A wear-resistant flux-cored welding wire for surface repair of flux-cored and single-toothed rollers, and a welding method.

Abstract

This invention relates to the field of welding materials technology, specifically to a wear-resistant flux-cored welding wire for surface repair of single-toothed rollers. The specific technical solution is as follows: a flux core, by mass percentage, comprises the following components: 5-15% graphite, 20-60% high-carbon ferrochrome, 3-10% silicon carbide, 2-15% tungsten carbide, 1-6% electrolytic manganese, 5-20% ferromolybdenum, with the balance being Fe powder. The flux-cored welding wire provided by this invention, through arc welding, yields a welding alloy that not only exhibits good welding processability and aesthetically pleasing weld formation with few surface pores, but also possesses high hardness and wear resistance.

Description

Technical Field

[0001] This invention relates to the field of welding materials technology, specifically to a flux-cored, wear-resistant surfacing flux-cored welding wire for repairing the surface of a single-tooth roller and a welding method thereof. Background Technology

[0002] As an indispensable key equipment in the modern steel industry, the single-tooth roll crusher plays a crucial role in the crushing and processing of materials such as sintered ore and blast furnace slag. During long-term operation, this equipment continuously endures severe wear from high-temperature sintered materials. Its main failure mechanisms can be summarized into the following three aspects: (1) The continuous contact and friction between the high-temperature sintered material and the surface of the roller teeth leads to the gradual loss of tooth surface material, eventually causing damage to the integrity of the roller tooth structure; (2) Under the working environment, the oxide scale on the roller surface peels off periodically, resulting in a significant increase in surface roughness, which in turn forms a vicious cycle that accelerates the wear process; (3) Under long-term alternating loads, the continuous friction and wear between the toothed roller and the material causes stress concentration, eventually leading to the fracture of the toothed roller structure. These failure modes not only affect the service life of the equipment, but also directly relate to the continuity and economy of steel production.

[0003] For the severe wear problem of single-toothed roll crushers under harsh working conditions, surfacing repair technology has become the industry's preferred solution due to its process reliability and cost-effectiveness. In engineering practice, the main surfacing repair materials are nickel-based, cobalt-based, and iron-based surfacing alloys. Cobalt-based surfacing alloys are known for their excellent wear resistance, especially suitable for high-stress wear environments. However, their high material cost limits large-scale application, and the demanding welding process significantly increases process complexity. Nickel-based surfacing alloys perform best in resisting intermetallic friction and wear, while also possessing excellent high-temperature resistance (operating temperatures up to 800℃ and above) and oxidation resistance, making them particularly suitable for high-temperature wear conditions. However, their high procurement cost limits their application mainly to the repair of critical components, resulting in poor economic efficiency. In contrast, iron-based surfacing alloys, with their excellent wear resistance and good cost-effectiveness, have become the most widely used surfacing materials in industrial applications. Among them, Fe-Cr-C alloys are favored due to their unique microstructure design. M7C3 and M... 23 High-hardness carbide hard phases such as C6 and M3C form a three-dimensional wear-resistant skeleton structure, which can not only effectively hinder the cutting action of abrasive grains, but also achieve excellent impact wear resistance, thus significantly reducing repair costs while ensuring wear resistance.

[0004] While traditional Fe-Cr-C surfacing alloys exhibit good wear resistance under normal working conditions, their wear resistance and impact resistance remain insufficient under the high stress and high impact wear conditions experienced by single-toothed roll crushers over long periods, making it difficult to meet actual repair needs. To address this technical bottleneck, this invention optimizes and modifies traditional Fe-Cr-C alloys through a multi-element alloying design. By introducing strong carbide-forming elements such as Mo and W, the wear resistance and impact resistance of the alloy are significantly improved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a wear-resistant flux-cored welding wire and welding method for surface repair of flux-cored and single-toothed rollers. The flux-cored welding wire provided by this invention, through arc welding, produces a welding alloy that not only has good welding processability and beautiful weld formation with few surface pores, but also possesses high hardness and wear resistance.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention discloses a core containing the following components by weight percentage:

[0008] Graphite 5-15%, high-carbon ferrochrome 20-60%, silicon carbide 3-10%, tungsten carbide 2-15%, electrolytic manganese 1-6%, ferromolybdenum 5-20%, balance Fe powder.

