Nuclear power nickel-based 690 welding flux with low hot crack sensitivity and preparation method thereof

Abstract

The invention discloses a nuclear power nickel-based 690 welding flux with low hot crack sensitivity and a preparation method thereof, and the welding flux comprises the following raw materials in parts by weight: 45-55 parts of CaF2, 20-32 parts of Al2O3, 3-5 parts of wollastonite, 0.2-1 part of NaF, 2-5 parts of chrome green, 5-7 parts of metal manganese, 6-9 parts of Ni-Mg alloy, 5-9 parts of Nb-Ni alloy, and a binder accounting for 14-20% of the total weight of all the raw materials. After the welding flux is matched with an EQNiCrFe-7A welding strip for surfacing, the hot crack sensitivity of a welding seam is low, the welding seam forming and corrosion resistance are good, and the welding flux is mainly suitable for large-area surfacing of SA5083 steel of nuclear power pressure-bearing equipment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of welding materials, and particularly relates to a nickel-based 690 flux with low hot crack sensitivity for nuclear power and a preparation method thereof. BACKGROUND

[0002] Nickel-based corrosion-resistant materials are key raw materials for nuclear reactor nuclear island main equipment. From the history and development trend of nuclear power plants, the proportion of nickel-based corrosion-resistant materials in nuclear containers is increasing, and the material types are also changing and improving. Since the 1960s, steam generator corrosion-resistant materials have mainly used UNS N06600 nickel-based alloy or UNS N08800 iron-nickel-based alloy (00Cr20Ni32Fe). In recent years, UNS N06690 nickel-based alloy with better intergranular corrosion resistance and stress corrosion resistance has been used.

[0003] Nuclear power industry is a major key industry in China. Key materials for nuclear power have been mainly imported. Pressure vessels, evaporators, in-core components, pressurizers, passive residual heat removal heat exchangers, core makeup tanks and injection tanks in nuclear power equipment all require UNS N06690 alloy welding materials. With the approval of nuclear power projects and the large-scale start of nuclear power equipment manufacturing, the use of UNS N06690 alloy welding materials, especially welding strips and fluxes for overlay welding with electrodes, will increase significantly. It is necessary to develop UNS N06690 alloy welding materials that can be used for nuclear power equipment manufacturing.

[0004] Chinese patent CN113319467A discloses a nickel-based alloy welding strip for nuclear power, which has a chemical composition including C 0.01-0.03%, Si≤0.30%, Mn 0.10-1.00%, Cr 29.0-31.0%, Fe 3-9%, Nb 2.0-3.0%, Ta≤1.0%, Ti≤1.0%, Al≤0.5%, Mo 3.0-4.0%, and the balance of Ni, in terms of mass percentage. The invention increases the Mo, Nb and Ta contents of the welding strip to solve the problems of insufficient high-temperature strength and high-temperature plastic crack resistance; and controls the amount of Laves phase to prevent crystallization cracks. The electrode overlay metal obtained by using the welding strip has high high-temperature strength. However, the invention studies the welding strip, not the adhesive flux.

[0005] Chinese patent CN107363435A discloses a nickel-based adhesive flux for band electrode submerged arc surfacing for nuclear power and a preparation method thereof. The raw material composition of the adhesive flux comprises CaF2: 35-45 parts, Al2O3: 25-35 parts, wollastonite: 3-5 parts, NaF: 0.2-1 part, chromium green: 3-5 parts, metallic manganese: 7-9 parts, Ni-Mg alloy: 8-10 parts, and 14-20% of the total weight of all the aforementioned raw materials of a binder. The invention adopts a CaF2-Al2O3-CaSiO3 neutral slag system, a small amount of chromium oxide, fluoride and water glass to make the adhesive flux, matches the corresponding welding strip EQNiCrFe-7A for welding, and the surfacing layer metal has good intergranular corrosion resistance, which can be applied to the welding of SA5083 steel pipe plate of nuclear power pressure equipment. The matching EQNiCrFe-7A welding strip has good process performance and good intergranular corrosion cracking resistance. However, the patent does not conduct in-depth research on the hot crack sensitivity of the weld formed by the flux.

