High-performance and high-yield heavy disc harrow blade manufacturing method based on novel boron steel

Abstract

The invention provides a high-performance and high-yield disc harrow blade manufacturing method based on novel boron steel. The disk blade structure is optimized, a forged round boss structure is adopted to replace a traditional connecting square hole, stress concentration is eliminated through an arc structure, the strength is improved, and the fatigue life is prolonged. The round boss is changed, forging and pressing procedures are reduced, the boss is directly formed during forging and pressing forming, and the production efficiency and the yield are improved. Component optimization design is carried out on the harrow blade material, and die forging pressure forming and composite heat treatment are synchronously carried out by adopting an integrated forming and critical cycle quenching process (machining-integrated forming-critical cycle quenching-tempering-shot blasting-plastic spraying-curing); stress concentration caused by micro-cracks and excessive punching during cold machining of the blank is avoided, the yield is increased, and the harrow blade has good strength, toughness and high wear resistance. The method is high in feasibility, easy to popularize, low in cost and expected to be widely applied to the field of agricultural machinery manufacturing.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a heavy-duty disc harrow blade with high performance and high yield based on a novel boron steel. Background Art

[0002] Currently, tillage machinery, represented by hydraulic plows, disc harrows, and rotary tillers, accounts for over 86% of agricultural production in my country. Heavy-duty disc harrows, owing to their versatility, robust soil-penetrating capabilities, and the ability to replace tilling with harrowing, have become a core piece of equipment in my country's agricultural landscape. As a key component of heavy-duty disc harrows, the performance of their blades directly impacts tillage efficiency and soil quality. During their service life, the blades withstand repeated impact and crushing from rocks and roots in the soil, accompanied by intense friction, creating an extremely harsh operating environment. Failure modes for disc harrow blades primarily include fracture due to intense impact from rocks or roots, and wear without fracture. Therefore, the steel used for these blades must possess a combination of mechanical properties, including high hardness, high wear resistance, and excellent strength-toughness properties (such as high tensile strength, high elongation, and excellent impact toughness). Heavy-duty disc harrow blades have long been manufactured from high-quality boron steel, using a precisely controlled manufacturing process supplemented by heat treatment. Boron steel harrow blades offer the advantages of low cost, long service life, and excellent performance. Currently, domestic agricultural machinery manufacturers primarily use 65Mn steel to produce key soil-contacting components such as heavy-duty disc harrow blades. However, the segregation of C or Mn elements in 65Mn steel can easily lead to quenching microcracks and temper brittleness, making domestically produced harrow blades highly susceptible to breakage during long-term service.

[0003] Furthermore, traditional disc harrow blade manufacturing processes often rely on forging followed by tempering, which presents challenges such as high material costs, complex and energy-intensive heat treatment processes, and low yield rates. Existing technologies often employ surface carburizing, laser cladding, or composite coatings to enhance the blade's wear and impact resistance. However, these processes require significant equipment investment and long processing cycles, significantly increasing manufacturing costs.

[0004] Furthermore, existing forging processes are prone to disc harrow blade flatness errors due to residual stress concentration, further reducing yield in subsequent shaping steps. Given the growing demand for agricultural mechanization, developing a high-performance disc harrow blade manufacturing technology that combines low cost, high yield, high wear resistance, and suitability for large-scale production is a key challenge in improving the cost-effectiveness of agricultural machinery and promoting the development of precision agriculture. Summary of the Invention

[0005] In view of the above problems in the prior art, the present invention provides a method for manufacturing a disc harrow blade with high performance and high yield based on a new type of boron steel.

[0006] First, the present invention designs a new type of rake blade, which is significantly different from the traditional rake blade structure. This structure eliminates the traditional connecting square hole design and replaces it with a forged circular boss connection structure. The continuously distributed arc structure eliminates the stress concentration phenomenon at the sharp corners of the traditional square hole. Changing to a circular boss can reduce the forging process and directly form the boss during forging, thereby improving production efficiency. The circular continuous structure itself is more conducive to dispersing stress, reducing stress concentration, and improving structural strength and fatigue life. In addition, reducing the number of punching holes means less material waste, higher material utilization, and lower costs. The boss design can also provide a better fit during installation and reduce looseness or wear.

