A welding wire for ultra-low carbon heat-resistant steel in high-temperature environments, its application and welding method

Abstract

This invention discloses an ultra-low carbon heat-resistant steel welding wire for high-temperature environments and its application, belonging to the field of welding materials technology. The chemical composition of the welding wire (wt.%) is: C≤0.01%, Cr: 7.5-10.5%, Si: 0.2-0.6%, Ni: 0.4-1.0%, Mo≤0.1%, N: 0.06-0.15%, Nb≤0.01%, V: 0.10-0.30%, Mn: 0.80-1.80%, W: 1.40-2.60%, Cu≤0.08%, Co≤0.06%, P≤0.02%, S≤0.02%, with the balance being iron and unavoidable impurities. This welding wire is suitable for welding heat-resistant steel components used in high-temperature environments such as nuclear power or thermal power plants. It provides stable welding, minimal spatter, and good process performance. The use of the ultra-low carbon heat-resistant steel welding wire of the present invention for high-temperature environments can produce welds with excellent high-temperature performance, meeting the requirements of high-temperature long-term service environments.

Description

Technical Field

[0001] This invention relates to the field of welding materials technology, specifically to an ultra-low carbon heat-resistant steel welding wire for high-temperature environments (usable from room temperature to ≤600℃, preferably 450-600℃) and its application. This welding wire is used for welding components that are used for a long time in high-temperature environments such as nuclear power or thermal power plants. Background Technology

[0002] Ferritic-martensitic heat-resistant steel was developed in the 1930s. Due to its high allowable stress, high creep strength, high fatigue strength, high thermal conductivity, low thermal expansion coefficient, good weldability, good corrosion resistance, and moderate price, it has been widely used in petrochemical, energy (thermal power, nuclear power, etc.) fields. The development of ferritic-martensitic heat-resistant steel involved first increasing the content of the heat-resistant alloying element Cr, from the initial 2.25% to 9-12%; secondly, the addition of alloying elements such as V and Nb promoted a comprehensive improvement in its high-temperature performance. However, at temperatures above 580℃, austenitic stainless steel is usually the only alternative. Excessive use of stainless steel leads to increased manufacturing costs and reduced thermal conductivity, hindering its large-scale application. Different countries and regions are actively researching ferritic-martensitic heat-resistant steel. Compared with the base material of ferritic-martensitic heat-resistant steel, the development of its matching welding materials is relatively lagging behind. However, in-service testing of ferritic-martensitic heat-resistant steel components during high-temperature service shows that many problems originate from the failure and damage of welded joints. Welding materials are an important factor determining the performance of welded joints. Therefore, the development of high-quality matching welding materials is the prerequisite and foundation for the further promotion and application of ferritic-martensitic heat-resistant steel.

[0003] The performance of existing heat-resistant steel welding consumables, especially their high-temperature creep resistance, still lags behind that of the base metal. Under prolonged high-temperature conditions, they are highly susceptible to weld failure, impacting the overall lifespan of the welded components. To improve the performance of heat-resistant steel welding consumables, some thermal power plant heat-resistant steel welding consumables currently incorporate Co to slow element diffusion and strengthen through solid solution, thereby enhancing the steel's high-temperature performance and reducing M. 23C6 growth rate slows down martensite recovery during high-temperature tempering, thus improving high-temperature creep strength. Additionally, Cu is added to enhance the steel's strength, toughness, and atmospheric corrosion resistance. However, materials containing Co and Cu have significant detrimental effects in nuclear power applications. Co's large neutron absorption cross-section easily leads to the failure of Co-containing materials under neutron irradiation. Furthermore, the radioactive isotope 60Co has a long half-life of 5.26 years, and its impact increases with reactor operating time. This not only introduces radioactivity into reactor equipment and components but also makes pipelines, pumps, valves, and other equipment in the primary loop system radioactive. This will create numerous difficulties for the maintenance and waste disposal of nuclear reactor equipment and components, and may even endanger personal safety. Cu-containing steel forms Cu-rich precipitates under irradiation, a major mechanism causing embrittlement in nuclear power steel. Therefore, the Co and Cu content in nuclear power steel should be strictly limited. Consequently, heat-resistant steel welding materials designed for thermal power applications cannot be used in the nuclear power field. Currently, there is relatively little research worldwide on improving the high-temperature performance of heat-resistant steel welding materials. Ferritic-martensitic welding materials with excellent high-temperature performance and applicable to multiple fields such as energy (thermal power, nuclear power, etc.) and petrochemicals should be designed for long-term high-temperature service environments. Summary of the Invention