[0009] Preferably, the high-carbon ferrochrome has a chromium mass fraction of 68% and a carbon mass fraction of 8%; the silicon carbide has a silicon mass fraction of 70% and a carbon mass fraction of 30%; the tungsten carbide powder has a tungsten mass fraction of 94% and a carbon mass fraction of 6%; the ferromolybdenum has a molybdenum mass fraction of 60%; the electrolytic manganese has a manganese mass fraction greater than 90%; and the graphite has a carbon mass fraction greater than 99.5%.

[0010] Preferably, by mass percentage, the composition is 5-15% graphite, 30-50% high-carbon ferrochrome, 3-6% silicon carbide, 5-10% tungsten carbide, 2-5% electrolytic manganese, 8-15% ferromolybdenum, and the remainder is Fe powder.

[0011] Preferably, the high-carbon ferrochrome has a particle size of 30-50 mesh, the ferromolybdenum and tungsten carbide have a particle size of 80-100 mesh, the electrolytic manganese has a particle size of 60-80 mesh, the silicon carbide has a particle size of 70-90 mesh, the graphite has a particle size of 40-60 mesh, and the Fe powder has a particle size of 100-150 mesh.

[0012] Accordingly, a wear-resistant flux-cored welding wire for surface repair of a single-toothed roller is provided, wherein the raw material of the flux-cored welding wire includes the flux core.

[0013] Preferably, the flux-cored wire has a flux-cored filling rate of 40-60%.

[0014] Correspondingly, a method for preparing a wear-resistant flux-cored welding wire for surface repair of a single-toothed roller involves encasing the flux core in a metal shell.

[0015] Accordingly, a welding method for reducing welding porosity in the surface repair weld overlay of a single-toothed roller is provided, which uses the wear-resistant weld overlay flux-cored wire for surface repair of the single-toothed roller, and the welding process is plasma arc welding.

[0016] Preferably, the plasma arc welding process parameters are: voltage: 25-30 V, current: 300-500 A, wire feed speed: 8-9 m / min, atmosphere: 80% Ar + 20% CO2 mixture, gas flow rate: 15-20 L / min, and wire elongation: 15-20 mm.

[0017] Preferably, after welding, the mass percentage of alloying elements in the obtained weld overlay alloy is within the following range: C: 2-8%; Cr: 10-40%; Mo: 2-7%; Mn: 0.5-3%; Si: 0.5-2%; W: 1-6%; Fe and unavoidable impurities: balance.

[0018] The present invention has the following beneficial effects:

[0019] The wear-resistant flux-cored welding wire for surface repair of a single-toothed roller provided by this invention conforms to the performance characteristics of a new type of wear-resistant and impact-resistant material.

[0020] This invention provides a wear-resistant flux-cored welding wire for repairing the surface of a single-toothed roller. Through arc welding, a composite microstructure with excellent wear resistance can be formed on the substrate surface. Metallographic analysis shows that the weld overlay mainly consists of a martensitic matrix, retained austenite, and carbide reinforcing phases (M7C3 and MC types). This multi-phase synergistic microstructure endows the material with good mechanical properties. Traditional Fe-Cr-C weld overlay alloys exhibit significant performance deficiencies under the high stress and high impact wear conditions of long-term service on single-toothed rollers, mainly manifested in rapid wear resistance degradation and unsatisfactory repair effects. Therefore, this invention innovatively introduces strong carbide-forming elements such as Mo and W for alloying modification based on the Fe-Cr-C alloy system. The addition of Mo promotes the nucleation and precipitation of carbides in the alloy, not only increasing the amount of hard phases but also effectively refining the grain size and improving the uniformity of the microstructure. W significantly improves the wear resistance of the material through solid solution strengthening and the formation of special carbides. This carbide-reinforced iron-based alloy represents the development direction of a new generation of wear-resistant materials. Its microstructure is characterized by a uniform distribution of fine carbide-reinforcing phases within a martensitic matrix. This unique microstructure offers dual advantages: firstly, the dispersed hard carbide phase effectively hinders the cutting action of abrasive particles, providing excellent wear resistance; secondly, the synergistic effect of the martensitic matrix and carbides allows the material to maintain high hardness while also possessing good impact resistance, meeting the repair requirements of single-toothed roll crushers. Furthermore, the presence of retained austenite helps alleviate stress concentration. Single-toothed rolls repaired using this welding wire exhibit a significantly longer service life compared to traditional Fe-Cr-C alloy welding coatings, meeting the steel industry's requirements for long service life and high reliability of critical equipment. Attached Figure Description

[0021] Figure 1 Flowchart for the preparation of wear-resistant flux-cored welding wire for surface repair of single-toothed rollers;

[0022] Figure 2 The surface morphology of the weld overlay alloy prepared in Example 5;

[0023] Figure 3 This is a wear depth diagram of the weld overlay alloy prepared in Example 5. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Unless otherwise specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.

