Cladding material for improving liquid lead and bismuth corrosion resistance of ferrite / martensitic steel and application of cladding material

Abstract

The invention discloses a cladding material for improving liquid lead and bismuth corrosion resistance of ferrite / martensitic steel and application of the cladding material, and belongs to the technical field of corrosion protection of nuclear materials. The cladding material is prepared from the following components in percentage by mass: less than or equal to 0.12% of C, 3.00 to 5.50% of Si, 1.00 to 2.00% of Mn, less than or equal to 0.015% of P, less than or equal to 0.015% of S, 16.50 to 21.50% of Cr, 11.00 to 22.00% of Ni, 0.10 to 1.00% of Nb, 0.80 to 1.20% of Mo, 0.0035 to 0.005% of N and the balance of Fe. The wire is cladded on the surface of the 9-12wt.% Cr ferrite / martensitic steel, the cladding layer and a matrix are metallurgically bonded, no welding defect exists, and the liquid lead bismuth corrosion resistance of the 9-12wt.% Cr ferrite / martensitic steel is effectively improved. The cladding material has a wide application prospect in the field of advanced nuclear industry.

Description

Technical Field

[0001] The present invention belongs to the technical field of corrosion protection of nuclear materials, and in particular relates to a cladding material for improving the corrosion resistance of ferrite / martensitic steel to liquid lead-bismuth. Background Art

[0002] Liquid lead-bismuth (LPB)-cooled fast reactors (LLBRs) possess excellent neutron physics, thermal-hydraulic, and safety characteristics, making them widely recognized as a candidate for fourth-generation nuclear energy systems worldwide. However, high-temperature, fluid LPB can severely corrode structural materials, posing a threat to the safe operation of the reactor. Ferritic / martensitic steels with 9-12 wt.% Cr (Cr) content offer excellent mechanical properties and resistance to radiation swelling, making them the preferred structural material for LPBRs. However, when used in LPB, the Cr content and the liquid metal's grain boundary penetration corrosion make it difficult to form a dense oxide layer on the steel surface. Matrix elements and Pb-Bi metal easily penetrate the oxide layer, accelerating oxidative corrosion of the substrate. Furthermore, the poorly dense oxide layer is prone to breakage and flaking, which also accelerates oxidative corrosion. Improving the ferritic / martensitic steel's resistance to LPB corrosion is crucial for ensuring the safe operation of fast reactors.

[0003] Pre-forming an anti-corrosion layer on the surface of ferrite / martensitic steel helps improve the ferrite / martensitic steel's resistance to liquid lead-bismuth corrosion. Chinese patents (CN105297034B, CN113106385B, and CN112646957B) respectively use methods such as mechanical grinding, aluminizing, and pre-oxidation treatment on the steel surface to improve the ferrite / martensitic steel's resistance to liquid lead-bismuth corrosion. However, the coatings prepared by these surface treatment methods have shortcomings such as small thickness (approximately tens of microns) and loose bonding. Under long-term, high-speed erosion by high-temperature liquid lead-bismuth, the coating easily peels off, thereby affecting the lead-bismuth corrosion of ferrite / martensitic steel. The present invention develops a cladding material that uses a tungsten inert gas shielded welding method to prepare a cladding metal layer on the surface of ferrite / martensitic steel. The cladding metal layer has excellent resistance to liquid lead-bismuth corrosion, thereby effectively preventing liquid lead-bismuth corrosion of ferrite / martensitic steel. Summary of the Invention

[0004] To address the problem that ferrite / martensitic steel (ferrite-martensitic steel), a structural material used in liquid lead-bismuth-cooled fast reactors, has insufficient resistance to liquid lead-bismuth corrosion, the present invention aims to provide a cladding material that forms a layer of cladding metal on the surface of the ferrite / martensitic steel. This cladding metal layer can effectively resist the corrosion of the ferrite / martensitic steel by liquid lead-bismuth.

[0005] The present invention adopts the following technical solution. The cladding material for improving the liquid lead-bismuth corrosion resistance of ferrite / martensitic steel is composed of the following components in mass percentage: C≤0.12%, Si3.00-5.50%, Mn 1.00-2.00%, P≤0.015%, S≤0.015%, Cr 16.50-21.50%, Ni 11.00-22.00%, Nb 0.10-1.00%, Mo 0.80-1.20%, N 0.0035-0.005%, and Fe balance.

