RU2313435C1 - Ceramic flux for automatic welding of low alloy steels - Google Patents

Abstract

FIELD: automatic welding of low-alloy cold-resistant steels of high and very high strength by means of low-carbon and low- alloy wires in any branch of industry.

SUBSTANCE: ceramic flux includes next relation of ingredients, mass %: roasted magnesite, 26.4 - 30.0; synthetic corundum, 18.6 - 22; fluorspar, 20.0 - 20.5; sphene concentrate, 12.2 - 14.5; synthetic titanium dioxide 98%, 5.0 - 6.5; manganese metallic, 2.0 - 3.1; ferrotitanium, 0.25 - 0.5; ferrosilicon, 0.5 - 0.8; titanium magnetite, 0.5 - 0.63; ferroboron, 0.2 - 0.4; sodium-potassium silicate, 6.55 - 8.1. Such flux allows use small cost low carbon wires instead of high cost low alloy and alloy wires for welding important structures operating at negative temperatures (40)-(-60)°C.

EFFECT: enhanced manufacturing properties at welding butt joints with deep dressing of their edges.

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Description

The present invention relates to welding materials, namely ceramic fluxes, and can be used for automatic welding of low alloy steels of high and high strength with low carbon and low alloy wires in any industry, for example, shipbuilding, for welding shipbuilding structures, in bridge building, as well as in petrochemical industry for welding products operating at low temperatures.

Known ceramic flux for automatic welding of low alloy steels with low alloy wires, containing calcined magnesite, fluorspar, electrocorundum, wollastonite, metallic manganese, sodium silicate, ferrotitanium and ferroboron in the following ratio, wt.%:

Calcined Magnesite 23.0-31.0 Fluorspar 24.0-27.0 Electrocorundum 18.0-27.0 Wollastonite 11.0-16.0 Manganese metal 0.9-1.8 Sodium silicate 8.3-9.2 Ferrotitanium 0.5-2.2 Ferroboron 0.1-0.9

the ratio of the total content of calcined magnesite, fluorspar and half wollastonite to the total content of electrocorundum, half wollastonite and two-thirds of sodium silicate is selected in the range of 1.43-2.16, and the ratio in the flux of titanium to boron is selected in the range of 4.23- 17.1 [1].

A disadvantage of the known ceramic flux is the high viscosity of the slag due to the increased content of basic oxides in the flux of relatively acidic and low thermodynamic stability of wollastonite. The high viscosity of the slag degrades the welding and technological properties of the flux (the inability to obtain the required concave shape of the weld when welding corner and tee joints). In addition, this flux can only be used when welding with low alloy wires.

Known closest in composition and technical result to the claimed ceramic flux for automatic welding of low alloy steels with low alloy wires, containing fluorspar, electrocorundum, calcined magnesite, sphene concentrate, metallic manganese, ferrotitanium, ferroboron, titanomagnetite, potassium ferrosilicon and sodium silicate ratio components, wt.%:

Fluorspar 22.0-30.0 Electrocorundum 14.0-25.0 Calcined Magnesite 22.0-31.0 Sphene Concentrate 10.0-20.0 Manganese metal 1.0-3.0 Ferrotitanium 1.2-2.8 Ferroboron 0.1-0.8 Titanomagnetite 0.4-0.9 Ferrosilicon 0.3-1.0 Sodium Potassium Silicate 7.7-8.9

the ratio of the total content of magnesite, fluorspar and one third of the sphene concentrate to the total content of two-thirds of the sphene concentrate, two-thirds of sodium potassium silicate and one second electrocorundum is selected in the range of 1.7-2.3, and the ratio of ferrotitanium to ferroboron is within 6.0-15.0 [2] is a prototype.

The well-known ceramic flux as compared to its counterpart, while maintaining the required toughness of the welded joint in the range of (-40) - (-50) ° C when welding low alloy steels with low alloy wires, has improved welding and technological properties (the ability to obtain the required concave shape of the weld when welding corner and tee joints) due to:

- reducing the viscosity of the slag by reducing the content in the flux of basic oxides relatively acidic as a result of the replacement of wollastonite with a mineral of sphene concentrate;

- increase the thermodynamic stability of sphene concentrate due to the presence of titanium dioxide in its composition.