[0026] This invention discloses a core containing the following components by weight percentage:

[0027] The composition comprises 5-15% graphite, 20-60% high-carbon ferrochrome, 3-10% silicon carbide, 2-15% tungsten carbide, 1-6% electrolytic manganese, 5-20% ferromolybdenum, and the balance being Fe powder. As a preferred embodiment, the composition is 5-15% graphite, 30-50% high-carbon ferrochrome, 3-6% silicon carbide, 5-10% tungsten carbide, 2-5% electrolytic manganese, 8-15% ferromolybdenum, and the remainder being Fe powder. Specifically, the high-carbon ferrochrome has a particle size of 30-50 mesh, the ferromolybdenum and tungsten carbide both have a particle size of 80-100 mesh, the electrolytic manganese has a particle size of 60-80 mesh, the silicon carbide has a particle size of 70-90 mesh, the graphite has a particle size of 40-60 mesh, and the Fe powder has a particle size of 100-150 mesh.

[0028] Furthermore, the high-carbon ferrochrome contains 68% chromium and 8% carbon by mass; the silicon carbide contains 70% silicon and 30% carbon by mass; the tungsten carbide powder contains 94% tungsten and 6% carbon by mass; the ferromolybdenum contains 60% molybdenum by mass; the electrolytic manganese contains more than 90% manganese by mass; and the graphite contains more than 99.5% carbon by mass.

[0029] This invention discloses a wear-resistant flux-cored welding wire for surface repair of single-tooth rollers, wherein the raw material of the flux-cored welding wire includes the aforementioned flux core. The flux core filling rate in the welding wire is 40-60%, representing the percentage of the area occupied by the flux core to the total cross-sectional area of ​​the welding wire. As a preferred embodiment, the flux core filling rate is 40-55%, and in a more preferred embodiment, it is 45-50%.

[0030] The preparation process of a wear-resistant flux-cored welding wire for surface repair of a single-tooth roller includes the following steps:

[0031] (1) Powder selection and drying: Select alloy powders according to the above core composition, and dry each powder in advance. The drying equipment is a vacuum drying oven, the drying temperature is 150℃, and the drying time is 2 hours.

[0032] (2) Sieving: In order to ensure the consistency of the particle size of the same powder, each powder needs to be sieved through a sieve.

[0033] (3) Powder preparation and mixing: Powder preparation is carried out according to the filling rate of each flux-cored wire and the mass percentage of each powder. After the powder preparation is completed, the different powders need to be mixed evenly to ensure that the components in the flux-cored wire are uniform.

[0034] (4) Selection of strip: Select stainless steel strip as metal shell, with a thickness of 0.3 mm and a width of 12 mm.

[0035] (5) Drawing: The steel strip passes through the forming rollers, changing from a flat surface to a U-shape. At this time, the pre-prepared core powder is fed into the U-shaped steel strip via a conveyor belt. After the U-shaped steel strip carrying the powder continuously passes through the closing rollers, the steel strip changes from a U-shape to an O-shape, closing and tightly wrapping the core powder. Figure 1 As shown.

[0036] (6) Diameter reduction and packaging: The drawn flux-cored wire is passed through a drawing die of a certain diameter to finally achieve the diameter required for the finished product. The reduced-diameter flux-cored wire is loaded into an I-beam and sealed for storage until it is ready for use.

[0037] The present invention also provides a welding method for reducing welding porosity in the weld overlay layer of a single-tooth roller surface repair, wherein the wear-resistant weld overlay flux-cored wire for single-tooth roller surface repair is used for welding, and the welding process is plasma arc welding.

[0038] The plasma arc welding process parameters are as follows: voltage: 25-30 V, current: 300-500 A, wire feed speed: 8-9 m / min, atmosphere: 80% Ar + 20% CO2 mixture, gas flow rate: 15-20 L / min, wire elongation: 15-20 mm. After welding, the mass percentage of alloying elements in the obtained weld alloy is within the following range: C: 2-8%; Cr: 10-40%; Mo: 2-7%; Mn: 0.5-3%; Si: 0.5-2%; W: 1-6%; Fe and unavoidable impurities: balance.

