Published torque values for Nitronic 60 Fasteners

Posted by Jeff Kirchner on May 20, 2016 3:32:00 AM
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  NITRONIC 60 is a natural stainless material for fastening systems. With an elevated yield strength (almost twice that of 304 and 316) in the annealed condition, it will take higher forces than popular stainless steels. This strengthening is primarily through the addition of Nitrogen to the composition. With the additions of Silicon and Manganese the material resists galling much better than these grades as well. These additions in essence help the inherent lubricity of the alloy and when coupled with the higher strength means that it will take higher stress before stretching or galling and tearing the thread. 

  This alloy has a low magnetic permeability, primarily due to its predominant austenitic nature. Corrosion resistance is similar or better than 316 and 304 as well. While this alloy does not require Molybdenum, like the 316, the Silicon acts in a similar fashion - though not as effective as Molybdenum. Silicon requires twice as much Silicon to be as effective as Molybdenum (2 to 1 ratio for replacement). This in effect means that NITRONIC 60 has a net Molybdenum rating of 2% compared to 316 having 2% minimum required.
  Running calculations of the estimated torque values on the materials reveals NITRONIC 60 annealed torque values should be 57% higher than 304L and 30% Higher for 316L (on fasteners smaller than 1/2" UNC/UNF) in both the lubricated and unlubricated. These increases are lowered to 42% and 19% respectively in sizes over 1/2" UNC/UNF.
Calculations were run with the same safety factor (SF) of 0.65, the same K value of 1.33, dry torque calculated with CF 0.4 and lubricated torque calculated with CF 0.2 (CF Coefficient of Friction)
  More calculations using higher  CF   numbers indicate a higher friction component, or 'stickier' material.  Changing the calculations to be more in line with materials expected  CF values of their respective materials provides more realistic results. 304L dry is closer to  CF   0.45 and 316L dry is closer to  CF   0.58.  The estimated torque values on the materials reveals NITRONIC 60 annealed  torque values should be 39% higher than 304L and 10% lower for 316L (on fasteners smaller than 1/2" UNC/UNF) in both the lubricated an unlubricated. These increases are lowered to 26% and -18% respectively in sizes over 1/2" UNC/UNF.
The last variable to look at is the Safety Factor, and whether SF=0.65 was too much or too little for your application. What the SF does is to help de-rate the material to ensure that it does not stretch or come close to failing during initial install. A study has been proposed to look at the subsequent torque loading requirements after initial install. A good fastener, by definition, would be to allow re-use of the hardware.
    We have all heard the nightmares caused by using foreign produced items and the extra inspections required to ensure those products meet specification.  When you buy from HPA the alloy will be known to be manufactured in the USA, and the manufacturing of the fasteners themselves will also be performed in the USA. We also utilize a Positive Metal Identification process for receiving. Using our NITON XRF gun we can assure that the material being processed is of the correct alloy family. 

Topics: nitronic 60 torque, nitronic fasteners, torque values nitronic, Fastenening

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