Method for depositing a cladding material onto a metal surface by electroslag strip surfacing

Abstract

In a method for depositing a cladding material onto a metal surface by means of electroslag strip surfacing, use is made of welding strips made of austenitic stainless steel, such as 308L or 309L alloy, and a flux material having the following composition: - Al203: 20-30 wt% - CaF2: 55-70 wt% - Mo: 0.3-3 wt% - Nb: 1.2-2.5 wt% - Cr: 3-6 wt% - Mn: 1-3.5 wt% - Na2Si03: 1-6 wt% and optionally other components, in particular: - MgO: < 1 wt% - CaO.Al203: < 1 wt% - Carbonates: < 1 wt% and unavoidable impurities.

Description

[0001] This invention relates to a method for depositing a coating material onto a metal surface using electroslag strip welding.

[0002] In nuclear power applications and in the upstream and downstream oil and gas industries, weld overlays are deposited on the walls of reactor vessels and vessel assemblies to protect them from corrosion, high temperatures, and / or chemical embrittlement. The reactor vessel is the most critical structural component for nuclear power plant safety. A nuclear reactor vessel is a cylindrical assembly constructed using low-alloy steel, clad in austenitic stainless steel to prevent corrosion processes. Corrosion is often the cause of cracking or deformation. Therefore, the advantage of austenitic stainless steel is its high corrosion resistance. Cladding materials are susceptible to thermal cracking and stress corrosion cracking. Cracks in the cladding can lead to catastrophic failures.

[0003] Overlay welding methods typically use strip electrodes to create an overlay layer on a metal surface. The two most common methods used for overlaying large components are submerged arc strip cladding and electroslag strip cladding.

[0004] In electroslag strip welding, the strip electrode is continuously fed into a shallow layer of conductive flux. The heat required for the surface layer of the molten strip, slag-forming flux, and base metal is generated by resistance heating produced by the welding current flowing through the molten conductive slag. The heat generated in this process is sufficient to stabilize the process and melt the strip into the liquid slag, thereby transferring the strip to the molten metal deposited on the base metal.

[0005] Electroslag strip welding is characterized by high deposition rates and low dilution. The degree of dilution, in particular, determines the amount of iron diluted from the base metal into the deposited cladding.

[0006] However, in nuclear power applications, only the less efficient submerged arc strip electrode welding method is currently used.

[0007] The metallographic composition of the welding strip electrode greatly determines the quality of the resulting cladding in terms of corrosion resistance, temperature resistance, and chemical resistance. Common alloys used for welding strip electrodes in nuclear power applications are the so-called 308L and 309L alloys. The composition of the 308L alloy is defined in AWS A5.9 / A5.9M:2017 and is as follows:

[0008] C≤0.03% by weight

[0009] Mn 1.0-2.5% by weight

[0010] Si 0.30-0.65% by weight

[0011] Cr 19.5-22.0% by weight

[0012] Ni 9.0-11.0% by weight

[0013] Mo ≤ 0.75% by weight

[0014] S≤0.03% by weight

[0015] P ≤ 0.03% by weight

[0016] Cu ≤ 0.75% by weight

[0017] N≤0.10% by weight

[0018] The balance consists of unavoidable impurities and Fe.

[0019] The composition of 309L alloy is defined in AWS A5.9 / A5.9M:2017 and is as follows:

[0020] C≤0.03% by weight

[0021] Mn 1.0-2.5% by weight

[0022] Si 0.30-0.65% by weight

[0023] Cr 23.0-25.0% by weight

[0024] Ni 12.0-14.0% by weight

[0025] Mo ≤ 0.75% by weight

[0026] S≤0.03% by weight

[0027] P ≤ 0.03% by weight

[0028] Cu ≤ 0.75% by weight

[0029] N≤0.10% by weight

[0030] The balance consists of unavoidable impurities and Fe.

[0031] 308L and 309L alloy welding strips are sold in different variations and under various trademarks, such as those from voestalpine. Welding's Soudotape 308L and Soudotape 309L.

