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In order to have a proper and clean welding procedure and process in the submerged type of arc welding, we can use Hobart and it’s explanations for it.
Proper welding process
The submerged arc welding (SAW) technology has the ability to significantly improve deposition rates and productivity while also providing reproducible weld quality.
This is due to the fact that the arc is kept submerged during the welding process. However, there are some applications where it works much better than others do.
When taking SAW into consideration, there are a number of different aspects that can affect the success of the procedure. It is necessary to evaluate not only the material thickness but also the joint design, the fit-up, and the length.
Be aware, though, that in order to achieve the most possible success with SAW, you will first need to do some research and make an investment in equipment. However, in many instances, this will result in a return that is both considerable and expeditious.
How does SAW work?
SAW is a method that is wire-fed, similar to gas metal arc welding (GMAW, or MIG). During the welding process, a wire is fed through a torch that is often mechanized to travel along the weld joint.
Having a knowledge of and being able to control SAW is not all that dissimilar to having an understanding of and being able to control GMAW.
The process of setting the machine up is very identical, and many of the variables that affect welding are the same: There is still a relationship between voltage and bead width, between amperage and penetration, and between an increase in wire feed speed and a rise in both amperage and deposition (assuming constant contact-to-work distance and use of a CV power supply).
Granular flux is used in SAW rather than gas metal arc welding (GMAW) to shield the arc from the surrounding atmosphere. During operations that are considered to be normal, the arc is hidden from view because it is engulfed and concealed by the flux.
Molten flux performs critical roles such as deoxidizing, alloying, shaping, and providing a protective environment for the weld deposit as the wire, flux, and base material are melted together by the arc to produce the weld pool.
SAW can give large productivity benefits in specific applications; but, in order to get these results, an investment in the appropriate equipment, in addition to the power supply and wire feeder, is required.
Because of this, the SAW technique often requires a greater financial investment than alternative methods.
There is a wide variety of available accessories, and each one serves a different purpose in optimizing SAW mechanization and providing differing degrees of flexibility to meet the requirements of certain applications.
In certain circumstances, the torch will remain immobile while the workpiece will be moved with the assistance of positioning apparatus. When arc motion is necessary, there are various options available, including the following:
SAW welding tractors provide portability and flexibility, allowing welding to be brought to jobs placed anywhere in the shop or even inside a vessel.
Proper welding ppe
Since side beams and gantry setups are fixed installations rather than movable ones, the work must be hauled to the weld cell in order to be completed. This cuts down on the amount of time spent setting up or changing over, but at the expense of flexibility.
An integrator can provide assistance in the design of a bespoke system, such as circular welders for the attachment of nozzles or girth welding for storage tanks. Some of these methods can be connected with positioning equipment to allow for the welding of more complex geometries, such as pipe saddles.
The SAW mechanization process is far more approachable as compared to robotic welding. In general, its implementation and familiarization are less complicated and time consuming.
Even though the operator needs to pay attention when using SAW, making adjustments while welding is typically much simpler than when using a robotic welding operation. In addition, SAW equipment is often built with durability and dependability in mind from the ground up.
However, keep in mind that SAW can only be used for welding in a flat or horizontal position, which enables the use of welding parameters that involve high current and high deposition.
It is possible that using a SAW for whole elements that have many welds may require substantial positioning equipment. Some of the available options are drop-tilt, head, and tailstock.
Sometimes the expense of this positioning equipment can be prohibitive; but, in other circumstances, the return on investment can quickly justify both the equipment and the SAW process when compared to welding out of position using another technique.
During the welding process, the operators are unable to monitor the position of the arc; therefore, joint tracking devices may be required.
There is a wide range of options available, some of which are straightforward, such as a laser that indicates the future position of the welding arc, while others are more complicated, such as a tactile probe that can automatically alter torch position.
Consult with an integrator or a manufacturer of the equipment in order to evaluate the mix of machinery that will optimize the potential of a SAW operation and calculate its return on investment.
Whether or not a part is suitable for SAW depends on a number of criteria. Both the type of material and the thickness are essential elements to take into account.
SAW is most effective when used on carbon and low-alloy steels, but it is also capable of cutting stainless steel and nickel-based alloys.
It is a frequent fallacy that SAW can only be used on thick materials, despite the fact that thick materials are the most common type of material.
SAW has proven to be effective on relatively thin materials in a variety of applications, including water heaters and propane tanks.
Even if high amperages are utilized, the travel speed is greatly increased in these scenarios, which results in a low heat input as a result of the combination of the two factors.
For instance, a single-torch SAW has the capability of welding material with a thickness of 6.5 millimeters in a single pass at 800 amps while moving at a speed of 76.2 centimeters per minute (or more, depending on joint design).
It is important to keep in mind that welding thinner materials necessitate paying increased attention to the "smoothness" of the mechanization, joint tracking, and consistency of joint preparation.
It is common practice to back joints with copper and/or welding flux, which is a solution that can increase repeatability.
Regardless of the thickness of the material, the following are critical part considerations that must be made in order to successfully utilize SAW:
Joint and component geometries: Since parts having jogs in the weld require more complicated and expensive mechanization to handle frequently, SAW is best suited for straight-line joints. Joints with jogs in the weld can be welded using other methods.
And despite the fact that SAW is ideally suited for high-volume components, its application is not limited to producing identical copies of the same component over and over again. SAW is useful for even job shops because of its versatility. To get the most out of the process, the individual parts don't have to be exactly the same, but they should have comparable geometries.
