RU2319590C2 - Electrodes for manual welding of steels of pearlite class - Google Patents

Abstract

FIELD: processes and equipment for welding pearlite-class steels used, for example for protecting housings of nuclear power stations, nuclear heat power central stations and so on without preliminarily heating and further heat treatment.

SUBSTANCE: rod of wire of given kind has coating containing next relation of components, mass %: marble, 40 - 53; quartz sand, 3.0 - 9.2; titanium, 7.0 - 15.5; zirconium, 0.05 - 6.0; ferrotitanium, 5 - 6; metallic manganese, 0.5 - 1.0; potassium carbonate, 1 - 2; fluorspar, the balance; melt glass (to dry mass of mixture), 23 - 25. Relation of content of CaCO₃ to total content of acidic oxides ( SiO₂ + TiO₂ + ZrO₂ ) is to be in range 1.82 - 2.85. Electrodes allow increase plastic and viscous properties and decrease critical temperature of seam metal embitterment in initial state in range (-60) - (50)°C without preliminary heating and further heat treatment while providing spontaneous separation of slag scum including root part of dressing for welding.

EFFECT: improved properties of seam metal with use of such electrodes.

4 tbl

Description

The invention relates to the field of production of welding materials for welding products of nuclear power engineering and can be used in various industries for welding pearlite class steels.

Of the known electrodes used for the indicated purpose in the respective industries, the electrode closest to the application electrodes for the purpose and composition of the coating components is an electrode coating using welding wire of the Sv-08G2S grade in accordance with a.c. No. 554120 dated 04/15/77. M. cl ² B23K, 35/365, containing, wt.%:

Marble 50-70 Fluorspar 10-25 Rutile 3-15 Quartz sand 2-10 Ferrotitanium 1-4 Ferrosilicon Calcium 1-4 Hematite 1-4

The main disadvantages of these electrodes are the insufficiently high level of plastic and viscous properties of the weld metal, the high critical temperature of the brittleness of the weld metal (Tk _o , ° C) in the initial state and the absence of spontaneous separability of the slag crust, including the root part of the weld. The technical result of the invention is to provide an electrode for welding protective housings NPP, NCP, and other products made from pearlitic steels that improve the level of plastic, the viscous properties of the weld metal and to reduce the value _of Tc in the initial state within (-60 ÷ -50 ° C) without preheating and subsequent heat treatment to ensure spontaneous separability of the slag crust, including the root part of the cutting for welding.

The technical result is achieved by the fact that the metal rod is made of Sv-08GS wire, and the composition of the electrode coating contains marble, fluorspar, silicon dioxide, titanium dioxide, ferrotitanium, liquid glass, zirconium dioxide, metallic manganese and potassium carbonate are additionally introduced ( potash) in the following ratio of components:

Marble 40-53 Quartz sand 3-9,2 Titanium dioxide 7-15.5 Zirconium dioxide 0.05-6 Ferrotitanium 5-6 Manganese metal 0.5-1 Potassium carbonate (potash) 1-2 Fluorspar rest Liquid glass (to the mass of the dry mixture) 23-35,

the ratio of the content of CaCO ₃ to the sum of acid oxides (SiO ₂ + TiO ₂ + ZrO ₂ ) should be 1.82-2.85.

The introduction of zirconia (ZrO ₂ ) into the coating in an amount of 0.05-6% leads to the release of a low concentration of ZrO ₂ and iron oxide (FeO) oxides in the intermediate layer between the slag crust and the weld metal.

The mismatch of the lattice sizes of these oxides is 13.9 and 6.18, respectively, increases the interfacial tension of the slag, reduces the adhesion - the bond strength of the slag crust with the metal, which leads to spontaneous separability of the slag crust, including the root part of the groove for welding, and helps to achieve a technical result .

The introduction of zirconia into the coating in an amount below 0.05% does not provide a high interfacial tension of the slag on the weld surface, reduce its adhesion and does not contribute to its spontaneous separability.

The introduction of zirconium dioxide into the coating is more than 6%: it is unacceptable to increase the oxidizing ability of the coating, reduces the recovery of the required amount of C, Si and Mn from the composition of the Sv-08GS wire in the weld metal, and an intermediate layer with a high concentration of compounds (oxides, spinels) is formed on the surface of the weld metal ), which together does not contribute to the achievement of the technical result.

The introduction of metallic manganese in an amount of 0.5-1% contributes to the deoxidation of the molten metal electrode in the arc zone, the weld pool metal and the refining of the bath metal by binding sulfur to manganese sulfide (MnS) with its transition to slag.

Manganese oxide (MnO) formed during deoxidation lowers the viscosity of slag.

The decrease in the oxygen and sulfur content in the weld metal during deoxidation with manganese metal increases the plastic, viscous properties of the weld metal, reduces the values of Tk _about in the initial state, which helps to achieve a technical result.

The introduction of metallic manganese in an amount below 0.5% is insufficient for deoxidation of the molten metal of the electrode in the arc zone, the weld pool metal and the binding of sulfur to manganese sulfide (MnS).

