Posted by Gordon England on August 28, 2003 at 21:40:45:
In Reply to: Carbon Steel galling in threaded application posted by Nick Atallah on August 25, 2003 at 22:00:41:
: Hi, I don't know if anyone here will be able to help me but I have a question regarding similar materials galling in a threaded application.
: First a little background,
: My company produces heavy load hydraulic equipment. We normally design hydraulic cylinders with the end caps threaded into the tube (10-24" diameter threads 6 threads per inch). The material we normally use is ASTM A516 Gr. 70 (70KSI Tensile) for the end caps and ASTM A106 gr. C (70 KSI Tensile) for the tube.
: Now for the challenge at hand,
: We currently have a contract to deliver some equipment to a very cold environment (-40C ambient temperature). We have chosen materials that will have good fracture toughness because of the low temperature. (We have Charpy V-notch test requirements at -40C). The materials we chose to use are ASTM A514 (110 KSI Tensile)for the end caps and a low allow centrifugally cast steel for the tube (112.7 KSI Tensile). When we try to thread the endcap onto the tube the end cap threads tend to cut into the tube threads and then material starts to gall. Most of the damage occurs on the tube.
: We realize that the metals are fairly similar in hardness and therefore not an ideal match. However the materials we normally use are even more similar!
: If anyone has any comments or suggestions I would love to hear them. I am not a metallurgist just a lowly mechanical engineer, so if you have any knowledge that may help me or if you can point me in the direction of someone who can I would greatly appreciate it.
: Thanks,
: Nick Atallah
Hi Nick
Check the finish or roughness of the thread flanks, particularly on the female thread. An increase in roughness normally leads to an increased risk of galling.
Try lubricants, anti-galling or sealing compounds.
Molybdenum disulphide, PTFE (Teflon), graphite, talc. Companies like Loctite and Interflon may be worth contacting.
Hope this helps.
Regards Gordon
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