[0006] Hot cracking is a common problem of nickel-based high-temperature alloy. There is no special flux for UNS N06690 alloy welding material that can make the weld have low hot cracking sensitivity. SUMMARY

[0007] The purpose of the present application is to provide a nickel-based 690 flux with low hot cracking sensitivity for nuclear power and a preparation method thereof. The flux can be low-temperature dried and bonded, has good edge bonding, easy deslagging, stable arc, and after matching the EQNiCrFe-7A welding strip for surfacing, the critical strain rate of the weld is ≥0.0220% / ℃, the hot cracking sensitivity of the weld is low, the intergranular corrosion test of the weld deposited metal according to ASTM A262-15 E method is qualified, the weld forming and corrosion resistance are good; the flux is mainly suitable for large-area surfacing of SA5083 steel of nuclear power pressure equipment.

[0008] To achieve the above purpose, the technical scheme of the present application is as follows:

[0009] A nickel-based 690 flux with low hot cracking sensitivity for nuclear power, by weight, the raw material composition of the flux comprises CaF2: 45-55 parts, Al2O3: 20-32 parts, wollastonite: 3-5 parts, sodium fluoride: 0.2-1 part, chromium green: 2-5 parts, metallic manganese: 5-7 parts, Ni-Mg alloy: 6-9 parts, Nb-Ni alloy 5-9 parts, and 14-20% of the total weight of all the aforementioned raw materials of a binder.

[0010] Preferably, the binder adopts pure potassium water glass with modulus of 2.8-3.2 and Baume degree of 40-44°Be' at 20℃; preferably, the pure potassium water glass has the following chemical composition: K2O≥12wt%, SiO2≥25wt%, S≤0.005wt%, P≤0.005wt%.

[0011] Preferably, CaF2 is added in the form of fluorite with particle size ≤80 mesh; Al2O3 is added in the form of α-alumina with particle size ≤200 mesh; sodium fluoride has particle size ≤80 mesh; Ni-Mg alloy and Nb-Ni alloy are added in the form of alloy powder with particle size ≤50 mesh;

[0012] Preferably, the fluorite has the following chemical composition: CaF2≥95.0wt%, SiO2≤1.00wt%, S≤0.010wt%, P≤0.010wt%;

[0013] The sodium fluoride has the following chemical composition: NaF≥99.0wt%;

[0014] The Ni-Mg alloy has the following chemical composition: Ni≥70wt%, Mg≥20wt%, Ni+Mg≥98wt%;

[0015] The Nb-Ni alloy has the following chemical composition: Nb≥30wt%, Ni≥50wt%, Ni+Nb≥98wt%.

[0016] Preferably, the wollastonite has particle size ≤80 mesh and the following chemical composition: CaSiO3≥80wt%, SiO2≥40wt%, CaO≥42wt%;

[0017] The metallic manganese has particle size ≤80 mesh and the following chemical composition: Mn≥99.0wt%;

[0018] The chrome green has particle size ≤200 mesh and the following chemical composition: Cr2O3≥95.0wt%, S≤0.04wt%, P≤0.04wt%.

[0019] The main functions of the raw materials of the components in the flux are as follows:

[0020] CaF2: main slagging agent, CaF2 can reduce the surface tension of the molten slag, make the molten slag thin, reduce the viscosity, improve the fluidity of the slag, and appropriate amount of CaF2 can make the viscosity of the molten slag moderate, improve the forming of the weld. Too little CaF2, the molten slag becomes thick, the spreading and wetting are not good, and too much CaF2 can easily lead to unstable arc and weld edge biting phenomenon when the weld is overlapped.

[0021] Al2O3: Mainly used as a slagging agent, Al2O3 has high melting point and low oxidation, which can change the melting point, viscosity and fluidity of the flux. Al2O3 can improve the desulfurization capacity of the flux when coexisting with CaF2.

[0022] Wollastonite: Mainly used for slagging. It can improve the viscosity and fluidity of the molten slag and improve the spreadability. The calcium oxide in it can also work together with fluorite to further improve the desulfurization capacity of the flux when fluorite is added in large amounts.

[0023] Sodium fluoride: Low melting point fluoride, the effect of diluting slag is more obvious, and appropriate addition can also adjust the viscosity and fluidity of the slag pool, and improve the weld edge wetting angle. The sodium ion with low ionization potential can improve the stability of the arc.

[0024] Metal manganese: Participate in deoxidation, improve deslagging, and prevent the surface of the weld from being oxidized. At the same time, the addition of alloy can reduce the burning loss of Cr, Mo and other elements during welding, and ensure the chemical composition, high temperature oxidation resistance and corrosion resistance of the surfacing metal.

