Neutral, all purpose flux BF 8.5 for SA-surfacing (hardfacing) of low alloy steels

Flux type: Fluoride–Basic

ISO 14174: S A FB 1 65 AC
(EN 760: SA FB 1 65 AC)


A semi–basic, agglomerated, flux for shape–and overlay welding with single or multiwire (TWIN–ARC) submerged-arc processes. BF 8.5 shows stable metallurgical reactions and constant operating characteristics over a wide current range, also when AC-power is applied. Low flux consumption, high resistance to porosity as well as low hydrogen potential and low sensitivity to arc–blow are typical for this flux.
The weld deposits exhibit smooth surface, good wetting and self-lifting slag detachability without “tiger-tracks”, even at high welding temperature (> 300°C).
BF 8.5 is a non-alloyed, neutral flux with little pick–up of silicon and neutral manganese reactions (see chemical composition of weld pads).


The flux can be welded DC (electrode positive or negative) or AC in combination with appropriate solid or, especially, metal-powder cored wires as commonly used for hardfacing.
BF 8.5 is formulated specifically for build-up or shape-welding (in combination with standard CMn-/ CMo-/ CCr-Mo-wires) to restore worn surface to proper dimensions, or to profile the shape of a section.
This flux is not formulated for joining or groove welding. For these applications the basic fluxes BF 5.1, BF 16 or WP 380 (>5%Cr-alloys) are recommended.


All factors affecting the microstructure and chemistry during build-up and surfacing/hardfacing operations should be considered, such as:

  • Substrate metal: affects the choice of build-up wire / flux–combination and thermal treatment
  • Surface requirement: considerations in selecting the final hard layer(s)
  • Welding technology: influences dilution, chemistry and structure of the deposit

Characteristic chemical constituents

SiO2 + TiO2Al2O3 + MnOCaO + MgOCaF2
20 % 25 % 35 % 15 %
Basicity according to Boniszewski: ~2.0

Flux density: 0.95 kg / dm3 (l)
Grain size acc. to ISO 14174: 3 – 25 (Tyler 8 x 48)
Current–carrying capacity: up to 1,000 A (DC or AC) using one wire


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