Method for prolonging service life of roller through cooperation of tubular composite welding wire surfacing and ultrasonic peening

Abstract

The invention discloses a method for prolonging the service life of a roller through cooperation of tubular composite welding wire surfacing and ultrasonic impact strengthening. A composite welding wire is prepared by spirally stranding a seamless tubular welding wire. A wear-resistant surfacing layer prepared by surfacing the welding wire comprises the following components in percentage by weight: 0.35 to 0.45 percent of C, 1.40 to 1.80 percent of Mn, 0.60 to 0.90 percent of Si, 7.00 to 8.00 percent of Cr, 1.60 to 1.95 percent of Mo, 0.80 to 0.95 percent of V, 3.00 to 4.00 percent of W, 0.50 to 1.20 percent of Nb, 0.002 to 0.004 percent of B, 0.05 to 0.1 percent of Ge and the balance of Fe. All the components in the surfacing layer are fully and uniformly mixed; and the surfacing layer surface is endowed with nano mechanical characteristics by adopting high-energy ultrasonic impact. And the use performance of the roller is improved through component uniformity of the surfacing layer and strengthening cooperation of nano fine grains.

Description

Technical Field

[0001] The present invention relates to the technical field of surfacing modification and repair of metal materials, and particularly to a method for synergistically extending the service life of rolls by surfacing with a tubular composite wire and ultrasonic impact strengthening. Background Art

[0002] With the development of steel rolling equipment in the metallurgical industry towards large-scale, continuous, high-speed and automated directions, the service conditions of rolls, such as high temperature, high variable load, thermal cycling, corrosion, wear and fatigue, tend to be more complex and severe. During operation, rolls are extremely prone to cracking, corrosion and wear, and need to be regularly replaced and maintained. Roll repair is to restore the roll with wear or surface defects removed to its original size by additive manufacturing and precision machining methods. Surfacing is the most commonly used additive manufacturing method, and in addition, methods such as high-speed arc thermal spraying and laser cladding are also used. With the continuous increase in steel production capacity, a large number of rolls are scrapped every year due to immature repair technology, resulting in great waste. At the same time, the frequent replacement of roll components in the steel rolling production line requires shutdown, heavy lifting and transportation, which is time-consuming and laborious, greatly affecting production continuity and work efficiency.

[0003] Roll repair needs to solve several technical problems at the same time: one is that the repair layer meets the special wear resistance, corrosion resistance and thermal fatigue resistance of the steel rolling service conditions, and at the same time has sufficient toughness; the second is that there is sufficient bonding force between the repair layer and the base metal to ensure that it does not fall off during use; the third is that the repair process needs to ensure that the deformation of the roll is within the required range, and after precision machining, it can meet the straightness and out-of-roundness requirements of the original design. From the existing technologies, surfacing technology is an effective way to ensure the metallurgical bonding between the hard-facing repair layer and the base atoms. However, there are still some technical difficulties in roll surfacing repair. The main problem is that the composition of the surfacing layer is relatively complex, and special alloying elements such as high-melting-point refractory metals W and Nb need to be infiltrated, which puts very strict requirements on the smelting and manufacturing of solid welding materials. Another problem is that surfacing is carried out using relatively traditional flux-cored wires. Practice shows that it is difficult to ensure the uniformity of the weld metal composition. The non-uniform composition distribution leads to a non-homogeneous surfacing surface, which in turn causes premature damage at the low-hardness surface of the micro-region during roll use. Once there is micro-region damage on the roll surface, it is judged as scrapped. In addition, the high-temperature creep performance of the surfacing layer is difficult to guarantee. These largely restrict the service life of rolls.

[0004] Therefore, how to improve the uniformity of the surfacing metal composition and at the same time take technical measures on the surfacing surface to further strengthen the surface hardness and toughness has become an urgent technical problem to be solved. Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide a tubular composite welding wire, and solve the problem of how to prepare a homogeneous surfacing layer with both surface hardness and toughness. Another object of the present invention is to propose a preparation method of the tubular composite welding wire, and solve the problem of how to prepare the tubular composite welding wire. The third object of the present invention is to propose the application of the tubular composite welding wire in roll surfacing repair, and solve the problem of how to surfacing and repair rolls.

