A welding wire for a bainite steel rail joint and a welding method thereof

Abstract

A welding wire for repairing bainitic steel frogs and its welding method are provided. The welding wire composition is as follows: C: 0.1-0.3 wt.%, Mn: 3.0-4.0 wt.%, Si: 2.0-3.0 wt.%, P: ≤0.03 wt.%, S: ≤0.03 wt.%, Cr: 1.0-2.0 wt.%, Nb: 0.3-0.5 wt.%, Ni: 0.1-0.3 wt.%, B: 0.3-0.5 wt.%, with the balance being Fe. The welding method is CO2 gas shielded welding. After each welding pass, 10-20% NaCl brine is poured onto the weld. After the previous weld pass is rapidly cooled to room temperature, the next repair welding pass is performed. This invention, through the pioneering and independent development of repair welding wire, combined with corresponding welding methods and control of welding parameters, can obtain the optimal weld structure; the repair welding area of ​​the fork is free of welding defects such as cracks, inclusions, and porosity; as the first research in China on the welding method for repair welding of bainitic steel rails, it has broadened its application in more fields, and no preheating is required before welding, and no cracks will be generated without post-weld treatment, resulting in good weld structure performance.

Description

Technical Field

[0001] This invention belongs to the field of welding technology, specifically relating to a welding wire for repair welding of bainitic steel frogs and its welding method. Background Technology

[0002] Currently, the welding technology for repairing high-manganese steel frogs has become increasingly mature, but research on welding repairing damaged bainitic steel frogs is relatively limited. Because the microstructure of bainitic steel is difficult to obtain through welding, and there are no proven welding materials and processes for bainitic steel frogs, the current approach for severely damaged bainitic steel frog cores is replacement, resulting in high maintenance costs and significant material waste. With the increasing prevalence of bainitic alloy steel frog products, the development, preparation, and process research of welding materials for repairing bainitic steel frogs are of great significance. Therefore, the following technical solution is proposed. Summary of the Invention

[0003] The technical problem solved by this invention is to provide a welding wire for repair welding of bainitic steel frogs and a welding method thereof, filling the technical gap in welding materials and welding methods for repair welding of bainitic steel frogs.

[0004] The technical solution adopted in this invention is: a welding wire for repairing bainitic steel frogs, wherein the welding wire composition is: C: 0.1-0.3 wt.%, Mn: 3.0-4.0 wt.%, Si: 2.0-3.0 wt.%, P: ≤0.03 wt.%, S: ≤0.03 wt.%, Cr: 1.0-2.0 wt.%, Nb: 0.3-0.5 wt.%, Ni: 0.1-0.3 wt.%, B: 0.3-0.5 wt.%, with the balance being Fe.

[0005] In the above technical solution, further: the welding wire is a flux-cored welding wire with a diameter of φ0.8~1.8mm.

[0006] The present invention also claims protection for a welding method for bainitic steel frogs, wherein the welding method uses the welding wire described in any of the preceding claims, and the welding method is as follows: after each welding pass, 10-20% NaCl brine is poured onto the weld, and after the previous weld has cooled rapidly to room temperature, the next welding pass is performed.

[0007] In the above technical solution, the welding method is CO2 gas shielded welding, and the external current of CO2 gas shielded welding is 150-180A, and the arc voltage is 20-30V.

[0008] In the above technical solution, further: the bainitic steel frog welded by the welding method has the following composition: C: 0.1-0.4 wt.%, Si: 0.7-1.5 wt.%, Mn: 1.0-2.5 wt.%, Cr: 1.0-1.5 wt.%, Ni: 1.0-1.5 wt.%, Mo: 1.0-1.5 wt.%, Cu: 0.01-0.3 wt.%, P: <0.03 wt.%, S: <0.03 wt.%, with the balance being Fe and unavoidable impurities.

[0009] Advantages of this invention compared to existing technologies:

[0010] 1. The welding wire of this invention, combined with the corresponding welding method, can achieve the best weld structure when welding bainitic steel frogs. Moreover, the weld repair area of ​​the frog is free from welding defects such as cracks, inclusions, and porosity. This not only broadens the application of welding wire in more fields, but also makes the welding method easy to operate and implement, and is suitable for promotion.

[0011] 2. The welding wire for repairing bainitic steel frogs of the present invention has high strength, improved toughness and wear resistance, enhanced fatigue resistance, excellent adaptability to welding process, and reliable low-temperature performance.