[0025] Ni-Mg alloy: Participate in deoxidation, ensure the chemical composition, high temperature oxidation resistance and corrosion resistance of the surfacing metal.

[0026] Nb-Ni alloy: Compensate for the loss of Ni and Nb in the weld, ensure the chemical composition of the weld metal after surfacing, and solid solution strengthening to improve the strength of the weld.

[0027] Chromium green: Increase the melting point of the molten slag, prevent the burning loss of alloy element Cr in the weld metal, reduce the generation of intermediate layer oxides, and improve the deslagging.

[0028] Further, the potassium oxide contained in the pure potassium water glass used in the binder can stabilize the arc, increase the basicity of the flux, and improve the desulfurization and dephosphorization capacity of the flux.

[0029] The flux of the present application adopts CaF2-Al2O3-CaSiO3 neutral slag system, adds a higher content of CaF2, so that it works together with Al2O3 and wollastonite to improve the desulfurization capacity of the flux, control the S content in the weld metal in a lower range, and improve the hot crack sensitivity of the weld. In addition, combined with the addition of Nb-Ni alloy, the loss of Nb and Ni in the weld is compensated, the Nb content in the weld metal is higher, so that the weld has higher strength on the basis of good hot crack sensitivity.

[0030] The welding flux matching EQNiCrFe-7A welding strip of the present application meets the following requirements after surfacing: the undiluted weld metal percentage by weight is C≤0.04%, Si≤0.75%, Cr: 28.00-31.50%, Mn≤5.00%, Al≤0.50%, Ti≤0.50%, Cu≤0.30%, 1.5≤Nb+Ta≤2.50%, Co≤0.01%, B≤0.001%, Zr≤0.02%, Mo≤0.50%, S≤0.005%, P≤0.015%, Fe: 7.00-12.00%, the balance including Ni and other unavoidable impurities, and other unavoidable impurities≤0.50%.

[0031] The undiluted chemical composition of the corresponding matching EQNiCrFe-7A welding strip of the present application meets the requirements of relevant standards.

[0032] Cr: solid solution strengthening element and carbide forming element, Cr2O3 forming element, improving stress corrosion cracking resistance.

[0033] Mo: solid solution strengthening element, improving high temperature creep strength.

[0034] Nb: Ni3Nb phase forming element, used for solid solution strengthening and promoting the precipitation of Ni3Nb phase to strengthen the weld metal.

[0035] Al: forming Ni3(Al, Ti) phase, solid solution strengthening, improving weld strength.

[0036] Ti: forming Ni3(Al, Ti) phase, solid solution strengthening, improving weld strength.

[0037] B and Zr: strengthening grain boundary, improving high temperature creep strength.

[0038] S: sulfur mainly causes hot cracking through grain boundary segregation and formation of low melting point eutectic, the present application controls the S content at a low level of≤0.005% through the joint action of CaF2, Al2O3 and wollastonite, thereby improving the hot cracking sensitivity of the weld.

[0039] The preparation method of the nuclear power use nickel-based 690 welding flux with low hot cracking sensitivity of the present application comprises the following steps:

[0040] 1) according to the weight parts of the above-mentioned adhesive flux raw materials, CaF2, Al2O3, wollastonite, NaF, chrome green, metallic manganese, Ni-Mg alloy and Nb-Ni alloy are weighed, and the components are uniformly mixed;

[0041] 2) wet mixing with the raw material binder, wet mixing time≥20 min;

[0042] 3) granulation, the granulation size is 20-120 mesh;

[0043] 4) sintering, the sintering temperature is 340-360 DEG C, and the sintering time is 2.5-3.5 h.

[0044] After the mixture is uniformly mixed according to the flux composition, wet mixing is further carried out for more than 20 min, so that the composition of the mixture is uniformly distributed, and product quality problems caused by uneven composition can be avoided.

[0045] Then, the flux is granulated by a granulator, and the flux with a particle size of 20-120 mesh is obtained; if the flux particle is too coarse or too fine, the welding process of the flux will be adversely affected.

[0046] The flux is baked at a low temperature of 340-360 DEG C, the components in the flux can be more uniformly distributed, a stable structure is formed, and the thermal stability and chemical stability of the flux are improved.

