A high-wear-resistance and impact-resistance composite surfacing material and automatic surfacing process special for stirring main machine lining plate / blade

Abstract

This invention discloses a high-wear-resistant and impact-resistant composite surfacing material and an automated surfacing process for agitator liner / blade. The surfacing material is a metal powder-cored welding wire, whose core powder composition, by weight percentage, includes: C: 0.8%~1.5%, Cr: 5.0%~8.0%, Mo: 2.0%~4.0%, V: 1.0%~2.5%, Nb: 0.5%~1.5%, WC: 20%~35%, with the balance being iron. After surfacing, a microscopic composite structure of "tough matrix embedded with multi-scale hard phases" is formed, with a 2~10 micrometer metallurgical reaction transition zone formed between the WC particles and the matrix interface. The automated surfacing process includes: pretreatment and matrix evaluation, three-dimensional digital reconstruction and adaptive path planning, precise heat input control based on the line energy formula, dynamic interpass temperature management, and a controllable slow cooling step. This invention, through synergistic innovation in materials and processes, achieves a weld overlay hardness ≥60HRC, an impact energy ≥28J, and a repair lifespan 1.5 to 2.2 times that of a new part, solving the technical problems of short lifespan and unstable repair quality of vulnerable parts in the mixing host.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of materials science and advanced manufacturing technology, and specifically relates to a high wear-resistant and impact-resistant composite surfacing material for stirring host liner / blade and an automated surfacing process. Background Technology

[0002] The mixing unit is a core piece of equipment in concrete production, mining and metallurgy, building materials and cement industries. Its internal linings and blades endure intense scouring, compression, and high-stress impact wear from materials such as concrete aggregates, mineral sands, and asphalt mixtures during operation, making them typical wear parts. Traditionally, these components are mainly made of high-manganese steel (such as Mn13), medium-carbon alloy steel, or wear-resistant steel plates (such as the Hardox series). Although these materials possess certain initial strength and wear resistance, their hardness and wear resistance reserves are still insufficient under long-term, harsh operating conditions, resulting in short component lifespans and frequent downtime for replacement. This not only increases spare parts procurement costs but also causes significant production losses due to downtime.

[0003] Currently, the most common approach to repairing and strengthening worn parts is manual arc welding. Operators use commercially available general-purpose wear-resistant welding rods to deposit welding material on the worn areas to restore dimensions and enhance surface wear resistance. However, manual welding has revealed several systemic drawbacks in practical applications: First, the repair quality heavily relies on the individual skill level of the welder, resulting in inconsistent weld formation and internal defects such as porosity, slag inclusions, and lack of fusion, leading to significant fluctuations in the lifespan of the repaired parts. Second, the alloy system design of conventional welding materials is often simplistic, prioritizing high hardness at the expense of toughness. This makes it difficult to simultaneously meet the dual requirements of abrasive wear resistance and mechanical impact resistance under stirring conditions; excessive hardness leads to cracking and spalling, while excessive toughness results in rapid wear. Third, the heat input control in manual operations relies entirely on experience, easily causing overheating of the base material, deterioration of the heat-affected zone, large workpiece deformation, and even inducing welding hot cracks. Fourth, the repair efficiency is low, the labor intensity is high, the working environment is harsh, and the overall cost-effectiveness is poor. Although semi-automatic flux-cored wire gas shielded welding was subsequently developed, it has poor adaptability to complex curved surfaces, and the process parameters still need to be optimized manually, failing to fundamentally solve the problems of quality consistency and efficiency.

[0004] Therefore, there is an urgent need in this field to develop a specialized surfacing material that can synergistically improve wear resistance and impact resistance, along with a highly efficient, stable, and precisely controllable automated surfacing process. This material should possess a specific microstructure design, enabling it to effectively resist cyclic impact loads without macroscopic brittle fracture while withstanding severe abrasive wear. The corresponding process should fully utilize digital and robotic technologies to achieve precise planning and execution of the complex surface repair process, thereby completely eliminating human uncertainties and significantly extending the service life of repaired components beyond that of new parts. This would fundamentally solve the technical challenges of short lifespan and high maintenance costs associated with mixing unit liners and blades. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high wear-resistant and impact-resistant composite surfacing material and an automated surfacing process for agitator liner / blade.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention first provides a high wear-resistant and impact-resistant composite surfacing material for agitator liner / blade. The surfacing material is characterized by being a metal powder-cored welding wire with a low-carbon steel strip outer sheath. The chemical composition of the core powder, by weight percentage, includes: carbon (C): 0.8%~1.5%, chromium (Cr): 5.0%~8.0%, molybdenum (Mo): 2.0%~4.0%, vanadium (V): 1.0%~2.5%, niobium (Nb): 0.5%~1.5%, tungsten carbide (WC) particles: 20%~35%, and the balance being iron powder. The composite surfacing material forms a micro-composite structure of "tough matrix embedded with multi-scale hard phase" after surfacing. The micro-composite structure is composed of a martensitic / bainitic multiphase matrix, submicron to micron-sized (Cr,Fe)7C3 type eutectic carbides precipitated in situ, dispersed nano-sized vanadium carbides (VC) and nano-sized niobium carbides (NbC), and incompletely molten micron-sized tungsten carbide (WC) particles. The tungsten carbide (WC) particles form a thin metallurgical reaction transition zone at the interface with the matrix, and the thickness of the metallurgical reaction transition zone is 2 to 10 microns.

[0007] Furthermore, the present invention also provides an automated surfacing process for implementing the above-mentioned composite surfacing material, characterized by comprising the following steps: a. Pretreatment and substrate assessment steps: After non-destructive testing of the workpiece to be repaired to confirm that there are no deep cracks, sandblasting is performed to remove surface contaminants; and the hardness of the substrate in the area to be repaired is measured by a portable hardness tester. When the hardness of the substrate is lower than a preset threshold, a transition layer is pre-welded to restore the strength of the substrate. b. Three-dimensional digital reconstruction and adaptive path planning steps: Use a 3D scanner to acquire point cloud data of the workpiece surface, and compare it with the original CAD model to generate a "defect model"; Based on the defect model, automatically calculate and generate a multi-layer, multi-pass welding path in the robot offline programming software. The path planning algorithm includes: automatically constraining the angle between the welding torch axis and the local curved surface normal of the welding point within the range of 90°±10°; adaptively adjusting the weld overlap for different repair layers, with the bottom layer overlap at 40%~50% and the surface layer overlap at 30%~40%; and automatically generating the welding sequence from high-stiffness areas to low-stiffness areas according to the workpiece structural stiffness distribution. c. Precise setting of welding parameters and control of heat input: Using a mixed shielding gas of 80% argon (Ar) and 20% carbon dioxide (CO2), set the welding current range to 200~280 amperes (A), the arc voltage range to 26~32 volts (V), and the welding speed range to 300~450 mm / min. Calculate and control the welding heat input (Q) in real time according to the following formula to stabilize it within the target range of 10~20 kJ / cm: In the formula, Q is the welding line energy, in kilojoules per centimeter (kJ / cm); η is the arc thermal efficiency constant determined according to the composition of the shielding gas, with a value of 0.75~0.85; U is the arc voltage, in volts (V); I is the welding current, in amperes (A); and v is the welding speed, in centimeters per minute (cm / min). d. Perform welding and dynamic interpass temperature management steps: Use a six-axis industrial robot to perform welding operations, monitor the temperature of the welding area in real time through infrared temperature sensors, and adopt a zoned alternating welding strategy to dynamically control the interpass temperature below 150℃. For thin-walled workpieces with a thickness of less than 20 mm, the interpass temperature is further controlled below 120℃. e. Controlled slow cooling and stress release steps: After the welding is completed, the workpiece is placed in a closed space wrapped with insulation material and slowly cooled to room temperature at a cooling rate of no more than 5°C / minute. During the cooling process, the workpiece is subjected to sub-resonant frequency mechanical vibration through a vibration aging device to actively release residual stress.