[0006] Furthermore, the cladding material is characterized in that the cladding material is a solid wire.

[0007] Furthermore, the cladding material is characterized in that the cladding metal layer is prepared by adopting a tungsten inert gas shielded welding method and using pure Ar as the welding shielding gas.

[0008] Furthermore, the cladding material is characterized by: tungsten inert gas shielded welding process parameters: welding current is 150-200A, welding voltage is 12-17V, welding speed is 70-120mm / min, and wire feeding speed is 700-1200mm / min.

[0009] Furthermore, the cladding material is characterized by: current type / polarity: direct current positive connection (DCEN), interlayer temperature ≤ 100°C, shielding gas: Ar with a purity ≥ 99.995%, and a shielding gas flow rate of 10 to 20 L / min during welding.

[0010] Furthermore, the cladding material is characterized in that the ferrite / martensitic steel is 9-12wt% Cr ferrite / martensitic steel, and the substrate is one of a plate, a rod or a pipe.

[0011] Furthermore, the cladding material is characterized in that the cladding metal layer has a thickness of 1.5 to 2.5 mm, is metallurgically bonded to the substrate, has no welding defects, and has no lead-bismuth infiltration in the cladding metal layer after being corroded in a 550°C oxygen-controlled lead-bismuth solution for 3000 hours, thereby effectively preventing liquid lead-bismuth corrosion.

[0012] The beneficial effects of the present invention are as follows: the present invention develops an austenitic stainless steel wire, which forms a cladding metal layer with a thickness of 1.5 to 2.5 mm on the surface of ferrite / martensitic steel through a tungsten inert gas shielded welding method, which can effectively prevent liquid lead and bismuth from corroding the ferrite / martensitic steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1The scanning electron microscope image of the cross-sectional morphology of the cladding layer metal prepared from the wire material with the chemical composition of the present invention after being corroded in an oxygen-controlled lead-bismuth solution at 550°C for 3000 hours: Figure 1 (a) Example 1, Figure 1 (b) Example 2, Figure 1 (c) Example 3.

[0014] Figure 2 The cross-sectional element distribution of the cladding layer prepared from the wire described in Example 1 after corrosion in a 550°C oxygen-controlled lead-bismuth solution for 3000 hours is as follows: Figure 2 (a) is oxygen element, Figure 2 (b) is silicon element, Figure 2 (c) is lead element, Figure 2 (d) is bismuth element.

[0015] Figure 3 The cross-section of the cladding metal prepared from the wire described in Comparative Example 1 was corroded in a 550°C oxygen-controlled lead-bismuth solution for 3000 hours: Figure 3 (a) Corrosion morphology, Figure 3 (b) Pb element distribution.

[0016] Figure 4 The cross-section of the cladding metal prepared from the wire described in Comparative Example 2 was corroded in a 550°C oxygen-controlled lead-bismuth solution for 3000 hours: Figure 4 (a) Corrosion morphology, Figure 4 (b) Pb element distribution.

[0017] Figure 5 This is the cross-sectional morphology of the 9wt.% Cr ferrite / martensite steel without surface cladding treatment in Comparative Example 3 after corrosion in an oxygen-controlled lead-bismuth solution at 550°C for 3000 hours. DETAILED DESCRIPTION

[0018] In the present invention, the wire can be produced using either a vacuum induction furnace or an electric furnace with external refining, as long as the final chemical composition of the welding wire meets the requirements of the aforementioned invention. The following specific embodiments primarily focus on 9 wt.% Cr ferrite / martensitic steel, but the present invention is equally applicable to other 9-12 wt.% Cr ferrite / martensitic steels.

[0019] Example 1:

[0020] The chemical composition (wt.%) of the cladding material wire is:

[0021] C: 0.11%, Si: 3.47%, Mn: 1.11%, P < 0.005%, S: 0.0018%, Cr: 17.47%, Ni: 11.5%, Nb: 0.94%, Mo: 1.02%, N: 0.0042%, Fe balance.

[0022] Example 2:

[0023] The chemical composition (wt.%) of the cladding material wire is:

[0024] C: 0.004%, Si: 3.90%, Mn: 1.40%, P < 0.005%, S < 0.001%, Cr: 18.97%, Ni: 18.90%, Nb: 0.10%, Mo: 1.02%, N: 0.0047%, Fe balance.

