When they are correctly heat treated, stainless steel assemblies emerge from the furnace with excellent tensile strength and a clean appearance. However, there are several things that can go wrong with the stainless steel brazing process, mistakes that can significantly affect the strength and appearance of finished assemblies. By having an experienced heat treating company perform the treatment process, the customer can avoid the costly mistakes below.
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Not Cleaning the Metal of Coatings
Before it enters the furnace, the metal must be free of surface coatings. Coatings that are commonly removed include: oil, grease, decals, paint, dirt, and rust. If coatings are left in place, they oxidize during the stainless steel brazing process and mar the surface of the metal. The result is that the metal will require finishing measures to give it a clean, bright appearance.
Not Using an Atmosphere-Controlled Furnace
Stainless steel is a chromium alloy; it contains at least 10.5 percent chromium by mass. Despite being a chemical element that is corrosion-resistant under normal conditions, chromium is highly reactive when it is treated in an oxygen environment. The best way to prevent chromium alloys from oxidizing when they are heated is to place them in an atmosphere-controlled furnace.
Not Establishing Proper Clearance Between Parts
One of the main keys for producing strong assemblies is to establish the proper clearance between workpieces. Most metallurgists recommend a clearance of .0015" between the parts of the assembly. A clearance that is much wider than this will prevent the filler metal from forming a strong bond between the workpieces, which could cause the product to fail during service.
Cooling the Assembly too Fast
Cooling the assembly too fast can create internal stresses that eventually cause the assembly to crack and break. This is why many heat treating companies use an atmosphere-controlled continuous furnace when processing chromium alloys. In addition to providing the perfect heating environment, the furnaces can also cool assemblies slowly and uniformly to prevent stresses.
Conclusion
If you need to have a chromium alloy brazed, outsourcing the job to a professional provider of heat treating services is the best way to avoid four crucial mistakes in the brazing process: not cleaning the metal of coatings, not using an atmosphere-controlled furnace, not establishing the proper clearance between parts, and cooling the metal too fast. For more information about heat treating chromium alloys, contact an experienced provider of heat treating services for metal.
Franklin Brazing's 53,000 square foot facility was designed especially for their clean processes such as stainless steel treating and annealing. The company runs steel treating production around the clock five days per week and on weekends if needed. Visit our website at: franklinbrazing.com
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