An increase in metallic manganese in the coating of more than 1% activates silicon and manganese reduction processes, an increase in the transition of oxide inclusions based on SiO ₂ into the weld metal, which impedes the achievement of a technical result.

Introduction to the coating of potash (K ₂ CO ₃ · 1,5H ₂ O) - a component with a reduced ionization potential - in an amount of 1-2% increases the stability of arc burning at a significant content that reduces the ionization of the welding arc, cinder-forming fluorspar - CaF ₂ .

A decrease in the coating of potash electrodes of less than 1% reduces the stability of arc burning.

Introduction to the coating of potash more than 2% increases its undesirable hygroscopicity.

The ratio in the coating of marble (CaCO ₃ ) to the sum of acid oxides (SiO ₂ + TiO ₂ + ZrO ₂ ) should be 1.82-2.85. The indicated optimal limits provide

- reduced oxidizing ability of the coating and low content of spinel-shaped oxides in the slag;

- the low limits of the slag basicity coefficient (K ^sh _o ) in the range of 1.12-1.34 contribute to the optimal, for alloying the weld metal, the intensity of the flow of silicon and manganese-oxidizing processes with the restoration of the required amount of carbon, silicon and manganese;

- spontaneous separability of the slag crust.

When the ratio of CaCO ₃ in the coating to the total amount of acidic oxides (SiO ₂ + TiO ₂ + ZrO ₂ ) is less than 1.82, it leads to a decrease in the oxidizing ability of the coating, an increase in silicon and manganese reduction processes with a deterioration in the welding and technological properties of the electrodes, which prevents the achievement of a technical result .

более 2,85 происходит сильное окисление раскисляющих и легирующих элементов - С, Si и Mn - в сварочной проволоке Св-08ГС с частичным переходом в металл шва продуктов раскисления ванны (SiO₂, MnO, AlO₃, TiO₂), включая нерастворимую в сварочной ванне и шлаке закись железа (FeO) повышенной концентрации, снижающими пластические и вязкие свойства металла шва, что не способствует достижению технического результата.With increasing ratio

more than 2.85, the deoxidizing and alloying elements — C, Si and Mn — are strongly oxidized in the Sv-08GS welding wire with a partial transition to the weld metal of the bath deoxidation products (SiO ₂ , MnO, AlO ₃ , TiO ₂ ), including insoluble in the welding bath and slag iron oxide (FeO) of increased concentration, reducing the plastic and viscous properties of the weld metal, which does not contribute to the achievement of the technical result.

The introduction of ferrotitanium into the coating in an amount (5-6%) deoxidizes and partially modifies the weld metal with titanium in the optimal range (0.016-0.028%).

Reduced titanium within the specified limits binds carbon and nitrogen into refractory carbides of carbon, nitrogen (TiC, TiN), which grind the grain of the weld metal during crystallization, which leads to an additional increase in the plastic, viscous properties and a decrease in the TC _{of the} weld metal.

The introduction of less than 5% ferrotitanium into the coating reduces titanium to the weld metal less than 0.016%, which is not enough to bind carbon and nitrogen to the optimum amount of refractory carbides - TiC and TiN - for grinding grain.

The introduction of ferrotitanium into the coating of more than 6% promotes an undesirable and excessive silicon reduction process, as well as the restoration of titanium in the weld metal of more than 0.028%, which is impractical.

The proposed ratio of components in the electrode coating and the doped rod of wire brand Sv-08GS allows you to get electrodes that provide:

- high stability of arc burning, lack of spatter, undercuts and high resistance of the weld metal to pore formation;

- obtaining a “short” welding slag with a low basicity coefficient (K ^w _o ) in the range (1.12 ÷ 1.34), which corresponds to high plastic and viscous properties (A5, KCV) and low values (Tk _o ) of the weld metal within (-60 ÷ -50 ° С);

- the presence in the "short" welding slag of a low concentration of spinels and surface-active oxides - FeO, Al ₂ O ₃ , MnO, which contributes to spontaneous separability of the slag crust, including the root part of the weld.

When creating the electrodes, the method of mathematical planning of experiments (MMPE) of the 28 studied experimental compositions was used.

A complex of laboratory and pilot works on the manufacture and practical testing of electrodes for welding pearlite-grade steels was carried out at the FSUE Central Research Institute KM "Prometey".

For the manufacture of electrodes was used wire Sv-08GS, GOST 2246-70 made in Sweden with a low content of impurity elements, especially for sulfur and phosphorus of 0.009 and 0.003%, respectively.

The electrodes were made in pilot production at the installation for the production of coated electrodes of the Swiss company Oerlikon.

Prototypes of the proposed electrode compositions were tested by arc welding on pearlite steel grade 22K with a thickness of 40 mm.

Welding was performed on billets with an X-shaped groove, alternately from 2 sides, with a direct current of reverse polarity without preheating and heat treatment.

Welding modes were as follows:

The diameter of the electrode is 4 mm, Isv. = 165-180 A; the diameter of the electrode is 5 mm, Is. = 190-210 A. The position of the seam is lower. The inter-pass temperature was not more than 100 ° C.

