Gradient functionalized high-toughness shear blade material based on double-laser melting forging time sequence coupling and preparation method of gradient functionalized high-toughness shear blade material

Abstract

The invention belongs to the technical field of metallurgical equipment remanufacturing, and particularly relates to a gradient functionalized high-toughness shear blade material based on double-laser melting forging time sequence coupling and a preparation method thereof. The gradient functionalized high-toughness shear blade material is prepared from the following components in percentage by mass: 0.6 percent to 0.7 percent of C, 4.5 percent to 5.5 percent of Cr, 1.8 percent to 2.2 percent of W, 1.2 percent to 1.5 percent of Mo, 0.8 percent to 1.0 percent of V, 2.8 percent to 3.2 percent of Ti, 0.008 percent to 0.015 percent of B, 0.02 percent to 0.05 percent of Ce and the balance of Fe and inevitable impurity elements. Through a three-in-one coordinated regulation and control system of gradient material design, double-laser time sequence coupling and in-situ interface strengthening, the technical bottleneck that the hardness and the toughness of a shear blade material cannot be obtained at the same time is broken through, and the problems of tipping failure, insufficient fatigue life and the like of a traditional disc shear blade material during service are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of remanufacturing of metallurgical equipment, and particularly relates to a gradient-functionalized high-strength and high-toughness shear blade material based on the time-sequence coupling of double laser forging and a preparation method thereof. Background Art

[0002] As the core equipment for sheet finishing processing, the service performance of the disc shear blade directly determines the quality grade of the strip steel shearing surface and the continuous operation efficiency of the production line. At present, the disc shear blades commonly used in the industry are made of LD cold work die steel (7Cr7Mo2V2Si) by traditional forging processes. In practical applications, key technical defects have emerged. Due to the low strength and toughness of the original LD material, for example, when the hardness of LD steel reaches ≥62HRC, the impact toughness drops sharply to <15 J / cm², and it is extremely easy to cause edge chipping failure due to impact loads during actual service, greatly affecting the service life and working stability of the shear blade. Especially when shearing silicon steel, it can only shear 2 - 5 coils of products before it needs to be taken offline, seriously affecting the continuous production operation rate. After taking it offline and conducting a failure analysis, a large number of edge chips are found at the blade edge. This form of chipping failure will cause "dog tooth" shaped defects in the edge quality, resulting in product downgrading and a great waste of production costs. Therefore, determining a special high-strength and high-toughness shear blade material suitable for disc shears is an important problem that needs to be solved at present.

[0003] Disc shears are usually prepared by forging. This process method cannot effectively overcome the problem of carbide segregation. The carbide segregation grade is usually ≥3, resulting in non-uniform internal properties of the material and further weakening the overall performance of the material. In addition, the current repair method for disc shears is usually to use a grinding machine to re-grind the blade edge after taking it offline, and then put it back on the machine after the blade edge is precisely ground to meet the drawing standards. However, the material purity of the original material and the fatigue situation after being put into service are not considered. Therefore, the service life of the disc shears put back on the machine after repair is usually shorter, and it has a greater impact on product quality, resulting in a vicious cycle.

[0004] Therefore, whether considering manufacturing or remanufacturing repair, disc shear products need to develop a new material and preparation method to achieve a longer service life by improving the comprehensive performance of the disc shear material.

[0005] The laser forging process method is different from the traditional laser cladding technology and surface strengthening technology fields. Although laser cladding can achieve metallurgical bonding on the material surface and the construction of a functional layer, problems such as residual stress concentration and insufficient density are prone to occur during the rapid solidification process of the cladding layer. Moreover, conventional post-treatment processes often require an independent impact strengthening process to be set up, and there are still various limitations.

