Frequently Asked Questions:
How is the KF-300 subarc flux oven used in the field?
Subarc flux is top-loaded by way of a hinge-supported lid that is easily lifted manually, and discharged through a slide valve located on the bottom of the unit. Handy, fixed steel bars that stretch across the hopper opening allow the easy emptying of new flux from unopened factory packaging. The flux bags can be placed across these bars, cut open and emptied into the oven hopper. When flux needs to be removed, a container is placed by the user beneath the hopper to catch the granulated flux as it is dispensed. The hopper unit is securely mounted onto a rolling stand with 4 heavy-duty casters- two that are swivel with brakes and 2 that are rigid. The wheeled mobility of the KF-300 flux oven enables easy transport. As an added mobility feature, the sides and back of the flux hopper have welded-in channels with threaded bolts; users can easily install lifting eyes into the bolts to enable transport by forklift or other method, if desired.
The welding flux temperature inside the oven is regulated and controlled by a field-adjustable, digital controller with bright, LED temperature indicating display (user can switch from Celsius and Fahrenheit). This microprocessor is housed in a control box on the side of the flux oven hopper, along with a separate on/off indicating red light. This light enables users to quickly view from a distance if the oven is receiving power or has been shut off.
What can you tell me about performance of Keen KF-300 flux ovens?
The KF-300 is ruggedly designed to withstand years of use in the most demanding industrial environments. Heavy-gauge steel is used throughout the unit and 2 inches of mineral wool in the oven walls and lid keeps the KF-300 flux oven well-insulated and energy efficient. The exterior features a durable powder-coated paint that is highly-resistant to industrial environments and will stand up to years of use. The KF-300’s hopper is has fully welded seams inside and out, and is securely mounted to the wheeled dolly by way of heavy duty screws. The oven hopper can also be removed by the user from the dolly and placed at the weld head for direct dispensing of flux.
Thorough, energy-efficient and quick heating of welding flux is the hallmark of all Keen flux ovens. The KF-300 in particular has twelve elements evenly dispersed throughout the flux oven hopper cavity. When loaded with flux, no more than 2” of flux is without direct heating. It is important to note that our flux ovens are designed to reduce watt density to the elements, eliminating the problem of flux fusing to the heating elements which is a common problem seen in competing brands. Fusing of flux often creates a “gumming” effect causing the granulated material surrounding the elements to meld together.
As standard equipment, Keen KF-300 flux ovens feature a UL® approved microprocessor with digital up/down temperature control and LED temperature-indicating display. The temperature reading can be displayed in either Fahrenheit or Celsius, and has a ±0.2 degree accuracy. Handy tactile increment/decrement keys on the controller’s water-resistant front panel enable easy temperature set point adjustment. The controller also features an on/off control mode.
Do Keen Ovens come with a manufacturer’s warranty?
Yes. Our ovens have a 1 year manufacturer’s limited warranty.
What is granulated submerged arc welding flux?
Used as a protective layer in the process of submerged arc welding (SAW), subarc flux is a granulated, fusible material consisting of lime, silica, manganese oxide, calcium fluoride, and other compounds. The flux forms a hardened layer after it is heated and becomes molten. In this melted state the flux becomes conductive, thus enabling it to supply a constant current between the electrode and the welding work. The remainder of the flux is recovered and reused, unless it has become contaminated.
The granular flux used in SAW serves several functions. In addition to providing a protective cover over the weld, the flux shields and cleans the molten puddle. The flux also affects the chemical composition of the weld metal, the weld bead shape, and the mechanical properties of the weld. Another function of granular flux is to act as a barrier that contains and concentrates the heat into the weld area thus enabling deeper weld penetration.
Why does granulated submerged arc welding flux need to be stored in an oven?
In order to answer this question, it is pertinent to describe the four types of welding fluxes that are commonly available: fused, bonded, agglomerated and pre-mixed fluxes.
Fused — this type of flux is non-hygroscopic (does not absorb moisture from the air). Any surface moisture on the particles can be removed at a low temperature oven setting of 300°F.
Bonded — this type of flux is hygroscopic (absorbs moisture from the air) and is comprised of a combination of dry ingredients that are glued together with a liquid binder, then baked at a low oven temperature.
Agglomerated — this type of flux is hygroscopic and is manufactured the same way as bonded fluxes only a ceramic binder is used instead of a liquid binder.
Pre-Mixed — this type of flux is hygroscopic and is simply a combination of two or more bonded or agglomerated fluxes.
