It should not contain elements that hinder graphitization, such as chromium. This article only deals with some issues that should be paid special attention to in the production process after the use of carbon scrap steel is increased in the production of ductile iron in induction furnaces.5%, wMn = 0. The scrap is melted by about 50%, and the coke is covered with thick sheet scrap.03% to 0. Addition of pig iron = Addition of scrap steel × (carbon content required for ductile iron-analysis of carbon content) / (carbon content for pig iron-required carbon content for ductile iron) (2) Adding amount of recycled ductile iron to calculate the carbon equivalent of recycled ductile iron It is basically normal, and the amount of addition is not large.5%-2. There are many scrap steels on the market, pig iron is expensive, and high-quality pig iron is even more scarce. Composition adjustment application example: Using 1t induction furnace, producing pearlite ductile iron QT800-2, casting weight 1000kg. Ferrosilicon addition = [1000 (2. It cannot be crushed after being burnt. The sulfur content is low, the block size is 60-80mm, and it has high strength.5%-0.04%.3% + 600 × 1. This is because the nodular cast iron is melted in the induction furnace, the elements are not burned, and the iron is also burned. Manufacturers starting to use this method to produce ductile iron, it is better to be about 30%. (8) Properly increase the temperature of the molten iron, supplement the alloy elements according to the analysis results, and add ferrosilicon before the furnace temperature is reached. The precautions during the smelting process are as follows: (1) The coke block is installed at the bottom of the furnace, the purpose is to create a longer soak time of the coke block in the molten iron. Excessive use of scrap steel, if the carbon increase efficiency is not high, it will affect the carbon and silicon equivalent of the final product.8% + 100 × 2. The amount of pig iron added = 300 × (3.15%)] / 65% = 5.02%, wMg = 0. Among chemical components, carbon equivalent is particularly important. (2) The proportion of scrap steel mainly depends on the efficiency of increasing carbon. ②Waste electrode block. Therefore, after the return iron is added, the carbon content of the molten iron in the entire furnace is acceptable. 2. (2) Carbon enhancer ① High-quality coke.42% If the silicon increase amount of the spheroidizing agent is 0. In the traditional production process of ductile iron, about 10% of carbon scrap steel is generally used for batching. In this regard, the carbon equivalent can be adjusted with Z18 cast pig iron, and the total amount of charge can be supplemented with recycled ductile iron. (4) Nodulizers and inoculants are used in accordance with traditional processes, and are subject to the actual conditions of each plant. It is desirable to use high-carbon low-sulfur pig iron with wC> 4%. (4) The calculation formula for the addition of ferrosilicon is as follows: Addition amount of ferrosilicon = [total amount of charge × (required silicon content of nodular cast iron-inoculation silicon increase amount-nodular silicon increase amount-analysis silicon content)] / ferrosilicon Silicon content (5) The calculation formula of the addition amount of manganese and other alloying elements is as follows: Addition amount of alloy iron = total amount of furnace charge × (alloy content of nodular cast iron-analysis content) / alloying element content in alloyed iron . The above calculation does not include burning loss .38% and the manganese content was 0. (4) After the estimated carbon content is high enough, remove the coke block and electrode rod, and sample to analyze the carbon content. 3. Calculate the amount of pig iron added based on the analysis of carbon content.02% to 0. It is also possible to use 60-80mm waste electrode blocks instead of coke and install it at the bottom of the furnace as a carbon enhancer. (7) After the furnace material is melted, sample and analyze the content of Si, Mn and other alloy elements. It should not contain anti-spheroidizing alloy elements.06%, wRE = 0. The control chemical components are: wC = 3. Therefore, the chemical composition must be strengthened and carefully adjusted, and "fixed ratio production" should not be adopted.5%, wSi = 2. (6) According to the estimation of silicon content, it is decided whether the total amount of molten iron can be made up with recycled materials.15%.5%. It is better to have a certain length to facilitate skewing into the molten iron. Therefore, we suggest that manufacturers with the production task of nodular cast iron can refer to the above-mentioned assumption and produce nodular cast iron by "steel instead of iron". (1) Calculate the amount of pig iron added.5%) = 600 (kg) blast furnace ductile iron usage = 1000-300-600 = 100 (kg) estimated silicon content = (300 × 0. According to the production practice, the author put forward his own views for reference of peers. Before the furnace analysis, the silicon content was 1. Smelting and smelting process flow: coke block + scrap steel → electrode block → warming → removing the coke block and electrode block → sampling and analysis of carbon content → pig iron → recycled material → sampling and analysis of Si and Mn → warming → ferromanganese + ferrosilicon → Released → gestation + spheroidization → pouring. After improving the carbon increase efficiency, gradually increase the proportion of scrap steel used. The sulfur content is lower, which is more beneficial to obtaining high-quality ductile iron.5%) × 100% = 1. (3) After the scrap steel is melted, the electrode rod is inserted, the temperature in the furnace is appropriately increased, and the carbon increase efficiency is improved. The amount of coke block is about 5% of scrap steel. If you encounter special circumstances, you should pay attention to burn damage. The added amount of spheroidal graphite cast iron = the total amount of charge-the amount of scrap steel added-the amount of pig iron added (3) The calculation formula of silicon content is as follows: silicon content ≈ [(scrap + pig iron + added amount of spheroidal graphite cast iron) × silicon content / charge Total] × 100% ≤Original molten iron allowed silicon content. (3) Pig iron is mainly used to adjust the carbon content of molten iron. 1. The block size of the scrap steel should be about 30% thick and can be placed flat in the furnace.5%-0.6kg Ferromanganese addition = [1000 (0. (5) Based on the analysis results, calculate the amount of pig iron added and the amount of recycled ductile iron used.5%) / (4%-3.4%, the silicon content of the original iron solution should be 1. The silicon content in the pig iron is suitably higher and better, and the production of nodular cast iron can add less ferrosilicon. Selection of furnace materials (1) Scrap steel The scrap steel used for the production of ductile iron should be carbon scrap steel. (10) Spheroidization, inoculation and pouring are carried out as usual.5%, wP <0.. In fact, the carbon equivalent of spheroidal reducer copper tube factory graphite cast iron is adjusted so that the molten carbon equivalent of both pig iron and scrap steel reaches the carbon equivalent required by spheroidal graphite cast iron.38%)] / 75% = 1. The chemical composition is the internal cause, the fundamental, and the variable, almost every furnace is different. When the estimated silicon content is too high, reduce the amount of spheroidal graphite cast iron in the furnace, and use the equivalent ratio of 9: 1 pig iron and scrap to make up the total charge.5%, high For estimating silicon content.4kg Conclusion In the production of induction furnaces, we use scrap steel to produce QT800-2 with a strength of 800 to 1000 MPa and an elongation of> 4%. Composition adjustment calculation As we all know, the mechanical properties of ductile iron mainly depend on the chemical composition, cooling rate (as-cast ductile iron) and heat treatment process. Especially for the ductile iron produced using scrap steel as the main charge, the carbon increase efficiency is difficult to control and the carbon equivalent fluctuates greatly, so special attention should be paid to adjusting the carbon equivalent. However, the furnace temperature is too high, increasing power consumption, is also detrimental to the furnace lining.4%-1. The carbon content of the "scrap steel" in the furnace after carbonization is 2.6%-0. (9) The ferrosilicon melts to the molten state and is released immediately.6% and the silicon increase amount of the inoculant is 0. The composition of the charge used is shown in the attached table.07%, wS <0