[0006] In summary, it is of great practical significance and urgency to develop a high-strength and tough shear blade material with gradient functionality that can break through the above material and process technology bottlenecks and its adapted preparation method. Summary of the Invention

[0007] In view of the above technical problems existing in the forged LD material used in traditional circular shear products, the present invention provides a gradient-functionalized high-strength and tough shear blade material based on the sequential coupling of dual-laser forging and its preparation method. The present invention designs a high-strength and high-toughness material for cutting tools, and combines a specific "dual-laser" sequential coupling forging technology to prepare a high-strength and high-toughness strengthening coating on the service surface of the circular shear, thereby improving the wear resistance and impact resistance of the circular shear and further enhancing the service life of the circular shear. Through a trinity collaborative regulation system of "gradient material design - dual-laser sequential coupling - in-situ interface strengthening", the technical bottleneck that hardness and toughness cannot be achieved simultaneously in the shear blade material is broken through, and problems such as edge chipping failure and insufficient fatigue life existing in the traditional circular shear blade material during service are solved.

[0008] To achieve the above object, the present invention adopts the following technical solutions.

[0009] A gradient-functionalized high-strength and tough shear blade material based on the sequential coupling of dual-laser forging, comprising the following components in mass percentage: C: 0.6% - 0.7%, Cr: 4.5% - 5.5%, W: 1.8% - 2.2%, Mo: 1.2% - 1.5%, V: 0.8% - 1.0%, Ti: 2.8% - 3.2%, B: 0.008% - 0.015%, Ce: 0.02% - 0.05%, and the balance is Fe and unavoidable impurity elements.

[0010] A preparation method for a gradient-functionalized high-strength and tough shear blade based on the sequential coupling of dual-laser forging, comprising the following steps: Step 1, pre-placement continuous laser cladding: perform continuous laser cladding on the shear blade, and keep the energy density in the cladding area at 200 J / mm² - 300 J / mm²; Step 2, post-placement pulsed laser forging: perform pulsed laser forging on the shear blade after continuous laser cladding in Step 1, and the interval time between pulsed laser forging and continuous laser cladding is ≤50 ms, and the energy density in the forging area is 80 J / mm² - 120 J / mm²; a gradient-functionalized high-strength and tough shear blade based on the sequential coupling of dual-laser forging is obtained.

[0011] Further, in Step 1, the laser cladding parameters are: the laser power is set at 2.5 kW - 3.5 kW, the scanning speed is 8 mm / s - 12 mm / s, the spot diameter is 3 mm - 4 mm, the overlapping rate is between 30% - 40%, and the thickness of the cladding layer is 1.5 - 2.5 mm.

[0012] Further, in step 2, the parameters of pulsed laser forging are as follows: the peak power of pulsed laser is 4kW - 6kW, the frequency is 20Hz - 30Hz, the pulse width is 5ms - 10ms, the scanning speed is 5mm / s - 8mm / s, and the scanning path is arranged at a 45° intersection with the cladding layer.

[0013] The working mechanism of the present invention: 1. Ultra-fast cooling solid solution and precipitation strengthening synergistic mechanism: In the present invention, residual carbides are removed from the quenched structure of high-strength steel components to improve the toughness of the material while ensuring the strength of the material; it breaks through the core bottleneck in the traditional process of adding Ti element - the high activity of Ti element leads to difficulties in traditional process control and the risk of precipitation of brittle phases. However, the advantages of grain refinement, high-temperature strengthening, and wear resistance improvement brought by it are significantly undeniable. Innovatively, laser ultra-fast solidification is used to inhibit the precipitation of TiC. During the ultra-fast cooling process of continuous laser cladding, the diffusion of Ti atoms is greatly hindered and it is difficult to combine with C atoms to form TiC. Thus, a large amount of Ti is dissolved in the BCC matrix to form a supersaturated solid solution, resulting in a significant solid solution strengthening effect, and the solid solution strengthening increment ≥ 200 Mpa; the solid solubility of Ti element in the matrix is increased from the solid solubility ≤ 1.5% in the traditional process to the solid solubility of 3.0 - 3.2% in the melting forging process. When post-pulsed laser forging is carried out, although the cooling rate decreases, appropriate thermal cycle conditions induce the precipitation of nano-sized TiC particles with a size < 20nm from Ti atoms and C atoms in the supersaturated solid solution at appropriate positions, realizing "solid solution + precipitation" composite strengthening, and making the material properties show gradient functionality, thereby further improving the strength and toughness.

