The surface color difference problem of copper plated alloy welding wires was studied by SEM,EDS etc.It was found that for alloy welding wire steel with high Si content,such as ER70S-G,iron oxide scale with Fe2SiO4 and oxide cracks were prone to appear on the surface of the cast billet,which were difficult to remove.After rolling and wire rod drawing,they were inherited to the surface of the welding wire,causing poor copper plating and resulting in surface blackening.The relationship be-tween Fe2SiO4,iron oxide scale,oxide cracks and the heating temperature,heating duration,and residual oxygen content was studied.When the heating temperature was above 1 150 ℃,the proportion of Fe2SiO4 in the iron oxide scale significantly in-creased.Under 1 100 ℃,oxidation reactions continued to occur and oxidation cracks significantly depened with the prolongation of heating duration.The higher the residual oxygen content in the furnace,the faster the oxidation rate of the billet.The oxida-tion rate of billets under a 10％residual oxygen content was four times that of a 2％residual oxygen content.To solve the color difference troubles,two retaining walls were added to the heating furnace and a special billet loading method is adopted.Thus the heating duration is cut down to be about 80-90 minutes.The temperature of furnace entrance is decreased to be less than 750 ℃.The first heating stage temperature is about 770-820 ℃,the second heating stage temperature is about 950-980 ℃,and the uniform heating stage temperature is about 1 050-1 100 ℃.This heating process solves the surface blackening problem of the high Si content welding wire products.
welding wiresurface color differencewire rodiron oxide scaleFe2SiO4heating furnace charging rulesheating process
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