The Best Brazing Method for Stainless Steel: Important Considerations
BusinessBrazing follows a similar process from one brazing method to another, but each method has unique characteristics that create unique results. For example, brazing stainless steel requires a controlled atmosphere that eliminates oxidation during brazing. This method provides unique benefits that others do not, particularly superior surface gloss and bond strength. But there are important cost, quality and environmental considerations that determine how valuable it is to a brazing company’s customers.
Cost Considerations
The cost of brazing equipment and the brazing process is ultimately passed on to the customer, so it is crucial to use cost-effective, high-efficiency furnaces. Today, the most common types are furnaces that use vacuum to remove oxygen during the brazing process; belt kilns, which move parts on a belt and use an atmosphere reducer to remove oxygen; and atmospheric bell jars, which control the atmosphere by placing a bell over work pieces.
Although vacuum furnaces and atmospheric bell jars provide excellent atmosphere control, they have two drawbacks compared to band furnaces: they cost more and they weld parts in batches, which slows down the production process. While product quality is the first concern, one must also carefully consider how the equipment affects service price and production capacity, the latter of which could affect customer sales opportunities.
Another cost consideration is the atmosphere used to weld stainless steel. Stainless steel is traditionally welded in an atmosphere of dissociated ammonia. But the cost of buying and storing anhydrous ammonia, and the potential for emissions penalties for companies that are located in low emission zones (LEZs), have made it unpopular. Today, the preferred option is a brazing method using a nitrogen/hydrogen atmosphere.
quality considerations
Most stainless steel products have two design requirements: a shiny surface and excellent strength. To ensure a shiny surface, an atmosphere with at least 25% nitrogen is recommended. For the best gloss, this percentage can be raised to 80 percent or higher. To ensure strong bonds, the key is to remove oxygen from the atmosphere, thus eliminating trace oxidation that weakens the bond between parent and filler metal.
environmental considerations
The main environmental concern is whether the brazing atmosphere has a chemical or elemental composition. Depending on the volume of brazing a company does, the use of an ammonia-based atmosphere might be unacceptable in terms of current emission limits and future environmental legislation. Combined with the danger that the use and storage of anhydrous ammonia pose to the work environment, a nitrogen/hydrogen atmosphere is the optimal choice.
Conclusion
For manufacturers who economize by outsourcing metal processing, the interplay of cost, quality, and environmental aspects of metal processing is important. In addition to wanting high-quality, low-cost service, manufacturers prefer brazing companies that demonstrate environmental responsibility. If you are considering outsourcing your stainless steel brazing needs, speaking with a company about their brazing method in terms of the above considerations will help you assess the value of their service.