High-wear-resistance and impact-resistance tool for agricultural machinery and preparation method thereof

Abstract

The invention relates to the field of cutter machining, in particular to a high-wear-resistance and impact-resistance cutter for agricultural machinery and a preparation method thereof. The high-wear-resistance and impact-resistance cutter for the agricultural machinery is prepared from molten steel, and the molten steel is prepared from, by mass, 0.15%-0.4% of C, 0.5%-1.5% of Si, 1.6%-3.5% of Mn, 0.1%-1% of Cr, 0.001%-0.01% of S, 0.001%-0.03% of P, 0.001%-0.008% of O, 0-0.5% of Mo, 0-0.1% of Nb and the balance Fe and inevitable impurities. According to the high-wear-resistance and impact-resistance tool for the agricultural machine, the hardness is larger than 60 HRC, the impact toughness is larger than 20 J / cm < 2 >, and the actual using effect is excellent.

Description

Technical Field

[0001] The present invention relates to the field of tool processing, and particularly relates to a highly wear-resistant and impact-resistant tool for agricultural machinery and a preparation method thereof. Background Art

[0002] In modern agricultural production, agricultural machinery plays a crucial role. And in various agricultural operations, efficiently cutting crops is an important task. For example, when returning crop straw to the field after harvest, a tillage knife is needed to cut the straw into pieces so that it can be evenly mixed into the soil, increasing soil fertility and improving soil structure; a straw shredding knife is used to specifically perform deep shredding on straw for better storage, transportation, or as feed raw materials, industrial raw materials, etc.; a green forage knife can cut fresh forage, silage crops, etc. into appropriate sizes for livestock to eat and digest conveniently. When these tools are working, they need to rely on the powerful kinetic energy generated by high-speed rotation to cut crops. In the actual working environment, these agricultural machinery tools usually face complex working conditions. On the one hand, they need to continuously rub against crops. The stems and fibers of crops have a certain hardness and toughness, which will cause continuous wear on the tool edge during the cutting process. Moreover, the soil in the farmland often contains various impurities, such as fine gravel, clay particles, etc. The tool will come into frequent contact with this soil during rotation, and the friction of the soil further aggravates the wear degree of the tool, resulting in the gradual dulling of the tool edge and the decline of cutting performance. On the other hand, when operating in the field, it is inevitable to encounter hard objects such as stones and tree roots. When the tool rotates at high speed and suddenly encounters these hard objects, it will instantly receive a huge impact load. This impact will not only cause direct damage to the tool edge, such as chipping and notching, but may also affect the overall structure of the tool, resulting in cracks or even fractures. The dual effects of this impact and wear pose quite high requirements for the wear resistance and impact resistance of the tool.

[0003] Currently, in the field of agricultural tool manufacturing, most commonly used tools are made of medium-high carbon steel through the process of forming, quenching + tempering. Materials such as 50Mn, 65Mn, 30MnB, 50CrV4, etc. are relatively common choices. However, such tools have obvious performance drawbacks. In terms of hardness, the hardness of general finished products is 45 - 55 HRC. Such hardness is difficult to maintain good cutting performance for a long time when facing long-term wear. In terms of room temperature impact energy, it generally does not exceed 20 J / cm 2, so when the tool is impacted, its impact resistance is weak and it is easy to be damaged. In actual use, its service life is usually only about several hundred hours. With the development of modern agriculture towards large-scale and intensive directions, the working intensity of agricultural machinery is increasing, and the working time is getting longer. The service life of the tool far cannot meet the requirements of high-intensity operations. Frequent tool replacement not only increases the agricultural production cost, but also affects the efficiency and progress of agricultural production.

