RU1776526C - Composition of electrode coating - Google Patents

Abstract

The invention relates to welding, in particular to the composition of an electrode coating used primarily for welding cast iron. The purpose of the invention is to increase the strength and machinability of cast iron weld, reducing its tendency to crystallize with bleach. SUMMARY OF THE INVENTION: Aerosil, ferromanganese are additionally introduced into the composition of an electrode coating containing graphite, nickel, kaolin, marble in the following ratio, wt.%: Graphite 5-7; nickel 7-15; kaolin 6-12; Aerosil 5-8; ferromanganese 3-5; marble - the rest. Aerosil provides a weld with high strength, better machinability and less than 1.5-2 times a tendency to crystallization with whitening. Ferromanganese contributes to the bleaching of cast iron. 3 tab.

Description

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The invention relates to welding, in particular to the composition of an electrode coating used primarily for welding cast iron.

The known composition of the electrode coating containing marble, graphite, silicon carbide, kaolin, nickel (A.S. Czechoslovakia No. 150344, class 49 h 36/01, 1967).

However, a weld made with electrodes of known composition has a tendency for the weld metal to crystallize with bleaching.

Closest to the proposed composition and the achieved effect is the composition of the electrode coating, containing, wt.%: Graphite 6-10; nickel 8-16; kaolin 12-26: marble 60 (see Autobahn. USSR No. 893481, class B 23 K 35/365. 1981).

The disadvantage of this coating composition is the insufficient strength and tendency of the weld metal to crystallize with bleaching. The absence of a low-temperature deoxidizer in the coating contributes to the saturation of the weld metal at the drop stage with oxygen. An increase in the content of graphite in the coating increases the size of graphite inclusions in the weld, which impairs the mechanical properties of cast iron.

The purpose of the invention is to increase the strength and machinability of cast iron weld, reducing its tendency to crystallize with bleach.

The goal is achieved by the fact that the composition of the electrode coating containing graphite, nickel, kaolin, marble, additionally introduced aerosil, ferromanganese, in the following ratio of components.

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wt.%: graphite 5-7; nickel 7-15; kaolin 6-12; Aerosil 5-8; 3-5 ferromanganese and marble - the rest.

Aerosil (GOST 14922-77) is an amorphous form of silica, consisting of elementary spherical particles SIOz in size less than 1000 A, the surface of which is formed from anhydrous SI02. In aerosil such particles form three-dimensional three-dimensional aggregates of particles. The peculiarity of aerosil, allowing its use as a modifier of cast iron, is the amorphous structure of its particles and their developed surface. Compared to crystalline silicon dioxide with a specific particle surface of 1-10 m2 / g, Aerosil has a specific surface of 175-380 m2 / g.

Aerosil particles with an amorphous structure act as an effective substrate for graphite inclusions released from the melt coating, which ensures the grinding of the graphite phase and the increase in the number of eutectic cells during the welding process. Grinding eutectic cells reduces the segregation of silicon and manganese, which is accompanied by the formation of a uniform pearlite base of the weld of cast iron. As a result of exposure to aerosil, which grinds the graphite phase and binds carbide-stabilizing impurities, the strength of deposited cast iron increases, but the tendency to crystallization with bleaching decreases by 1.5-2.0 times.

In the structure of the welded joint of cast iron, aerosil particles are located inside graphite inclusions and do not have an abrasive effect on the cutting tool, which provides an increase in the machinability of cast iron by 20-25%, reduces the cost of the cutting tool.

The addition of Aerosil provides the weld with greater strength, better machinability and less tendency to crystallization with bleaching.

The addition of aerosil below the lower limit does not provide a developed surface that allows increasing the number of eutectic cells and, as a result, does not provide an increase in the strength and machinability of cast iron, 8 and also reduces its tendency to whiten crystallization during welding.

When the aerosil content is more than 8%, the viscosity of the slag increases and its gas permeability decreases.

Ferromanganese is introduced into the coating composition as a deoxidizing agent, which acts during crystallization of a liquid bath, as well as to reduce the percentage of sulfur in

seam metal. A ferromanganese content below 3% does not provide sufficient deoxidation and refinement of the weld metal. The content of ferromanganese in the given

positively affects the graphitization process, eliminates the negative effect of sulfur in the weld metal, forming with it sulfur manganese MnS, poorly soluble in liquid and solid cast iron and relatively easily removed from metal to slag. When the content of ferromanganese exceeds 5%, the conversion of manganese to cast iron increases, which helps stabilize the carbide formation process, i.e. promotes whitening

cast iron.

Kaolin is introduced into the coating as a slag-forming component and at the same time as a good plasticizer. The introduction of kaolin below 6% does not provide good plastic properties of the coating, reliable slag protection. The introduction of kaolin in excess of 12% reduces the quality of the electrode coating, contributes to the formation of cracks in the coating and during drying of the electrodes.

Graphite is present in the coating composition as a deoxidizer and a carbon source in the weld metal. The specified ratio determines the optimal carbon content in the weld metal, increase or

a decrease in this ratio leads to a change in the quality of the weld metal.

Nickel is added to the electrode coating in an amount of 7-15%. The main feature of nickel is that it

prevents the formation of free carbides. The introduction of nickel below 7% slightly expands the region of the γ phases; with an increase in the percentage of nickel up to 15%, its effect on expansion

γ-phase, helps to maintain the greatest amount of free graphite, reduces the tendency of the weld metal to crystallize with whitening. The management of nickel in an amount of over 15% is not economically feasible, so

how increases the cost of electrodes without noticeable improvements in welding performance.

For experimental verification of the proposed electrode coating composition, five ingredient compositions were prepared, of which 2, 3, 4 compositions showed optimal results.

The welding rods of the brand were used as electrode rods.

Sv08A (Sv08).

The compositions of the electrode coatings are presented in table 1. From the rest 6 taken according to the prototype. The chemical composition of the deposited metal is given in table.2.

To determine the hardness of the deposited metal and the fusion line, multilayer welding of various defects with a depth of 10-12 mm and an opening angle of 90 ° was performed.

Welding was performed with electrodes with a diameter of 5 mm at a constant current of reverse polarity. Template was cut out from brewed areas for sample preparation.

The tendency of cast iron to bleach was determined by the depth of the bleached zone in the fracture of the samples.

Machinability was determined by the wear of a VK-8 alloy brazed tool in 30 minutes with turning at V-65 m / min, S - 0.8 mm / rev, t -1.5 mm. The results of the mechanical properties and wear of the cutter are shown in table.3.

high welding and technological properties of the electrode coating of the proposed composition contribute to

Coating Compounds

The chemical composition of weld iron

deposited metal with a uniform chemical composition, increased mechanical properties, reduce the ability of the weld metal and the heat-affected zone to bleach and reduce the cost of a cutting tool during machining.

Claims (1)

The formula of the invention 0 The composition of the electrode coating for welding cast iron containing marble, graphite, nickel, kaolin, characterized in that, in order to reduce the tendency to bleach, the composition additionally contains aerosil and ferromanganese in the following ratio, wt.%: Graphite 5-7 Nickel 7-15 Kaolin6-12 Aerosil 5-8 : Ferromanganese 3-5 Marble Table 1 table 2 Technological and mechanical properties of cast iron Table 3