[0006] Technical Solution: A tubular composite welding wire according to the present invention is obtained by helically stranding several seamless tubular welding wires to form a tubular composite welding wire. The seamless tubular welding wire includes a tubular wrapper and metal powders filled in the tubular wrapper. The metal powders include metal chromium powder, metal tungsten powder, metal molybdenum powder, metal germanium powder, ferrovanadium powder, ferroniobium powder, graphite powder, ferromanganese powder, ferrosilicon powder, and titanium-boron additive; the titanium-boron additive is prepared by mixing titanium iron powder and boron oxide powder in a mass ratio of 10:1.

[0007] The welding wire in the present invention can form a high-strength, tough, wear-resistant and impact-resistant alloy system through surfacing. The hardness of this alloy system reaches HRC58-65, and it can meet the severe service environments of high temperature, high variable load, thermal cycling, corrosion, wear and fatigue in steel plate rolling.

[0008] The functions of the main alloying elements in the metal powders are as follows: W and C form WC in the surfacing layer to ensure the red hardness of the roll at the service temperature. At the same time, Cr, Mo, V, and Nb also form carbides, and the carbide strengthening phases generated by the combined action of various alloys ensure the strength, hardness and wear resistance of the surfacing layer. V can refine the grain size, making it have a certain toughness and being able to withstand impact. Elements Si, Mn, and Mo not only improve the hardenability, but mainly dissolve in the matrix, playing a role in strengthening the matrix structure and improving the tempering stability of the surfacing layer. Trace element B plays a significant role in enhancing the high-temperature creep performance in the surfacing layer. The mechanism is that B can accumulate at the grain boundaries of the grains at high temperature, hindering the deformation of the grain boundaries and also inhibiting the growth of grains. Ge plays a key role in balancing the toughness and strength of the surfacing layer, enabling the surfacing layer to withstand high-energy ultrasonic impact without cracking or breaking while maintaining high surface hardness.

[0009] Preferably, the number of the seamless tubular welding wires is 5-7, the diameter of a single wire is 1.2 mm, and the mass ratio of titanium iron powder and boron oxide powder is 10:1.

[0010] On the other hand, the present invention discloses a preparation method of the above tubular composite welding wire, including the following steps:

[0011] (1) Mix chromium metal powder, tungsten metal powder, molybdenum metal powder, germanium metal powder, ferroniobium powder, ferroniobium powder, graphite powder, ferromanganese powder, and ferrosilicon powder according to the element ratio to obtain a metal alloy mixed powder; the element ratio is 0.35 - 0.45 wt% C, 1.40 - 1.80 wt% Mn, 0.60 - 0.90 wt% Si, 7.00 - 8.00 wt% Cr, 1.60 - 1.95 wt% Mo, 0.80 - 0.95 wt% V, 0.50 - 1.20 wt% Nb, 3.00 - 4.00 wt% W, 0.05 - 0.1 wt% Ge, S < 0.040 wt%, P < 0.040 wt%, and the balance is Fe;

[0012] (2) Trace B is achieved by adding a titanium-boron additive. Ti and B₂O₃ undergo a metallurgical chemical reaction during the arc metallurgy process and are reduced into the surfacing layer metal, i.e., 3Ti + 2B₂O₃ → 3TiO₂ + 4B. The titanium-boron additive powder is composed of a mixture of ferrotitanium powder and boron oxide powder. The Ti content in the ferrotitanium powder is 25 - 35 wt%, and the boron oxide powder is a chemical grade reagent powder with B₂O₃ ≥ 99.9 wt%. Mix the titanium-boron additive powder and the metal alloy mixed powder evenly according to the ratio of adding 3 grams of titanium-boron additive powder per 1000 grams of metal alloy mixed powder;

[0013] (3) Use a low-carbon steel strip to wrap the metal powder into a tube shape. After longitudinally welding and sealing the formed steel strip, draw it into a seamless tubular wire;

[0014] (4) Twist the seamless tubular wire into a spiral shape to obtain a tubular composite wire.

