Stainless Steel Fasteners Galling or Seizing

We have a problem when tightening stainless steel bolts - they tend to seize - what's happening?     Stainless steel can unpredictably sustain galling (cold welding). Stainless steel self-generates an oxide surface film for corrosion protection. During fastener tightening, as pressure builds between the contacting and sliding, thread surfaces, protective oxides are broken, possibly wiped off, and interface metal high points shear or lock together. This cumulative clogging-shearing-locking action causes increasing adhesion. In the extreme, galling leads to seizing - the actual freezing together of the threads. If tightening is continued, the fastener can be twisted off or its threads ripped out.

If galling is occurring because of high friction the torque will not be converted into bolt preload. This may be the cause of the problems that you are experiencing. The change may be due to the surface roughness changing on the threads or other similar minor change. To overcome the problem - suggestions are:
1. Slowing down the installation RPM speed may possibly solve or reduce the frequency of the problem. As the installation RPM increases, the heat generated during tightening increases. As the heat increases, so does the tendency for the occurrence of thread galling.
2. Lubricating the internal and/or external threads frequently can eliminate thread galling. The lubricants usually contain substantial amounts of molybdenum disulfide (moly). Some extreme pressure waxes can also be effective. Be careful however, if you use the stainless steel fasteners in food related applications some lubricants may be unacceptable. Lubricants can be applied at the point of assembly or pre-applied as a batch process similar to plating. Several chemical companies, such as Moly-Kote, offer anti-galling lubricants.
3. Different combinations of nut and bolt materials can assist in reducing or even eliminating galling. Some organizations specify a different material, such as aluminum bronze nuts. However this can introduce a corrosion problem since aluminum bronze is anodic to stainless steel.

If you have questions about stainless steel or other fasteners, please contact us at AFT Fasteners (877) 844-8595 or via email Contact Us.

Petrochemical Hardware Suppliers in Texas, Houston & Dallas - AFT

 

     AFT Industries provides a wide variety of products and supplies for the Petroleum and Oil Field Industries. AFT is excited to announce that we now have offices in Dallas / Fort Worth as well as our new office in Houston, Texas. On the international stage of petroleum refinery and production, Houston stands on top of the industry that literally drives the world. We have expanded our services to an even broader geographical base of clients that drill, refine and transport petroleum based products all over the United States.
      Most hardware for this industry requires heavy duty components with larger sizes, higher safety specifications, higher operating tolerances and guaranteed longer life expectancies. Some of the premium petrochemical hardware that AFT Industries provides are:

• Studs and Bolts - petrochemical grades, stainless steel grades, exotic alloys: (nickel, brass, bronze, titanium), all threaded rod, low carbon studs, heavy hex bolts
• Nuts - heavy hex, all materials and grades, industrial electroplatings and specialty coatings

• Flanges - lap joint, welding neck, slip on, socket weld and threaded

• Pipes, Valves and Fittings - brass, steel, forged steel, stainless steel, CPVC, PVC, iron, and fittings for all purposes
• Gaskets - spiral wound, Flexitallic, composite materials/fibers and matching industrial sets

• Washers - all types of finishes and metal materials
• Special Platings & Coatings - Xylan, Teflon, Cadmium, E-Nickel, Zinc, Zinc Nickel, Nickel, Phosphate & more

• Cutting & Safety Equipment - personal wear, coco mats, escape chairs, welding helmets, welding supplies, leak detectors, saws, saw blades, circular safety blades and more.

     At AFT Industries the mission statement is simple: Provide our Customers with what they need to Succeed! We strive to accomplish this mission every day in a timely manner that allows your business to be as successful and profitable as possible.

Next time your company needs Petroleum and Oil Field hardware or supplies, do not hesitate to contact us at Info@Aft-Corp.com or call toll free 877-844-8595.


- The AFT Team