Safety technology of the hottest metal smelting an

2022-07-25
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Safety technology for metal smelting and hot working

the production process of metal smelting, casting, forging and heat treatment is accompanied by high temperature, and emits various harmful gases, dust and smoke. At the same time, it also produces noise, which seriously worsens the working environment and working conditions. These operations have many working procedures, heavy physical labor and heavy lifting and transportation workload, so they are prone to various injury accidents, and targeted safety technical measures need to be taken

I. safety technology for metal smelting

(I) high temperature and heatstroke

metal smelting operations, such as steelmaking and ironmaking, are carried out at high temperatures above 1000 degrees. When working at high temperature, the human body is affected by high temperature, resulting in a series of physiological changes, such as the decline of temperature regulation function. When the production environment temperature exceeds 34 ℃, heatstroke is easy to occur. If the labor intensity is too high and the continuous labor time is too long, the vanadium battery is more prone to heatstroke. Severe cases can lead to shock

the measures to prevent heatstroke are to reasonably design process flow, improve production equipment and operation methods, and eliminate or reduce the impact of high temperature and thermal radiation on human body. This is the fundamental measure to improve the working conditions of high-temperature operation. Heat insulation with water or materials with small thermal conductivity is also an important measure to prevent heatstroke. Mechanical ventilation and natural ventilation are economical and effective ways of heat dissipation

(II) explosion and scalding

in order to improve efficiency and reduce consumption, steel plants often adopt measures to strengthen smelting, such as pulverized coal injection and oxygen blowing, which makes molten steel, molten iron splashing and explosion accidents prone to occur in steelmaking and ironmaking production

there are many reasons for splashing and explosion of molten steel and iron. Unsafe factors are hidden in the whole production process of producing molten steel and iron from raw materials. Preventive measures must be strengthened for each process

1. All production personnel must master the production rules, be familiar with the operating procedures, carefully observe the accident precursors and understand the handling methods

2. Strengthen the management and selection of raw materials, and strictly prevent explosives and sealed containers from entering the furnace

3. Check the cooling system frequently to ensure that the protection system is unblocked. Control the cooling water pressure and water volume to prevent the steel plate from burning through due to insufficient strength of the water cooling system, resulting in the explosion of molten steel when encountering water

4. The ironmaking workshop shall strictly implement the working system of hot blast stove to prevent the explosion of hot blast stove due to furnace replacement accident; The steelmaking workshop shall strictly implement the operating procedures for the whole production process from furnace mending, furnace charging, smelting to tapping to avoid splashing and explosion accidents during smelting due to improper operation

5. During iron and steel tapping, the iron trench, molten iron tank, ladle, pit and ingot mold shall be heated and dried in advance. Strictly prevent explosion due to humidity according to relevant information and actual use

(III) gas poisoning

the main harmful component in gas is carbon monoxide. In steelmaking and ironmaking production, especially in ironmaking production, the exhaust gas, namely blast furnace gas, contains very high carbon monoxide. Therefore, in steelmaking and ironmaking production, gas poisoning accidents are likely to occur if it is not handled properly. The effective prevention method is to strengthen the ventilation, monitoring, maintenance and personal protection at the production site

II. Casting safety technology

(I) characteristics of casting production

the manufacturing method of injecting molten metal into a mold or metal mold made of molding materials and adhesives to obtain molded castings is called casting. When foundry workers deal with cupola and electric furnace, if foreign matters are mixed in the molten metal or water is encountered, explosion and scald accidents may be caused. In addition to casting machinery and equipment, a large number of lifting and transportation machinery are used in casting production, which is prone to mechanical injury accidents. Some processes of casting operation have a large amount of manual work, which is prone to collision accidents. Melting, pouring, sand falling and other processes will emit a lot of heat, affecting the health of workers. Vibrating Sand shaker, roller and pneumatic tools shall be used for sand removal, which may cause great noise and occupational deafness. Sand grinding, sand returning, boxing and sand falling generate a lot of dust. If there are no dust prevention measures, workers are prone to silicosis. During the core drying, smelting, pouring and other processes, there is oil decomposition, which will emit acrolein vapor, carbon monoxide, carbon dioxide and other toxic and harmful gases. Without ventilation measures, respiratory tract inflammation and acute conjunctivitis may be caused

(II) safety technology for metal melting

1 The main equipment for melting cast iron is cupola. The key points for safe operation are:

(1) pay attention to prevent the furnace lining from collapsing and damaging the head during furnace repair. Prevent flying debris from injuring eyes and face during slagging. When working, stand firmly, pay attention not to pour the furnace bottom, and pay attention to prevent gas poisoning and other mechanical injuries. Before furnace repair, the furnace temperature shall be lower than 50 ℃. During operation, safety helmet shall be worn and supervised by someone. Protective plate shall be set at the feeding port and 12V lighting lamp shall be used. Blowing is not allowed during furnace repair, but all air holes on the furnace shall be opened

