Harm of argon arc welding to human body welding dust 1, possible occupational disease: welder's pneumoconiosis 2. Industry example: (1) Sporting goods manufacturing: copper tube punching (2) Machinery industry: manual arc welding, gas shielded welding, argon arc welding, carbon arc gouging and gas welding (3) Transportation equipment manufacturing: locomotive parts assembly and platform assembly. Safety technology of argon arc welding of ship anchor chain (IV) Processing, brake beam processing, automobile assembly and motorcycle assembly In addition to electric shock, burn and fire, argon arc welding also has much stronger high-frequency electromagnetic field, electrode radiation and arc damage, welding smoke and toxic gas than manual arc welding. The most important things are high frequency electricity and ozone. 1. Preventing high-frequency electromagnetic field damage 1. Generation and harm of high-frequency electromagnetic field In TIG welding and plasma welding, high-frequency oscillators are often used to excite the arc, and some AC TIG welding machines also use high-frequency oscillators to stabilize the arc. The frequency of the high-frequency oscillator commonly used in welding is 200-500 kilocycles, the voltage is 2500-3500 volts, the high-frequency current intensity is 3-7 mA, and the electric field intensity is about 140- 190 volts/meter. Long-term exposure of welders to high-frequency electromagnetic fields can cause autonomic nerve dysfunction and neurasthenia. It is characterized by general malaise, dizziness, dreaminess, headache, memory loss, fatigue, loss of appetite, insomnia and hypotension. According to the hygienic standard, the allowable radiation intensity of high-frequency electromagnetic field is 20 V/m after 8 hours of contact. According to the measurement, the intensity of high-frequency electromagnetic field in all parts of the welder exceeds the standard during manual TIG welding, and the strength of the hand is the largest, which exceeds the hygienic standard by more than 5 times. If the high-frequency oscillator is only used when the arc is started, it will have little influence because of the short time, but long-term contact is also harmful, so effective protective measures must be taken. 2. Protective measures for high-frequency electromagnetic field (1) As far as possible, transistor pulse devices are used for arc initiation and arc stabilization in argon arc welding, and high-frequency oscillation devices are not used, or only used for arc initiation. Cut off the high-frequency power supply immediately after the arc is ignited. ⑵ Reduce the oscillation frequency, change the parameters of capacitance and inductance, reduce the oscillation frequency to 30 kilocycles, and reduce the impact on human body. (3) Shielding cables and wires. Outside the cable hose (including the welding torch and wires connected to the welding machine), a thin copper cord should be sheathed and grounded. (4) Due to the high voltage of the high-frequency oscillation circuit, good and reliable insulation is required. Prevention of radiation damage 1. Sources and Hazards of Radiation Thorium-tungsten electrodes used in argon arc welding and plasma arc welding contain1-1.2% of thorium oxide, which is a radioactive substance and is affected by radiation during welding and when it comes into contact with thorium-tungsten rods. Radiation acts on the human body in two forms: one is external irradiation, and the other is internal irradiation through the respiratory and digestive systems. A large number of investigations and measurements of shielded argon arc welding and plasma arc welding have proved that the radioactive harm is less, because only 100-200mg thorium tungsten electrode is consumed every day, and the radiation dose is extremely small, which has little impact on human body. But there are two situations that must be paid attention to: first, when welding in the container, the ventilation is not smooth, and the radioactive particles in the flue gas may exceed the hygienic standard; Second, the concentration of radioactive aerosol and radioactive dust can reach or even exceed the hygienic standard where thorium tungsten rods and thorium tungsten rods exist. The invasion of radioactive substances into the body can cause chronic radiation sickness, which is mainly manifested in the weakening of the whole body function, obvious weakness, obvious decline in resistance to infectious diseases, weight loss and other symptoms. 