A disc harrow blade and a method of manufacturing the same

Abstract

The application relates to a disc harrow blade and a preparation method thereof, and belongs to the technical field of high-strength steel for agricultural machinery; the microstructure of the edge part of the disc harrow blade is based on martensite, and the microstructure of the core part of the disc harrow blade is based on ferrite and pearlite; the distribution of the microstructure ensures the high wear resistance of the edge part of the disc harrow blade during work, and ensures the high toughness of the core part of the disc harrow blade, so that brittle fracture or cracking phenomenon is avoided during service.

Description

Technical Field

[0001] This invention belongs to the technical field of high-strength steel for agricultural machinery, and specifically relates to a disc harrow blade and its preparation method. Background Technology

[0002] Disc harrow blades, as key components of modern large-scale agricultural machinery, play a crucial role in cultivating large areas of farmland. By rotating in the field, they loosen the soil and remove large particles. Due to the complex environment of farmland, disc harrow blades face wear from sand and gravel during their service, requiring parts with high wear resistance. They also encounter hard objects such as rocks, facing impacts from stones in the field, necessitating high toughness.

[0003] Currently, disc rake blades are made of medium-to-high carbon steel such as boron steel (27MnB, 30MnB, 34MnB, and 40MnB), with thicknesses ranging from 3.0mm to 12.0mm. The manufacturing process includes blanking, hot forming, shot peening, and baking paint. The hot stamping process involves fully austenitizing the flat plate, forming it at high temperature in a mold, and then cooling it in water. The resulting microstructure is a martensitic matrix, which possesses high hardness and wear resistance. However, parts with a martensitic matrix have poor toughness, making them prone to brittle fracture when encountering hard objects such as stones during service, thus affecting work efficiency. Summary of the Invention

[0004] The purpose of this application is to provide a disc rake blade and its preparation method to solve the problem of poor toughness of current disc rake blades.

[0005] This invention provides a disc rake blade, wherein the microstructure of the edge of the disc rake blade is based on martensite, and the microstructure of the core of the disc rake blade is based on ferrite and pearlite.

[0006] Optionally, the edge hardness of the disc rake blade is 47-57 HRC, and the core hardness of the disc rake blade is 18-23 HRC.

[0007] Based on the same inventive concept, embodiments of the present invention also provide a method for preparing the disc rake blade as described above, the method comprising:

[0008] The steel coil is leveled and then cut into blanks to obtain the material to be cut.

[0009] The material to be cut is cut and then stamped to obtain a disc blank;

[0010] The disk blank is heated at the edges and then hot-stamped and quenched to obtain a quenched disk blank.

[0011] The disc quenching blank is shot blasted, and then is baked and painted to obtain a disc harrow blade.

[0012] Optionally, the edge heating is inductive heating.

[0013] Optionally, the width of the edge heating is 30-150 mm, measured from the outer extension of the disc blank as zero coordinate.

[0014] Optionally, the temperature of the edge heating is 860-940 ℃, and the holding time of the edge heating is 1-10 min.

[0015] Optionally, the interval between the hot stamping and the quenching to the edge heating is ≤15 s, and the holding time of the hot stamping is ≥30 s.

[0016] Optionally, the steel coil is medium-high carbon steel.

[0017] Optionally, the medium-high carbon steel is one of 27MnB, 30MnB, 34MnB and 40MnB.

[0018] Optionally, the temperature of the baking and painting is 150-240 ℃, and the time of the baking and painting is 15-30 min.

[0019] The one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0020] The disc harrow blade provided by the embodiments of the present application has a structure in which the edge part is a matrix of martensite, and the core part retains a structure of ferrite + pearlite. Such a structure distribution ensures high wear resistance of the edge part of the disc harrow blade during work, and ensures high toughness of the core part of the disc harrow blade, so that brittle fracture or cracking phenomenon is avoided during service.

[0021] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, the embodiments of the present application can be implemented according to the content of the description, and in order to make the above and other purposes, characteristics and advantages of the present application more obvious and easy to understand, the following will describe the specific embodiments of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0023] Figure 1 is a structure schematic view of the disc harrow blade provided by the embodiments of the present application;

[0024] Figure 2 is a schematic diagram of inductive heating provided by an embodiment of the present application;

[0025] Figure 3 is a production process diagram provided by an embodiment of the present application;

[0026] Figure 4 is a microstructure diagram of a disc harrow blade core provided by embodiment 1 of the present application;

[0027] Figure 5 is a microstructure diagram of a disc harrow blade edge provided by embodiment 1 of the present application;

[0028] Figure 6 is a flowchart of a method provided by an embodiment of the present application. DETAILED DESCRIPTION

[0029] The advantages and various effects of the present application will be more clearly presented hereinafter with specific embodiments and examples. Those skilled in the art should understand that these specific embodiments and examples are used to illustrate the present application, rather than limit the present application.