[0032] Compared to submerged arc welding (SAW), electroslag strip welding offers a superior welding process with increased productivity. However, currently, there are no suitable flux materials that meet the technical requirements for nuclear applications for depositing 308L or 309L alloys using SAW. In particular, current strip-flux combinations cannot ensure an ultimate tensile strength of 520 MPa while maintaining the ferrite content of the cladding material at around 15 FN (FN = ferrite number). Only submerged arc welding (SAW) solutions can currently meet this requirement.

[0033] Manufacturers of structural components for nuclear power plants are reluctant to switch to different welding consumables because product certification is a cumbersome process, and changing products always involves some risk. This is especially true when it comes to changing welding processes.

[0034] Therefore, one object of the present invention is to provide an improved method for depositing a cladding material onto a metal surface by electroslag strip welding using a weld strip electrode made of austenitic stainless steel, such as alloy 308L or 309L. In particular, one object of the present invention is to provide a method wherein the cladding material has an ultimate tensile strength (UTS) higher than 520 MPa and a ferrite content lower than 17 FN.

[0035] To achieve at least some of the above objectives, the present invention generally provides a method for depositing a cladding material onto a metal surface using electroslag strip welding, wherein the method comprises using a welding strip made of austenitic stainless steel, such as an alloy of 308L or 309L, and a flux material having the following composition:

[0036] -Al2O3: 20-30% by weight

[0037] -CaF2: 55-70% by weight

[0038] -Mo: 0.3-3% by weight

[0039] -Nb: 1.2-2.5% by weight

[0040] -Cr: 3-6% by weight

[0041] -Mn: 1-3.5% by weight

[0042] -Na2SiO3: 1-6 wt%

[0043] And other optional ingredients, especially:

[0044] MgO: <1% by weight

[0045] CaO.Al2O3: <1% by weight

[0046] Carbonates: <1% by weight

[0047] And unavoidable impurities.

[0048] This invention provides a specific mixture of alloying elements for flux materials, falling within the permissible range of the 308LAWS standard to ensure the desired properties of the coating material in terms of ultimate tensile strength and ferrite number. Al₂O₃ and CaF₂ are provided in the flux material as slag-forming agents. Mo acts as a ferrite promoter to improve pitting corrosion resistance. Nb improves intergranular resistance and acts as an alloying strengthener. Cr acts as a ferrite promoter and improves corrosion resistance. Mn reduces hot cracking susceptibility and improves tensile strength. Na₂SiO₃ acts as a binder.

[0049] Furthermore, the electroslag strip welding process can achieve exceptionally high deposition rates, particularly by about 20% compared to known submerged arc strip welding processes.

[0050] According to a preferred embodiment, two cladding material layers are deposited onto a metal surface, each using an electroslag strip welding process. This dual-layer technique is characterized by depositing a first cladding layer onto the metal surface, followed by depositing a second cladding layer onto the first layer in a separate electroslag strip welding process. Applying two layers is beneficial for achieving a sufficient total thickness of the cladding material. In the electroslag strip welding process, the first cladding layer will have a relatively low ferrite number, while the second layer will have a higher ferrite number. Therefore, applying the second layer, forming the outer surface of the cladding material, is beneficial for maintaining the ferrite number within a preferred range of 13-17 FN.

[0051] In any case, a preferred embodiment proposes that the second layer of cladding material deposit has a ferrite content of <17FN, preferably <15FN (measured on its top surface). Preferably, the cladding material deposit has a ferrite content of 13-17FN, particularly 13-15FN.

[0052] Within the scope of this invention, the ferrite number was measured according to AWS A4.2 using a Fischer Ferrite-scope FMP 30.

[0053] Preferably, the first and / or second layer of coating material deposits has an ultimate tensile strength >520 MPa, as measured in the Embodiments section of this application (eight layers of weld metal deposits are deposited onto a steel plate surface to construct a metal block, and the block is then machined into a specimen). Ultimate tensile strength (UTS) is the maximum stress a material can withstand before fracture when stretched or pulled. Ultimate tensile strength (Rm) is measured according to AWS B.4 standards. This invention uses a flux material with a high proportion of Mn and Nb, as described in claim 1 of this invention, along with the remaining components, to achieve a coating material tensile strength >520 MPa. Mn is an element that improves resistance to hot cracking. It reduces the free sulfur content in the alloy matrix of the coating material of this invention, which can induce hot cracking. Reducing hot cracking susceptibility helps achieve a tensile strength of 520 MPa by reducing “micro-hot cracks” in the alloy that will initiate cracking and ultimately lead to alloy fracture.