[0012] 3. The welding wire diameter design of this invention improves welding efficiency, increases deposition speed by 20% to 30%, significantly shortens welding time, ensures reliable weld quality, and significantly reduces rework rate; the arc is stable, suitable for all-position welding such as flat welding, vertical welding, horizontal welding and overhead welding, and is especially suitable for repair welding; it supports high-speed and high-efficiency welding, reducing labor costs.

[0013] 4. The welding method of this invention achieves three core advantages in the repair welding of bainitic steel turnouts: refined microstructure, optimized performance, and controllable process through the innovative design of forced cooling with 10-20% NaCl brine and room temperature waiting between passes.

[0014] 5. This invention limits the welding method to CO2 gas shielded welding and specifies the parameter range of 150-180A external current and 20-30V arc voltage, which can prevent spatter from getting stuck in the wheel-rail contact surface and ensure driving safety; improve welding efficiency and significantly shorten maintenance time; the weld surface is smooth and the reinforcement height is uniform, without defects such as undercut and lack of fusion; the molten pool protection effect is good, reducing hydrogen porosity and avoiding grain coarsening and increased crack sensitivity caused by excessive current; combined with rapid cooling characteristics, it complements the brine cooling process, further refining the weld microstructure, and the wear resistance is better than that of high manganese steel frogs; under this parameter range, the residual tensile stress of the weld is significantly reduced, reducing the risk of stress corrosion cracking during service; the energy consumption for single frog maintenance is reduced by 40%-50% compared with traditional manual arc welding; this parameter range can give full play to the metallurgical effect of alloying elements in flux-cored wire, ensuring that the weld metal composition is highly matched with the base metal and avoiding performance degradation due to component dilution.

[0015] 6. The bainitic steel frog composition design of this invention improves strength, toughness, and wear resistance, optimizes welding process adaptability, and enhances fatigue resistance. Attached Figure Description

[0016] Figure 1 This is a macroscopic morphology diagram of a single weld pass in the repair welding area of ​​the present invention;

[0017] Figure 2 This is a low-magnification optical microstructure image of the weld repair area in this invention.

[0018] Figure 3 This is a high-magnification optical microstructure image of the weld repair area in this invention. Detailed Implementation

[0019] The following will refer to the appendices in the embodiments of the present invention. Figure 1-3 The technical solutions in the embodiments of the present invention are clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: A welding wire for repairing bainitic steel frogs, wherein the welding wire composition is C: 0.1 wt.%, Mn: 3.0 wt.%, Si: 2.0 wt.%, P: 0.005 wt.%, S: 0.005 wt.%, Cr: 1.0 wt.%, Nb: 0.3 wt.%, Ni: 0.1 wt.%, B: 0.3 wt.%, with the balance being Fe.

[0021] In the above embodiments, the welding wire is further described as a flux-cored welding wire with a diameter of φ0.8mm.

[0022] This invention also claims protection for a welding method for bainitic steel frogs, wherein the welding method uses the aforementioned welding wire and the welding method is as follows: after each welding pass, 10% NaCl brine is poured onto the weld, and after the previous weld has cooled rapidly to room temperature, the next welding pass is performed.

[0023] In the above embodiments, the welding method is further described as CO2 gas shielded welding, and the external current for CO2 gas shielded welding is 150A and the arc voltage is 20V.

[0024] In the above embodiments, further: the bainitic steel frog welded by the welding method has the following composition: C: 0.1 wt.%, Si: 0.7 wt.%, Mn: 1.0 wt.%, Cr: 1.0 wt.%; Ni: 1.0 wt.%; Mo: 1.0 wt.%; Cu: 0.01 wt.%; P: 0.005 wt.%; S: 0.005 wt.%, with the balance being Fe and unavoidable impurities.

[0025] Example 2: A welding wire for repairing bainitic steel frogs, wherein the welding wire composition is C: 0.15 wt.%, Mn: 3.2 wt.%, Si: 2.2 wt.%, P: 0.01 wt.%, S: 0.01 wt.%, Cr: 1.2 wt.%, Nb: 0.35 wt.%, Ni: 0.15 wt.%, B: 0.35 wt.%, with the balance being Fe.

[0026] In the above embodiments, the welding wire is further described as a flux-cored welding wire with a diameter of φ1.2mm.

[0027] This invention also claims protection for a welding method for bainitic steel frogs, wherein the welding method uses the aforementioned welding wire and the welding method is as follows: after each welding pass, 12% NaCl brine is poured onto the weld, and after the previous weld has cooled rapidly to room temperature, the next welding pass is performed.