[0030] Throughout the specification, unless otherwise specifically indicated, the terms used herein are to be understood as having the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as generally understood by those skilled in the art to which the present application belongs. If there is a conflict, the present specification takes precedence.

[0031] Unless otherwise specifically indicated, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0032] The technical solution of the embodiments of the present application is to solve the above technical problems, and the general idea is as follows:

[0033] The process of cold forming and hot forming is adopted, the blanked parts are laser cut into accurate shapes, cold stamping is adopted in the first step to obtain the shape of the disc harrow blade, the edge of the disc harrow blade is inductively heated in the second step, the edge is rapidly austenitized and immediately quenched (boron steel is quenched in water), the edge is obtained with a structure of martensite as a matrix (hardness 47-57HRC), and the core retains a structure of ferrite + pearlite (hardness 18-23HRC). Such distribution of the structure ensures high wear resistance of the edge of the disc harrow blade during work, and on the other hand, ensures high toughness of the core of the disc harrow blade to avoid brittle fracture or cracking phenomenon during service.

[0034] According to a typical embodiment of the present application, a disc harrow blade is provided, the microstructure of the edge of the disc harrow blade is based on martensite, and the microstructure of the core of the disc harrow blade is based on ferrite and pearlite.

[0035] In some embodiments, the edge portion of the disc harrow blade has a hardness of 50-57 HRC, and the core portion of the disc harrow blade has a hardness of 18-23 HRC.

[0036] According to another typical embodiment of the present application, there is provided a method for manufacturing a disc harrow blade as described above, the method comprising:

[0037] S1. flattening a steel coil, and then blanking the flattened steel coil to obtain a blank to be cut;

[0038] Specifically, the steel coil is first flattened into a flat plate, and then blanked into a desired square shape to obtain the blank to be cut.

[0039] In some embodiments, the steel coil is a medium-high carbon steel.

[0040] In this embodiment, the medium-high carbon steel includes one of 27MnB, 30MnB, 34MnB and 40MnB.

[0041] S2. cutting the blank to be cut, and then stamping the blank to obtain a disc blank; it should be noted that in this step, the stamping is cold stamping, and the stamping is performed into a desired shape.

[0042] Specifically, the blank to be cut after blanking is laser cut into a precise shape required by the disc harrow blade, including the opening of the edge portion, etc. In other embodiments, in addition to laser cutting, the cutting can also be performed by die blanking.

[0043] S3. edge heating the disc blank, and then hot stamping and quenching the disc blank to obtain a disc quenched blank;

[0044] In some embodiments, the edge heating is performed by induction heating.

[0045] In some embodiments, the width of the edge heating is 30-150 mm, measured from the outer extension edge of the disc blank as the zero coordinate.

[0046] In some embodiments, the temperature of the edge heating is 860-940℃, and the holding time of the edge heating is 1-10 min. The induction heating time is different according to the thickness.

[0047] The reason for controlling the temperature of the edge heating to be 860-940℃ and the holding time to be 1-10 min is to completely austenitize the region of the edge portion that needs to be quenched during heating, so as to ensure that the martensite is obtained as the matrix during quenching. If the value is too large, the grains will be coarse, and the toughness will be reduced. If the value is too small, it may cause incomplete austenitization, resulting in the presence of a large number of ferrite and other phases in the structure, which cannot guarantee the hardness and wear resistance of the edge portion.

[0048] In some embodiments, the time interval of the hot stamping quenching to the edge heating is ≤15s, and the dwell time of the hot stamping quenching is ≥30s.

[0049] The time interval of the hot stamping quenching to the edge heating is controlled to be ≤15s, and the transfer time affects the temperature reduction. The faster the transfer is, the better the hardness after quenching is. If the time interval is too large, ferrite is generated, and the hardness and wear resistance of the edge cannot be guaranteed.

[0050] Specifically, the part after induction heating is transferred to a hot stamping die for hot stamping quenching. Boron steel (i.e., 27MnB, 30MnB, 34MnB, and 40MnB) is quenched by water. The time from induction heating to hot stamping is ≤15s, and the dwell time is ≥30s.