[0014] 2. Dynamic recrystallization grain refinement mechanism: During the pulsed laser forging process, the material undergoes a thermal cycle with instant high temperature and extremely short holding time. This special thermal condition stimulates the material to undergo ultra-fine grain dynamic recrystallization, forming a fine grain structure with a grain size of 2 - 5μm. The segregation effect of B element at the grain boundary effectively inhibits the grain boundary migration and prevents abnormal grain growth; Ce element reduces the inclusions in the molten pool and provides good nucleation conditions for recrystallization. The synergistic effect of the two realizes the refinement of grains, and the grain boundary strengthening increment ≥ 150 MPa.

[0015] 3. Gradient function construction and optimization mechanism: Due to the rapid solidification and thermal shrinkage effects, the surface layer formed by continuous laser cladding generates a relatively high residual compressive stress, which effectively inhibits the initiation and propagation of cracks. Post-pulsed laser forging forms a reasonable gradient distribution from the surface residual compressive stress to the matrix tensile stress inside the material by precisely controlling the process parameters. At the same time, pulsed laser introduces high-density dislocations, and the dislocations interact with each other inside the material to form dislocation walls, further forming an equiaxed grain gradient level distribution with gradient differentiation. The combined action of the two strengthens the material, enabling the material to have a high-hardness edge while the matrix maintains good toughness and anti-deformation ability, meeting the mechanical property requirements of the shear blade at different service stages.

[0016] Compared with the prior art, the technical effects of the present invention are as follows.

[0017] (1) Due to the extremely high cooling rate (up to 10 4 -10 5 ℃ / s) in the pre - continuous laser cladding process, the precipitation of TiC is effectively inhibited, enabling Ti atoms to be fully dissolved in the matrix, forming a surface layer region with ultra - high hardness, hardness ≥ 65HRC, meeting the high - hardness requirement of the cutting edge.

[0018] (2) The instantaneous high temperature and high pressure generated by the pulsed laser stimulate the dynamic recrystallization process inside the material, resulting in a recrystallization rate of the material ≥ 90%, forming a uniform and fine grain structure, significantly improving the toughness of the material. At the same time, a reasonable stress gradient is constructed inside the material. The residual compressive stress is ≥ 500MPa on the surface layer, gradually transitioning to a tensile stress ≤ 100MPa towards the matrix, and the stress relaxation rate < 15%, effectively improving the fatigue resistance and service stability of the material.

[0019] (3) The interval time between continuous laser cladding and pulsed laser forging is strictly controlled within ≤ 50ms, which can utilize the residual heat of the cladding layer to ensure good metallurgical bonding between the cladding layer and the matrix, and the bonding strength ≥ 800MPa.

[0020] (4) By precisely regulating the laser energy density, the energy density in the cladding area is maintained at 200J / mm 2 -300J / mm 2 , and the energy density in the forging area is 80J / mm 2 -120J / mm 2 , forming a hardness gradient (65HRC → 58HRC) and a toughness gradient (KIC: 50 Mpa·m 1 / 2 →85Mpa·m 1 / 2 ) from the cutting - edge surface layer to the matrix, enabling the material properties to be optimally matched in different regions, meeting the requirements of the complex service conditions of the shear blade. Detailed implementation manners

[0021] The technical solutions in the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without any creative work belong to the scope of protection of the present invention.

[0022] A gradient-functionalized high-strength and high-toughness shear blade material based on the time-sequence coupling of dual-laser melting and forging, comprising the following components by mass percentage: C: 0.6% - 0.7%, Cr: 4.5% - 5.5%, W: 1.8% - 2.2%, Mo: 1.2% - 1.5%, V: 0.8% - 1.0%, Ti: 2.8% - 3.2%, B: 0.008% - 0.015%, Ce: 0.02% - 0.05%, and the balance being Fe and inevitable impurity elements.