[0028] In the above embodiments, the welding method is further described as CO2 gas shielded welding, and the external current for CO2 gas shielded welding is 160A and the arc voltage is 24V.

[0029] In the above embodiments, further: the bainitic steel frog welded by the welding method has the following composition: C: 0.2 wt.%, Si: 0.9 wt.%, Mn: 1.5 wt.%, Cr: 1.2 wt.%; Ni: 1.2 wt.%; Mo: 1.2 wt.%; Cu: 0.1 wt.%; P: 0.01 wt.%, S: 0.01 wt.%, with the balance being Fe and unavoidable impurities.

[0030] Example 3: A welding wire for repairing bainitic steel frogs, wherein the welding wire composition is C: 0.2 wt.%, Mn: 3.5 wt.%, Si: 2.5 wt.%, P: 0.02 wt.%, S: 0.02 wt.%, Cr: 1.5 wt.%, Nb: 0.4 wt.%, Ni: 0.2 wt.%, B: 0.4 wt.%, with the balance being Fe.

[0031] In the above embodiments, the welding wire is further described as a flux-cored welding wire with a diameter of φ1.6mm.

[0032] This invention also claims protection for a welding method for bainitic steel frogs, wherein the welding method uses the aforementioned welding wire and the welding method is as follows: after each welding pass, 16% NaCl brine is poured onto the weld, and after the previous weld has cooled rapidly to room temperature, the next welding pass is performed.

[0033] In the above embodiments, the welding method is further described as CO2 gas shielded welding, and the external current for CO2 gas shielded welding is 170A and the arc voltage is 28V.

[0034] In the above embodiments, further: the bainitic steel frog welded by the welding method has the following composition: C: 0.3 wt.%, Si: 1.2 wt.%, Mn: 2.0 wt.%, Cr: 1.4 wt.%; Ni: 1.4 wt.%; Mo: 1.4 wt.%; Cu: 0.2 wt.%; P: 0.02 wt.%; S: 0.02 wt.%, with the balance being Fe and unavoidable impurities.

[0035] Example 4: A welding wire for repairing bainitic steel frogs, wherein the welding wire composition is C: 0.3 wt.%, Mn: 4 wt.%, Si: 3.0 wt.%, P: 0.03 wt.%, S: 0.03 wt.%, Cr: 2.0 wt.%, Nb: 0.5 wt.%, Ni: 0.3 wt.%, B: 0.5 wt.%, with the balance being Fe.

[0036] In the above embodiments, the welding wire is further described as a flux-cored welding wire with a diameter of φ1.8mm.

[0037] The present invention also claims protection for a welding method for bainitic steel frogs, wherein the welding method uses the aforementioned welding wire and the welding method is as follows: after each welding pass, 20% NaCl brine is poured onto the weld, and after the previous weld has cooled rapidly to room temperature, the next welding pass is performed.

[0038] In the above embodiments, the welding method is further described as CO2 gas shielded welding, and the external current for CO2 gas shielded welding is 180A and the arc voltage is 30V.

[0039] In the above embodiments, further: the bainitic steel frog welded by the welding method has the following composition: C: 0.4 wt.%, Si: 1.5 wt.%, Mn: 2.5 wt.%, Cr: 1.5 wt.%; Ni: 1.5 wt.%; Mo: 1.5 wt.%; Cu: 0.3 wt.%; P: 0.03 wt.%; S: 0.03 wt.%, with the balance being Fe and unavoidable impurities.

[0040] It should be noted that the welding wire for repairing bainitic steel frogs of this invention has significant metallic advantages in terms of high strength and toughness matching, improved wear resistance, enhanced fatigue resistance, optimized welding process adaptability, and guaranteed low-temperature performance. Bainitic steel itself possesses high strength and good toughness. The welding wire of this invention, with appropriate amounts of elements such as C, Mn, and Si, can form a bainitic structure during the welding process, thereby ensuring that the weld metal has a high strength and good toughness matching. High strength helps to withstand the huge loads borne by the frog during operation, while good toughness resists the initiation and propagation of cracks, increasing the service life of the frog. Elements such as Cr and Ni in the welding wire of this invention can improve the wear resistance of the weld metal, reduce wear on the frog during use, thereby extending the frog replacement cycle and reducing maintenance costs. By adding appropriate amounts of elements such as Nb and B, the welding wire of this invention can refine the grain size of the weld metal, improve the fatigue resistance of the weld metal, reduce the initiation and propagation of fatigue cracks, and thus increase the fatigue life of the frog. The welding wire of this invention is designed with welding process adaptability in mind. Low P and S content helps reduce defects such as porosity and cracks during welding, improving weld quality. Simultaneously, an appropriate amount of Si enhances the deoxidation capacity of the weld metal, further reducing welding defects. For railway frogs used in cold regions, low-temperature performance is particularly important. This invention's welding wire, with an appropriate amount of Ni, improves the low-temperature toughness of the weld metal, ensuring the frogs maintain good performance even in low-temperature environments.

