RU2000185C1 - Composition for electrode coating - Google Patents

Abstract

The invention relates to welding, in particular, to the composition of the electrode coating, which is used mainly for welding without heating under mounting conditions of hard joints of long joints from low alloy high strength steels of type 16GMYUCH, 15G2SF. The purpose of the invention is to create such an electrode coating that would provide high resistance to cracking in welds of great length under conditions of increased concentration of welding stresses, and also meet the requirements of the chemical composition and mechanical properties of the weld metal without heat treatment after welding, which it is especially important when carrying out repair work in installation conditions. This goal is achieved by containing in the composition of the electrode coating powder cobalt 11-18% and ferromolybdenum 2-3% and the addition of rutile mica flour and feldspar in the following ratio, wt.%: Marble 42-45, fluorspar 18-25; feldspar 2-4, mica for flour 2-3, rutile 4-6, ferrosilicon 7-9. ferromanganese 3-6. A carbon content of not more than 0.06% is provided in the seam. 3 tab.

Description

FIELD: welding. SUBSTANCE: invention relates to welding, in particular, to the composition of an electrode coating, which is used mainly for welding without heating under mounting conditions of rigid assemblies, long-seams of low alloy steels of type 16GMYUCH, 15G2SF.

Known composition of the electrode coating containing the following components, wt.%:

Marble 10-25

Fluorspar 7.5-15

Titanium dioxide

Chrome metal 2-8

Molybdenum 8-30

Cobalt5-24

Ferrosilicon Ferrovanadium Ferrotitanium Nickel powder Aluminum

1-6

0.5-1E

5-15

6-28

2.5-6

Electrodes with such a precoated coating: started for cladding die tools and provide maraging steel with high hardness - 38-40 HRc i low plasticity, which excludes their use for welding low alloy steels for general purposes among vessels operating under pressure. In addition, the high total content of alloying elements causes embrittlement about

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weld metal at a weldment operating temperature of 520 ° С.

Also known is calcium fluoride coating of OZS-2 brand electrodes containing components, wt.%:

Marble44

Fluorspar21

Quartz sand2

Mica on flour 3

Rutilb

Ferrosilicon15

Manganese ore9

Water glass30% by weight

dry charge.

However, both these electrodes and similar ones - TML-IV, UONII 13/55 grades, do not provide, when welding 16GMYUCH steel under installation conditions, the absence of cracks in the welds formed after some time after welding. In addition, the weld made with UONII 13/55 electrodes does not contain molybdenum, the need for which (about 1%) is dictated by the high-temperature operation of coke oven chambers.

The closest solution to the proposed composition of the electrode coating is a coating containing the following components, wt.%:

Marble35-45

Fluorspar15-28

Ferromanganese 3-8

Ferrosilicon 1-4

Ferrotitanium 5-15

Ferromolybdenum 1-5

Chrome metal1-5

Iron scale1-12

Cobalt1-10

Cellulose 1-4

Quartz sand 5-10

The disadvantage of this electrode coating is that it, due to the additional introduction of chromium metal and a higher total content of components — ferromanganese, ferrosilicon, silica sand, reduces the decomposition temperature of austenite during the formation of a weld. And this, in turn, reduces the ductility of austenite decomposition products and does not ensure the absence of cracks in the weld metal immediately after welding and after aging of the welded joints.

Thus, the known electrode coatings do not provide high resistance to delayed drying of the joints and long-term strength of the welded joint at temperatures up to 520 ° C.

The purpose of the invention is the creation of a new electrode coating, which would provide resistance to delayed

the destruction of long seams in combination with an increased concentration of welding stresses, as well as the long-term strength of the welded joint at temperatures up to 520 ° C, in particular when operating coke oven chambers made of 16GMYuCh steel.

To achieve this goal, an electrode coating comprising marble, fluorspar, ferromanganese,

ferrosilicon, ferromolybdenum, cobalt, rutile and feldspar were additionally introduced, and powder cobalt was introduced in an amount of 11-18%, ferromolybdenum - 2-3%, while providing a carbon content of two

5 more than 0.06% in the following ratio of components, wt.%:

Marble42-45

Feldspar 2-4

Fluorspar18-25

0 Mica to flour 2-3

Rutile 4-6

Ferrosilicon 7-9

Ferromanganese 3-6

Ferromolybdenum 2-3

5 Cobalt powder 11-18

Marble in the coating acts as a gas-forming and slag-forming component. In less than 42% of the quantities, reliable protection of the melted metal is not provided. An increase in the amount of marble of more than 45% affects the technological properties of the coating.

A content of fluorspar less than 18% does not provide a short

5 of slag, which leads to a deterioration in the shape of the weld and does not have a positive effect on the purity of the weld metal, which is reflected in a decrease in the toughness of the weld metal. When the content of fluorspar is more

0 25%, a flowing slag is formed which does not cover the upper part of the roller, and the separability of the slag crust is deteriorated.

Introduction to the coating of rutile (TI02) helps stabilize the arc in the process

5 welding, reducing spraying of the weld metal. A concentration of rutile of less than 4% does not provide stable arc burning in a wide range of currents; there is a deterioration in weld formation

0 An increase in the amount of rutile by more than 6% affects the physical properties of the slag, in particular its separability, the formation of the weld metal and makes the slag more fluid, which negatively affects 5 s when welding vertical welds.