[0054] In a preferred embodiment of the present invention, the flux material has the following composition:

[0055] -Al2O3: 22-25% by weight

[0056] -CaF2: 58-68% by weight

[0057] -Mo: 0.5-2% by weight

[0058] -Nb: 1.5-2.3% by weight

[0059] -Cr: 3-5% by weight

[0060] -Mn: 1.2-3% by weight

[0061] -Na2SiO3: 2-6 wt%

[0062] And other optional ingredients, especially:

[0063] -MgO: <1% by weight

[0064] -CaO.Al2O3: <1% by weight

[0065] - Carbonates: <1% by weight

[0066] And unavoidable impurities.

[0067] In a particularly preferred embodiment of the invention, the flux material has the following composition:

[0068] -Al2O3: 23-24% by weight

[0069] -CaF2: 60-65% by weight

[0070] -Mo: 0.8-1.5% by weight

[0071] -Nb: 1.8-2.2% by weight

[0072] -Cr: 3.4-4.5% by weight

[0073] -Mn: 1.2-2.5% by weight

[0074] -Na2SiO3: 4-6 wt%

[0075] And other optional ingredients, especially:

[0076] -MgO: <1% by weight

[0077] -CaO.Al2O3: <1% by weight

[0078] - Carbonates: <1% by weight

[0079] And unavoidable impurities.

[0080] Specifically, the flux material may have the following composition:

[0081] -Al2O3: 24 wt%

[0082] -CaF2: 62% by weight

[0083] -Mo: 1% by weight

[0084] -Nb: 2% by weight

[0085] -Cr: 4% by weight

[0086] -Mn: 2% by weight

[0087] -Na2SiO3: 5% by weight

[0088] And other optional ingredients, especially:

[0089] -MgO: <1% by weight

[0090] -CaO.Al2O3: <1% by weight

[0091] - Carbonates: <1% by weight

[0092] And unavoidable impurities.

[0093] As described above, the flux material of the present invention is developed for combination with a welding strip electrode made of austenitic stainless steel. Specifically, the welding strip electrode has the following composition:

[0094] C≤0.03% by weight

[0095] Mn 1.0-2.5% by weight

[0096] Si 0.30-0.65% by weight

[0097] Cr 19.5-25.0% by weight

[0098] Ni 9.0-14.0% by weight

[0099] And other optional ingredients, especially:

[0100] Mo ≤ 0.75% by weight

[0101] S≤0.03% by weight

[0102] P ≤ 0.03% by weight

[0103] Cu ≤ 0.75% by weight

[0104] N≤0.10

[0105] And unavoidable impurities, with the remainder being iron.

[0106] In a preferred embodiment, the welding strip electrode has the following composition:

[0107] C 0.012-0.015% by weight

[0108] Mn 1.65-1.75% by weight

[0109] Si 0.38-0.42% by weight

[0110] Cr 20-25% by weight

[0111] Ni 10-15% by weight

[0112] And other optional ingredients, especially:

[0113] Mo 0.01-0.15% by weight

[0114] S 0.0005-0.003% by weight

[0115] P 0.012-0.020 wt%

[0116] Cu 0.02-0.04% by weight

[0117] N 0.045-0.60% by weight

[0118] And unavoidable impurities, with the remainder being iron.

[0119] The welding strips falling within the aforementioned range are made of voestalpine Welding Belgium sa sells under the trademarks SOUDOTAPE 308L and SOUDOTAPE 309L.

[0120] According to a preferred embodiment, a first layer of coating material is deposited using a 309L welding strip electrode, and a second layer of coating material is deposited onto the first layer using a 308L welding strip electrode.