[0041] This invention features a wire diameter design that improves welding efficiency and cladding rate. Compared to solid welding wire, flux-cored welding wire can increase deposition rate by 20%–30%, significantly shortening welding time. The diameter range of φ0.8–1.8 mm covers welding needs from thin plates to medium-thick plates, making it particularly suitable for repair welding of complex structures like turnouts with significant thickness variations. The slag-forming agent in the flux core forms a dense slag, effectively isolating air and reducing defects such as porosity, cracks, and slag inclusions during welding. This is crucial for components like turnouts, which have extremely high weld quality requirements, significantly reducing rework rates. Through precise proportioning of the internal alloy powder, the flux-cored welding wire ensures a high degree of matching between the weld metal composition and the base metal, avoiding performance fluctuations caused by base metal dilution in solid welding wire. For example, turnout repair welding requires ensuring the consistency of the bainitic structure between the weld and the base metal; the flux core design allows for precise control of the transition of key elements such as Cr, Nb, and B. Flux-cored welding wire offers excellent slag coverage and a stable arc, making it suitable for all-position welding, including flat, vertical, horizontal, and overhead welding. It is particularly well-suited for repair welding of structures like frogs with limited space and complex weld shapes. Compared to solid wire, the slag layer of flux-cored wire reduces wind interference with the arc, making it suitable for outdoor welding environments or those with poor ventilation, such as railway on-site maintenance, thus improving welding process stability. Optimized flux-cored wire composition significantly reduces welding spatter, minimizing post-weld cleaning and increasing operational efficiency. Its high deposition efficiency and low weld defect rate reduce material waste and rework costs. φ0.8–1.8mm flux-cored wire is compatible with most automated welding equipment (such as robotic welding systems), supporting high-speed, high-efficiency welding and further reducing labor costs. The addition of elements like Ni and B to the flux core refines the grain size and improves the low-temperature toughness of the weld metal. Combined with a bainitic steel composition design, this wire maintains good toughness even at -40℃ or lower, meeting the requirements for frogs in cold regions. Elements such as Cr and Si in the flux core can form a dense oxide film, which improves the corrosion resistance of the weld metal and extends the service life of the turnout in humid or corrosive environments.

[0042] This invention's welding method, through an innovative design of forced cooling with 10-20% NaCl brine combined with room temperature waiting between passes, achieves three core advantages in the repair welding of bainitic steel frogs: refined microstructure, optimized performance, and controllable process. Brine cooling accelerates the cooling rate of the weld metal, promoting bainitic microstructure formation and refining grains; fine grain strengthening simultaneously improves strength and toughness, avoiding the brittleness tendency caused by coarse microstructure, thus matching the dual requirements of frogs for high strength and fatigue resistance. Rapid cooling inhibits the formation of low-strength phases such as ferrite and pearlite, reducing soft zones in the weld and ensuring microstructure consistency between the weld and the base metal. Studies show that bainitic steel frogs are prone to softening bands if the cooling rate is insufficient after air cooling, a problem effectively avoided by brine cooling. Room temperature waiting between passes reduces the local temperature gradient of the weld, decreasing residual tensile stress caused by rapid cooling and lowering the risk of crack initiation. Combined with the low crack sensitivity of bainitic steel, this further ensures welding reliability. A 10-20% NaCl brine concentration strikes a balance between cooling efficiency and cost, avoiding weld cracking caused by excessively rapid cooling with pure water while preventing insufficient cooling with low-concentration brine. Experiments show that this concentration can increase the weld cooling rate by 3-5 times compared to air cooling, significantly shortening the welding cycle. Forced cooling to room temperature before the next welding pass ensures that each weld layer undergoes a complete bainitic phase transformation, avoiding interlayer microstructure differences. This is particularly important for thick-section, multi-pass welded structures like frogs, reducing microstructure coarsening caused by heat accumulation. Brine cooling materials are readily available and easy to use, making it especially suitable for railway on-site maintenance environments. Compared to traditional post-weld heat treatment requiring specialized cooling equipment, this method achieves weld performance improvement and reduces maintenance costs without additional energy input. Fine-grained bainitic microstructure exhibits higher hardness and wear resistance. The uniform and fine bainitic microstructure reduces stress concentration, and combined with a low residual stress state, improves the weld's resistance to fatigue crack propagation. Studies show that the fatigue life of bainitic steel frogs is 2-3 times that of high-manganese steel, making it particularly suitable for heavy-haul railways. This method enables "online welding repair" of frogs, meaning that once wear reaches its limit, there is no need for complete replacement; only localized welding repairs are required to restore usability. Compared to imported bainitic steel welding materials or complex welding processes, this method uses a low-cost combination of domestically produced flux-cored welding wire and brine cooling, reducing the maintenance cost of a single frog by 30% to 40%, while also minimizing downtime and improving railway transport efficiency.