[0007] On this basis, the present invention adds appropriate amounts of V, Nb and Mo elements on the basis of the composition design of existing 34MnB5 steel, and utilizes vacuum induction melting furnace to melt and obtain a new type of 34MnB5-M steel with fine and uniform grains. Among them, the V element can form fine carbides (such as VC) with the C element, refine the grains, and improve strength and toughness. The Nb element can generate highly dispersed strong carbide NbC, which can further prevent grain growth, and can further optimize hardenability by synergizing with the B element. The Mo element Mo is a strong carbide-forming element, which combines with carbon to generate fine carbides such as Mo2C, delays austenite decomposition, expands the quenching window, thereby improving the hardenability of steel, and can also suppress the formation of proeutectoid ferrite, promote the generation of acicular ferrite, refine the grains and improve toughness. The above alloying concept effectively improves the defect of the original 34MnB5 steel that the strength, hardness, toughness and plasticity cannot be improved simultaneously, and provides high-quality raw material supply for the subsequent manufacture of high-strength heavy-duty disc harrow blades.

[0008] In addition, the present invention has newly added integrated forming and critical cycle quenching process (machining-integrated forming-critical cycle quenching-tempering-shot peening-spraying-solidification) to the rake blade parts prepared based on novel connection structure design scheme and high-quality 34MnB5-M steel.By Deform software, simulate the best critical cycle quenching parameters.Wherein, integrated forming is the process that the rake blade blank is synchronously used to be integrally formed by forging die, so that not only can effectively avoid the stress concentration that microcrack defect and too much punching cause in the large deformation position of rake blade blank when cold working, improve yield rate.Can also significantly reduce the working load of press in rake blade blank forming process, be more conducive to energy conservation.In addition, critical cycle quenching process can make the nucleation and crystallization behavior of austenite and martensite realize the grain refinement of lower cost in the 34MnB5-M steel heating and cooling process, make grain boundary density increase simultaneously, hinder dislocation motion, to realize the good strength, toughness and high wear resistance of rake blade. The above-mentioned technical method effectively realizes the manufacture of heavy-duty disc harrow blades with high yield strength, high tensile strength, high toughness, high wear resistance, and high yield rate. The technical method used in the present invention is highly feasible, easy to promote, and low in cost, and is expected to be widely used in the field of agricultural machinery manufacturing.

[0009] The present invention relates to the field of manufacturing high-performance heavy-duty disc harrow blades and provides a method for manufacturing heavy-duty disc harrow blades that exhibit high yield strength, high tensile strength, high toughness, high wear resistance, and a high yield rate. The harrow blade components produced by this method combine high performance with high wear resistance, while also exhibiting a high yield rate. This method can effectively address the problems of existing heavy-duty disc harrow blades, which suffer from fracture and wear failure due to repeated impact and friction during operation, as well as the excessive production of defective products due to stress concentration caused by multiple punching operations. The method is expected to find widespread application in the manufacture of soil-contacting components for agricultural machinery. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A flow chart showing a method for manufacturing a high-performance, high-yield heavy-duty disc harrow blade based on a new boron steel according to one embodiment of the present invention is shown;

[0011] Figure 2 A three-dimensional structural diagram of a heavy-duty disc harrow blade according to one embodiment of the present invention is shown;

[0012] Figure 3 A two-dimensional engineering drawing showing a heavy-duty disc harrow blade according to one embodiment of the present invention;

[0013] Figure 4 A partial diagram illustrating the relationship of a heavy-duty disc harrow blade according to an embodiment of the present invention is shown;

[0014] Figure 5It shows the composite heat treatment process for the integrated molding of the heavy-duty disc harrow blade according to one embodiment of the present invention;

[0015] Figure 6 shows a microstructure photograph of a rake blade prepared according to Example 1;

[0016] Figure 7 shows the X-ray diffraction pattern of the rake blade prepared according to Example 1;

[0017] Figure 8 shows the prior austenite grain map of the rake blade prepared according to Example 1;

[0018] Figure 9 shows the tensile curve of the rake blade prepared according to Example 1;

[0019] Figure 10 The mechanical properties of the harrow blade prepared according to Example 1 are shown;

[0020] Figure 11 shows a microstructure photograph of a rake blade prepared according to Example 2;

[0021] Figure 12 shows the X-ray diffraction pattern of the rake blade prepared according to Example 2;

[0022] Figure 13 shows the prior austenite grain map of the rake blade prepared according to Example 2;

[0023] Figure 14 shows the tensile curve of the rake blade prepared according to Example 2;

[0024] Figure 15 The mechanical properties of the harrow blade prepared according to Example 2 are shown;

[0025] Figure 16 shows a microstructure photograph of a rake blade prepared according to Example 3;

[0026] Figure 17 shows the X-ray diffraction pattern of the rake blade prepared according to Example 3;

[0027] Figure 18 shows the prior austenite grain map of the rake blade prepared according to Example 3; DETAILED DESCRIPTION

[0028] According to the present invention, in order to solve the problem of fracture and wear failure of existing heavy-duty disc harrow blades due to repeated impact and friction during operation, as well as the problem of excessive defective products due to stress concentration caused by multiple punching in the production process, a method for manufacturing heavy-duty disc harrow blades with high yield strength, high tensile strength, high toughness and high wear resistance and high yield is provided. The process is as follows: Figure 1 shown.

