Low-yield-strength impact-resistant steel for rotary blade of agricultural machine and manufacturing method of low-yield-strength impact-resistant steel

Abstract

The invention relates to the technical field of steel for agricultural machinery, in particular to low-yield-strength impact-resistant steel for a rotary blade of agricultural machinery and a manufacturing method of the low-yield-strength impact-resistant steel. Cr, Nb, B and Re are used for alloying, meanwhile, the technological parameters such as casting blank heating, rough and finish rolling descaling pressure, the rolling temperature, the reduction rate, the coiling temperature and the cooling speed are controlled, and the prepared steel for the agricultural machine rotary blade is low in yield strength and good in punch forming performance; the yield strength of the agricultural machine rotary blade part produced by using the composite material is 300-400MPa, the tensile strength is 700-800MPa, and the ductility is greater than or equal to 18%; after heat treatment, the yield strength is 1400 MPa or above, the tensile strength is 1900 MPa or above, the ductility is larger than or equal to 10%, the impact energy AKv at the temperature of 20 DEG C is larger than or equal to 25 J, the hardness is 53 HRC or above, the wear-resisting life is prolonged by two times or above, and the service life is obviously prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural machinery steel, and in particular to a low-yield strength impact-resistant agricultural machinery rotary tiller steel and a manufacturing method thereof. Background Art

[0002] The rotary tiller blade of agricultural machinery is a key component of agricultural tillage machinery, and its service life directly affects the quality and efficiency of agricultural machinery tillage operations. The rotary tiller blade has a complex shape, is difficult to process and is easy to break. It is severely worn and easy to break when in contact with hard soil such as sand and gravel during operation. The yield strength of the hot-rolled plate of 60Si2Mn material used for the original processing and manufacturing of rotary tillers is above 600MPa, the yield strength ratio is above 65%, and the tensile strength is above 900MPa. The oil quenching + tempering treatment is inefficient and not environmentally friendly. The hardness of the heat-treated finished product is 45-50HRC, the tensile strength is 1300-1500MPa, and the impact energy AKv at 20℃ is less than 10J. The hot-rolled plate has a high yield strength and is difficult to process and form. After heat treatment, it is brittle, has poor toughness, is easy to break, has low hardness and poor wear resistance, is frequently replaced, and has low operating efficiency. It is difficult to meet the large-scale, complex, high-speed development and continuous and efficient operation requirements of fully automatic agricultural machinery. On the other hand, with the continuous improvement of environmental protection requirements, water quenching is the development direction of the heat treatment industry. The mismatch in materials, manufacturing processes and component performance is the main reason restricting the lagging development of agricultural machinery tools such as rotary tillers in my country. Summary of the invention

[0003] In view of the problems that the existing steel for rotary tiller blades mentioned above has high yield strength but poor formability of hot-rolled plates, low hardness and insufficient wear resistance after heat treatment, poor impact toughness and easy breakage, environmentally unfriendly heat treatment process, low efficiency and inability to meet the use requirements of complex-shaped agricultural machinery parts such as rotary tillers, the present invention provides a low yield strength and impact-resistant steel for agricultural machinery rotary tiller blades and a manufacturing method thereof.

[0004] In order to achieve the above object, the technical solution of the present invention is as follows:

[0005] On one hand, the present invention provides a low-yield strength impact-resistant steel for agricultural machinery rotary tiller blades. The chemical composition of the steel is as follows by weight percentage: C 0.30%-0.50%, Si 0.01%-0.3%, Mn 0.5%-1.5%, B0.0005%-0.005%, Cr 0.1%-0.8%, Nb 0.01%-0.5%, Ti 0.01%-0.1%, Al0.01%-0.1%, Re0.001%-0.2%, N 0.0010%-0.010%, Ca 0.0005%-0.02%, 0.01%≤Ti+Al≤0.15%, 1≤Nb / Ti≤10, P≤0.020%, S≤0.020%, and the balance is Fe and unavoidable impurities.

[0006] The following is a detailed description of the mechanism of action of each alloy component of the agricultural machinery rotary tiller steel of the present invention:

[0007] C: C is the main solid solution strengthening element in steel, and in the present invention, sufficient C and Re are required to generate rare earth carbides, inhibit surface oxidation and decarburization, and improve hardness and hardness uniformity. If the C content is lower than 0.30%, it is difficult to ensure the hardness of the steel plate after heat treatment. On the other hand, if the C content is higher than 0.50%, the strength is too high, which deteriorates the toughness and plasticity of the steel after heat treatment, reduces impact toughness, and is easy to break. Therefore, the C content should be controlled at 0.30% to 0.50%.

