Use of nickel-chromium-iron-molybdenum alloys without titanium

Abstract

The invention relates to the use of an alloy having the following composition in mass %: max. 0.02% C, max. 0.01% S, max. 0.03% N, 20.0-23.0% Cr, 39.0-44.0% Ni, 0.4-<1.0% Mn, 0.1-<0.5% Si, >4.0-<7.0%, max. 0.15% Nb, >1.5-<2.5% Cu, 0.05-<0.3% Al, max. 0.5% Co, 0.001-<0.005% B, 0.005-<0.015% Mg, balance Fe and impurities resulting from melting, which is further processed via the molten phase as an alloy solid in the form of wire, strip, bar or powder and used in the field of wet corrosion applications in the oil and gas industry and in the chemical industry.

Description

Technical Field

[0001] The present invention relates to the use of a titanium-free nickel-chromium-iron-molybdenum alloy having high pitting corrosion resistance, crevice corrosion resistance, high yield point and strength.

Background Art

[0002] Alloy 825 is a material with high corrosion resistance used in the petroleum industry, gas industry, and chemical industry. Alloy 825 is sold under the material number 2.4858 and has the following chemical composition: C≤0.05%, S≤0.03%, Cr 19.5 - 23.5%, Ni 38 - 46%, Mn≤1.0%, Si≤0.5%, Mo 2.5 - 3.5%, Ti 0.6 - 1.2%, Cu 1.5 - 3.0%, Al≤0.2%, Fe balance.

[0003] Alloy 825 is a material stabilized with titanium, that is, the addition of titanium should neutralize harmful carbon in the material as much as possible. Alloy 825 is used as a wet corrosion alloy in various industrial fields including the petroleum industry and gas industry, and has a PREN of 30. In particular, it has only moderate resistance to pitting corrosion and crevice corrosion in seawater applications. Those skilled in the art understand that the effective total PREN is the pitting corrosion resistance index.

[0004] PREN = 1×%Cr + 3.3×%Mo

[0005] PREN summarizes alloying elements having a positive effect on pitting corrosion resistance and crevice corrosion resistance at coefficients specific to the material.

[0006] Alloy 825 (ISO 18274: Ni8065) has not been established as a welding consumable or filler metal (FM) and is rarely used. The reason for this is difficult workability, which is often shown in that the weld metal has high-temperature cracking in the form of solidification cracking and remelting cracking. In particular, in important applications in the oil and gas industries, this processing problem inherent in the material becomes an exclusion criterion, which often leads to the use of an alternative welding consumable, namely welding consumable FM 625 (ISO 18274: Ni6625), instead of FM 825. However, FM 625 has the following disadvantages compared to FM 825: 1) FM 625 is alloyed very highly compared to FM 825 and contains at least 58.0% nickel, at least 8.0% molybdenum, and at least 3.0% niobium. Therefore, for welding structural members made of Alloy 825, FM 625 is overly alloyed too strongly as a welding consumable, which results in high costs and unnecessary consumption of resources such as the rare element niobium.

[0007] 2) The weld metal made of FM 625 is difficult to reprocess mechanically compared to FM 825, for example, during the turning finish of surfacing welding or when flattening the excessive buildup of the weld seam, because it clearly has a high hardness. For example, the hardness of the FM 825 weld metal is below 250 HV10, while the hardness of FM 625 is usually 310 HV10.

[0008] 3) In the case of FM 625, especially during post-weld heat treatment (so-called post-weld heat treatment; PWHT) or during hot forming by induction bending of, for example, surfacing-welded pipes, there is a risk of forming undesirable γ'' phase or delta phase by the alloying element niobium. The formation of the γ'' phase or δ phase causes a dramatic loss of corrosion resistance and / or ductility.

[0009] In addition to a relatively low PREN and poor weldability due to the formation of hot cracks, FM 825 has a further drawback, namely it has titanium as an alloying element. Titanium can be easily oxidized uncontrollably when the material is present as a liquid phase in the case of fusion welding, which may lead to a lack of intrusive titanium in the weld metal and thus a reduction in its stabilizing effect without being defined. Furthermore, the oxidation or nitridation of titanium during welding may cause a significant deterioration in the quality of the weld joint by reducing the strength, ductility and / or corrosion resistance of the weld metal due to titanium oxide particles or titanium nitride particles that are formed and distributed in the weld metal.