[0008] Compared with the prior art, this application has the following beneficial effects: This invention provides a high wear-resistant and impact-resistant composite surfacing material for stirring host liners / blades. By precisely controlling the content and ratio of carbon, chromium, molybdenum, vanadium, niobium, and tungsten carbide particles, a "tough matrix embedded with multi-scale hard phase" micro-composite structure is constructed in the surfacing layer. This structure consists of a strong and tough martensitic / bainitic multiphase matrix, in-situ precipitated submicron to micron-sized (chromium, iron) 7-carbon type eutectic carbides, dispersed nano-sized vanadium carbides and niobium carbides, and incompletely melted micron-sized tungsten carbide particles. At the same time, the 2-10 micron thin metallurgical reaction transition zone formed at the interface between the tungsten carbide particles and the matrix effectively avoids excessive dissolution and failure of the tungsten carbide particles while ensuring the interfacial bonding strength. This unique microstructure endows the weld overlay with excellent comprehensive mechanical properties: on the one hand, the large number of dispersed micron-sized tungsten carbide particles serve as the first line of defense against abrasive wear, and the in-situ precipitated nano-sized carbides further enhance the microhardness and resistance to tempering softening of the matrix through dispersion strengthening, making the macroscopic Rockwell hardness of the weld overlay no less than 60 HRC. In wear tests under simulated working conditions, the volumetric wear is only one-third that of high manganese steel. On the other hand, the composite toughening effect of elements such as molybdenum and niobium, as well as the fine-grained structure formed by precise control of the welding process, enable the weld overlay to maintain excellent impact toughness while possessing high hardness. The Charpy V-notch impact energy is no less than 28 Joules, effectively solving the technical problem of easy brittle fracture and spalling of conventional high-hardness weld overlays. The accompanying automated surfacing process, through three-dimensional digital reconstruction, adaptive path planning, precise heat input control based on the line energy formula, and zoned alternating welding and dynamic interpass temperature management, ensures that the microstructure design of the aforementioned composite surfacing material can be completely and consistently reproduced on complex curved workpieces. This completely eliminates the quality fluctuations of manual surfacing and significantly reduces welding deformation and cracking tendency. Through synergistic innovation in materials and processes, this invention enables the repaired liners and blades to achieve a service life of 1.5 to 2.2 times that of new parts under harsh operating conditions, reducing overall maintenance costs by more than 40%. Furthermore, this technical solution can be extended to the remanufacturing of various heavily worn components in mining, cement, power, and shipbuilding industries, resulting in significant economic and social benefits. Attached Figure Description

[0009] Figure 1 This is an automated welding process flow diagram for a high wear-resistant and impact-resistant composite welding material specifically for mixing host liner / blade. Detailed Implementation

[0010] 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.

[0011] Furthermore, in this invention, an element referred to as fixed to or disposed on another element may be directly disposed on the other element, or there may be an intermediate element. When an element is considered to be connected to another element, it may be directly connected to the other element, or there may be an intermediate element present simultaneously. The terms vertical, horizontal, left, right, and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0012] This application provides a high wear-resistant and impact-resistant composite surfacing material for agitator liner / blade. The surfacing material is a metal powder cored flux-cored wire with a low-carbon steel strip outer sheath. The chemical composition of the core powder, by weight percentage, includes: carbon (C): 0.8%~1.5%, chromium (Cr): 5.0%~8.0%, molybdenum (Mo): 2.0%~4.0%, vanadium (V): 1.0%~2.5%, niobium (Nb): 0.5%~1.5%, tungsten carbide (WC) particles: 20%~35%, and the balance being iron powder. The composite surfacing material forms a micro-composite structure of "tough matrix embedded with multi-scale hard phase" after surfacing. The micro-composite structure is composed of a martensitic / bainitic multiphase matrix, submicron to micron-sized (Cr,Fe)7C3 type eutectic carbides precipitated in situ, dispersed nano-sized vanadium carbides (VC) and nano-sized niobium carbides (NbC), and incompletely molten micron-sized tungsten carbide (WC) particles. The tungsten carbide (WC) particles form a thin metallurgical reaction transition zone at the interface with the matrix, and the thickness of the metallurgical reaction transition zone is 2 to 10 microns.

[0013] This embodiment also specifies a high-wear-resistant and impact-resistant composite surfacing material specifically for the liner / blades of a mixing host. This material is designed as a metal powder-cored welding wire, its structure consisting of a low-carbon steel strip encasing a specific ratio of alloy powder. The reason for using a flux-cored welding wire is that the composition of its internal core powder can be flexibly adjusted within a wide range, enabling precise realization of the complex multi-component alloy system designed in this invention, which is difficult to achieve with solid welding wires.

[0014] Regarding the chemical composition of the core powder, the carbon (C) content is controlled between 0.8% and 1.5% (by weight). Carbon is the basic element for forming carbides and also dissolves in the matrix to increase the hardness of martensite. When the content is below 0.8%, the number of carbides is insufficient, the matrix hardness is low, and the wear resistance cannot meet the requirements of stirring conditions. When the content is above 1.5%, the brittleness of the weld overlay increases sharply, the crack sensitivity increases significantly, and it is prone to spalling or cracking under impact loads. The chromium (Cr) content is 5.0% to 8.0%. Part of the chromium dissolves in the matrix to improve hardenability and ensure that the weld overlay obtains a strong and tough structure mainly composed of martensite or bainite. The other part combines with carbon to form (Cr,Fe)7C3 type eutectic carbides, which contribute to wear resistance as a secondary hard phase. The molybdenum (Mo) content is 2.0%–4.0%. Molybdenum dissolves in the matrix, playing a significant role in solid solution strengthening and grain refinement. It also improves hardenability and works synergistically with chromium to suppress temper brittleness, making it a key element in ensuring the toughness of the weld overlay. The vanadium (V) content is 1.0%–2.5%. Vanadium is a strong carbide-forming element, precipitating extremely fine vanadium carbides (VC) in situ during weld solidification. These fine-sized, dispersed VCs produce a strong dispersion strengthening effect, significantly improving the microhardness and resistance to temper softening of the matrix. The niobium (Nb) content is 0.5%–1.5%. Niobium preferentially forms niobium carbides (NbC), which tend to precipitate at austenite grain boundaries, effectively pinning grain boundaries and preventing grain growth, thus obtaining a fine solidification structure. Grain refinement strengthening is the only mechanism that can simultaneously improve the strength and toughness of the material. Furthermore, the addition of niobium can significantly reduce the hot cracking susceptibility of the weld metal. Tungsten carbide (WC) particles, as an added hard phase, constitute 20% to 35% of the alloy. These particles possess extremely high intrinsic hardness and are uniformly dispersed within the weld overlay, forming the first line of defense against severe abrasive wear. The remainder consists of iron powder and unavoidable trace impurities; the iron powder forms the basic carrier of the alloy system.

[0015] Furthermore, this embodiment also defines the unique micro-composite structure formed after the composite surfacing material is welded; this structure can be summarized as "tough matrix embedded with multi-scale hard phases"; specifically, the micro-composite structure is composed of the following parts: First, a martensitic / bainitic multiphase matrix, which serves as a tough skeleton supporting the hard phases, and its toughness benefits from the composite toughening effect of elements such as molybdenum and chromium, as well as the precise control of the subsequent welding process; Second, submicron to micron-sized (chromium, iron)7C3 ((Cr, Fe)7C 3) Type eutectic carbides, which are distributed in a network or stripe pattern along the grain boundaries to form a continuous wear-resistant skeleton; third, dispersed nano-sized vanadium carbide (VC) and nano-sized niobium carbide (NbC), which are extremely small in size and uniformly dispersed in the matrix, significantly improve the matrix's ability to resist plastic deformation and micro-cutting through the second-phase strengthening mechanism; fourth, incompletely molten micron-sized tungsten carbide (WC) particles, which retain the high hardness and irregular shape of the original particles, serve as the core hard phase to resist macro-abrasive plowing and gouging. More importantly, the interface between tungsten carbide (WC) particles and the matrix is ​​not a simple mechanical encapsulation, but rather forms a thin metallurgical reaction transition zone under the heat of welding. The thickness of this transition zone is precisely controlled within the range of 2-10 micrometers. This characteristic is achieved through strict control of the welding heat input: when the heat input is too low, the surface of the tungsten carbide particles does not melt sufficiently, failing to form an effective metallurgical bond, resulting in weak interfacial bonding and easy particle detachment during wear; when the heat input is too high, the tungsten carbide particles dissolve excessively. Although the interfacial bonding is enhanced, the hard phase effect of the particles themselves is weakened, and the dissolved tungsten and carbon significantly alter the matrix composition, increasing brittleness. This invention, by controlling the thickness of the transition zone to 2-10 micrometers, ensures a strong metallurgical bond between the tungsten carbide particles and the matrix while maximizing the preservation of the original high hardness and wear resistance of the tungsten carbide particles. This microstructural feature is one of the core inventive features of this invention and the fundamental reason for achieving a synergistic improvement in macroscopic high hardness and high toughness of the weld overlay.