[0004] In recent years, in order to improve the wear resistance of the tool, those skilled in the art have tried to add a layer of cemented carbide on the tool edge, and tungsten carbide is a relatively commonly used material. For example, CN106702304B discloses a method for preparing a wear-resistant layer of a special tool for green forage, and a wear-resistant layer is processed on the tool surface by means of cladding. When using the coating method, although the wear resistance of the tool is improved to a certain extent, it is very difficult to achieve an ideal state for the bonding strength between the coating and the tool substrate. During the actual operation process, affected by factors such as vibration, impact and temperature change, the coating is prone to peeling. Once the coating peels off, the wear resistance of the tool will be greatly reduced. The surfacing and cladding methods can make the cemented carbide combine relatively tightly with the substrate, but during the operation process, due to the high temperature effect, the tool substrate will be softened after being heated. After the substrate is softened, the overall strength and hardness of the tool will decrease, which greatly affects the stability of the tool during operation. In actual applications, various tool breakage situations often occur, which not only seriously affect the normal progress of the operation, but also may damage the agricultural machinery and increase the maintenance cost. At the same time, due to the softening of the substrate, the cemented carbide coating is more likely to fall off, further reducing the service life of the tool, resulting in a significant increase in the tool replacement frequency, bringing many inconveniences to agricultural production. Therefore, there is an urgent need for a high wear-resistant and impact-resistant tool that can be better applied to agricultural machinery tools, which is an urgent technical problem to be solved in the current field. Summary of the Invention

[0005] In order to solve the above technical problems, the first aspect of the present invention provides a preparation method of a high wear-resistant and impact-resistant tool for agricultural machinery, including:

[0006] S1. After pouring molten steel into a steel billet, the steel billet is heated, kept warm, and rolled into steel;

[0007] S2. The steel is cut into segments, then heated, kept warm, and processed to obtain a tool substrate;

[0008] S3. The surface of the tool substrate is treated, and then a wear-resistant layer is processed on the surface by means of laser cladding or surfacing, and a high wear-resistant and impact-resistant tool for agricultural machinery is obtained.

[0009] As an implementable case, the composition of the molten steel, calculated by mass percentage, includes: C 0.15-0.4%, Si 0.5-1.5%, Mn 1.6%-3.5%, Cr 0.1-1%, S 0.001-0.01%, P 0.001-0.03%, O 0.001-0.008%, Mo 0-0.5%, Nb 0-0.1%, and the balance is Fe and unavoidable impurities.

[0010] Furthermore, the composition of the molten steel includes, by mass percentage, C 0.15-0.4%, Si 0.5-1.5%, Mn 1.6%-3.5%, Cr 0.1-1%, S 0.001-0.005%, P 0.001-0.02%, O 0.001-0.008%, Mo 0-0.5%, Nb 0-0.1%, and the remainder is Fe and unavoidable impurities.

[0011] C: C (carbon) element plays a key role in regulating the properties of steel. From the perspective of its influence on the strength of steel, C is one of the important elements for improving the strength of steel. It can form interstitial solid solutions with iron atoms, produce solid solution strengthening, and effectively improve the strength of steel. However, with the increase of C content, the plastic toughness of steel will gradually decrease. This is mainly because too much C will cause changes in the crystal structure inside the steel, increase the resistance to dislocation movement, and make it difficult for the steel to produce plastic deformation when deformed by force, showing a significant brittle tendency. At the same time, the C element will also affect the phase transition temperature of the steel, significantly increasing the Ms point (the temperature at which martensite transformation begins). The increase in the Ms point means that during the cooling process, supercooled austenite is more likely to transform into martensite, increasing the tendency of steel to form martensite. The martensitic structure has high hardness and high brittleness. Excessive martensitic structure will seriously affect the toughness of the steel and destroy the strength-toughness matching of the steel.

[0012] In the present invention, in order to ensure that the steel can form a microstructure dominated by bainite and achieve a good match between strength and toughness to meet the high wear resistance and impact resistance requirements of agricultural machinery tools under complex working conditions, the C content must be strictly controlled within a range of 0.15% to 0.4%. Within this content range, it can not only ensure that the steel obtains a certain strength improvement, but also maintain good plasticity and toughness and bainite organizational morphology, providing a stable and reliable performance foundation for the tool matrix.