[0015] Preferably, in step (2), the metal powder should meet the following requirements: in the alloy powder, S < 0.015 wt%, P < 0.020 wt%, tungsten metal powder W > 99.5 wt%, chromium metal powder Cr > 99.5 wt%, molybdenum metal powder Mo > 99.9 wt%, ferroniobium powder V > 40 wt%, ferroniobium powder Nb > 50%, graphite C > 99 wt%, ferromanganese powder Mn > 65 wt%, ferrosilicon powder Si > 75 wt%, germanium powder Ge > 99.5 wt%, the Ti content in the ferrotitanium powder is 25 - 35 wt%, B₂O₃ in the boron oxide powder ≥ 99.9 wt%, and the particle size of the metal powder is 150 - 300 mesh. If the particle size of the metal powder is too large, it will exacerbate the uneven distribution of components in the surfacing layer; if the particle size is too small, the fluidity will be insufficient during the process of filling the welding core, affecting the continuity of filling the welding core and also resulting in uneven surfacing components. The seamless tubular wire ensures that the metal powder in the wire does not leak out due to the twisting and cracking of the rolled seam during the stranding of the wire in the stranding machine.

[0016] Preferably, in step (3), the filling rate of the metal powder in the seamless tubular wire is 16-20%, and the welding method is a high-frequency induction welding method or a laser welding method. The low-carbon steel strip meets the following composition requirements: C≤0.04wt%, Mn: 0.15-0.35wt%, Si≤0.040wt%, S≤0.008wt%, P≤0.012wt%, Al≤0.020wt%, N≤0.0030wt%, O≤0.0050wt%.

[0017] More preferably, the filling rate of the metal powder is controlled at about 18% to ensure that sufficient alloying elements in the surfacing process are transferred to the surfacing layer. The filling rate is the mass ratio of the metal powder in the unit length of the seamless tubular wire.

[0018] The third aspect of the present invention discloses the application of the above tubular composite wire in the surfacing repair of rolls.

[0019] Specifically, the steps of applying the tubular composite wire to repair the roll include:

[0020] S1. Using the tubular composite wire as the filling material, surfacing on the roll surface with a gas metal arc welding to obtain a wear-resistant surfacing layer;

[0021] S2. Ultrasonic impact the surfacing part of the roll until the surface hardness is stabilized at HRC58-65.

[0022] Since the seamless tubular wire is helically composite, during the surfacing process, a single-strand seamless tubular wire feeds into the molten pool along a helical rotation, and the arc generates self-rotation to form a strong stirring effect on the molten pool metal. The rotation of the arc makes the physical factors uniform in the circumferential direction, and the arc pressure and heat distribution of the entire molten pool can reach uniform consistency. With the aid of the stirring effect of the rotating arc, the surfacing metal can be fully mixed and homogenized, avoiding the uneven hardness caused by non-uniform composition to the greatest extent, and further avoiding the premature damage of the local micro-region with low hardness on the surface during the use of the roll.

[0023] The present invention also uses ultrasonic impact technology to strengthen the repaired surface with nanocrystalline refinement. A high-power ultrasonic impact tool is used to impact the surface of the surfacing layer at a frequency of more than 20,000 times per second. Due to the high frequency, high efficiency and large energy under focusing of ultrasonic waves, large plastic deformation is generated on the metal surface layer, enabling strain strengthening of local weak areas, thereby avoiding premature failure of these micro-regions during use. At the same time, ultrasonic impact can eliminate the original residual stress field. Under high-energy impact, the surface temperature of the surfacing metal rises rapidly and then cools quickly, causing changes in the surface metal structure of the affected area, and the impact area is strengthened. When the surfacing hard surface layer is treated with optimized ultrasonic impact parameters, a nanocrystalline layer and a plastic strengthening layer of a certain thickness are formed on the surface, with high-strength and tough mechanical properties at the nanoscale. At the same time, the improvement of residual stress also significantly improves the fatigue performance, having a significant impact on extending the service life of the roll.