[0121] Preferably, electroslag strip welding includes:

[0122] -Provide welding strip electrodes,

[0123] -Provide flux materials,

[0124] - Position the welding electrode at a certain distance above the welding area on the metal surface.

[0125] - Apply a layer of flux material to the metal surface in the welding area.

[0126] - Apply welding current to the welding strip electrode, thereby melting the flux material, the strip electrode, and the metal surface.

[0127] - While the welding electrode advances above the metal surface, it is continuously fed into a layer of molten flux material to create a coating material deposit on the metal surface along the advance path.

[0128] It is known that the welding parameters selected for electroslag strip welding, such as welding current, welding voltage, welding speed, and stick-out, affect the penetration thickness (the thickness of the molten base metal layer) and the deposition thickness. In a preferred embodiment of the invention, the welding parameters are optimized to maintain the correct ratio between penetration thickness and deposition thickness, and also to allow sufficient time for element transfer between the weld pool and the molten slag. Therefore, the electroslag strip welding may include applying a welding current of 400-1800 A, preferably 1200-1300 A, and a welding voltage of 22-26 V, particularly 23-25 ​​V.

[0129] The welding current can be preferably selected to suit the width of the welding electrode. According to a preferred embodiment, a welding electrode with a width of 10-90 mm, preferably 60 mm, is used. In order to adjust the welding current according to the bandwidth, this adjustment is advantageously carried out to select a ratio of welding current [A] to electrode bandwidth [mm] of 18-22, preferably 20.

[0130] Furthermore, the electroslag strip welding advantageously includes positioning the welding strip at a certain distance above the welding area on the metal surface, so that the stick out is 28-42 mm, preferably 29-40 mm.

[0131] In addition, the welding speed is preferably selected as 16-24 cm / min, and more preferably 18-22 cm / min.

[0132] It is known that the strip feed nozzle plays a crucial role in the strip welding process. This nozzle guides the welding strip, ensures a uniform distribution of welding current across the entire width of the strip, and must be able to withstand heat and dissipate heat effectively to avoid overheating during continuous operation.

[0133] According to a preferred embodiment of the invention, the strip feed nozzle is mounted to be pivotable relative to the metal surface. Depending on the curvature of the substrate material, it is advantageous to provide an angle for the weld strip by using a pivoting nozzle. This allows control of the angle between the strip and the surface to be coated. Therefore, a preferred embodiment proposes that the electroslag strip welding includes maintaining the strip feed nozzle such that the weld strip is arranged at a maximum angle of ±25° relative to the perpendicular to the metal surface.

[0134] According to a further aspect, the present invention relates to a flux material used in a method of depositing a cladding material onto a metal surface by means of electroslag strip welding, said flux material having the following composition:

[0135] -Al2O3: 20-30% by weight

[0136] -CaF2: 55-70% by weight

[0137] -Mo: 0.3-3% by weight

[0138] -Nb: 1.2-2.5% by weight

[0139] -Cr: 3-6% by weight

[0140] -Mn: 1-3.5% by weight

[0141] -Na2SiO3: 1-6 wt%

[0142] And other optional ingredients, especially:

[0143] -MgO: <1% by weight

[0144] -CaO.Al2O3: <1% by weight

[0145] - Carbonates: <1% by weight

[0146] And unavoidable impurities.

[0147] According to a further aspect, the present invention relates to a kit for use in a method of depositing a cladding material onto a metal surface by means of electroslag strip welding, comprising the flux material of the present invention and a welding strip electrode, wherein the welding strip electrode is made of austenitic stainless steel, such as 308L or 309L alloy.

[0148] According to another aspect of the invention, an article, such as a plate, container or pipe, is provided, comprising a metal surface and at least two layers of cladding material deposited on the metal surface by means of a welding process, wherein the second cladding material layer has a ferrite content of <17FN, preferably <15FN (measured on its top surface).