[0029] First, the inventors provide (such as Figure 2 and Figure 3 A heavy-duty disc harrow blade with a forged circular boss connection structure (shown in FIG) comprises a circular boss 1, an arc transition area 2, a fillet 3, a fixed square hole 4, a flat transition area 5, a curved working area 6, and harrow teeth 7. The circular boss 1 is centered on the center of the entire harrow disc and is tangent to the arc transition area 2 (see FIG). Figure 4 ); the arc transition zone 2 is tangent to the circular boss 1 and the plane transition zone 5 (see Figure 4 ); the planar transition zone 5 is tangent to the arc-shaped working area 6; four fixed square holes 4 are evenly distributed in a circular pattern along the planar transition zone 5; and nine rake teeth 7 are evenly distributed along the circumference of the working area 6. A circular boss 1 serves as a connecting structure, replacing the traditional connecting square holes. The continuously distributed arc structure 2 eliminates stress concentration at the sharp corners of the traditional square holes, improving structural strength and fatigue life. The use of the circular boss 1 reduces the forging process, allowing the boss 1 to be formed directly during the forging process, thereby improving production efficiency and yield.

[0030] In contrast, the traditional solution is divided into two steps. The first step is to use flat forging to form a disc rake blade blank. The second step is to replace the rake blade blank obtained in the first step with a punching device to punch square holes. Replacing the equipment will affect production efficiency. At the same time, due to the square hole design, stress concentration will occur at the sharp corners, which will easily cause micro cracks at the sharp corners of the square hole during punching, reducing the yield.

[0031] Second, according to one embodiment of the present invention, by introducing appropriate amounts of V, Nb and Mo elements into the composition design of the existing 34MnB5 steel, a new type of 34MnB5-M steel with fine grains and uniform structure is obtained. Among them, the V element can form fine carbides (such as VC) with the C element, refine the grains, and improve strength and toughness. The Nb element can generate highly dispersed strong carbides NbC, which can further prevent grain growth, and at the same time, synergistically with the B element can further optimize hardenability. The Mo element is a strong carbide-forming element, which combines with carbon to generate fine carbides such as Mo2C, delaying the decomposition of austenite, expanding the quenching window, thereby improving the hardenability of the steel, and can also inhibit the formation of proeutectoid ferrite, promote the formation of acicular ferrite, refine the grains and improve strength and toughness.

[0032] According to one embodiment of the present invention, the heavy-duty disc harrow blades are manufactured using the new high-performance 34MnB5-M steel (a new boron steel alloy) designed in accordance with the present invention. This alloying treatment effectively improves the blades' strength, toughness, and wear resistance.

[0033] On this basis, the present invention innovatively designs an integrated molding and critical cycle quenching process for the rake blade components based on a new connection structure design and high-quality 34MnB5-M steel, including machining-integrated molding-critical cycle quenching-tempering-shot peening-plastic spraying-curing steps, such as Figure 5 As shown. The optimal critical cyclic quenching parameters were determined through Deform software simulation, including: keeping warm at 820℃~850℃ for 5 minutes, then cyclic quenching in PAG quenching liquid (water-soluble quenching liquid of polyalkylene glycol polymer, referred to as PAG quenching liquid) for 3 to 5 times, and finally tempering at 375℃~425℃ for 1 hour. Among them, integrated molding is a process of simultaneously molding the rake blade blank using a forging die. This technology can not only effectively prevent the occurrence of microcrack defects in the large deformation area during cold working and stress concentration problems caused by excessive punching, thereby improving the yield rate, but also can significantly reduce the workload of the press during the rake blade blank molding, which is beneficial to energy conservation and emission reduction. In addition, by applying the critical cycle quenching process to 34MnB5-M steel during the forming process, the present invention can optimize the nucleation and crystallization behavior of austenite and martensite during the heating and cooling processes, achieve grain refinement at a lower cost, increase the grain boundary density, and restrict dislocation movement, thereby giving the rake blade excellent strength, toughness and high wear resistance.

[0034] A method for manufacturing a heavy-duty disc harrow blade according to one embodiment of the present invention includes:

[0035] Step 1: Determine the optimized structure. This invention optimizes the original connection structure and uses a circular boss connection structure to replace the traditional connection square hole design, thereby determining a new heavy-duty disc harrow blade structure, such as Figure 2 and Figure 3 shown.

