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1、 Product quality requirements
High carbon ferrochrome is divided into four grades according to different carbon content, and its chemical composition shall comply with the provisions in the table.

Remarks: ① 50% chromium content of high carbon ferrochrome is taken as the benchmark assessment unit; ② The contents of chromium, silicon, carbon, phosphorus and sulfur must be measured for each batch of high-carbon ferrochromium. When the supplier can ensure that it meets the provisions of this standard, other elements may not be measured; ③ If the demander has special requirements for chemical composition, it can be separately agreed by the demander and the demander.


2、 Batching requirements


The charge is mainly composed of chrome ore, coke and silica. In order to improve the recovery rate, an appropriate amount of chromium rich slag can be added to the batch. In order to adjust the furnace condition and control the silicon content of the alloy, an appropriate amount of silicon chromium slag can be added to the batch. The ratio of raw materials shall be calculated by the furnace technician, reviewed by the technical team of the branch plant and agreed by the director of the production plant. When the chemical composition, moisture, slag alkalinity, furnace condition, etc. of the furnace charge change greatly, the smelting shift leader on duty can adjust the material ratio appropriately, fill in the material change notice, and submit it to the batching shift leader for implementation and storage. Under normal smelting conditions, it is strictly prohibited to change the material ratio. The batcher is responsible for checking the weighing apparatus before use and monitoring the operation of the batching equipment, observing the changes of raw materials at any time, and reporting the problems of equipment or raw materials to the team leader in time. It is required that all raw materials used shall be weighed accurately. According to the different weighing instruments used, the allowable error of weighing in each batch of materials shall be ± 2.5% of the batch weight of the mechanical platform scale; The electronic scale is ± 1.5% of the batch weight. In order to mix the burden evenly, the burden shall be proportioned in the order of coke, silica and chrome ore. For closed electric furnace, in order to prevent gas poisoning and fire accidents, the silo and material pipe shall be filled with furnace charge, and the furnace charge shall not be less than 8 silos. For open electric furnace, only two batches of materials can be prepared in the reserve silo above each material pipe at most. The proportion of raw materials, batch number of ingredients and quantity of additional materials on duty shall be accurately recorded on the production record card by the smelting team leader. The smelting team leader or technician is responsible for checking the accuracy of the batching process on duty and finding relevant personnel to deal with the problems immediately.


3、 Equipment maintenance


After the planned maintenance or temporary power failure of the electric furnace is cut off, the smelting team leader on duty must accept the maintenance work. After passing the acceptance, the maintenance personnel shall be required to evacuate, and the on-site personnel and electric furnace equipment shall be comprehensively inspected. After confirming that the power transmission conditions are met, the operator can be commanded to transmit power. During the production process, the smelting team leader shall often check the operation of the water cooling system of the electric furnace, and all waterways are required to be unblocked, with return water and no steam production (with measuring device, the water temperature shall not exceed 60 ℃, and the water pressure shall not be less than 0.20 MPA). In case of no water return or steam production, power off immediately and find maintenance personnel to deal with it on site. If water is found to enter the furnace, close the waterway valve immediately. Before each shift takes over and leaves work, the smelting team leader and deputy team leader must carefully check the electrode lifting system, electrode pressure release system, water cooling system and conductive system; The batcher is responsible for inspecting the batching system; The foreman in front of the furnace shall check the burners, tapping tools, tapping bags, tanks, cars, hoists and other equipment in front of the furnace. Strictly follow the shift handover system. All parts of the furnace cover, water jacket and material pipe shall be sealed tightly to prevent air from entering under negative pressure. When recovering gas, no one is allowed to open the operation hole.


5、 Smelting operation


1. Normal furnace condition characteristics


Electrode stability; Current balance; The furnace charge sinks evenly; The iron in each slag is uniform; Small fluctuation of furnace pressure; Do not stab fire; No material collapse; Fast material conversion; Smooth and balanced tapping and slag discharge; The furnace hole is easy to open and blocked.


2. Create conditions for normal furnace conditions


The concentrate is fed into the furnace, the ingredients are accurate, the mixture is uniform and the ratio is stable. Always keep the appropriate length of electrode working end. Generally, the length of 25000 KVA electric furnace is about 2200 mm, that of 12500 KVA electric furnace is 1600 ~ 2000 mm, and that of 5000 KVA electric furnace is 1700 ~ 1900 mm. The slag composition of reasonable slag type: SiO2 is about 28% ~ 30%, MgO is more than 30%, Al2O3 is 17% ~ 22%. Adopt reasonable secondary voltage. See transformer parameter table for details. Formulate a reasonable electrode lowering system, less and frequently, generally 60 ~ 100 mm per shift. Cr2O3 in slag is less than 5.0%. The smelting team leader shall often check whether there is material suspension in the material pipe and electrode, and deal with any problems in time. The electric furnace operator shall operate in strict accordance with the power supply system, keep the current and voltage stable, and pay attention to whether the electrode lifting system operates normally.


3. Treatment conditions of abnormal furnace conditions


The melting point of slag is low. Features: large amount of slag, good fluidity, thin furnace wall, easy opening and blocking of furnace hole, rapid decrease of current when discharging, sometimes insufficient load for a long time, and low silicon content of alloy. Cause: low carbon content or excessive silica. Treatment method: add coke or reduce silica in the batch.


High melting point of slag. Features: the electrode is often in the middle and upper limit position; The electrode still doesn't like to plug down after coming out of the furnace; Slow melting; Small amount of slag; Poor fluidity of slag; Furnace hole shrinkage; Thickness of furnace wall; The furnace hole is difficult to open and block; When discharging, iron comes first and then slag; Alloy silicon is high. Cause: insufficient silica and excess coke in the furnace. Treatment method: add silica or coke reduction in the batch, and add several batches of coke if necessary; In case of serious slag turnover, an appropriate amount of chrome ore can be added directly from the operation hole for treatment.


Furnace slag turning. Features: large current and voltage fluctuations; There is obvious arc sound in the furnace; High furnace temperature; There is a large amount of adhesive around the electrode; Sometimes the material pipe is blocked, and the silo will not discharge material. Reason: the melting point of slag is high and the slag cannot be discharged, which is caused by excess coke. Treatment method: reduce the amount of coke from the batch. In order to quickly reverse the furnace condition, several batches of coke fully reduced charge can be added.