RU2443530C1 - Welding wire for welding and building-up of parts from diverse steels - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to welding, particularly, to composition of welding wire for welding and building up of articles operated at high alternating-sign loads and temperatures and may be used in building up of the first layer of carbon and low-alloyed steel edges for making welded joints with austenitic steels, mainly, on producing welded structures for nuclear power engineering. Proposed wire comprises carbon, silicon, manganese, phosphorus, sulfur, copper, nickel, cobalt, niobium, nitrogen, tin, antimony and iron in the following ratio, in wt %: carbon - 0.012-0.02, silicon - 0.45-0.65, manganese - 1.0-2.0, chromium - 23.0-25.0, nickel - 12.0-14.0, niobium - 0.45-0.6, sulfur - not over 0.02, phosphorus - not over 0.015, copper - not over 0.1, tin - not over 0.005, antimony - not over 0.005, cobalt 0 not over 0.05, nitrogen - not over 0.05, iron making the rest. Proposed wire allows obtaining two-phase austenitic-ferrite structure of build-up metal with content of ferrite phase making 5-10%.

EFFECT: optimum physical and mechanical properties of welded joint metal.

Description

The invention relates to welding and the composition of the welding wire for welding and surfacing of products operating at high alternating loads and elevated temperatures, and can be used for surfacing the first layer of the edges of carbon and low alloy steels when performing dissimilar welded joints with austenitic class steels, mainly, when manufacturing of welded structures of nuclear and power engineering.

The known composition of the welding wire containing carbon, chromium, silicon, manganese, molybdenum, vanadium, sulfur, phosphorus, iron, which introduced calcium in the following ratio, wt.%:

Carbon 0.06-0.10 Chromium 0.9-1.2 Silicon 0.4-0.7 Manganese 1.55-1.8 Molybdenum 0.5-0.7 Vanadium 0.2-0.45 Sulfur 0,025-0,04 Phosphorus 0.025-0.030 Calcium 0.05-0.2 Iron - the rest,

the ratio of carbon content to the total content of molybdenum and vanadium should be 0.066-0.087, and the ratio of sulfur to the total content of calcium and manganese should be in the range of 0.015-0.020 (see, for example, the description of the invention to RF patent No. 2104138, cl. B23K 35/30, publ. 1998).

The disadvantages of this composition include unstable flickering arc burning, as well as the possibility of the formation of hot cracks and the comparative fragility of the weld.

The closest known for its technical essence and the achieved result is a welding wire selected for the prototype for welding and surfacing of parts from dissimilar steels containing carbon, silicon, manganese, phosphorus, sulfur, chromium, nickel, molybdenum, cobalt, niobium, nitrogen and iron (see, for example, STAINLESS WELDING CONSUMABLES prospectus, SANDVIK24 / 13 / LHF (AWS309L), 1981, p. 27).

The disadvantages of this composition include the high content of the ferrite phase (more than 15%), which contributes to embrittlement of the deposited metal during heat treatment and during operation at elevated temperatures, as well as the lack of regulation of the content of sulfur, phosphorus, tin, antimony, copper impurities at the required level that does not guarantee resistance to the formation of hot cracks in the metal of the first layer of surfacing adjacent to the line of alloying with carbon or low alloy steel, in conditions of alloying niobium and insufficient content of the ferrite phase.

The essence of the claimed invention is expressed in the aggregate of essential features sufficient to achieve the technical result provided by the invention, which is expressed in obtaining optimal physical and mechanical properties of the weld metal when performing welded joints of dissimilar steels and resistance to intergranular corrosion, which is ensured by the chemical composition of the welding wire, chemical the composition of the weld metal and the ratio of chromium, nickel, niobium, carbon and nitrogen, regulations tiruyuschih content of the ferrite phase in the weld metal, specify the ratio of niobium to carbon and prevent the formation of martensite structure in the deposited weld metal.

The specified technical result is achieved in that the welding wire for welding and surfacing of parts from dissimilar steels, containing carbon, silicon, manganese, phosphorus, sulfur, chromium, nickel, molybdenum, cobalt, niobium, nitrogen and iron, additionally contains tin and antimony, carbon, nitrogen, nickel, manganese are combined in the austenite-forming group of elements, and silicon, chromium and niobium are included in the ferrite-forming group of elements in the following ratio of components, wt.%:

Carbon 0.012-0.02 Silicon 0.45-0.65 Manganese 1.0-2.0 Chromium 23-25 Nickel 12-14 Niobium 0.45-0.6 Sulfur no more than 0,01 Phosphorus no more than 0.015 Copper no more than 0.1 Tin no more than 0,005 Antimony no more than 0,005 Cobalt no more than 0,05 Nitrogen no more than 0,05 Iron rest,

this should be ensured by the ratio of austenito and ferrite-forming elements:

14≤Ni _E ≤16

24≤Cr _E ≤26

Ni _E ≥Cr _E -10

Ni _E =% Ni + 30% C + 0.5% Mn;

Cr _e =% Cr + 1.5% Si + 0.5% Nb

The specified ratio of austenitic (carbon, nitrogen, nickel, manganese) and ferrite-forming (silicon, chromium, niobium) elements allows to obtain a two-phase austenitic-ferritic structure of the deposited metal with a regulated content of ferrite phase in the range of 5-10%.