[0008] Mn: Mn is relatively cheap and is a good deoxidizer and desulfurizer. It is an essential element to ensure the strength and toughness of steel. Manganese and iron can infinitely dissolve to form a solid solution, which improves hardness and strength and has relatively little effect on plasticity. Mn combines with S to form MnS, avoiding the formation of FeS at the grain boundaries and causing hot cracks that affect the hot formability of steel. At the same time, Mn is also a good deoxidizer and increases hardenability. A low Mn content in steel cannot meet the requirements of high strength and hardness. A high Mn content will cause serious segregation, affecting welding performance and formability, and increasing production costs. Therefore, considering factors such as cost and performance requirements, the Mn content should be controlled between 0.50% and 1.5%.

[0009] Si: Si is one of the common elements in steel. It is used as a reducing agent and deoxidizer in the steelmaking process. Si is a ferrite-forming element, not a carbide-forming element. Si solid dissolves in ferrite to improve hardenability and tempering resistance, strength and hardness, wear resistance, elastic limit, yield strength and yield strength ratio, fatigue strength, and extend the service life of steel. When the Si content exceeds 0.3%, the steel surface will be decarburized and oxidized, which seriously affects the fatigue performance.

[0010] B: Boron solid solution in steel can significantly improve hardenability and hardenability. 0.001% to 0.003% boron is equivalent to 0.6% manganese, 0.7% chromium, 0.5% molybdenum and 1.5% nickel, so a very small amount of boron can save a large amount of precious alloy elements. After adding B in the present invention, the steel plate with a carbon content of less than 0.4% can obtain a full martensitic structure after oil quenching, which significantly improves the hardenability of the steel. On the other hand, the present invention effectively controls the content of solid solution B in steel by limiting the relationship between the contents of the three elements Nb, Ti and Al, avoids the phenomenon of boron embrittlement, and gives full play to the beneficial effects of boron.

[0011] Cr: Chromium is a medium-strong carbide forming element. After adding Cr in the present invention, it forms a composite carbide with Re, inhibits microsegregation, and reduces banding. Chromium can also increase the temperature of A3 and A1, and the GS line moves to the upper left. It slows down the decomposition of A and improves hardenability; improves the oxidation resistance and corrosion resistance of steel, improves tempering stability, high hardness, and improves wear resistance.

[0012] Nb: fine grain strengthening element, high temperature solid solution improves hardenability, 1≤Nb / Ti≤10 ensures the formation of dispersed fine NbN particles ≤50nm in the steel and the formation of composite N compounds with N, N and Re, high melting point, high hardness, strong wear resistance, while adding Nb helps to improve the impact resistance after heat treatment and avoid cracking during operation. 1≤Nb / Ti does not form square TiN particles, Nb / Ti≤10 allows Ti and Al to effectively control the solid solution B content in the steel, avoid boron embrittlement, give full play to the beneficial role of boron, inhibit microsegregation, uniform organization, and reduce banding. 1≤Nb / Ti≤10, improve impact resistance and fatigue life.

[0013] Ti: The main function of Ti in the present invention is a deoxidizer. It also precipitates and strengthens the steel, improves hardenability, and increases the strength of the steel while maintaining good plasticity and toughness.

[0014] Al: Al is used as a deoxidizer during steelmaking to refine grains, inhibit steel aging, improve steel toughness at low temperatures, and especially reduce the brittle transition temperature of steel. Al is a non-carbide forming element that can improve steel's oxidation resistance, inhibit surface oxidation and decarburization, and improve surface quality.

[0015] 0.01≤Ti+Al≤0.15: The three elements Nb+Ti+Al work together to effectively control the solid solution B content in the steel, avoid boron embrittlement, give full play to the beneficial role of boron, inhibit microsegregation, uniform organization, reduce banding, and improve impact resistance and fatigue performance. When Ti+Al is less than 0.01%, the above effect is not obvious. When Ti+Al is higher than 0.15%, coarse inclusions are formed in the steel, and the formation of fine dispersed NbC particles is not utilized, which affects the impact resistance and fatigue performance.