[0047] Compared with the prior art, the present application has the following beneficial effects:

[0048] The present application develops a flux with low hot crack sensitivity for UNS N06690 alloy welding material, adopts a CaF2-Al2O3-CaSiO3 neutral slag system, adds a high content of CaF2, so that the CaF2, Al2O3 and wollastonite jointly act to improve the desulfurization capacity of the flux, the S content in the weld metal is controlled in a low range, and the hot crack sensitivity of the weld is improved; in addition, combined with the addition of Nb-Ni alloy, the loss of Nb and Ni in the weld is compensated, the Nb content in the weld metal is higher, so that the weld has higher strength on the basis of good hot crack sensitivity. The flux is matched with the corresponding welding strip EQNiCrFe-7A for welding, the critical strain rate of the weld is greater than or equal to 0.0220% / ℃, the hot crack sensitivity of the weld is lower; the yield strength of the weld at room temperature is greater than or equal to 400 MPa, the tensile strength is greater than or equal to 620 MPa, the elongation is greater than or equal to 40%, the yield strength at 350 DEG C is greater than or equal to 245 MPa, the tensile strength is greater than or equal to 490 MPa, and the elongation is greater than or equal to 47%.

[0049] Furthermore, the flux of the present application is matched with the EQNiCrFe-7A welding strip, and the welding process is good without defects such as undercut, pressure pit, slag inclusion and welding tumor. According to the intergranular corrosion test of the weld deposited metal according to ASTM A262-15 E method, the test results are qualified, which proves that the hardfacing layer metal has good intergranular corrosion resistance, and can be applied to the inner wall corrosion-resistant hardfacing of nuclear pressure equipment. DETAILED DESCRIPTION

[0050] The present application will be further described below in combination with examples.

[0051] The flux composition of the present application is shown in Table 1.

[0052] Using the welding flux described in the embodiments of the present invention, SA5083 steel plate is used as the base material, and 690 welding strip is used for surfacing. The thickness of the base material plate is 50 mm, the specification of the welding strip is 60×0.5 mm, and the surfacing size is sufficient for chemical composition and intergranular corrosion sampling. A total of three layers are welded, two passes are welded in the first layer, and one pass is welded in the latter two layers. Welding specifications: DC reverse connection, welding current 700 - 850 A, voltage 27 - 28 V, welding speed 160 mm / min, preheating and interpass temperature of 150 °C, and heat treatment at 690 °C×6 h is carried out after welding.

[0053] The process control parameters for the preparation process of the embodiments of the present invention are shown in Table 2.

[0054] The chemical composition analysis of the weld deposited metal is shown in Table 3.

[0055] It can be seen from the results in Table 3 that after surfacing with the welding flux of the embodiments of the present invention matching the EQNiCrFe-7A welding strip, the undiluted weight percentages of the weld metal all meet the requirements: C≤0.04%, Si≤0.75%, Cr: 28.00 - 31.50%, Mn≤5.00%, Al≤0.50%, Ti≤0.50%, Cu≤0.30%, 1.5%≤Nb+Ta≤2.50%, Co≤0.01%, B≤0.001%, Zr≤0.02%, Mo≤0.50%, S≤0.008%, P≤0.015%, Fe: 7.00 - 12.00%, and the balance includes Ni and other inevitable impurities, and other inevitable impurities≤0.50%.

[0056] The intergranular corrosion mechanical property test is carried out by the ASTM A262-15E method, and the heat treatment is at 690 °C×6 h. The test results are shown in Table 4. It can be seen from Table 4 that the intergranular corrosion test results of the welds in the embodiments of the present invention are all qualified.

[0057] The weld thermal crack sensitivity test is carried out according to the method of the annular mosaic block test (THOMS annular crack test) in Appendix B of German KTA1408.2. The test results are shown in Table 5. It can be seen from Table 5 that no defect is shown in the detection results.

[0058] The quantitative analysis of the thermal crack sensitivity of the welds in the embodiments of the present invention is carried out according to ISO / TR 17641-3:2005, and the results are shown in Table 6.

[0059] It can be seen from Table 6 that the critical strain rate of the welds obtained by the welding flux + NiCrFe-7A welding strip of the present invention≥0.0220%. The critical strain rate of the welds of domestic similar products≥0.0133%, and the critical strain rate of the welds of a certain international imported product≥0.0121%.

[0060] The mechanical property test was carried out on the welding seams of the inventive examples and the comparative examples according to RCC-M:2007, and the results are shown in Table 7.