[0010] The material described in German Patent Application Publication No. 102014002402 (DE 10 2014 002 402 A1) is also known under the name Alloy 825 CTP and is only used in the form of products such as sheet materials, strip materials, pipe materials (longitudinally seam-welded and seamless), bar materials, or forged parts.

[0011] The above publication discloses a titanium-free alloy having high pitting corrosion resistance and crevice corrosion resistance, as well as a high yield point in the strain-hardened state, and in mass % C maximum 0.02% S maximum 0.01% N maximum 0.03% Cr 20.0 - 23.0% Ni 39.0 - 44.0% Mn 0.4 - <1.0% Si 0.1 - <0.5% Mo >4.0 - <7.0% Nb maximum 0.15% Cu >1.5 - <2.5% Al 0.05 - <0.3% Co maximum 0.5% B 0.001 - <0.005% Mg 0.005 - <0.015% Fe the balance, as well as impurities resulting from melting and discloses said alloy having the above.

[0012] Furthermore, a method for manufacturing this alloy, a) melting the alloy as is in continuous casting or ingot casting, b) performing a homogenization heat treatment of the produced slab / billet at 1150 - 1300 °C for 15 - 25 hours in order to remove segregation caused by an increase in the molybdenum content, where c) the homogenization heat treatment is particularly carried out following the first hot forming, is described.

[0013] The aforementioned material (Alloy 825 CTP) has a high PREN of approximately 42 for Alloy 825 and is not titanium alloyed. The material Alloy 825 CTP was developed to overcome the following drawbacks of Alloy 825: 1) Poor solubility and castability due to titanium content (keyword: clogging) 2) Unwanted precipitation of TiC or Ti(C,N) in the structure 3) Not seawater resistant / relatively poor pitting corrosion resistance and crevice corrosion resistance.

Prior Art Documents

Patent Documents

[0014]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0015] The problem of the present invention is to provide a new application field for the material described in German Patent Application Publication No. 102014002402.

[0016] The above problem is solved by the following composition: C maximum 0.02% S maximum 0.01% N maximum 0.03% Cr 20.0 - 23.0% Ni 39.0 - 44.0% Mn 0.4 - <1.0% Si 0.1 - <0.5% Mo >4.0 - <7.0% Nb maximum 0.15% Cu >1.5 - <2.5% Al 0.05 - <0.3% Co maximum 0.5% B 0.001 - <0.005% Mg 0.005 - <0.015% Fe the balance, and impurities resulting from melting Use of a titanium-free alloy having, in mass %, said alloy being further processed via a molten phase into alloy solids in the form of wire, strip, rod or powder and being used in the field of wet corrosion applications in the petroleum industry and the gas industry as well as the chemical industry, which is solved by said use of the alloy.

[0017] An advantageous further aspect of the subject matter of the invention results from the dependent claims.

[0018] The suitability of Alloy 825 CTP as a filler material is not described in DE 10 2014 002 402 A1, and product forms such as welding wire, welding strip and powder (e.g. for additive manufacturing processes) are not mentioned. The new fields of application are characterized by the fact that the material is basically processed via a molten phase.

[0019] Carbon of the element is provided in the alloy as follows: · maximum 0.02%.

[0020] Alternatively, carbon can be limited as follows: · maximum 0.015% · maximum 0.01% · <0.01%.

[0021] The chromium content is 20.0 - 23.0%. Preferably, Cr can be adjusted within the following spread range in the alloy: · 20.0 - 22.0% · 21.0 - 23.0% · 20.5 - 22.5% · 22.0 - 23.0%.

[0022] The nickel content is 39.0 - 44.0%, and the preferred range can be adjusted as follows: · 39.0 - <42.0% · 39.0 - <41.0% · 39.0 - <40.0%.