[0016] N: Generally, N is considered to be a harmful element. The lower the N content in steel, the better. The present invention adopts a composition design containing N. During refining, N with a content of more than 0.001% is introduced to form fine carbide particles of ≤50nm with Nb and C, thereby inhibiting microsegregation, making the structure uniform, and reducing banding. If the N content exceeds 0.01%, it will form a BN phase with B, resulting in boron brittleness and reducing toughness and plasticity.

[0017] P, S: P and S are both unavoidable harmful impurities in steel. Their presence will seriously deteriorate the toughness of steel, so measures should be taken to reduce the P and S content in steel as much as possible. The P content of the present invention is limited to P≤0.020%. The maximum S content is limited to 0.010% to reduce the formation of MnS.

[0018] Re: As a microalloying element, Re improves strength by solid solution. Re forms composite carbides with Cr and Nb, which helps pearlite spheroidization and improves tensile strength, thereby reducing the yield strength ratio, while inhibiting microsegregation and reducing banding, not exceeding level 2.0. Re can also refine grains, improve molten steel fluidity, improve steel surface finish, eliminate organizational anisotropy, improve molten steel purity, and increase elongation after heat treatment to more than 10%, impact performance to more than 25J, and hardness to more than 53HRC and uniform.

[0019] Ca: Ca, as a microalloying element, forms complex carbides with Cr and V, inhibits microsegregation, reduces banding, promotes carbide nucleation and spheroidization, and improves impact resistance and fatigue properties.

[0020] In the above technical solution, further, the yield strength of the steel is 300-400MPa, and the tensile strength is 700-800MPa; the yield strength after heat treatment is above 1400MPa, the tensile strength is above 1900MPa, the elongation is ≥10%, the impact energy AKv at 20°C is ≥25J, and the surface hardness is above 53HRC.

[0021] Another aspect of the present invention provides a method for manufacturing the above-mentioned agricultural machinery rotary tiller steel, the method comprising the following steps:

[0022] (1) Smelting and continuous casting: The C content of the molten steel before tapping the converter is 0.25% to 0.45%. The molten steel enters the LF electric furnace for refining. After the sulfur content is ≤ 0.020%, alloying is performed. At the same time, N is introduced to adjust the N content of the molten steel to 0.001% to 0.010%, and continuous casting is performed to obtain a continuous casting billet.

[0023] (2) Ingot treatment: Ingot is slowly cooled down after it leaves the production line, kept at 600-700℃ for more than 90h, and then hot-transferred and heated into a walking beam heating furnace. The preheating section is at 500-600℃, and the holding time is more than 60min. The first heating section is at 900-1100℃, and the holding time is more than 60min. The second heating section is at 1200-1350℃, and the total time in the furnace is 3-4h.

[0024] (3) Rolling: High-pressure water descaling is used before rough and finish rolling. Rough rolling adopts 3-5 continuous rolling, with the first-pass reduction rate of 20%-25%, the rolling temperature of 1150-1250°C, and the temperature difference of the whole length of the steel strip is ≤20°C. Finishing rolling adopts 5-7 continuous rolling, with the first-pass reduction rate of 20%-25%, the final rolling temperature of 950-1150°C, and the temperature difference of the whole length of the steel strip is ≤10°C.

[0025] (4) Cooling: After leaving the finishing mill, the steel plate enters the layer cooling, cools to 500-600℃ and coils, then slowly cools to below 300℃ and air cools to room temperature.

[0026] In the above technical solution, further, in step (1), the molten steel is cast by a vertical bending arc continuous casting machine, and the arc radius of the vertical bending continuous casting machine is not less than 5m;

[0027] Continuous casting adopts light pressure and crystallizer electromagnetic stirring, the electromagnetic stirring current is 500-700A, the frequency is 2.2-2.9Hz, the dynamic water volume of the crystallizer is 80-160L / min, the crystallizer protection slag is used for casting, the crystallizer liquid level is 750-850mm, the superheat is 20-25℃, the continuous casting speed is 0.8-1.2m / min, and the secondary cooling water volume is 0.15-0.25L / kg;

[0028] The thickness of the continuous casting billet is 170-250 mm.

[0029] In the above technical solution, further, in step (3), the high-pressure water pressure is not less than 30 MPa;

[0030] During the finishing rolling process, edge heating devices are used on both sides of the steel plate, with a compensation temperature of 40 to 50°C and a width of 40 to 50 mm.