[0016] In one specific embodiment, the tungsten carbide (WC) particles have a particle size of 60-200 micrometers and a volume fraction of 18%-30% in the weld overlay; the nano-sized vanadium carbide (VC) has an average size of 50-300 nanometers, and the nano-sized niobium carbide (NbC) preferentially precipitates along grain boundaries and forms a pinning effect, making the austenite grain size of the solidified structure of the weld overlay finer than ASTM grade 8.

[0017] In this embodiment, the composite weld overlay material is further defined; specifically, the particle size of tungsten carbide (WC) particles is limited to 60-200 micrometers. If the particle size of tungsten carbide particles is less than 60 micrometers, the risk of complete dissolution in the molten pool increases significantly, making it impossible to effectively retain them as an independent hard phase. If the particle size is greater than 200 micrometers, the suspension and uniform distribution of particles in the molten pool become difficult, and the interfacial stress concentration between large particles and the matrix is ​​more severe, making them prone to becoming crack initiation sites under impact loads. Simultaneously, the volume fraction of tungsten carbide particles in the weld overlay is limited to 18%-30%. This volume fraction is the effective hard phase proportion actually retained in the weld overlay after considering partial burn-off and dissolution during the welding process, based on an addition amount of 20%-35%. Below 18%, the improvement in wear resistance is insufficient; above 30%, the toughness and crack resistance of the weld overlay will significantly decrease.

[0018] Furthermore, the average size of nanoscale vanadium carbides (VC) was limited to 50–300 nanometers. This size range is ideal for vanadium carbides to exert their optimal dispersion strengthening effect. By controlling the welding cooling rate (i.e., through interpass temperature management and post-weld slow cooling control), vanadium carbides can be uniformly precipitated at the nanoscale during the solid-state phase transformation after solidification, rather than coarsely precipitated during liquid solidification. Simultaneously, niobium carbides (NbC) were preferentially precipitated along grain boundaries and formed a pinning effect, resulting in a finer austenitic grain size in the solidified weld overlay than ASTM grade 8. The average grain diameter corresponding to ASTM grade 8 is approximately 22 micrometers. The grain boundary pinning effect of niobium carbides effectively inhibits grain growth during the welding thermal cycle, and the fine grain structure provides an excellent strength and toughness foundation for the weld overlay.

[0019] In one specific embodiment, the internal core powder further contains 0.1% to 0.5% titanium (Ti) and / or 0.001% to 0.005% boron (B), wherein the titanium (Ti) is used for deoxidation and to form titanium nitride (TiN) particles to further refine the grains, and the boron (B) is used to segregate at grain boundaries to improve the resistance of the weld overlay to hot cracking.

[0020] This embodiment further optimizes the composite surfacing material; 0.1%~0.5% titanium (Ti) and / or 0.001%~0.005% boron (B) can be selectively added to its core powder. The addition of titanium plays two main roles: firstly, as a strong deoxidizer, titanium combines with oxygen in the molten pool to form titanium oxide (TiO2), which enters the slag, thereby purifying the weld metal and reducing porosity; secondly, titanium combines with dissolved nitrogen in the molten pool to form high-melting-point titanium nitride (TiN) particles. These particles can act as heterogeneous nucleation sites in the liquid metal, promoting grain refinement. The amount of boron added is extremely small, but its effect is significant: boron atoms tend to segregate at austenite grain boundaries, reducing the grain boundary interface energy, thereby significantly inhibiting the initiation and propagation of welding hot cracks (especially solidification cracks and liquefaction cracks). The addition of boron is particularly important for repair scenarios involving thick workpieces or high restraint.

[0021] This application also provides an automated welding process for implementing the above-mentioned composite welding materials, such as... Figure 1 As shown, it includes the following steps: a. Pretreatment and substrate assessment steps: After non-destructive testing of the workpiece to be repaired to confirm that there are no deep cracks, sandblasting is performed to remove surface contaminants; and the hardness of the substrate in the area to be repaired is measured by a portable hardness tester. When the hardness of the substrate is lower than a preset threshold, a transition layer is pre-welded to restore the strength of the substrate. In this embodiment, firstly, a comprehensive non-destructive testing (NDT) is performed on the workpiece to be repaired (such as a liner or blade), typically using magnetic particle testing or penetrant testing. The purpose is to confirm the absence of micro or macroscopic cracks within and on the surface of the base material. Any original cracks in the base material, if not detected and addressed, are highly likely to propagate under the thermal stress of subsequent welding, leading to premature fracture failure of the repaired part in its early service life. After confirming the integrity of the workpiece base, the surface is sandblasted or shot-peened. This treatment aims to thoroughly remove oxide scale, residual concrete, oil, and other contaminants formed on the workpiece surface during long-term service, until a uniform metallic color is exposed. A clean metal surface is fundamental to ensuring stable arc combustion, good wetting and spreading of the molten metal, and preventing defects such as weld porosity and slag inclusions. Furthermore, this step incorporates a base material hardness assessment: a portable hardness tester is used to measure the hardness of the base material in the area to be repaired. When the hardness of the base material significantly decreases due to long-term service or past repair experiences, falling below a preset threshold (determined based on the original properties of the base material), a transition layer is pre-welded to restore the base material strength. The design of this transition layer effectively prevents the high-hardness wear-resistant weld overlay from "collapsed" or causing interface peeling of the softened base material under stress.

[0022] b. Three-dimensional digital reconstruction and adaptive path planning steps: Use a 3D scanner to acquire point cloud data of the workpiece surface, and compare it with the original CAD model to generate a "defect model"; Based on the defect model, automatically calculate and generate a multi-layer, multi-pass welding path in the robot offline programming software. The path planning algorithm includes: automatically constraining the angle between the welding torch axis and the local curved surface normal of the welding point within the range of 90°±10°; adaptively adjusting the weld overlap for different repair layers, with the bottom layer overlap at 40%~50% and the surface layer overlap at 30%~40%; and automatically generating the welding sequence from high-stiffness areas to low-stiffness areas according to the workpiece structural stiffness distribution. In this embodiment, this step is the core link in achieving precise control of the automated cladding process. First, a non-contact 3D scanner is used to perform a high-precision scan of the workpiece after the preprocessing in step a, acquiring dense 3D point cloud data of its surface, especially the wear areas. This point cloud data is imported into specialized software and precisely geometrically compared with the original computer-aided design (CAD) model of the workpiece. Through 3D deviation analysis, the software automatically generates a digital "defect model" that accurately describes the spatial geometry of the material defect area. Based on this defect model, intelligent planning of the cladding path is performed in the robot's offline programming software. This planning algorithm includes the following innovative features: First, the welding torch posture control system automatically ensures that the angle between the welding torch's axial direction and the normal direction of the local curved surface at the welding point is always constrained within the range of 90°±10° during the welding process. This precise posture control guarantees effective coverage of the molten pool by the shielding gas, regular weld bead formation, and facilitates the uniform distribution of hard phase particles in the molten pool.

[0023] Second, the overlap amount of the weld bead is adaptively adjusted, and different overlap strategies are adopted for different repair layers. The bottom layer weld (usually the initial 1 to 2 layers to fill the bottom of the wear pit) uses a larger overlap amount, ranging from 40% to 50%, to ensure sufficient wetting and filling of the boundary of the defect area and avoid the generation of incomplete fusion defects; the surface layer weld uses a smaller overlap amount, ranging from 30% to 40%, to obtain a smoother weld overlay surface and reduce the amount of subsequent grinding work.

[0024] Third, the welding sequence is optimized. Based on the stiffness distribution of the workpiece structure, the welding sequence from high-stiffness areas to low-stiffness areas is automatically generated. High-stiffness areas have strong resistance to deformation, and welding them first can form a rigid frame; low-stiffness areas are welded later, and their welding stress can be shared by the already welded high-stiffness areas, thereby significantly reducing the overall deformation of the workpiece.