[0025] Example 3:

[0026] The chemical composition (wt.%) of the cladding material wire is:

[0027] C: 0.096%, Si: 5.00%, Mn: 1.54%, P < 0.005%, S < 0.001%, Cr: 18.95%, Ni: 17.00%, Nb: 0.11%, Mo: 1.02%, N: 0.036%, Fe balance.

[0028] Comparative Example 1:

[0029] The chemical composition (wt.%) of the comparative cladding material wire is:

[0030] C: 0.097%, Si: 0.40%, Mn: 1.52%, P < 0.005%, S < 0.001%, Cr: 15.83%, Ni: 26.0%, Mo: 6.25%, N: 0.19%, Fe balance.

[0031] Comparative Example 2:

[0032] The chemical composition (wt.%) of the comparative cladding material wire is:

[0033] C: 0.10%, Si: 2.03%, Mn: 1.53%, P < 0.005%, S: 0.0013%, C: 15.95%, Ni: 25.60%, Mo: 6.29%, N: 0.19%, Fe balance.

[0034] Comparative Example 3:

[0035] The chemical composition (wt.%) of the matrix 9wt%Cr ferrite / martensitic steel is:

[0036] C: 0.17%, Si: 1.10%, Mn: 0.14%, Cr: 9.20%, Ni: 0.70%, Mo: 0.50%, W: 0.60%, Nb: 0.35%, V: 0.25%, N: 0.025%, Fe balance.

[0037] Application examples:

[0038] The wires of different compositions in Examples 1 to 3 (diameter 1.6 mm) were used to prepare a cladding metal layer on the upper surface of 9wt.%Cr ferrite / martensitic steel (size: 150 mm×100 mm×12 mm) using a Panasonic TA1600 automatic welding robot. The size of the cladding metal layer was 100 mm×60 mm×(1.5-2.5) mm. The cladding process parameters were as follows: welding current of 170 A, welding voltage of 14 V, welding speed of 90 mm / min, wire feeding speed of 900 mm / min, and flow rate of shielding gas argon (purity 99.999%) during welding of 15 L / min. After cladding, the ferrite / martensitic steel samples with the cladding metal layer (the cladding layer thickness in Example 1 was 1.8 mm, the cladding layer thickness in Example 2 was 1.8 mm, and the cladding layer thickness in Example 3 was 2.1 mm) were heated at 550°C with oxygen controlled (oxygen content: 10 -6 ~5×10 -6 wt.%) in a liquid lead-bismuth solution (44.5wt.% Pb and 55.5wt.% Bi) for 3000h. After the corrosion experiment, the sample cross section was processed by wire cutting, and after mounting, the cross section was polished with 2000# sandpaper. The cross section morphology of the sample was observed by scanning electron microscopy. Figure 1 As shown in (a) to (c), it can be seen that the lead-free bismuth element penetrates into the cladding metal, and an oxide film is formed on the surface of the cladding metal layer, the thickness of which is less than 10 μm (the oxide film thickness in Example 1 is 4.0 μm; the oxide film thickness in Example 2 is 8.0 μm; the oxide film thickness in Example 3 is 8.0 μm). Figure 2 The element distribution on the cladding metal surface is shown. An oxygen- and silicon-rich layer forms on the cladding metal surface, while lead and bismuth elements are blocked by this oxygen- and silicon-rich layer. Therefore, the cladding metal effectively blocks the penetration of the lead-bismuth solution, protecting the base metal (9wt.% Cr ferrite / martensitic steel) from lead-bismuth corrosion.

[0039] In Comparative Example 1 and Comparative Example 2, the same cladding process parameters and corrosion test parameters as those in the embodiment are used, wherein the cladding layer thickness of Comparative Example 1 is 1.8 mm, and the cladding layer thickness of Comparative Example 2 is 2.0 mm. However, the composition of the cladding wire (diameter 1.6 mm) exceeds the scope of this patent application, specifically, the Si content is lower than the controlled component by 3.00 to 5.50 wt.%, and the Cr content is lower than the controlled component by 16.50 to 21.50 wt.%. Since Cr and Si are key elements for forming a dense oxide film, it is difficult to form a dense oxide layer during the lead-bismuth corrosion process. The cross-sectional morphology and Pb element distribution of the sample after corrosion are shown as follows: Figure 3 and Figure 4 As shown in the figure, it can be seen that lead and bismuth elements have penetrated into the cladding metal, with the maximum depth being about 800μm and 450μm respectively. Severe dissolution corrosion has occurred in the cladding metal.