Visual inspection and radiographic inspection of the weld metal showed the absence of splashing and unacceptable defects: cracks, lack of penetration, non-metallic inclusions.

Samples for determining the chemical composition of the weld metal, slag crust (calculation of its basicity and separability characteristics), as well as the mechanical properties of the weld metal, were made and tested from weld metal obtained using the electrodes of the proposed and known composition. The test and calculation results are presented in Tables 1-4.

The comparative chemical composition of the welding wire and electrode coatings are presented in Tables 1 and 2.

The chemical composition of the weld metal made by the electrodes and the results of comparative tests of the electrodes are presented in Tables 3 and 4.

The results of comparative tests show that the claimed electrode compositions in comparison with the known ones provide the weld metal stably high plastic and viscous properties (A5, KCV) and low values of Tk _about (-60 ÷ -50 ° C) when welding pearlitic steels. Electrons have no tendency to spray and vaporize. In addition, an important advantage is the spontaneous separability of the slag crust, including the root portion of the groove for welding.

The expected technical and economic effect will be expressed in increasing the operational reliability of welded products that are not subject to heating and heat treatment, as well as in increasing labor productivity and reducing the complexity of work.

Table 1
The comparative chemical composition of the welding wire of the grades Sv-08GS and Sv-08G2S used for the manufacture of electrodes of the proposed and known composition Wire mark Chemical composition FROM Si Mn Cr Ni Mo Al Ti Cu As N ₂ S P Sv-08gs square No. 5189 0.09 0.71 1,56 <0.01 0.19 0.01 0.009 0.010 0.04 0.005 0.003 0.009 0.003 Sv-08g2s 0.010 0.83 1.92 0.18 0.18 - - - - - - - -

table 2
Comparative chemical composition of electrode coatings Structure Conventional composition number The composition of the coating, wt.%

Marble Silica Titanium dioxide Zirconium dioxide Ferrotitanium Manganese Metallic Potash Ferro-silico-calcium Hematite Fluorspar Liquid glass Proposed one
2
3
four 53
43
43
40 3
6
3
9.2 15,5
7
fifteen
12.7 0.05
6
3
0.05 6
5
5
5 1,0
0.5
0.5
0.5 one
one
one
2 -
-
-
- -
-
-
- rest
rest
rest
rest 35
25
25
23 2.85
2.26
2.04
1.82 Famous 5 70 2 fifteen - one - - one one 10 25 -

Table 3
The chemical composition of the weld metal made by electrodes Structure Conventional composition number The content of elements in the weld metal FROM Si Mn Cr Ni Ti Al S P Cu [O] [N] one 0.06 0.22 0.89 0.10 0.20 0.016 0.008 0.012 0.010 0.08 0,027 0.009 The claimed 2
3 0,07
0.06 0.38
0.31 0.92
0.90 0.10
0.10 0.16
0.14 0,023
0,028 0.008
0.007 0.014
0.014 0.008
0.009 0,07
0.09 0,047
0,040 0.008
0.007 four 0,07 0.44 0.92 0.10 0.19 0,023 0.008 0.014 0.009 0,07 0,043 0.0065 Famous 5 0.09 0.46 1.17 0.10 0.17 0,053 0.008 0.014 0,026 0.08 0,044 0.008

Table 4
The results of comparative tests of electrodes Structure Conventional composition number Weld metal characteristic The critical temperature of fragility Tk _about , ° C, The estimated coefficient of basicity of the slag crust, K ^sh _about Slag Peel Separation Characterization Yield Strength, MPa Tensile strength, MPa Relative extension, % KCV hit work,
J / cm ² T = + 20 ° C T = -40 ° C The claimed one 382 486 33.8 276 146 -fifty 1.34 self separability 2 438 546 27.9 283 182 -60 1.29 - // - 3 441 541 26.5 295 154 -60 1.12 - // - four 544 629 28.0 291 174 -60 1.15 - // - Famous 5 327 418 26.3 247 55 -10 1.42 using instrument Note:
1. The data are averaged according to the test results of 3 samples per point.
2. The mechanical properties of the weld metal were determined on the metal in the initial state.

Claims (1)

An electrode for manual welding of pearlite-grade steels, consisting of a steel rod made of welding wire and a coating containing marble, fluorspar, quartz sand, titanium dioxide, ferrotitanium and liquid glass, characterized in that the steel rod is made of Sv-08GS wire, and the coating additionally contains zirconia, manganese metal and potash in the following ratio of components, wt.%: Marble (CaCO ₃ ) 40-53 Quartz sand (SiO ₂ ) 3-9,2 Titanium dioxide (TiO ₃ ) 7-15.5 Zirconium Dioxide (ZrO ₂ ) 0.05-6 Ferrotitanium 5-6 Manganese metal 0.5-1 Potash (potassium carbonate) 1-2 Liquid glass (to the mass of the dry mixture) 23-35 Fluorspar Rest the ratio of CaCO ₃ to the sum of acid oxides (SiO ₂ + TiO ₂ + ZrO ₂ ) is 1.82 ÷ 2.85.