinch effect, just like the spray arc. Unlike the dip transfer arc, the droplet is NOT detached in the high current phase. The wire electrode is melted and constricted at a certain point by applying an extremely high current for about one to two milliseconds during the respective pulse. Shortly before the current reaches the range of the low base current again, the constricted droplet is released and glides smoothly into the weld pool. With the appropriate arc length (distance between the wire end and the weld pool), there is never any contact between the wire electrode and the weld pool, which is why impulse welding is virtually short-circuit-free. It thus enables an extremely clean material transfer – exceptions prove the rule.

In addition, as per the spray arc, the droplet size is kept rather small and is approximately the same size over the entire power range, which has a positive effect on the material transfer. Only the number of pulse intervals changes and thus the number of detached droplets, with fewer pulses in the low power range and significantly more in the high power range. This can also be heard: the greater the power, the higher the tone (pulse frequency).

Advantages and disadvantages of pulse welding in practice

Heat input: The current peaks required for the pinch effect must reach a minimum of 450 amperes. Pulsing is therefore always hotter than standard welding in a dip transfer arc. This is why it is often preferred by welders for light-gage sheet metal in particular, where maximum heat reduction is required. However, the extra heat input can also be perfectly converted into higher welding speeds. Therefore, in certain sheet thickness ranges, the pulsed arc can also increase efficiency.
If, on the other hand, one approaches the spray arc range, the opposite occurs: the pulse makes it possible to reduce the heat input, especially in the high power ranges, since high currents are not permanently applied.

Disadvantages in handling: Impulse welding is based on the fact that there is no direct contact between the electrode and weld pool. Professional welders therefore talk about the advantages of dip transfer arc handling, as the continuous contact allows for better guidance of the weld pool and prevention of undercuts.

Reduction of welding spatter: It is clear to see – welding spatter is reduced by up to 100 percent due to the short-circuit-free droplet detachment and the resulting extremely clean material transfer. Pulse welding is therefore highly advisable in the intermediate arc range in particular as it saves an incredible amount of rework.

Always the same type of arc: From minimum to maximum power, the same type of arc can always be applied using the pulse function.

Advantageous for multirun welding technology: Impulse welding is perfectly suited for layer build-up.

Guaranteed flat seams

Particularly advantageous for aluminum

For users that work in the field of professional aluminum welding, a MIG/MAG pulse welder is simply indispensable. A special effect can be observed here: the dip transfer arc is often too cold due to aluminum’s high thermal conductivity. In practice, this means that welders have to configure a significantly higher welding current (wire speed) with the DTA compared to the pulse arc. This makes it much more difficult to select a suitable welding parameter. If the welding is too “cold”, the result is a seam with considerable weld reinforcement. If, on the other hand, a welding parameter that is too high is used, it results in excessive penetration (waste of filler metal).

Pulse welding can therefore help with aluminum applications, especially in the lower power range. Due to the adapted pulse characteristics, it is easy to avoid burn-through and excess penetration and at the same time to achieve a clean outflow of the molten mass for a concave seam appearance (curved inwards). A further advantage of the pulsed arc on aluminum is its cost effectiveness due to higher welding speeds and the particularly spatter-free welding results across the entire power range. The visual results are flawless and highly professional.

The right MIG/MAG pulse welding machine

The pulsed arc has been state of the art for decades in the highest quality welding systems. But impulse welding is also rapidly gaining ground even in the mid-range segment of manual welding systems. Power Welds has also responded to this market development and has added this function to the multi-process devices from the TransSteel series.

The new MIG-280P MIG welder thus features all the technology needed to meet all the welding challenges in the manual welding sector, regardless of the material.

powerwelds Welding Tips

1 April

Titanium Welding Tips：How to Weld Titanium

Titanium is a metal which is silvery gray in color and has about half the density of steel (0.163 lb/in3). Pure titanium is relatively soft has very low ultimate tensile strength. For use in structural applications titanium is alloyed with chromium and iron, chromium and aluminum, manganese and aluminum and manganese alone. These alloying elements raise the UTS of titanium from 45,000 psi to over 200,000 psi.