[0024] Through the synergistic effect of rotary arc surfacing with seamless tubular composite wire and ultrasonic impact, rotary arc surfacing obtains the basic mechanical properties of the surfacing layer, and high-energy ultrasonic impact makes up for the performance weakness caused by uneven composition in local micro-regions of the surfacing layer, effectively solving the premature failure caused by insufficient low hardness and impact resistance in local micro-regions, overall improving the service performance of the roll and achieving the purpose of extending the service life of the roll.

[0025] Preferably, in step S1, when the diameter of the roll ≥ 500 mm, the surface of the roll is preheated to above 250 °C before surfacing.

[0026] Preferably, in step S2, the parameters of ultrasonic impact are that the shock wave frequency is 10 - 25 kHz and the impact current is 1.5 - 2.5 A. The following effects need to be obtained by ultrasonic impact: when the ultrasonic vibration energy is transmitted into the surfacing layer, plastic deformation with a depth of 1 - 2 mm is generated on the surfacing surface of the high-energy impact area, and the surface grains are refined to the order of 20 - 50 nm. During this process, the grains are broken and refined through the interaction between internal dislocations and reformed into nanocrystals. The surface nanocrystalline strengthening layer is about 100 μm thick. At this time, the microhardness of the surface nanocrystals can be increased by about 30% - 40% compared with the core, resulting in an increase in the microhardness and wear resistance of the roll surface layer, achieving the purpose of extending the life.

[0027] Preferably, in step S1, the composition of the wear-resistant surfacing layer is: 0.35 - 0.45 wt% C, 1.40 - 1.80 w% Mn, 0.60 - 0.90 wi% Si, 7.00 - 8.00 wt% Cr, 1.60 - 1.95 wt% Mo, 0.80 - 0.95 wt% V, 3.00 - 4.00 wt% W, 0.50 - 1.20 wt% Nb, 0.002 - 0.004 wt% B, 0.05 - 0.1 wt% Ge, S < 0.040%, P < 0.040%, and the balance is Fe.

[0028] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages:

[0029] 1) The present invention uses the self-rotating arc surfacing technology for roll surfacing repair. By means of the rotation of the arc, the stirring effect of the molten pool is enhanced, promoting the formation of a circumferential flow field inside the fluid, making the chemical components inside the molten pool mix as evenly as possible, and reducing macroscopic component segregation. Thus, a surfacing layer with homogeneous composition and properties is obtained, solving the technical problem of premature breakage at the low-hardness surface of local weak micro-regions during the use of the roll caused by the uneven hardness of traditional inhomogeneous components.

[0030] 2) When ultrasonic impact is adopted in the present invention, the ultrasonic vibration energy is transmitted into the surfacing layer, and plastic deformation with a depth of 1 - 2 mm occurs on the surfacing surface in the high-energy impact area, and the surface grains are refined to the order of 20 - 50 nm. During this process, through the interaction between internal dislocations of the grains, the original grains are broken and refined and re-form into nanocrystals. The surface nanocrystal strengthening layer is about 100 μm thick. At this time, the microhardness of the surface nanocrystals can be increased by about 30% - 40% compared with the core, resulting in an increase in the microhardness and wear resistance of the roll surface layer, achieving the purpose of extending the service life. Description of the Drawings

[0031] Figure 1 is a schematic diagram of a seamless tubular composite welding wire;

[0032] Figure 2 is the effect of the rotating arc stirring the molten pool formed by welding the seamless tubular composite welding wire;

[0033] Figure 3 is a schematic diagram of a special conductive nozzle for the seamless tubular composite welding wire;

[0034] Figure 4 is a schematic diagram of roll surfacing;

[0035] Figure 5 is a schematic diagram of ultrasonic impact;

[0036] Figure 6 is a photo of the hardness test result of the specimen before ultrasonic impact on the surfacing layer in Example 1;

[0037] Figure 7 is a photo of the hardness test result of the specimen after ultrasonic impact treatment on the surfacing layer in Example 1. Detailed Embodiments

[0038] The technical solution of the present invention will be further described below in conjunction with the drawings.