Proper welding angle
For instance, since the geometries of 3.7-meter-diameter and 3-meter-diameter pressure vessels are comparable, it is normal practice for SAW and its equipment to readily weld both sizes of pressure vessels.
The goal is to locate components that may make use of the same arc/work motion equipment and equipment placement in order to cut down on the amount of time spent on changeover and therefore on downtime.
SAW is a common choice in pressure vessel and pipe applications because the vessel or pipe may be rotated on positioners.
This makes circumferential welds greater than 200 millimeters in diameter. However, beyond this diameter, it becomes more difficult to confine the flux since the flux waterfalls off the pipe.
If you employ SAW on pipes with a smaller diameter, you run the risk of producing an undesirable bead profile. This is because the pace at which the weld cools in SAW is slower than in other techniques.
Parts that are easily accessible Because of the size and weight of the SAW equipment, space, and part access are two of the most important issues.
If you want to use a system in a smaller place, you might need to have it custom-designed, but then you might run into problems with cable feeding. On a robotic GMAW arm, the large diameters simply do not possess the same degree of flexibility as the smaller diameters.
Welders discuss the proper type of welding procedure and process. Application, cost, and quality level determine the optimal welding procedure. Material, welding position, and location are application factors.
Welding costs are quantified in pounds of weld metal per hour. Labor per hour is a set cost irrespective of the welding procedure. The product's quality level depends on codes, norms, and customer requirements.
Boiler and pressure vessel manufacturing uses five arc welding processes:
- SMA Welding (Stick)
- Submerged arc welding (Sub-Arc)
- FCA Welding (Flux-Cored)
- Gas-Metal-Arc-Welding (MIG)
Each procedure has advantages and limitations that assist identify the best welding method. Each procedure is described below.
Stick welding is the most common method. It's adaptable and uses simple gear. The compact, light electrode and holder can reach hundreds of feet from the welding power supply.
Even though the equipment is cheap (beginning at $300), the process is pricey. This is because the deposition rate is low, around 2 to 5 pounds each hour.
Since a typical consumable electrode is 14 inches long, the arc must be stopped to replace it. Downtime, stub loss, and inefficiencies raise costs.
Proper welding rod angle
Stick welding requires expert welders for high quality. Low heat input gives weld metal a fine microstructure. The slag that protects the molten weld metal from the atmosphere can develop slag inclusions if not cleaned adequately between passes and at the start and end of each weld. Large welds have multiple starts and stops, which causes flaws.
Submerged Arc Welding (Sub-Arc) is the cheapest welding method, although the equipment is expensive. Since sub-arc is generally an automatic or machine welding process, a lot of money is spent on carriages, turning rollers, manipulators, welding heads, and power supplies.
Submerged arc welding's high amperage (over 1,000 amps) can penetrate and deposit carbon steel plates quickly. Sub-arc can dump over 100 pounds per hour with up to five wires at once. Here, costs are cut.
High productivity has drawbacks. Due to granular flux and weld puddle, sub-arc can only be done level and horizontally.
High amperage and heat inputs produce welds with big grains. Large grains and micro-inclusions from the slag system provide lower mechanical characteristics than certain lower heat input techniques, although they can still be good.
Flux-Cored Arc Welding (Flux-Cored) is versatile. It's self-shielded or gas-shielded. Self-shielded is utilized outdoors and when mechanical qualities aren't needed. Gas-shielded is utilized indoors when greater mechanical qualities are needed.
Popular gas-shielded uses an external source of shielding gas. CO2 or argon/CO2 is utilized to safeguard the arc. Gas-shielded flux-cored arc welding produces cleaner weld metal and superior mechanical characteristics.
Large-diameter (3/32-inch) wires may deposit 21 pounds per hour and penetrate well. They're merely flat and horizontal.
035,045, and 1/16-inch wires are great for out-of-position welding. All-position techniques produce the highest deposition rates and quality. Vertically and above, they can weld 10 lbs/hr.
Short-circuiting, globular, spray, and pulsed are MIG droplet transfer mechanisms. Current, voltage, and shielding gas oxidizing potential influence operating mode.
CO2 shielding uses low-current short-circuiting. Short-circuiting generates little heat and penetrates little. This helps control distortion on thin parts, fill gaps, and weld over pollution. Fast-freezing puddle allows all positions. Short-circuiting thick parts can cause "failure of fusion."
The globular transfer is high-current short-circuiting. In globular transmission, the arc doesn't run out, therefore there's more heat and better penetration. It runs on 100% CO2 or argon-CO2.
Spray transfer uses a 98% argon/2% oxygen combination. The transition current must be exceeded. Spray transfer offers good penetration and deposition rates due to its high current.
In spray mode, the 1/16-inch wire can deliver 14 lbs/hr deposition. Spray transfer may only be utilized flat or horizontally due to heat and fluid puddles.
Pulsed transfer combines spray and globular. Low background current, strong pulse current. A high current causes a spray transfer, then the welder lowers the current.
Heat input is lower than spray transfer, hence out-of-position welding is possible. But short-circuit heat is higher, so penetration isn't an issue.
Since the arc is entirely shielded (as with minimum oxygen content), the weld metal has good mechanical characteristics.
What is the best?
ARC welding has positives and downsides. Each can generate high-quality welds if used appropriately.
Gas-shielded methods produce purer weld metal with superior mechanical characteristics. Flux-based techniques are easier to utilize but have micro-inclusions, greater oxygen levels, and worse mechanical characteristics.
Any of the aforementioned procedures may be "the best" based on the application, desired cost, and required quality level.
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