[0004] To address the issues of the relatively low high-temperature performance of existing domestic heat-resistant steel welding wires compared to their base materials and the limitations of their application environments, the present invention aims to provide an ultra-low carbon heat-resistant steel welding wire for high-temperature environments. This welding wire is suitable for welding key high-temperature structural components in fields such as energy (thermal power, nuclear power, etc.) and petrochemicals.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A high-temperature environment ultra-low carbon heat-resistant steel welding wire, the chemical composition of which is as follows by weight percentage:

[0007] C≤0.01%, Cr: 7.5-10.5%, Si: 0.2-0.6%, Ni: 0.4-1.0%, Mo≤0.1%, N: 0.06-0.15%, Nb≤0.01%, V: 0.10-0.30%, Mn: 0.80-1.80%, W: 1.40-2.60%, Cu≤0.08%, Co≤0.06%, P≤0.02%, S≤0.02%, balance being iron and unavoidable impurities.

[0008] Furthermore, the Cr content in the welding wire is preferably 7.5-8.5%, or 8.5-9.5%, or 9.5-10.5%.

[0009] Furthermore, the Si content in the welding wire is preferably 0.2-0.4%, or 0.4-0.6%.

[0010] Furthermore, the Ni content in the welding wire is preferably 0.4-0.6%, or 0.6-0.8%, or 0.8-1.0%.

[0011] Furthermore, the nitrogen content in the welding wire is preferably 0.06-0.09%, or 0.09-0.12%, or 0.12%-0.15%.

[0012] Furthermore, the V content in the welding wire is preferably 0.10-0.17%, or 0.17-0.23%, or 0.23-0.30%.

[0013] Furthermore, the Mn content in the welding wire is preferably 0.8-1.1%, or 1.0-1.4%, or 1.4-1.8%.

[0014] Furthermore, the W content in the welding wire is preferably 1.4-1.8%, or 1.8-2.2%, or 2.2-2.6%.

[0015] Furthermore, the Cu content in the welding wire is preferably Cu≤0.04%, or Cu≤0.02%, or Cu≤0.01%.

[0016] Furthermore, the Co content in the welding wire is preferably Co ≤ 0.03%, or Co ≤ 0.02%, or Co ≤ 0.01%.

[0017] Furthermore, the phosphorus (P) content in the welding wire is preferably P ≤ 0.01% or P ≤ 0.005%.

[0018] Furthermore, the sulfur content in the welding wire is preferably S≤0.01% or S≤0.005%.

[0019] The reasons for identifying the above chemical components are as follows:

[0020] The formation and coarsening of carbides within the weld during long-term high-temperature service are significant factors contributing to the deterioration of the weld's high-temperature performance. Reducing the carbon (C) content can significantly decrease the tendency for carbide formation and coarsening. Nitrogen (N) is an austenite-forming element that can inhibit the formation of δ-ferrite. In heat-resistant steel, δ-ferrite is a harmful structure that deteriorates the impact toughness and high-temperature creep properties of the weld metal. Nitrogen can also form carbides with v, which helps improve the high-temperature strength and stable microstructure of the heat-resistant steel weld. Increasing the nitrogen (N) content while reducing the carbon (C) content is beneficial for improving high-temperature performance. On the other hand, excessive nitrogen content can lead to the formation of the Z-phase (CrNbN phase), which deteriorates creep performance. Limiting the Nb content can inhibit the formation of the Z-phase; therefore, the C and N contents should be rationally configured. In this application, C ≤ 0.01%; N: 0.06-0.15%, preferably 0.06-0.09%, or 0.09-0.12%, or 0.12%-0.15%.

[0021] Si is a deoxidizer for weld metal, which can ensure the low-temperature impact toughness of weld metal to a certain extent, and can also improve the strength of the weld metal to a certain extent. When the ratio of Mn to Si is appropriate, its deoxidation effect reaches the optimal state, which can greatly improve the comprehensive mechanical properties of the weld metal. However, excessive Si and Mn will promote the segregation of P, increase the temper brittleness sensitivity of weld metal, and excessive Si content will also drastically increase the tendency to form hot cracks during welding and hot embrittlement. In addition, Si tends to preferentially segregate to dislocations and grain boundaries. Therefore, excessive Si under irradiation environment can easily cause irradiation embrittlement or lead to the precipitation of silicon-rich phases. Excessive Si will also promote the formation of high-temperature δ-ferrite, deteriorating the weld performance. Therefore, the Si content in heat-resistant steel welding materials should be reasonably controlled within a certain range. In this application, Si is 0.2-0.6%, preferably 0.2-0.4%, or 0.4-0.6%.

[0022] Mn is an austenitizing element. Increasing the Mn content in heat-resistant steel can suppress the formation of high-temperature δ-ferrite, but it also lowers the Al transformation temperature and reduces the high-temperature stability of the ferrite matrix. When the Mn content is too high, Mn segregation will occur, forming MnS defects and deteriorating performance. An appropriate amount of Mn can ensure that the material has high strength while also having high low-temperature impact toughness and strong crack resistance. Therefore, Mn is an indispensable alloying element. In this application, Mn is 0.80-1.80%, preferably 0.8-1.1%, or 1.0-1.4%, or 1.4-1.8%.