[0039] Example 1: The composition and preparation method of a tubular composite welding wire are as follows:

[0040] (1) Dry mix chromium metal powder, tungsten metal powder, molybdenum metal powder, germanium metal powder, ferroniobium powder, ferrotitanium powder, graphite powder, ferromanganese powder, ferrosilicon powder, and ferroboron powder in a blender according to the following element ratios for 30 minutes, and then pass through a 200-mesh sieve to obtain a metal alloy mixed powder:

[0041] 0.4wt% C, 1.6wt% Mn, 0.75wt% Si, 7.5wt% Cr, 1.8wt% Mo, 0.88wt% V, 0.85wt% Nb, 3.5wt% W, 0.075wt% Ge, impurity S < 0.040wt%, P < 0.040wt%, and the balance is Fe;

[0042] In the metal alloy mixed powder, S < 0.015wt%, P < 0.020wt%, tungsten metal powder W > 99.5wt%, chromium metal powder Cr > 99.5wt%, molybdenum metal powder Mo > 99.9wt%, ferroniobium powder V > 40wt%, ferrotitanium powder Nb > 50%, graphite C > 99wt%, ferromanganese powder Mn > 65wt%, ferrosilicon powder Si > 75wt%, and germanium powder Ge > 99.5wt%;

[0043] The titanium-boron additive powder is prepared by mixing ferrotitanium powder and boron oxide powder in a mass ratio of 10:1. Among them, the ferrotitanium powder has a Ti content of 25 - 35wt%, and the boron oxide powder is a chemical grade reagent powder with B2O3 ≥ 99.9wt%. Mix the titanium-boron additive and the metal alloy mixed powder evenly according to the ratio of adding 3 grams of titanium-boron additive powder per 1000 grams of metal alloy mixed powder to obtain a metal powder.

[0044] (2) Use a low-carbon steel strip to wrap the metal powder into a tube shape, and after high-frequency induction welding and sealing the longitudinal seam of the formed steel strip, draw it into a seamless tubular wire with a diameter of 1.2 mm. The filling rate of the metal powder in the seamless tubular wire is 18%. The low-carbon steel strip meets the following composition requirements: C ≤ 0.04wt%, Mn: 0.15 - 0.35wt%, Si ≤ 0.040wt%, S ≤ 0.008wt%, P ≤ 0.012wt%, Al ≤ 0.020wt%, N ≤ 0.0030wt%, O ≤ 0.0050wt%.

[0045] (3) Use a stranding machine to strand 5 seamless tubular wires into a spiral composite wire, as Figure 1 shown, that is, a tubular composite wire is obtained.

[0046] The tubular composite wire prepared by the above method is used to repair the rolling rolls for steel rolling, and the method is as follows:

[0047] S1. Grind, degrease and rust the surface of the roller to keep the surface clean and of metallic color. For large-diameter rollers over 500 mm repaired by surfacing welding, the surfacing layer has a large rigidity. If many cracks are found during welding, the surface of the roller can be preheated to 250°C by wrapping an electric belt heater before welding, and then surfacing welding is performed to obtain a wear-resistant surfacing layer. The composition of the wear-resistant surfacing layer is: 0.4wt% C, 1.6wt% Mn, 0.75wt% Si, 7.5wt% Cr, 1.8wt% Mo, 0.88wt% V, 0.85wt% Nb, 3.5wt% W, 0.075wt% Ge, 0.003wt% B, impurities S<0.040wt%, P<0.040wt%, and the remainder is Fe.

[0048] S2. Use the prepared tubular composite welding wire as the filling material and use two consumable argon arc welding machines to perform surfacing welding on both ends of the roller at the same time. During the surfacing welding process, the welding gun is aimed at the surface of the workpiece to be welded and remains fixed. The roller is clamped on the tooling machine and rotates. The welding completes the surfacing repair of the entire circumference of the roller. Figure 4 As shown. After the surfacing is completed and cooled, the roller surface is machined to above level 8, and ultrasonic non-destructive testing is used to ensure that the surfacing layer has no micro crack defects. If ultrasonic testing finds defects such as cracks, the defective parts can be removed by grinding with a grinding wheel, and then repaired by manual TIG welding with a single seamless tubular welding wire that is not composited, and then the surface is ground until it is smooth with the roller surface.