Feldspar contains alkaline earth elements that reduce the ionization potential of the arc. The introduction of feldspar below the value given in the composition has no practical effect on TRHNP

logical properties of electrodes, the introduction of feldspar of more than 4% leads to a silicon reduction process that increases the silicon content in the weld metal, which reduces its ductility.

The introduction of feldspar and rutile improves the welding and technological properties of the electrodes.

The gas-slag system, consisting of 42-45% marble, 18-25% fluorspar, 4-6% rutile, 2-4% feldspar, provides seams with a finely scaly surface, easy separability of the slag crust, helps to remove gases and non-metallic from the molten metal inclusions.

The content of deoxidizing agents in the coating within the specified range, such as ferrosilicon, allows controlling the level of oxygen in the form of finely divided oxide inclusions in the deposited metal.

Mica on the flour is introduced into the coating to improve the formation of the deposited metal, making it finely scaled with a smooth transition to the welded edge. A content of less than 2% in the coating of mica flour does not improve the formation of the weld metal in the groove. A concentration of mica flour of more than 3% leads to slag porosity and the so-called bruising on the surface of the weld metal.

It was found that when the content of cobalt in the coating is more than 18%, the formation of weld metal rollers with the simultaneous appearance of pores deteriorates sharply, while the resistance to cracking of the weld metal does not increase compared to the proposed cobalt content of 11-18%, and when the content is less than 11 % cobalt does not provide resistance to cracking in welds when welding without heating large lengths of welds and knots of increased rigidity.

The introduction of cobalt, while ensuring a carbon content in the weld of not more than 0.06%, can significantly increase the temperature and the gamma-alpha conversion rate (Table 1) during the formation of the weld and, as a result, produce a deposited metal with high deformation ability without creating tears and cracks.

The molybdenum content in the coating was established on the basis of ensuring the required long-term strength of the weld metal with a guaranteed service life of the welded structure of 10 years at a temperature of 520 ° C. The results of the tests carried out by the authors showed that the optimum content of 6d "in the weld metal should be in the PRDPRP. NC 0 4Ti 0.60%. With the selected components of the proposed electrode coating and their 5% content, the required molybdenum content in the weld metal is ensured by introducing 2-3% FeMo grade MFO - 60 GOST 4759-79 into the coating. Below this limit is not provided long

0 strength at a temperature of 520 ° C. Above 3% FeMo, it is impractical to introduce into the coating because of the cost of electrodes and the deterioration of the technological properties of the weld metal.

5 Effect of molybdenum on temperature and

the completeness of gamma-alpha conversion when its content in the seam is up to 1% is less pronounced, but similar to the effect of cobalt, which is confirmed by the data in Table 1.

A comparative analysis with the prototype allows us to conclude that the claimed composition of the electrode coating differs from the known introduction of new components, namely rutile and field

5 spar and a new ratio of components, for example, powder cobalt, in the amount of 11-18% and molybdenum 2-3%. Thus, the claimed technical solution is new.

An analysis of the known compositions of electrode coatings used in welding without heating low-alloy steels of increased strength showed that some of the substances introduced into the claimed solution are known, for example, cobalt and molybdenum. However, their use in known electrode coating compositions in combination with other components does not provide such properties for coatings.

0 which they exhibit in the claimed solution, namely, crack resistance of the weld metal after long aging of welded joints of increased stiffness with a large length of welds, in particular,

5 coke oven chambers with a diameter of 5000-7000 mm from steel 16GMYUCH. Thus, this composition of the components gives the electrode coating new properties, which allows us to conclude that the claimed

0 solutions to inventive step.

For experimental verification of the claimed composition of the electrode coating, five formulations were prepared, which are listed in Table 2

5

For each option, an experimental batch of electrodes with a diameter of 4 mm was made with coating by crimping with a rod of wire Sv-08A and Sv-08GA.

The electrodes were tested for resistance to cracking in the weld metal under conditions that maximally simulate the welding of coke oven chambers at the installation according to the procedure in accordance with GOST 26389-84. The test results on samples of steel 16GMYUCH 30 mm thick are given in table.3.

Based on the requirements of the industry standard OST 26-291-87, which allows welding of steel vessels and apparatuses under mounting conditions at positive temperatures and the results of comparative tests on racks, cracking in the weld performed by new and used UONII 13/55 and TML electrodes -IV, it is clear that only new electrodes with a coating content of 12% Co and 18% Co on the Sv-08A wire allow, without heating during welding, to provide welds without cracks with mechanical properties not lower than the steel being welded: the limit accuracy not less than 550 MPa, yield strength not less

5

400 MPa, impact strength at test temperatures of 50 ° C, at least 30 J / cm.

The manufacture of electrodes with the proposed coating in comparison with the known does not require a change in existing technology.

Claims (1)

SUMMARY OF THE INVENTION An electrode coating composition comprising marble, fluorspar, ferromanganese, ferrosilicon, cobalt, ferromolybdenum, characterized in that it further comprises rutile, feldspar and mica flour in the following ratio, wt.%: 0 5 marble fluorspar feldspar mica on rutile flour ferrosilicon ferromanganese ferromolybdenum cobalt 42-45 18-25 2-4 2-3 4-6 7-9 3-6 2-3 11-18. Table 1 The effect of cobalt and molybdenum content on the change in the rate and temperature of gamma-alpha conversion of iron from 0.04% C The results of comparative tests of epectrodes for resistance to cracking in the weld of samples of steel 16GMYUCH with a thickness of 30 mm T l f p i c a 2 Table 3 Continuation of the table.