[0023] The molybdenum content is >4.0 - <7.0%, and here, depending on the field where the alloy is used, the preferred molybdenum content can be adjusted as follows: · >5.0 - <7.0% · >5.0 - <6.5% · >5.5 - <6.5% · >6.0 - <7.0%.

[0024] The said material can preferably be used for the following applications: · As a filler material in the form of a wire or rod for joining welding for the base material Alloy 825 or Alloy 825 CTP, · As a filler material in the form of a wire or rod for joining welding for super austenitic steel or nickel-based alloy, · For the wire arc additive manufacturing method (WAAM), that is, for the application of manufacturing structural members using an arc welding process with a welding wire, · In the form of powder for the so-called plasma powder welding method, · In the form of powder for the so-called additive manufacturing printing method for manufacturing structural members, · In the form of a strip for build-up welding or joining welding, for the so-called electro-slag and / or submerged arc welding, · In the form of powder for a spraying process, such as flame spraying, · In the form of a coated rod electrode, · In the form of a cored wire electrode.

[0025] When conducting investigations on hot cracking, welding tests, and modeling considerations, unexpectedly, the hot cracking safety, that is, the material's resistance to the formation of solidification cracks, and re-melting cracks during the melt processing of the above materials, were found to be significantly better than those of the welding wire FM 825.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Figure 4

Examples

[0027] Investigations using a modified varestraint - transform varestraint (MVT) hot cracking test show the advantages of FM 825 CTP over FM 825 as follows:

[0028] The MVT test is a high-temperature cracking test with external stress applied. Samples of material FM 825 CTP and samples of FM 825 were successively used, with an energy per unit length (Streckenergie) of 7.5 kJ / cm and 14.5 kJ / cm, and the total bending strain of 1%, 2%, and 4% of each sample was applied for inspection. The evaluation was carried out according to the length of high-temperature cracks in the weld metal area and the heat-affected area on the sample surface after the test process. The values of a series of tests were compared and shown in a graph, where the material can basically be classified into three high-temperature crack classifications according to the determined inspection values (Figure 1). For the implemented investigation, samples made of pure weld metal were used.

[0029] According to these MVT results, FM 825 welded with an energy of 7.5 kJ / cm per unit length and applying a total bending strain of 1%, 2%, and 4% respectively has measured high-temperature crack values (total length of high-temperature cracks) in sector 2, which means "tendency of high-temperature cracks", and sector 3, which means "risk of high-temperature cracks". In the case of the MVT test similarly carried out using FM 825 CTP, all high-temperature crack values (total length of high-temperature cracks) are in sector 1, where the material is classified as "high-temperature crack resistant". Therefore, the MVT investigation shows unexpectedly good weldability in the form of high resistance to high-temperature cracking of FM 825 CTP.

[0030] The unexpected result of the MTV investigation was verified by welding two plates of Alloy 825 CTP with batch number 130191 together in a butt joint using the plasma welding method, where the following welding parameter set was used: welding current 220 A, welding voltage = 19.5 V, welding speed = 30 cm / min, plasma gas flow rate = 1 l / min, shielding gas flow rate = 20 l / min, work distance = 5 mm.

[0031] Figure 2 shows the macroscopic cross-section of the welded joint. No high-temperature cracks were found in the weld seam area.

[0032] Calculations were carried out in J-Mat Pro to further investigate the unexpectedly good weldability. Figure 3 shows a comparison of the cooling rate dependence in the solidification range of FM 825 CTP and FM 825. In the model, the solidification range is an indicator of the susceptibility of the material to hot cracking and is, in the ideal case (e.g., for a pure material), 0. During welding, the cooling rate varies greatly depending on the method, the thickness of the structural member, the welding parameters, etc., so it is particularly meaningful to observe not only individual cooling rates but also the range of cooling rates from 0 °C / s to 50 °C / s. Figure 3 shows that a solidification range 40 °C to 70 °C lower than that of FM 825 was modeled for FM 825 CTP in the overall investigated cooling rate range.

[0033] Alloy 825 or FM 825 CTP was melted in the following composition:

Table 1-1

[0034]

Table 1-2

[0035] The material FM 825 CTP was melted on an industrial scale as a filler material and further processed into a filler material, in particular as a welding wire having a diameter of 1.00 mm.