2. Measures to prevent radiation damage (1) Thorium tungsten rods should have special storage equipment, which should be hidden in iron boxes when stored in large quantities, and exhaust pipes should be installed. ⑵ When welding with a closed cover, do not open the cover during operation. When operating manually, you must wear a protective helmet for gas supply or take other effective measures. (3) Grinding thorium-tungsten rods should be equipped with special grinding wheels, and dust removal equipment should be installed in the grinder. Debris on the ground of grinder should be cleaned by wet method frequently and buried intensively. (4) Wear a dust mask when grinding thorium tungsten rod. Wash your hands with tap water and soap after touching thorium tungsten rods, and wash your work clothes and gloves frequently. 5] Choose reasonable specifications when welding and cutting to avoid excessive burning of thorium tungsten rod. [6] Try to use cerium tungsten rod or yttrium tungsten rod instead of thorium tungsten rod, because the latter two are not radioactive. Prevention of arc damage 1. Harm of Arc Radiation Welding arc radiation mainly includes visible light, infrared light and ultraviolet light. They act on human body and are absorbed by human tissues, causing thermal, photochemical or ionization effects of tissues and damaging human tissues. (1) The wavelength of ultraviolet light is between 0.4 and 0.0076 micron. The shorter the wavelength, the greater the damage to organisms. Human skin and eyes are sensitive to excessive ultraviolet radiation. Under the action of strong ultraviolet rays, the skin will appear dermatitis, erythema, even blisters, exudates and edema, burning pain, itching, tenderness, blackening and peeling. Eyes are most sensitive to ultraviolet rays. Short-term exposure can cause acute keratoconjunctivitis, which is called electro-optic ophthalmia. Its symptoms include pain, sandy feeling, excessive tears, photophobia, fear of wind blowing, blurred vision and so on. And generally there will be no sequelae. The ultraviolet rays of welding arc have a strong destructive ability to fibers, especially to cotton fabrics. White fabric has strong reflection performance, so it has strong anti-ultraviolet radiation ability. The ultraviolet ray produced by argon arc welding is 5- 10 times that of manual arc welding, and the damage is more serious. Work clothes for argon arc welding should be acid-resistant woolen cloth, tussah silk and other fabrics. ⑵ The wavelength of infrared rays is between 343 and 0.76 microns, and the harm to human body is mainly caused by the thermal effect of tissues. Long-wave infrared rays can be absorbed by the human body, making people feel hot; Short-wave infrared rays can be absorbed by tissues, heating blood and deep tissues and causing burns. In the welding process, the eyes are exposed to intense infrared radiation, which will immediately produce intense burns and burning pain, and flash hallucinations. Long-term exposure may also lead to infrared cataracts, decreased vision and even blindness in severe cases. It can also cause retinal burns. (3) The light variation of visible light in visible light welding arc is more than 10000 times larger than that normally borne by naked eyes. My eyes hurt when I was irradiated, and I couldn't see clearly for a while. Usually called arc "glare", it loses its working ability in a short time, but it can be recovered soon. 2. Protection of welding arc light In order to protect eyes from arc light, welders must wear masks with special filters when welding. The mask is made of Kurogane cardboard, which is suitable, light, heat-resistant, non-conductive and does not leak light. The filter lens embedded in the mask, commonly known as black glass, is often used as an absorption filter lens, and its blackness should be determined according to the intensity of welding current, as shown in Table 10-2. At the same time, the welder's vision and the brightness of the welding environment should also be considered. Young welders have good eyesight. When welding at night or in a dark environment, it is advisable to use filter lenses with large color number and dark color, and dark lenses should also be selected. Table 10-2 Selection of color number and color of filter lens Applicable current (1) 9 shallow 350 has reflective protective lenses, which can reflect strong arc light. There is also a photoelectric lens, which can automatically adjust the light, and has good transparency when it is not arcing, so you can clearly see the scenery outside the mirror. When the arc is ignited, the blackness of the protective mirror immediately deepens, which can block the light