1 Introduction
Welding has a series of advantages such as short production cycle, low cost, flexible structure design, reasonable material and small size, so it has been widely used in industrial production. At the same time, various unsafe and unsanitary factors threaten the safety and health of welders and other production personnel.
There are many kinds of welding pollution and great harm, which has become a major environmental hazard. With the deepening of relevant research and the improvement of governance technology, welding pollution has been relatively effectively controlled. This paper starts with the formation and harm of welding pollution and proposes practical and feasible countermeasures.
2 Sources and hazards of harmful factors
Harmful factors in the welding process can be divided into metal smoke, toxic gases, high-frequency electromagnetic fields, radiation, arc radiation and noise. What kind of factors are present, mainly related to welding methods, materials to be welded and protective gases, and their severity is affected by welding specifications.
2.1 Welding fume
2.1.1 Generation of welding fume
A large amount of welding fumes are generated during the welding process. It includes smoke and dust. Particles having a diameter of less than 0.1 μm are referred to as smoke, and particles having a diameter of between 0.1 and 10 μm are referred to as dust. The steam generated when the electrode and the base metal are melted is rapidly condensed and oxidized in the air to form welding dust of different particle sizes. It floats in the air of the working environment in the form of an aerosol.
Table 1: Boiling point elements of several metal elements Fe Mn Si Cr Ni
Boiling point °C 3235 1900 2600 2200 3150
The welding fume is first derived from the evaporation of the metal during the welding process because the temperature of the welding arc is above 3000 ° C and the arc center temperature is higher than 6000 ° C. Such a high temperature inevitably causes evaporation and oxidation of the metal element. Table 1 is the boiling point of several metal elements; the second is the metal oxide produced by the oxidation of oxygen decomposed under the action of arc high temperature and the liquid metal in the arc region. In addition to defects such as slag inclusions that may remain in the weld, they may also spread to the job site. It is mainly a mixed dust composed of iron oxide, manganese oxide, fluoride and silica.
2.1.2 Harm of welding fume
When welding ferrous materials, the main components of soot are iron, silicon and manganese. When welding other different materials, aluminum, zinc oxide, molybdenum, etc. are still present in the soot, and the most toxic is manganese. Although the toxicity of iron and silicon is not large, because the dust particles are below 5 microns, they stay in the air for a long time, and it is easy to enter the lungs through the respiratory tract to form pneumoconiosis. Iron oxide, manganese oxide particles and fluoride enter the peripheral bronchioles and alveoli through the upper respiratory tract, and then enter the body, which may cause weld metal heat.
Long-term contact with such metal fumes by welders, if poorly protected, inhaling too much smoke, will cause headaches, nausea, bronchitis, pneumonia, and even the risk of welder pneumoconiosis, metal heat and manganese poisoning.
2.2 Toxic gases
Under the action of high arc temperature and strong ultraviolet light, a variety of toxic gases can be formed around the arc area, including ozone, nitrogen oxides, carbon monoxide and hydrogen fluoride.
The composition and quantity of toxic gases are related to welding methods, welding materials, shielding gases and welding specifications. For example, in the case of argon-shielded welding of carbon steel, the amount of ozone generated by ultraviolet excitation is as high as 73 μg/min; when carbon dioxide gas shielded and welded carbon steel, the amount of ozone generated is only 7 μg/min.
Various toxic gases are inhaled into the body and will affect the health of the operator.
(1) Ozone mainly has a strong stimulating effect on the respiratory tract and lungs of the human body. When the concentration of ozone exceeds a certain limit, especially when it is welded in a closed container and the ventilation is poor, it may cause symptoms such as bronchitis, cough, and chest tightness.
(2) Nitrogen oxides have a strong stimulating effect on the lungs. Acute nitrogen oxide poisoning is a systemic disease characterized by acute respiratory damage.
(3) Carbon monoxide is a suffocating gas. The carbon monoxide inhaled through the respiratory tract causes the function of oxygen transport in the body or the function of absorbing oxygen in the body to cause the human tissue to become necrotic due to lack of oxygen.
(4) Inhalation of a higher concentration of hydrogen fluoride gas or vapor can seriously irritate the eyes, nose and respiratory mucosa, and may cause bronchitis and bone lesions.
There is a certain internal relationship between smoke and toxic gases. The weaker the arc radiation, the more soot and the lower the concentration of toxic gases. Conversely, the stronger the arc radiation, the higher the concentration of toxic gases.
2.3 Arc radiation
In the case of arc discharge, on the one hand, high heat is generated, and at the same time, arc radiation is generated. Arc radiation mainly includes visible light, infrared light and ultraviolet light. It acts on the human body and is absorbed by the tissues in the body, causing thermal, photochemical or ionization of the tissue, causing acute or chronic damage to human tissues.