[0013] Si: As a common alloying element in steel, the Si (silicon) element is mainly introduced by deoxidizers during the steelmaking process. During the transformation of the microstructure of steel, Si plays a unique role, facilitating the transformation from austenite to bainite. During the transformation from austenite to bainite, Si can inhibit the diffusion of carbon, making the bainite transformation easier to occur, promoting the formation of bainite microstructure, and thereby improving the comprehensive properties of steel. Therefore, in order to fully exert the promoting effect of Si on the transformation from austenite to bainite, it is necessary to ensure that its content in steel remains above 0.5%. However, when the Si content exceeds 1.5%, it will bring obvious negative effects to the steel, significantly increasing the cold brittleness tendency of the steel. This is because excessive Si will cause changes in the crystal structure of the steel, resulting in a significant decrease in the ability of the steel to resist brittle fracture at low temperatures. During the actual use of agricultural machinery tools, different environmental temperatures are often encountered. Especially during operations in cold seasons, if the cold brittleness tendency of the steel is too large, the tool is extremely prone to brittle fracture when subjected to impact loads, seriously affecting the service life of the tool and the safety of agricultural machinery operations. Therefore, considering the advantages and disadvantages of the Si element on the properties of steel comprehensively, strictly limiting its content between 0.5% - 1.5% can ensure the promotion of the transformation from austenite to bainite while effectively avoiding the occurrence of cold brittleness problems and ensuring good performance stability of the tool substrate.

[0014] Mn: Mn (manganese) has multiple functions in steel and is of great significance for improving the properties of steel. First of all, Mn can expand the austenite phase region, making austenite stable in a wider temperature and composition range, which is of great significance for the heat treatment process and microstructure control of steel. Secondly, Mn can also significantly increase the hardenability of steel. Under the same cooling conditions, steel with a higher Mn content is more likely to obtain a uniform and dense structure, thereby improving the comprehensive properties of steel. In addition, Mn also has the function of refining grains. The refined grains can effectively improve the strength and toughness of steel, reduce the stress concentration inside the steel, and improve the mechanical property uniformity of steel.

[0015] In the present invention, considering that the C content is limited to a relatively low level to ensure the strength-toughness matching of steel, it is necessary to add sufficient Mn to improve the solid solution strengthening effect and make up for the strength loss caused by the reduction of C content. However, the Mn content is not the higher the better. When the Mn content exceeds a certain amount, it will have obvious negative effects on the hot working performance of steel. During hot working, too high a Mn content will reduce the hot plasticity of steel, and cracking is likely to occur during processing, seriously affecting the processing quality and production efficiency of steel. In the present invention, it is defined that the Mn content in the range of 1.6% - 3.5% is the optimal range. Within this content range, Mn can not only fully exert its beneficial effects such as expanding the austenite phase region, increasing hardenability, and refining grains, but also effectively avoid having an adverse impact on the hot working performance of steel.

[0016] Cr: Chromium (Cr) can increase the stability of austenite, delay the pearlite transformation, thus significantly improving the hardenability of steel. It can obtain a bainite-based microstructure even at a relatively low cooling rate, thereby enhancing the strength and toughness of the material. At the same time, Cr can lower the Ms point of the steel, reducing the tendency of austenite to transform into martensite, which is further beneficial to the formation of a bainite-based microstructure under air-cooling conditions. In addition, the addition of Cr helps to improve the strength and toughness of the steel. Through mechanisms such as solid-solution strengthening and grain refinement, it improves the overall properties of the material. It can also form and stabilize the austenite structure, ensuring that the material can obtain an ideal microstructure during hot working and subsequent processing, thereby optimizing the comprehensive properties of the tool substrate, making it have good toughness while maintaining high hardness, and meeting the usage requirements of agricultural machinery tools under complex working conditions.