[0036] As shown schematically in Figure 4, using the wire of batch 132490, fully mechanized surfacing welding was carried out on S 355 C steel by a metal inert gas welding process (MIG process) using a pulsed arc. As welding parameters, welding current = 170 A, welding voltage = 24 V, wire speed = 7.4 m / min, welding speed = 55 cm / min were used, and pure argon was used as the shielding gas. The surfacing welding was finished in part in two layers. It was shown that no macroscopic cracks or microscopic cracks were detected on the surface of the weld by either visual inspection or dye penetrant inspection.

[0037] The above results support the following new findings: · FM 825 CTP can be used, for example, for build-up welding at the end of mechanically clad tubes, · FM 825 CTP can be used as a joining welding material for joining Alloy 825 and / or Alloy 825 CTP structural members, · FM 825 CTP can be used as a material for wire arc additive manufacturing (WAAM), where it has better reworkability than, for example, a corresponding additively manufactured structural member made of FM 625, · FM 825 CTP can be used in powder form for the field of additive manufacturing, where it can be a cost-effective, resource-saving and more readily mechanically reworkable alternative to FM 625, · Symmetrically to FM 825, in the case of FM 825 CTP, titanium is not an alloying element. Thus, instead of the noble gases used in other cases, a shielding gas with nitrogen (content) for welding and / or printing is possible, which reduces the manufacturing costs. [Embodiment 1] The following composition: C at most 0.02% S at most 0.01% N at most 0.03% Cr 20.0~23.0% Ni 39.0 - 44.0% Mn 0.4 - <1.0% Si 0.1 - <0.5% Mo >4.0 - <7.0% Nb at most 0.15% Cu >1.5 - <2.5% Al 0.05~<0.3% Co at most 0.5% B 0.001~<0.005% Mg 0.005 - <0.015% Fe the balance, and impurities resulting from melting The use of an alloy having the above in mass %, wherein the alloy is further processed via a molten phase into alloy solids in the form of wire, strip, rod or powder, and is used in the field of wet corrosion applications in the petroleum industry, gas industry and chemical industry. [Embodiment 2] C at most 0.015% S at most 0.005% N at most 0.02% Cr 21.0~<23.0% Ni >39.0 - <43.0% Mn 0.5 - 0.9% Si 0.2 - <0.5% Mo >4.5 - 6.5% Nb at most 0.15% Cu >1.6 - <2.3% Al 0.06~<0.25% Co at most 0.5% B 0.002~0.004% Mg 0.006 - 0.015% Fe the balance, and impurities resulting from melting The use according to Embodiment 1, having the above in mass %. [Embodiment 3] C at most 0.010% S at most 0.005% N at most 0.02% Cr 22.0~<23.0% Ni >39.0 - <43.0% Mn 0.55 - 0.9% Si 0.2 - <0.5% Mo >5.0 - 6.5% Nb at most 0.15% Cu >1.6 - <2.2% Al 0.06~<0.20% Co at most 0.5% B 0.002~0.004% Mg 0.006 - 0.015% Ti at most 0.10% P at most 0.025% W at most 0.50% Fe at least 22%, and impurities resulting from melting The use according to Embodiment 1 or 2, having the above in mass %. [Embodiment 4] The use according to any one of Embodiments 1 to 3, characterized in that the material is used as a wire-shaped or rod-shaped filler metal for build-up welding using an arc process or a laser process. [Embodiment 5] The use according to any one of Embodiments 1 to 3, characterized in that the material is used as a wire-shaped or rod-shaped filler metal for joining welding for a base material, such as Alloy 825 or Alloy 825 CTP. [Embodiment 6] The use according to any one of Embodiments 1 to 3, characterized in that the material is used as a wire-shaped or rod-shaped filler metal for joining welding for super austenitic steel and / or nickel-based alloys. [Embodiment 7] The use according to any one of Embodiments 1 to 3, characterized in that the material is processed using additive manufacturing by using a welding wire by an arc welding process, a laser welding process, or an electron beam welding process. [Embodiment 8] The use according to any one of Embodiments 1 to 3, characterized in that the material is in powder form and is used for so-called plasma powder welding. [Embodiment 9] The use according to any one of Embodiments 1 to 3, characterized in that the material is in powder form and is used for so-called additive manufacturing printing for manufacturing structural members. [Embodiment 10] The use according to any one of Embodiments 1 to 3, characterized in that the material is in strip form and is used for so-called electroslag welding and / or submerged arc welding for build-up welding or joining welding. [Embodiment 11] The use according to any one of Embodiments 1 to 3, characterized in that the material is in powder form and is used for a spraying process, in particular flame spraying. [Embodiment 12] The use according to any one of Embodiments 1 to 3, characterized in that the material is used in the form of a coated rod electrode. [Embodiment 13] The use according to any one of Embodiments 1 to 3, characterized in that the material is used in the form of a cored wire electrode.