well. In this way, when replacing the covering electrode, it is no longer necessary to lift the mask or turn over the protective glasses. In order to prevent the welder's skin from being damaged by electric arc, the welder's protective clothing should be light-colored or white canvas to increase the reflection ability of arc light. The pockets of work clothes should be dark. When working, the cuffs should be tied tightly, gloves should be worn outside the cuffs, the neckline should be buckled, the trouser legs should not be discounted, and the skin should not be exposed. In order to prevent auxiliary workers and other workers near the welding site from being injured by arc light, we should pay attention to mutual cooperation, say hello before striking the fire, and auxiliary workers should wear colored glasses. When welding in a fixed position, a shading screen should be used. Prevention of spatter metal burns In the process of arc welding, spatter of molten metal and slag and hot weldments may burn welders, and the burned skin will cause infection and ulceration. Therefore, welders must wear canvas overalls, working caps and long-sleeved gloves when operating, and wear work shoes. Work clothes should not be tied in the waistband, pockets should be covered, buttons should be buckled, towels should be worn around the neck if necessary, and aprons should be worn when sitting and welding for a long time. When welding at high altitude or multi-layers, a baffle should be set below the weldment to prevent liquid metal and slag from splashing when falling and expand the damaged surface. V. Prevention of welding fume and toxic gas poisoning 1. Harm of metal dust A large amount of metal dust will be produced in the welding process, which is called welding dust. Metal dust first comes from the evaporation of metal elements during welding. The high temperature of welding arc is often higher than the boiling point of metal, and many metal elements evaporate and float in the state of metal vapor, and then condense and oxidize to form metal dust with different particle sizes. The diameter of welding metal dust is usually below 65438 0 micron, which is easy to be inhaled into the lungs and cause lesions. According to field investigation and experiment, the composition and concentration of welding metal dust mainly depend on welding method, welding material and welding specification. When manual arc welding adopts iron powder covered electrode welding, the dust emission is the highest, and the greater the welding current intensity, the higher the dust concentration. Different components of welding smoke have different hazards to human body. The main elements of dust produced by black metallic paint covered electrode are iron, silicon and manganese, among which manganese is the most toxic. Long-term exposure to welding dust can cause occupational diseases such as welder's pneumoconiosis, manganese poisoning, metal fever, etc. under the condition of high welding dust concentration and no corresponding dust removal measures. (1) Welder's pneumoconiosis is caused by long-term inhalation of excessive dust, which causes diffuse fibrosis in lung tissue. In the air around the welding area, besides a lot of welding metal dust, there are many toxic substances that are irritating and promote pulmonary fibrosis, such as metal oxides such as silicon, silicate, manganese, chromium and fluoride. In addition, there are mixed dust and toxic gases such as ozone and nitrogen oxides, which can promote the formation of pneumoconiosis. Welder's pneumoconiosis is the result of long-term and chronic comprehensive action of these harmful factors. The incidence of pneumoconiosis is generally slow, mostly after exposure to smoke and dust 10 years. The main symptoms are shortness of breath, cough and expectoration, chest tightness and chest pain. Some X-ray chest films have fibrous shadows, which also affect lung function. (2) Manganese poisoning Manganese poisoning is mainly caused by manganese compounds. Manganese vapor can be rapidly oxidized into gray manganous oxide and brownish red manganous oxide smoke in the air. Manganese oxide and manganese powder enter the human body through respiratory tract and digestive tract, which can cause neurasthenia and neurological dysfunction. The process of manganese poisoning is slow, and it usually takes five years or even as long as 20 years to get sick gradually. (3) Iron oxide, manganese oxide particles and fluoride in the metal dust of welder's metal hot welding can cause welder's metal thermal reaction. In manual arc welding, alkaline