RU2407617C1 - Electrode for arc welding and resurface welding - Google Patents

Abstract

FIELD: process engineering. ^ SUBSTANCE: invention can be sued in arc welding or resurface welding for modification of weld metal by nano-sized refractory particles. Two-layer coat is applied onto metal rod surface. Coat inner layer comprises slag- and gas-forming components. Outer layer consists of pulverised mix of micro- and/or nano-sized refractory components with binder. Coat outer layer thickness makes 1.8-9 % of metal rod diametre and is selected depending upon coat inner layer thickness. Coat outer layer can be discrete or continuous. Outer discrete layer represents longitudinally or spirally arranged grooves of V, U or "" shape arranged regularly on the coat inner layer surface. ^ EFFECT: higher reliability in production and operation. ^ 6 cl, 2 dwg, 2 tbl, 2 ex

Description

The invention relates to welding materials used in metallurgical, petrochemical and general mechanical engineering, and can be used in manual arc welding or surfacing processes to modify deposited metal with nanosized refractory particles.

A known electrode for arc welding (USSR Author's Certificate No. 1825701 Al, B23K 35/365, 35/365, publ. Bull. No. 25, 07/07/1993), which is a metal rod with a two-layer coating, the inner layer of which is made of composition: plasticized nitrocellulose and gunpowder based on nitrocellulose. However, the construction of such an electrode does not provide for a ratio of layer thicknesses, which does not allow one to choose their optimal sizes.

Known electrode (USSR Author's Certificate No. 77181 of 08/27/1949), which is a metal rod and a three-layer coating. The inner coating layer, applied directly to the metal rod, contains alloying elements, and the remaining coating layers contain slag and gas-forming components. Contacting during the welding process with a high-temperature arc column, the inner coating layer is quickly melted, and the melt of alloying components is mixed with the rod melt, forming drops. Thus, introducing whole micro- and / or nanosized refractory components into the inner layer of the electrode coating is irrational, since this will lead to their complete melting in the arc column and will not allow to obtain the effect of nanomodification of deposited metal.

A known electrode (RF patent No. 2244615 C1, B23K 35/365, 35/10, publ. 20.01.2005), the coating of which is divided into two layers, one of which contains slag-forming and gas-forming components, and the other consists of activating components. Coating layers may be placed on the surface of a metal rod in a different order. The disadvantage of this electrode is the possible destruction of its coating during heat treatment, as well as as a result of heating of the electrode during welding due to different values of the coefficients of thermal expansion of the coating layers.

The closest technical solution to the claimed electrode is an electrode for arc welding (RF patent No. 539723, V23K 35/365, 35/04, publ. 12/25/1976), the coating of which is divided into two layers, the inner layer of the electrode coating contains slag-forming and gas-forming components, and particles of refractory compounds selected from the group of nitrides, carbides, borides and exides of 0.1-1.5 mm in size were added to the outer layer of the electrode coating. The disadvantage of this electrode is the high (in% of the diameter of the metal rod of the electrode) value of the ratio of the thicknesses of the inner and outer layers, which, when micro- and nanosized powders of refractory compounds are introduced into the outer coating layer, will inevitably lead to their penetration into the high-temperature region of the welding arc, where they dissociate and the reaction products dissolve in the metal of droplets, the temperature of which (2200 ... 2400 ° C) significantly exceeds the temperature of the weld pool (1700 ... 1800 ° C), the effect of modifying the weld metal is not real zuetsya.

It is also possible the destruction of the inner layer of the coating when applied to it by pressing the outer layer.

The technical result consists in the creation of an electrode with increased technological reliability and the possibility of obtaining whole micro- and / or nanosized refractory components in the deposited metal due to their location in the outer layer of the electrode coating, which ensures the transition of the refractory components into the weld pool through a low-temperature peripheral area of arc space.