[0049] In order to carry out destructive testing on the cladding layer, a small test piece of the same material can be fixed on the side of the roller while cladding the roller, and cladding with the same parameters can be carried out according to the roller specifications to provide analysis samples for testing and subsequent ultrasonic impact.

[0050] Welding wire feeding needs to be Figure 3 The special conductive nozzle with elastic clamping is shown. The elastic force is used to force the welding wire to contact and conduct electricity with the inner wall of the conductive nozzle, avoiding the loose contact and poor conductivity caused by the formation of grooves due to long-term friction, so as to ensure that the welding wire stably conducts the welding current and the arc in the cladding process is stable.

[0051] S3, clamp the roller on the fixture to rotate it, and use ultrasonic impact equipment to perform high-energy impact, such as Figure 5As shown. During the impact process, the impact needle remains stationary, vertically aligned with the cylinder surface, and a slight pressure is applied. As the roller rotates, the impact needle slowly and dynamically impacts the surfacing area along the previous surfacing path. The shock wave frequency is 18 kHz, and the impact current is 2 A. If the hardness value range is not met, ultrasonic impact can be continued on the local area. The surface nano-structured gradient obtained by the above impact effect can be verified by observing with a metallographic microscope and a scanning electron microscope (SEM). For the small surfacing test piece fixedly attached to the side of the roller, after impact according to the same parameters as above, specimens for metallographic and SEM observations can be obtained by wire cutting along the cross-section line.

[0052] S4. After the collaborative processing of surfacing and ultrasonic impact is completed and the hardness of the surfacing repair area is detected, then machining is carried out to the dimensions required by the design drawing. The hardness test results show the effective effect of ultrasonic impact as Figure 6 、 Figure 7 shown: The hardness test values before ultrasonic treatment are HRC 56.1 and HRC 55.2, while after ultrasonic treatment of the same specimen, they increase to HRC 64.3 and HRC 64.9.

[0053] Example 2: The rest are the same as in Example 1, except that:

[0054] The element ratio in the metal alloy mixed powder is:

[0055] 0.35 wt% C, 1.40 wt% Mn, 0.60 wt% Si, 7.00 wt% Cr, 1.60 wt% Mo, 0.80 wt% V, 0.50 wt% Nb, 3.00 wt% W, 0.05 wt% Ge, S < 0.040 wt%, P < 0.040 wt%, and the balance is Fe;

[0056] In the used metal alloy mixed powder, S < 0.015 wt%, P < 0.020 wt%, metal tungsten powder W > 99.5 wt%, metal chromium powder Cr > 99.5 wt%, metal molybdenum powder Mo > 99.9 wt%, ferrovanadium powder V > 40 wt%, ferroniobium powder Nb > 50%, graphite C > 99 wt%, ferromanganese powder Mn > 65 wt%, ferrosilicon powder Si > 75 wt%, germanium powder Ge > 99.5 wt%, and the particle size of the metal powder is 150 - 300 mesh;

[0057] Laser welding is used for the longitudinal seam, the diameter of the seamless tubular wire is 1.5 mm, and the filling rate of the metal powder in the seamless tubular wire is 16%.

[0058] A stranding machine is used to twist 7 seamless tubular wires into a helical composite wire.

[0059] The composition of the wear-resistant surfacing layer is: 0.35 wt% C, 1.40 wt% Mn, 0.60 wt% Si, 7.00 wt% Cr, 1.60 wt% Mo, 0.80 wt% V, 0.50 wt% Nb, 3.00 wt% W, 0.05 wt% Ge, 0.003 wt% B, with impurities S < 0.040 wt% and P < 0.040 wt%, and the balance being Fe.

[0060] The frequency of the ultrasonic shock wave is 10 kHz, and the shock current is 2.5 A.