[0017] S: Sulfur (S) is a harmful element in steel. Although its content in steel is usually low, it has a serious negative impact on various properties of steel. In terms of corrosion resistance, the presence of S will react with other elements in the steel to form sulfide inclusions. These inclusions will damage the integrity of the oxide film on the steel surface, reducing the corrosion resistance of the steel, making the steel more likely to corrode in humid and corrosive environments, and shortening the service life of agricultural machinery tools. In terms of hot working performance, sulfide inclusions will form low-melting eutectics during the hot working process of steel. When the steel is heated to a certain temperature, these low-melting eutectics will melt prior to the matrix, resulting in hot brittleness during the hot working process of the steel, seriously affecting the hot working quality of the steel, increasing the processing difficulty and the rejection rate. In addition, the presence of S will also significantly reduce the toughness of the steel, making the steel more likely to undergo brittle fracture when stressed, reducing the reliability and safety of agricultural machinery tools during use.

[0018] In order to minimize the adverse effects of S on the properties of steel, the present invention strictly limits the S content to less than 0.01%, specifically 0.001 - 0.005%. By strictly controlling the S content, the formation of sulfide inclusions can be effectively reduced, improving the corrosion resistance, hot working performance and toughness of the steel.

[0019] P: Phosphorus (P) is also a harmful element in steel, having many adverse effects on the properties of steel. In terms of corrosion resistance, P reduces the corrosion resistance of steel. The phosphide film formed on the surface of steel has a loose structure and cannot effectively block the erosion of external corrosive media on steel, thus accelerating the corrosion process of steel and making agricultural machinery tools more likely to suffer from corrosion damage during use. In terms of toughness, P is an interstitial solid solution element, which causes lattice distortion in steel, increases the resistance to dislocation movement, and thus significantly reduces the toughness of steel. When the P content in steel is relatively high, this effect is more obvious in a low-temperature environment, resulting in cold brittleness of steel and seriously affecting the service performance and safety of agricultural machinery tools in cold seasons or low-temperature environments.

[0020] To ensure that the steel has good corrosion resistance and toughness and meets the usage requirements of agricultural machinery tools under complex working conditions, the P content in the present invention is strictly limited to less than 0.03%, and further limited to 0.001 - 0.02%, which is more beneficial to improving the properties of steel. By strictly controlling the P content, the negative impact of P on the properties of steel can be effectively reduced, and the comprehensive properties of steel can be improved.

[0021] O: Oxygen (O) mainly exists in the form of various oxide inclusions in steel. Although the content of these inclusions is small, they have an impact on the properties of steel that cannot be ignored. In terms of hot working performance, the existence of oxide inclusions destroys the continuity and uniformity of steel. During hot working, these inclusions become stress concentration sources, causing steel to be prone to cracking during hot working, reducing the hot working performance and processing quality of steel, and increasing the rejection rate during the production process. In terms of plasticity and toughness, oxide inclusions hinder the movement of dislocations inside steel, reducing the plastic deformation ability of steel and significantly decreasing the plasticity and toughness of steel. Agricultural machinery tools need to bear impact loads and complex stress during use. If the plasticity and toughness of steel are insufficient, the tools are prone to brittle fracture and cannot meet the requirements of high wear resistance and impact resistance.

[0022] To ensure that the steel finally has good hot working performance and plasticity and toughness and meets the performance requirements of agricultural machinery tools, the O content in the present invention is strictly controlled to be 0.001 - 0.008%. By precisely controlling the deoxidation process during steelmaking, reducing the residual oxygen, and effectively reducing the content of oxide inclusions, the quality and performance stability of steel can be improved.

[0023] In addition, Mo and Nb elements can be appropriately added to further improve the performance:

[0024] Mo: Mo (molybdenum) can strongly delay the transformation of supercooled austenite to pearlite, making it easier for steel to form a bainite-based structure during the cooling process. The bainite structure has good comprehensive properties, can effectively improve the strength and toughness of steel, and meet the requirements of agricultural machinery tools for high wear resistance and impact resistance. At the same time, Mo also has a good solid solution strengthening effect. It can dissolve in ferrite, distort the ferrite lattice, increase the resistance to dislocation movement, and thus improve the strength of steel. However, the Mo element is a precious alloy element, and adding Mo will increase the production cost of steel. In addition, when the Mo content is too high, it tends to form coarse carbides that will form stress concentration points inside the steel, reduce the toughness of the steel, and have an adverse effect on the performance of agricultural machinery tools. Taking into account the effect of Mo element on improving steel performance, cost factors, and its impact on toughness, the present invention limits the Mo content to less than 0.5%, while ensuring the improvement of steel performance, effectively controlling production costs, and ensuring that the tool matrix has good comprehensive performance.