[0061]

[0062]

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[0065]

Claims

1. A nickel-based 690 flux with low hot cracking sensitivity for nuclear power applications, characterized in that, The flux, by weight, consists of the following raw materials: CaF2: 45-55 parts, Al2O3: 20-32 parts, wollastonite: 3-5 parts, sodium fluoride: 0.2-1 parts, chrome green: 2-5 parts, metallic manganese: 5-7 parts, Ni-Mg alloy: 6-9 parts, Nb-Ni alloy: 5-9 parts, and a binder comprising 14-20% of the total weight of all the aforementioned raw materials.

2. The nickel-based 690 flux with low hot cracking sensitivity for nuclear power as described in claim 1, characterized in that, The adhesive is pure potassium silicate with a modulus of 2.8 to 3.2 and a Baumé degree of 40 to 44°Beˊ at 20°C; preferably, the chemical composition of the pure potassium silicate is required to be as follows by weight percentage: K2O≥12wt%, SiO2≥25wt%, S≤0.005wt%, P≤0.005wt%.

3. The nickel-based 690 flux with low hot cracking sensitivity for nuclear power as described in claim 1, characterized in that, CaF2 is added in the form of fluorite with a particle size ≤ 80 mesh; preferably, the chemical composition of fluorite by weight percentage is: CaF2 ≥ 95.0 wt%, SiO2 ≤ 1.00 wt%, S ≤ 0.010 wt%, P ≤ 0.010 wt%.

4. The nickel-based 690 flux with low hot cracking sensitivity for nuclear power as described in claim 1, characterized in that, Al2O3 is added in the form of α-alumina with a particle size ≤200 mesh; sodium fluoride has a particle size ≤80 mesh; preferably, the chemical composition weight percentage of sodium fluoride is: NaF≥99.0wt%.

5. The nickel-based 690 flux with low hot crack sensitivity for nuclear power as described in claim 1, characterized in that, Ni-Mg alloy and Nb-Ni alloy are added in the form of alloy powder with a particle size ≤50 mesh; preferably, the chemical composition weight percentage of Ni-Mg alloy is: Ni ≥70wt%. Mg≥20wt%, Ni+Mg≥98wt%; The chemical composition weight percentage requirements for Nb-Ni alloys are: Nb≥30wt%, Ni≥50wt%, Ni+Nb≥98wt%.

6. The nickel-based 690 flux with low hot crack sensitivity for nuclear power as described in claim 1, characterized in that, The particle size of wollastonite is ≤80 mesh, and its chemical composition by weight percentage is required to be: CaSiO3≥80wt%, SiO2≥40wt%, CaO≥42wt%.

7. The nickel-based 690 flux with low hot cracking sensitivity for nuclear power as described in claim 1, characterized in that, The particle size of metallic manganese is ≤80 mesh, and its chemical composition weight percentage requirement is: Mn≥99.0wt%.

8. The nickel-based 690 flux with low hot cracking sensitivity for nuclear power as described in claim 1, characterized in that, The particle size of chrome green is ≤200 mesh, and its chemical composition weight percentage requirements are: Cr2O3≥95.0wt%, S≤0.04wt%, P≤0.04wt%.

9. The nickel-based 690 flux for nuclear power with low hot cracking sensitivity as described in any one of claims 1 to 8, characterized in that, After the flux is matched with EQNiCrFe-7A welding strip for surfacing, the weight percentage of the undiluted weld metal meets the following requirements: C≤0.04%, Si≤0.75%, Cr: 28.00~31.50%, Mn≤5.00%, Al≤0.50%, Ti≤0.50%, Cu≤0.30%, 1.5≤Nb+Ta≤2.50%, Co≤0.01%, B≤0.001%, Zr≤0.02%, Mo≤0.50%, S≤0.005%, P≤0.015%, Fe: 7.00~12.00%, with the balance including Ni and other unavoidable impurities, and other unavoidable impurities ≤0.50%.

10. The method for preparing the low-hot-cracking-susceptibility nickel-based 690 flux for nuclear power as described in any one of claims 1 to 9, characterized in that, Includes the following steps: 1) Weigh out CaF2, Al2O3, wollastonite, NaF, chrome green, metallic manganese, Ni-Mg alloy and Nb-Ni alloy according to the weight parts of the above flux raw materials, and mix each component evenly; 2) Add the raw material binder and wet mix for ≥20 min; 3) Granulation, with a particle size of 20-120 mesh; 4) Sintering, sintering temperature 340~360℃, sintering time 2.5~3.5h.

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