Claims

1. By mass%: C at most 0.02% N at most 0.03% Cr 20.0 - 23.0% Ni 39.0 - 44.0% Mn 0.4 - <1.0% Si 0.1 - <0.5% Mo >4.0 - <7.0% Nb at most 0.15% Cu >1.5 - <2.5% Al 0.05 - <0.3% Co at most 0.5% B 0.001 - <0.005% Mg 0.005 - <0.015%, and impurities resulting from melting, and Fe the balance, Use of an alloy having a composition consisting of, wherein the alloy is further processed via a molten phase as an alloy filler material in the form of a wire, as an alloy filler material in the form of a strip, as an alloy filler material in the form of a rod, or as an alloy filler material in the form of a powder, and is used in the field of wet corrosion applications in the petroleum and gas industries.

2. The alloy, by mass% C at most 0.015% N at most 0.02% Cr 21.0 - <23.0% Ni >39.0 - <43.0% Mn 0.5 - 0.9% Si 0.2 - <0.5% Mo >4.5 - 6.5% Nb at most 0.15% Cu >1.6 - <2.3% Al 0.06 - <0.25% Co at most 0.5% B 0.002 - 0.004% Mg 0.006 - 0.015% and impurities resulting from melting, and Fe the balance The use according to claim 1, comprising

3. The alloy is, in mass% C at most 0.010% N at most 0.02% Cr 22.0 to <23.0% Ni > 39.0 to <43.0% Mn 0.55 to 0.9% Si 0.2 to <0.5% Mo > 5.0 to 6.5% Nb at most 0.15% Cu > 1.6 to <2.2% Al 0.06 to <0.20% Co at most 0.5% B 0.002 to 0.004% Mg 0.006 to 0.015% And impurities due to melting, and Fe at least 22%, The use according to claim 1 or 2, comprising

4. The use according to any one of claims 1 to 3, characterized in that the alloy is used as a wire-shaped or rod-shaped filler material for build-up welding using an arc process or a laser process.

5. The use according to any one of claims 1 to 3, characterized in that the alloy is used as a wire-shaped or rod-shaped filler material for joining welding of a base material.

6. The use according to any one of claims 1 to 3, characterized in that the alloy is used as a wire-shaped or rod-shaped filler material for joining welding of super austenitic steel and / or nickel-based alloy.

7. The use according to any one of claims 1 to 3, characterized in that the alloy is processed using additive manufacturing by using a welding wire in an arc welding process, a laser welding process, or an electron beam welding process.

8. The use according to any one of claims 1 to 3, characterized in that the alloy is in the form of a powder and is used for plasma powder welding method.

9. The use according to any one of claims 1 to 3, characterized in that the alloy is in the form of a powder and is used for additive manufacturing printing method for manufacturing a structural member.

10. The use according to any one of claims 1 to 3, characterized in that the alloy is in the form of a strip and is used for electro-slag welding and / or submerged arc welding for build-up welding or for joining welding.

11. The use according to any one of claims 1 to 3, characterized in that the alloy is in the form of a powder and is used for a spraying process.

12. The use according to any one of claims 1 to 3, characterized in that the alloy is used in the form of a coated rod electrode.

13. The use according to any one of claims 1 to 3, characterized in that the alloy is used in the form of a cored wire electrode.

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