[0039] In this invention, the various elements function as follows:

[0040] C: Carbon and chromium are alloying elements that significantly affect the microstructure of high-chromium cast iron. As the mass fraction of carbon and chromium increases, the microstructure of high-chromium cast iron transforms from a hypoeutectic to a hypereutectic structure, and the primary phase changes from austenite to M7C3 carbides. The M7C3 carbide hard phase has high hardness and can significantly improve the wear resistance of the weld overlay.

[0041] Cr: Chromium plays a decisive role in the type of carbide, mainly forming M3C, M7C3, and M... 23 C6 carbides. Among them, M7C3 carbides have extremely high hardness and are uniformly distributed in the matrix as hard particles, significantly improving the hardness and wear resistance of the material. At the same time, Cr can improve the strength of steel and improve the hardenability of alloys.

[0042] Mo: Mo can improve the hardenability of alloy steel, inhibit the transformation of pearlite and ferrite, and enable more austenite to transform into martensite during quenching; at the same time, it can improve the strength and tempering resistance of martensite through solid solution strengthening and carbide formation.

[0043] W: W significantly improves the tempering stability, red hardness (e.g., high-speed steel maintains high hardness at 600℃) and high-temperature strength of steel by forming stable carbides (such as W2C) and solid solution strengthening; its carbides can also improve wear resistance, making it especially suitable for high-temperature and high-wear environments such as cutting tools.

[0044] Mn and Si: The elemental transition coefficient is improved by using manganese-silicon combined deoxidation.

[0045] Fe: Filling the gap.

[0046] To better understand the present invention, the present invention will be further described below with reference to specific embodiments.

[0047] In the following embodiments, all raw materials used are commercially available.

[0048] 1. In the following embodiments, the outer sheath of the flux-cored welding wire is made of stainless steel strip with a thickness of 0.3 mm and a width of 12 mm. The flux composition of the flux-cored welding wire is specifically described in the embodiments. After passing through the rollers, the steel strip is rolled into a U-shape. Various powders in the formula are weighed in advance according to the designed proportions, dried, mixed evenly, and then mechanically added to the steel strip. The U-shaped steel strip closes after passing through subsequent rollers. The closed steel strip is repeatedly drawn and reduced in diameter using a drawing die to produce a flux-cored welding wire with a diameter of 2.8 mm, thus obtaining a wear-resistant surfacing flux-cored welding wire for single-tooth roller surface repair.

[0049] 2. In the core powder, the high-carbon ferrochrome has a particle size of 30-50 mesh; the ferromolybdenum and tungsten carbide both have a particle size of 80-100 mesh; the manganese has a particle size of 60-80 mesh; the silicon carbide has a particle size of 70-90 mesh; the graphite has a particle size of 40-60 mesh; and the Fe powder has a particle size of 100-150 mesh.

[0050] The high-carbon ferrochrome has a chromium mass fraction of 68% and a carbon mass fraction of 8%; the silicon carbide has a silicon mass fraction of 70% and a carbon mass fraction of 30%; the tungsten carbide powder has a tungsten mass fraction of 94% and a carbon mass fraction of 6%; the ferromolybdenum has a molybdenum mass fraction of 60%; the manganese raw material has a manganese mass fraction greater than 90%; and the graphite has a carbon mass fraction greater than 99.5%.

[0051] 3. The weld overlay alloy was prepared using an electric arc welding process. The welding process parameters were: voltage: 25-30V, current: 300-500A, wire feed speed: 8-9m / min, atmosphere: 80%Ar + 20%CO2 mixture, gas flow rate: 15-20L / min, and wire elongation: 15-20mm. The weld overlay alloy prepared in the example was subjected to hardness tests, abrasive wear tests, friction wear tests, and impact tests. The specific test steps are as follows:

[0052] (1) The Rockwell hardness of the weld overlay alloy was tested using an HR-150A electric Brinell hardness tester. The hardness tester indenter was a diamond cone indenter, the load was 150 kg, the loading time was 5 s, and the recovery time was 3 s. The distance between two adjacent test points was 5 mm, and the number of test points was 10. The final hardness of the weld overlay alloy was taken as the average value of the data from the 10 test points.

