6/29/2023 0 Comments Co iron charge![]() Neutralizing all iron oxide in the cover slag stabilizes chemistry because Iron oxide is converted into inert by-products. DeOX stops both carbon and silicon oxidation by stabilizing chemistry in both EF and cupola operation. Chemistry variations, heat to heat, result from oxidation loss. In cupola melting, the classic excuse for low carbon and silicon levels is “the cupola is oxidizing today” or a "a double charge must have happened." In electric furnace melting, “poor carbon” or “low-purity silicon carbide" are the standard explanations. Misunderstanding chemistry - Many explanations surface when molten iron chemistry is out-of-spec. One melting supervisor reported Mastermelt DeOX tuyere injection puts the cupola on “cruise control” for chemistry control throughout the melt campaign. When injected carbon or silicon carbide produces full recovery in molten iron, melting personnel are afforded a very viable tool for trimming chemistry precisely. Unfortunately, many (if not all) of those users proved unequivocally coke breeze is ineffective for controlling iron chemistry, though some suppliers still recommend it. Many of those systems injected “injection carbon,” which turned out to be coke breeze. When Mastermelt first introduced SiC tuyere injection many suppliers and foundries followed suit and start injecting none of the competing SiC injection systems proved successful. The properties develop during production of the material and are reset when production concludes. Carbon and silicon-carbide’s entry rates into molten iron are inherent properties of the material. The governing forces controlling the rates these materials enter into molten iron are complicated, best left to scientists and crystallographers. Without full recovery, chemistry control deteriorates further.īoth carbon and SiC are commonly tuyere-injected, and both materials are unique: They do not melt but enter into molten iron via an atomic exchange at the molten-metal interface. It is pointless to inject SiC and carbon materials that do not provide full carbon or silicon recovery. Mastermelt engineers spent two years developing the technology and skill needed to determine the specific materials that can be injected effectively. Trimming chemistry - Both carbon and silicon-carbide can be injected to trim the cupola metal chemistry. Carbon must possess an equally high dissolution rate in molten iron and no commonly available graphite carbon raisers meet this qualifying standard. SiC must possess a high dissolution rate in the molten iron, and only a few grades of SiC qualify. Simply, lower-quality materials do not work and using them discredits tuyere injection as a reliable melting tool. The materials to be injected must be "injection-grade" and "injection-quality": Standard-grade silicon carbide (SiC) and graphite do not qualify. Then, silicon and carbon can be injected in any amounts needed to trim the chemistry. Tuyere injection can be used to counter oxidation losses in a cupola, in addition to supplementing carbon and silicon in molten metal exiting the cupola. One-hundred-ton-per-hour cupola furnaces have been operated for entire daylong campaigns with carbon variation of 0.01% C, and such exceptional chemistry control is possible with any melting operation. Oxidation must be controlled in order to attain “straight-line” chemistry.Ĭan carbon be controlled to produce straight-line chemistry? Unequivocally, yes. It is a simple analytical comparison: Chemistry will vary by 50% when a 50% oxidation loss occurs. The wide variations in metal chemistry faced by some ferrous foundries are caused by oxidation loss of the key elements. You must experience melting without oxidation loss to appreciate the significance of this. Unwanted weight variations in charge ingredients, which frequently are assumed to lead to chemistry variations, in fact are a minor influence in most melting operations. ![]() Oxidation losses cause 99% of all chemistry variations in molten iron. (2) Chemical reactions (slag/metal reactions) that occur during the melting process and cause unpredictable and widely varying loss of C, Si, MN and other necessary elements. (1) Accuracy of the weight of individual metallic and alloy ingredients in the charge and, Molten iron chemistry variations result from two primary sources: Melting is not simply the process of re-melting existing metallic materials: Slag-induced influences during the melting process - caused or produced by the slag/metal chemical reaction - have a consequential role in iron chemistry and finished metal quality Unfortunately, formulating the charge does not determine the final chemistry or quality of the molten iron. The ingredients of a furnace charge, whether it is an electric furnace or a cupola melter, are formulated to produce the final chemistry required for the castings to be poured. ![]()
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