[0025] c. Precise setting of welding parameters and control of heat input: Using a mixed shielding gas of 80% argon (Ar) and 20% carbon dioxide (CO2), set the welding current range to 200~280 amperes (A), the arc voltage range to 26~32 volts (V), and the welding speed range to 300~450 mm / min. Calculate and control the welding heat input (Q) in real time according to the following formula to stabilize it within the target range of 10~20 kJ / cm: In the formula, Q is the welding line energy, in kilojoules per centimeter (kJ / cm); η is the arc thermal efficiency constant determined according to the composition of the shielding gas, with a value of 0.75~0.85; U is the arc voltage, in volts (V); I is the welding current, in amperes (A); and v is the welding speed, in centimeters per minute (cm / min). In this embodiment, key electrical and gas parameters for achieving high-quality weld overlay are set in this step. A mixture of 80% argon (Ar) and 20% carbon dioxide (CO2) by volume is used as the protective medium. This ratio balances arc stability and droplet transfer morphology, resulting in minimal spatter. The shielding gas flow rate is controlled at 18-22 liters per minute (L / min). The welding current range is set to 200-280 amperes (A), the arc voltage range to 26-32 volts (V), and the welding speed range to 300-450 millimeters per minute (mm / min). These parameters are not set in isolation but are synergistically controlled through a core control index: welding heat input (Q). The formula for calculating welding heat input is: In the formula, the meaning and unit of each symbol are specified as follows: Q: Welding line energy, i.e., the heat absorbed per unit length of weld, in kilojoules per centimeter (kJ / cm); η: Arc thermal efficiency constant, which depends on the welding method and shielding gas composition. For the 80%Ar+20%CO2 mixed gas shielded welding used in this invention, the value of η ranges from 0.75 to 0.85; U: Arc voltage, in volts (V); I: Welding current, in amperes (A); v: Welding speed, in centimeters per minute (cm / min).

[0026] This invention achieves stable control of the welding heat input (Q) within the target range of 10-20 kJ / cm by precisely adjusting the three parameters of current, voltage, and speed. This control has crucial metallurgical significance: a heat input below 10 kJ / cm may result in an insufficient molten pool duration, inadequate fluidity of the molten metal, and defects such as incomplete fusion and inclusions; a heat input above 20 kJ / cm will lead to overheating of the molten pool, excessive dissolution of tungsten carbide particles, and an interfacial reaction transition zone thickness exceeding 10 micrometers, causing it to lose its function as an independent hard phase. It will also cause coarse grains and performance degradation in the heat-affected zone of the base material.

[0027] d. Perform welding and dynamic interpass temperature management steps: Use a six-axis industrial robot to perform welding operations, monitor the temperature of the welding area in real time through infrared temperature sensors, and adopt a zoned alternating welding strategy to dynamically control the interpass temperature below 150℃. For thin-walled workpieces with a thickness of less than 20 mm, the interpass temperature is further controlled below 120℃. In this embodiment, after all parameters are set, a six-axis industrial robot precisely and automatically performs the welding operation according to the path planned in step b and the parameters set in step c. During this process, the welding power system provides real-time feedback and records the actual current and voltage values ​​to ensure the process remains stable within the preset window. Simultaneously, a key monitoring and management measure is interpass temperature control. After each pass or layer of welding is completed, a portable infrared thermometer or a fixed thermocouple is used to measure the temperature of the workpiece's welding area and its surroundings. This invention mandates that the interpass temperature be dynamically controlled below 150°C before starting the next layer of welding. For thin-walled areas less than 20 mm thick on the workpiece, due to their small heat capacity and slow heat dissipation, heat accumulation and microstructure coarsening are more likely to occur. Therefore, a stricter interpass temperature control standard is implemented, requiring cooling to below 120°C. Effective control of the interpass temperature limits accumulated heat input, preventing overheating and coarsening of the weld layer microstructure. This is a key process measure for obtaining a fine-grained microstructure, ensuring toughness, and reducing the risk of hot cracking.

[0028] e. Controlled slow cooling and stress release steps: After the welding is completed, the workpiece is placed in a closed space wrapped with insulation material and slowly cooled to room temperature at a cooling rate of no more than 5°C / minute. During the cooling process, the workpiece is subjected to sub-resonant frequency mechanical vibration through a vibration aging device to actively release residual stress.

[0029] In this embodiment, when the entire surfacing process is completed, the workpiece as a whole is still at a relatively high temperature and has significant welding residual stress. If rapid cooling methods such as air cooling or water cooling are used, huge thermal stress will be generated, which is extremely likely to cause cracking of the surfacing layer or the base material. Therefore, the present invention adopts a controllable slow cooling strategy: the workpiece after surfacing is immediately transferred and tightly wrapped with a heat-insulating material (such as aluminosilicate heat-insulating blanket), and placed in a relatively enclosed space, so that it cools uniformly to room temperature at a slow cooling rate not exceeding 5 °C per minute. This slow cooling process allows the residual stress to be fully released and redistributed through microscopic plastic deformation, while avoiding quenching cracks caused by too rapid cooling during the martensitic transformation process. To further actively reduce the residual stress, during the slow cooling process, a mechanical vibration with a sub-resonant frequency can also be applied to the workpiece through a vibration aging device to promote the release of lattice distortion energy and ensure the dimensional stability of the remanufactured component.

[0030] In a specific embodiment, the adaptive adjustment of the bead overlap amount in step b further includes feedback-correcting the offset of the next pass according to the actually scanned bead width, so as to achieve closed-loop control of the surfacing layer thickness.

[0031] In this embodiment, the adaptive adjustment of the bead overlap amount in step b is further limited; in addition to presetting different overlap rates for the bottom layer and the surface layer, this process also introduces a closed-loop control mechanism based on visual feedback; specifically, after the robot completes one weld seam, the actual width of this weld seam can be measured online by using a laser vision sensor integrated with the robot; the control system compares the actually measured bead width with the theoretically planned width, and if there is a deviation, it automatically corrects the movement offset of the robot for the next pass, that is, dynamically adjusts the lateral stepping distance of the welding torch. For example, if the actual bead is wider than expected, the overlap amount for the next pass will be automatically increased to compensate for the overly wide bead and prevent the formation of grooves on the surface; vice versa. Through this closed-loop feedback control, precise control of the surfacing layer thickness and consistency of the surface flatness are achieved.

[0032] In a specific embodiment, the zone-by-zone alternating welding strategy in step d is specifically as follows: the area to be surfaced is divided into a number of sub-blocks with equal areas, and welding is carried out in a "pin" shape or a checkerboard format jump sequence, so that the welding time interval between adjacent sub-blocks is not less than 5 minutes.

[0033] In this embodiment, the partition alternating welding strategy in step d is specifically defined. When the area of the area to be repaired is large, continuous surfacing at one time will cause serious local heat accumulation and workpiece deformation. For this reason, in the path planning stage of the present invention, the entire surfacing area to be welded is divided into a number of sub-blocks with equal areas (for example, divided in a grid pattern); the execution of the welding program does not proceed block by block in sequence, but adopts a "pin" shape or checkerboard format jump sequence. The so-called "pin" shape sequence means taking three adjacent blocks as a group, welding the blocks at the diagonal positions in sequence, and then welding the middle block. The so-called checkerboard format sequence means, like the black and white squares of a chessboard, first welding all the "black square" blocks and then welding all the "white square" blocks. Through this programming strategy, it is forced that the welding start time interval between any two adjacent sub-blocks is not less than 5 minutes. This 5-minute interval provides sufficient heat dissipation time for the welded block, so that its temperature is significantly reduced before being affected by the welding heat of the adjacent area, thereby evenly dispersing the overall heat input in terms of time and space, effectively avoiding excessive peak temperature caused by local heat accumulation, and is a creative process means for suppressing the welding deformation of large and complex workpieces.

[0034] In a specific embodiment, in step a, the transition layer is surfacing with a transition welding wire whose composition is similar to the above composite surfacing material but the carbon content is reduced by 20% - 30%, and the thickness of the transition layer is 2 - 4 millimeters.

[0035] In this embodiment, the transition layer involved in step a is further defined. When it is found through substrate evaluation that the hardness of the base material is low or the local area of the workpiece is too thin due to wear and the strength is insufficient, there is a risk of peeling or collapse when directly surfacing the wear-resistant layer with high hardness and high carbon content. At this time, before surfacing the wear-resistant layer, a transition layer needs to be pre-surfaced. The transition layer is surfacing with a transition welding wire whose composition system is similar to the前述 composite surfacing material but the carbon content is reduced by 20% - 30%. Reducing the carbon content means that the hardness and brittleness of the transition layer are relatively low, while the toughness is significantly improved. The thickness of this transition layer is controlled within 2 - 4 millimeters. This tough transition layer plays multiple roles: First, as a "buffer layer", it absorbs and disperses the stress gradient between the high-hardness wear-resistant layer on the surface and the relatively soft base material, preventing interface cracking; Second, as a "strengthening layer", it provides a support base with moderate strength and hardness for the subsequent surfacing of the wear-resistant layer, avoiding the base material being "collapsed"; Third, its composition is similar to that of the wear-resistant layer, ensuring good metallurgical compatibility and bonding strength.