The technical result is achieved in that in the electrode for arc welding and surfacing, consisting of a metal rod and a two-layer coating deposited on the surface of this rod, the inner coating layer contains slag and gas-forming components, and the outer coating layer consists of a powder mixture of micro- and / or nanosized refractory components with a binder, while the thickness of the outer coating layer is from 1.8 to 9% of the diameter of the metal rod, depending on the thickness of the inner coating layer.

The outer coating layer is made in the form of a continuous layer.

The outer coating layer is made in the form of a discrete layer.

The outer discrete layer is formed by placing its components in longitudinally or helically arranged grooves uniformly distributed on the surface of the inner coating layer and at a distance of 0.5 to 3.0 mm from each other.

The grooves on the surface of the inner layer are made of V, U and U-shaped.

As refractory components, it contains elements of the group of transition metals and their refractory chemical compounds with carbon or nitrogen, or boron, or phosphorus, or sulfur.

The outer coating layer contains micro- and / or nanosized refractory components, which, when introduced into the molten pool of the weld pool, are crystallization centers, which provides modification of the weld metal and, accordingly, improves the mechanical and operational properties of welded joints and deposited metal. As refractory components, elements of the group of transition metals and their refractory chemical compounds with elements such as carbon, nitrogen, boron, phosphorus and sulfur are used.

The thickness of the outer coating layer of the electrode, which is in the range of 1.8-9% of the diameter d of the metal rod, is selected based on the thickness of the inner coating layer, which is taken as the coating thickness of standard electrodes regulated by GOST 9466-75, which is regulated depending on the ratio D / d (D is the diameter of the rod coated on it), the electrodes are divided: with a thin, with an average, with a thick and especially thick coating. Given the data of GOST 9466-75, the thickness of the outer coating layer will be selected from the ranges:

for electrodes with a thin coating of 1.8% d≤S ' _rm <6% d;

for electrodes with an average coating of 2.1% d <S ' _rpm <7.25% d;

for electrodes with a thick coating of 2.7% d <S ' _rm <9% d,

where S _obm - the thickness of the outer layer of the coating.

The thickness of the outer coating layer of electrodes with a particularly thick coating type is chosen experimentally, due to the fact that the maximum thickness of the inner coating layer is not specified in GOST 9466-75.

The proposed intervals of the thickness of the outer layer of the electrode coating provide the transition of particles of refractory components to the peripheral part of the arc space. With a decrease in the thickness of the outer layer of electrode coatings of less than 1.8% d, 2.1% d, and 2.7% d, respectively, for electrodes with a thin, medium, and thick coating, the number of refractory components introduced into the metal decreases significantly, which does not allows you to modify the weld metal. With an increase in the thickness of the outer layer of electrode coatings of more than 6% d, 7.25% d and 9% d, respectively, the number of refractory components introduced into the metal increases significantly, which leads to a decrease in the level of ductility and the formation of cracks in the deposited metal, due to the excess content of refractory components along the boundaries of its grains.

In the electrode with a thin inner coating layer, the outer layer can be continuous (Fig. 1). In this case, the thermal stress in the thin layer is small and its destruction does not occur. In an electrode with a middle and thick inner coating layer, the outer coating layer is discrete, which reduces the likelihood of destruction and cracking of the coating layers. In both cases, the outer layer of the electrode coating consists of a powder mixture with a binder. The composition of the powder mixture includes micro- and / or nanosized refractory components, which allows you to apply the outer coating layer by known methods. As components of the outer electrode coating layer, refractory elements of the group of transition metals and their refractory chemical compounds are used. Such compounds are carbides, nitrides, borides, fluorides, sulfides, carbonitrides, carboborides, carbosilphides and nitrocarbides of elements of this group.

In the case of the outer layer in a discrete version, it is a longitudinal (figure 2) or spiral (figure 3) grooves of V, U and U-shaped (figure 4, 5 and 6), uniformly distributed on the surface of the inner layer coatings and located at least 0.5 mm apart. If the grooves are closer than the specified value, they will be stress concentrators, which increases the likelihood of destruction of the inner layer of the electrode coating.

