Harmful factors of welding materials – what should be considered when using them?

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China’s welding materials industry is highly market-oriented. Ordinary, low-grade electrodes and copper-coated welding wires used in this industry have a low level of technological complexity, resulting in low entry barriers; as a result, there has been severe overcapacity in these areas in recent years. As market competition intensifies, the industry is moving toward larger-scale, group-based business models. While some domestic companies are encroaching on the market by offering low prices, they are also accelerating the adjustment of their product portfolios in an effort to capture the high-end market. Next, I will introduce the harmful factors of welding materials as well as the precautions to take. Let’s take a look together. Harmful factors of welding materials (1) The main focus of occupational health research in welding is fusion welding, among which shielded arc welding presents the greatest occupational health issues, while submerged arc welding and electroslag welding have the fewest such problems. (2) The main harmful factor in processes such as flux-cored wire manual arc welding, carbon arc gouging, and CO2 gas shielded welding is the dust generated during welding – welding fumes. Especially shielded metal arc welding. Similar to carbon arc gas gouging, welding in confined spaces for extended periods of time (such as boilers, ship cabins, sealed containers, and pipes), especially in conditions with poor hygiene, can cause harm to the respiratory system; in severe cases, it may lead to welder’s pneumoconiosis. (3) Toxic gases are a major hazard factor in gas welding and plasma arc welding; high concentrations can cause poisoning symptoms. In particular, ozone and nitrogen oxides are produced by the high-temperature radiation from arcs acting on oxygen and nitrogen in the air. (4) Arc radiation is a harmful factor common to all open arc welding processes, and the electro-optic eye disease caused by it is a specific occupational disease associated with open arc welding. Arc radiation can also damage the skin, causing welders to suffer from skin conditions such as dermatitis, redness, and small blisters. Furthermore, it will also damage the cotton fibers. (5) Tungsten inert gas welding and plasma arc welding involve harmful factors in the form of high-frequency electromagnetic fields, as the welding machines are equipped with high-frequency oscillators to assist in starting the arc; this is especially true for welding machines whose high-frequency oscillators operate for long periods of time (such as some argon arc welding machines manufactured by factories). High-frequency electromagnetic fields can cause diseases of the nervous and blood systems in welders. Since thorium-tungsten rod electrodes are used and thorium is a radioactive substance, there are harmful radiation factors (alpha, beta, and gamma rays), which may pose radioactive hazards in the area where these thorium-tungsten rods are stored and in the vicinity of the grinders used for sharpening them. (6) Plasma arc welding, spraying, and cutting generate intense noise; in the absence of proper protection, this can damage the welder’s auditory nerves. (7) The main harmful factors during gas welding of non-ferrous metals are the oxide dust formed by the evaporation of molten metal into the air, and the toxic gases emitted from the welding flux. Precautions for using welding materials: 1. Stainless steel electrodes are generally available in two types: titanium-calcium type and low-hydrogen type. It is advisable to use a DC power supply for the welding current, as this helps to overcome issues such as the electrode turning red and a shallow weld depth. Welding electrodes with a titanium-calcium type coating are not suitable for welding in all positions; they are only appropriate for flat welding and groove welding ； Welding electrodes with low-hydrogen coatings can be used for all-position welding. 2. Stainless steel welding electrodes should be kept dry when in use. To prevent defects such as cracks, pits, and pores, titanium-calcium fluxes are dried at 150–250°C for 1 hour before welding, while low-hydrogen fluxes are dried at 200–300°C for 1 hour before welding. Drying cannot be repeated multiple times, otherwise the flux is likely to peel off. 3. Clean the weld area thoroughly, and also prevent the welding rod from coming into contact with oil and other contaminants, so as to avoid increasing the carbon content in the weld and affecting the quality of welding. 4. To prevent intergranular corrosion caused by heating, the welding current should not be too high; it is generally advisable to use a current level that is about 20% lower than that used with carbon steel electrodes. The arc length should also be kept short, and rapid cooling between layers is necessary, with narrow weld paths being preferred. 5. Be careful when starting the arc; do not start it at areas that are not to be welded. It is best to use an arc-starting plate made of the same material as the workpiece for starting the arc. 6. Short-arc welding should be preferred as much as possible; the arc length is generally 2-3 mm, as an excessively long arc can easily cause thermal cracks. 7. Welding technique: Short-arc rapid welding should be used; lateral movement is generally not permitted. The purpose of this is to reduce heat input and the width of the heat-affected zone, thereby enhancing the weld’s resistance to intergranular corrosion and minimizing the tendency for hot cracks. 8. When welding dissimilar steels, care should be taken in selecting the welding electrode to prevent hot cracks caused by an inappropriate choice of electrode, or the precipitation of σ-phase after high-temperature heat treatment, which can render the metal brittle. Select the electrodes in accordance with the selection criteria for welding stainless steel and dissimilar steels, and adopt appropriate welding procedures. The development strategy for welding material products in China is gradually shifting, with highly automated, high-performance products replacing manual ones. Manual welding rod products are evolving toward higher strength, greater toughness, lower hydrogen content, and improved environmental compatibility, in order to meet the various welding technical requirements associated with different types of products, welding structures, and operating conditions.