[0036] This application also provides a wear-resistant weld overlay layer, which is formed by welding the above-mentioned composite weld overlay material according to the above-mentioned automated weld overlay process. The wear-resistant weld overlay layer has a macroscopic Rockwell hardness (HRC) of not less than 60, a Charpy V-notch impact energy (AKU) of not less than 28 joules (J), and in a dry sand rubber wheel wear test under simulated working conditions, the volumetric wear of the wear-resistant weld overlay layer does not exceed one-third of that of the high manganese steel (Mn13) comparative sample.

[0037] In this embodiment, a wear-resistant weld overlay product formed from the aforementioned composite weld overlay material according to the aforementioned automated weld overlay process is defined. This wear-resistant weld overlay possesses excellent performance indicators that can be quantified and verified. Its macroscopic Rockwell hardness (HRC) is not less than 60, a hardness level far exceeding that of conventional high-manganese steel (around HB200, approximately equivalent to below HRC15) and medium-carbon low-alloy steel, effectively resisting the indentation and cutting of abrasive particles. Simultaneously, despite its high hardness, due to its unique microstructure design (tough matrix + multi-scale hard phase), the weld overlay still maintains excellent impact toughness. Its Charpy V-notch impact energy (AKU) is not less than 28 joules (J); this level of toughness is sufficient to withstand the periodic mechanical impact of materials on the liner and blades under stirring conditions, preventing brittle fracture or large-area spalling; more directly, in the dry sand rubber wheel wear test simulating actual working conditions (such as ASTM G65 standard), the volumetric wear of this wear-resistant weld overlay does not exceed one-third of the volumetric wear of the high manganese steel (Mn13) comparative sample under the same test conditions; this relative wear resistance index intuitively and powerfully proves the excellent wear resistance performance of the weld overlay of this invention.

[0038] This application also provides a mixing host liner or blade, the working surface of which has the above-mentioned wear-resistant weld overlay layer.

[0039] This embodiment defines a final product of a mixing host liner or blade; the product is characterized in that its working surface, which is subject to material wear, has a wear-resistant weld overlay as described above; this wear-resistant weld overlay can be a reinforcing layer pre-welded to the easily worn areas of a newly manufactured liner or blade, or it can be a remanufactured layer formed after repair weld overlay on the surface of a worn liner or blade. Regardless of the form, the liner or blade with this wear-resistant weld overlay exhibits a service life and reliability far exceeding that of conventional products.

[0040] This application also provides a method for remanufacturing a mixing host liner or blade, including using the above-mentioned automated overlay welding process to precisely overlay the above-mentioned composite overlay welding material onto the worn working surface of the liner or blade to form a wear-resistant overlay welding layer.

[0041] This embodiment defines a method for remanufacturing a mixing host liner or blades. The core of this method lies in using worn, scrapped liners or blades as blanks and employing an automated welding process to precisely and controllably weld composite welding material onto the working surface of the blank, thereby forming a high-performance wear-resistant weld overlay layer. Through this remanufacturing method, previously unusable consumable parts are given a completely new working surface, even surpassing the performance of new parts, achieving high-value recycling of resources and significantly reducing users' equipment maintenance costs and downtime losses. This method integrates innovation in specialized materials and advanced manufacturing processes, representing the ultimate embodiment of the beneficial effects and industrial value of this invention.

[0042] Example 1 This embodiment provides a high-wear-resistant and impact-resistant composite surfacing material specifically for agitator liner / blades. This material is designed as a metal-cored welding wire, its structure consisting of a low-carbon steel strip encasing a specific ratio of alloy powder. The reason for using a flux-cored welding wire is that the composition of its internal core powder can be flexibly adjusted within a wide range, enabling precise realization of the complex multi-component alloy system designed in this embodiment, which is difficult to achieve with solid welding wire.

[0043] In this embodiment, regarding the chemical composition of the core powder, the carbon (C) content is controlled at 0.8%~1.5% (weight percentage, the same below). Carbon is the basic element for forming carbides, and it also dissolves in the matrix to increase the hardness of martensite. When the content is less than 0.8%, the amount of carbides is insufficient, the matrix hardness is low, and the wear resistance cannot meet the requirements of stirring conditions; when the content is higher than 1.5%, the brittleness of the weld overlay increases sharply, the crack sensitivity increases significantly, and it is prone to spalling or cracking under impact load. The chromium (Cr) content is 5.0%~8.0%. Part of the chromium dissolves in the matrix to improve hardenability, ensuring that the weld overlay obtains a strong and tough structure mainly composed of martensite or bainite, and the other part combines with carbon to form (chromium, iron)7C3 ((Cr, Fe)7C3) type eutectic carbides, which contribute to wear resistance as a secondary hard phase. The molybdenum (Mo) content is 2.0%–4.0%. Molybdenum dissolves in the matrix, playing a significant role in solid solution strengthening and grain refinement. It also improves hardenability and works synergistically with chromium to suppress temper brittleness, making it a key element in ensuring the toughness of the weld overlay. The vanadium (V) content is 1.0%–2.5%. Vanadium is a strong carbide-forming element, precipitating extremely fine vanadium carbides (VC) in situ during weld solidification. These fine-sized, dispersed VCs produce a strong dispersion strengthening effect, significantly improving the microhardness and resistance to temper softening of the matrix. The niobium (Nb) content is 0.5%–1.5%. Niobium preferentially forms niobium carbides (NbC), which tend to precipitate at austenite grain boundaries, effectively pinning grain boundaries and preventing grain growth, thus obtaining a fine solidification structure. Grain refinement strengthening is the only mechanism that can simultaneously improve the strength and toughness of the material. Furthermore, the addition of niobium can significantly reduce the hot cracking susceptibility of the weld metal. Tungsten carbide (WC) particles, as an added hard phase, constitute 20% to 35% of the alloy. These particles possess extremely high intrinsic hardness and are uniformly dispersed within the weld overlay, forming the first line of defense against severe abrasive wear. The remainder consists of iron powder and unavoidable trace impurities; the iron powder forms the basic carrier of the alloy system.

[0044] In this embodiment, the composite welding material forms a unique micro-composite structure after welding, which can be summarized as "tough matrix embedded with multi-scale hard phase". Specifically, this micro-composite structure consists of the following parts: First, a martensitic / bainitic multiphase matrix, which serves as a tough skeleton supporting the hard phase. Its toughness benefits from the composite toughening effect of elements such as molybdenum and chromium, as well as the precise control of subsequent welding processes. Second, in-situ precipitated submicron to micron-sized (Cr,Fe)7C3 type eutectic carbides, which are distributed in a network or strip pattern along the grain boundaries, forming a continuous wear-resistant skeleton. Third, dispersed nano-sized vanadium carbide (VC) and nano-sized niobium carbide (NbC), which are extremely small in size and uniformly dispersed in the matrix, significantly improving the matrix's resistance to plastic deformation and micro-cutting through a second-phase strengthening mechanism. Fourth, incompletely molten micron-sized tungsten carbide (WC) particles, which retain the high hardness and irregular shape of the original particles, serving as the core hard phase to resist macro-abrasive plowing and gouging.

[0045] More importantly, in this embodiment, the interface between the tungsten carbide (WC) particles and the matrix is ​​not a simple mechanical encapsulation, but rather a thin metallurgical reaction transition zone is formed under the heat of welding. The thickness of this metallurgical reaction transition zone is precisely controlled within the range of 2-10 micrometers. This feature is achieved through strict control of the welding heat input: when the heat input is too low, the surface of the tungsten carbide particles does not melt sufficiently, failing to form an effective metallurgical bond, resulting in weak interfacial bonding and easy detachment of the particles during wear; when the heat input is too high, the tungsten carbide particles dissolve excessively. Although the interfacial bonding is enhanced, the hard phase effect of the particles themselves is weakened, and the dissolved tungsten and carbon significantly alter the matrix composition, increasing brittleness. This embodiment, by controlling the thickness of the metallurgical reaction transition zone to 2-10 micrometers, ensures a strong metallurgical bond between the tungsten carbide particles and the matrix while maximizing the preservation of the original high hardness and wear resistance of the tungsten carbide particles. This microstructural feature is one of the core inventive features of this invention and is the fundamental reason for achieving a synergistic improvement in macroscopic high hardness and high toughness of the weld overlay layer.

[0046] Example 2 Based on Example 1, this embodiment further optimizes several technical features of the composite overlay welding material.