Welding Titanium Tips and Tricks

Alloyed titanium has high strength-to-weight ratio and excellent corrosion resistance. These characteristics are retained at elevated service temperatures of up to 800˚F [427˚C]. As expected, the high tensile strength also comes with low ductility; however, titanium can have good fatigue life provided there is absolutely no contamination.

Titanium alloys are used extensively in the marine field and in chemical processing. Their main use still remains in the aircraft industry.

Benefits of Using Titanium Alloys

As mentioned above, titanium alloys have excellent corrosion resistance and high tensile strength. Below is a more comprehensive list of its benefits.

Outstanding fatigue resistance
Excellent notch toughness
Low coefficient of thermal expansion
High strength to weight ratio – provides same strength as steel with half the weight.
Excellent resistance to oxidation at elevated temperatures.
Ability to maintain toughness down to -320˚F.
Excellent corrosion resistance
Low thermal conductivity
No scaling below 800˚F

Welding of Titanium Alloys

To successfully weld titanium many factors must be carefully considered. Most of these items are the same as when you weld carbon steel, aluminum, stainless and other metals. However, the main difference is the need to always have an inert atmosphere. This inert atmosphere is not only necessary during solidification of the puddle, but also as the weld and HAZ cool to below its critical temperature. This critical temperature is 968˚F [520˚C]; however, it is recommended that the inert atmosphere be maintained until the base metal has cooled to below 752˚F [400˚C].

TIG Welding Titanium A Guidebook That Answers All Your, 53% OFF

Oxygen and nitrogen will diffuse into titanium at temperatures above 752˚F [400°C] raising the tensile strength but causing embrittlement of the metal.

The maximum allowable amount of oxygen in the weld metal is 0.30% while nitrogen comes in at only 0.15%. Hydrogen is limited even further to 150 parts per million. Because of this, the cleanliness of the base metal, filler metal and completely inert atmosphere are absolutely essential.

For small parts, the best way to weld is using the GTAW process inside of an argon chamber. This chamber is filled completely with argon and will typically be equipment with an oxygen and nitrogen sensor to ensure the levels of these elements are below the specified maximums. Some chambers look a lot like sandblasting cabinets, but they are very different. So don’t assume you can use a sandblasting cabinet as an argon chamber.

The chamber is filled with argon. As argon enters the chamber it displaces oxygen since it is heavier. The oxygen rises and exits through a special opening at the top of the chamber. The oxygen analyzer will indicated when you can start welding. Once the oxygen is below the specified level welding can commence.

Before filling the chamber with argon everything that needs to be welded must be introduced. Welding torches, filler metals and other materials must also be in the camber before purging begins. Small chambers take about 5-8 minutes to purge the oxygen. Much larger chamber can take hours. Of course, this depends on the flow rate of the argon coming in.

Argon must be continuously fed into the chamber, this does not stop once the oxygen level drops to below the specified maximum. Purging is only stopped when the welding is complete and the parts need to be retrieved.

A physical characteristic of titanium and titanium alloys is their relatively low thermal conductivity. This means a small heat affected zone after welding and a smaller area that needs the inert atmosphere. Because of this, it is possible to successfully weld titanium outside of an argon chamber. Proper shielding is still required by means of a trailing gas and shielding of the back side of the weld as in the case of thin sections and/or tube sections.

Acceptance criteria for welds are detailed in codes and standards. Most applications that use titanium are demand critical so allowances for discontinuities such as undercut, porosity, underfill, cracks and overlap are zero or very close to it. The major concern is the pickup of oxygen, nitrogen and hydrogen while the titanium is molten.

A small test is typically done in a piece of scrap titanium before welding on production parts starts. The test consists of striking an arc and allowing a puddle to form. No filler metal is added. Then the arc is turned off and the puddle solidifies. Once the part has had time to cool down the color is evaluated. You are looking for a silver-colored weld. If there is any kind of discoloration it means that oxygen and/or nitrogen were absorbed into the weld.

This chart can be used to evaluate whether the right shielding is being attained by performing the test mentioned above.

If the right atmosphere has not being achieved additional purging time may be necessary. You must also ensure there no leaks in the chamber that may be allowing air to enter it.

Titanium welding is still a niche business which only a few have mastered. This type of welding is typically done in critical aeronautical components so it also requires a significant amount of documentation and traceability.

powerwelds Welding Tips

1 April

What are the differences between AC and DC welding plant?

