Prior to smelting, the chemical composition of all metal charge must meet the requirements, clean appearance, no oil and sand. Before entering the furnace, it should be preheated to 200-3000C. The new graphite crucible should be slowly heated up to 900°C for calcination before use. The old trowel should first check for damage, and then remove the slag and metal attached to the rake. Preheat to 500-600T before loading. All tools that come in contact with the zinc alloy must be cleaned, sprayed, and fully dried before use. The recipes for paints for crucibles and tools are shown in Table 14-3.
The zinc alloy melting process is simple and easy, does not require special slagging and degassing treatment, and does not require the use of special covering agents. Melting speed, high melting efficiency, low energy consumption. In order to limit the introduction of harmful impurities, the purity of the raw materials is required to be high. In addition, the charge materials must be placed in isolation from the aluminum alloy and the copper alloy when preparing the materials. The melting process should be stirred up and down to avoid segregation of specific gravity. The melting should be rapid and should not be overheated.
When melting, care must be taken to keep the solution clean, raw materials must be pure, and be clean. All containers that come into contact with liquid metal should be coated with paint to prevent impurities on the container or tool from entering the solution; water vapor should be avoided, and all tools used should be baked. Intervention of heat to remove water vapor, to prevent liquid splashes and injuries during work, and product porosity defects, preheat temperature around 200 °C, strictly control the pouring temperature.
The smelting processes of various alloys are basically the same (the selections for p-steps, specific raw materials, modifiers, and refining agents are somewhat different). The process is divided into pre-melting preparation, charging, melting, adjusting chemical composition, refining, modification, and adjustment. Temperature, pouring these steps. When burning ingredients must consider the burning rate of various elements according to 14-4)
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1. Gravity Casting Alloy Melting Gravity casting alloys are melted by the intermediate melting method and the direct melting method. In the intermediate melting method, the added alloying elements are previously melted into an intermediate alloy to prevent oxidation loss of the elements. The direct melting method is a method of directly adding the desired constituent material.
The melting point of the master alloy made of copper with a melting point of 1080°C and aluminum with a melting point of 660°C can be reduced to a melting point of between 600 and 65,000, and the ratio of copper to aluminum is generally (2-3): 4 . Generally, the resistance site is melted. The graphite crucible is preheated to about 200° C. and the coating is applied 2-3 times. After drying, the broken aluminum ingot is placed in the crucible coated with the paint. When heated, charcoal powder can be sprinkled in the Citrus Scroll. After the aluminum is melted, the preheated electrolytic copper is added to the molten aluminum, and then stirring is continued to completely dissolve the copper block in the molten aluminum.
After the copper is completely dissolved, it can be de-energized and refined. Commonly used refining agents are zinc chloride or hexachloroethane. Because the density of the refining agent is smaller than that of the alloy, the bell should be pressed down to make the refining agent react with the alloy when it is added. The refining agent is generally packed with paper and then pressed. After the refining is completed, the charcoal and slag can be removed by pouring into the ingot.
The thickness of the cast intermediate alloy ingot is 40-50mm, too thick will increase the difficulty of crushing.
When melting the zinc-based alloy with the master alloy, one-third of the desired mass of zinc ingot is loaded into the furnace. The temperature was set at 6500C. After the zinc was melted, charcoal powder was sprinkled on the surface.
The aluminum-copper master alloy is gradually added to the molten zinc solution, and stirring is continued. After the master alloy is completely dissolved, it can be de-energized, and then the preheated aluminum foil-wrapped magnesium is pressed into the bell jar. The bottom of the furnace is agitated and finally slagging is removed with a refining agent.
When the furnace temperature drops to about 450°C, it can be poured.
The specific operation of the intermediate melting method of zinc-aluminum alloy is as follows: first, the copper is placed in a crucible to be heated and melted, then the heating is stopped, and an aluminum block is added to the copper liquid for stirring. When the temperature drops to about 700°C, zinc blocks can be placed. After the zinc is melted, the magnesium is wrapped into the bottom of the furnace, and the alloy liquid is suitably stirred during the addition of the alloy to homogenize the components. After the alloy is melted, it is necessary to perform refining degassing treatment. Before casting, it is necessary to remove slag. The disadvantage of using this method to dispose the alloy is that the smelting temperature is high, zinc is easily oxidized, and the produced zinc oxide is unfavorable to human health. The specific melting method used may be based on actual production conditions.
2. Pressure Casting Zinc Alloy Melting Pressure Casting Zinc alloys are melted by direct melting and secondary melting.
In the direct melting method, the crucible is preheated to a dark red state with about 600 persuasions. The copper material is charged and melted by heating, and then deoxidized with 1.5%-2% phosphorous copper, after which all of the aluminum is added. After the aluminum is melted, add 90% of the zinc or 90% of the charge of the planned charge mass. The temperature was raised to 6500C, 0.1%-0.13% magnesium and 0.1%-0.13% zinc chloride were pressed into the liquid with a bell jar, and finally 10% zinc and all the returned charge were added.
In the secondary melting method, aluminum and copper are first melted into a Cu50Al5O or Cu67A133 master alloy. The melting of the aluminum-copper master alloy is carried out in a crucible furnace. After preheating the mandarin disaster, 2/3 of the total aluminum material is added first, then 1/3 of the total copper material is added, and the remaining material is placed on the furnace cover for preheating. After the aluminum is melted, spread the covering agent and continue heating to 700-800T to melt the charge completely. Add the remaining copper material to the address vortex. After the copper is completely melted, add the remaining 1/3 of the aluminum, and then use the zinc chloride. Or hexachloroethane deoxidation to residue. When the Zn-Al alloy is melted, 90% of the entire zinc material or return material is first loaded into the crucible, and the Al-Cu master alloy is added and heated to 65,000. At this point, 0.2% magnesium and 0.1%-0.12% zinc chloride were added and then the remaining 10% zinc or return charge was added. Finally, 0.05% zinc chloride was added to the furnace charge, and after standing for 5-7 minutes, the slag was poured. However, in this process, the melting time and melting temperature should be controlled properly. If the melting time is too long or the melting temperature is in the solidification zone, a large amount of molten slag will float on the upper part of the melt. The slag contains a large amount of aluminum. If the slag is removed, , will inevitably cause a substantial reduction in the amount of aluminum.
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