[0047] In this embodiment, the particle size of tungsten carbide (WC) particles is preferably 60-200 micrometers. If the particle size is less than 60 micrometers, the risk of complete dissolution in the molten pool increases significantly, making it impossible to effectively retain as an independent hard phase. If the particle size is greater than 200 micrometers, the suspension and uniform distribution of particles in the molten pool become difficult, and the interfacial stress concentration between large particles and the matrix is ​​more severe, making them prone to becoming crack initiation sites under impact loads. Simultaneously, the volume fraction of tungsten carbide particles in the weld overlay is preferably 18%-30%. This volume fraction represents the effective hard phase proportion actually retained in the weld overlay after considering partial burn-off and dissolution during the welding process, based on an addition amount of 20%-35%. Below 18%, the improvement in wear resistance is insufficient; above 30%, the toughness and crack resistance of the weld overlay will significantly decrease.

[0048] In this embodiment, the average size of the nanoscale vanadium carbide (VC) is preferably 50–300 nanometers. This size range is the ideal range for vanadium carbide to exert its best dispersion strengthening effect. By controlling the welding cooling rate (i.e., through interpass temperature management and post-weld slow cooling control), vanadium carbide can be uniformly precipitated at the nanoscale during the solid-state phase transformation after solidification, rather than coarsely precipitated during liquid solidification. Simultaneously, nanoscale niobium carbide (NbC) preferentially precipitates along grain boundaries and forms a pinning effect, resulting in an austenitic grain size finer than ASTM grade 8 in the solidified weld overlay. The average grain diameter corresponding to ASTM grade 8 is approximately 22 micrometers. The grain boundary pinning effect of niobium carbide effectively suppresses grain growth during the welding thermal cycle, and the fine grain structure provides an excellent strength and toughness foundation for the weld overlay.

[0049] In this embodiment, the preferred composition of the core powder is as follows: carbon (C): 1.0%~1.3%, chromium (Cr): 6.0%~7.0%, molybdenum (Mo): 2.5%~3.5%, vanadium (V): 1.5%~2.0%, niobium (Nb): 0.8%~1.2%, and tungsten carbide (WC) particles: 25%~30%. This preferred composition has been verified through extensive testing and can achieve the best balance between wear resistance and impact resistance under conventional stirring host operating conditions.

[0050] Example 3 This embodiment, based on Embodiment 1, further supplements the core powder composition of the composite overlay material.

[0051] In this embodiment, 0.1%–0.5% titanium (Ti) and / or 0.001%–0.005% boron (B) are selectively added to the internal core powder. The addition of titanium plays two main roles: firstly, as a strong deoxidizer, titanium combines with oxygen in the molten pool to form titanium oxide (TiO2), which enters the slag, thereby purifying the weld metal and reducing porosity; secondly, titanium combines with dissolved nitrogen in the molten pool to form high-melting-point titanium nitride (TiN) particles. These particles can act as heterogeneous nucleation sites in the liquid metal, promoting grain refinement. The amount of boron added is extremely small, but its effect is significant: boron atoms tend to agglomerate at austenite grain boundaries, reducing the grain boundary interface energy, thereby significantly inhibiting the initiation and propagation of welding hot cracks (especially solidification cracks and liquefaction cracks). The addition of boron is particularly important for repair scenarios involving thick workpieces or high restraint. Titanium and boron can be added individually or in combination; their synergistic effect can further improve the metallurgical quality and crack resistance of the weld overlay.

[0052] Example 4 This embodiment provides an automated welding process for implementing the composite welding materials described in the foregoing embodiments. The process comprises five core steps, aiming to completely replace traditional manual welding and achieve high precision, high consistency, and high-quality reproducibility in the welding process. A specific repair example is used below to illustrate each step of the process in detail.

[0053] The workpiece is a side lining plate of the main unit of a certain type of concrete mixing plant, made of Hardox450 wear-resistant steel plate with an original thickness of 30mm. After long-term service, the deepest wear in the central area reaches 15mm.

[0054] Step a: Pretreatment and matrix assessment.

[0055] First, a comprehensive non-destructive testing (NDT) is performed on the lining plate to be repaired, using magnetic particle testing to check for micro or macro cracks in the worn area and surrounding region. Any original cracks in the substrate, if not detected and addressed, are highly likely to propagate under the thermal stress of subsequent welding, leading to premature fracture failure of the repaired part in its early service life. After confirming the integrity of the workpiece substrate, the surface is sandblasted to thoroughly remove oxide scale, residual concrete, oil, and other contaminants accumulated during long-term service, until a uniform silver-gray metallic luster is exposed. A clean metal surface is fundamental to ensuring stable arc combustion, good wetting and spreading of the molten metal, and preventing defects such as weld porosity and slag inclusions.

[0056] Furthermore, in the substrate evaluation stage of this embodiment, a portable Leeb hardness tester was used to measure the substrate hardness of the area to be repaired. The measurement showed that the average hardness of the substrate in the wear zone was 420 HB, which meets the preset threshold (≥400 HB) set for Hardox 450 material; therefore, no transition layer is required. If the measurement reveals a significant decrease in substrate hardness, falling below the preset threshold, a transition layer needs to be pre-applied to restore substrate strength.

[0057] Step b: 3D digital reconstruction and adaptive path planning.

[0058] In this embodiment, a handheld blue light 3D scanner is used to perform high-precision scanning of the worn area, obtaining dense 3D point cloud data of its surface. This point cloud data is imported into specialized software and precisely geometrically compared with the original computer-aided design (CAD) model of the lining plate. Through 3D deviation analysis, the software automatically generates a digital "damage model" that accurately describes the spatial geometry of the material defect area.

[0059] Based on this defect model, intelligent planning of the welding path is performed in the robot's offline programming software. This planning includes the following key points: First, welding torch posture control. The system automatically ensures that during the welding process, the angle between the welding torch's axial direction and the normal direction of the local curved surface of the welding point is always constrained within the range of 90°±10°. This precise posture control guarantees effective coverage of the molten pool by the shielding gas, regular weld bead formation, and facilitates the uniform distribution of hard phase particles in the molten pool.

[0060] Second, the overlap amount of the weld bead is adaptively adjusted. Different overlap strategies are adopted for different repair layers. In this embodiment, a total of 8 layers of weld overlay are planned to fill the 15mm wear depth. Among them, the first and second bottom layers use a larger overlap amount of 45% to ensure sufficient wetting and filling of the wear pit boundary and avoid the generation of incomplete fusion defects; the third to eighth surface layers use a smaller overlap amount of 35% to obtain a smoother weld overlay surface and reduce the amount of subsequent grinding work.

[0061] Third, welding sequence optimization. Based on the workpiece's structural stiffness distribution, the welding sequence is automatically generated from high-stiffness areas to low-stiffness areas. This embodiment adopts a spiral advancement strategy from the center of the wear zone to the edge, ensuring that the high-stiffness, unworn areas are heated first, followed by the low-stiffness, worn center areas, thereby evenly releasing welding stress and significantly reducing workpiece deformation.

[0062] Step c: Precise setting of welding parameters and control of line energy.

[0063] In this embodiment, a mixture of 80% argon (Ar) and 20% carbon dioxide (CO2) by volume is used as the protective medium. This ratio balances arc stability and droplet transition morphology, resulting in minimal splashing. The protective gas flow rate is set to 20 liters per minute (L / min).

[0064] Welding parameters are synergistically controlled according to the following line energy formula: In the formula, the meaning and unit of each symbol are specified as follows: Q: Welding line energy, which is the amount of heat absorbed per unit length of weld, is expressed in kilojoules per centimeter (kJ / cm). H: Arc thermal efficiency constant. For the 80%Ar+20%CO2 mixed gas shielded welding used in this embodiment, η is 0.8. U: Arc voltage, measured in volts (V); I: Welding current, in amperes (A); V: Welding speed, measured in centimeters per minute (cm / min).

[0065] In this embodiment, the welding current is set to I=250A, the arc voltage to U=28V, and the welding speed to v=38cm / min (i.e., 380mm / min). Substituting these values ​​into the formula, the linear energy Q=(0.8×28×250) / 38≈14.7kJ / cm is calculated, which stably falls within the target range of 10~20kJ / cm.

[0066] Maintaining the heat line energy within the range of 10–20 kJ / cm is of crucial metallurgical significance: Below 10 kJ / cm, the molten pool may exist for too short a time, resulting in insufficient fluidity of the molten metal and defects such as incomplete fusion and inclusions; above 20 kJ / cm, the molten pool will overheat, leading to excessive dissolution of tungsten carbide particles and an interfacial reaction transition zone thickness exceeding 10 micrometers, thus losing its function as an independent hard phase. Simultaneously, it will cause coarse grains and performance degradation in the heat-affected zone of the base material. This embodiment, through precise control of the heat line energy, ensures that only the surface of the tungsten carbide particles undergoes slight melting, forming a metallurgical reaction transition zone with a thickness of approximately 5–8 micrometers.