Difference between AC and DC Welding Machines

Welding is a process used to join metals together by melting the parts and using a filler to form a joint. Welds can be accomplished using different energy sources from a gas flame or electric arc to a laser or ultrasound. Welding cannot be done with all types of metals. For example, stainless steel is prone to cracking and distortions when it is overheated. Alloys are often a problem because it is difficult to know the exact chemical composition of the metal.

For a welder to make the best welds he must understand what alternating current (AC) and direct current (DC) signify on the welder as well as on electrodes.

Electricity flows in two ways: either in an alternating current (AC) or in a direct current (DC). Electricity or “current” is nothing but the movement of electrons through a conductor, like a wire. The difference between AC and DC lies in the direction in which the electrons flow. In DC, the electrons flow steadily in a single direction, or “forward.” In AC, electrons keep switching directions, sometimes going “forward” and then going “backward.”

Alternating current is the best way to transmit electricity over large distances.

AC and DC are terms that refer to the polarity of the electrical current that is created by the welder and runs through the electrode.

What Is Polarity?

Every electrical circuit has a negative and positive pole. Direct current flows in a single direction resulting in a constant polarity. Alternating current or AC current flows in one direction half of the time and in the opposite direction the other half. AC current changes its polarity 120 times per second with a 60 hertz current.

Other differences between Ac Current and Dc Current.

In Ac, it is safe to transfer over longer city distances and can provide more power while in Dc,Voltage of DC cannot travel very far until it begins to lose energy -Amount of energy that can be carried.
Steady magnetism along the wire while in Ac, it rotates magnet along the wire.Cause of the direction of flow of electrons
The frequency of alternating current is 50Hz or 60Hz depending upon the country while that of Dc the frequency of direct current is zero.Frequency
Ac reverses its direction while flowing in a circuit. Dc flows in one direction in the circuit.Direction

Its ideal for the following types of welds;

1. Downhand heavy plates

2. Fast Fill

3. Aluminium TIG welding with Hi frequency

In DC reverse polarity, the electrode is positive and the current flows from the workpiece to the electrode. It is ideal for:

Overhead welding
Vertical welding
Cast iron welding
Heavy aluminium
Rivet welding
Sheet metal
Low hydrogen welding
Arc bronze rod

Safety procedures for using these Welding machines

There are requirements for personal safety equipment and fire-prevention measures that welders must observe/ abide by.

Welding fumes can cause breathing problems in welders. Some problems are short term and others may be long term illnesses like asthma. Welding fumes are also internationally classified as possible carcinogens.

Personal protective equipment for welders includes

Fire-resistant clothing,
safety glasses,
shoes,
gloves,
hood and welding helmet and leathers. Synthetic clothing should never be worn because it melts when exposed to extremely high heat. Wool is a better choice because it is durable and resistant to fire.

AC And DC welding are both needed to accomplish certain tasks. DC welding generally has more advantages over AC welding but the most important thing for a welder to understand is how polarity works so that the welder can choose the proper electrode with the right polarity for the job.

powerwelds Welding Tips

1 April

How does resistance spot welding work, and where is it used?

Spot welding (also known as resistance spot welding) is a resistance welding process. This welding process is used primarily for welding two or more metal sheets together by applying pressure and heat from an electric current to the weld area.

Resistance welding utilises the Joule heating effect (I^2.R) of an electric current passing through a resistor. It is most commonly used for welding sheet metals. The most common type of resistance welding is spot welding. Refer to Figure (a).

The most common type of resistance welding is spot welding

The two pieces to be welded together (workpieces) are clamped together by two electrodes. Then a controlled burst of current is passed between the electrodes. The interface area between the workpieces heats with I^2.R losses where R is the resistance of the interface. The absorbed energy melts the interface area into a nugget which bonds the workpieces together. The process is fast, repeatable and lends itself to automation.

The welding cycle is shown in Figure (b). The steps are:

Electrodes are clamped with a preset force either side of the workpieces.
A burst of current of controlled magnitude and duration is passed between the electrodes. This produces the melted nugget.
After the current has stopped, the pieces are held together for a time to allow the weld to solidify.
The electrodes are released and the weld is complete

powerwelds Welding Tips

1 April

How to control welding distortion during the welding process?