[0061] Example 3: The rest is the same as in Example 1, except that:

[0062] The element ratio in the metal alloy mixed powder is:

[0063] 0.45 wt% C, 1.80 wt% Mn, 0.90 wt% Si, 8.00 wt% Cr, 1.95 wt% Mo, 0.95 wt% V, 1.20 wt% Nb, 4.00 wt% W, 0.1 wt% Ge, S < 0.040 wt%, P < 0.040 wt%, and the balance being Fe;

[0064] In the metal alloy mixed powder used, S < 0.015 wt%, P < 0.020 wt%, metal tungsten powder W > 99.5 wt%, metal chromium powder Cr > 99.5 wt%, metal molybdenum powder Mo > 99.9 wt%, ferrovanadium powder V > 40 wt%, ferroniobium powder Nb > 50%, graphite C > 99 wt%, ferromanganese powder Mn > 65 wt%, ferrosilicon powder Si > 75 wt%, germanium powder Ge > 99.5 wt%, and the particle size of the metal powder is 150 - 300 mesh;

[0065] A laser welding longitudinal seam is adopted, the diameter of the seamless tubular wire is 1.2 mm, and the filling rate of the metal powder in the seamless tubular wire is 20%.

[0066] The composition of the wear-resistant surfacing layer is: 0.45 wt% C, 1.80 wt% Mn, 0.90 wt% Si, 8.00 wt% Cr, 1.95 wt% Mo, 0.95 wt% V, 1.20 wt% Nb, 4.00 wt% W, 0.1 wt% Ge, 0.003 wt% B, with impurities S < 0.040 wt% and P < 0.040 wt%, and the balance being Fe.

[0067] The frequency of the ultrasonic shock wave is 25 kHz, and the shock current is 1.5 A.

[0068] Comparative Example 1: The rest is the same as in Example 1, except that:

[0069] No metal germanium powder is added to the metal alloy mixed powder.

[0070] Comparative Example 2: The rest is the same as in Example 1, except that:

[0071] The germanium metal powder is replaced with tin metal powder.

[0072] The hardness of the surfacing repair areas in Examples 1-3 and Comparative Examples 1-2 and whether there are cracks after ultrasonic impact are respectively detected. Different 10 places are randomly selected for detection at the surfacing repair areas, and the area of each place is about 5 cm × 5 cm. The results are as follows:

[0073] Table 1 Influence of different metal powders on the surfacing repair effect

[0074] Group Hardness (HRC) Total number of cracks (pcs) Example 1 64.5±0.4 0 Example 2 63.2±0.6 0 Example 3 62.9±0.7 0 Comparative Example 1 67.9±1.5 8 Comparative Example 2 52.1±1.8 13

[0075] As can be seen from the results in Table 1, although the addition of germanium element reduces the hardness of the surfacing repair layer, the reduction amplitude is small and can meet the working requirements of the roll. More importantly, the germanium element effectively improves the plastic deformation ability of the surfacing repair layer, so that the surfacing repair layer will not crack under ultrasonic impact, and further improves the hardness after ultrasonic impact, and the hardness dispersion decreases, and the hardness uniformity is significantly improved. When the germanium element is replaced with the tin element, not only the hardness is greatly reduced, but also a large number of impact cracks appear, indicating that the tin element does not have the effect of improving the plastic deformation ability of the surfacing repair layer, and the welding wire containing the tin element cannot adapt to the ultrasonic impact process.

Claims

1. A tubular composite welding wire, characterized in that, A tubular composite wire is made by helically twisting several seamless tubular welding wires. The seamless tubular welding wire includes a tubular wrapper and metal powder filled inside the tubular wrapper. The metal powder includes metal chromium powder, metal tungsten powder, metal molybdenum powder, metal germanium powder, ferroniobium powder, ferrovanadium powder, graphite powder, ferromanganese powder, ferrosilicon powder, and a titanium-boron additive. The titanium-boron additive is prepared by mixing ferrotitanium powder and boron oxide powder.

2. The tubular composite welding wire according to claim 1, wherein, The number of the seamless tubular welding wires is 5 - 7, the diameter of a single wire is 1.2 mm, and the mass ratio of ferrotitanium powder to boron oxide powder is 10:

1.

