Multiphase composite reinforced alloy for quick-wear parts of engineering machinery and gradient control preparation method of multiphase composite reinforced alloy

Abstract

The invention relates to the technical field of metal material preparation, in particular to a multiphase composite reinforced alloy for a quick-wear part of engineering machinery and a gradient control preparation method of the multiphase composite reinforced alloy, and the multiphase composite reinforced alloy comprises the following chemical components in percentage by weight: 0.3-0.6% of C, 2.8-3.7% of Si, 0.1-0.9% of Mn, 0.2-0.5% of Cr, 0.02-0.05% of Mo, 0.09-0.13% of Ti, 0.001-0.003% of B, 0.01-0.03% of Al and the balance of Fe and inevitable impurities. The residual tensile stress on the surface of the structure is synchronously reduced through single quenching and partition heat treatment, and the wear resistance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal material preparation, and in particular to a multiphase composite strengthened alloy for wearing parts of construction machinery and a gradient controllable preparation method thereof. Background Art

[0002] To improve wear resistance and strength, traditional steels (such as maraging steel and bainitic steel) often adopt processes such as shot peening surface strengthening and multi-stage heat treatment. However, there are the following defects: Although the shot peening process introduces surface compressive stress, it is easy to cause the accumulation of tensile stress in the subsurface layer, and the fatigue life fluctuates greatly. For example, in the Chinese patent "A processing technology of a harmonic reducer flexspline" with the application number CN202410749840.1, the residual stress is 600 - 800 MPa, the process is complex and the cost is high: the shot peening + multiple tempering process requires additional equipment and increases energy consumption.

[0003] During the treatment of the conventional quenching + partitioning process, due to the uneven microstructure transformation, residual tensile stress of ≥300 MPa is easily generated on the surface layer, resulting in the easy initiation of microcracks in the wear-resistant layer under alternating loads and accelerating wear failure. For example, in the Chinese patent "An ignition process of a stainless steel continuous annealing furnace" with the application number CN202411658730.0.

[0004] In view of the problems of existing steels, such as the accumulation of subsurface tensile stress (600 - 800 MPa) due to dependence on shot peening strengthening, insufficient stability of retained austenite (volume fraction < 15%), and complex processes (cost increase of 15 - 20%), an innovative solution is proposed to simultaneously reduce the residual tensile stress on the surface of the structure and improve wear resistance through single quenching + partitioning heat treatment. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a multiphase composite strengthened alloy for wearing parts of construction machinery and a gradient controllable preparation method thereof, which can simultaneously reduce the residual tensile stress on the surface of the structure and improve wear resistance through single quenching + partitioning heat treatment.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A multiphase composite strengthened alloy for wearing parts of construction machinery, the chemical composition of the alloy by weight percentage includes: C: 0.3 - 0.6%, Si: 2.8 - 3.7%, Mn: 0.1 - 0.9%, Cr: 0.2 - 0.5%, Mo: 0.02 - 0.05%, Ti: 0.09 - 0.13%, B: 0.001 - 0.003%, Al: 0.01 - 0.03%, and the balance is Fe and unavoidable impurities;

[0008] Among them, the C / Si mass ratio = 0.09 - 0.19;

[0009] Ti / N mass ratio = 3.5 - 4.0;

[0010] Total content of Mn + Cr ≤ 1.1%.

[0011] Preferably, the matrix metallographic structure of the alloy comprises martensite, secondary martensite, bainite and retained austenite, wherein alloying elements such as Cr, Si, Mn, and Mo are dissolved in the matrix, and the carbide is spherical TiC with a size of 10 - 30 nm.

[0012] Preferably, the yield strength of the alloy ≥ 1766 MPa; tensile strength ≥ 2000 MPa; Vickers hardness ≥ 560 HV; V-notch impact energy at 20 °C ≥ 20 J / cm 2 ; volume fraction of retained austenite ≥ 20%.