Welding has a series of advantages such as short production cycle, low cost, flexible structure design, reasonable material and small size, so it has been widely used in industrial production. At the same time, various unsafe and unsanitary factors threaten the safety and health of welders and other production personnel.
There are many kinds of welding pollution and great harm, which has become a major environmental hazard. With the deepening of relevant research and the improvement of governance technology, welding pollution has been relatively effectively controlled. This paper starts with the formation and harm of welding pollution and proposes practical and feasible countermeasures.
2 Sources and hazards of harmful factors
Harmful factors in the welding process can be divided into metal smoke, toxic gases, high-frequency electromagnetic fields, radiation, arc radiation and noise. What kind of factors are present, mainly related to welding methods, materials to be welded and protective gases, and their severity is affected by welding specifications.
2.1 Welding fume
2.1.1 Generation of welding fume
A large amount of welding fumes are generated during the welding process. It includes smoke and dust. Particles having a diameter of less than 0.1 μm are referred to as smoke, and particles having a diameter of between 0.1 and 10 μm are referred to as dust. The steam generated when the electrode and the base metal are melted is rapidly condensed and oxidized in the air to form welding dust of different particle sizes. It floats in the air of the working environment in the form of an aerosol.
Table 1: Boiling point elements of several metal elements Fe Mn Si Cr Ni
Boiling point °C 3235 1900 2600 2200 3150
The welding fume is first derived from the evaporation of the metal during the welding process because the temperature of the welding arc is above 3000 ° C and the arc center temperature is higher than 6000 ° C. Such a high temperature inevitably causes evaporation and oxidation of the metal element. Table 1 is the boiling point of several metal elements; the second is the metal oxide produced by the oxidation of oxygen decomposed under the action of arc high temperature and the liquid metal in the arc region. In addition to defects such as slag inclusions that may remain in the weld, they may also spread to the job site. It is mainly a mixed dust composed of iron oxide, manganese oxide, fluoride and silica.
2.1.2 Harm of welding fume
When welding ferrous materials, the main components of soot are iron, silicon and manganese. When welding other different materials, aluminum, zinc oxide, molybdenum, etc. are still present in the soot, and the most toxic is manganese. Although the toxicity of iron and silicon is not large, because the dust particles are below 5 microns, they stay in the air for a long time, and it is easy to enter the lungs through the respiratory tract to form pneumoconiosis. Iron oxide, manganese oxide particles and fluoride enter the peripheral bronchioles and alveoli through the upper respiratory tract, and then enter the body, which may cause weld metal heat.
Long-term contact with such metal fumes by welders, if poorly protected, inhaling too much smoke, will cause headaches, nausea, bronchitis, pneumonia, and even the risk of welder pneumoconiosis, metal heat and manganese poisoning.
2.2 Toxic gases
Under the action of high arc temperature and strong ultraviolet light, a variety of toxic gases can be formed around the arc area, including ozone, nitrogen oxides, carbon monoxide and hydrogen fluoride.
The composition and quantity of toxic gases are related to welding methods, welding materials, shielding gases and welding specifications. For example, in the case of argon-shielded welding of carbon steel, the amount of ozone generated by ultraviolet excitation is as high as 73 μg/min; when carbon dioxide gas shielded and welded carbon steel, the amount of ozone generated is only 7 μg/min.
Various toxic gases are inhaled into the body and will affect the health of the operator.
(1) Ozone mainly has a strong stimulating effect on the respiratory tract and lungs of the human body. When the concentration of ozone exceeds a certain limit, especially when it is welded in a closed container and the ventilation is poor, it may cause symptoms such as bronchitis, cough, and chest tightness.
(2) Nitrogen oxides have a strong stimulating effect on the lungs. Acute nitrogen oxide poisoning is a systemic disease characterized by acute respiratory damage.
(3) Carbon monoxide is a suffocating gas. The carbon monoxide inhaled through the respiratory tract causes the function of oxygen transport in the body or the function of absorbing oxygen in the body to cause the human tissue to become necrotic due to lack of oxygen.
(4) Inhalation of a higher concentration of hydrogen fluoride gas or vapor can seriously irritate the eyes, nose and respiratory mucosa, and may cause bronchitis and bone lesions.
There is a certain internal relationship between smoke and toxic gases. The weaker the arc radiation, the more soot and the lower the concentration of toxic gases. Conversely, the stronger the arc radiation, the higher the concentration of toxic gases.
2.3 Arc radiation
In the case of arc discharge, on the one hand, high heat is generated, and at the same time, arc radiation is generated. Arc radiation mainly includes visible light, infrared light and ultraviolet light. It acts on the human body and is absorbed by the tissues in the body, causing thermal, photochemical or ionization of the tissue, causing acute or chronic damage to human tissues.
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