[0067] Step d: Perform weld overlay and dynamic interpass temperature management.

[0068] In this embodiment, a six-axis industrial robot equipped with a digital welding machine is used to precisely and automatically perform the welding operation according to the path planned in step b and the parameters set in step c. During the welding process, the welding power system provides real-time feedback and records the actual current and voltage values ​​to ensure that the process remains stable within a preset window.

[0069] Meanwhile, a key monitoring and management measure is interlayer temperature control. After each pass or each layer of welding is completed, a portable infrared thermometer is used to measure the temperature of the workpiece welding area and its surrounding areas. In this embodiment, it is mandatory to dynamically control the interlayer temperature below 150 °C before starting the welding of the next layer. For the thin-walled edge areas on the backing plate with a thickness less than 20 mm, a more stringent interlayer temperature control standard is implemented, that is, it must be cooled below 120 °C. In actual operation, after each layer of welding is completed, wait for the temperature to naturally cool to 110 - 120 °C before starting the welding procedure for the next layer. The effective control of the interlayer temperature limits the cumulative heat input, avoids overheating and coarsening of the surfacing layer structure, and is a key process measure to obtain a fine-grained structure, ensure toughness, and reduce the risk of hot cracks. The entire repair process takes about 45 minutes.

[0070] In this embodiment, when the area of the area to be repaired is large, a zoning and alternating welding strategy is also adopted. Specifically, during the path planning stage, the entire surfacing area to be welded is divided into several sub-blocks with equal areas. The welding procedure is executed in a "pin" shape or checkerboard format jump sequence. The so-called "pin" shape sequence means taking three adjacent blocks as a group, welding the blocks at the diagonal positions in sequence, and then welding the middle block; the so-called checkerboard format sequence means, like the black and white squares of a chessboard, first welding all the "black square" blocks and then welding all the "white square" blocks. Through this programming strategy, it is forced that the start time interval between the welding of any two adjacent sub-blocks is not less than 5 minutes. This 5-minute interval provides sufficient heat dissipation time for the welded blocks, allowing their temperature to significantly decrease before being affected by the welding heat of the adjacent area, thereby evenly dispersing the overall heat input in terms of time and space, and effectively suppressing the welding deformation of large and complex workpieces.

[0071] Step e: Controlled slow cooling and stress release.

[0072] In this embodiment, when the entire surfacing procedure is completed, the workpiece as a whole is still at a relatively high temperature and has a large amount of welding residual stress. If rapid cooling methods such as air cooling or water cooling are used, huge thermal stresses will be generated, which are extremely likely to cause cracking of the surfacing layer or the base material. Therefore, a controlled slow cooling strategy is adopted: immediately wrap the completed backing plate tightly with an aluminum silicate insulation blanket and place it in a corner of the workshop for slow cooling. The measured cooling rate is about 3.5 °C / minute, which is lower than the control upper limit of 5 °C / minute. This slow cooling process allows the residual stress to be fully released and redistributed through microscopic plastic deformation, while avoiding quenching cracks caused by too rapid cooling during the martensitic transformation process.

[0073] To further actively reduce residual stress, during the slow cooling process in this embodiment, a sub-resonant frequency mechanical vibration can be applied to the workpiece using a vibration aging device. This promotes the release of lattice distortion energy and the redistribution of the stress field, ensuring the dimensional stability and service reliability of the remanufactured parts. After cooling to room temperature, the surface of the weld overlay is ground with an angle grinder to remove localized micro-splashes and protrusions, restoring its original smooth contour.

[0074] Process effect inspection The surface of the weld overlay is smooth and even, with uniform weld patterns. Penetrant testing revealed no surface cracks, and ultrasonic testing showed no internal defects such as porosity or slag inclusions. Metallographic analysis showed that the microstructure of the weld overlay consisted of a fine lath martensitic matrix, (chromium, iron) 7-carbon trieutectic carbides distributed along grain boundaries, dispersed nanoscale VC and NbC particles, and a large number of incompletely molten WC particles. A clear metallurgical reaction transition zone with a thickness of approximately 6 micrometers existed between the WC particles and the matrix.

[0075] In terms of mechanical property testing, samples were taken from the excess weld overlay via wire cutting, and the average Rockwell hardness was measured to be 61.5 HRC; the Charpy V-notch impact energy was 28.5 J. In the dry sand rubber wheel wear test (ASTM G65 standard), the volumetric wear of the weld overlay in this embodiment was 28 mm³, while the volumetric wear of the high manganese steel (Mn13) sample under the same conditions was 96 mm³, and the relative wear resistance was 3.4 times that of high manganese steel (i.e., the volumetric wear was approximately 29% of that of high manganese steel).

[0076] In terms of operational testing, the repaired side liner was reinstalled on the original mixing unit, and data was recorded during continuous C30 concrete production. After six months of operation, the wear of the liner was equivalent to that of a brand-new liner after only 2.5 months of use. Considering complete failure, its total service life was 1.8 times that of a brand-new liner. In terms of economic benefits, the cost of a single repair was 35% of the price of a new part; considering the extended lifespan, the annual maintenance cost was reduced by approximately 55%.

[0077] Example 5 Based on Example 4, this embodiment further optimizes the technical solution for adaptively adjusting the weld overlap in the automated surfacing process.

[0078] In this embodiment, in addition to presetting different overlap rates for the bottom and top layers, a closed-loop control mechanism based on visual feedback is introduced. Specifically, after the robot completes a weld, the actual width of the weld is scanned and measured online using a laser vision sensor integrated with the robot. The control system compares the measured actual weld width with the theoretically planned width. If a deviation exists, the robot's movement offset for the next pass is automatically corrected, i.e., the lateral step distance of the welding torch is dynamically adjusted. For example, if the actual weld is wider than expected, the overlap amount for the next pass will automatically increase to compensate for the excessively wide weld and prevent grooves from forming on the surface; conversely, the overlap amount will also increase. Through this closed-loop feedback control, precise control of the weld overlay thickness and consistency of surface flatness are achieved, further improving the quality stability of automated weld overlay.

[0079] Example 6 This embodiment further explains the transition layer technology solution involved in the preprocessing step, based on embodiment 4.

[0080] In this embodiment, when the substrate assessment reveals that the base material has low hardness or that the workpiece is too thin and lacks strength in certain areas due to wear, directly welding a high-hardness, high-carbon-content wear-resistant layer carries the risk of peeling or collapse due to excessive interfacial stress or insufficient support. In this case, a transition layer needs to be pre-welded before welding the wear-resistant layer.

[0081] The transition layer is welded using a transition welding wire with a composition system similar to the aforementioned composite cladding material, but with a carbon content reduced by 20% to 30%. The reduced carbon content means that the transition layer has relatively lower hardness and brittleness, while its toughness is significantly improved. The thickness of the transition layer is controlled at 2 to 4 millimeters.

[0082] This tough transition layer serves multiple functions: First, as a "buffer layer," it absorbs and disperses the stress gradient between the high-hardness wear-resistant surface layer and the relatively soft base material, preventing interface cracking; second, as a "reinforcing layer," it provides a support base with moderate strength and hardness for the subsequent welding of the wear-resistant layer, preventing the base material from being "crushed"; third, its composition is similar to that of the wear-resistant layer, ensuring good metallurgical compatibility and bonding strength.

[0083] Taking the repair of a spiral blade in a mining mixing tank as an example, the workpiece was made of 16Mn, and the blade edge showed localized material fracture and severe thinning. The substrate assessment revealed that the edge area had low hardness. Therefore, before welding the wear-resistant layer, a 3mm thick transition layer was first welded using a transition wire with a 25% lower carbon content (i.e., 0.75% carbon content), followed by the welding of the wear-resistant layer. The repaired blade operated in the slurry mixing tank for 9 months, achieving a lifespan 2.0 times that of a new blade, without any further breakage or peeling.

[0084] Example 7 This embodiment provides a wear-resistant weld overlay product formed from the composite weld overlay material described in the foregoing embodiments according to the automated weld overlay process described in the foregoing embodiments.

[0085] In this embodiment, the wear-resistant weld overlay exhibits excellent performance indicators that can be quantified and verified. Its macroscopic Rockwell hardness (HRC) is not less than 60, a level far exceeding that of conventional high-manganese steel (around HB200, roughly equivalent to below HRC15) and medium-carbon low-alloy steel, effectively resisting the indentation and cutting of abrasive particles. Simultaneously, despite its high hardness, due to its unique microstructure design (tough matrix + multi-scale hard phase), the weld overlay maintains excellent impact toughness, with a Charpy V-notch impact energy (AKU) of not less than 28 joules (J). This level of toughness is sufficient to withstand the periodic mechanical impacts of materials on the liner and blades under stirring conditions, preventing brittle fracture or large-area spalling.