Distortion is a nasty problem we experience in welding. Understanding what causes distortion is important in order to be able to minimize or eliminate it completely. There are physical and mechanical properties that affect distortion susceptibility of materials.

Larger weld nuggets in butt joints can help in minimizing distortion

As fabricators we hardly ever get to pick the base material of the welded structure. However, regardless of a material’s mechanical and physical properties, we can follow a set of rules to minimize or eliminate distortion altogether. Follow these steps and you’ll be on your way to controlling weldment distortion.

Don’t overweld – the more weld metal we put in the joint the higher the forces causing shrinkage. Don’t lay a 5/16” fillet when a ¼” fillet will do. If there is a drawing calling out welds stick to the sized called for. If necessary, invest in weld gages. You can learn how to use them in Proper Use of Weld Gages.
Use intermittent welding – using intermittent welds rather than continuous welds, where design allows it, can save as much as 75% weld metal and significantly reduce shrinkage and distortion. Welding stiffeners to plate is a great place to do this.
Minimize the number of weld passes – the shrinkage caused by each pass is cumulative, thus making it better to fill the same volume in fewer passes, especially when we are welding in the transverse distortion.
Weld near the neutral axis – as you can see in the image below the location of the weld relative to the neutral axis will determine which way the structure will distort. If we can place the weld right at the neutral axis we can effectively control distortion.

Source: Haynes International – Welding and Joining

5. Balance welds around the neutral axis – we can’t always change the material thickness to affect where the neutral axis is. In this case, whenever possible, balance the welds around the neutral axis. This means trying to achieve symmetry.

When designing consider the location of the welds based on the neutral axis6.

6. Use backstep technique – this is helpful since the previous weld create a restraint minimizing distortion. This technique may not be feasible in all situations.

7. Preset parts to offset distortion – if we anticipate distortion and can predict which way the welded structure will bend, we can pre-bend the part so that after welding the part is straight.

There are other methods for reducing distortion such as planning the welding sequence accordingly to counteract shrinkage forces. Peening can also reduce some of the residual stresses. Preheating and other thermal methods can help as well.

powerwelds Welding Tips

27 March

Which shielding gas is best for MIG welding?

Today we received two different requests for help pertaining to shielding gas selection. The first caller requested a chart that tells them what materials can be welded with the different shielding gases that they had. They wanted a chart that can be provided to the welders to make sure they used the right gas on the right material. The second caller asked if they could use their shielding gas used for stainless (98% Argon/2% Carbon Dioxide) on carbon steel.

For the second caller we were able to weld some samples using the 98/2 shielding gas on steel and showed them the effects on penetration and bead profile.

Our response to the first caller was that shielding gas selection is made based on more than just base material alone. Developing welding procedures specifications is a process that considers base metal, base metal conditions, joint type, welding position, material thickness, and many more requirements. The selection of a shielding gas is therefore affected by these requirements.

However, we get into trouble because you can make welds look good regardless of what gas you use, for the most part. For example, you can weld mild steel with any of the following shielding gases:

100% Carbon Dioxide
75% Argon / 25% Carbon Dioxide (75/25)
90% Argon / 10% Carbon Dioxide (90/10)
95% Argon / 5% Oxygen (95/5)
And many other mixtures

Although all of the above can be used on mild steel you must make your selection based on the application. If your base material is covered in rust and mill scale then the 95/5 mix is a terrible choice. But if we are welding on clean sheet metal than this 95/5 is adequate. 75/25 is an excellent choice for sheet metal as well since it is good with the short circuit mode of metal transfer, but should not be your preferred choice for welding heavy sections of steel (for the GMAW process). However, if you use flux-cored wire (FCAW process) then you can use 75/25 without concern for material thickness.

As you can see, there are certain considerations when selecting the right gas. We are in the process of creating a comprehensive chart that will cover not just the gases above but several more. For now, this is the quick reference guide we provided to our customer while the chart is created.

Shielding Gas Selector Chart

This chart should be used simply as a general guideline. All welding procedures should be qualified by testing or prequalified in conformance with the applicable structural welding code.