[0023] A preparation method of a gradient-functionalized high-strength and high-toughness shear blade based on the time-sequence coupling of dual-laser melting and forging, comprising the following steps: Step 1, pre-positioned continuous laser cladding: Continuously laser-clad the shear blade, and keep the energy density in the cladding area at 200 J / mm 2 -300 J / mm 2 ; The laser cladding parameters are: the laser power is set at 2.5 kW - 3.5 kW, the scanning speed is 8 mm / s - 12 mm / s, the spot diameter is 3 mm - 4 mm, the overlapping rate is between 30% - 40%, and the thickness of the cladding layer is 1.5 - 2.5 mm; Step 2, post-positioned pulsed laser forging: Pulse-laser-forge the shear blade after continuous laser cladding in Step 1. The interval time between pulsed laser forging and continuous laser cladding is ≤50 ms, and the energy density in the forging area is 80 J / mm 2 -120 J / mm 2 ; The pulsed laser forging parameters are: the peak power of the pulsed laser is 4 kW - 6 kW, the frequency is 20 Hz - 30 Hz, the pulse width is 5 ms - 10 ms, the scanning speed is 5 mm / s - 8 mm / s, and the scanning path intersects with the cladding layer at 45°; thus obtaining a gradient-functionalized high-strength and high-toughness shear blade based on the time-sequence coupling of dual-laser melting and forging.

[0024] Example 1.

[0025] A gradient-functionalized high-strength and high-toughness shear blade material: Composed of the following components by mass percentage, C: 0.65%, Cr: 5.0%, W: 2.0%, Mo: 1.3%, V: 0.9%, Ti: 3.0%, B: 0.012%, Ce: 0.03%, and the balance being Fe.

[0026] A preparation method of a gradient-functionalized high-strength and high-toughness shear blade based on the time-sequence coupling of dual-laser melting and forging, comprising the following steps: Step 1, pre-positioned continuous laser cladding: Continuously laser-clad the shear blade, set the laser power at 3.0 kW, the scanning speed at 10 mm / s, the spot diameter at 3.5 mm, the overlapping rate at 35%, and perform cladding at the edge of the shear blade blank to form a cladding layer with a thickness of 2.0 mm. The energy density in the cladding area is 280 J / mm2 The cooling rate is measured to be approximately 8×10 4 ℃ / s; Step 2, post - pulse laser forging: Conduct pulse laser forging 40 ms after the completion of continuous laser cladding in Step 1. Start the pulse laser forging, set the peak power of the pulse laser to 5.0 kW, the frequency to 25 Hz, the pulse width to 8 ms, the scanning speed to 6 mm / s, and the scanning path intersects the cladding layer at 45°. The energy density in the forging area is 90 J / mm 2 to obtain a gradient - functionalized high - strength and tough shear blade based on the time - sequence coupling of dual - laser melting and forging.

[0027] Performance testing: 1. Hardness testing: Use a Rockwell hardness tester to test the surface layer of the blade edge, and the hardness reaches 66.2 HRC; test at different positions in the transition zone and the substrate, and the hardness shows a gradient change that gradually decreases from the blade edge to the substrate. The hardness in the transition zone is about 60 HRC, and the hardness of the substrate is 58 HRC.

[0028] 2. Impact toughness testing: Use an impact testing machine to test the impact toughness. Conduct impact toughness testing in the cladding area of the blade edge, and the result is 18 J / cm 2 ; conduct impact toughness testing in the transition zone, and the result is 22 J / cm 2 ; conduct impact toughness testing in the substrate area, and the result is 28 J / cm 2 ; Based on the above test results, realize the gradient design of impact toughness.

[0029] 3. Fracture toughness testing: Conduct fracture toughness testing on the cladding area of the blade edge, and the KIC value reaches 55 MPa・m 1 / 2 ; conduct fracture toughness testing on the transition zone, and the KIC value reaches 72.5 MPa・m 1 / 2 ; conduct fracture toughness testing on the substrate area, and the KIC value reaches 82 MPa・m 1 / 2 . It is possible to achieve a fracture toughness gradient design of 50 Mpa·m 1 / 2 →85Mpa·m 1 / 2 .

[0030] 4. Residual stress testing: The residual compressive stress is 500 MPa on the surface layer, gradually transitioning to a tensile stress of 90 MPa towards the substrate, and the stress relaxation rate is 10%, realizing the construction of a reasonable stress gradient inside the material.

[0031] 5. Bonding strength testing: Conduct strength testing on the bonding strength of the substrate, and the result of the bonding strength is 820 MPa, ensuring good metallurgical bonding between the cladding layer and the substrate.

