RU2084322C1 - Flux-cored electrode for arc welding - Google Patents

Abstract

FIELD: mechanical engineering; welding of carbon and low-alloyed steel structures with yield point up to 490 MPa; mechanized welding of structures when erecting earthquakeproof buildings, offshore oil production platforms, cement plants and gas and oil pipelines. SUBSTANCE: charge of flux-cored electrode contains, mas.-%: fluorspar concentrate, 4-12; calcium or magnesium carbonate, 5-12; powder nickel, 2-5; powder aluminium, 5-10; powder aluminomagnesium, 4-14; metal manganese, 2-4; sintered mixture of barium fluoride and powder ferrum, 2-4, ratio 2:1. Use of such components made it possible to stabilize strength properties of welded-on metal, increase quality of weld and reduce labour input in manufacture of flux -cored electrodes by increasing specific weight and friability of charge. EFFECT: enlarged operating capabilities, possibility of welding in any spatial position, even using downward welding method, with provision of high strength characteristics of weld. 2 tbl

Description

 The invention relates to welding materials, and more specifically to a cored wire for arc welding.

 The invention with the greatest success can be used for mechanized welding in construction during the construction of reservoir tanks, offshore platforms, earthquake-resistant buildings, blast furnaces, cement plants and gas and oil pipelines. In addition, the invention can find application in the manufacture of technological equipment and various metal structures from carbon and low alloy steel with a yield strength of up to 490 MPa.

 Known for high-performance flux-cored wires (Pokhodnya I.K. et al. Prospects for the application of self-shielding flux-cored wire in shipbuilding // Sudostroenie, 1987, N 5, pp. 24-26), which allow to obtain high-quality metal in a wide range of welding modes. However, these wires do not allow welding of joints in all spatial positions by a top-down method.

 A known composition of cored wire for arc welding (US patent N 4571480, CL B 23 K 35/36, 1986). A wire of this composition provides welding in all spatial positions, but has low strength properties, namely, the yield strength and tensile strength of the directional metal.

The main mechanical characteristics of the weld metal of a known cored wire are in the following ranges: impact strength at -30 ^o C 8-142 J; yield strength -397-473 MPa; tensile strength - 504-586 MPa; elongation of 17-35%
A disadvantage of the known self-shielding flux-cored wire is also a small fill factor (the ratio of the mass of the charge of the wire to the mass of the tape) and, as a result, a large spread in the values of the mechanical properties of the weld metal.

 The present invention is based on the task of creating a self-shielding flux-cored wire for welding in all spatial positions by a top-down method with high strength properties of the deposited metal. At the same time, the wire charge should have an increased bulk density, providing a high and stable filling factor.

 The problem is solved by a flux-cored wire for the arc welding of steels, consisting of a low-carbon steel shell and a powder mixture containing barium fluoride, calcium or magnesium carbonates, aluminum-magnesium alloy, nickel, manganese, aluminum, iron powder, in which the mixture additionally contains fluor-spar concentrate, and fluoride barium and iron powder contains in the form of a sintered mixture with the following ratios of components, wt.

Fluorspar concentrate 4.0-12.0
Carbonate 5.0-12.0
Aluminum powder 5.0-10.0
Magnesium-aluminum powder 4.0-14.0
Manganese metal 2.0-4.0
Sintered mixture of barium fluoride with iron powder
The presence of a sintered mixture of barium fluoride with iron powder made by a special technology in the charge of the self-shielding flux-cored wire stabilized the bulk density of the charge, increased the fill factor of the wire, and, as a result, increased and stabilized the strength properties of the deposited metal.

 The introduction of fluorspar concentrate into the wire mixture optimized the physicochemical properties of the slag phase of the flux-cored wire, which made it possible to perform top-down welding. The use of barium fluoride as the main component in the composition of a flux-cored wire charge is widespread in the developed foreign countries of the USA, Japan, and England. This is due to the fact that barium fluoride gives special positive properties to the slag system of welding materials and allows to obtain welds that are smooth with a metallic sheen in various spatial positions.

 Industrial technology for the production of pure barium fluoride according to GOST 7168-80 determines its receipt in finely dispersed form. The use of such barium fluoride in a flux-cored wire mixture sharply reduces the flowability and bulk density of the mixture, making it difficult to obtain a high and stable fill factor.

