The hazard degree of argon arc welding is relatively greater than that of electrode arc welding, but it is not so large that it is daunting. The infrared radiation is about 1 to 1.5 times that of ordinary electrode arc welding, and the ultraviolet radiation generated by argon arc welding arc is about It is 5 to 20 times that of electrode arc welding.
When welding in a limited space, the concentration of ozone can increase to a dangerous level. During the welding process, harmful gases such as carbon dioxide and carbon monoxide and metal dust will also be produced, which will cause certain harm to welders.
Therefore, we must do a good job of protection during the welding process, and choose the material of the electrode, and try to use cerium tungsten with low radioactivity. When grinding electrodes, wear a mask and gloves, and wash your hands after work to minimize the hazards.
Prevent damage from high-frequency electromagnetic fields
1. Generation and harm of high-frequency electromagnetic fields
In tungsten argon arc welding and plasma arc welding and cutting, high-frequency oscillators are often used to stimulate the arc, and some AC argon arc 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 thousand cycles, the voltage is 2500-3500 volts, the high-frequency current intensity is 3-7 mA, and the electric field strength is about 140-190 volts/meter.
Long-term exposure of welders to high-frequency electromagnetic fields can cause autonomic dysfunction and neurasthenia. Symptoms include general malaise, dizziness, dreaminess, headache, memory loss, fatigue, loss of appetite, insomnia, and low blood pressure. Click to get 10G CNC programming tutorial pictures for free
The reference hygienic standard for high-frequency electromagnetic fields stipulates that the allowable radiation intensity of 8-hour exposure is 20 volts/meter.
According to measurements, the intensity of the high-frequency electromagnetic field received by each part of the welder during manual argon tungsten arc welding exceeds the standard, among which the intensity of the hand is the strongest, exceeding the hygienic standard by more than 5 times. If the high-frequency oscillator is only used for arc striking, the impact is small because of the short time, but long-term contact is also harmful, and effective protective measures must be taken.
2. Protective measures against high-frequency electromagnetic fields
⑴ For arc ignition and arc stabilization measures of argon arc welding, try to use transistor pulse device instead of high-frequency oscillation device, or only for arc ignition. After the arc is ignited, immediately cut off the high-frequency power supply.
(2) Reduce the oscillation frequency, change the capacitor and inductance parameters, reduce the oscillation frequency to 30 thousand cycles, and reduce the impact on the human body.
(3) Shielded cables and wires are made of thin copper braided flexible wires, which are placed outside the cable hose (including the wires inside the welding torch and leading to the welding machine), and grounded.
⑷Because the voltage of the high-frequency oscillation circuit is high, good and reliable insulation is required.
radioactive hazards
The thoriated tungsten used in argon arc welding contains 1% to 1.2% thorium oxide. Thorium is a radioactive element that emits alpha, beta, and gamma rays. During the welding process and the contact process with the thoriated tungsten rod, it may be affected by radiation. Through a large number of investigations, the daily consumption of thoriated tungsten rods is only 100--200mg, and the radiation dose is very small, which has little effect on the human body. However, when welding in the container, the ventilation is not smooth, and the radioactive particles in the smoke may exceed the hygienic standard;
Second, when grinding thoriated tungsten rods and the place where thoriated tungsten rods are stored, the concentration of radioactive aerosol and radioactive dust can reach or even exceed the hygienic standard. The intrusion of radioactive substances into the body can cause chronic radiation diseases and form internal exposure, which is mainly manifested in the weakening of the general functional state, obvious weakness, significantly reduced resistance to infectious diseases, and weight loss.
Baidu Encyclopedia: Radioactive aerosol, solid or liquid particles containing radionuclides suspended in air or other gases. Dispersion system formed by solid or liquid radioactive particles suspended in air or gaseous medium. The basic characteristics of aerosols are instability, particles smaller than 0.1 microns perform Brownian motion in the gas, and do not settle due to gravity; particles of 1 to 10 microns settle slowly and are suspended in the air for a long time. Radioactive aerosols have high ionization effects, low concentrations, and are easily charged on particles (produced by radioactive decay). Radioactive aerosols are the main threat to human internal exposure.
Hazards of strong arc light
Welding arc radiation mainly includes visible light, infrared rays and ultraviolet rays. They act on the human body, are absorbed by human tissue, cause thermal action, photochemical action or ionization of tissue, and cause damage to human tissue.
The luminosity of visible light is about 10,000 times greater than the normal luminosity of the naked eye. When the visible light radiates to the human eye, it will cause pain and make it hard to see. It is usually called "dazzling", and loses the ability to work in a short time .
The harm of infrared rays to the human body is mainly caused by the thermal effect of the tissue. During the welding process, the eyes are exposed to strong infrared radiation, and they will immediately feel strong burns and pains, and flash hallucinations will occur. Long-term exposure may cause infrared cataracts, vision loss, and even blindness in severe cases.
Ultraviolet radiation (UV), also known as ultraviolet radiation, refers to electromagnetic waves with a wavelength of 100-400nm. Appropriate amount of ultraviolet radiation can have a beneficial effect on the human body, but excessive exposure can cause adverse effects on the human body (such as welding ultraviolet radiation). The harm of ultraviolet rays to the human body is mainly photochemical action, which causes damage to human skin and eyes. After the skin is exposed to strong ultraviolet radiation, it can cause dermatitis, diffuse erythema, sometimes small blisters, exudate, burning sensation, and itching;
When the effect is strong, it is accompanied by systemic symptoms: headache, dizziness, fatigue, nervous excitement, fever, insomnia, etc. Excessive exposure of ultraviolet rays to human eyes can cause acute keratitis and conjunctivitis, that is, electro-optic ophthalmia. Symptoms are high eye shame, tearing, foreign body sensation, tingling, eyelid redness, spasms, accompanied by headache and blurred vision.