[0040] Comparative Example 3 uses the same 9wt.% Cr ferrite / martensite steel plate as in Example 1. The main elements Si, Cr, Ni, etc. in its composition are not within the control range of this patent. The sample is placed in the same liquid lead-bismuth environment as in Example 1 for 3000 hours. The cross-sectional morphology of the sample after corrosion is as follows: Figure 5 As shown in Figure 2, it can be seen that a corrosion layer with a maximum thickness of about 45 μm is formed on the surface of the ferrite / martensite steel.

[0041] Table 1 summarizes the corrosion resistance of lead-bismuth solution (550°C, 3000h) in the above examples and comparative examples. -6 ~5×10 -6 After being placed in a liquid lead-bismuth (44.5wt.% Pb and 55.5wt.% Bi) solution for 3000h, the cladding metal exhibited excellent resistance to lead-bismuth corrosion. This was mainly attributed to the formation of a dense oxide film on the surface of the cladding metal, which effectively prevented the infiltration of the lead-bismuth solution, thereby effectively improving the liquid lead-bismuth corrosion resistance of the ferrite / martensitic steel.

[0042] Table 1 shows the corrosion resistance of lead-bismuth solution (550°C, 3000h) of the examples and comparative examples.

[0043]

Claims

1. A cladding material for improving the corrosion resistance of ferrite / martensitic steel to liquid lead and bismuth, characterized in that: The chemical composition of the cladding material consists of the following components in mass percentage: C≤0.12%, Si: 3.00~5.50%, Mn: 1.00~2.00%, P≤0.015%, S≤0.015%, Cr: 16.50~21.50%, Ni: 11.00~22.00%, Nb: 0.10~1.00%, Mo: 0.80~1.20%, N: 0.0035~0.005%, Fe balance.

2. The cladding material according to claim 1, wherein: The chemical composition of the cladding material is as follows in mass percentage: C≤0.12%, Si: 3.00~4.50%, Mn: 1.00~1.50%, P≤0.015%, S≤0.015%, Cr: 16.50~20.50%, Ni: 11.00~15.00%, Nb: 0.50~1.00%, Mo: 0.80~1.20%, N: 0.004~0.005%, Fe balance.

3. The cladding material according to claim 2, wherein: The chemical composition of the cladding material is as follows in mass percentage: C≤0.12%, Si: 3.00~4.00%, Mn: 1.00~1.30%, P≤0.010%, S≤0.010%, Cr: 16.50~18.50%, Ni: 11.00~13.00%, Nb: 0.70~1.00%, Mo: 0.80~1.20%, N: 0.004~0.045%, Fe balance.

4. Use of the cladding material according to any one of claims 1 to 3, characterized in that: A cladding metal layer is prepared on the surface of ferrite / martensitic steel by welding to prevent liquid lead and bismuth from corroding the ferrite / martensitic steel.

5. The use according to claim 4, characterized in that: The cladding material is solid wire with a wire diameter of 1.2mm to 2.0mm.

6. The use according to claim 4, characterized in that: The tungsten inert gas shielded welding method was adopted and pure Ar was used as the welding shielding gas to prepare the cladding layer on the surface of ferrite / martensitic steel.

7. The use according to claim 4, characterized in that: Tungsten inert gas shielded welding process parameters: welding current is 150~200A, welding voltage is 12~17V, welding speed is 70~120mm / min, and wire feeding speed is 700~1200mm / min.

8. The use according to claim 4 or 7, characterized in that: Current type / polarity: DC normal connection (DCEN), interpass temperature ≤ 100°C, shielding gas: Ar with a purity of ≥ 99.995%, and a shielding gas flow rate of 10 to 20 L / min during welding.

9. The use according to claim 4, characterized in that: The ferrite / martensitic steel is 9-12wt.% Cr ferrite / martensitic steel, and the matrix of the ferrite / martensitic steel is one of a plate, a bar or a pipe.

10. The use according to claim 4 or 9, characterized in that: The cladding metal layer has a thickness of 1.5 to 2.5 mm and is metallurgically bonded to the substrate without welding defects. After being corroded in a 550°C oxygen-controlled lead-bismuth solution for 3000 hours, the cladding metal layer has no lead-bismuth infiltration, and can effectively block liquid lead-bismuth corrosion.

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