[0025] Nb: Nb (niobium) carbides will precipitate from austenite at high temperatures. These fine dispersed carbides can hinder the growth of austenite grains and play a role in grain refinement. The refined grains can effectively increase the grain boundary area, so that the steel can better disperse stress when subjected to force, thereby improving the strength and toughness of the steel. For the agricultural tool matrix material involved in the present invention, by adding the Nb element to refine the grains, the toughness of the material can be significantly improved, and the reliability and wear resistance of the tool during use can be improved. However, when the Nb content exceeds 0.1%, coarse carbides are easily formed. These coarse carbides not only fail to play a role in grain refinement, but will become defects inside the steel, reduce the plastic toughness of the steel, and affect the performance of the agricultural tool. Therefore, in order to give full play to the role of Nb element in refining grains and improving strength and toughness while avoiding its adverse effects on plasticity and toughness, the present invention controls the Nb content within the range of 0-0.1%, ensuring that the tool matrix material has good comprehensive performance and meets the high requirements of agricultural machinery tools in actual use.

[0026] As an implementable case, in the step S1, the heating temperature of the steel billet is 1100-1250°C, and the holding time is 1-4h.

[0027] The precise control of heating temperature and holding time is directly related to the performance of the final product. When the heating temperature is too high or the holding time is too long, the steel billet will overheat or burn. Overheating refers to the phenomenon that the austenite grains grow excessively during the heating process of the steel billet. At this time, the grain size increases significantly and the grain boundary area decreases, which will lead to a decrease in the comprehensive mechanical properties of the steel, such as strength, toughness and plasticity. In the subsequent use of the tool, the tool made of overheated steel is more likely to suffer from brittle fracture and cannot withstand the impact and friction during normal operation. Overburning is even more serious. It refers to the phenomenon that the austenite grains of the steel billet grow at high temperature, and the grain boundaries are oxidized or even partially melted. The organizational structure of the overburned steel billet is severely damaged, the performance deteriorates sharply, and it almost loses its use value. Even if it is made into a tool, it is very easy to have serious problems such as cracks and fractures during processing or use, which seriously affects the quality and service life of the tool.

[0028] On the contrary, if the heating temperature is too low or the holding time is too short, it will also have an adverse effect on the steel billet. When the heating temperature is too low, the atomic activity inside the steel billet is weak, and the recrystallization and homogenization process cannot be fully carried out. This makes the structure and composition inside the steel billet uneven. In the subsequent rolling process, this unevenness will be further amplified, which may lead to uneven distribution of hardness and strength of the steel, affecting the cutting performance and wear resistance of the tool. At the same time, if the holding time is too short, the stress inside the steel billet cannot be fully eliminated. During rolling, rolling defects such as cracks and folds are prone to occur in the stress concentration area. Not only does it reduce the yield rate of steel and increase production costs, but it also seriously affects the quality of the tool, reducing the reliability of the tool during use, or even scrapping it in advance. Therefore, this application limits the heating temperature to 1100-1250°C and the holding time to 1-4h to ensure that the steel can obtain good structure and performance.

[0029] As an implementable case, the heating temperature of the steel in the S2 step is 900-1050°C, and the insulation time is 5-30 minutes.

[0030] As an implementable case, in the step S2, the processing includes one of hot extrusion, hot calcination or hot rolling, and can be processed into a corresponding required tool shape according to actual agricultural machinery needs.

[0031] As an implementable example, in the S3 step, the surface treatment step includes sandblasting or pickling.

[0032] Furthermore, in the pickling process, the acid used for pickling includes hydrochloric acid or sulfuric acid with a mass concentration of 10-20wt%.

