Classification of covered electrodes
At the present time in our country for welding carbon and alloy structural steels are used according to GOST 9467-60 the electrodes, which is based on the mechanical properties of weld metal or weld performed by the electrode. In addition, limited sulfur and phosphorus content in the weld metal.
Type of electrode denoted by the letter E, followed by the letter denotes the number of lower value of tensile strength. Standard provides for the types of electrodes from E34 to E145; if, after the letter of A, then it means that the electrode provides higher values of the plastic properties of weld metal and welded joint.
The electrode type E34 gives the lowest strength and low ductility of the metal and apply the electrodes coated with a thin stabilizing is permitted only in the production of less critical welded structures, E42 and E46 are suitable for critical structures made of carbon steel, E50 and E55 - for of medium-and low-alloy steels, E60 , E70, E85, E100, E125 and E145 - to high-strength alloy steels, and for the types of E85-E145 weld after weld heat treatment takes place. E34-E70 types are wire rod from St-08, E85-E145 - stainless wire.
However, the electrode of the same type, such as E42, is available with different coatings, giving the electrode significant technological features that are not marked for a visit. Consequently, there remains another brand of electrodes, installed by the manufacturer of electrodes and electrode introduced into the passport. Legend marks completely arbitrary, and the brand may vary, for example, a number of the coating with the same composition.
Based on the chemical composition of the classification of high-quality coating of electrode surfaces:
1. Rudnokislye coatings containing oxides of iron and manganese (usually in the form of ores), silica, a large number of ferro-manganese, to create a gas protection welding zone is introduced into the coating of organic material (cellulose, wood flour, starch, etc.) which are decomposed by heat and burn with a mixture of protective gases. The electrodes have a fairly high speed of melting, the deposition rate 8 - 11 g / h, and are suitable for welding in all positions on the direct and alternating current, weld metal for the type of electrodes E42 and contains less than 0.12S, less than 0,10 Si; 0 ,6-0, 9 Mn, P less than 0.05 and less than 0.05 S.
With the melting of the electrode is an intensive exothermic reaction with oxygen and carbon manganese oxides, heated molten pool and provides a smooth surface of the weld metal with a little scaly. With high content of manganese ore produced smoke is bad for the welder and the lack of ventilation may gradually poison its compounds of manganese. The electrodes are widely used in the manufacture of various products from low-carbon and low alloy steels, but at a number of the Soviet Union, the use of these electrodes is limited or prohibited because of their toxicity.
2. Rutile coatings are significant of the mineral rutile, consisting mainly of titanium dioxide, TiO2. In the cover, in addition to rutile, introduced silica, ferro-manganese, calcium or magnesium carbonates. Coatings on technological qualities are close to rudnokislym provide a better formation, less spatter and release gases, are considered less harmful to the welder. The weld metal meets the electrodes E42 and E46 type, the electrodes can be used for more important structures of low-carbon and low alloy steels.
3. Fluorine-calcium coatings are composed of calcium carbonate and magnesium, fluorspar and ferro-alloys. Coatings are also called primary, as they give short slag main character, and electrodes coated with such a well known nizkovodorodistymi as weld metal contains less hydrogen than other coatings.
Gas protection is provided by Bath dioxide and carbon monoxide formed during the decomposition of carbonates under the influence of heat. The electrodes are usually used with direct current reverse polarity (plus on the electrode).
The weld metal composition corresponds to a quiet steel, very clean, low oxygen, nitrogen and hydrogen, reduced sulfur, and phosphorus, increased - manganese (0.5-1.5%) and silicon (0.3-0.6%) . Metal is resistant to aging, has high mechanical properties, including toughness, and often superior to the mechanical properties of the base metal. Electrodes with this coating is recommended for the most important structures of carbon and alloy steels.
Electrodes with fluorine-coated calcium for many years are the best quality of weld metal. Sensitive to the presence of scale, rust, oil on the edges of the base metal and in these cases give the pores, as in the dampness of the electrodes. The properties of weld metal can be varied within wide limits by varying the amount of ferro-alloys in the coating. Widely known for this type of electrode, marked SSSI-13, and he has several varieties; UONI-13/45, UONI-13/55, etc., the second number indicates the strength of weld metal.
4. Organic coatings are composed of organic material, usually of the oxycellulose, which added slag-forming materials, titanium dioxide, silicates, etc., and ferromanganese as a deoxidizer and alloying agent. Electrodes are suitable for welding in all positions on the direct and alternating current, insensitive to the quality of assembly and of the metal surface, especially suitable for use in mounting and field conditions. Give a satisfactory weld metal corresponding to the electrodes E42-E50 types. Widely used in the U.S. assembly operations.
See also:
Classification of covered electrodes
The composition of electrode coatings
Appointment of individual coating components SSSI-13
Manufacturing Electrodes
Welding Electrodes
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