[0032] 6. Microstructure examination: Through metallographic microscopy and scanning electron microscopy, the initial grain size of the material is about 6 μm, the carbide segregation grade is ≤1 level, and the porosity is detected to be 0.2%.

[0033] 7. Service life test: The prepared shear blade is installed on a circular shear equipment for actual service test. Compared with the traditional LD steel shear blade, the service life is increased by 3.2 times.

[0034] Example 2.

[0035] A gradient-functionalized high-strength and high-toughness shear blade material based on the time-sequence coupling of dual-laser melting and forging: It is composed of the following components by mass percentage: C: 0.63%, Cr: 4.8%, W: 1.9%, Mo: 1.4%, V: 0.85%, Ti: 2.9%, B: 0.01%, Ce: 0.04%, and the balance is Fe.

[0036] A preparation method of a gradient-functionalized high-strength and high-toughness shear blade based on the time-sequence coupling of dual-laser melting and forging, comprising the following steps: Step 1. Preceding continuous laser cladding: Continuously laser-clad the shear blade. Set the laser power to 2.8 kW, the scanning speed to 11 mm / s, the spot diameter to 3.2 mm, and the overlapping rate to 32%. Clad the edge part of the shear blade blank to form a clad layer with a thickness of 1.5 mm. The energy density of the clad area is 220 J / mm², and the cooling rate is calculated to be about 7.8×10 4 ℃ / s Step 2. Subsequent pulsed laser forging: Perform pulsed laser forging 35 ms after the completion of the continuous laser cladding in Step 1. Start the pulsed laser forging, set the peak power of the pulsed laser to 4.5 kW, the frequency to 22 Hz, the pulse width to 7 ms, the scanning speed to 7 mm / s, and the scanning path to intersect with the clad layer at 45°. The energy density of the forging area is 112 J / mm², and a gradient-functionalized high-strength and high-toughness shear blade based on the time-sequence coupling of dual-laser melting and forging is obtained.

[0037] Performance test: 1. Hardness test: Use a Rockwell hardness tester to test the surface layer of the edge, and the hardness reaches 65.4 HRC; test at different positions in the transition zone and the matrix, and the hardness shows a gradient change gradually decreasing from the edge to the matrix. The hardness in the transition zone is about 59.8 HRC, and the hardness of the matrix is 57 HRC.

[0038] 2. Impact toughness test: Use an impact testing machine to test the impact toughness. Conduct the impact toughness test in the clad area of the edge, and the result is 17.5 J / cm 2 ; conduct the impact toughness test in the transition zone, and the result is 24 J / cm 2 ; conduct the impact toughness test in the matrix area, and the result is 27.2 J / cm 2; Based on the above test results, achieve the design of impact toughness gradient.

[0039] 3. Fracture toughness test: Conduct a fracture toughness test on the clad area of the blade edge. The KIC value reaches 57 MPa·m 1 / 2 , conduct a fracture toughness test on the transition zone. The KIC value reaches 76 MPa·m 1 / 2 , conduct a fracture toughness test on the substrate area. The KIC value reaches 85 MPa·m 1 / 2 . It is possible to achieve a toughness gradient design of 50 Mpa·m¹ / ² → 85 Mpa·m 1 / 2 .

[0040] 4. Residual stress test: The residual compressive stress is 516 MPa on the surface layer, gradually transitioning to a tensile stress of 95 MPa towards the substrate, and the stress relaxation rate is 11%. A reasonable stress gradient is built inside the material.

[0041] 5. Bonding strength test: Conduct a strength test on the bonding strength of the substrate. The result shows that the bonding strength is 825 MPa, ensuring good metallurgical bonding between the clad layer and the substrate.

[0042] 6. The internal metallographic structure of the material is uniform, the initial grain size is about 7 μm, the carbide segregation grade is ≤ 1 level, and the porosity is 0.25%.

[0043] 7. In the service test of the disk shear blade, the service life is increased by 2.8 times compared with the traditional LD steel shear blade.

[0044] Comparative Example 1.