[0051] The hot stamping quenching process adopts a press quenching process, i.e., water quenching during the dwell process, to obtain a good shape and high edge hardness.

[0052] S4. The disc quenching blank is shot blasted, and then baked and painted to obtain a disc harrow blade.

[0053] The purpose of shot blasting is to remove the surface scale. The baking and painting process is similar to a tempering process, which can eliminate the internal stress of the edge quenching and improve the toughness of the edge of the disc harrow blade.

[0054] In some embodiments, the temperature of the baking and painting is 150-240℃, and the time of the baking and painting is 15-30min.

[0055] The reasons for controlling the temperature of the baking and painting to be 150-240℃ and the time of the baking and painting to be 15-30min are as follows: (1) to ensure the quality of the baking and painting; (2) the baking and painting process is essentially a tempering process, which can reduce the internal stress of the material and improve the toughness; (3) to reduce the hydrogen embrittlement sensitivity. In the present application, the material is medium carbon steel, and the microstructure after edge quenching is based on martensite. The hydrogen embrittlement sensitivity is high. A low-temperature tempering process can reduce the hydrogen content in the material and reduce the hydrogen embrittlement sensitivity. If the temperature is too high, it enters the first type of tempering brittleness zone, which affects the toughness. If the time is too long, the hardness decreases too much, which cannot guarantee the hardness. If the temperature is too low or the time is too short, the quality of the baking and painting is affected, the internal stress cannot be fully eliminated, and the effect of reducing the hydrogen embrittlement sensitivity cannot be achieved.

[0056] The disc harrow blade and the preparation method thereof of the present application will be described in detail below in combination with examples, comparative examples, and experimental data.

[0057] Example 1

[0058] A disc harrow blade, the mass percentage of the components of which is shown in the following table,

[0059] C Si Mn P S Alt Cr Ti B N 0.339 0.247 1.43 0.009 0.001 0.041 0.19 0.052 0.0023 0.0035

[0060] The balance is iron and unavoidable impurities.

[0061] The preparation process is as follows:

[0062] The steel coil is opened, blanked, laser cut, stamped, induction heated, quenched, shot blasted, and painted. The thickness of the steel coil is 4 mm, the diameter after laser cutting is 480 mm, the width of the edge induction heating is 50 mm, the temperature of the induction heating is 900 °C, the holding time is 5 min, it is transferred to a press quench die for water quenching, the holding time is 32 s, then the die is opened, the opening temperature is 100 °C. Then the surface oxide is removed by shot blasting, and then the paint is baked, the temperature is 200 °C, and the time is 20 min. The shape of the disc harrow blade is shown in Figure 1 , the schematic diagram of induction heating is shown in Figure 2 , the microstructure of the center of the disc harrow blade is shown in Figure 4 , and the microstructure of the edge of the disc harrow blade is shown in Figure 5 .

[0063] Example 2

[0064] A disc harrow blade, the mass percentage of the components is shown in the following table,

[0065] C Si Mn P S Alt Cr Ti B N 0.331 0.235 1.38 0.008 0.002 0.042 0.15 0.043 0.0021 0.0040

[0066] The balance is iron and unavoidable impurities.

[0067] The preparation process is as follows:

[0068] The steel coil is opened, blanked, laser cut, stamped, induction heated, quenched, shot blasted, and painted. The thickness of the steel coil is 6 mm, the diameter after laser cutting is 560 mm, the width of the edge induction heating is 80 mm, the temperature of the induction heating is 900 °C, the holding time is 7 min, it is transferred to a press quench die for water quenching, the holding time is 33 s, then the die is opened, the opening temperature is 110 °C. Then the surface oxide is removed by shot blasting, and then the paint is baked, the temperature is 210 °C, and the time is 22 min.

[0069] Example 3

[0070] A disc harrow blade, the mass percentage of the components is shown in the following table,

[0071] C Si Mn P S Alt Cr Ti B N 0.302 0.241 1.29 0.007 0.001 0.043 0.17 0.047 0.0022 0.0038

[0072] The balance is iron and unavoidable impurities.

[0073] The preparation process is as follows:

[0074] The steel coil is opened, blanked, laser cut, stamped, inductively heated, quenched, shot blasted and painted. The steel coil has a thickness of 8 mm, a diameter of 660 mm after laser cutting, an inductive heating width of 120 mm, an inductive heating temperature of 930℃, a holding time of 8 min, is transferred to a press quenching die for water quenching, a holding time of 40 s, then the die is opened, and the opening temperature is 105℃. Then the surface oxide is removed by shot blasting, and then the paint is baked at a temperature of 220℃ for 25 min.

