RU2274535C2 - Powder wire composition - Google Patents

Abstract

FIELD: welding processes and equipment, namely materials for gas-shield powered welding of ship building structures of low carbon and low alloy steels operating in low-temperature climate.

SUBSTANCE: in order to provide high-quality welding with improved strength properties in all spatial positions and to enhance strength and stability of welded-on metal, wire composition includes components at next relation of ingredients, mass %: rutile concentrate, 4.8 - 8.4; feldspar, 0.8 - 1.4; synthetic corundum, 0.4 - 0.7; sodium silicofluoride; ferrosilicon, 0.2 - 0.5; ferromanganese, 1.0 - 2.7; magnesium, 0.4 0.7; iron powder, 3.0 - 5.5; sheath steel, the balance. Magnesium and rutile concentrate are added to charge at relation 1 : 12; synthetic corundum and feldspar are added at relation 1 : 2.

EFFECT: improved strength and stability of welded-on metal, high strength properties of welded structures.

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Description

The invention relates to welding production, and in particular to materials for mechanized welding in a protective gas environment of shipbuilding structures made of low-carbon and low alloy steels operating in conditions of negative climatic temperatures.

Known composition [A.S. USSR No. 927461, dated 05.15.82, bull. No. 18] cored wire for welding low alloy steels in a carbon dioxide environment, consisting of a low carbon steel shell and a powder mixture containing the following components, wt.%:

Rutile concentrate 20.0-53.0 Ferromanganese 10.0-22.8 Ferrosilicon 1.3-6.0 Sodium silicofluoride 1.0-5.0 Magnesite 1.3-10.0 Electrocorundum 1.6-7.5 Iron powder Rest

Furthermore, the fill factor is 17%.

This composition of cored wire due to the lack of ionizing elements and a sufficient number of deoxidizers does not provide high welding and technological properties and the guaranteed absence of defects in the weld.

Also known is the closest in ingredients and technical result to the claimed composition of cored wire for welding in protective gases [RF Patent No. 2164419, publ. 05/10/2001] containing a shell of low carbon steel and a powder mixture in the following ratio of wire components, wt.%:

Rutile concentrate 4.35-8.35 Feldspar 0.50-1.50 Electrocorundum 0.25-0.65 Sodium silicofluoride 0.20-0.50 Ferrosilicon 0.30-0.70 Ferromanganese 1.45-3.45 Iron powder 3.65-5.65 Potassium silicate block 0.15-0.45 Integrated Ligature 0.35-0.75 Mild steel shell Rest

Moreover, the shell contains carbon in an amount of not more than 0.06 wt.%, And sulfur and phosphorus - each not more than 0.015 wt.%. In addition, the complex master alloy charge may contain components in the following ratio, wt.%:

Boron 0,055-0,085 Magnesium 2.8-3.6 Aluminum 1.2-1.8 Lithium 0.026-0.038 Iron Rest

Such a composition of flux-cored wire for welding structures of low-alloyed shipbuilding steels in comparison with the previous analogue can significantly improve the welding and technological properties of flux-cored wire.

However, the presence of a prototype of boron and aluminum in the complex ligature often leads to a decrease in the ductility of the weld metal, and the use of hygroscopic materials such as potassium silicate block promotes defects.

The technical task of the invention is to increase the efficiency of the welded joint of the structure due to the guaranteed cold resistance of the weld metal at negative temperatures, with a relative elongation of at least 22%, as well as improving the quality of the weld due to the lack of flakiness of the surface of the weld metal during welding in all spatial positions, the minimum spraying, ensuring the smoothness of the border of its transition to the base metal.

The technical result is achieved by the fact that in the composition of the flux-cored wire containing a shell of low-carbon steel and a powdery mixture, including rutile concentrate, feldspar, electrocorundum, sodium silicofluoride, ferromanganese, ferrosilicon, magnesium, iron powder, according to the invention, in the composition of the mixture, the ratio of magnesium to rutile concentrate is maintained in a proportion of 1:12, and fused alumina to feldspar - 1: 2 in the following ratio of components, wt.%:

Rutile concentrate 4.8-8.4 Feldspar 0.8-1.4 Electrocorundum 0.4-0.7 Sodium silicofluoride 0.2-0.5 Ferrosilicon 0.2-0.6 Ferromanganese 1.0-2.7 Magnesium 0.4-0.7 Iron powder 3.0-5.5 Steel shell Rest

An additional introduction of magnesium flux-cored wire in amounts of 0.4-0.7 wt.% And a proportion to rutile concentrate in the ratio of 1:12 reduces the likelihood of defects in the weld due to the high deoxidizing ability of magnesium, and magnesium oxide forms with rutile complex compound passing into slag. This provides an improvement in the surface quality of the weld metal by reducing its scaly and creates a smooth conjugation of the boundary of the transition of the weld metal to the base metal. In addition, improving the quality of the welded joint allows you to get a guaranteed toughness of the latter at low temperatures due to the high purity of the welded metal from non-metallic inclusions. This leads to increased efficiency and reliability of the welded joint in comparison with the prototype.

A decrease in the amount of this component less than 0.4 wt.% Or a change in the proportion of its introduction compared to rutile concentrate will lead to an increase in the amount of non-metallic inclusions in the weld metal and an increase in the complexity of slag removal. An increase in its amount of more than 0.7 wt.% Will lead to a violation of the quality of the surface of the weld metal, excessive slagging.

The presence in the charge of rutile concentrate in the range of 4.8-8.4 wt.%, Feldspar in the range of 0.8-1.4 wt.% And electrocorundum in the range of 0.4-0.7 wt.%, Subject to the proportion of electrocorundum to feldspar 1: 2 provides easy separation of the slag from the surface of the weld, high stability of the arc during welding and full coverage of the weld with slag.