[0036] Step 2: Prepare a new 34MnB5-M steel and use it to manufacture the new heavy-duty disc harrow blade. Based on the existing 34MnB5 steel composition design, add 0.05-0.15% V, 0.06-0.08% Nb, and 0.3-0.5% Mo by mass. Melt the alloy in a medium-frequency induction melting furnace and cast it into slabs measuring 250*250mm. Heat the slabs to 880-930°C for 2.0-2.5 hours. After being removed from the furnace, they undergo a rough rolling cycle and a finish rolling cycle to form 6mm thick 34MnB5-M plates. The plates are then sheared into 700mm*700mm disc blade blanks.

[0037] Table 1 Comparison of chemical composition of new 34MnB5-M steel and existing 34MnB5 steel (mass fraction, %)

[0038]

[0039] Step 3: Rake blade blank die forging - integrated forming process.

[0040] During the design process of this manufacturing method, the inventors used Deform software to simulate the optimal critical cyclic quenching parameters, including: a 5-minute soak at 820°C to 850°C, followed by 3-5 cycles of quenching in a PAG quenching solution (a water-soluble quenching solution of polyalkylene glycol polymer, referred to as PAG quenching solution), and finally a 1-hour tempering treatment at 375°C to 425°C. The actual operation of this step was based on the results of the Deform software simulation.

[0041] The 34MnB5-M rake blade blank obtained in step 2 is placed in a heating furnace and heated to 820°C-850°C, kept warm for 5 minutes, and then transferred to the mold of a hot forging press for integrated die forging. During the die forging, the mold is slowly immersed in PAG (water-soluble quenching liquid of polyalkylene glycol polymer) quenching liquid to complete a quenching process to obtain a preliminarily formed rake blade.

[0042] Step 4: Rake-critical cycle quenching-tempering treatment, such as Figure 5 As shown. The treated rake disc from step 3 is heated to 830°C along with the mold, held at this temperature for 5 minutes, then transferred to a PAG quenching solution for quenching, and this cycle is repeated 2-5 times. After quenching, the rake disc is transferred to a tempering furnace at 375°C-425°C, held at this temperature for 1.0 hour, and then air-cooled to room temperature. Finally, shot peening, plastic spraying, and curing are performed.

[0043] Advantages of the present invention include:

[0044] The present invention provides a method for manufacturing high-performance, high-yield disc harrow blades using a novel boron steel. This method changes the traditional segmented processing method and comprehensively adopts a novel connection structure, a method for improving the material composition of the harrow blades, and an integrated molding manufacturing process, thereby greatly improving the performance and production yield of the harrow blades. The advantages and / or beneficial effects thereof include:

[0045] (1) The present invention changes the structure of the traditional rake blade and uses a forged circular boss connection structure to replace the traditional connecting square hole design. The continuously distributed arc structure eliminates the stress concentration phenomenon at the sharp corners of the traditional square hole, improves the structural strength and fatigue life, and avoids the stress concentration in the middle of the rake blade and the resulting fracture.

[0046] (2) Changing to a circular boss can reduce the forging process and directly form the boss during forging, thereby improving production efficiency and yield rate.

[0047] (3) The boss design can also provide a better fit during installation and reduce loosening or wear.

[0048] (4) The present invention introduces appropriate amounts of V, Nb and Mo elements into the composition design of the existing 34MnB5 steel to obtain a new type of 34MnB5-M steel with fine grains and uniform structure, thereby effectively improving the strength, toughness and high wear resistance of the heavy-duty disc harrow blade.

[0049] (5) Based on the above-mentioned new 34MnB5-M steel as raw material, the present invention simulates the optimal critical cycle quenching parameters through Deform software, adopts the integrated process of die forging and critical cycle quenching, and simultaneously completes the integrated forming and one-time quenching of the rake blade. It prevents the occurrence of microcrack defects in the large deformation area during the cold working process and the stress concentration problem caused by excessive punching, thereby improving the yield rate; and significantly reduces the workload of the press during the forming of the rake blade blank, which is conducive to energy conservation and emission reduction. At the same time, the critical cycle quenching process is carried out simultaneously during the forming process, which can achieve grain refinement, increase the grain boundary density, and limit dislocation movement, thereby giving the rake blade excellent strength, toughness and high wear resistance.

[0050] (6) The process of the present invention simplifies the manufacturing process of the rake blade, improves the yield rate and reduces the cost.