[0033] Furthermore, the material of the wear-resistant layer includes: nickel powder, tungsten carbide or corundum.

[0034] Furthermore, the powder for sandblasting includes nickel powder, tungsten carbide powder or emery, and the end point of sandblasting is that the surface roughness reaches Ra3.2 - Ra6.3μm.

[0035] Furthermore, the wear-resistant layer is made of tungsten carbide with a particle size of 100 - 300 mesh.

[0036] As an implementable case, in the laser cladding, the laser power is 1.5 - 3.5kW, the laser scanning speed is 100 - 1000mm / s, the powder feeding rate is 10 - 30g / min, and the flow rate of the shielding gas is 5 - 15L / min.

[0037] The second aspect of the present invention provides an agricultural machinery high wear-resistant and impact-resistant tool prepared by the preparation method of the above-mentioned agricultural machinery high wear-resistant and impact-resistant tool.

[0038] Beneficial effects

[0039] (1) The tool in the present invention is an air-cooled bainitic steel. By reasonably controlling the contents of alloying elements such as C, Mn, Si, and Cr, the matrix has high toughness while having high hardness. This matrix structure with strong toughness matching is stable. During the agricultural machinery operation, when facing the friction of crops and soil and the impact load brought by hard objects such as stones and tree roots, it can effectively disperse stress, reduce the generation and propagation of cracks, greatly reduce the risk of tool damage, and extend the overall service life of the tool.

[0040] (2) The present application uses laser cladding or surfacing to cover the tungsten carbide wear-resistant layer, so that the hardness of the cutting edge reaches above 65HRC. The ultra-high hardness endows the cutting edge with excellent wear resistance. During the process of cutting crops at high speed, it can effectively resist wear, reduce the loss of the cutting edge, significantly improve the wear-resistant life of the tool, reduce the replacement frequency of the tool, and enhance the continuity and efficiency of agricultural machinery operation.

[0041] (3) In the present application, accurately controlling the heating temperature in the S1 step at 1100 - 1250°C and the holding time at 1 - 4h can avoid overheating and overburning of the steel billet, prevent excessive growth of austenite grains and oxidation and melting of grain boundaries, and ensure the comprehensive mechanical properties such as strength, toughness, and plasticity of the steel.

[0042] (4) The service life of traditional tools is generally about several hundred hours, which is difficult to meet the requirements of high-intensity operation of agricultural machinery. However, the tool in the present application, with its high wear resistance, impact resistance, and long life characteristics, can operate stably in the long-term and high-load agricultural machinery operation environment, reduce the downtime and maintenance costs caused by tool damage, improve the operation efficiency of agricultural machinery, and better meet the operation requirements of modern agriculture with high intensity and high efficiency.

[0043] (5) The cutting tools provided by this application are applicable to various agricultural implements with high reliability requirements. Whether it is a rotary tillage knife, a straw shredding knife, or a forage harvester knife, etc., they can meet the high wear resistance and impact resistance requirements during crop cutting, providing excellent cutting tool options for different types of agricultural machinery and having broad application prospects. Description of the Drawings

[0044] Figure 1 Appearance of the high wear-resistant and impact-resistant cutting tool for agricultural machinery prepared in Example 1.

[0045] Figure 2 Appearance of the high wear-resistant and impact-resistant cutting tool for agricultural machinery prepared in Example 2. Detailed Description of the Invention

[0046] Example 1

[0047] In the first aspect of this example, a preparation method of a high wear-resistant and impact-resistant cutting tool for agricultural machinery is provided, specifically as follows:

[0048] S1. After casting the molten steel into a steel billet, heat the steel billet to 1200 °C, hold for 3 h, and roll it into steel. The composition of the molten steel is as follows by mass percentage: C 0.2%, Si 1.2%, Mn 2.5%, Cr 0.6%, S 0.005%, P 0.01%, O 0.005%, Mo 0.2%, Nb 0.1%, and the balance is Fe and inevitable impurities;

[0049] S2. Cut the steel into segments, then heat to 1000 °C, hold for 20 min, and perform hot roll forming to obtain the cutting tool substrate;

[0050] S3. Pickle the cutting tool substrate with hydrochloric acid with a mass concentration of 10 wt%, and then process a wear-resistant layer on the surface by laser cladding to obtain the high wear-resistant and impact-resistant cutting tool for agricultural machinery. The wear-resistant layer is made of tungsten carbide with a particle size of 200 mesh. In the laser cladding process, the laser power is 3.5 kW, the laser scanning speed is 1000 mm / s, the powder feeding rate is 20 g / min, and the flow rate of the shielding gas argon is 10 L / min.