The hazards of welding fumes
A large amount of metal welding dust will be produced during the welding process. The metal powder produced by welding has a small diameter and is easier to inhale into the lungs. Because the diameter is small, it is difficult to excrete the body, so pathological changes occur. The greater the welding current intensity, the higher the dust concentration. In the case of high concentration of welding dust and no corresponding dust removal measures, long-term exposure to welding dust can cause occupational diseases such as welder's pneumoconiosis, manganism and metal fever.
Reproductive toxicity. In the past 10 years, some studies on the reproductive toxicity of welding work have been carried out at home and abroad, mainly involving the quality of male workers' semen, female workers' reproductive outcomes and damage mechanisms. Studies have shown that: female welders have increased menstrual flow, shortened cycle, prolonged menstrual period, increased leucorrhea, spontaneous abortion, premature delivery, and dysmenorrhea, all of which are higher than those of the control group. The appearance of the semen of manganese poisoned male workers was uniform off-white, the pH value was normal, and the average liquefaction time was longer than that of the control group.
The test results proved that the average ejaculate volume, total sperm count, sperm survival rate and motile sperm rate of male workers with manganism poisoning were all lower than those of the control group, and the abnormal sperm rate of male workers with manganism poisoning was significantly higher than that of the control group. It is believed that metal manganese can affect the spermatogenesis system of male workers, has a direct toxic effect on the development of sperm, and can kill sperm, thereby causing changes in the quality of male semen. It has also been reported abroad that the secretion of sex hormones in electric welding workers has changed, and the quality of sperm has declined, but it has no effect on the sex ratio of offspring
The hazards of harmful gases
Under the action of welding arc high temperature and strong ultraviolet rays, a variety of harmful gases are formed around the arc, mainly including ozone, nitrogen oxides, carbon monoxide and hydrogen fluoride. Ozone is an irritating poisonous gas with a light blue color. When the concentration is high, it emits a fishy smell; high concentration ozone also has a slightly sour taste.
The main hazard of ozone to the human body is that it has a strong stimulating effect on the respiratory tract and lungs. It often causes coughing, chest tightness, loss of appetite, fatigue, dizziness, general pain, etc. In severe cases, it can also cause bronchitis and pulmonary edema, etc.
Nitrogen oxides are irritating and toxic gases. Nitrogen dioxide is reddish brown and has a special odor. The harm of nitrogen oxides to the human body is mainly the stimulation of lung tissue. After it is inhaled into the respiratory tract, it gradually reacts with water in the alveoli to form nitric acid and nitrous acid, which will strongly stimulate and corrode the lung tissue, causing poisoning.
The main symptom of chronic poisoning is neurasthenia, such as insomnia, headache, loss of appetite, and weight loss. High concentrations of nitrogen oxides can cause acute poisoning. In mild poisoning, only acute bronchitis occurs; in severe poisoning, severe coughing, dyspnea, collapse, general weakness and other symptoms are caused.
The effect of nitrogen oxides on the human body is also reversible, and its adverse effects will gradually decrease or be eliminated as the time away from work increases. During argon tungsten arc welding, if ventilation measures are not taken, its concentration often exceeds the hygienic standard by more than ten times, or even dozens of times. The hygienic standard for nitrogen oxides (converted into nitrogen dioxide) stipulated in our country is 5mg/m3. During the welding process, ozone and nitrogen oxides usually exist at the same time, so they are more toxic. In general, the presence of two toxic gases at the same time is 15-20 times more harmful than a single toxic gas.
Protective measures
(1) Ventilation measures
The argon arc welding work site must have a good ventilation device to discharge harmful gases and smoke. In addition to the ventilation of the factory building, several axial flow fans can be installed in places where the welding workload is heavy and the welding machines are concentrated. In addition, local ventilation measures can also be used to remove harmful gases around the arc, such as using open arc exhaust hoods, exhaust welding torches, and small portable fans.
(2) Radiation protection measures
Use cerium tungsten electrode with extremely low radiation dose as much as possible. When processing thorium tungsten electrodes and cerium tungsten electrodes, sealed or ventilated grinding wheels should be used for grinding. Operators should wear masks, gloves and other personal protective equipment, and wash hands and faces after processing. Thoriated tungsten and cerium tungsten electrodes should be stored in aluminum boxes.
(3) Measures to protect against high frequency
In order to prevent and weaken the influence of high-frequency electromagnetic fields, the measures taken are: 1) The workpiece is well grounded, and the welding torch cable and ground wire should be shielded with metal braided wires; 2) Reduce the frequency appropriately; 3) Try not to use high-frequency oscillators as The arc stabilizing device reduces the action time of high-frequency electricity.
(4) Other personal protective measures
During argon arc welding, due to the strong effects of ozone and ultraviolet rays, it is advisable to wear non-cotton work clothes (such as acid-resistant wool, tussah silk, etc.). In the case of welding in the container and local ventilation cannot be used, personal protective measures such as air-supply helmets, air-supply masks or gas masks can be used.