covered electrode is more likely to produce metallic thermal reaction than acidic covered electrode. Its typical symptoms are chills after work, followed by fever, fatigue, metallic taste in the mouth, itchy throat, dyspnea, chest pain, loss of appetite and nausea. According to the investigation, welders using alkaline covered electrode weld in closed tanks and cabins. When ventilation measures are not appropriate, the occurrence rate of metal thermal reaction is very high. 2. Harm of Toxic Gases Under the action of high temperature and strong ultraviolet rays of welding arc, various harmful gases are formed around the arc area, including ozone, nitrogen oxides, carbon monoxide and hydrogen fluoride. (1) Ozone Under the irradiation of short-wave ultraviolet rays, oxygen in the air undergoes photochemical reaction to generate ozone (O3). Ozone is a light blue gas with a pungent smell. When the concentration is high, it smells fishy; When the concentration is higher, the fishy smell is slightly sour. Its harm to human body is mainly that it has a strong stimulating effect on respiratory tract and lungs. When the ozone concentration exceeds a certain limit, it often causes cough, dry throat, dry tongue, chest tightness, loss of appetite, fatigue, dizziness, nausea and general pain. In severe cases, especially when welding in a closed container is poorly ventilated, it can also cause bronchitis. According to measurement, the ozone concentration in welding environment is related to welding method, welding material, shielding gas and welding specification. See table 10-3 for the average ozone concentration at the distance of arc 150 mm by different welding methods. According to the results of field investigation in China, the hygienic standard of ozone concentration is 0.3 mg/m3. (2) Nitrogen oxides in the process of nitrogen oxide welding are formed by the dissociation and recombination of nitrogen and oxygen molecules in the air due to the high temperature of the arc. Nitrogen oxides are also irritating and toxic gases, but their toxicity is less than ozone. Nitrogen oxides are mainly irritating to the lungs. The factors affecting the concentration of nitrogen oxides are similar to ozone. In argon arc welding and plasma arc welding, if ventilation measures are not taken, the concentration of nitrogen oxides often exceeds the hygienic standard by ten times or even dozens of times. The hygienic standard of nitrogen oxides (converted into = nitrogen oxides) in China is 5 mg/m3. In the welding process, the possibility of nitrogen oxides alone is very small, usually ozone and nitrogen oxides exist at the same time, so the toxicity is greater. Generally speaking, the harmful effect of the simultaneous action of two toxic gases is 15-20 times that of a single toxic gas. (3) carbon monoxide carbon monoxide is formed by the decomposition of carbon dioxide gas under the high temperature of arc. All kinds of open arc welding will produce carbon monoxide gas, and the concentration of carbon dioxide shielded welding is the highest. According to the measurement, the concentration of carbon monoxide near the welder's mask can reach 300 mg/m3, which is more than ten times the hygienic standard. The concentration of carbon monoxide produced by plasma arc welding is also quite high, so special attention should be paid to working in an environment with poor ventilation. There is about 1% carbon monoxide in the flue gas of manual arc welding, and the concentration can reach 15 mg/m3 in a closed container with poor ventilation. China's health standard stipulates that the concentration of carbon monoxide is 30 mg/m3. Carbon monoxide is a kind of asphyxiating gas, and its toxic effect on human body is to hinder the transport of oxygen in the body or the function of tissue to absorb oxygen, resulting in tissue hypoxia and a series of symptoms and signs of hypoxia. Acute carbon monoxide poisoning is characterized by headache, dizziness, nausea, vomiting, general weakness, leg weakness and even fainting. If you leave the scene immediately and breathe fresh air, the symptoms can disappear quickly. In severe cases, in addition to the above symptoms, the pulse increases rapidly, and it is unable to move, entering a coma, and even complicated with symptoms such as brain edema, pulmonary edema, myocardial damage and arrhythmia. Under welding conditions, carbon monoxide mainly shows chronic effects on human body. If inhaled for a long time, symptoms of neurasthenia such as headache, dizziness, pallor, weakness of limbs, weight loss and general malaise may occur.