[0045] A preparation method of a gradient-functionalized high-strength and tough shear blade based on the time-sequence coupling of double laser melting and forging, whose component composition is exactly the same as that of Example 1, specifically: C: 0.65%, Cr: 5.0%, W: 2.0%, Mo: 1.3%, V: 0.9%, Ti: 3.0%, B: 0.012%, Ce: 0.03%, and the balance is Fe.

[0046] The preparation method includes the following steps: Step 1. Preceding continuous laser cladding: Consistent with the parameters of Example 1, conduct continuous laser cladding on the shear blade. Set the laser power to 3.0 kW, the scanning speed to 10 mm / s, the spot diameter to 3.5 mm, and the overlapping rate to 35%. A clad layer with a thickness of 2.0 mm is formed at the blade edge part of the shear blade blank, and the energy density of the clad area is 280 J / mm 2 , and the cooling rate is estimated to be about 8×10 4 ℃ / s.

[0047] Step 2, Post - pulse laser forging: 60 ms after the completion of continuous laser cladding in Step 1 (compared with 40 ms in Comparative Example 1), start pulse laser forging. Set the peak power of the pulse laser to 5.0 kW, the frequency to 25 Hz, the pulse width to 8 ms, the scanning speed to 6 mm / s, the scanning path intersects with the cladding layer at 45°, and the energy density in the forging area is 90 J / mm 2 , and finally obtain the shear blade material.

[0048] Performance test and comparative analysis: Bonding strength test: Use a universal material testing machine (ASTM E8 standard) to test the bonding strength between the cladding layer and the substrate.

[0049] Example 1: The bonding strength is 820 MPa, and the fracture position is in the substrate area, indicating good bonding between the cladding layer and the substrate.

[0050] Comparative Example 1: The bonding strength is only 650 MPa, and the fracture interface is at the junction of the cladding layer and the substrate, showing brittle fracture characteristics.

[0051] Metallographic structure analysis Example 1: A continuous gradient transition structure is formed at the interface between the cladding layer and the substrate, with fine and uniform grains (average grain size ≤ 5 μm), and no unfused defects are found.

[0052] Comparative Example 1: There is a local unfused area (width about 10 - 15 μm) at the interface, obvious grain coarsening (average grain size ≥ 20 μm), and accompanied by microcracks (length about 50 - 100 μm).

[0053] Residual stress test Example 1: The residual compressive stress at the interface is - 350 MPa, effectively inhibiting crack initiation.

[0054] Comparative Example 1: The residual tensile stress at the interface is + 200 MPa, increasing the risk of crack propagation.

[0055] Comparative Example 2.

[0056] A preparation method of a gradient - functionalized high - strength and tough shear blade based on the time - sequence coupling of double - laser melting and forging, whose component composition is exactly the same as that of Example 1, specifically: C: 0.65%, Cr: 5.0%, W: 2.0%, Mo: 1.3%, V: 0.9%, Ti: 3.0%, B: 0.012%, Ce: 0.03%, and the balance is Fe.

[0057] The preparation method includes the following steps: Step 1. Preceding continuous laser cladding: Perform continuous laser cladding on the shear blade, adjust the laser power to 1.2 kW (3.0 kW in the original Example 1), the scanning speed to 10 mm / s, the spot diameter to 3.5 mm, and the overlapping rate to 35%. A cladding layer with a thickness of 2.0 mm is formed at the edge part, and the energy density in the cladding area is reduced to 100 J / mm 2 (compared with 280 J / mm in Comparative Example 1 2 ), and the cooling rate is measured to be approximately 5×10 3 ℃ / s (significantly reduced).

[0058] Step 2. Subsequent pulsed laser forging: Start pulsed laser forging 40 ms after Step 1 is completed (the interval time is the same as that in Example 1), adjust the peak power of the pulsed laser to 8.0 kW (5.0 kW in the original Example 1), the frequency to 25 Hz, the pulse width to 8 ms, and the scanning speed to 6 mm / s. The energy density in the forging area is increased to 150 J / mm 2 (compared with 90 J / mm in Comparative Example 1 2 ), and the scanning path still intersects with the cladding layer at 45°.