[0031] In the above technical solution, further, in step (4), the cooling rate of the layer cooling is 10-25°C / s, and the cooling rate difference in the bandwidth direction at the same position is ≤1°C / s;

[0032] The slow cooling rate is 15-25℃ / h.

[0033] The present invention also provides a heat treatment method for an agricultural machinery rotary blade produced using the above-mentioned agricultural machinery rotary blade steel, which comprises processing the agricultural machinery rotary blade steel into a rotary blade blank, induction heating to 850-900°C, hot stamping forming, cooling to 200-250°C with a coolant containing 60%-90% water for 5-10 minutes, and then air cooling to room temperature.

[0034] The invention adopts converter smelting and LF electric furnace refining, and does not need RH vacuum treatment; before the converter tapping, the molten steel has a C content of 0.25%≤C≤0.40%, so as to ensure that the carbon content in the ingot after the fine steel continuous casting is uniform and has no macro segregation; LF electric furnace refining is adopted, and after the refined sulfur content is ≤0.010%, Re and other alloys are added, and nitrogen is passed at the same time to adjust the N content of the molten steel, change the composition, quantity and form of non-metallic inclusions, accelerate the flow of molten steel, promote the inclusions to float fully, improve the purity of steel, various non-metallic inclusions in the finished steel do not exceed level 1.5, and improve the surface finish of the steel and eliminate the anisotropy of the structure; the continuous casting adopts light pressure reduction and crystallizer electric Magnetic stirring, electromagnetic stirring current 500 ~ 700A, frequency 2.2 ~ 2.9Hz; dynamic water volume of crystallizer 80 ~ 160L / min, use crystallizer protection slag for pouring, crystallizer liquid level 750 ~ 850mm, superheat 20 ~ 25 ℃, control inclusions and segregation, while continuous casting speed 0.8 ~ 1.2m / min, secondary cooling water volume 0.15 ~ 0.25L / kg, to ensure that the surface temperature deviation of the ingot is no more than 10 ℃, the cooling rate of the ingot is uniform, the organization is uniform, the strength difference of the same roll of strip steel after rolling is ≤ 20MPa, the hardness difference of the same roll is ≤ 3HRB, the equiaxed crystal rate is more than 50%, and the liquid micro-segregation of the alloy at the end of the columnar crystal is controlled.

[0035] The billet is slowly cooled off the line and kept at 600-700℃ for more than 90h to reduce the temperature difference on the billet surface and alleviate microsegregation. The heating furnace adopts a weak oxidizing atmosphere (air excess coefficient 1.02-1.1, air-fuel ratio 2.0-2.2), the preheating section temperature is 500-600℃, the holding time is more than 60min, the first heating section temperature is 900-1100℃, the holding time is more than 60min, the second heating section temperature is 1200-1350℃, and the total time in the furnace is 3-4h to ensure the surface quality of the billet and avoid oxidation and decarburization.

[0036] High-pressure water is used for descaling before rough and fine rolling, and the pressure of high-pressure water is not less than 30MPa to ensure the surface quality of the steel plate. Rough rolling adopts 3-5 continuous rolling, the first pass reduction rate is 20%-25%, and the rolling temperature is 1150-1250℃, which provides nucleation power for the precipitation of various carbides and nitrides. The temperature difference of the full length of the steel strip is ≤20℃, and the microstructure and performance are uniform. Finishing rolling adopts 5-7 continuous rolling, the first pass reduction rate is 20%-25%, and the final rolling temperature is 950-1150℃, which helps to increase the spheroidization rate after heating and reduce the banding, which does not exceed 2.0 grade. Both finishing and rough rolling use high temperature and small reduction, which is helpful to obtain a coarser pearlite and ferrite mixed structure after subsequent cooling and reduce the yield strength. In particular, edge heating devices are used on both sides of the steel plate, with a compensation temperature of 40-50°C, a width of 40-50mm, a strip rolling temperature difference of ≤10°C, uniform organizational properties, strip thickness fluctuation within ±0.20mm, convexity ≤40μm, tensile strength difference of the same roll ≤20MPa, and hardness difference of the same roll ≤3HRB.