It is very important to know that just because a weld looks good on the outside it does not guarantee quality. Take a look at the image below:

This weld was made on 1/4″ A36 steel with 0.035″ ER70S-6 and 98%Ar/2%CO2 shielding gas in spray transfer. This shielding gas mixture is for GMAW of stainless steels.

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26 March

How to Select Air Compressor for Your Plasma Cutter

Plasma is a superheated ionized gas. In a plasma cutter air compressor system, you can think of this as a lightning bolt inside a tornado. For a small handheld plasma cutter running at 20-30 amps, you’ll need as little as 80 psi (5.5 bar). Larger, automated plasma cutting systems in the 130 to 800 amp range may require 115 psi (8 bar) or more.

The electrical current (lightning bolt) contains a massive amount of heat energy. The gas (tornado) ionizes, controls the arc, and blows away the molten material. In order for a plasma cutting system to perform optimally, the gas supply must be clean, dry, and properly regulated. When using bottled gas, these factors are relatively simple to control. Since most modern plasma cutting systems rely on shop air for the majority of cutting processes, it introduces more variables into the equation. Oftentimes, this causes performance and consumable life to suffer when the air supply is less than ideal.

Here, we’ll discuss the three factors that contribute the most to the performance of your plasma-cutting system and how to make sure that your tornado can keep up with your lightning bolt.

Before we can discuss what a plasma cutter needs to breathe, we need to understand the design and operation of air compressors.

About Plasma Cutter Air Compressors

A typical air compressor comprises of a motor-driven compressor and a storage tank. The storage tank size is represented in gallons or liters. Portable systems have tanks as small as 1 gallon, and stationary systems have tanks of 100 gallons or larger.

Flow rate capacity is a product of output pressure and storage tank size. The higher the output pressure is set, the lower the flow rate capacity will be. It is important that you are confident your compressor can keep up with the flow rate requirement of your cutting system when set at the required output pressure.

It is highly recommended that your plasma cutter air compressor be dedicated to running your plasma cutting system. If you plan to run other pneumatic devices simultaneously, you will have to add the flow rate requirements of all devices together. This ensures that your compressor can keep up without exceeding its duty cycle.

1. Pressure

Pressure is the force of the compressed air being fed to your plasma cutter. The value for gas pressure may be represented in pounds per square inch (psi), megapascal (MPa) or bar.

Air compressor system pressure is preset and usually between 100 psi and 135 psi. Output pressure is adjustable via the pressure regulator. Inlet pressures vary by system. For a small handheld plasma cutter running at 20-30 amps, you’ll need as little as 80 psi (5.5 bar). Larger, automated plasma cutting systems in the 130 to 800 amp range may require 115 psi (8 bar) or more.

Most commercial industrial air compressors for plasma cutters will be capable of generating pressures in this range. It is important to note that the inlet pressure at your plasma cutting system will be lower than the output pressure of your air compressor due to pressure drops between the two points which can be caused by leaks or restrictions such as undersized fittings or filtration units.

You may need to set your compressor’s output pressure slightly higher than the inlet pressure requirement of your plasma cutter to compensate for pressure drops. Consult your operator’s manual to determine the best pressure for your system.

2. Flow

Flow is the rate at which air is being fed to your plasma cutter from the air compressor.

The value for flow rate may be represented in cubic feet per minute (CFM or ft3/min), standardized cubic feet per minute (SCFM), cubic feet per hour (CFH or ft3/h), standardized cubic feet per hour (SCFH), liters per minute (l/min), or liters per hour (l/hr). The size of the tank largely determines the flow capacity of the compressed air system.

As a good rule of thumb, select a compressor that has a flow rate capacity of at least 1.5 times the consumption rate of the plasma cutter. You’ll also want to make sure that the hose or tubing in use is rated for the pressure the system will handle, large enough in diameter to handle the flow rate requirements, and will not corrode or cause excess moisture to develop inside the line.

Copper is preferable to steel and aluminum pipe. Lines shorter than 75’ should use 3/8” diameter hose or tubing. Lines longer than 75’ should use ½” diameter hose or tubing. If using a flexible hose, you should make sure not to pinch or kink the hose.