[0051] (7) The heavy-duty disc harrow blades produced by the process of the present invention were tested in actual field operations on sandy soil, which showed that the wear failure rate of the harrow blades was 4.0%-4.6%, the fracture failure rate was 3.5%-4.2%, and the average service life of a single harrow blade was 11,300 mu to 12,800 mu, which is 50% to 70% higher than the existing ones (the service life of a single harrow blade is about 7,500 mu).

[0052] In summary, the present invention provides a high-performance, high-yield integrated molding and manufacturing method for disc harrow blades based on new boron steel, which can not only effectively solve the major problems of insufficient strength, toughness and high wear resistance of existing heavy-duty disc harrow blades during operation, but also greatly improve the yield in the production process and reduce production costs. It has important and broad application prospects in the fields of manufacturing key components of agricultural machinery.

[0053] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solutions of the present invention are described in detail below through examples, but the applicable scope of the present invention is not limited to the following examples.

[0054] Example 1:

[0055] Step 1: Determine the optimized structure. The present invention optimizes the original connection structure and uses a circular boss connection structure to replace the traditional connection square hole design to determine the new heavy-duty disc harrow blade structure.

[0056] Step 2: Prepare the new 34MnB5-M steel. Based on the existing 34MnB5 steel composition, 0.05% V, 0.06% Nb, and 0.3% Mo were added by mass. The alloy was melted in a medium-frequency induction melting furnace and cast into 250 x 250 mm slabs. The slabs were heated to 880°C and held for 2.0 hours. After removal from the furnace, they underwent a rough rolling cycle and a second finishing rolling cycle to form 6 mm thick 34MnB5-M sheets. The sheets were then sheared into 700 mm x 700 mm raked blanks.

[0057] Table 1 Comparison of chemical composition of new 34MnB5-M steel and existing 33MnB5 steel (mass fraction, %)

[0058]

[0059] Step 3: Rake blank die forging - integrated forming process. The 34MnB5-M steel billet from step 2 is heated to 820°C along with the die. After holding at this temperature for 5 minutes, it is removed from the furnace and transferred into the die for integrated die forging. While forging, the die is slowly immersed in PAG quenching liquid to complete the first quenching process.

[0060] Step 4: Rake - Critical Cycle Quenching - Tempering. Based on the critical cycle quenching parameters simulated by the Deform software, the rake from Step 3 is heated in a furnace to 820°C, held at this temperature for 5 minutes, then quenched in a PAG quenching solution. This cycle is repeated twice. After quenching, the rake is transferred to a tempering furnace at 400°C for 1 hour, then air-cooled to room temperature. Finally, shot peening, plastic spraying, and curing are performed.

[0061] The microstructure of the new 34MnB5-M rake blade was observed using a FEI Nova Nano450 field emission scanning electron microscope and a Leica optical microscope. Before the test, the samples were mounted, ground and polished in sequence. Figure 6 This is the OM image of the surface structure of the new 34MnB5-M rake blade of this embodiment ( Figure 6 a) and SEM images ( Figure 6 b). It can be seen that the 34MnB5-M rake blades are small in size and have a uniformly distributed martensite composition. Figure 8 The metallographic diagram of the original austenite grains shows that the average grain length is about 6.67 μm ( Figure 8 ). Figure 8 This is a statistical metallographic diagram of the original austenite grains of the surface structure of the new 34MnB5-M rake blade after being treated in Example 1.

[0062] The phase composition of the new 34MnB5-M rake was analyzed by X-ray diffraction (XRD). The two samples were tested on a SmartLab X-ray diffractometer using a Co target. The diffraction angle scan range was 20-90° and the scanning step size was 3° / min. Figure 7 The phase composition of the surface layer material of the novel 34MnB5-M rake blade of this embodiment is shown. It can be seen that the novel 34MnB5-M rake blade material is mainly composed of α phase.

[0063] The room temperature tensile test of the new 34MnB5-M rake was carried out on an Instron-8801 tensile testing machine. Before the test, the surface and cross section of the tensile specimen were polished to remove the oxide scale and cutting marks. During the test, the strain value of the specimen was measured by an electronic extensometer at a strain rate of 1×10 -3 s -1 . Figure 9 The stress-strain curve of the new 34MnB5-M harrow blade of this embodiment during the tensile process is shown. As can be seen, the new 34MnB5-M harrow blade has a yield strength of 1312 MPa, a tensile strength of 1382 MPa, and an elongation of 9.1%. This shows that the new 34MnB5-M harrow blade achieves high yield strength, high tensile strength, and good plasticity.

[0064] The hardness test of the new 34MnB5-M harrow blade was carried out using a FR-3E digital Rockwell hardness tester and the room temperature impact test was carried out using a NI300 impact testing machine. Figure 10 The surface hardness and impact toughness test results of the new 34MnB5-M harrow blade material of this embodiment are shown. It can be seen that the surface hardness of the new 34MnB5-M harrow blade is 46.3HRC and the impact absorbed energy is 48.5J, indicating that the new 34MnB5-M harrow blade has high wear resistance and good toughness.

