Australia's #1 industrial directory for equipment & suppliers

Why nozzle anti-spatter sprays could be doing more harm than good

Supplier: Loctite - Henkel Australia
31 July, 2014

A persistent bugbear of today's welding process is the release of 'spatter' – particles of molten metal expelled from the welding arc and deposited throughout the weld area.

The build-up of these ostensibly benign molten particles has the potential to diminish the quality and durability of weld joints, requiring immediate repair or, in many cases, complete re-welding.

A recent survey by one of India's largest auto component manufacturers, Badve, observed that 12 per cent of robot MIG welded parts were deemed defective due to spatter-related defects, an unacceptably high defect rate of for today's efficiency driven businesses.1

Reworking or scrapping sub-par welds can sap hours of productive labour from your workforce. Indeed, if a weld operator were to spend just four hours per week repairing defects, this 'non-production' time would equate to approximately $6240 per year in lost labour2.

More than mess: torch head damage, impaired weld quality and downtime

Delicate torch head attachments (or consumables) – including diffusers, shrouds, contact tips and shielding gas nozzles – are at the frontline of the welding system, in direct contact with the welding wire before it enters the weld pool.3 The integrity of these frontline consumables is crucial to maintaining consistent weld quality and maximal utility of labour.

Critically, both MIG and MAG welding rely upon a steady supply of shielding gases to prevent oxidative damage to the weld seam.

During the welding process, spatter can adhere to the contact tip and torch shroud, and quickly solidify around the head, obstructing the consistent flow of these protective gases. Solidified spatter can also short out the contact tube to the gas nozzle, reducing the concentration and effectiveness of shielding gases.4 What's more, excessive turbulence – caused by spatter-obstructed gas – may contaminate the weld seam and, in extreme cases, lead to porosity.

The inevitable build-up of spatter impairs connectivity between these delicate torch head mechanisms, resulting in inconsistent electrical transfer and increased incidence of burnback (the formation of a weld inside the contact tip) - a chief source of operator downtime.

Selecting high-quality consumables is a vital first step to ensuring contact tips and diffusers can be secured in proper alignment, maximising the consistency of welds.5 However, judicious use of anti-spatter solutions is considered necessary to ensure adequate spatter resistance for delicate torch heads and consumables.

The problem with conventional nozzle anti-spatter treatments

Aerosol-based anti-spatter sprays have long been regarded as a versatile, cost-efficient, and fast-acting solution for overall spatter resistance. Yet despite industry-wide adoption, welders have been quick to recognise their limitations, particularly when applied on delicate torch head consumables.

Conventional nozzle anti-spatter sprays are formulated with an active silicone, petroleum or solvent base; owing to the volatile properties of each chemical base, these anti-spatter formulations are not only highly noxious, but require frequent and time-consuming re- application (upwards of 25 re-coatings per shift6) to ensure continual protection of welding equipment.

Indeed, one of the critical drawbacks of anti-spatter sprays is their poor performance on consumable surfaces. Being highly reactive to heat, conventional nozzle anti-spatter sprays evaporate quickly during the weld, offering little protection against spatter accretions in the torch head; the necessary manual removal of spatter build-up requires frequent operational stoppages (every 15-30 minutes), a major drain on productivity.

What's more, both silicone- and petroleum-based solutions are notorious for the deposition of greasy residues across the weld torch, extending the post-weld cleanup time significantly.

Of course, whilst anti-spatter 'Tip-Dips' provide a more reliable alternative for the protection of torch heads (offering excellent thermal properties), these cream- based solutions are not only difficult to apply, but leave behind unseemly residues.

The question remains: is there a viable alternative to 'anti-spatter' that can be applied across small- and large-scale industrial processes?

'Ceramic Shield': superior nozzle spatter protection for the modern welder

Owing to their exceptional thermal and micro-spatter resistant properties, composite ceramic coatings have seen widespread adoption in precision laser drilling and laser welding applications over the last decade.

Consumable producers have been quick to recognise the outstanding potential of ceramic-based aerosols as a safe and highly effective spatter-repellent for a broad range of welding equipment, offering marked benefits over traditional nozzle anti-spatter sprays.

Independent studies reveal that even low concentrations of ceramic particles can vastly improve the resistant properties  of  conventional  anti-spatter  coatings.

Indeed, numerous spatter tests have shown that while 0 per cent ceramic concentrations (silicone elastomer base) sustained 'excessive transverse burning' across coated surfaces, a progressive increase in ceramic filler saw drastic improvements in the spatter resistant properties of the coating: at 36 per cent ceramic filler concentrations, coated surfaces revealed next-to-no spatter deposition.7

Due to their unique low-residue and thermally resistant properties, ceramic-based sprays can be freely applied across all welding equipment surfaces – including torches, consumables and welding robots – with minimal post-weld cleanup.

Resistant to the heat extremes of the welding torch, ceramic sprays provide unsurpassed spatter- resistance for shrouds and contact tips, drastically reducing cleaning time (a nearly 20-fold decrease) and replacement costs.

While conventional anti-spatter nozzle sprays require continuous re-application (up to 25 re-coatings per shift), a single application of ceramic shield for contact tips and shrouds can resist spatter incursions for up to 8 hours (including the thermal extremes of the torch head), allowing uninterrupted welding for a full workday.

In terms of real-world commercial benefits, ceramic shields offer unrivalled efficiency and cost dividends for business: industry surveys reported a 7 per cent increase in productivity and a 40 per cent reduction in running costs for consumables as a direct result of using ceramic-based sprays.

References

  1. H. T. Goud, 'Minimizing Excessive Spatters in MIG Welding', Badve Auto Company.
  2. Bernard Welds, 'MIG Gun Mythbusting: Separating Fact From Fiction', Bernard Welds, 2012. http://www.bernardwelds.com/mig-gun-mythbusting--p152081#.U84YN_mSyXx
  3. Ibid.
  4. L. F. Jeffus, Welding: Principles and Applications, Cengage Learning, December 2002. pg. 266.
  5. Bernard Welds, 'MIG Gun Mythbusting: Separating Fact From Fiction', 2012.
  6. Loctite UK, 'Loctite SF 7900 Ceramic Shield', 2014, http://www.loctite.co.uk/loctite-sf-7900-ceramic-shield-8880.htm
  7. D.K.Y. Low, L. Li, & P.J. Byrd, 'Combined Spatter and Hole Taper Control in Nd:YAG Laser Percussion Drilling', in Laser Materials Processing, ICALEO 2000 Proceedings, Vol. 89, Laser Institute, pgs 11-20; D.K.Y. Low, L. Li, P.J. Byrd, 'Spatter prevention during the laser drilling of selected aerospace materials', Journal of Materials Processing Technology, Vol. 139, Iss. 1–3, 2003, pgs 71–76.