However, due to the fact that titanium dioxide in the composition of the sphene concentrate mineral is firmly bonded in the complex compound (CaO · SiO ₂ · TiO ₂ ), the achieved thermodynamic stability is not sufficient for good separation of the slag crust when welding butt joints with deep cutting edges, which reduces welding technological properties of the flux.

In addition, due to the increased content of carbon and oxygen in the weld pool, this flux cannot provide the necessary impact strength of welded joints in the range of (-40) - (-60) ° С when welding with low-cost low-carbon wires and is intended for welding only with more expensive low-alloy ones and complex alloyed wires, which is not optimal for economic reasons.

The disadvantages of the known ceramic flux (prototype) include the following:

- the inability to provide the necessary toughness of welded joints of low alloy steels in the range of (-40) - (- 60) ° C when welding them with low-carbon wires;

- difficult separation of the slag crust when welding butt joints with deep cutting edges.

The technical result of the invention is to provide the necessary impact strength of welded joints of low alloy steels in the range of (-40) - (- 60) ° C when welding them with low-cost low-carbon wires and increase the welding and technological properties of the flux by improving the separation of the slag crust when welding butt joints with deep cutting edges.

The technical result is achieved in that the ceramic flux for automatic welding of low alloy steels, containing calcined magnesite, electrocorundum, fluorspar, sphene concentrate, metallic manganese, ferrotitanium, ferrosilicon, titanomagnetite, ferroboron and a binder additive, sodium potassium silicate, additionally contains 98% synthetic titanium dioxide in the following ratio of components, wt.%:

Calcined Magnesite 26.4-30.0 Electrocorundum 18.6-22.0 Fluorspar 20.0-20.5 Sphene Concentrate 12.2-14.5 Synthetic Titanium Dioxide 98% 5.0-6.5 Manganese metal 2.0-3.1 Ferrotitanium 0.25-0.5 Ferrosilicon 0.5-0.8 Titanomagnetite 0.5-0.63 Ferroboron 0.2-0.37 Sodium Potassium Silicate 6.55-8.1

the ratio of the total content, calcined magnesite, fluorspar and 1/3 of the sphene concentrate to the total content of 2/3 of the sphene concentrate, 2/3 of sodium potassium silicate, 1/2 of electrocorundum and 1/2 of titanium dioxide is selected within 1.8 -2.1, the ratio of ferrotitanium to ferroboron is in the range of 0.67-2.5, and the ratio of synthetic titanium dioxide to fluorspar is selected in the range of 0.24-0.32.

Introduction to the proposed ceramic flux of unbound synthetic titanium dioxide with increased thermodynamic stability is an effective tool to reduce the carbon and oxygen content in the molten metal of the weld pool and increase the amount of reduced titanium, because with increasing temperature during the welding process, carbon actively interacts with oxygen, turning into a gaseous state - carbon monoxide, and titanium is reduced. The interaction of titanium dioxide with carbon in the process of melting occurs by the reaction of TiO ₂ + 2C = 2CO ↑ + Ti. Moreover, the oxidation of 0.05% carbon leads to the restoration of 0.1% titanium [3].

As a result, the structure of the weld metal and its visco-plastic properties are improved, which significantly increases its mechanical properties at low temperatures, providing the necessary impact strength of welded joints of low alloy steels in the range of - (- 40) - (- 60) ° С when welding them with low carbon wires.

The presence of synthetic titanium dioxide with increased thermodynamic stability in an unbound (unlike the prototype) state reduces the redox reactions between molten flux slag and the metal. This is due to the fact that titanium dioxide lowers the viscosity of slag due to the substitution of silica in the flux [3]. In addition, being a catalyst, titanium dioxide intensifies the action of fluorspar, which dilutes the main slags [4, 5].

As a result, when welding in the process of melting the electrode wire and the base metal from the flux protecting the weld pool from air, a non-metallic liquid phase is formed - slag with a reduced density compared to the density of the molten metal.

In this regard, there is an easier floating of slag into the upper part of the weld pool, which carries away harmful compounds and gases. Upon cooling, the metal crystallizes, and the liquid slag turns into a crust and is easily separated from the weld metal [5].