[0023] Cr is one of the essential elements for ferritic-martensitic heat-resistant steel to resist high-temperature oxidation and corrosion. Cr can improve the oxidation resistance and corrosion resistance of materials. Cr dissolves in the matrix and plays a role in solid solution strengthening. At the same time, it improves the hardenability of heat-resistant steel and reduces the critical cooling rate of heat-resistant steel, allowing it to obtain a full martensitic structure at a lower cooling rate. However, excessive Cr content in steel will promote the formation of high-temperature δ-ferrite and lead to coarsening of the corresponding carbide precipitates, thus having adverse effects. In this application, Cr is 7.5-10.5%, preferably 7.5-8.5%, or 8.5-9.5%, or 9.5-10.5%.

[0024] W is also an important alloying element in ferritic-martensitic heat-resistant steel. Its main function is to improve the comprehensive mechanical properties of steel. W is one of the most important alloying elements for improving hot strength, and its effect is stronger than that of Mo. At the same time, its tendency to promote the formation of δ-ferrite is lower than that of Mo. Therefore, more W can be added to further improve the hot strength of the weld. However, if the W content is too high, it will form the Laves phase and deteriorate the performance. Therefore, its upper and lower limits should be limited. In this application, W is 1.4-2.6%, preferably 1.4-1.8%, or 1.8-2.2%, or 2.2-2.6%.

[0025] Ni is an austenitizing element, similar to Mn. Increasing the Ni content in heat-resistant steel can suppress the formation of high-temperature δ-ferrite, but it also lowers the Al transformation temperature and reduces the high-temperature stability of the ferrite matrix. Increasing the Ni content can improve toughness, but it reduces the stability of carbonitrides, accelerates the coarsening of precipitates, reduces tempering resistance (tempering stability, tempering resistance), and leads to deterioration of creep performance. In addition, under the influence of irradiation, Ni is also an important source of helium formation. In this application, Ni is 0.4-1.0%, preferably 0.4-0.6%, or 0.6-0.8%, or 0.8-1.0%.

[0026] The main role of V and Nb in heat-resistant steel is to strengthen the steel by generating fine and uniformly distributed carbonitride particles through appropriate heat treatment. Nb can improve the high-temperature strength and creep resistance of steel, but it is detrimental to the plasticity and low-temperature toughness of the weld. Furthermore, Nb reacts with N to form the Z phase (CrNbN phase), which worsens creep performance. Therefore, its content in the weld should be controlled to ensure both improved high-temperature strength and good plasticity and toughness. In this application, V is 0.10-0.30%, preferably 0.10-0.17%, or 0.17-0.23%, or 0.23-0.30%; Nb ≤ 0.01%.

[0027] Sulfur (S) and phosphorus (P) are harmful impurities in steel, mostly introduced during steelmaking from raw materials, and should be minimized. During welding, inadequate beveling can also increase S content. Excessive P content increases the tendency for cold cracking, while excessive S content increases the tendency for hot cracking. Therefore, the S and P content in the welding wire's chemical composition should be strictly controlled. In this application, S ≤ 0.02%, preferably S ≤ 0.01%, or S ≤ 0.005%; P ≤ 0.02%, preferably P ≤ 0.01%, or P ≤ 0.005%.

[0028] Co has a large neutron absorption cross section, which can easily cause Co-containing materials to fail under neutron irradiation. Moreover, the half-life of the radioactive isotope 60Co is as long as 5.26 years. Its impact will increase with the increase of reactor operating time. It not only introduces radioactivity into the equipment and components inside the reactor, but also makes the pipelines, pumps, valves and other equipment in the primary loop system radioactive. This will bring many difficulties to the maintenance of nuclear reactor equipment and components and waste disposal, and may even endanger personal safety. Therefore, the Co content should be strictly limited. In this application, Co ≤ 0.06%, preferably Co ≤ 0.03%, or Co ≤ 0.02%, or Co ≤ 0.01%.

[0029] Under irradiation, Cu forms a Cu-rich precipitate phase, which is a major mechanism for the embrittlement of nuclear power steel. Therefore, the Cu content should be strictly limited. In this application, Cu ≤ 0.08%, preferably Cu ≤ 0.04%, or Cu ≤ 0.02%, or Cu ≤ 0.01%.

[0030] The present invention discloses an ultra-low carbon heat-resistant steel welding wire for high-temperature environments, which can be produced by vacuum induction furnace smelting or by electric furnace smelting and ladle refining, as long as the final chemical composition of the welding wire meets the above requirements.