[0086] More directly, in dry sand rubber wheel wear tests simulating actual working conditions (such as ASTM G65 standard), the volumetric wear exhibited by this wear-resistant weld overlay does not exceed one-third of the volumetric wear of the high-manganese steel (Mn13) comparative specimen under the same test conditions. This relative wear resistance index intuitively and powerfully demonstrates the superior wear resistance of the weld overlay in this embodiment.

[0087] Example 8 This embodiment provides a final product: a liner or blade for a mixing host.

[0088] In this embodiment, the liner or blade is characterized in that its working surface, which is subject to material wear, has a wear-resistant weld overlay as described in Embodiment 7. This wear-resistant weld overlay can be a reinforcing layer pre-welded to the wear-prone areas of a newly manufactured liner or blade, or it can be a remanufactured layer formed after repair weld overlay on the surface of a worn liner or blade. Regardless of the form, the liner or blade with this wear-resistant weld overlay exhibits a service life and reliability far exceeding that of conventional products.

[0089] Example 9 This embodiment provides a method for remanufacturing the liner or blades of a mixing host.

[0090] In this embodiment, the core of the remanufacturing method is to use worn waste liners or blades as blanks, and to use the automated overlay welding process described in any one of Embodiments 4 to 6 to precisely and controllably overlay the composite overlay welding material described in any one of Embodiments 1 to 3 onto the working surface of the blank, thereby forming the high-performance wear-resistant overlay welding layer described in Embodiment 7.

[0091] This remanufacturing method endows previously unusable consumable parts with entirely new working surfaces, even surpassing the performance of new parts, achieving high-value recycling of resources and significantly reducing users' equipment maintenance costs and downtime losses. This method integrates innovation in specialized materials and advanced manufacturing processes, representing the ultimate embodiment of the beneficial effects and industrial value of this technical solution.

[0092] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0093] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A high wear-resistant and impact-resistant composite overlay welding material for mixing host liner / blades, characterized in that, The welding material is a metal powder-cored flux-cored wire, with an outer sheath of low-carbon steel strip. The chemical composition of the inner core powder, by weight percentage, includes: carbon (C): 0.8%~1.5%, chromium (Cr): 5.0%~8.0%, molybdenum (Mo): 2.0%~4.0%, vanadium (V): 1.0%~2.5%, niobium (Nb): 0.5%~1.5%, tungsten carbide (WC) particles: 20%~35%, and the balance being iron powder. The composite surfacing material forms a micro-composite structure of a tough matrix inlaid with multi-scale hard phases after surfacing. The micro-composite structure is composed of a martensitic / bainitic multiphase matrix, submicron to micron-sized (Cr,Fe)7C3 type eutectic carbides precipitated in situ, dispersed nano-sized vanadium carbides (VC) and nano-sized niobium carbides (NbC), and incompletely molten micron-sized tungsten carbide (WC) particles. The tungsten carbide (WC) particles form a thin metallurgical reaction transition zone at the interface with the matrix, and the thickness of the metallurgical reaction transition zone is 2 to 10 microns.

2. The composite surfacing material according to claim 1, characterized in that, The tungsten carbide (WC) particles have a particle size of 60-200 micrometers and a volume fraction of 18%-30% in the weld overlay; the nano-sized vanadium carbide (VC) has an average size of 50-300 nanometers, and the nano-sized niobium carbide (NbC) preferentially precipitates along grain boundaries and forms a pinning effect, making the austenite grain size of the solidified structure of the weld overlay finer than ASTM grade 8.

3. The composite surfacing material according to claim 1, characterized in that, The internal core powder also contains 0.1% to 0.5% titanium (Ti) and / or 0.001% to 0.005% boron (B), wherein the titanium (Ti) is used for deoxidation and to form titanium nitride (TiN) particles to further refine the grains, and the boron (B) is used to segregate at the grain boundaries to improve the thermal cracking resistance of the weld overlay.

4. An automated welding process for implementing the composite welding material according to any one of claims 1 to 3, characterized in that, Includes the following steps: a. Pretreatment and substrate assessment steps: After non-destructive testing of the workpiece to be repaired to confirm that there are no deep cracks, sandblasting is performed to remove surface contaminants; The hardness of the substrate in the area to be repaired is measured by a portable hardness tester. When the hardness of the substrate is lower than a preset threshold, a transition layer is pre-welded to restore the strength of the substrate. b. Steps for 3D digital reconstruction and adaptive path planning: Use a 3D scanner to acquire point cloud data of the workpiece surface, compare it with the original CAD model to generate a "damaged model"; Based on the aforementioned defect model, a multi-layer, multi-pass welding path is automatically calculated and generated in the robot offline programming software. The path planning algorithm includes: automatically constraining the angle between the welding torch axis and the local curved surface normal of the welding point within the range of 90°±10°; adaptively adjusting the weld overlap amount for different repair layers, with the bottom layer overlap amount being 40%~50% and the surface layer overlap amount being 30%~40%; and automatically generating the welding sequence from high stiffness region to low stiffness region according to the workpiece structural stiffness distribution. c. Precise setting of welding parameters and control steps of line energy: Use a mixed shielding gas of 80% argon (Ar) and 20% carbon dioxide (CO2). Set the welding current range to 200 - 280 amperes (A), the arc voltage range to 26 - 32 volts (V), and the welding speed range to 300 - 450 millimeters per minute (mm / min). Calculate and control the welding line energy (Q) in real time according to the following formula to stabilize it within the target range of 10 - 20 kilojoules per centimeter (kJ / cm): ； In the formula, Q is the welding line energy, with the unit of kilojoules per centimeter (kJ / cm); η is the arc thermal efficiency constant determined according to the composition of the shielding gas, and its value is 0.75 - 0.85; U is the arc voltage, with the unit of volts (V); I is the welding current, with the unit of amperes (A); v is the welding speed, with the unit of centimeters per minute (cm / min); d. Execution of surfacing welding and dynamic interlayer temperature management steps: Use a six-axis industrial robot to perform surfacing welding operations. Real-time monitor the temperature of the welding area through an infrared temperature sensor, and adopt a zoning and alternating welding strategy to dynamically control the interlayer temperature below 150°C. For the thin-walled workpiece area with a thickness less than 20 millimeters, the interlayer temperature is further controlled below 120°C; e. Controllable slow cooling and stress release steps: After surfacing welding is completed, place the workpiece in a closed space wrapped with heat-insulating materials and slowly cool it to room temperature at a cooling rate not greater than 5°C / minute. During the cooling process, apply mechanical vibration with a sub-resonant frequency to the workpiece through a vibration aging device to actively release the residual stress.

5. The automated welding process according to claim 4, characterized in that, The adaptive adjustment of the bead overlap amount in step b also includes feedback correction of the offset of the next pass according to the actual bead width obtained by scanning, to achieve closed-loop control of the surfacing layer thickness.

6. The automated welding process according to claim 4, characterized in that, The zoning and alternating welding strategy in step d is specifically: Divide the area to be surfaced into several sub-blocks with equal areas, and perform welding in a "pin" shape or checkerboard pattern jump sequence, so that the welding time interval between adjacent sub-blocks is not less than 5 minutes.

7. The automated welding process according to claim 4, characterized in that, In step a, the transition layer is surfaced using a transition welding wire with a composition similar to the composite surfacing material described in any one of claims 1 to 3 but with a carbon content reduced by 20% - 30%. The thickness of the transition layer is 2 - 4 millimeters.

8. A wear-resistant weld overlay, characterized in that, The wear-resistant surfacing layer is formed by surfacing the composite surfacing material described in any one of claims 1 to 3 according to the automated surfacing process described in any one of claims 4 to 7. The macro Rockwell hardness (HRC) of the wear-resistant surfacing layer is not less than 60, the Charpy V-notch impact energy (AKU) is not less than 28 joules (J), and in the dry sand rubber wheel wear test under simulated working conditions, the volume wear amount of the wear-resistant surfacing layer does not exceed one-third of the comparison specimen of high manganese steel (Mn13).

9. A mixing host liner or blade, characterized in that, The working surface of the lining plate or blade has a wear-resistant surfacing layer as described in claim 8.

10. A method for remanufacturing a mixing host liner or blades, characterized in that, It includes using the automated surfacing process described in any one of claims 4 to 7 to precisely surface the composite surfacing material described in any one of claims 1 to 3 on the worn working surface of the lining plate or blade, to form the wear-resistant surfacing layer described in claim 8.

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