[0037] After the steel plate leaves the finishing mill, it enters the layer cooling, the cooling rate is 10-25℃ / s, the cooling rate difference in the bandwidth direction at the same length position is ≤1℃ / s, to ensure the uniform performance of the same plate structure, the strength difference is ≤20MPa, and the hardness difference is ≤3HRB. Cooling to 500-600℃ for coiling, cooling to below 300℃ at a cooling rate of 15-25℃ / h, is conducive to carbide nucleation, and a uniform spheroidized pearlite, lamellar pearlite and ferrite mixed structure is obtained, the diameter of the spheroidized pearlite is less than 0.2μm, the spheroidization rate is more than 50%, the cooling rate exceeds 25℃ / h, it is easy to form lamellar pearlite, and the cooling rate is lower than 15℃ / h, the spheroidized pearlite is easy to grow, and the toughness and plasticity are poor.

[0038] The blank of the part is induction heated to 880-950℃, hot stamped, quenched with a coolant containing 60%-90% water, cooled to 200-250℃ and kept warm for 5-10 minutes, and then air-cooled to room temperature to obtain a fine lath martensite structure, which has excellent performance without tempering. The yield strength is above 1400MPa, the tensile strength is above 1900MPa, the elongation is ≥10%, the impact energy AKv at 20℃ is ≥25J, and the surface hardness is above 53HRC.

[0039] The beneficial effects of the present invention are:

[0040] The present invention utilizes alloying elements such as Cr, Nb, B, Re, and controls manufacturing process parameters at the same time to obtain a uniform and fine mixed structure of spheroidized pearlite, lamellar pearlite and ferrite. The diameter of the spheroidized pearlite is less than 0.2 μm, the spheroidization rate is more than 50%, the banding does not exceed grade 2.0, the yield strength of the steel is 300-400 MPa, the tensile strength is 700-800 MPa, the yield strength ratio is less than 60%, the elongation is greater than 18%, and the hardness is 85-95 HRB.

[0041] The present invention controls the thickness fluctuation of the strip steel within ±0.20 mm, the convexity ≤40 μm, the difference in tensile strength of the same roll ≤20 MPa, and the hardness difference of the same roll ≤3 HRB through a controlled rolling and controlled cooling process.

[0042] The steel for agricultural machinery rotary tiller blades produced by the present invention has low yield strength and good stamping formability; the agricultural machinery rotary tiller blades produced by the present invention are quenched with a coolant containing 60% to 90% water to obtain a uniform fine lath martensitic structure, the longest martensitic lath does not exceed 25 μm, no tempering treatment is required, the yield strength is above 1400 MPa, the tensile strength is above 1900 MPa, the elongation is ≥10%, the impact energy AKv at 20°C is ≥25J, the hardness is above 53HRC, the wear-resistant life is extended by more than 2 times, and the service life is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is the metallographic structure diagram of the hot-rolled steel plate according to Example 1 of the present invention. DETAILED DESCRIPTION

[0044] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0045] The chemical composition of the steel in Examples 1-15 and Comparative Example 1 is shown in Table 1; the smelting and continuous casting process parameters are shown in Table 2; the ingot processing process parameters are shown in Table 3; the rolling process parameters are shown in Table 4; the cooling process parameters are shown in Table 5; the structure and properties of the steel are shown in Table 6; the performance of the parts after heat treatment is shown in Table 7.

[0046] Table 1 Chemical composition of steel in Examples 1-15 and Comparative Example 1, %

[0047]

[0048]

[0049] Table 2 Smelting and continuous casting process parameters in Examples 1-15 and Comparative Example 1

[0050]

[0051] Table 3 Process parameters of casting process in Examples 1-15 and Comparative Example 1

[0052]

[0053] Table 4 Rolling process parameters in Examples 1-15 and Comparative Example 1

[0054]

[0055]

[0056] Table 5 Cooling process parameters in Examples 1-15 and Comparative Example 1

[0057]

[0058]

[0059] Table 6 Structure and properties of steel in Examples 1-15 and Comparative Example 1

[0060]

[0061] Table 7 Performance of parts after heat treatment in Examples 1-15 and Comparative Example 1

[0062]

[0063]

[0064] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the implementation methods. The protection scope of the present invention shall be subject to the scope defined in the claims. Other different forms of changes or modifications may be made based on the above description. Obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A steel for agricultural machinery rotary tiller with low yield strength and impact resistance, characterized in that: The chemical composition of the steel is as follows by weight percentage: C 0.30%-0.50%, Si 0.01%-0.3%, Mn 0.5%-1.5%, B0.0005%-0.005%, Cr 0.1%-0.8%, Nb 0.01%-0.5%, Ti 0.01%-0.1%, Al0.01%-0.1%, Re0.001%-0.2%, N 0.0010%-0.010%, Ca 0.0005%-0.02%, 0.01%≤Ti+Al≤0.15%, 1≤Nb / Ti≤10, P≤0.020%, S≤0.020%, and the balance is Fe and unavoidable impurities.