(2) the bottom coke shall be handled carefully before ignition. After adding the bottom coke, open all the tuyeres, iron taps and slag taps of the cupola, and then ignite to prevent carbon monoxide poisoning

(3) before feeding, it is necessary to wait to check whether the mechanical parts are firm and flexible; Fences shall be set near the material transportation route, and pedestrians are strictly prohibited to pass through or close to the loading machine; When the loader is running, it is better to set a warning board or light a red alarm light; The cupola feeding port shall be 0.5m higher than the feeding platform, and the feeding platform shall be kept neat and clean; When weighing materials, carefully check to prevent explosives from mixing into the furnace

(4) during the blowing and melting operation, the operator shall wear protective glasses and stand at the side of the air nozzle to monitor. If the furnace shell is red, stop feeding and air supply immediately. Watering is strictly prohibited; When the burned area is not more than 75 square centimeters, it can be cooled by blowing

(5) during iron and slag tapping, there shall be no moisture or moisture around the cupola, especially the iron tapping pit and slag chute shall be very dry. If there is ponding, it must be drained and paved with dry sand of appropriate thickness. All tools used must be coated and dried to prevent scalding

(6) the ground must be paved with dry sand to keep dry when the air is stopped and the furnace is fired; No one is allowed to stand around; The operator stands on the windward side of fy17. After the furnace is fired, the red hot iron block and coke shall be taken out quickly. It is not allowed to use water to spray out, so as to avoid gas returning to the cupola and causing furnace explosion

2. During the production of cast steel, the widely used smelting equipment is the electric furnace, and its key points for safe operation are:

(1) before discharging, the inclination of the electric melting furnace shall not exceed 45, and during slag removal, it shall not exceed 15 ~ 20. For this reason, the electric melting furnace shall be equipped with an inclination limiter, and the tilting worm drive mechanism shall be self-locking

(2) the charging port frame and electrode base of the electric melting furnace shall be equipped with a water cooling circulating device, and the return water temperature of the cooling water shall not exceed 45 ℃. The high-pressure part of the electric melting furnace shall be set in a special control room. For the smoke and dust of electric melting furnace, the measures of furnace smoke exhaust and furnace smoke exhaust can be taken

(III) safety technology of metal casting

the main tool for metal pouring is the ladle, which contains high-temperature metal melt. The operation has certain different dangers from the previous emphasis on advanced weapons and landing operations directed at specific military targets. Pay great attention to safety. The rotating shaft of the ladle shall be provided with a safety device to prevent accidental inclination. During pouring, after the ladle is full of molten iron, the center of gravity should be more than 100mm lower than the rotating shaft. The ladle with a capacity of more than 500kg must be equipped with a rotating mechanism and can be self-locking. The ladle rotating device shall be provided with a protective shell to prevent the splashing metal from entering and getting stuck

pay attention to the quality inspection and test of ladle. Crane ladle shall be inspected and tested at least once every half a year; Hand lift ladle shall be inspected and tested once every two months. The crane ladle shall be subject to appearance inspection and static test. The key parts are reinforcement ring, ladle shaft, pull rod, frame, lifting ring and tilting mechanism. The particularly important parts shall be carefully inspected with magnifying glass. Before inspection, remove dirt, rust spots and oil stains. If the parts are found to have cracks, cracks, bends, poor connection between welds and bolts, unreliable connection of rivets, etc., they must be replaced or repaired. The static test method of the ladle is to hoist the ladle to the minimum height, and the test load is 125% of the maximum working load of the ladle, lasting for 15 minutes; The test load of portable ladle is equal to 150% of its maximum working load. If no other defects and permanent deformation are found in the inspected and tested ladle, it is qualified. The ladle shall be dried before use, and the liquid level of molten iron shall not exceed seven eighths of the ladle height. When using the hand-held ladle, the load per person shall not exceed 30 meters. In order to ensure the safety during pouring, the main channel shall be 3 meters wide, and the ladle shall take a circular road; Tongs, iron bars, hooks and additives (silicon angle, aluminum, spheroidizing agent, etc.) must be preheated; Before pouring, check whether the pressure iron is firmly pressed and whether the bolt clamp is tightly clamped; The manual lifting of the ladle shall be carried out at the same pace and with the same coordination, and the gate shall face outward when lifting; The pouring shall be carried out with a crane. The driver and the crane commander shall comply with the crane movement signal and operate stably. The lifting height of molten iron ladle shall not be greater than 200mm; During pouring, the ladle shall be as close to the opening ring as possible to prevent molten iron from pouring on the pressed iron or the ground; When the height of the sand box is higher than 0.7m, a pit shall be dug; When pouring large sand mold, pay attention to the bottom ventilation, and the ejected carbon monoxide will be ignited and burned; The remaining molten metal can only be poured into ingot mold and sand mold; Before pouring, the ingot mold shall be preheated to 150 ~ 200 ℃, and the sand pit shall be dry. (end)

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