A decrease in the content of these components or a change in the proportions less than the specified lower limits will lead to a violation of the stability of arc burning and an increase in spatter of the electrode metal. An increase in the content of these components or a change in the proportions of more than the specified upper limits will lead to a deterioration in the formation of weld metal, the separability of the slag crust.

The presence of sodium silicofluoride in the mixture in amounts of 0.2-0.5 wt.% Improves the formation of the weld and its gas protection, contributes to the purification of the metal, which ensures the required level of toughness of the weld metal at low temperatures. With a decrease in the content of this component in the charge of less than 0.2 wt.%, The likelihood of pores in the weld metal increases, leading to a decrease in the strength of the welded joint, and an increase in the content of more than 0.5 wt.

The content of ferromanganese is optimal in the range of 1.0-2.7 wt.% And ferrosilicon in the range of 0.2-0.6 wt.%, The values of these values are taken from the calculation of ensuring high mechanical properties of the weld metal with a temporary resistance of at least 500 MPa and providing an elongation of at least 22%.

A decrease in the content of these components in the charge of less than the lower limits leads to a decrease in the strength of the welded joint, and an increase in the higher limits leads to a decrease in the ductility of the weld metal.

The presence in the charge of iron powder in the optimal range of 3.0-5.5 wt.% Contributes to the improvement of welding and technological properties with high welding performance. A change in these values leads to a decrease in the uniformity of melting of the charge and shell.

The flux-cored wire of the proposed composition is made according to the following technology.

The charge materials are pre-milled, sieved through a sieve. Then the powders are thoroughly mixed and poured into a shell made of carbon steel with a diameter of 3-5.0 mm and a wall thickness of 0.5 mm. The estimated fill factor is 12-21%. Next, wire drawing is carried out to an outer diameter of (1.0-1.6) mm and calcining in a furnace at a temperature of about 250 ° C for 3-4 hours. After calcination, a row winding is carried out on Eurocassettes with a diameter of 200 mm.

Three compositions of flux-cored wire with a diameter of 1.2 mm, conventionally designated 1, 2 and 3, were made. The steel of the sheath was 79-88% of the total mass of the wire.

Specific examples of the composition of the cored wire are shown in table 1.

Table 1. No. Component Name The content of components, wt.% one 2 3 one. Rutile concentrate 4.8 6.0 8.4 2. Feldspar 0.8 1,0 1.4 3. Electrocorundum 0.4 0.5 0.7 four. Sodium silicofluoride 0.2 0.4 0.5 5. Granular magnesium 0.4 0.5 0.7 6. Ferrosilicon 0.2 0.4 0.6 7. Ferromanganese 1,0 1.9 2.7 8. Iron powder 4.2 5.3 5,4 9. Carbon steel sheath 88.0 84.00 79.5

To determine the mechanical properties of the experimental samples of flux-cored wires, plates made of steel 10KHSND with a size of 200 × 500 × 14 mm were welded. Welding was carried out semi-automatically by direct current of reverse polarity. Welding modes are presented in table 2.

Table 2. Welding position lower vertical Current, A 230 180 Voltage 27 26 CO ₂ consumption, l / min 16 16 Departure of an electrode, mm twenty twenty Welding speed, m / h 33 25

Carbon dioxide CO ₂ was used as a protective medium. With horizontal and ceiling positions, the welding speed is 20-25 m / h. The optimal content limits of the components of the flux-cored wire charge of the claimed composition were determined by the results of tests of the impact work of fracture of the metal of the welded joints of the samples at minus 20 ° С, by the observations of the welding and technological properties of the wire, the smoothness of the surface of the roller and the smooth transition of the weld to the base metal.

The test results are presented in table 3.

Table 3. Composition of cored wire Temporary tear resistance, MPa Relative extension, % Work of blow at a temperature (-20 ° C), J one 520 29th 51 2 570 27 78 3 620 23 62

As follows from table 3, the welds obtained using flux-cored wires with a carbon steel sheath and a batch made according to the invention with an average fill factor of 16 have high mechanical properties and a high impact result of fracture of the weld metal at low temperatures.

Tests have shown that the most optimal composition of the wire is composition No. 2, in which the impact work of the destruction of the weld metal at a temperature of minus 20 ° C is 51-78 J.

In addition, the welds obtained by cored wire of the claimed composition have high quality indicators, the formed surface of the weld metal is smooth, almost without scaly on it, the formation of the weld proceeds with a smooth transition from the weld metal to the base metal due to better wettability of the weld metal.

The use of the claimed composition of flux-cored wire for the manufacture of critical welded structures from shipbuilding steels operating in conditions of negative climatic temperatures allows high-quality welding in all spatial positions with high strength properties, and also provides increased strength and stability of the deposited metal.

Information sources

1. USSR author's certificate No. 927461, dated 05.15.82, bull. Number 18.

2. RF patent No. 2164419 dated 05/10/2001 - prototype.

Claims (1)

The composition of the flux-cored wire, containing a shell of low-carbon steel and a powder mixture, including rutile concentrate, feldspar, electrocorundum, sodium silicofluoride, ferromanganese, ferrosilicon, magnesium, iron powder, characterized in that magnesium and rutile concentrate are introduced into the mixture in a ratio of 1:12 and electrocorundum and feldspar in a ratio of 1: 2 with the following content of components, wt.%: Rutile concentrate 4.8-8.4 Feldspar 0.8-1.4 Electrocorundum 0.4-0.7 Sodium silicofluoride 0.2-0.5 Ferrosilicon 0.2-0.6 Ferromanganese 1.0-2.7 Magnesium 0.4-0.7 Iron powder 3.0-5.5 Steel shell  Rest