[0043] This invention limits the welding method to gas metal arc welding (GMAW) using CO2, and specifies the parameter range of 150–180A external current and 20–30V arc voltage. Under these parameters, CO2 GMAW can achieve a stable short-circuit transfer mode. During short-circuit transfer, the droplet diameter is small (approximately 0.5–1.2 mm), the transfer frequency is high (50–200 times / s), the arc combustion is stable, and spatter is significantly reduced (more than 60% less compared to coarse droplet transfer). This is particularly important for components like frogs with complex structures and narrow weld spaces, preventing spatter from getting stuck in the wheel-rail contact surface and ensuring operational safety. Within this parameter range, the arc stiffness is moderate, which can penetrate the oxide film on the frog surface, such as rust and oil, ensuring good fusion, without causing excessive melting or burn-through of the base material due to excessive current, thus improving welding efficiency. The deposition efficiency of CO2 GMAW can reach 8–12 kg / h, and combined with a 150–180A current, it can quickly fill frog wear defects, significantly shortening maintenance time. By adjusting the voltage by 20-30V, the arc length can be precisely controlled, thereby adjusting the heat input. This flexibility prevents the frog from coarsening of the microstructure or concentration of residual stress due to localized overheating, extending its service life. Under optimized parameters, the weld surface is smooth, with uniform reinforcement height controlled at 1-2mm, free from defects such as undercut and lack of fusion, reducing stress concentration at wheel-rail contact and lowering the risk of fatigue crack initiation. CO2 gas shielded welding provides good molten pool protection, and combined with the deoxidizing and slag-forming effect of flux-cored wire, it effectively reduces hydrogen porosity. Simultaneously, the 150-180A current range avoids excessive current leading to grain coarsening and increased crack susceptibility. The rapid cooling characteristics of CO2 gas shielded welding complement the aforementioned brine cooling process, further refining the weld microstructure and resulting in superior wear resistance compared to high-manganese steel frogs. Within this parameter range, the peak temperature (Tp) and cooling time (t8 / 5) of the welding thermal cycle are controllable. Combined with inter-pass brine cooling, it significantly reduces residual tensile stress in the weld, minimizing the risk of stress corrosion cracking during service. CO2 gas shielded welding equipment is inexpensive and easy to maintain, making it suitable for the decentralized operation needs of railway on-site maintenance. Within this parameter range, the welding machine power factor (PF) can reach over 0.9, resulting in high energy efficiency. Energy consumption for single-piece turnout maintenance is reduced by 40%–50% compared to traditional manual arc welding. This parameter range fully utilizes the metallurgical effects of alloying elements in the flux-cored wire, such as Cr, Ni, and B, ensuring a high degree of matching between the weld metal composition and the base metal, and avoiding performance degradation due to component dilution.