[0051] In the second aspect of this example, a high wear-resistant and impact-resistant cutting tool for agricultural machinery prepared by the above preparation method is provided. The product schematic diagram is as Figure 1 shown.

[0052] Example 2

[0053] In the first aspect of this example, a preparation method of a high wear-resistant and impact-resistant cutting tool for agricultural machinery is provided, specifically as follows:

[0054] S1. After casting the molten steel into steel billets, heat the steel billets to 1200 °C, hold for 3 h, and roll them into steel products. The composition of the molten steel is as follows by mass percentage: C 0.3%, Si 1.2%, Mn 3.5%, Cr 0.6%, S 0.005%, P 0.01%, O 0.005%, and the balance is Fe and inevitable impurities.

[0055] S2. Cut the steel products into segments, then heat them to 1000 °C, hold for 20 min, and perform hot roll pressing to obtain the tool matrix.

[0056] S3. Spray diamond sand on the tool matrix until the surface roughness reaches Ra 6 μm at the end of sandblasting. Then, use laser cladding to process a wear-resistant layer on the surface to obtain a high wear-resistant and impact-resistant tool for agricultural machinery. The wear-resistant layer is made of tungsten carbide with a particle size of 200 mesh. In the laser cladding, the laser power is 3.5 kW, the laser scanning speed is 1000 mm / s, the powder feeding rate is 20 g / min, and the flow rate of the shielding gas argon is 10 L / min.

[0057] In the second aspect of this example, a high wear-resistant and impact-resistant tool for agricultural machinery prepared by the above preparation method is provided. The product schematic diagram is as Figure 2 shown.

[0058] Comparative Example 1

[0059] The specific implementation of this example is the same as that of Example 1, except that in the S1 step, the heating temperature of the steel billet is 900 °C and the holding time is 45 min.

[0060] Comparative Example 2

[0061] The specific implementation of this example is the same as that of Example 1, except that the composition of the molten steel is as follows by mass percentage: C 0.2%, Si 1.2%, Mn 1.2%, Cr 0.6%, S 0.005%, P 0.01%, O 0.005%, Mo 0.2%, Nb 0.1%, and the balance is Fe and inevitable impurities.

[0062] Comparative Example 3

[0063] The specific implementation of this example is the same as that of Example 1, except that the composition of the molten steel is as follows by mass percentage: C 0.2%, Si 1.2%, Mn 4%, Cr 0.6%, S 0.005%, P 0.01%, O 0.005%, Mo 0.2%, Nb 0.1%, and the balance is Fe and inevitable impurities.

[0064] Comparative Example 4

[0065] The specific implementation of this example is the same as that of Example 1, except that the composition of the molten steel is as follows by mass percentage: C 0.2%, Si 1.2%, Mn 3.5%, Cr 0.6%, S 0.02%, P 0.01%, O 0.01%, Mo 0.2%, Nb 0.1%, and the balance is Fe and unavoidable impurities.

[0066] Performance test

[0067] Test objects: The tools described in Examples 1-2 and Comparative Examples 1-4.

[0068] Test items:

[0069] 1. Hardness; refer to GB / T 230.1-2018 "Metallic materials - Rockwell hardness test - Part 1: Test method");

[0070] 2. Impact toughness; refer to GB / T 229-2007 "Metallic materials - Charpy pendulum impact test method"; The experimental results are shown in Table 1 for details.