[0149] Preferably, the covering material has the following composition on its top surface:

[0150] C 0.022-0.025% by weight

[0151] Mn 2.35-2.45% by weight

[0152] Si 0.45-0.50% by weight

[0153] Cr 18-21% by weight

[0154] Ni 9.5-11% by weight

[0155] Mo 0.35-0.40% by weight

[0156] Nb 0.4-0.5% by weight

[0157] And other optional ingredients, especially:

[0158] S < 0.0005% by weight

[0159] P 0.014-0.018 wt%

[0160] Cu 0.03-0.07% by weight

[0161] N 0.045-0.55% by weight

[0162] And unavoidable impurities, with the remainder being iron.

[0163] The invention will now be explained in more detail through exemplary embodiments.

[0164] A flat carbon steel sheet (0.2 wt% C; thickness: 30 mm) is used as the base metal. The metal surface of this steel sheet is covered with two overlapping layers of cladding material by a welding process. Electroslag strip welding is used as the welding process. In electroslag strip welding, consumables (welding strip and flux material) are melted by resistance heating. Heating is provided by current transmitted to the molten pool via conductive flux, which, after melting, participates in the melting of the strip and generates slag. In this process, flux is introduced through a flux tube positioned in front of the cladding nozzle and fed to the strip via a feed roller.

[0165] Use, such as voestalpine Welding Belgium sa sells two types of welding strip electrodes under the trademarks SOUDOTAPE 309L and SOUDOTAPE 308L, which have the following composition:

[0166] SOUDOTAPE 309L:

[0167] C 0.013% by weight

[0168] Mn 1.69% by weight

[0169] Si 0.40% by weight

[0170] S 0.001% by weight

[0171] P 0.016% by weight

[0172] Cr 23.7% by weight

[0173] Ni 13.60% by weight

[0174] Mo 0.10% by weight

[0175] Cu 0.03% by weight

[0176] N 0.055% by weight

[0177] The balance is Fe.

[0178] SOUDOTAPE 308L:

[0179] C 0.014% by weight

[0180] Mn 1.71% by weight

[0181] Si 0.40% by weight

[0182] S 0.002% by weight

[0183] P 0.012 wt%

[0184] Cr 20.4% by weight

[0185] Ni 10.3% by weight

[0186] Mo 0.02% by weight

[0187] Cu 0.03% by weight

[0188] N 0.048% by weight

[0189] The balance is Fe.

[0190] The strip has a width of 60 mm and a thickness of 0.5 mm.

[0191] In addition, a powdered flux material is used, which has the following composition:

[0192] Al2O3 24 wt%

[0193] CaF2 62% by weight

[0194] CaO.Al₂O₄ 9.5% by weight

[0195] Cr 4% by weight

[0196] Mo 1% by weight

[0197] Nb 2% by weight

[0198] Mn 2% by weight

[0199] Na2O.SiO2 5 wt%

[0200] Use the following welding parameters:

[0201] Welding current: 1250A

[0202] Welding voltage: 24V

[0203] Welding speed: 20cm / min

[0204] Elongation: 30mm

[0205] Three side-by-side overlay weld beads are deposited on the surface of the steel plate using SOUDOTAPE 309L and flux material to form the first layer. Two side-by-side overlay weld beads are then deposited using SOUDOTAPE 308L and flux material deposited on the first layer to form the second layer.

[0206] The resulting weld strip cladding was subjected to multiple analytical procedures, such as lateral bending test (according to AWS B4.0), ultrasonic observation (according to ASME), ferrite content (using feritscope FMP30), and surface chemical measurement on the top surface (by atomic emission spectrometry) to examine the quality of the deposit.

[0207] The test results were positive; the surface was continuous and without any defects. Chemical analysis and ferrite content of the obtained deposits, compared to the requirements specified in AWS A5.4 / A5.4M:2012, showed the following results:

[0208]

[0209] * Ferrite number calculated based on WRC92 diagram

[0210] Ferrite number measured using Ferrite-scope FMP 30 according to AWS A4.2

[0211] In addition, eight SOUDOTAPE 309L layers were deposited on the surface of a steel plate using the flux material to construct a metal block. A 309L tensile specimen was then machined from this metal block.

[0212] Similarly, eight SOUDOTAPE 308L layers were deposited on the surface of a steel plate using the same flux material to construct a metal block. A 308L tensile specimen was then machined from this metal block.