[0044] This invention relates to a bainitic steel frog composition design that enhances strength, toughness, and wear resistance, optimizes welding process adaptability, and strengthens fatigue resistance. The Mo content (1.0–1.5 wt.%) significantly improves the hardenability of the steel, shifting the bainitic transformation curve to the right and ensuring that the frog forms a uniform bainitic structure even under air cooling conditions. Simultaneously, Mo forms stable carbides with C, slowing carbon diffusion, inhibiting ferrite precipitation, and refining grains, thus maintaining toughness while improving strength. The combined addition of Cr (1.0–1.5 wt.%) and Mo further delays the pearlite and ferrite transformation, expanding the bainitic transformation zone. Cr also forms stable carbides, improving the tempering stability of the steel and ensuring the stability of the frog's microstructure during service, preventing softening failure. Bainitic steel exhibits superior wear resistance compared to high-manganese steel because its fine bainitic lath bundles and retained austenite effectively resist abrasive penetration and micro-cutting. Although the Cu content (0.01–0.3 wt.%) is low, it can dissolve in ferrite, improving the matrix strength through solid solution strengthening and refining the grains, thus indirectly enhancing wear resistance. Furthermore, Cu improves the corrosion resistance of steel, reducing corrosion wear on the frog in humid environments. A low C content (0.1–0.4 wt.%) reduces weld crack susceptibility while ensuring sufficient strength. Mn (1.0–2.5 wt.%) expands the austenite phase region, stabilizes retained austenite, and improves weld toughness. Extremely low P (<0.03 wt.%) and S (<0.03 wt.%) content significantly reduces phosphide and sulfide inclusions in the weld, preventing hot cracking. Low P and S content also improves the low-temperature toughness of the steel, reducing the risk of brittle fracture of the frog in cold regions. Ni (1.0–1.5 wt.%) lowers the ductile-brittle transition temperature of the steel, improving low-temperature toughness. Under alternating impact loads, Ni can inhibit crack initiation and propagation, extending the fatigue life of turnouts. Si (0.7–1.5 wt.%) can dissolve in ferrite, improving matrix strength through solid solution strengthening. Si is a strong deoxidizer, reducing the oxygen content in steel and decreasing the number of non-metallic inclusions, thereby reducing fatigue crack initiation points.

[0045] The design principle of this invention is as follows: (combined with) Figure 1 , Figure 2 , Figure 3 This invention addresses the development direction and future market demand for frogs. Using U20MnCrNiMo, a novel bainitic steel frog material, as the primary research base, and considering the composition and microstructure characteristics of bainitic steel frog materials, this invention explores welding process parameters and selects suitable welding wires. Ultimately, it determines an arc welding repair wire suitable for bainitic steel frog repair welding. Combined with the welding method, it exhibits excellent welding performance and material composition / microstructure, with no defects in the welded area and weld joint strength meeting usage requirements.

[0046] As can be seen from the above description, the present invention can obtain the best weld structure, and the weld repair area of ​​the turnout is free from welding defects such as cracks, inclusions and porosity; the welding method of the present invention broadens its application in more fields; the welding process of the present invention is easy to operate, easy to implement, suitable for promotion, and can be carried out by relevant personnel with a little training. No preheating is required before welding, and no cracks will be generated. The weld structure has good performance and is of great significance to promoting the national "dual carbon" strategic goal.

[0047] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications and equivalent substitutions made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A welding wire for repairing bainitic steel frogs, characterized in that: The welding wire composition is as follows: C: 0.1-0.3 wt.%, Mn: 3.0-4.0 wt.%, Si: 2.0-3.0 wt.%, P: ≤0.03 wt.%, S: ≤0.03 wt.%, Cr: 1.0-2.0 wt.%, Nb: 0.3-0.5 wt.%, Ni: 0.1-0.3 wt.%, B: 0.3-0.5 wt.%, with the balance being Fe.

2. The welding wire according to claim 1, characterized in that: The welding wire is a flux-cored welding wire with a diameter of φ0.8~1.8mm.

3. A welding method for bainitic steel frogs, characterized in that, The welding method uses the welding wire described in any one of claims 1-2. The welding method is as follows: after each welding pass, 10-20% NaCl brine is poured onto the weld. After the previous weld has cooled rapidly to room temperature, the next welding pass is performed.

4. The welding method according to claim 3, characterized in that: The welding method is CO2 gas shielded welding, and the external current for CO2 gas shielded welding is 150-180A, and the arc voltage is 20-30V.

5. The welding method according to claim 3, characterized in that: The bainitic steel frog welded by the aforementioned welding method has the following composition: C: 0.1–0.4 wt.%, Si: 0.7–1.5 wt.%, Mn: 1.0–2.5 wt.%, Cr: 1.0–1.5 wt.%, Ni: 1.0–1.5 wt.%, Mo: 1.0–1.5 wt.%, Cu: 0.01–0.3 wt.%, P: <0.03 wt.%, S: <0.03 wt.%, with the balance being Fe and unavoidable impurities.

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