[0053] (2) Abrasive wear tests were conducted using an MLS-225 wet sand rubber wheel abrasive wear testing machine. The wear sample size was 57mm × 25mm × 10mm. The main test parameters included: rubber wheel diameter of 176mm, rubber wheel speed of 240 rpm, rubber wheel hardness of 60 Shore hardness, 40-70 mesh quartz sand as abrasive, load of 100 N, and 1000g of water and 1500g of quartz sand added during the test. Before each test, the sample was pre-ground at 2000rpm to avoid the surface roughness of the sample affecting the wear results. The sample was weighed after pre-grounding as the weight before wear. After 8000rpm, the sample was immersed in an ethanol solution, ultrasonically cleaned, and dried with a hair dryer. The sample was weighed using a Beijing Sartorius precision balance, with the weight accurate to 0.0001g. Each sample was tested three times, and the average weight loss of the sample was taken as the reference standard for wear resistance.

[0054] (3) Friction and wear tests were conducted using an MS-HT1000 friction and wear testing machine. The wear specimen size was 20mm×20mm×7mm. The test parameters were: φ4 silicon carbide, load 2000g, friction radius 6mm, rotation speed 300r / min, test temperature room temperature, and test time 60min. To reduce experimental error, each specimen was tested three times. After the test, the three-dimensional morphology of the wear track was obtained using an OLMPUS-4100 laser confocal scanning microscope, and the wear volume of the specimen was calculated. The wear track morphology was observed using a field emission scanning electron microscope.

[0055] (4) The impact resistance of the weld overlay alloy was tested using a self-designed drop hammer impact testing machine. The impact specimen size was 57mm×25mm×15mm. The specimen was placed in the groove under the punch and then clamped with a clamp before impact. The punch tip had a certain angle. The impact energy could be selected by adjusting the height of the punch with a screw. The hammer of the impact testing machine was 10kg, the maximum impact load was 80J, and the impact tip angle of the hammer was 171°. To simulate the impact force under the actual working conditions of a single toothed roller, the impact energy set in this test was 10J. The toughness of the weld overlay alloy was comprehensively measured by the actual impact tip angle θ. The impact angle was measured using the image processing software Image-pro.

[0056] Example 1

[0057] Weigh the core according to the following percentages: 8% graphite, 30% high-carbon ferrochrome, 3.5% silicon carbide, 5% tungsten carbide, 2.5% electrolytic manganese, 8% ferromolybdenum, and the remainder is Fe powder.

[0058] The welding alloy prepared according to the welding process disclosed above in this invention has the following mass percentage content of alloying elements: C: 5.5%; Cr: 18.5%; Mo: 2.1%; Mn: 1.1%; W: 1%; Si: 0.8%; Fe and unavoidable impurities: balance.

[0059] The Rockwell hardness of the weld overlay alloy is 60.1 HRC; the wear loss weight in the abrasive wear test is 0.6162 g; the wear depth in the friction and wear test is 12.6 μm; and the impact angle is 55.3°.

[0060] Example 2

[0061] Weigh the core according to the following percentages: 8% graphite, 35% high-carbon ferrochrome, 3.5% silicon carbide, 4.5% tungsten carbide, 2.5% electrolytic manganese, 10% ferromolybdenum, and the remainder is Fe powder.

[0062] The welding alloy prepared according to the welding process disclosed above in this invention has the following mass percentage content of alloying elements: C: 5.5%; Cr: 20.0%; Mo: 2.8%; Mn: 1.1%; W: 2%; Si: 0.8%; Fe and unavoidable impurities: balance.

[0063] The Rockwell hardness of the weld overlay alloy is 63.7 HRC; the wear loss weight in the abrasive wear test is 0.4927 g; the wear depth in the friction and wear test is 9.7 μm; and the impact angle is 50.5°.

[0064] Example 3

[0065] Weigh the core according to the following percentages: 8% graphite, 35% high-carbon ferrochrome, 3.5% silicon carbide, 7.0% tungsten carbide, 2.5% electrolytic manganese, 12% ferromolybdenum, and the remainder is Fe powder.

[0066] The welding alloy prepared according to the welding process disclosed above in this invention has the following mass percentage content of alloying elements: C: 5.5%; Cr: 20.0%; Mo: 3.0%; Mn: 1.1%; W: 3.0%; Si: 0.8%; Fe and unavoidable impurities: balance.