Just as stick welding electrodes readily pick up moisture from the surrounding atmosphere, the same applies to bonded welding fluxes that are comprised mostly of dry, powdered ingredients. As described above, the purpose of flux is to clean and shield the weld area from impurities. If moisture has contaminated the flux, hydrogen is released into the metal when heat is applied. When the weld cools, it can become brittle, crack and/or develop pinholes. Moisture-contaminated flux can also accelerate corrosion to certain metals like aluminum and must be kept dry throughout the welding process.
Keen welding flux holding ovens and rebake ovens are an indispensable addition to any subarc welding operation to help ensure quality welds. Our flux holding ovens and rebake ovens are suitable for almost any flux heating application that is required for today’s professionals.
What is the difference between subarc flux holding/storage and subarc flux rebaking/reconditioning?
Generally, there are two involved with the proper maintenance of subarc welding flux: holding (also called storing) and rebaking (also called reconditioning).
The holding process refers to the long-term* heated storage of welding flux to maintain factory-fresh dryness. Storing the flux at elevated temperatures prevents atmospheric moisture contamination of the hygroscopic granules. There are various temperature requirements according to the type of flux and also that are also set forth by welding codes. For specific holding temperature guidelines, please contact the manufacturer of your welding consumable.
The rebaking process refers to the short-term**, high temperature heating of subarc flux that has been contaminated by atmospheric moisture. The rebaking process “reconditions” the welding flux, meaning it bakes out the moisture that has been absorbed thus restoring the flux so it is suitable for reuse. For specific rebake temperature guidelines, please contact the manufacturer of your consumable.
* - In relation to our products, we consider long-term to mean 24 hours/day 7 days/week.
** - In relation to our products, we consider long-term to mean 24 hours/day 7 days/week.
What are the key differences between welding flux holding ovens and welding flux rebake ovens?
Keen ovens are specifically designed according to the temperature range of the process, and the amount of subarc flux to be stored. The standard holding ovens are designed to accommodate a maximum temperature of 550F and the rebake ovens are designed to reach 999F. The higher temperature ovens have larger wall thicknesses to accommodate more insulation and digital programmable temperature controllers. More information is available on the individual product pages. Please select a product from the chart above and you will be taken to the product page which has digital photos of each flux oven and technical specifications.
How do I store unopened packaging of sub-arc welding flux?
Submerged arc welding flux is available in a wide-variety of packaging and in various amounts according to how much is used, bulk pricing, etc. It is commonly purchased in single wall plastic or multi-wall plastic bags, paper bags, bulk bags with liners, plastic pails and steel drums. It is recommended by most manufacturers that users follow basic guidelines when storing unopened packaging. For example, storage of unopened bags must be indoors with moderate relative humidity below 70% (RH suggestions vary among flux manufacturers) and within a temperature range of 48°F-122°F. A bag of welding flux is the least durable form of packaging available, and care must also be taken to avoid puncturing or tearing the packaging. Avoidance of condensation is critical and is the main objective when storing unopened bags of welding flux. The more durable plastic pails and steel drums are tightly sealed and are often stored outdoors. Care must be taken to protect the containers from rain and snow. Again, condensation and moisture is damaging to flux and must be avoided. Labeling must never be removed from flux packaging while in storage.
Once I opened packaging, how should I store new, unused flux?
As discussed above, sub-arc welding flux is hygroscopic and once exposed to the atmosphere it will absorb moisture; the amount absorbed depends upon the relative humidity in the air and the period of time the flux remains exposed. It is recommended by most manufacturers of welding flux that unused amounts be stored at elevated temperatures in an oven to stave off moisture and ensure quality welds. Keen flux holding ovens are designed to hold welding flux that has not been exposed to moisture (either new or recycled) in order to preserve quality and maintain performance of the flux in operation.
What is the procedure for recycling welding flux and what are slag screens?
After the weld is completed flux that is not consumed can be collected and recycled to the flux oven hopper. However, contained in the non-consumed flux may be some contaminants such as slag, metal, mill scale, grindings, etc. that need to be filtered out before the flux is introduced back into the hopper to mix with new flux. Many manufacturers of sub-arc flux recommend maintaining a ratio of new flux to recycled flux. Some suggest adding 20% new flux by weight to recycled flux, others recommend a rule of thumb that one part new flux be added to three parts reused. it is always best to check with the manufacturer of your consumable for guidelines.
Keen flux oven slag screens are designed to be a sieve for filtering out contaminants in reused flux as it is being poured back into the flux oven hopper. The hole size on our flux oven slag screens is standard, but we can adjust the screen hole size if you have a different requirement. The slag screens are a fixed size according to the flux oven with which they are used.