[0013] The gradient control preparation method of a multiphase composite strengthened alloy for a vulnerable part of construction machinery according to any one of the above, comprising the following steps:

[0014] S1, melting and casting treatment: Heat each element to 1550 - 1590 °C in a vacuum induction melting furnace under argon protection according to the formula ratio to melt the steel liquid. During casting, use a copper mold for rapid cooling, control the solidification rate ≥ 35 °C / s, and obtain an ingot with a cross-sectional size of 180 mm × 45 mm;

[0015] S2, gradient forging treatment: Place the ingot obtained in step S1 in a gradient heating furnace, heat it to 1150 - 1200 °C at a rate of 120 - 150 °C / h, introduce a N2 / H2 mixed gas with a volume ratio of 4:1, keep it warm for 3 - 6 hours and then perform four-way alternating forging, with a single-pass deformation amount of 20 - 25%, a cumulative forging ratio ≥ 4.5, and control the temperature of the billet core at 800 - 880 °C by laser temperature measurement during the final forging stage;

[0016] S3, temperature-controlled cooling: Immediately perform water mist cooling after final forging, with a cooling rate ≥ 80 °C / s, so that the surface temperature of the forging drops to 250 - 300 °C within 8 - 12 seconds, and obtain a fine-grained forging blank with a grain size grade ≥ 8;

[0017] S4, composite quenching: Heat the forging blank obtained in step S3 to 900 - 950 °C and keep it warm for 25 - 35 min, and perform water quenching to 150 - 180 °C in a way that the length direction is perpendicular to the water surface. The temperature of the quenching medium is 70 - 80 °C, and the distance from the steel cross-section to the water surface > 10 mm;

[0018] S5, aging treatment: Place the quenched part obtained in step S4 in silicone oil at 150 - 180 °C and keep it warm for 6 min, then heat it to 350 - 400 °C and keep it warm for 10 - 30 min and then water quench it to room temperature.

[0019] Preferably, during melting in step S1, the initial grain size ≤ 50 μm.

[0020] Preferably, during the four-way alternative forging in step S2, the forging direction circulates in the order of X→Y→Z→diagonal direction, and the deviation of the deformation amount in each direction is ≤3%.

[0021] Preferably, in step S3, the water mist cooling uses an adjustable annular nozzle array, the atomizing water pressure is maintained at 0.8 - 1.2 MPa, and the water-gas volume ratio is controlled at 1:(3 - 5).

[0022] Preferably, the water quenching process parameters in step S4 satisfy: the single water quenching time is 6 - 20 s; the number of continuous water quenching times is 2 - 4 times; the first water quenching temperature is ≤300 °C, and the second water quenching temperature is ≥200 °C; after each water quenching, it is air-cooled to 200 - 230 °C and then put into silicone oil.

[0023] Preferably, in the water quenching process of step S4, an infrared temperature detector is used to monitor the temperature, and the measuring tilt angle of the probe is 120 - 150°.

[0024] Advantages of the present invention:

[0025] 1. The present invention optimizes and innovates under the existing alloy system. By introducing N element (removing surface oxides by H2 reducibility, enhancing the surface activity of the metal, decomposing N2 into active nitrogen atoms and adsorbing them on the surface of the ingot. Then, increasing the diffusion rate at high temperature, the nitrogen atoms can penetrate into the interior of the ingot) + regulating the Ti / N ratio and synergistic gradient forging + composite quenching process, the precipitation of nano-TiC is dispersed and the retained austenite is stabilized, thereby synchronously reducing the residual tensile stress (<100 MPa) and improving the wear resistance, while greatly reducing the usage of precious metals Mo, Cr, and Mn. And without relying on precious metals such as Ni, Co, and Cr, the yield strength ≥1766 MPa, the tensile strength ≥2000, KV2 ≥20 J can be achieved, and it can be rapidly prepared with the total production time <7 h.