[0065] In summary, the performance of the harrow blade produced in Example 1 is as follows:

[0066]

[0067] By conducting actual field operation tests on sandy soil using a heavy-duty disc harrow equipped with harrow blades produced in Example 1, the wear failure rate of the harrow blades was 4.6%, the fracture failure rate was 4.2%, and the average service life of a single harrow blade was 11,300 mu, which is approximately 50% higher than the service life of existing harrow blades (the service life of an existing single harrow blade is approximately 7,500 mu).

[0068] Example 2:

[0069] Step 1: Determine the optimized structure. The present invention optimizes the original connection structure and uses a circular boss connection structure to replace the traditional connection square hole design to determine the new heavy-duty disc harrow blade structure.

[0070] Step 2: Prepare the new 34MnB5-M steel. Based on the existing 34MnB5 steel composition, 0.10% V, 0.07% Nb, and 0.4% Mo were added by mass. The alloy was melted in a medium-frequency induction melting furnace and cast into 250 x 250 mm slabs. The slabs were heated to 900°C and held for 2.5 hours. After removal from the furnace, they underwent a rough rolling cycle and a second finishing rolling cycle to form 6 mm thick 34MnB5-M sheets. The sheets were then sheared into 700 mm x 700 mm raked blanks.

[0071] Table 1 Comparison of chemical composition of new 34MnB5-M steel and existing 33MnB5 steel (mass fraction, %)

[0072]

[0073] Step 3: Rake blank die forging and integrated forming. Based on the critical cycle quenching parameters simulated by the Deform software, the 34MnB5-M billet from Step 2 is heated to 835°C in a furnace. After holding for 5 minutes, it is removed from the furnace and transferred into a die for integrated die forging. Simultaneously, the die is slowly immersed in PAG quenching liquid to complete the first quenching process.

[0074] Step 4: Rake blade-critical cycle quenching and tempering treatment. The blade from step 3 is heated in a furnace to 835°C, held at this temperature for 5 minutes, then transferred to a PAG quenching solution for quenching. This cycle is repeated three times. After quenching, the blade is transferred to a tempering furnace at 375°C, held at this temperature for 1.0 hour, and then air-cooled to room temperature. Finally, shot peening and plastic spraying are performed.

[0075] The microstructure of the new 34MnB5-M rake was observed using a FEI Nova Nano450 field emission scanning electron microscope and a Leica optical microscope. Figure 11 This is the OM image of the surface structure of the new 34MnB5-M rake blade of this embodiment ( Figure 11 a) and SEM images ( Figure 11 b). It can be seen that the 34MnB5-M rake blades are small in size and have a uniformly distributed martensite composition. Figure 13 The original austenite grain metallographic diagram shows that the average grain length is about 5.45 μm ( Figure 13 ). Figure 13 It refers to the statistical metallographic diagram of the original austenite grains of the surface structure of the new 34MnB5-M rake blade after being treated in Example 1.

[0076] The phase composition of the new 34MnB5-M rake was analyzed by X-ray diffraction (XRD). The two samples were tested on a SmartLab X-ray diffractometer using a Co target. The diffraction angle scan range was 20-90° and the scanning step size was 3° / min. Figure 12 The phase composition of the novel 34MnB5-M rake blade material of this embodiment is shown. It can be seen that the novel 34MnB5-M rake blade material is mainly composed of α phase.

[0077] Room temperature tensile tests were conducted on the new 34MnB5-M rake blade using an Instron-8801 tensile testing machine. The tensile specimens used were standard specimens cut radially from the rake blade. Before the test, the surface and cross-section of the tensile specimens were polished to remove scale and cut marks. During the test, the strain value of the specimens during the tensile process was measured using an electronic extensometer at a strain rate of 1×10 -3 s -1 . Figure 14 The stress-strain curve of the new 34MnB5-M harrow blade of this embodiment during the tensile process is shown. As can be seen, the new 34MnB5-M harrow blade has a yield strength of 1394 MPa, a tensile strength of 1436 MPa, and an elongation of 9.7%. This shows that the new 34MnB5-M harrow blade achieves high yield strength, high tensile strength, and good plasticity.