[0059] Performance test and comparative analysis: Hardness gradient test Example 1: The surface hardness of the edge is 65 HRC, and it gradually decreases to 58 HRC in the direction of the substrate (the gradient difference is 7 HRC), meeting the requirements of the shearing working condition for high surface hardness and high substrate toughness.

[0060] Comparative Example 2: The surface hardness is only 52 HRC, the substrate hardness is 50 HRC (the gradient difference is 2 HRC), and the hardness distribution fluctuates greatly (±3 HRC), unable to form an effective gradient.

[0061] Fracture toughness (KIC) test Example 1: The KIC of the edge surface is 50 MPa·m 1 / 2 , and the substrate is increased to 85 MPa·m 1 / 2 , achieving an optimized matching of "hard outside and tough inside".

[0062] Comparative Example 2: The KIC of the surface layer is 75 MPa·m 1 / 2 (due to insufficient cladding energy resulting in insufficient hardening), and the KIC of the substrate is reduced to 65 MPa·m 1 / 2 (due to excessive forging energy causing grain boundary embrittlement), the toughness gradient is reversed and the overall performance is unbalanced.

[0063] Microstructure analysis Example 1: The cladding layer is a fine martensite + carbide composite structure (the source of hardness), and the forging area forms dislocation strengthening + nano-precipitates through thermo-mechanical effects (the source of toughness), with a continuous gradient transition.

[0064] Comparative Example 2: The cladding layer is mainly composed of coarse ferrite (insufficient hardness). In the forging area, due to excessive energy, local remelting occurs, forming an amorphous / crystallized mixed zone (a stress concentration source), and microvoids (with a diameter of about 5 - 10 μm) appear at the interface.

[0065] Shear life test Example 1: In the simulated shear test (shearing a 2 - mm - thick stainless - steel plate), the shear - blade life reached 150,000 times, and there was no chipping at the blade edge.

[0066] Comparative Example 2: The shear life was only 40,000 times, and the failure mode was the concurrent occurrence of blade - edge collapse (insufficient hardness) and matrix cracking (decreased toughness).

Claims

1. A gradient-functionalized high-strength and tough shear blade material based on the time-sequence coupling of dual laser forging, characterized in that, It includes the following components by mass percentage: C: 0.6% - 0.7%, Cr: 4.5% - 5.5%, W: 1.8% - 2.2%, Mo: 1.2% - 1.5%, V: 0.8% - 1.0%, Ti: 2.8% - 3.2%, B: 0.008% - 0.015%, Ce: 0.02% - 0.05%, and the balance is Fe and inevitable impurity elements.

2. A preparation method of a gradient-functionalized high-strength and tough shearing blade based on the time-sequence coupling of dual-laser melting forging, characterized in that, It includes the following steps: Step 1, pre - continuous laser cladding: Continuously laser - clad the shear blade, and keep the energy density in the cladding area at 200 J / mm² - 300 J / mm²; Step 2, post - pulsed laser forging: Pulse - laser - forge the shear blade after continuous laser cladding in Step 1. The interval time between pulsed laser forging and continuous laser cladding is ≤50 ms, and the energy density in the forging area is 80 J / mm² - 120 J / mm²; Obtain a gradient - functionalized high - strength and tough shear blade based on the time - sequence coupling of dual - laser melting and forging.

3. The preparation method of the gradient-functionalized high-strength and tough shear blade based on the time-sequence coupling of dual laser forging according to claim 2, wherein, In Step 1, the laser cladding parameters are: the laser power is set at 2.5 kW - 3.5 kW, the scanning speed is 8 mm / s - 12 mm / s, the spot diameter is 3 mm - 4 mm, the overlapping rate is between 30% - 40%, and the thickness of the cladding layer is 1.5 - 2.5 mm.

4. The preparation method of the gradient-functionalized high-strength and tough shear blade based on the time-sequence coupling of double laser melting forging according to claim 2, characterized in that, In Step 2, the pulsed laser forging parameters are: the peak power of the pulsed laser is 4 kW - 6 kW, the frequency is 20 Hz - 30 Hz, the pulse width is 5 ms - 10 ms, the scanning speed is 5 mm / s - 8 mm / s, and the scanning path intersects with the cladding layer at 45°.