[0031] The welding wire of this invention is applied to the welding of key high-temperature structural components in the fields of energy (thermal power, nuclear power, etc.) and petrochemicals. The welding process is as follows: take a Φ1.2mm welding wire, use TIG welding, and the joint type is butt joint. The welding parameters are: welding current 150-240A, arc voltage 10-15V, DC positive polarity, welding speed 0.05-0.15m / min, arc protection using high-purity argon gas with a purity ≥99.995%, and argon gas flow rate 12-30L / min; weld the test piece using a multi-layer, multi-pass deposition method, with a preheating temperature of 150-260℃ before welding and an interpass temperature of 150-260℃ during welding, and perform annealing heat treatment at 750±10℃ after welding for 2.5±1h.

[0032] The room temperature tensile property requirement for the weld metal of this invention is: yield strength Rp 0.2 ≥410MPa, tensile strength R m ≥620MPa, elongation A≥16%; room temperature impact energy KV2≥47J; high temperature tensile properties of weld metal: 550℃: Rp 0.2 ≥269MPa, R m ≥379MPa; Weld metal microstructure requirements: full martensitic structure, without δ-ferrite.

[0033] The welding wire of this invention is suitable for welding heat-resistant steel components used in high-temperature environments such as nuclear power or thermal power plants. The welding process is stable, with minimal spatter and good process performance. Welding with this invention's ultra-low carbon heat-resistant steel welding wire for high-temperature environments yields welds with excellent high-temperature performance, meeting the requirements of long-term high-temperature service environments.

[0034] The present invention has the following advantages:

[0035] 1. The ultra-low carbon heat-resistant steel welding wire for high-temperature environments of this invention possesses excellent high-temperature mechanical properties, a low coefficient of thermal expansion, high thermal conductivity (which can reduce stress caused by thermal fatigue in components), high strength and toughness, and excellent resistance to radiation swelling. It can be used for welding key high-temperature structural components in energy (thermal power, nuclear power, etc.), petrochemical, and other fields. The welding wire of this invention contains ≤0.01% C, which inhibits the formation and coarsening tendency of carbides during long-term high-temperature service, improving long-term high-temperature performance. The addition of 0.06-0.15% N compensates for the strength decrease caused by the reduced C content and inhibits the formation of high-temperature δ-ferrite. These two points are crucial for improving the overall performance of heat-resistant steel welds.

[0036] 2. This invention fully considers the unique characteristics of weld metal in nuclear reactors, which must withstand the deteriorating effects of high radiation, while also addressing weld life under high temperature and stress conditions. In addition to strict control over the content of C and Cr, the contents of Ni, Mn, W, and Nb are also precisely controlled: by limiting the Ni content in the welding wire to 0.4-1.0%, nitride coarsening during long-term high-temperature service can be effectively suppressed, improving the high-temperature long-term performance of the weld. Increasing the Mn content in the welding wire to 0.80-1.80% suppresses the tendency for high-temperature δ-ferrite formation caused by reduced Ni content, improving the impact toughness and high-temperature creep resistance of the weld. The welding wire of this invention adds 1.4-2.6% W. W has a stronger effect on improving the heat resistance of the weld than Mo, and its tendency to promote δ-ferrite formation is lower than that of Mo. Therefore, more W can be added to further improve the high-temperature performance of the weld. The Nb content in the welding wire of this invention is controlled to be ≤0.01%. This is because a relatively high N content is added to the welding wire. During long-term high-temperature service, Nb and N will form a Z phase (NiNbN phase), which deteriorates the creep performance. The Nb content in the weld should be controlled to ensure the high-temperature long-term performance of the weld.

[0037] Furthermore, considering nuclear applications, the welding wire of this invention does not contain Co and Cu, and reduces the generation of long-lived radioactive isotope 60Co by limiting the content of impurity Co to below 0.06%, and suppresses irradiation embrittlement of weld metal by limiting the content of impurity Cu to below 0.08%.

[0038] 3. This invention provides a solid ultra-low carbon heat-resistant steel welding wire for high-temperature environments. When welding under inert gas protection, it effectively prevents weld oxidation, reduces inclusions in the weld, and improves weld quality. It effectively avoids slag contamination and quality degradation of the weld during the welding of heat-resistant steel welding electrodes and flux-cored wires. Experiments show that when using the heat-resistant steel welding wire of this invention in conjunction with the welding process defined in this invention, spatter is minimal, the process is stable, and the process performance is good; moreover, it can obtain weld metal with the required properties, especially with good high-temperature performance.