[0026] 2. The overall process route of the present invention is: forged blank → homogenization annealing → temperature-controlled forging → austenitization → quenching → two-stage partitioning. During the casting process, melting is carried out at 1550 - 1590°C + copper mold chill (solidification rate ≥ 35°C / s) to inhibit dendritic segregation and reduce compositional inhomogeneity (segregation index ≤ 1.05), with the initial grain size ≤ 50μm, providing a uniform matrix for subsequent forging. During the gradient forging process, it is carried out at 1150 - 1200°C + N2 / H2 mixed gas (4:1) + four-way alternating forging. High-temperature large deformation promotes complete recrystallization, and in the N2 / H2 atmosphere, TiN and TiC cooperate to capture hydrogen atoms, eliminating the hydrogen diffusion process. Through X→Y→Z→diagonal cyclic forging, anisotropy is eliminated. Water mist cooling inhibits dislocation recovery, retains a high density of dislocations, and refines the width of lath martensite ≤ 0.2μm, enhancing strength and toughness. Silicon oil insulation is used, and silicon oil insulation induces dislocation rearrangement, reducing residual stress. Tempering at 350 - 400°C promotes the decomposition of retained austenite into secondary martensite, enhancing strength and stability.

[0027] 3. The alloy of the present invention has a multiphase structure. Through the martensite matrix (60 - 70%), it provides ultra-high strength (contribution ≥ 1500MPa). Through the retained austenite (20 - 28%), it triggers the TRIP effect. During plastic deformation, austenite → martensite transformation occurs, absorbing energy to enhance toughness (impact absorption work ≥ 21%) and crack blunting and propagation increasing the elongation (contribution of 5% elongation). Through the bainitic ferrite (5 - 10%), it coordinates deformation and balances the brittleness of martensite. For secondary martensite, TiC provides precipitation strengthening, and the Orowan mechanism hinders dislocation movement (contribution ≥ 300MPa strength). The interface captures diffused hydrogen, inhibiting hydrogen-induced cracking.

[0028] 4. The present invention is a alloy steel that realizes low residual stress and high wear resistance through the synergistic regulation of composition and process, and is applicable to high-performance structural steel fields such as construction machinery and automotive transmission components. Description of the Drawings

[0029] Figure 1 It is the microstructural diagram of Example 1 and Comparative Example 1 of the present invention;

[0030] Figure 2 It is the tensile test result diagram of the specimens of Examples 1 - 9 of the present invention;

[0031] Figure 3 It is the Charpy impact fracture morphology diagram of Examples 1 - 9 of the present invention;

[0032] Figure 4 It is the comparison diagram of the impact wear morphology of Comparative Example 1 and Example 1 of the present invention;

[0033] Figure 5 It is the XRD residual stress test of Example 1 of the present invention;

[0034] Figure 6 XRD residual stress test for Comparative Example 1 of the present invention. Specific embodiments

[0035] For the convenience of those skilled in the art, the present invention will be further described below in conjunction with embodiments and the accompanying drawings. The content mentioned in the embodiments does not limit the present invention.

[0036] The setting principle of the elements is as follows:

[0037] C: 0.3 - 0.6%: Solution strengthening. C atoms are interstitially dissolved in the matrix to improve the matrix strength, carbide control, form nano-TiC (10 - 30 nm) in combination with Ti, and avoid brittleness caused by coarse carbides. Si: 2.8 - 3.7%: Replace the solution strengthening effect of Ni / Co, inhibit cementite. Si inhibits the precipitation of Fe3C, promotes the enrichment of carbon in austenite, improves the carbon activity, and C / Si = 0.1 - 0.3 optimizes the austenite stability, reduces the pearlite transformation, and promotes the formation of bainite / martensite.

[0038] B: 0.001 - 0.003%: Grain boundary strengthening and hardenability improvement. B atoms segregate at the austenite grain boundary, inhibit the nucleation of ferrite, improve the hardenability, extend the transformation time of austenite to bainite under the partitioning state, and refine the structure.

[0039] C / Si = 0.09 - 0.19: Limit the oxidation tendency of Si and improve the hardenability.

[0040] Ti / N = 3.5 - 4.0: Through precise stoichiometric ratio control, promote the preferential formation of 10 - 30 nm spherical TiC over coarse TiN (XRD verifies that the peak half-width of TiC < 0.5°).