[0213] Tensile tests were performed on the specimens according to AWS B4.0 standard, and the following results were obtained:

[0214] Rp0.2 [MPa] Rm[MPa] A(4d)[%] Sample 309L 364 556 47 Sample 308L 346 555 52

[0215] Therefore, the content of all chemical elements in the second layer falls within the limits specified in AWS A5.4 / A5.4M:2012.

[0216] In addition, the tensile strength of the 309L & 308L specimens is higher than 520 MPa, and the Δ ferrite content of the second layer is lower than 17FN, which is a common requirement for nuclear manufacturers.

Claims

1. A method for depositing a cladding material onto a metal surface using electroslag strip welding, wherein the electroslag strip welding comprises using a welding strip made of austenitic stainless steel and a flux material having the following composition: - Al2O3: 20-30% by weight - CaF2: 55-70% by weight - Mo: 0.3-3% by weight - Nb: 1.2-2.5% by weight - Cr: 3-6% by weight - Mn: 1-3.5% by weight - Na2SiO3: 1-6 wt% And other optional ingredients and unavoidable impurities, Electroslag strip welding includes: - Provide the aforementioned welding strip electrode, - Provide the flux material, - Position the welding strip electrode at a certain distance above the welding area on the metal surface. - Apply a layer of flux material to the metal surface in the welding area. - A welding current is applied to the welding strip electrode, thereby melting the flux material, the strip electrode, and the metal surface. - As the welding electrode advances above the metal surface, it is continuously fed into a layer of molten flux material to create a coating material deposit on the metal surface along the advance path.

2. The method according to claim 1, wherein the austenitic stainless steel is 308L or 309L alloy.

3. The method of claim 1, wherein two coating material layers are deposited onto the metal surface.

4. The method of claim 3, wherein the second overlay material deposit has a ferrite content of <17 FN measured on its top surface, wherein the ferrite number (FN) is measured according to AWS A4.2 using a Fischer Ferrite-scope FMP 30.

5. The method of claim 4, wherein the second coating material deposit has a ferrite content of <15 FN measured on its top surface.

6. The method according to claim 1, wherein the flux material has the following composition: - Al2O3: 22-25% by weight - CaF2: 58-68% by weight - Mo: 0.5-2% by weight - Nb: 1.5-2.3% by weight - Cr: 3-5% by weight - Mn: 1.2-3% by weight - Na2SiO3: 2-6 wt% And other optional ingredients and unavoidable impurities.

7. The method according to claim 6, wherein the flux material has the following composition: - Al2O3: 23-24% by weight - CaF2: 60-65% by weight - Mo: 0.8-1.5% by weight - Nb: 1.8-2.2% by weight - Cr: 3.4-4.5% by weight - Mn: 1.2-2.5% by weight - Na2SiO3: 4-6 wt% And other optional ingredients and unavoidable impurities.

8. The method according to claim 7, wherein the flux material has the following composition: - Al2O3: 24% by weight - CaF2: 62% by weight - Mo: 1% by weight - Nb: 2% by weight - Cr: 4% by weight - Mn: 2% by weight - Na2SiO3: 5% by weight And other optional ingredients and unavoidable impurities.

9. The method according to claim 8, wherein the other components of the flux material include: - MgO: < 1% by weight - CaO•Al2O3: < 1% by weight - Carbonates: < 1 wt%.

10. The method according to claim 1, wherein the welding strip electrode has the following composition: C 0.012-0.015% by weight Mn 1.65-1.75% by weight Si 0.38-0.42% by weight Cr 20-25% by weight Ni 10-15% by weight Mo 0.01-0.15% by weight And other optional ingredients and unavoidable impurities, with the balance being iron.

11. The method of claim 10, wherein the other components in the weld strip electrode include: S 0.0005-0.003% by weight P 0.012-0.020 wt% Nb 0.01% by weight Cu 0.02-0.04% by weight N 0.045-0.60 by weight.

12. The method according to claim 1, wherein the electroslag strip welding comprises applying a welding current of 400-1800 A and a welding voltage of 22-26 V.