[0071] Table 1

[0072] Serial number Hardness (HRC) <![CDATA[Impact toughness (J / cm 2 )]]> Example 1 65 22 Example 2 63 21 Comparative example 1 55 18 Comparative example 2 57 19 Comparative example 3 64 18 Comparative example 4 58 19

[0073] It can be seen from the experimental results in Table 1 that the hardness of the high wear-resistant and impact-resistant tool for agricultural machinery provided by the present invention is greater than 60 HRC, and the impact toughness is greater than 20 J / cm 2 ; However, the change of the processing parameters of the steel billet in Comparative Example 1 and the change of the molten steel element content in Comparative Examples 2-4 will affect the hardness and impact toughness, and further affect the service life of the tool.

Claims

1. A preparation method of a highly wear-resistant and impact-resistant tool for agricultural machinery, characterized in that, It includes the following steps: S1. After casting molten steel into a steel billet, heat the steel billet, keep it warm, and roll it into steel products; S2. Cut the steel products into segments, then heat, keep warm, and process them to obtain a tool substrate; S3. Treat the surface of the tool substrate, and then process a wear-resistant layer on the surface by laser cladding or surfacing to obtain a high-wear-resistant and impact-resistant tool for agricultural machinery; The composition of the molten steel, by mass percentage, includes C 0.15 - 0.4%, Si 0.5 - 1.5%, Mn 1.6 - 3.5%, Cr 0.1 - 1%, S 0.001 - 0.01%, P 0.001 - 0.03%, O 0.001 - 0.008%, Mo 0 - 0.5%, Nb 0 - 0.1%, and the balance is Fe and unavoidable impurities.

2. The preparation method of the high wear-resistant and impact-resistant tool for agricultural machinery according to claim 1, characterized in that, The composition of the molten steel, by mass percentage, includes C 0.15 - 0.4%, Si 0.5 - 1.5%, Mn 1.6 - 3.5%, Cr 0.1 - 1%, S 0.001 - 0.005%, P 0.001 - 0.02%, O 0.001 - 0.008%, Mo 0 - 0.5%, Nb 0 - 0.1%, and the balance is Fe and unavoidable impurities.

3. The preparation method of the high wear-resistant and impact-resistant tool for agricultural machinery according to claim 1, characterized in that, In the step S1, the heating temperature for heating the steel billet is 1100 - 1250 °C, and the heat preservation time is 1 - 4 h.

4. The preparation method of the high wear-resistant and impact-resistant tool for agricultural machinery according to claim 1, characterized in that, In the step S2, the heating temperature for heating the steel products is 900 - 1050 °C, and the heat preservation time is 5 - 30 min.

5. The preparation method of the high wear-resistant and impact-resistant tool for agricultural machinery according to claim 1, characterized in that, In the step S2, the processing includes one of hot extrusion, hot forging, or hot roll pressing.

6. The preparation method of the high wear-resistant and impact-resistant tool for agricultural machinery according to claim 1, characterized in that, In the step S3, the surface treatment includes sandblasting or pickling.

7. The preparation method of the high wear-resistant and impact-resistant tool for agricultural machinery according to claim 6, characterized in that, The powder for sandblasting includes nickel powder, tungsten carbide powder, or emery, and the end point of sandblasting is that the surface roughness reaches Ra3.2 - Ra6.3 μm.

8. The preparation method of the high wear-resistant and impact-resistant tool for agricultural machinery according to any one of claims 1-7, characterized in that, The material of the wear-resistant layer includes one of nickel powder, tungsten carbide, or emery.

9. The preparation method of the high wear-resistant and impact-resistant tool for agricultural machinery according to claim 1, characterized in that, In the laser cladding, the laser power is 1.5 - 3.5 kW, the laser scanning speed is 100 - 1000 mm / s, the powder feeding rate is 10 - 30 g / min, and the flow rate of the protective gas is 5 - 15 L / min.

10. A high-wear-resistant and impact-resistant tool for agricultural machinery prepared by the preparation method of the high-wear-resistant and impact-resistant tool for agricultural machinery according to any one of claims 1 - 9.

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