Thus, the introduction of unbound titanium dioxide improves the separation of the slag crust when welding butt joints with deep grooving due to a decrease in the density of the slag compared to the density of the molten metal and a decrease in the adhesion of the slag to the metal due to the increased thermodynamic stability of titanium dioxide.

The indicated limits of the ratios of the total content of components in the composition of the proposed flux make it possible to adjust the optimum ratio of acid and basic oxides in it, as well as the content of carbon, oxygen and reduced titanium in the weld metal, which together with microalloying additives increases its impact strength at negative temperatures in the range ( -40) - (- 60) ° С when welding low-alloy steels with inexpensive low-carbon wires.

An additional unbonded synthetic titanium dioxide, which has increased thermodynamic stability, is added to the flux, together with electrocorundum and sphene concentrate, can significantly improve the separation of the slag crust when welding butt joints with deep cutting edges.

All compositions of the proposed flux were made on a semi-automated line according to the following technology. The components, ground to 0.3 mm, were dosed strictly according to the given recipe in the cube and transported to the granulator-mixer. The mixing of the ingredients was carried out in two stages: dry and wet (with a liquid solution of sodium potassium silicate). After mixing, the wet flux was supplied to the pelletizing machine, where the granules were compacted, then the flux was first supplied to a rotary drum-type drying oven, and then to the calcining furnace. After calcination, the flux was cooled, sieved, weighed and packaged.

The fabricated flux compositions are conventionally designated: 1, 2, 3, 4, 5.

Table 1 presents 5 options for the compositions of the proposed ceramic flux.

Table 1 Ingredients and their ratio The content of ingredients in the flux, wt.% one 2 3 four 5 Calcined Magnesite 26,4 28.6 30,0 29.75 29.0 Electrocorundum 22.0 18.6 20,0 19.5 19.0 Fluorspar 20.5 20.5 20,0 20,0 20.17 Sphene Concentrate 14.0 14.5 12,2 13.0 14.0 Synthetic Titanium Dioxide 5,0 5.5 6.5 6.0 5.65 Manganese metal 2.0 2.7 3,1 3.0 2,8 Ferrotitanium 0.5 0.4 0.35 0.25 0.3 Ferrosilicon 0.8 0.5 0.5 0.55 0.6 Titanomagnetite 0.5 0.6 0.6 0.6 0.63 Ferroboron 0.2 0.3 0.2 0.37 0.35 Sodium Potassium Silicate (solids) 8.1 7.8 6.55 6.98 7.5 * D / P 0.24 0.27 0.32 0.3 0.28 ** FeTi / FeB 2,5 1.33 1.75 0.67 0.86

***

1.8 2.0 2.1 2.1 2.0 * D / P - the ratio of titanium dioxide and fluorspar.
** FeTi / FeB - ratio of ferrotitanium and ferroboron
*** M, P, C, G, E, D - the ratio of the total content of magnesite, fluorspar and sphene concentrate to the total content of phenic concentrate, sodium potassium silicate (water glass), electrocorundum and titanium dioxide.

To determine the chemical composition, surfacing on the plates was carried out under the manufactured fluxes using low-carbon and low-alloy wires (Sv-08A, Sv-10GNA).

Table 2 shows the chemical compositions of the metal obtained welds during surfacing using 5 options for the composition of the flux.

table 2 Flux Options Welding wire The content of elements in the weld metal,% Carbon Silicon Manganese Nickel Sulfur Phosphorus one Sv-08A 0.11 0.20 0.73 0.2 0.016 0.010 2 Sv-08A 0.11 0.17 1.10 0.67 0.010 0.015 3 Sv-08A 0.08 0.12 1,50 0.46 0.019 0.005 four Sv-10GNA 0,07 0.25 1.70 0.71 0.007 0.012 5 Sv-10GNA 0,07 0.18 1.89 0.80 0.011 0.018

Under these fluxes, in combination with serial wires (low-carbon Sv-0.8A and low-alloyed Sv-10GNA) with a diameter of 4 mm, welded butt joints from steel St3, St10KHSND and St15KHSND were obtained with a thickness of 20 mm with an angle of cutting edges from 15 to 30 ° .