The invention is illustrated by drawings.

Figure 1 shows an electrode with a continuous outer coating layer;

Figure 2 shows an electrode with a discrete outer coating layer, the grooves of which are located longitudinally;

Figure 3 shows the electrode with a discrete outer coating layer, the grooves of which are arranged in a spiral;

Figure 4 shows the electrode with a V-shaped grooves of the outer discrete coating layer;

Figure 5 shows the electrode with a U-shaped grooves of the outer discrete coating layer;

Figure 6 shows the electrode with a U-shaped grooves of the outer discrete coating layer;

7 shows the microstructure of the weld metal (x1000).

The proposed electrode for arc welding and surfacing contains a metal rod 1 and a coating consisting of two layers. The inner layer 2 of the coating is applied directly to the rod 1 and contains slag-gas-forming components. On the surface of the inner coating layer 2, an outer coating layer 3 is deposited, consisting of a powder mixture of micro- and / or nanosized refractory components with a binder. As these components, elements of the group of transition metals and their refractory chemical compounds are used. The thickness of the outer layer 3 of the coating, depending on the thickness of the inner layer 2 of the coating, is in the range of 1.8-9% of the diameter of the metal rod 1. The outer layer 3 of the coating can be either continuous (Fig. 1) or discrete. The discrete outer coating layer 3 can be made on the surface of the inner layer 2 in the form of uniformly distributed longitudinally located grooves (figure 2) or in the form of spiral grooves arranged with a constant pitch (figure 3). The grooves of the discrete outer coating layer 3 may be V-shaped (FIG. 4), U-shaped (FIG. 5) and U-shaped (FIG. 6).

Example 1

The starting materials for the manufacture of the electrode with a two-layer coating were: an UONI 13/45 electrode according to GOST 9466-75 with a core diameter of 3 mm with a thin coating of the main type, made with a thin coating, and a composite powder Ni + WC, consisting of an electrolytic nickel powder with particle size of 50-80 microns, containing 30% nanoscale (20-70 nm) WC carbide obtained by ion-plasma spraying, as well as a binder - liquid potassium-sodium glass.

A thin layer of water glass was applied to the coating surface of the standard electrode, which in this case was the inner coating layer of the claimed electrode, then a layer of composite powder Ni + WC with a thickness of S ' _rm = 2% · d = 0.02 · 3 mm = 0.06 mm Next, the electrode was dried in air at a temperature of 25 ° C for 12 hours, and then heat treated in an electric furnace for two hours at a temperature of 300 ° C. Manual arc surfacing was performed on a plate of steel 20 with a direct current of reverse polarity. The welding current was 120 A.

Similarly, experiments were conducted using electrodes with different thicknesses of the outer coating layer. The test results are shown in table 1.

Example 2

The starting materials for the manufacture of the electrode with a two-layer coating were: an UONI 13/45 electrode in accordance with GOST 9466-75 with a core diameter of 3 mm with an average coating thickness of the main type, made with a thin coating, and a Ni + WC composite powder consisting of nickel electrolytic powder with a particle size of 50-80 microns, containing 30% nanoscale (20-70 nm) WC carbide obtained by ion-plasma spraying, as well as a binder - liquid potassium-sodium glass.

On the surface of the coating of the standard electrode, which in this case was the inner coating layer of the inventive electrode, V-shaped grooves were applied at a distance of 1 mm from each other. The depth of the grooves (thickness of the outer coating layer) was S ′ _rm = 4% · d = 0.04 · 3 mm = 0.12 mm. Then a mixture was prepared: wt.%, 10% liquid potassium-sodium-glass and 90% composite powder Ni + WC, and the grooves made on the surface of the coating of the standard electrode were filled with it. Next, the electrode was dried in air at a temperature of 25 ° C in

