No need for annealing
Tube benders find success with unannealed material
Tube benders work with unannealed material and deliver better-performing products to customers.
Fabricators are always looking for new ideas. Any new strategy, whether it involves a machine, a process, a technology, or a technique, is worth investigating if it will result in a better product or improve profitability.
New ideas aren't always easy to implement. Sometimes they are stymied by standard operating procedures based on proven practices that deliver predictable results—also known as "this is the way we've always done it." On the other hand, sometimes a new idea falls in front of open minds that can and do understand the opportunity, and they do everything they can to turn the idea into a plan and the plan into reality.
When open minds meet a new idea that has the potential to meet their needs, everything falls into place and a new operating procedure replaces the tried-and-true way of doing things. This is good news for tube benders and fabricators that work with steel in applications that require heat and corrosion resistance. Recent experience at Atlas Steel Products, Twinsburg, Ohio, has shown that, with a little time and effort, tube fabricators can explore material options, change to a new material, reduce costs, increase operational efficiencies, and deliver a better-performing product to their customers.
Calling on Experience
Atlas has worked with a number of heating, ventilation, and air-conditioning (HVAC) customers on switching from annealed 409 stainless steel to unannealed 409. Their experiences demonstrate that unannealed 409 actually is a better choice in many applications than annealed 409.
Such successes are not a snap to generate. The material supplier must have substantial metallurgical knowledge, experience with alternative materials, and a thorough understanding of the fabricator's challenges and performance requirements. The fabricator must have an open mind, a willingness to get beyond the "this is the way we've always done it" limitation, and a readiness to adopt new ideas when the benefits are clear and tangible.
In the past many tube benders working with 409 stainless in HVAC applications were persuaded that to gain optimal performance throughout the process, without damaging the integrity of the tubing's weld, the best material was annealed. The accepted truth was that annealed 409 was easier to form because of the metallurgical properties that result from annealing.
Factors to Consider
Material options can be confusing. Factors to consider include tubular product alloys, grades, conditions; raw material quality; variations in primary and secondary processes (making the tube and fabricating it); and the customer's equipment and methods. It also is important to analyze factors that are peripheral to, but just as important as, the manufacturing processes, such as inventory control arrangements, raw material packaging, and material handling.
Atlas' counsel for fabricators follows the fabrication process, starting with raw material procurement and ending with shipping the finished component to the customer:
- Use certified, prime material from accredited (ISO 9000) mills.
- For each product, conduct a supplier-purchaser review of optional and optimal material choices, factoring in formability, durability, and other relevant material properties.
- Weigh total material and quality cost considerations by suppliers and mill sources. The purchase price alone can be misleading. In many cases a high-cost, high-quality material can be less expensive and time-consuming to fabricate than a low-cost material.
- Consider high-quality, camber-free slit coils of raw material.
- Purchase large coils to reduce the coil changeover frequency and product variations.
- Match higher-efficiency, higher-productivity materials with the proper tube-welding equipment and technologies.
- Use high-efficiency, in-process quality evaluations, including metallurgical weld integrity.
- Depending on the material, substitute as-welded material manufactured with a solid-state welding machine for conventionally made welded-and-annealed material.
- Look for other in-house efficiency opportunities. In some cases, a protective returnable rack can enhance both shipping and storage.
Several recent successes improved overall tube bending efficiencies with welded tube made with unannealed 409 stainless steel for HVAC applications. Although annealed 409 is accepted by many fabricators as the optimal material for fabrication, Atlas has found that unannealed 409 made with high-speed welding has better material consistency. High-speed welding reduces property variations in the as-welded material; forgoing annealing eliminates any inconsistencies associated with that process.
Material with more consistent properties requires fewer bender adjustments, which translates into more tube bender uptime. Furthermore, unannealed 409 is more aesthetically attractive because the material is bright compared to the heat-tinted, stained appearance of annealed stainless.
Beckett Makes the Change
Beckett Gas Inc. is a heat exchanger and combustion component supplier to HVAC system manufacturers. It supplies 409 stainless steel heat exchanger tubes, bent to customer-specified configurations, and it relied on annealed gas tungsten arc welded (GTAW) 409 tube products. Beckett sought to reduce the cost of its 409 stainless tube materials for the heat exchanger product lines, and began to investigate options. BGI's tube bending processes, which were used successfully for aluminized carbon steel heat exchanger tubing, required repeated setups and numerous adjustments when bending lots of annealed 409 tubes.
BGI investigated the use of unannealed, high-frequency-welded 409 stainless tubing. After running blind trial lots (blind so as not to influence the bender operators), BGI saw improved lot-to-lot consistency and a reduction in the lot-to-lot tube bender adjustments after it switched to unannealed tubes.
The Appeal of Unannealed
Two other HVAC component manufacturers also made the switch.
For one of these manufacturers, aluminized carbon steel was its conventional material. It investigated annealed and unannealed 409. Its initial work with annealed 409 stainless tubes proved that the costs associated with GTAW and annealing were prohibitive, reducing profitability, and the material was difficult to process. Tube bender setups and delays added time to the process, and tubes occasionally failed during bending.
Type 409 produced with high-frequency, solid-state welding without subsequent annealing proved to meet the customer's requirements and resulted in a cost reduction that approached 25 percent; a significant portion of the savings came from eliminating the annealing process. In addition, the new material's consistency resulted in fewer bender setups and eliminated the breakage problem.
Another manufacturer was processing aluminized steel and 409 stainless HVAC tubing for residential heat exchanger applications in two plants. The staff at one plant was using unannealed 409 tubing, while the sister plant was using annealed tubing. The engineers at the facility had always used annealed and were convinced that they needed to continue to do so despite the other plant's success with the unannealed product. Atlas worked with the sister plant as it tweaked the process and made some minor tooling changes that allowed it to change to unannealed 409.
The FABRICATOR is North America's leading magazine for the metal forming and fabricating industry. The magazine delivers the news, technical articles, and case histories that enable fabricators to do their jobs more efficiently. The FABRICATOR has served the industry since 1971.