The sintering of finely dispersed barium fluoride with iron powder in a ratio of 2: 1 and the use of the mixture after crushing and sifting make it possible to increase the bulk density of the charge by an order of magnitude. The use of sintered mixture allows to achieve a high fill factor of flux-cored wire made of steel tape 0.4-0.5 mm thick and a diameter of 1.6 ^o C2.0 mm, the problem of increasing the fill factor and improving the protective properties of self-shielding flux-cored wires of small diameter is solved. In the course of experiments, it was found that a decrease in the content of fluoride-spar concentrate in the charge of the wire is less than 4 wt. little effect on the properties of the slag phase and worsens the formation of the weld during welding method "top-down". The excess of 12 wt. reduces stability of arc burning. The optimal carbonate content was found in the range of 5.0-12.0 wt. A change in this content leads to a decrease in the protective properties of the charge or to increased spraying of molten metal during the welding process. The nickel content is optimal in the range of 2.0-5.0 wt. A change in these values leads to a decrease in the toughness of the deposited metal at a negative temperature. The decrease in the content of the mixture of aluminum powder of less than 4.0 wt. violates the protective properties of the mixture, and an excess of more than 14.0 wt. increases spraying of molten metal. Aluminum powder should be in the range of 5-10 wt. A change in these values leads to a decrease in the toughness of the deposited metal. The decrease in the charge of metallic manganese below 2.0 wt. reduces strength, and an excess of 4.0 wt. reduces the yield strength of the weld metal. The optimum content of a sintered mixture of barium fluoride with iron powder was found in the range of 43-70 wt.

 Specific examples of cored wire compositions for arc welding are summarized in table. one.

 To determine the mechanical properties of the weld metal and the fill factor of the charge options flux cored wire specified in the table. 1, the components in accordance with the recipe after grinding and sieving were subjected to heat treatment in order to remove moisture. Then the mixture of experimental samples of flux-cored wire was weighed on an electronic balance with a weighing limit of 500 g (with an accuracy of 0.1 g). Mixing was carried out in a kubelny mixer for 45 minutes. For the manufacture of wires used steel tape brand Sv.08sp size 0.5 x 12 mm. The wire was made with a diameter of 2.0 mm on a six-drum drawing mill.

To control the fill factor from each experimental sample, the wires were cut one sample at least 100 mm long. The fill factor of the wire was determined according to the method specified in GOST 2.62,7.1.-84. To determine the mechanical properties of the experimental samples of flux-cored wires, butt joints were welded from plates measuring 210 x 320 mm in accordance with GOST 2.62.7.1.-84 with an automatic welding machine A-765. Wire feed speed 169 m / h, reach 15–20 mm, I _st 200–250 A, U _g 20–22 B. For tensile tests, type II specimens were prepared from butt welded joints, and six specimens were tested for impact strength like Charpy. Type II samples were tested on a tensile testing machine with a force of 50 tons. The type of sample "Charpy" was tested at +20 ^o C, the rest at a temperature of -30 ^o C. The test results are presented in table. 2.

 The welding and technological properties of the experimental versions of the wire were checked on pipes with a diameter of 600 mm and a wall thickness of 12 mm. Tests have shown that the most optimal wire compositions are options 2 and 5. Thus, a flux-cored wire with the specified composition of the charge provides high-speed top-down welding and increased strength and stability of the deposited metal values.

Claims (1)

 A flux-cored wire for arc welding of steels, consisting of a low-carbon steel sheath and a powder mixture containing barium fluoride, iron powder, calcium or magnesium carbonate, aluminum-magnesium alloy, aluminum, nickel, manganese, characterized in that the mixture additionally contains fluor-spar concentrate, and barium fluoride and iron powder is introduced in the form of a sintered mixture in a ratio of 2 1 in the following components, wt. Fluorspar concentrate 4.0 12.0
Calcium or Magnesium Carbonate 5.0 12.0
Nickel 2.0 5.0
Aluminum Magnesium Ligature 4.0 14.0
Aluminum 5.0 10.0
Manganese 2.0 4.0
Sintered Barium Fluoride Mixture with Iron Powder
the fill factor of the cored wire is 24 26%

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