Table 1 The influence of the thickness of the outer coating layer on its quality and structure of the weld metal An object Execution of the outer coating layer Thin inner coating Middle inner coating layer Thick inner coating The state of the outer layer of the coating under thermal stress The nature of the structure of the weld metal 1.8% d 2.1% d 2.7% d Fine-grained structure 4% d 5% d 6% d deposited metal. Homogeneous solid solution with uniformly distributed refractory nanosized particles 6% d 7.25% d 9% d No damage, cracks or other defects solid 1,1% d 1,1% d 2% d Inhomogeneous solid solution with periodically occurring refractory nanosized particles Proposed 7% d 8% d 12% d Destruction of the outer layer of the coating The fine-grained structure of the weld metal. Homogeneous solid solution with refractory nanosized particles on
grain boundaries (d = 3 mm) - 2.1% d 2.7% d Homogeneous fine-grained - 5% d 6% d solid solution with evenly - 7.25% d 9% d Destruction, cracks and other
no defects distributed refractory nanosized particles discrete - 1,1% d 2% d Inhomogeneous solid solution with periodically occurring refractory nanosized particles - - 9% d 12% d Destruction of the outer layer of the coating The fine-grained structure of the weld metal. Homogeneous solid solution with refractory nanosized particles at grain boundaries. Prototype solid - Destruction of the outer layer of the coating Homogeneous coarse-grained

for 12 hours, and then heat treated for two hours in an electric furnace at a temperature of 300 ° C. Manual arc surfacing was performed on a plate of steel 20 with a direct current of reverse polarity. The welding current is 120 A.

Similarly, experiments were conducted using electrodes with different thicknesses of the outer layer of the coating, made in the form of grooves. The test results are shown in table 1. Also tested the electrodes, in which the grooves in the outer layer were located at different distances. The test results are presented in table 2.

The metal deposited by the proposed electrode is characterized by a fine-grained structure. In the metal structure, which is a homogeneous solid solution, nanosized WC carbides are evenly distributed (Fig. 7).

In the examples shown, nanosized WC carbide powder was introduced into the outer electrode coating layer. Because WC has one of the lowest melting points among the known refractory chemical components. The use of other components from the group of transition metals and their refractory compounds as nanoscale components of the outer layer does not change the nature of the transition of these components through the arc and does not exclude the possibility of modifying the deposited metal.

table 2 The influence of the distance between the grooves on the possibility of modification
weld metal The distance between the grooves, mm The state of the inner coating layer The number of refractory components in the weld metal 0.2 Cracks in the coating Enough for 0.5 metal modifications one No cracks, coating More than 3 quality Not enough for metal modification

The manufacture of the electrode of the proposed design gives in comparison with the known electrode designs the following positive effect:

- increase the technological reliability of the electrode in the process of its manufacture and use;

- the possibility of obtaining in the weld metal whole micro- and / or nanoscale refractory components.

Claims (6)

1. The electrode for arc welding and surfacing, consisting of a metal rod and a two-layer coating deposited on the surface of this rod, the inner coating layer contains slag and gas-forming components, and the outer layer is refractory components, characterized in that the outer coating layer consists of powder a mixture of micro- and / or nanosized refractory components with a binder, while the thickness of the outer coating layer is from 1.8 to 9% of the diameter of the metal rod, depending on the thickness of the inner layer covering. 2. The electrode according to claim 1, characterized in that the outer coating layer is made in the form of a continuous layer. 3. The electrode according to claim 1, characterized in that the outer coating layer is made in the form of a discrete layer. 4. The electrode according to claim 3, characterized in that the outer discrete layer is formed by placing its components in longitudinally or helically arranged grooves uniformly distributed on the surface of the inner coating layer at a distance of 0.5 to 3.0 mm from each other. 5. The electrode according to claim 4, characterized in that the grooves on the surface of the inner layer are made of V, U and U-shaped. 6. The electrode according to claim 1, characterized in that, as refractory components, it contains elements of a group of transition metals and their refractory chemical compounds with carbon, or nitrogen, or boron, or phosphorus, or sulfur.

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