RU2518211C1 - Powder wire - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to surfacing by submerged arc for recovery of worn-out parts and production of protective coating at equipment operated at compression and abrasion loads at 600°C. Proposed composition contains the following substances, in wt %: steel shell - 67.0-68.0, ferrotungsten - 10.0-13.75, ferromanganese - 0.76-1.41, ferrosilicum - 0.26-1.34, ferrochromium - 3.38-5.38, ferrovanadium - 0.4-1.0, nickel - 0.1-1.0, carbon-fluoride-bearing powder of electric precipitator of aluminium production - 0.80-2.58, iron powder making the rest.

EFFECT: higher wear resistance and hardness, stable arc, improved formation of built-up metal.

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Description

The invention relates to welding consumables and can be used for submerged arc surfacing to restore worn parts and obtain a wear-resistant protective coating on parts of metallurgical equipment operating under compression and abrasive wear at temperatures of 600 ° C.

Known [1], flux-cored wire for mechanized surfacing under flux, consisting of a steel sheath and a powder mixture containing ferrochrome, ferromolybdenum, ferrovanadium, ferrosilicon, ferromanganese, graphite, sodium silicofluoride, ferro-tungsten, and iron powder in the ratio, wt.%:

Ferrochrome 6-8 Ferromolybdenum 5.5-8.0 Ferrovanadium 0.8-1.8 Ferrosilicon 0.5-2.0 Ferromanganese 0.2-1.0 Graphite 0.05-0.25 Sodium silicofluoride 1,5-3,5 Ferro-tungsten 3,5-5,0 Iron powder 3.0-14.0 Shell Rest

Significant disadvantages of this cored wire are:

- reduced mechanical properties of the weld metal, in particular wear resistance and hardness, due to increased contamination of non-metallic oxide steel, as well as the ratio of carbide-forming elements;

- poor stability of arc burning due to the lack of a sufficient amount of elements (potassium, sodium) in the charge that facilitate ionization in the arc column;

- low quality deposited metal due to pore formation associated with a high hydrogen content;

- the possibility of the formation of cold cracks in the process of multilayer surfacing due to the lack of a sufficient amount of austenite-forming elements in the composition of the charge, in particular nickel;

- the high cost of the welding process due to the use of expensive materials in significant quantities (molybdenum, and sodium silicofluoride).

Known selected as a prototype [2], a flux-cored wire consisting of a steel sheath and a powder mixture containing ferromanganese, ferrosilicon, ferrochrome, ferromolybdenum, ferrovanadium, graphite, sodium silicofluoride, ferro-tungsten, iron powder in the following ratio,%:

Ferromanganese 0.2-0.5 Ferrosilicon 1.6-2.3 Ferrochrome 5.5-8.5 Ferromolybdenum 0.6-1.5 Ferrovanadium 1-3 Graphite 0.05-0.15 Sodium silicofluoride 2.2-2.4 Ferro-tungsten 5-8.5 Iron powder 5-15 Steel sheath Rest

Significant disadvantages of this cored wire are:

- reduced mechanical properties of the deposited metal, in particular hardness and wear resistance, due to increased contamination of steel with non-metallic oxide inclusions, as well as the ratio of carbide-forming elements in the composition of the charge;

- poor stability of arc burning due to the absence of elements in the charge that facilitate ionization in the arc column (lack of potassium);

- low quality deposited metal due to pore formation associated with a high hydrogen content;

- the formation of cold cracks in the process of multilayer surfacing due to the lack of a sufficient amount of austenite-forming elements in the mixture, in particular nickel;

- the high cost of the welding process through the use of expensive materials in significant quantities (molybdenum and sodium silicofluoride).

The technical results of the invention are:

- increasing the mechanical properties of the deposited metal, in particular wear resistance and hardness, due to the reduction of steel contamination by non-metallic oxide inclusions and the effect of dispersion hardening of highly alloyed austenite during tempering;

- increasing the stability of arc burning by introducing elements that facilitate ionization in the arc column;

- improving the formation of deposited metal and the elimination of pore formation due to the introduction of fluorine-containing components and the creation of additional gas protection;

- preventing the formation of cold cracks in the process of multilayer deposition by increasing the amount of stabilized austenite in the deposition process and reducing the hydrogen content in the deposited metal;

- reducing the cost of the welding process by optimizing the composition of the charge and the efficient use of production waste.