[0041] Mn + Cr ≤ 1.1%: Inhibit MnS inclusions, and at the same time Cr solution strengthens the matrix.

[0042] Example 1

[0043] Prepare raw materials according to the following weight ratios:

[0044] C: 0.45%, Si: 3.0%, Mn: 0.5%, Cr: 0.4%, Mo: 0.035%, Ti: 0.11%, B: 0.002%, Al: 0.02%, N*: 0.0299%, and the balance is Fe and unavoidable impurities.

[0045] Prepare the alloy:

[0046] S1, Casting treatment: Heat the elements in a vacuum induction melting furnace under argon protection to 1550 - 1590 °C to melt the steel liquid according to the formula ratio. During casting, use a copper mold for rapid cooling, control the solidification rate ≥ 35 °C / s, obtain an ingot with a cross-sectional size of 180 mm × 45 mm, and the initial grain size ≤ 50 μm;

[0047] S2, Gradient forging treatment: Place the ingot obtained in step S1 in a gradient heating furnace, heat it to 1150 °C at a rate of 120 - 150 °C / h, introduce a N2 / H2 mixed gas with a volume ratio of 4:1, after holding for 3 hours, perform four-way alternating forging. The forging direction circulates in the order of X → Y → Z → diagonal direction. The deviation of the deformation amount in each direction ≤ 3%, the single-pass deformation amount is 20 - 25%, the cumulative forging ratio ≥ 4.5, and in the final forging stage, control the billet core temperature at 850 °C through laser temperature measurement;

[0048] S3, Temperature-controlled cooling: Immediately after final forging, perform water mist cooling. Use an adjustable annular nozzle array, maintain the atomizing water pressure at 0.8 - 1.2 MPa, control the water-gas volume ratio at 1:(3 - 5), the cooling rate ≥ 80 °C / s, so that the surface temperature of the forging drops to 250 - 300 °C within 8 - 12 seconds, and obtain a fine-grained forging blank with a grain size grade ≥ 8;

[0049] S4, Composite quenching: Heat the forging blank obtained in step S3 to 900 °C and hold for 25 min, then water quench it to 150 - 180 °C in a way that the length direction is perpendicular to the water surface. The single water quenching time is 6 - 20 s; The number of continuous water quenching is 2 times. Use an infrared temperature detector to monitor the temperature, and the probe measurement tilt angle is 120 - 150°; The first water quenching temperature ≤ 300 °C, the second water quenching temperature is 200 °C; After each water quenching, air cool to 200 - 230 °C and then put it into silicone oil. The temperature of the quenching medium is 70 - 80 °C, and the distance from the steel cross-section to the water surface > 10 mm;

[0050] S5, Aging treatment: Place the quenched part obtained in step S4 in silicone oil at 150 °C and hold for 6 min, then heat it to 350 °C and hold for 10 min, and then water quench it to room temperature to obtain the alloy.

[0051] Example 2

[0052] Prepare raw materials according to the following weight ratio:

[0053] C: 0.60%, Si: 3.2%, Mn: 0.9%, Cr: 0.2%, Mo: 0.050%, Ti: 0.13%, B: 0.003%, Al: 0.03%, N*: 0.0374%, and the balance is Fe and unavoidable impurities.

[0054] Prepare the alloy:

[0055] S1, Casting treatment: Heat the elements to 1550 - 1590 °C in a vacuum induction melting furnace under argon protection according to the formula ratio to melt the steel liquid. During casting, use a copper mold for rapid cooling, control the solidification rate ≥ 35 °C / s, and obtain an ingot with a cross-sectional size of 180 mm × 45 mm, with an initial grain size ≤ 50 μm;

[0056] S2, Gradient forging treatment: Place the ingot obtained in step S1 in a gradient heating furnace, heat it to 1160 °C at a rate of 120 - 150 °C / h, introduce a N2 / H2 mixed gas with a volume ratio of 4:1, hold for 6 hours, and then perform four-way alternating forging. The forging direction cycles in the order of X → Y → Z → diagonal direction. The deviation of the deformation amount in each direction ≤ 3%, the single-pass deformation amount is 20 - 25%, the cumulative forging ratio ≥ 4.5, and the core temperature of the billet is controlled at 850 °C by laser temperature measurement during the final forging stage;

