Specifying a degassing and refining unit for lighting-fixture castings starts with the alloy and the section thickness: thin-wall LED heat-sink housings (typically 1.5-3.0 mm wall) in A380 or ADC12 diecasting tolerate less than 0.15 ml/100 g hydrogen before porosity forms under the polished reflector surface [S2].
Buyers pairing molten-metal treatment with downstream lighting equipment and electric lamps assembly lines should treat the degasser as a process guarantor for surface finish, since cosmetic defects on diecast lamp housings are the single largest QA-reject category reported by industrial-lighting suppliers [S5].
Alloy Window and Hydrogen Target
A380, ADC12, and the AlSi9Cu3 family used in lamp housings all share a solidification range narrow enough that hydrogen above 0.20 ml/100 g produces visible subsurface porosity in sections below 2.5 mm [S2]. Most OEM datasheets for decorative and outdoor luminaires call for hydrogen at or below 0.10 ml/100 g, which sets the practical operating ceiling for the refining step [S4].
Aluminium-road and high-mast floodlight housings exposed to outdoor humidity (Stanley Electric LEDSHIGHMAST LLF0059A, 460 W) sit in IP65+ enclosures, so internal porosity that would otherwise be cosmetic becomes a long-term moisture-ingress path; the refining step therefore also drives lifetime, not just appearance [S4].
Process Criteria: Rotor, Gas, Time
For a 250-400 kg furnace common to mid-size lighting-fixture foundries, the working envelope is a 1.5-3.0 kW graphite-rotor degasser turning at 80-200 rpm with argon flow of 10-25 L/min for 6-12 minutes per batch; this configuration typically pulls dissolved hydrogen from 0.30-0.45 ml/100 g down to 0.08-0.12 ml/100 g [S2].
Flux addition (typically 0.1-0.3 wt% of a Na- or Sr-bearing cover flux) is used when the alloy shows more than 0.05 wt% Na pickup from prior charges, a common issue on recycled-scrap lighting-fixture melts [S2].
Comparison of In-Line Options
Three configurations dominate the lighting-fixture foundry market, and the choice is driven by batch size and alloy mix rather than by brand preference: (1) rotary-lance degassing, 1.5-3.0 kW, 80-200 rpm, suited to 200-500 kg batches, lowest capital cost; (2) in-hearth rotary degasser integrated with the hydraulic power unit of a tilt furnace, 3.0-5.5 kW, 60-120 rpm, better for 500-1500 kg production runs with higher alloy churn; (3) SNIF-style multi-station in-line degassing for high-volume OEM suppliers running the same A380 grade continuously, 7.5-15 kW per station, 250-400 rpm, but requiring a sand-handling and sand reclamation unit downstream if the foundry also runs sand cores [S2].
For most lighting-fixture plants running three to five diecasting cells on A380 or ADC12, option (1) hits the lowest total cost of ownership because the same degasser can serve two furnaces on a shared FRL unit for pneumatic rotation, while option (2) only pays back above 30 t/day throughput [S2][S5].
What Buyers Get Wrong
Specifying rotor diameter and gas flow without locking rotor immersion depth is the most common source of under-performance: at less than 60% immersion, hydrogen removal efficiency drops 30-40% even at full argon flow, and operators compensate by extending cycle time, which then erodes furnace temperature and downstream diecasting cycle stability [S2].
A second common miss is ignoring the degassing unit graphite-rotor service life under recycled A380 scrap, which carries Fe and Mn contamination; rotors in such service typically last 200-300 cycles versus 600-800 in primary alloy, so a spare-rotor kit and a documented replacement schedule should be written into the purchase spec, not treated as a consumable footnote [S2].
Standards and Documentation Buyers Should Reference
For foundries shipping castings into lighting-fixture assemblies that carry CE or UL listings, the refining process record (alloy batch, gas type, flow, time, pre/post hydrogen) is the audit trail; keeping it machine-logged rather than paper-clipboard is what separates OEM-tier suppliers from job-shop tier in 2026 lighting-fixture sourcing [S4].
Foundries should also be asked to declare their hydrogen-measurement method (reduced-pressure test, RPT, or inline Telegas probe), since a Telegas reading of 0.10 ml/100 g and an RPT reading on the same melt can differ by 0.04-0.06 ml/100 g, and that gap regularly shows up in supplier comparison tables on large road-lighting and high-mast tenders [S2][S4].
Adjacent Casting Programs Worth Cross-Referencing
Lighting-fixture foundries that also run pump and valve bodies, or that supply agricultural-machinery castings on the same furnace line, can reuse the same degassing envelope and reduce qualification overhead by aligning specs with the pump and valve degassing guide and the agricultural-machinery casting selection notes.
Plants that occasionally run aerospace-grade heatsinks alongside commercial luminaires should expect a tighter hydrogen ceiling (typically below 0.08 ml/100 g) and may need to size the rotor one step up; the aerospace aluminium casting reference gives the higher-spec envelope so the lighting buyer can decide whether the same unit can straddle both programs or needs a dedicated station.
Track two signals over the next procurement cycle: graphite-rotor lead time from the dominant Chinese suppliers (typically 4-6 weeks, with occasional 10-week stretches on 150 mm-diameter shafts) and the spread between argon and nitrogen contract pricing in the buyer's region, which swings the operating-cost line of any rotary degasser by 8-12% year over year [S2][S5].