Recently, Marlin Steel’s engineering team was asked by a client whether a stainless steel nut could be welded to a carbon steel wire form.
The short answer was “yes, you can, but you probably wouldn’t want to.” In most cases, if you need a corrosion-resistant wire form, it’s best to go all the way with stainless steel wire rather than mixing and matching metals.
How You Could Weld Dissimilar Metals
Austenitic stainless steels such as grade 304 stainless or grade 316 stainless can be welded to plain carbon steel using MIG and TIG welding. In many cases, when welding dissimilar metals such as stainless and plain carbon steel, weld processes such as MIG welding that use filler material are preferred.
Resistance welding of stainless and carbon steel isn’t typically done, as the differences in electrical conductivity between the two make reaching the right weld temperature extremely difficult. When resistance welding is used, the carbon steel is usually preheated since it’s more electrically conductive and doesn’t heat up as fast as stainless steel.
Reasons You Don’t Want to Weld Plain Carbon and Stainless Steel Wire
- Difficulty. Welding dissimilar metals together adds extra challenges to the process. This translates into increased labor, rejection/error rates, and costs.
- Hot Cracking of the Stainless Steel. Because it is more electrically-resistant than carbon steel, stainless heats up much faster in electrical resistance welds than carbon steel. While waiting for the carbon steel to reach weld temperature, the stainless can overheat and become riddled with hot cracks. Using filler-based welding or preheating the plain steel can ameliorate this, but these methods aren’t perfect.
- Thermal Expansion in High Temperature Service Conditions. Another problem with using dissimilar metals in a welded wire form is that thermal expansion from heat will affect each metal differently. This difference in expansion rates between the two metals can cause extra fatigue to the welded joint—reducing the wire form’s structural integrity and useful life.
- Increased Bimetallic Corrosion. One of the reasons you generally want to use stainless steel is because of its strong corrosion resistance. An uncovered weld of plain and stainless steel that is exposed to extreme corrosive conditions, such as immersion in saltwater, could cause corrosion. This is because the intermingling of plain steel particles with the stainless alloy compromises the protective oxide layer of the stainless, allowing rust to form.
- Reduced Weld Strength. The problem with joining dissimilar metals is that it can lead to weaker welds—even with filler-based welding methods. The differences in weld temperatures and operational tolerances alone can easily compromise the strength of the welded joint.
To boil it down, welding dissimilar metals together is difficult to do right, and often produces inferior results to using metal alloys that are similar or the same.
By taking into account the long-term effects of using different metal alloys in a custom wire form, you can make sure that you get the right basket for the job.
If you have a question about wire forming issues, or need a custom wire form for a high-precision application with strict tolerance requirements, be sure to contact an experienced mechanical engineer!