[0075] Comparative Example 1

[0076] The present comparative example selects a currently published patent of a disc harrow blade, the application publication number of which is CN 106521102A, the mass percentage of the components of which is shown in the following table,

[0077] C Si Mn P S Alt Cr Ti B N 0.3 0.25 1.28 0.012 0.002 0.045 0.3 0.044 0.0008 0.0037

[0078] The rest is iron and unavoidable impurities.

[0079] The production process is quenching and tempering, the heating temperature is 890-930℃, the holding time is 13-25 min, the quenching medium is cooling water. The tempering temperature is 190-210℃, and the tempering time is 4-10 h.

[0080] Experimental Example

[0081] The disc harrow blades prepared from Examples 1-3 and Comparative Example 1 are subjected to performance testing, and the test results are shown in the following table.

[0082] Core hardness Edge hardness (induction heating zone) Example 1 20-22 53-55 Example 2 19-21 51-53 Example 3 19-21 49-51 Comparative Example 1 48-53 48-53

[0083] From the above table, it can be seen that the disc harrow blade prepared by the method provided in the present application has different hardness in the core and the edge, the low hardness in the core ensures high toughness, and the high hardness in the edge ensures wear resistance. The disc harrow blade of the comparative example has high hardness throughout the blade, and has a greater risk of breaking during service.

[0084] Meanwhile, the method provided in the present application does not have a tempering step, and the comparative example requires long-term tempering, which affects the production efficiency. Because the present application only locally inductively heats and quenches, the toughness of the entire disc harrow blade can still be ensured without tempering.

[0085] The one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0086] (1) The disc harrow blade edge provided by the embodiment of the present application has a structure (hardness 47-57HRC) with martensite as a matrix, and the core retains a structure (hardness 18-23HRC) of ferrite + pearlite, which on the one hand ensures high wear resistance of the edge of the disc harrow blade during work, and on the other hand ensures high toughness of the core of the disc harrow blade, avoiding brittle fracture or cracking phenomenon during service;

[0087] (2) The method provided by the embodiment of the present application adopts a process means of cold forming and hot forming, and the blanked part is laser cut into an accurate shape, cold stamping is adopted in the first step to obtain the shape of the disc harrow blade, the edge of the disc harrow blade is inductively heated in the second step, the edge is rapidly austenitized, and is immediately quenched (boron steel is quenched in water), to obtain a structure (hardness 47-57HRC) with martensite as a matrix in the edge, and a structure (hardness 18-23HRC) of ferrite + pearlite in the core.

[0088] Finally, it should be noted that the terms "comprising", "including", or any other variant thereof are intended to cover non-exclusive inclusions, so that processes, methods, articles, or devices that include a series of elements not only include those elements, but also include other elements not explicitly listed, or inherent to such processes, methods, articles, or devices.

[0089] Although the preferred embodiments of the present application have been described, those skilled in the art can make further changes and modifications to the embodiments once they have the basic inventive concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0090] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and variations.

Claims

1. A disc harrow blade characterized by, The microstructure of the edge part of the disc harrow blade is based on martensite, and the microstructure of the core part of the disc harrow blade is based on ferrite and pearlite; The hardness of the edge part of the disc harrow blade is 47-57HRC, and the hardness of the core part of the disc harrow blade is 18-23HRC; The preparation method of the disc harrow blade comprises: The steel coil is opened and flattened, and then blanked to obtain a to-be-cut material; The to-be-cut material is cut, and then stamped to obtain a disc blank; The edge part of the disc blank is heated, and then hot stamping and quenching are performed to obtain a disc quenched blank; The disc quenched blank is shot blasted, and then baked to obtain a disc harrow blade; The width of the edge part heating is 30-150mm with the extension edge of the disc blank as zero coordinates; The temperature of the edge part heating is 860-940℃, and the holding time of the edge part heating is 1-10min; The time interval of the hot stamping and quenching to the edge part heating is ≤15s, and the pressure holding time of the hot stamping and quenching is ≥30s.

2. The disc harrow blade of claim 1, wherein, The edge part heating adopts induction heating.

3. The disc harrow blade of claim 1, wherein, The steel coil is medium-high carbon steel.

4. The disc harrow blade of claim 3 wherein, The medium-high carbon steel is one of 27MnB, 30MnB, 34MnB and 40MnB.

5. The disc harrow blade of claim 1, wherein, The temperature of the baking is 150-240℃, and the time of the baking is 15-30min.

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