Lead-free Niello Alloy & Fusion Safety
无铅乌银配方与熔合安全
标签：无铅乌银, 熔合安全, REACH合规, 配方设计, 通风排烟
传统乌银含铅 10–20%，熔炼烟气与长期接触风险高。现代无铅配方取 Ag 55–65%、Cu 15–25%、S 12–18%，另加 3–5% 锌或铟把熔点降到 680–720℃；熔炼须在通风柜进行，含硫烟气经碱液喷淋塔吸收。无铅料流动性略差：基体预热至 300℃、以还原焰由一端推进熔填可减少夹气。试片经 500 h 人工汗液浸泡析出量达标。欧盟 REACH 与加州 65 号提案均要求成品标注无铅，此配方已成出口件主流。
Traditional niello carries 10–20% lead, with fume and contact hazards. A modern lead-free alloy runs Ag 55–65%, Cu 15–25%, S 12–18%, plus 3–5% zinc or indium to lower melting to 680–720℃; melt in a fume hood with alkaline scrubbing of sulfur fumes. The lead-free melt flows less freely—preheat the base to 300℃ and advance with a reducing flame from one end to avoid gas pockets. Coupons pass 500 h artificial-sweat extraction limits. REACH and California Prop 65 labeling make this the mainstream export formula.