2. The agricultural machinery rotary tiller steel according to claim 1, characterized in that: The yield strength of the steel is 300-400MPa, and the tensile strength is 700-800MPa; after heat treatment, the yield strength is above 1400MPa, the tensile strength is above 1900MPa, the elongation is ≥10%, the impact energy AKv at 20°C is ≥25J, and the surface hardness is above 53HRC.

3. A method for manufacturing steel for agricultural machinery rotary tiller blade according to any one of claims 1 to 2, characterized in that: The method comprises the following steps: (1) Smelting and continuous casting: The C content of the molten steel before tapping the converter is 0.25% to 0.4%. The molten steel enters the LF electric furnace for refining. After the sulfur content is ≤ 0.020%, alloying is performed. At the same time, N is introduced to adjust the N content of the molten steel to 0.001% to 0.010%, and continuous casting is performed to obtain a continuous casting billet. (2) Ingot treatment: Ingot is slowly cooled down after it leaves the production line, kept at 600-700℃ for more than 90h, then hot-transferred and loaded into the heating furnace for heating, with the preheating section at 500-600℃ and the holding time at more than 60min, the first heating section at 900-1100℃ and the holding time at more than 60min, the second heating section at 1200-1350℃, and the total time in the furnace at 3-4h; (3) Rolling: High-pressure water descaling is used before rough and finish rolling. Rough rolling adopts 3-5 continuous rolling, with the first-pass reduction rate of 20%-25%, the rolling temperature of 1150-1250°C, and the temperature difference of the whole length of the steel strip is ≤20°C. Finishing rolling adopts 5-7 continuous rolling, with the first-pass reduction rate of 20%-25%, the final rolling temperature of 950-1150°C, and the temperature difference of the whole length of the steel strip is ≤10°C. (4) Cooling: After leaving the finishing mill, the steel plate enters the layer cooling, cools to 500-600℃ and coils, then slowly cools to below 300℃ and air cools to room temperature.

4. The manufacturing method according to claim 3, characterized in that: In step (1), the molten steel is cast by a vertical bending arc continuous casting machine, and the arc radius of the vertical bending continuous casting machine is not less than 5m; Continuous casting adopts light pressure and crystallizer electromagnetic stirring, the electromagnetic stirring current is 500-700A, the frequency is 2.2-2.9Hz, the dynamic water volume of the crystallizer is 80-160L / min, the crystallizer protection slag is used for casting, the crystallizer liquid level is 750-850mm, the superheat is 20-25℃, the continuous casting speed is 0.8-1.2m / min, and the secondary cooling water volume is 0.15-0.25L / kg; The thickness of the continuous casting billet is 170-250 mm.

5. The manufacturing method according to claim 3, characterized in that: In step (3), the high-pressure water pressure is not less than 30 MPa; During the finishing rolling process, edge heating devices are used on both sides of the steel plate, with a compensation temperature of 40 to 50°C and a width of 40 to 50 mm.

6. The manufacturing method according to claim 3, characterized in that: In step (4), the cooling rate of the layer cooling is 10-25°C / s, and the cooling rate difference in the bandwidth direction at the same position is ≤1°C / s; The slow cooling rate is 15-25℃ / h.

7. A heat treatment method for agricultural machinery rotary tiller blades produced using the agricultural machinery rotary tiller blade steel according to any one of claims 1 to 2 or the agricultural machinery rotary tiller blade steel produced by the manufacturing method according to any one of claims 3 to 6, characterized in that: The agricultural machinery rotary blade steel is processed into a rotary blade blank, induction heated to 850-900° C., hot stamped, cooled to 200-250° C. with a coolant containing 60%-90% water for 5-10 minutes, and then air cooled to room temperature.

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