The most harmful impurities in tin bronze are aluminum, silicon and magnesium. When their content exceeds 0.005%, the inclusion of SiO2, MgO and Al2O3 oxides will pollute the melt and reduce the performance of certain aspects of the alloy.
When smelting tin bronze, because zinc has a relatively low boiling point and has a greater affinity for oxygen, it should be deoxidized and then melted in the furnace. Chuangrui tin bronze plate can supplement deoxidation by zinc, which is more helpful to avoid The danger of SnO2 production. The zinc and phosphorus in the melt have a comprehensive deoxidation structure, and the resulting 2ZnO·P2O5 is easier to separate from the melt, and it is helpful to improve the fluidity of the melt.
The use of dry charge, even preheating the charge before melting, can reduce or even avoid gas absorption by the melt. The proper ratio of new metal and process waste is also conducive to stabilizing the quality of the melt. The amount of process waste should generally not exceed 20% to 30%. The melt slightly contaminated by impurities can be oxidized by blowing in air or by adding an oxidizing agent (such as copper oxide CuO). Waste materials that are heavily contaminated by certain impurity elements can be refined by solvents or inert gases, including remelting treatment, to improve their quality.
Appropriate feeding and melting sequence, including the use of a power-frequency iron core induction electric furnace with the function of intensively stirring the melt for smelting, are all conducive to reducing and avoiding segregation. Adding an appropriate amount of nickel to the melt is beneficial to accelerate the solidification and crystallization speed of the melt, and has a certain effect on reducing and avoiding segregation. Similar additives, zirconium and lithium can also be selected. It is possible to adopt a mixed smelting method of separately melting copper and lead, and then injecting the lead melt into the copper melt at 1150 to 1180°C. Under normal circumstances, smelting tin bronze containing phosphorous mostly uses charcoal, or petroleum coke and other carbonaceous materials to cover the melt, instead of using solvents. The covering agent used when smelting tin bronze containing zinc should also include carbon-containing materials such as charcoal. During continuous casting, it is appropriate to control the tapping temperature at 100-150°C above the alloy liquidus.
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