3. The preparation method of the tubular composite welding wire according to claim 1 or 2, characterized in that, It includes the following steps: (1) Mix metal chromium powder, metal tungsten powder, metal molybdenum powder, metal germanium powder, ferroniobium powder, ferrovanadium powder, graphite powder, ferromanganese powder, and ferrosilicon powder according to the element ratios to obtain a metal alloy mixed powder; the element ratios are 0.35 - 0.45 wt% C, 1.40 - 1.80 wt% Mn, 0.60 - 0.90 wt% Si, 7.00 - 8.00 wt% Cr, 1.60 - 1.95 wt% Mo, 0.80 - 0.95 wt% V, 0.50 - 1.20 wt% Nb, 3.00 - 4.00 wt% W, 0.05 - 0.1 wt% Ge, S < 0.040 wt%, P < 0.040 wt%, and the balance is Fe; (2) Mix the titanium-boron additive and the metal alloy mixed powder evenly according to the ratio of adding 3 grams of titanium-boron additive powder per 1000 grams of metal alloy mixed powder to obtain metal powder; (3) Wrap the metal powder with low-carbon steel strip into a tube, and use high-frequency induction welding or laser welding to seal the longitudinal seam of the formed steel strip, and then draw it into a seamless tubular welding wire; (4) Twist the seamless tubular welding wires into a spiral shape to obtain the tubular composite wire.

4. The preparation method of the tubular composite welding wire according to claim 3, wherein, In step (2), the metal powder used should meet the following requirements: in the alloy powder, S < 0.015 wt%, P < 0.020 wt%, metal tungsten powder W > 99.5 wt%, metal chromium powder Cr > 99.5 wt%, metal molybdenum powder Mo > 99.9 wt%, ferrovanadium powder V > 40 wt%, ferroniobium powder Nb > 50%, graphite C > 99 wt%, ferromanganese powder Mn > 65 wt%, ferrosilicon powder Si > 75 wt%, germanium powder Ge > 99.5 wt%, the Ti content in ferrotitanium powder is 25 - 35 wt%, B2O3 in boron oxide powder ≥ 99.9 wt%, and the particle size of the metal powder is 150 - 300 mesh.

5. The method for preparing the seamless tubular welding wire according to claim 3, wherein In step (3), the filling rate of the metal powder in the seamless tubular welding wire is 16 - 20%, the welding method is high-frequency induction welding method or laser welding method, and the low-carbon steel strip meets the following composition requirements: C ≤ 0.04 wt%, Mn: 0.15 - 0.35 wt%, Si ≤ 0.040 wt%, S ≤ 0.008 wt%, P ≤ 0.012 wt%, Al ≤ 0.020 wt%, N ≤ 0.0030 wt%, O ≤ 0.0050 wt%.

6. Application of the tubular composite wire according to claim 1 or 2 in roll surfacing repair.

7. The application according to claim 6, characterized in that, It includes the following steps: S1. Using the tubular composite welding wire as the filler material, perform surfacing on the surface of the roll by gas metal arc welding to obtain a wear-resistant surfacing layer; S2. Perform ultrasonic impact on the surfacing part of the roll until the surface hardness is stabilized at HRC58 - 65.

8. The application according to claim 7, wherein, In step S1, when the diameter of the roll is ≥500 mm, preheat the surface of the roll to above 250 °C before surfacing.

9. The application according to claim 7, wherein In step S2, the parameters of ultrasonic impact are: the shock wave frequency is 10 - 25 kHz, and the impact current is 1.5 - 2.5 A.

10. The application according to claim 7, characterized in that, In step S1, the composition of the wear-resistant surfacing layer is: 0.35 - 0.45 wt% C, 1.40 - 1.80 w% Mn, 0.60 - 0.90 wi% Si, 7.00 - 8.00 wt% Cr, 1.60 - 1.95 wt% Mo, 0.80 - 0.95 wt% V, 3.00 - 4.00 wt% W, 0.50 - 1.20 wt% Nb, 0.002 - 0.004 wt% B, 0.05 - 0.1 wt% Ge, S < 0.040%, P < 0.040%, and the balance is Fe.

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