Welding Modes:

- Welding current: 500-700 A.

- Voltage on an arc: 32-38 V.

- Welding speed: 25-36 m / h.

Current is constant, reverse polarity.

Samples were made and tested to determine their mechanical properties and impact strength.

The test data are given in table.3. Table 3 also gives an assessment of the separability of the slag crust from the weld metal when welding butt joints with deep cutting edges.

Table 3 Flux Options Wire mark steel grade Mechanical properties Impact strength, KCV, J / cm ² Slag crust separation Temporary resistance, σ _in , MPa Yield Strength, σ _t , MPa Elongation, δ _s ,% -40 ° C -60 ° C one Sv-08A St3

Satisfactory 2 Sv-08A 15HSND

Good 3 Sv-08A 10HSND

Good four Sv-10GNA 15HSND

Good 5 Sv-10GNA 10HSND

Good Note: The numerator shows the minimum and maximum values, and the denominator shows the average values of mechanical properties and impact strength.

As can be seen from the above data, the proposed flux provides the necessary level of toughness of the weld metal when welding low alloy steels with low carbon wires of at least 50 J / cm ² at a test temperature of -40 ° C and at least 42 J / cm ² at a test temperature of -60 ° C , as well as good formation of weld metal with easy separability of the slag crust when welding butt products with deep cutting edges.

This is ensured by the granular fine-grained structure of the weld metal, which is formed by reducing carbon and reducing titanium from synthetic unbound titanium dioxide with increased thermodynamic stability, introduced into the composition of the proposed flux.

Given the results of impact tests, determined on type IX specimens with a sharp notch, in accordance with GOST [6], at negative temperatures of -40 ° C and -60 ° C, as well as the results of microstructural studies, the optimal composition of the proposed flux was determined - the composition of option 3, the content of the components of the ore-mineral and alloying parts of which are indicated in table 1.

Thus, the proposed flux for the automatic welding of low alloy steels allows the use of low-cost low-carbon wires instead of the more expensive low-alloy and complex alloyed wires for welding critical structures operating in the negative temperature range (-40) - (-60) ° С, which will expand its technological capabilities and will give a significant economic effect.

Information sources

1. A.S. USSR No. 1298029, V23K 35/362.

2. Patent of Russia No. 2228828, V23K 35/362.

3. Konishchev B.P., Kurlanov S.A., Potapov N.N. Welding materials for arc welding. Shielding gases and welding fluxes. M .: Engineering, 1989, t.1, p.138, 203.

4. Kokhanovsky N.I., Fartushny V.G., Yushchenko K.A. Arc welding of steels. Directory. Publishing house "Naukova Dumka", Kiev - 1975, p.241.

5. Stepanov V.V. Welder Reference. Moscow. Engineering. 1974, p. 9.

6. GOST 6996-66 Welded joints. Methods for determining mechanical properties.

Claims (1)

Ceramic flux for automatic welding of low alloy steels containing calcined magnesite, electrocorundum, fluorspar, sphene concentrate, metallic manganese, ferrotitanium, ferrosilicon, titanomagnetite, ferroboron and a binder additive in the form of sodium potassium silicate, characterized in that it additionally contains 98% - synthetic titanium dioxide in the following ratio of components, wt%: Calcined Magnesite 26.4-30.0 Electrocorundum 18.6-22.0 Fluorspar 20.0-20.5 Sphene Concentrate 12.2-14.5 Synthetic Titanium Dioxide 98% 5.0-6.5 Manganese metal 2.0-3.1 Ferrotitanium 0.25-0.5 Ferrosilicon 0.5-0.8 Titanomagnetite 0.5-0.63 Ferroboron 0.2-0.37 Sodium Potassium Silicate 6.55-8.1 the ratio of the total content of calcined magnesite, fluorspar and 1/3 of sphene concentrate to the total content of 2/3 of sphenic concentrate, 2/3 of sodium potassium silicate, 1/2 of electrocorundum and 1/2 of titanium dioxide is selected within 1.8- 2.1, the ratio of ferrotitanium to ferroboron is in the range of 0.67-2.5, and the ratio of synthetic titanium dioxide to fluorspar is in the range of 0.24-0.32.