For this purpose, a flux-cored wire is proposed, consisting of a steel shell and a powder mixture containing ferro-tungsten, ferromanganese, ferrosilicon, ferrochrome, ferrovanadium, an iron powder, in which the steel shell is made of 08YuA steel, and the powder mixture additionally contains nickel and carbon-containing dust from aluminum electrostatic precipitators the ratio of components, wt.%:

Steel sheath 67.0-68.0 Ferro-tungsten 10.0-13.75 Ferromanganese 0.76-1.41 Ferrosilicon 0.26-1.34 Ferrochrome 3.38-5.38 Ferrovanadium 0.4-1.0 Nickel 0.1-1.0 Carbon fluoride dust of electrostatic precipitators aluminum production 0.80-2.58 Iron powder Rest

The claimed limits are selected empirically, based on the quality of the metal obtained during surfacing, the stability of the welding process, preventing the formation of cold cracks and the required mechanical properties.

The steel sheath of the inventive flux-cored wire was made of cold-rolled steel strip 08YuA, which made it possible to reduce the oxygen content and, accordingly, reduce the concentration of oxide non-metallic inclusions in the deposited metal compared to steel 08kp used previously.

Nickel and carbon-fluorine-containing dust of aluminum electrostatic precipitators are additionally introduced into the composition of the powdered charge, based on the following premises.

The introduction of a strong austenite-forming element, nickel, into the composition of the deposited metal increases the amount of residual austenite, which reduces the likelihood of the formation of cold cracks due to an increase in the amount of residual austenite and a decrease in the volumetric effect of martensitic transformation.

Introduction to the composition of a flux-cored powder wire charge of aluminum electrostatic precipitators is associated with the content of the latter elements, allowing:

- carry out the removal of hydrogen due to a complex of fluorine-containing compounds (such as Na ₃ AlF ₆ , Na ₂ SiF ₆ , NaF, KF, CF (1≥x≥0), AlF ₃ ), decomposing at temperatures of welding processes with the release of F, which in its the turn interacts with hydrogen dissolved in steel to form a gaseous HF compound. Reducing the hydrogen content in the weld metal reduces the likelihood of pores and cold cracks in the weld metal;

- increase the stability of arc burning due to elements that facilitate ionization in the arc column - potassium and sodium;

- carry out intensive carburization during the interaction of carbon fluoride CF _x (1≥x> 0) with carbide-forming elements, which allows to increase the amount of carbide component in the structure of the deposited metal and to further increase its hardness.

For the manufacture of a mixture of flux-cored wire used carbon-fluoride dust of aluminum electrostatic precipitators with the following chemical composition, wt.%: Al ₂ O ₃ = 18-48; F ⁺ = 18-27; Na ₂ O = 3-16; K ₂ O = 0.4-6%, CaO = 0.6-1.9; SiO ₂ = 0.5-2.4; Fe ₂ O ₃ = 1.7-3.3; C _total = 12-31, MnO = 0.05-1.3, MgO = 0.06-0.9, S = 0.09-0.4, P = 0.1-0.15.

The change in the content of nickel and carbon-containing dust of aluminum electrostatic precipitators as part of the inventive charge was made taking into account the production of high-quality deposited metal (stable arc burning, good formation, dense deposited metal without cracks, pores and non-metallic inclusions), while taking into account the content of other components.

In the manufacture of cored wire used: FV 80 (a) GOST 17293-93 ferro-tungsten powders, FS 75 grade ferrosilicon according to GOST1415-93, FMN 78 (A) carbon ferromanganese according to GOST 4755-91, ФХ900А high-carbon ferrochrome according to GOST 4757-91, ferrovanadium grade ФВ50У0.6 in accordance with GOST 27130-94, nickel grade ПНК-2К9 in accordance with GOST 9722-97, iron grade ПЖВ 1 in accordance with GOST 9849-86.

The mixture was mixed in mixers to obtain a homogeneous mass and calcined to remove moisture at a temperature of 250-350 ° C. Then, flux-cored wire was made on the machine. The diameter of the finished wire after drawing operations was 3.6 mm, with a fill factor of 0.32-0.33. The flux-cored wire with the proposed charge was used for surfacing of work roll blanks with a working part diameter of 150 mm and a length of 425 mm. Surfacing was carried out under flux in the following modes: welding current 380-400 A, arc voltage 32-34 V, surfacing speed 25 m / h, cored wire feed speed 73 m / h.