The orifice size of all fittings used should match the ID of the hose or tubing. Flow rate requirements also vary by system. You’ll need between 3.5 scfm (99 l/min) and 6.7 scfm (189 l/min) depending on your system’s requirements.

3. Filtration

While inlet pressure and flow rate vary by system, filtration requirements do not. At the surface level, it may seem that this makes filtration the simplest variable to account for.

In truth, filtration is the biggest gremlin in many air supply systems because it is often misunderstood. Operators assume that because they have invested in the proper filtration equipment, they cannot possibly be experiencing a filtration issue.

The design and layout of a compressed air system can have a large impact on the amount of moisture that becomes trapped in the system, and where it ends up. Gravity can be your friend or enemy in this regard. You should use air filtration devices to remove water, oil, and debris from your air supply. Place these as close to the plasma cutting system as possible.

Under most conditions, a common coalescing filter with an automatic drain is sufficient. If cutting in a high-humidity environment, consider a refrigerated air dryer.

Taking the time to ensure a proper supply of clean dry air to your plasma cutting system will provide you with better cut quality, less downtime, and longer-lasting consumables. If you need help selecting the proper air compressor or air system components, visit your local supplier for assistance!

PLASMA GAS SELECTION GUIDE

Plasma Gas	Shield Gas	Mild Steel	Stainless Steel	Aluminum
Air	Air	Good cut quality Economical	Good cut quality and speed Economical	Good cut quality and speed Economical
Oxygen	Air	Excellent cut quality and speed Very little dross	Not recommended	Not recommended
Nitrogen	Carbon Dioxide	Fair cut quality Some dross Excellent parts life	Good cut quality Excellent parts life	Excellent cut quality Excellent parts life
Nitrogen	Air	Fair cut quality Some dross Excellent parts life	Good cut quality Excellent parts life	Good cut quality Excellent parts life
Nitrogen	Water	Fair cut quality Some dross Excellent parts life	Excellent cut quality Excellent parts life	Excellent cut quality Excellent parts life
Argon Hydrogen	Nitrogen	Not recommended	Excellent on thicknesses above 1/2″	Excellent on thicknesses above 1/2″

powerwelds Welding Tips

19 March

Why Choose Automatic Orbital TIG Welding？

Orbital TIG welding is a welding process that requires a high level of competence and experience in order to produce great results . But it is quite difficult to count only on the experience and the skill of the welders to realise these kinds of welds, when productivity is required in addition to high quality welds. Automated welding with Power welding equipment offers a good solution when striving for these standards. In this article you will read more about the advantages and disadvantages of automated orbital welding.

What are the advantages of automated orbital TIG welding?

1. HIGH QUALITY WELDS

You obtain a much better quality by automated TIG welding compared to manual welding. Welds produced manually are not always of a poor quality, but the number of discarded tubes / defects is higher compared to TIG welding.

2. TRAINING / COMPETENCES

Using an orbital welding equipment is possible without a long and tedious training. You do not need to bean accomplished welder to proceed to orbital welding. Training sessions are typically much shorter and easier compared to those of a specialized welder. This means a gain in terms of labour costs and in deploying the welding teams.

3. A HIGHER PRODUCTIVITY

Automated orbital TIG welding provides you with a better productivity compared to manual welding. The welding tasks can be registered and repeated any time it will be necessary. When you make a weld manually, a variety of factors have a direct influence over it, whereas with automated TIG welding, the welds can be repeated by the equipment as often as required in the future.

4. A WELDING TECHNOLOGY SUITING CONFINED SPACE ENVIRONMENTS

Orbital welding equipment allows welding in all situations: confined spaces, lack of visibility, high-risk environments. Welding can be performed from a remote location and a special welding camera can be added to the equipment, reducing any risk for the operators.

5. ORBITAL TIG WELDING ENSURES BETTER MONITORING AND TRACEABILITY OF THE WELDS

Orbital welding equipment allows great recording of each weld. Every welding parameter is registered, the welds can be repeated any time by means of the data acquisition of each weld.

CONCLUSION

Yes, orbital TIG welding requires an investment if you want to automatize welding, but the return on investment is achieved quickly by the high quality of the welds that automated welding provides, as well as the increase in productivity.

powerwelds Welding Tips