The lower limit of the content of the ferritic phase provides resistance to the formation of hot cracks.

The upper limit of the content of the ferritic phase is set to prevent embrittlement of the deposited metal during heat treatment and during operation at elevated temperatures.

The carbon content of 0.012-0.02% ensures the formation in the metal of the first layer of surfacing adjacent to the line of fusion with carbon or low alloy steel, a plastic structure without a martensitic component, which provides resistance to the formation of cold cracks.

The introduction of niobium at a ratio of Nb / C = 22-30 in the composition of the welding wire provides resistance to intergranular corrosion of the deposited metal, including after heat treatment (high tempering). It also provides resistance to intergranular corrosion of the metal of the first surfacing layer adjacent to the line of alloying with carbon or low alloy steel, under conditions of a decrease in the Nb / C ratio relative to that indicated due to dilution of the surfacing metal with the base metal.

The low content of sulfur, phosphorus, tin, antimony, copper prevents the segregation of impurities and a decrease in strength along the grain boundaries. This provides resistance to the formation of hot cracks in the metal of the first surfacing layer adjacent to the line of alloying with carbon or low alloy steel, in conditions of insufficient content of the ferritic phase, which is possible as a result of a decrease in its amount relative to the calculated one due to dilution of the surfacing metal with the base metal.

The limitation of the cobalt content prevents the radioactive contamination of parts with surfacing in contact with the radioactive medium.

The wire provides increased resistance against the formation of cold and hot cracks in the weld metal of variable composition in the fusion zone of a heterogeneous compound, resistance to the formation of hot cracks in the austenitic welded metal and resistance to intergranular corrosion in contact with a corrosive medium.

In production conditions, batches of welding wire Sv-02X24N13B were made.

Forgings of steel grade 15X2NMFAA were used as the main metal.

Surfacing was carried out by argon-arc welding with a welding wire of the following composition:

Carbon 0.014 Silicon 0.48 Manganese 1.36 Chromium 23.17 Nickel 13.29 Niobium 0.5 Sulfur 0.007 Phosphorus 0.01 Copper 0,03 Tin 0,0005 Antimony 0.001 Cobalt 0.02 Nitrogen 0.04 Iron rest.

The thickness of the deposited layer was from 4 to 5.5 mm.

Welded welded joints were examined in the state after welding and in the state after high tempering at 650 ° C for 10 hours.

Metallographic studies were performed on the following compound zones:

- 1 layer of deposited metal with a thickness of 0.5-1.0 mm, adjacent to the fusion line;

- deposited metal of subsequent layers.

Metallographic studies showed:

The first layer in the state after welding does not contain traces of quenching structures and has a low hardness (Nµ). Cold cracks were not identified.

The chemical composition has changed in comparison with the initial composition of the welding wire, while the content of the ferrite phase has decreased. At the same time, discontinuities having the character of crystallization cracks, microcracks and tears were not revealed.

The subsequent layers of the deposited metal have a two-phase austenitic-ferritic structure with a ferrite content of up to 9%. There are no discontinuities like hot cracks.

In the state after high tempering, the required quality of the deposited metal over the entire thickness is ensured.

The metal of the 1st layer of surfacing and the metal of subsequent layers were tested for resistance to intergranular corrosion when testing samples in a solution of sulfuric acid according to the AMU method, GOST 6032-2003. Samples were subjected to high tempering at a temperature of 650 ° C for 10 hours. A tendency to intergranular corrosion has not been identified.

The application of the invention provides a combination of increased optimal values of strength, ductility, resistance to brittle fracture due to the exclusion of intergranular corrosion when performing welded joints of dissimilar steels.

Claims (1)

Welding wire for welding and surfacing parts from dissimilar steels containing carbon, silicon, manganese, phosphorus, sulfur, chromium, nickel, copper, cobalt, niobium, nitrogen and iron, characterized in that it additionally contains tin and antimony, while carbon , nitrogen, nickel, manganese are combined in an austenite-forming group of elements, and silicon, chromium and niobium are included in a ferrite-forming group of elements in the following ratio of components, wt.%:
carbon 0.012-0.02 silicon 0.45-0.65 manganese 1.0-2.0 chromium 23.0-25.0 nickel 12.0-14.0 niobium 0.45-0.6 sulfur no more than 0,01 phosphorus no more than 0.015 copper no more than 0.1 tin no more than 0,005 antimony no more than 0,005 cobalt no more than 0,05 nitrogen no more than 0,05 iron rest,
however, it provides a two-phase austenitic-ferritic structure of the weld metal with a ferrite phase content of 5-10%.