[0078] The hardness test of the new 34MnB5-M harrow blade was carried out using a FR-3E digital Rockwell hardness tester and the room temperature impact test was carried out using a NI300 impact testing machine. Figure 15 The surface hardness and impact toughness test results of the new 34MnB5-M harrow blade material of this embodiment are shown. It can be seen that the surface hardness of the new 34MnB5-M harrow blade is 48.7HRC and the impact absorbed energy is 51.7J, indicating that the new 34MnB5-M harrow blade has high wear resistance and good toughness.

[0079] In summary, the performance of the harrow blade produced in Example 2 is as follows:

[0080]

[0081] By conducting actual field operation tests on sandy soil using a heavy-duty disc harrow equipped with harrow blades produced in Example 2, the wear failure rate of the harrow blades was 4.4%, the fracture failure rate was 3.8%, and the average service life of a single harrow blade was 11,950 mu, which is approximately 59% higher than the service life of existing harrow blades (the service life of an existing single harrow blade is approximately 7,500 mu).

[0082] Example 3:

[0083] Step 1: Determine the optimized structure. The present invention optimizes the original connection structure and uses a circular boss connection structure to replace the traditional connection square hole design to determine the new heavy-duty disc harrow blade structure.

[0084] Step 2: Prepare the new 34MnB5-M steel. Based on the existing 34MnB5 steel composition, 0.15% V, 0.08% Nb, and 0.5% Mo were added by mass. The alloy was melted in a medium-frequency induction melting furnace and cast into 250 x 250 mm slabs. The slabs were heated to 930°C and held for 2 hours. After removal from the furnace, they underwent a rough rolling cycle and a second finishing rolling cycle to form 6 mm thick 34MnB5-M sheets. The sheets were then sheared into 700 mm x 700 mm long rake blanks.

[0085] Table 1 Comparison of chemical composition of new 34MnB5-M steel and existing 33MnB5 steel (mass fraction, %)

[0086]

[0087] Step 3: Rake blank die forging and integrated forming. Based on the critical cycle quenching parameters simulated by the Deform software, the 34MnB5-M billet from Step 2 is heated to 850°C in a furnace. After holding for 5 minutes, it is removed from the furnace and transferred into a die for integrated die forging. Simultaneously, the die is slowly immersed in PAG quenching liquid to complete the first quenching process.

[0088] Step 4: Rake blade-critical cycle quenching and tempering treatment. The blade from step 3 is heated in a heating furnace to 850°C, held at this temperature for 5 minutes, then transferred to PAG quenching liquid for quenching, and the cycle is repeated five times. After quenching, the blade is transferred to a tempering furnace at 425°C, held at this temperature for 1.0 hour, and then air-cooled to room temperature. Finally, shot peening and plastic spraying are performed.

[0089] The microstructure of the new 34MnB5-M rake was observed using a FEI Nova Nano450 field emission scanning electron microscope and a Leica optical microscope. Figure 16 This is the OM image of the surface structure of the new 34MnB5-M rake blade of this embodiment ( Figure 16 a) and SEM images ( Figure 16 b). It can be seen that the 34MnB5-M rake blades are small in size and have a uniformly distributed martensite composition. Figure 18 The metallographic diagram of the original austenite grains shows that the average grain length is about 4.74 μm ( Figure 18 ).

[0090] The phase composition of the new 34MnB5-M rake was analyzed by X-ray diffraction (XRD). The two samples were tested on a SmartLab X-ray diffractometer using a Co target. The diffraction angle scan range was 20-90° and the scanning step size was 3° / min. Figure 17 The phase composition of the novel 34MnB5-M rake blade material of this embodiment is shown. It can be seen that the novel 34MnB5-M rake blade material is mainly composed of α phase.

[0091] The mechanical property test of the rake blade is consistent with the method of Example 1 and Example 2.

[0092] In summary, the performance of the harrow blade produced in Example 3 is as follows:

[0093]

[0094] By conducting actual field operation tests on sandy soil using a heavy-duty disc harrow equipped with harrow blades produced in Example 3, the wear failure rate of the harrow blades was 4.0%, the fracture failure rate was 3.5%, and the average service life of a single harrow blade was 12,800 mu, which is approximately 70% higher than the service life of existing harrow blades (the service life of an existing single harrow blade is approximately 7,500 mu).

Claims

1. A heavy-duty disc harrow blade with a forged circular boss connection structure, characterized in that include: A circular boss (1), an arc transition area (2), four fixed square holes (4), a plane transition area (5), an arc surface working area (6) and a plurality of rake teeth (7), in: The circular boss (1) is a circular raised portion with the center of the heavy disc harrow blade as the center and facing the center. The circular boss (1) is tangent to the arc transition zone (2); The arc transition zone (2) is tangent to the circular boss (1) and the plane transition zone (5) respectively; The plane transition area (5) is tangent to the arc surface working area (6); Four fixed square holes (4) are evenly distributed in a circular shape along the plane transition zone (5); A plurality of rake teeth (7) are evenly distributed along the circumference of the working area (6).

