Industry News
Stainless steel screw galling: causes, prevention and on-site fixes for seized threads
2026-09-16
Compiled by JIALI Industrial (164.hk) — a Hong Kong fastener supplier specialising in screws, bolts, nuts and selection know-how.
Why stainless steel is especially prone to galling
Austenitic stainless steels (304/A2, 316/A4) conduct heat at roughly one third the rate of carbon steel and work-harden readily. During tightening, the thread flanks see localised high pressure, micro-slip and momentary heat, producing cold welding between mating surfaces — the phenomenon known as thread galling. ISO 3506 governs material and mechanical properties but says nothing about installation friction, which is why projects so often report 'the material certificate was fine, yet the bolt would not go in'. The risk actually rises with longer thread engagement, larger sizes (M10 and up) and perfectly clean, oil-free threads.
Three keys to prevention: slow speed, lubrication, sensible pairing
(1) Control the speed: keep electric-tool run-in below 100 rpm — high-speed friction is the primary trigger. (2) Apply anti-seize compound: molybdenum-disulphide, PTFE or copper-based pastes cut the friction coefficient by roughly 30–50% and suppress micro-slip adhesion at very low cost, making them the most cost-effective measure of all. (3) Pair sensibly: match nuts and bolts from the same batch and material, avoid overly tight thread fits, and lubricate throughout when engagement exceeds 2d. Before batch installation, trial-fit 3–5 sets to confirm a smooth, free-running feel with no binding.
How to recover a joint that has already seized
The moment torque resistance spikes, stop — forcing it widens the cold-welded area, and the usual outcome is a broken bolt stuck in the hole. The right response: apply penetrating lubricant and let it soak for 10–15 minutes, then work the fastener slowly back and forth two or three times with hand tools to clear debris before continuing. A fully seized small part can be removed with a screw extractor; precision or expensive substrates may need wire EDM or spark erosion, which costs far more than prevention. Always replace with brand-new fasteners and re-apply anti-seize on reassembly. Need anti-galling treated stainless screws or installation advice? Contact JIALI Industrial (164.hk) with your application for selection and samples.
Related Reading
- How to align fastener standards? GB/T, DIN and ISO differences for cross-border procurement
- How to choose fastener surface treatment? Zinc, Dacromet, hot-dip galvanising and black oxide compared
- JIALI launches Stainless Steel zone with full 304 / 316 range
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