[0039] 4. Experiments show that the weld metal of the ultra-low carbon heat-resistant steel welding wire for high-temperature environments of this invention meets the following performance requirements: Weld metal room temperature performance requirements: Yield strength Rp 0.2 ≥410MPa, tensile strength R m ≥620MPa, elongation ≥16%; room temperature impact energy KV2 ≥47J; high temperature tensile properties of weld metal: 550℃: Rp 0.2 ≥269MPa, R m ≥379MPa; Weld metal microstructure requirements: full martensitic structure, without δ-ferrite. Attached Figure Description

[0040] Figure 1 This is the welding joint form of the present invention. Detailed Implementation

[0041] The present invention discloses an ultra-low carbon heat-resistant steel welding wire for high-temperature environments, which can be produced by vacuum induction furnace smelting or by electric furnace smelting and ladle refining, as long as the final chemical composition of the welding wire meets the specified welding wire composition; in addition, the entire smelting and processing process of the welding wire is no different from that of ordinary alloy steel welding wire.

[0042] Taking Φ1.2mm welding wire as an example, the weld metal of Φ1.2mm welding wire is prepared by multi-layer, multi-pass TIG (automatic tungsten inert gas welding). The base material is P91 heat-resistant steel, and the joint type is 20mm thick plate butt welding. The welding parameters are: welding current 150-220A (specifically 180A in this case), arc voltage 10-15V (specifically 12-13V in this case), DC positive polarity, and welding speed 0.06-0.1. The welding speed is 5 m / min (0.10 m / min in this case), and the arc protection uses high-purity argon gas with a purity ≥99.995%, with an argon flow rate of 12-30 L / min (25 L / min in this case). The preheating temperature before welding and the interpass temperature during welding are 150-260℃ (180-200℃ in this case). After welding, annealing heat treatment is performed at 750±10℃ for 2.5±1 h (2.5 h in this case). Samples are then taken from the weld metal for mechanical property analysis. Of course, the welding parameters of this application can be adjusted for different welding wire diameters.

[0043] Example 1:

[0044] The chemical composition (by weight) of the ultra-low carbon heat-resistant steel welding wire used in this high-temperature environment is as follows:

[0045] C: 0.0043%, Cr: 8.90%, Si: 0.401%, Ni: 0.75%, Mo: 0.067%, N: 0.11%, Nb < 0.005%, V: 0.22%, Mn: 1.38%, W: 1.98%, P: 0.004%, S: 0.0015%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0046] Example 2:

[0047] The chemical composition (by weight) of the ultra-low carbon heat-resistant steel welding wire used in this high-temperature environment is as follows:

[0048] C: 0.01%, Cr: 8.98%, Si: 0.39%, Ni: 0.71%, Mo: 0.058%, N: 0.11%, Nb < 0.005%, V: 0.21%, Mn: 1.31%, W: 1.97%, P: 0.005%, S: 0.0016%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0049] Example 3:

[0050] The chemical composition (by weight) of the ultra-low carbon heat-resistant steel welding wire used in this high-temperature environment is as follows:

[0051] C: 0.0042%, Cr: 8.95%, Si: 0.20%, Ni: 0.75%, Mo: 0.049%, N: 0.12%, Nb < 0.005%, V: 0.20%, Mn: 1.29%, W: 1.97%, P: 0.005%, S: 0.0016%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0052] Example 4:

[0053] The chemical composition (by weight) of the ultra-low carbon heat-resistant steel welding wire used in this high-temperature environment is as follows:

[0054] C: 0.0048%, Cr: 8.85%, Si: 0.60%, Ni: 0.74%, Mo: 0.051%, N: 0.10%, Nb < 0.005%, V: 0.23%, Mn: 1.31%, W: 2.01%, P: 0.004%, S: 0.0015%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0055] Example 5:

[0056] The chemical composition (by weight) of the ultra-low carbon heat-resistant steel welding wire used in this high-temperature environment is as follows:

[0057] C: 0.0039%, Cr: 9.01%, Si: 0.43%, Ni: 0.40%, Mo: 0.068%, N: 0.11%, Nb < 0.005%, V: 0.22%, Mn: 1.26%, W: 1.98%, P: 0.005%, S: 0.0014%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0058] Example 6:

[0059] The chemical composition (by weight) of the ultra-low carbon heat-resistant steel welding wire used in this high-temperature environment is as follows:

[0060] C: 0.0041%, Cr: 8.87%, Si: 0.41%, Ni: 1.0%, Mo: 0.057%, N: 0.09%, Nb < 0.005%, V: 0.23%, Mn: 1.30%, W: 2.05%, P: 0.005%, S: 0.0014%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0061] Example 7:

[0062] The chemical composition (by weight) of the ultra-low carbon heat-resistant steel welding wire used in this high-temperature environment is as follows:

[0063] C: 0.0041%, Cr: 7.5%, Si: 0.45%, Ni: 0.75%, Mo: 0.059%, N: 0.11%, Nb < 0.005%, V: 0.21%, Mn: 1.31%, W: 2.15%, P: 0.004%, S: 0.0013%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0064] Example 8:

[0065] The chemical composition (by weight) of the ultra-low carbon heat-resistant steel welding wire used in this high-temperature environment is as follows:

[0066] C: 0.0038%, Cr: 10.5%, Si: 0.48%, Ni: 0.68%, Mo: 0.061%, N: 0.10%, Nb < 0.005%, V: 0.22%, Mn: 1.25%, W: 1.95%, P: 0.005%, S: 0.001%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0067] Example 9:

[0068] The chemical composition (by weight) of the ultra-low carbon heat-resistant steel welding wire used in this high-temperature environment is as follows:

[0069] C: 0.0045%, Cr: 8.96%, Si: 0.45%, Ni: 0.78%, Mo: 0.10%, N: 0.11%, Nb < 0.005%, V: 0.21%, Mn: 1.25%, W: 2.14%, P: 0.005%, S: 0.0015%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0070] Example 10:

[0071] The chemical composition (by weight) of the ultra-low carbon heat-resistant steel welding wire used in this high-temperature environment is as follows:

[0072] C: 0.0038%, Cr: 9.06%, Si: 0.32%, Ni: 0.70%, Mo: 0.068%, N: 0.10%, Nb: 0.01%, V: 0.21%, Mn: 1.40%, W: 2.02%, P: 0.005%, S: 0.00173%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0073] Example 11:

[0074] The chemical composition (by weight) of the ultra-low carbon heat-resistant steel welding wire used in this high-temperature environment is as follows:

[0075] C: 0.0035%, Cr: 9.11%, Si: 0.39%, Ni: 0.75%, Mo: 0.062%, N: 0.12%, Nb < 0.005%, V: 0.24%, Mn: 1.30%, W: 1.40%, P: 0.005%, S: 0.0015%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0076] Example 12:

[0077] The chemical composition (by weight) of the ultra-low carbon heat-resistant steel welding wire used in this high-temperature environment is as follows:

[0078] C: 0.0041%, Cr: 8.98%, Si: 0.31%, Ni: 0.65%, Mo: 0.065%, N: 0.11%, Nb < 0.005%, V: 0.22%, Mn: 1.27%, W: 2.60%, P: 0.005%, S: 0.001%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0079] Example 13:

[0080] The chemical composition (by weight) of the ultra-low carbon heat-resistant steel welding wire used in this high-temperature environment is as follows:

[0081] C: 0.0038%, Cr: 8.88%, Si: 0.32%, Ni: 0.75%, Mo: 0.055%, N: 0.06%, Nb < 0.005%, V: 0.21%, Mn: 1.32%, W: 2.10%, P: 0.004%, S: 0.0015%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0082] Example 14:

[0083] The chemical composition (by weight) of the ultra-low carbon heat-resistant steel welding wire used in this high-temperature environment is as follows:

[0084] C: 0.0040%, Cr: 8.71%, Si: 0.41%, Ni: 0.71%, Mo: 0.062%, N: 0.15%, Nb < 0.005%, V: 0.22%, Mn: 1.40%, W: 1.95%, P: 0.005%, S: 0.0012%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0085] Example 15:

[0086] The chemical composition (by weight) of the ultra-low carbon heat-resistant steel welding wire used in this high-temperature environment is as follows:

[0087] C: 0.0042%, Cr: 8.81%, Si: 0.38%, Ni: 0.65%, Mo: 0.064%, N: 0.11%, Nb < 0.005%, V: 0.10%, Mn: 1.38%, W: 1.99%, P: 0.005%, S: 0.0017%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0088] Example 16:

[0089] The chemical composition (by weight) of the ultra-low carbon heat-resistant steel welding wire used in this high-temperature environment is as follows:

[0090] C: 0.0038%, Cr: 8.92%, Si: 0.39%, Ni: 0.70%, Mo: 0.065%, N: 0.10%, Nb < 0.005%, V: 0.30%, Mn: 1.40%, W: 2.09%, P: 0.005%, S: 0.0014%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0091] Example 17:

[0092] The chemical composition (by weight) of the ultra-low carbon heat-resistant steel welding wire used in this high-temperature environment is as follows:

[0093] C: 0.0042%, Cr: 8.75%, Si: 0.40%, Ni: 0.74%, Mo: 0.061%, N: 0.12%, Nb < 0.005%, V: 0.20%, Mn: 0.80%, W: 2.02%, P: 0.005%, S: 0.0013%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0094] Example 18:

[0095] The chemical composition (by weight) of the ultra-low carbon heat-resistant steel welding wire used in this high-temperature environment is as follows:

[0096] C: 0.0037%, Cr: 9.05%, Si: 0.36%, Ni: 0.65%, Mo: 0.069%, N: 0.11%, Nb < 0.005%, V: 0.18%, Mn: 1.80%, W: 2.10%, P: 0.004%, S: 0.0012%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0097] Comparative Example 1:

[0098] The chemical composition (by weight) of heat-resistant steel welding wire is as follows:

[0099] C: 0.080%, Cr: 8.92%, Si: 0.44%, Ni: 0.78%, Mo: 0.087%, N: 0.11%, Nb < 0.005%, V: 0.22%, Mn: 1.28%, W: 2.15%, P: 0.005%, S: 0.0015%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0100] Comparative Example 2:

[0101] The chemical composition (by weight) of heat-resistant steel welding wire is as follows:

[0102] C: 0.0045%, Cr: 8.95%, Si: 0.41%, Ni: 0.65%, Mo: 0.069%, N: 0.04%, Nb < 0.005%, V: 0.21%, Mn: 1.24%, W: 2.04%, P: 0.005%, S: 0.0015%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0103] Comparative Example 3:

[0104] The chemical composition (by weight) of heat-resistant steel welding wire is as follows:

[0105] C: 0.0037%, Cr: 8.65%, Si: 0.43%, Ni: 0.69%, Mo: 0.071%, N: 0.09%, Nb < 0.005%, V: 0.22%, Mn: 1.37%, W: 2.80%, P: 0.005%, S: 0.0016%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0106] Comparative Example 4:

[0107] The chemical composition (by weight) of heat-resistant steel welding wire is as follows:

[0108] C: 0.0038%, Cr: 5.99%, Si: 0.31%, Ni: 0.65%, Mo: 0.068%, N: 0.10%, Nb < 0.005%, V: 0.21%, Mn: 1.29%, W: 2.10%, P: 0.005%, S: 0.0016%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0109] Comparative Example 5:

[0110] The chemical composition (by weight) of heat-resistant steel welding wire is as follows:

[0111] C: 0.0042%, Cr: 9.12%, Si: 0.35%, Ni: 0.75%, Mo: 0.066%, N: 0.11%, Nb < 0.005%, V: 0.23%, Mn: 0.41%, W: 2.04%, P: 0.005%, S: 0.0015%, Co < 0.01%, Cu < 0.01%, with the remainder being iron and unavoidable impurities.

[0112] Table 1. Results of room temperature tensile and impact properties tests for the Examples and Comparative Examples

[0113]

[0114]

[0115] Table 2. Tensile property test results at 550℃ for the Examples and Comparative Examples

[0116]

[0117]

[0118] Table 3 Weld microstructure of the Examples and Comparative Examples

[0119]

[0120] The welding test conditions for the above embodiments and comparative examples are shown in Table 4, and the types of welded joints used are as follows: Figure 1 As shown.

[0121] Table 4 Welding Test Conditions

[0122]

[0123]

[0124] The performance design requirements of this invention for the weld metal of ultra-low carbon heat-resistant steel welding wire for high-temperature environments are as follows:

[0125] Room temperature tensile property requirements for weld metal: Yield strength Rp 0.2 ≥410MPa, tensile strength R m ≥620MPa, elongation A≥16%; room temperature impact energy KV2≥47J; high temperature tensile properties of weld metal: 550℃: Rp 0.2 ≥269MPa, R m ≥379MPa; Weld metal microstructure requirements: fully martensitic, without δ-ferrite. The standard for room temperature tensile properties is GB / T2652-2008, the standard for high temperature tensile properties is GB / T 228.2-2015, and the standard for room temperature impact properties is GB / T2650-2008.

[0126] As can be seen from Examples 1-18, Comparative Examples 1-5, and Table 1-3:

[0127] The chemical composition of the welding wire designed using this invention, as shown in Examples 1-18, is within the scope of the technical solution of this invention, and the weld metal meets the performance design requirements of this invention. In Comparative Example 1, the C content of the welding wire is 0.08%, which is outside the scope of the technical solution of this invention (C≤0.01%). The increased C content reduces the toughness and plasticity of the weld, resulting in a room temperature elongation of 14.5% and a room temperature impact energy of 38J. Both elongation and impact energy do not meet the design requirements of this invention (room temperature elongation A≥16%; room temperature impact energy KV2≥47J). In Comparative Example 2, the N content of the welding wire is 0.04%, which is outside the scope of the technical solution of this invention (N: 0.06-0.15%). The decreased N content promotes δ-ferrite, resulting in a weld metal microstructure containing 3.5% ferrite. The δ-ferrite content in Comparative Example 3 was 2.80%, which is outside the scope of the present invention (W: 1.40-2.60%). Increased W content reduced weld plasticity and promoted δ-ferrite formation, resulting in a room temperature elongation of 15.0% in the weld metal. The weld metal microstructure contained 2.1% δ-ferrite, and both elongation and δ-ferrite content failed to meet the design requirements of the present invention (room temperature elongation A ≥ 16%; weld metal microstructure is full martensitic, without δ-ferrite). In Comparative Example 4, the Cr content in the welding wire was 5.99%, which is outside the scope of the present invention (Cr: 7.5-10.5%). Decreased Cr content worsened the high-temperature strength of the weld, leading to a decrease in the 550°C tensile strength R of the weld metal. m The value is 371 MPa, which does not meet the design requirements of this invention (tensile strength R at 550℃). m ≥379MPa). In Comparative Example 5, the Mn content of the welding wire was 0.41%, which is outside the scope of the technical solution of the present invention (Mn: 0.80-1.8%). The reduced Mn content promotes the formation of δ-ferrite, resulting in the weld metal microstructure containing 3.9% δ-ferrite, which does not meet the design requirements of the present invention (the weld metal microstructure is a full martensitic microstructure without δ-ferrite).