13. The method of claim 12, wherein the electroslag strip welding comprises applying a welding current of 1200-1300 A and a welding voltage of 23-25 ​​V.

14. The method according to any one of claims 1-13, wherein a welding speed of 16-24 cm / min is used.

15. The method of claim 14, wherein a welding speed of 18-22 cm / min is used.

16. A flux material used in a method of depositing a cladding material onto a metal surface by means of electroslag strip welding, said flux material having the following composition: - Al2O3: 20-30% by weight - CaF2: 55-70% by weight - Mo: 0.3-3% by weight - Nb: 1.2-2.5% by weight - Cr: 3-6% by weight - Mn: 1-3.5% by weight - Na2SiO3: 1-6 wt% And other optional ingredients and unavoidable impurities.

17. The flux material according to claim 16, wherein the flux material has the following composition: - Al2O3: 23-24% by weight - CaF2: 60-65% by weight - Mo: 0.8-1.5% by weight - Nb: 1.8-2.2% by weight - Cr: 3.4-4.5% by weight - Mn: 1.2-2.5% by weight - Na2SiO3: 4-6 wt% And other optional ingredients and unavoidable impurities.

18. The flux material according to claim 16 or 17, wherein the flux material has the following composition: - Al2O3: 24% by weight - CaF2: 62% by weight - Mo: 1% by weight - Nb: 2% by weight - Cr: 4% by weight - Mn: 2% by weight - Na2SiO3: 5% by weight And other optional ingredients and unavoidable impurities.

19. The flux material according to claim 18, wherein the other components of the flux material include: - MgO: < 1% by weight - CaO•Al2O3: < 1% by weight - Carbonates: < 1 wt%.

20. A kit used in a method of depositing a cladding material onto a metal surface by means of electroslag strip welding, comprising a flux material and a welding strip electrode according to any one of claims 16-19, wherein the welding strip electrode is made of austenitic stainless steel.

21. The kit of claim 20, wherein the austenitic stainless steel is 308L or 309L alloy.

22. The kit of claim 20, wherein the welding strip electrode has the following composition: C ≤ 0.03% by weight Mn 1.0-2.5% by weight Si 0.30-0.65% by weight Cr 19.5-25.0% by weight Ni 9.0-14.0% by weight And other optional ingredients and unavoidable impurities, with the balance being iron.

23. The kit of claim 22, wherein the other components in the weld strip electrode include: Mo ≤ 0.75% by weight S ≤ 0.03% by weight P ≤ 0.03% by weight Cu ≤ 0.75% by weight N ≤ 0.10% by weight.

24. The kit of claim 20, wherein the welding strip electrode has the following composition: C 0.012-0.015% by weight Mn 1.65-1.75% by weight Si 0.38-0.42% by weight Cr 20-25% by weight Ni 10-15% by weight And other optional ingredients and unavoidable impurities, with the balance being iron.

25. The kit of claim 24, wherein the other components in the weld strip electrode include: Mo 0.01-0.15% by weight S 0.0005-0.003% by weight P 0.012-0.020 wt% Cu 0.02-0.04% by weight N 0.045-0.60 by weight.

26. An article comprising a metal surface and at least two overlay material layers deposited on the metal surface by the method according to any one of claims 1-15, wherein the second overlay material layer has a ferrite content of < 17 FN measured on its top surface.

27. The article of claim 26, wherein the article is a plate, container or pipe.

28. The article of claim 26, wherein the second covering material layer has a ferrite content of <15 FN measured on its top surface.

29. The article of any one of claims 26-28, wherein the covering material has the following composition on its top surface: C 0.022-0.025% by weight Mn 2.35-2.45% by weight Si 0.45-0.50% by weight Cr 18-21% by weight Ni 9.5-11% by weight Mo 0.35-0.40% by weight Nb 0.4-0.5% by weight And other optional ingredients and unavoidable impurities, with the balance being iron.

30. The article of claim 29, wherein the other components further comprise: S < 0.0005% by weight P 0.014-0.018 wt% Cu 0.03-0.07% by weight N 0.045-0.55% by weight.

Images