2. The heavy-duty disc harrow blade according to claim 1, characterized in that: The circular boss (1) has rounded corners (3).

3. The heavy-duty disc harrow blade according to claim 1, characterized in that: The plurality of rake teeth (7) is nine rake teeth.

4. The heavy-duty disc harrow blade according to any one of claims 1 to 3, characterized in that The heavy-duty disc harrow blade is made of new high-performance 34MnB5-M steel, which includes: The novel high-performance 34MnB5-M steel is obtained by introducing appropriate amounts of V, Nb and Mo elements into the composition design of the existing 34MnB5 steel, thereby obtaining a novel 34MnB5-M steel having fine grains and uniform structure.

5. The heavy-duty disc harrow blade according to claim 4, characterized in that The preparation method based on the new high-performance 34MnB5-M steel comprises: A) harrow sheet stock preparation step, comprising: A1) Adding 0.05-0.15% V, 0.06-0.08% Nb, and 0.3-0.5% Mo to the existing 34MnB5 steel, the specific chemical composition comparison includes: The unit is mass fraction%, A2) Melting the alloy in a medium frequency induction melting furnace and casting it into slabs; A3) heating the slab to 880-930°C, holding the temperature for 2.0-2.5 hours, and then subjecting it to a first rough rolling and a second finish rolling to form a 6 mm thick plate. A4) Shear the plate into rake blanks, B) The rake blade blank die forging-integrated forming process includes: B1) The 34MnB5-M rake blank obtained in step A is placed in a heating furnace and heated to 820°C-850°C, and kept warm for 5 minutes to obtain a preliminarily heated rake blank. B2) After the heated rake blade blank is taken out of the furnace after the treatment in step B1, it is transferred to the mold of a hot forging press for integrated die forging. During the die forging, the mold is slowly immersed in PAG quenching liquid to complete a quenching process to obtain a preliminarily formed rake blade. C) performing a rake-critical cycle quenching-tempering treatment, including heating the preliminarily formed rake along with the mold to 830°C, holding the temperature for 5 minutes, and then transferring the rake into a PAG quenching liquid for quenching, and performing the cycle 2-5 times; after the quenching is completed, transferring the rake into a tempering furnace at a temperature of 375°C-425°C for 1.0 hour, and then air cooling to room temperature.

6. The heavy-duty disc harrow blade according to claim 5, characterized in that The preparation method further comprises: D) Shot blasting, plastic spraying and curing treatment.

7. A method for preparing a new type of high-performance 34MnB5-M steel for manufacturing heavy-duty disc harrow blades, characterized in that include: A) harrow sheet stock preparation step, comprising: A1) Adding 0.05-0.15% V, 0.06-0.08% Nb, and 0.3-0.5% Mo to the existing 34MnB5 steel, the specific chemical composition comparison includes: The unit is mass fraction%, A2) Melting the alloy in a medium frequency induction melting furnace and casting it into slabs; A3) heating the slab to 880-930°C, holding the temperature for 2.0-2.5 hours, and then subjecting it to a first rough rolling and a second finish rolling to form a 6 mm thick plate. A4) Shear the plate into rake blanks, B) The rake blade blank die forging-integrated forming process includes: B1) The 34MnB5-M rake blank obtained in step A is placed in a heating furnace and heated to 820°C-850°C, and kept warm for 5 minutes to obtain a preliminarily heated rake blank. B2) After the heated rake blade blank is taken out of the furnace after the treatment in step B1, it is transferred to the mold of a hot forging press for integrated die forging. During the die forging, the mold is slowly immersed in PAG quenching liquid to complete a quenching process to obtain a preliminarily formed rake blade. C) performing a rake-critical cycle quenching-tempering treatment, including heating the preliminarily formed rake along with the mold to 830°C, holding the temperature for 5 minutes, and then transferring the rake into a PAG quenching liquid for quenching, and performing the cycle 2-5 times; after the quenching is completed, transferring the rake into a tempering furnace at a temperature of 375°C-425°C for 1.0 hour, and then air cooling to room temperature.

8. The preparation method according to claim 7, characterized in that Further including: D) Shot blasting, plastic spraying and curing treatment.

9. The preparation method according to claim 7, characterized in that The heavy-duty disc harrow blade is the heavy-duty disc harrow blade according to any one of claims 1 to 6.

10. The preparation method according to claim 7, characterized in that: The slab size is 250*250mm; The size of the rake blade blank is 700mm*700mm.

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