Claims

1. A type of ultra-low carbon heat-resistant steel welding wire, characterized in that: The chemical composition of this welding wire, by weight percentage, is as follows: C < 0.01%, Cr: 7.5-9.11%, Si: 0.2-0.6%, Ni: 0.4-1.0%, Mo < 0.1%, N: 0.09-0.15%, Nb < 0.01%, V: 0.10-0.30%, Mn: 0.80-1.80%, W: 1.40-2.60%, Cu ≤ 0.04%, Co ≤ 0.03%, P ≤ 0.02%, S ≤ 0.02%, balance being iron and unavoidable impurities; Using this welding wire to perform TIG welding on heat-resistant steel components, followed by annealing at 750±10℃ for 2.5±1h, the resulting weld metal microstructure is a fully martensitic structure without δ-ferrite.

2. The welding wire according to claim 1, characterized in that, The elemental composition of the welding wire is one or more of the following a-g: a. The Cr content in the welding wire is further set to Cr: 7.5%-8.5%, or further set to Cr: greater than 8.5%-9.11%; b. The Si content in the welding wire is further set to Si: greater than 0.2%-0.4%, or further set to Si: greater than 0.4%-0.6%; c. The Ni content in the welding wire is further set to Ni: 0.4%-0.6%, or further set to Ni: 0.6%-0.8%, or further set to Ni: 0.8%-1.0%; d. The nitrogen content in the welding wire is further set to N: 0.09%-0.12%, or further set to N: 0.12%-0.15%; e. The V content in the welding wire is further set to V: 0.10%-0.17%, or further set to V: 0.17%-0.23%, or further set to V: 0.23%-0.30%; f. The Mn content in the welding wire is further set to Mn: 0.8%-1.1%, or further set to Mn: 1.4%-1.8%; g. The W content in the welding wire is further set to W: 1.4%-1.8%, or further set to W: 1.8%-2.2%, or further set to W: 2.2%-2.6%.

3. The welding wire according to claim 1 or 2, characterized in that, The elemental composition of the welding wire is one or more of the following a-d conditions: a. The Cu content in the welding wire is further set to Cu≤0.02%; b. The Co content in the welding wire is further set to Co ≤ 0.02%; c. The phosphorus (P) content in the welding wire is further set to P ≤ 0.01%; d. The sulfur content in the welding wire is further set to S≤0.01%.

4. The application of the ultra-low carbon heat-resistant steel welding wire according to any one of claims 1-3, characterized in that: This welding wire is used for welding heat-resistant steel components that are used for extended periods in high-temperature environments in the nuclear power or thermal power industries.

5. A welding method for ultra-low carbon heat-resistant steel welding wire according to any one of claims 1-3, characterized in that: The welding process uses TIG welding, with a butt joint, a welding current of 150-240A, an arc voltage of 10-15V, a DC positive polarity, and a welding speed of 0.05-0.15m / min.

6. The welding method according to claim 5, characterized in that: The specimens were welded using a multi-layer, multi-pass fusion method, with a preheating temperature of 150~260℃ and an interpass temperature of 150~260℃ during the welding process.

7. The welding method according to claim 5, characterized in that: Welding wire with a specification of Φ1.2mm was selected for the welding process.

8. The welding method according to claim 5, characterized in that: During the welding process, high-purity argon gas with a purity of ≥99.995% is used for arc protection, with an argon gas flow rate of 12-30L / min.

9. The welding method according to any one of claims 5-8, characterized in that: The properties of the weld metal obtained after welding are as follows: The weld metal properties at room temperature are: yield strength Rp 0.2 ≥410MPa, tensile strength R m ≥620MPa, elongation A≥16%; The room temperature impact energy of the weld metal is KV2≥47J.

10. The welding method according to any one of claims 5-8, characterized in that: The high-temperature tensile properties of the weld metal are: 550℃: Rp 0.2 ≥269MPa, R m ≥379MPa.

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