The presence of cracks in the surfacing process was visually assessed; after surfacing, the presence of cracks, pores and non-metallic inclusions was evaluated by ultrasonic and magnetic particle methods, as well as on metallographic sections. The hydrogen content in the deposited metal was determined by reductive melting in vacuum or in an inert carrier gas stream using a LECO TS-600 gas analyzer (USA). Hydrogen content was varied in the range 0.2-0.6 cm ^3/100 g of weld metal with an acceptable hydrogen content in the high alloy weld metal to 2 cm ³ / 100g metal. The hardness of the deposited metal was monitored immediately after surfacing. The hardness of the deposited metal after surfacing was HRC 48-54. Defects (cracks, pores, and non-metallic inclusions) during surfacing with flux-cored wire with a batch of the claimed composition containing nickel and dust from aluminum electrostatic precipitators were not detected.

Investigated 6 options for the composition of the charge (table 1) cored wire with foreign and boundary of the claimed limits.

The effect of changes in the chemical composition on the technological properties and mechanical characteristics of the weld metal is shown in table 2. Using the inventive composition of the flux-cored wire charge in comparison with the base composition (prototype) allows you to:

1. To improve the quality of the deposited metal by reducing its contamination with non-metallic inclusions, reducing the likelihood of pore formation and preventing the formation of cold cracks.

2. Reduce the hydrogen content by the introduction of fluorine-containing components and create an extra gas protection in the average of 0.3-0.6 cm ³ / 100g metal.

3. To improve the formation of the weld during welding by stabilizing the burning of the arc.

4. Increase the hardness of the weld metal to HRC 48-54.

5. To reduce the cost of manufacturing flux-cored wire by reducing the content of alloying components and the use of aluminum waste in the proposed flux-cored wire.

List of sources

1. A.S. USSR No. 449790, class B23K 35/30, B23K 35/30.

2. A.S. USSR No. 287830, class B23K 35/30, B23K 35/04.

Table 1  The composition of the charge The composition of the mixture, wt.%: one 2 3 four 5 6 Steel sheath 67.0 67.0 67.0 68.0 68.0 68.0 Ferro-tungsten 9.9 10.0 12.8 13,4 13.75 13.76 Ferromanganese 0.75 0.76 1,1 1.38 1.41 1.42 Ferrosilicon 0.25 0.26 0.38 1.17 1.34 1.35 Ferrochrome 3.37 3.38 4.2 5.34 5.38 5.39 Ferrovanadium 0.39 0.4 0.8 0.96 1,0 1,1 Nickel 0.09 0.1 0.31 0.45 1,0 1,1 Carbon fluorine-containing dust of aluminum electrostatic precipitators 0.79 0.80 0.96 2.44 2,58 2.59 Iron powder 17.46 16.3 12.45 6.86 5.54 5.29

table 2 Characteristics of the studied parameters depending on the composition of the charge The composition of the mixture, wt.% one 2 3 four 5 6 The hydrogen content [H], ^cm3 / 100g metal 1.3-1.5 0.3-0.6 0.3-0.6 0.2-0.5 0.2-0.5 1.2-1.6 Cracks in the weld metal Single Are absent Are absent Are absent Are absent Single Hardness of weld metal, HRC 48-50 48-54 48-54 48-54 48-54 50-54 Maximum line length of oxide non-metallic inclusions, mm 1.8 0.5 0.7 0.4 0.7 2.1

Claims (1)

A flux-cored wire consisting of a steel shell and a powder mixture containing ferro-tungsten, ferromanganese, ferrosilicon, ferrochrome, ferrovanadium, and iron powder, characterized in that the steel sheath is made of 08YuA steel, and the powder mixture additionally contains nickel and carbon-fluoride dust from the following aluminum electrostatic precipitators the ratio of components, wt.%:
steel sheath 67.0-68.0 ferro-tungsten 10.0-13.75 ferromanganese 0.76-1.41 ferrosilicon 0.26-1.34 ferrochrome 3.38-5.38 ferrovanadium 0.4-1.0 nickel 0.1-1.0 carbon fluoride dust of electrostatic precipitators aluminum production 0.80-2.58 iron powder rest