[0067] The Rockwell hardness of the weld overlay alloy is 65.5 HRC; the wear loss weight in the abrasive wear test is 0.4177 g; the wear depth in the friction and wear test is 8.8 μm; and the impact angle is 42.9°.

[0068] Example 4

[0069] Weigh the core according to the following percentages: 6% graphite, 45% high-carbon ferrochrome, 4.5% silicon carbide, 9% tungsten carbide, 2.5% electrolytic manganese, 12% ferromolybdenum, and the remainder is Fe powder.

[0070] The welding alloy prepared according to the welding process disclosed above in this invention has the following mass percentage content of alloying elements: C: 5.0%; Cr: 23.0%; Mo: 3.2%; Mn: 1.1%; W: 3.5%; Si: 1.5%; Fe and unavoidable impurities: balance.

[0071] The welding process exhibits minimal spatter, good flatness, and minimal micro-cracks; the Rockwell hardness of the weld alloy is 68.1 HRC; in the abrasive wear test, the wear loss weight is 0.3404 g; the friction depth is 7.2 μm; and the impact angle is 37.1°.

[0072] Example 5

[0073] Weigh the core according to the following percentages: 8% graphite, 45% high-carbon ferrochrome, 4.5% silicon carbide, 9% tungsten carbide, 2.5% electrolytic manganese, 15% ferromolybdenum, and the remainder is Fe powder.

[0074] The welding alloy prepared according to the welding process disclosed above in this invention has the following mass percentage content of alloying elements: C: 5.5%; Cr: 23.0%; Mo: 3.5%; Mn: 1.1%; W: 4%; Si: 1.5%; Fe and unavoidable impurities: balance.

[0075] The welding process produces less spatter, the weld alloy surface is bright and smooth, free of cracks, and has few surface pores. Figure 2As shown; the Rockwell hardness of the weld overlay alloy is 69.3 HRC; in the abrasive wear test, the wear loss weight is 0.2520 g; in the tribological wear test, the wear depth is 6.8 μm (as shown). Figure 3 The impact angle is 32.5°.

[0076] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A core, characterized in that: It includes the following components by mass percentage: The composition comprises 5-15% graphite, 30-50% high-carbon ferrochrome, 3-6% silicon carbide, 5-10% tungsten carbide, 2-5% electrolytic manganese, 8-15% ferromolybdenum, and the remainder being Fe powder; the high-carbon ferrochrome contains 68% chromium and 8% carbon by mass; the silicon carbide contains 70% silicon and 30% carbon by mass; the tungsten carbide powder contains 94% tungsten and 6% carbon by mass; the ferromolybdenum contains 60% molybdenum by mass; the electrolytic manganese contains more than 90% manganese by mass; and the graphite contains more than 99.5% carbon by mass.

2. The drug core according to claim 1, characterized in that: The high-carbon ferrochrome has a particle size of 30-50 mesh, the ferromolybdenum and tungsten carbide have a particle size of 80-100 mesh, the electrolytic manganese has a particle size of 60-80 mesh, the silicon carbide has a particle size of 70-90 mesh, the graphite has a particle size of 40-60 mesh, and the Fe powder has a particle size of 100-150 mesh.

3. A wear-resistant flux-cored welding wire for surface repair of a single-toothed roller, characterized in that: The raw material of the flux-cored welding wire includes the flux core as described in any one of claims 1-2, and the flux core filling rate in the flux-cored welding wire is 40-60%.

4. A welding method for reducing welding porosity in the repair weld overlay layer on the surface of a single-toothed roller, characterized in that: The wear-resistant surfacing flux-cored welding wire for surface repair of a single toothed roller as described in claim 3 is used for welding. The welding process is plasma arc surfacing. The plasma arc surfacing process parameters are: voltage: 25-30 V, current: 300-500 A, wire feed speed: 8-9 m / min, atmosphere: 80% Ar + 20% CO2 mixture, gas flow rate: 15-20 L / min, and wire elongation: 15-20 mm. After welding, the mass percentage of alloying elements in the obtained weld overlay alloy is within the following range: C: 2-8%; Cr: 10-40%; Mo: 2-7%; Mn: 0.5-3%; Si: 0.5-2%; W: 1-6%; Fe and unavoidable impurities: balance.

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