[0057] S3, Temperature-controlled cooling: Immediately perform water mist cooling after final forging. Use an adjustable annular nozzle array, maintain the atomizing water pressure at 0.8 - 1.2 MPa, control the water-gas volume ratio at 1:(3 - 5), and the cooling rate ≥ 80 °C / s, so that the surface temperature of the forging drops to 250 - 300 °C within 8 - 12 seconds, and obtain a fine-grained forging blank with a grain size grade ≥ 8;

[0058] S4, Composite quenching: Heat the forging blank obtained in step S3 to 930 °C and hold for 26 min, then water quench it to 150 - 180 °C in a way that the length direction is perpendicular to the water surface. The single water quenching time is 6 - 20 s; the number of continuous water quenching is 2 times. Use an infrared temperature detector to monitor the temperature, and the probe measurement tilt angle is 120 - 150°; the first water quenching temperature ≤ 300 °C, the second water quenching temperature is 220 °C; after each water quenching, air cool to 200 - 230 °C and then put it into silicone oil, the temperature of the quenching medium is 70 - 80 °C, and the distance from the steel cross-section to the water surface > 10 mm;

[0059] S5, Aging treatment: Place the quenched part obtained in step S4 in silicone oil at 160 °C and hold for 6 min, then heat it to 360 °C and hold for 15 min, and then water quench it to room temperature to obtain the alloy.

[0060] Example 3

[0061] Prepare raw materials according to the following weight ratio:

[0062] C: 0.30%, Si: 3.3%, Mn: 0.1%, Cr: 0.5%, Mo: 0.020%, Ti: 0.09%, B: 0.001%, Al: 0.01%, N*: 0.0257%, and the balance is Fe and unavoidable impurities.

[0063] Prepare the alloy:

[0064] S1, Casting treatment: Heat the elements to 1550 - 1590 °C in a vacuum induction melting furnace under argon protection according to the formula ratio to melt the steel liquid. During casting, use a copper mold for rapid cooling, control the solidification rate ≥ 35 °C / s, obtain an ingot with a cross-sectional size of 180 mm × 45 mm, and the initial grain size ≤ 50 μm;

[0065] S2, Gradient forging treatment: Place the ingot obtained in step S1 in a gradient heating furnace, heat it to 1160 °C at a rate of 120 - 150 °C / h, introduce a mixed gas of N2 / H2 with a volume ratio of 4:1, hold for 5 hours, and then perform four-way alternating forging. The forging direction cycles in the order of X → Y → Z → diagonal direction. The deviation of the deformation amount in each direction ≤ 3%, the single-pass deformation amount is 20 - 25%, the cumulative forging ratio ≥ 4.5, and the core temperature of the billet is controlled at 880 °C by laser temperature measurement during the final forging stage;

[0066] S3, Temperature-controlled cooling: Immediately perform water spray cooling after final forging. Use an adjustable annular nozzle array, maintain the atomizing water pressure at 0.8 - 1.2 MPa, control the water-gas volume ratio at 1:(3 - 5), and the cooling rate ≥ 80 °C / s, so that the surface temperature of the forging drops to 250 - 300 °C within 8 - 12 seconds, obtaining a fine-grained forging blank with a grain size grade ≥ 8;

[0067] S4, Composite quenching: Heat the forging blank obtained in step S3 to 930 °C and hold for 28 min, then water quench it to 150 - 180 °C in a way that the length direction is perpendicular to the water surface. The single water quenching time is 6 - 20 s; The number of continuous water quenching is 3 times. Use an infrared temperature detector to monitor the temperature, and the probe measurement tilt angle is 120 - 150°; The first water quenching temperature ≤ 300 °C, and the second water quenching temperature is 200 °C; After each water quenching, air cool to 200 - 230 °C and then put it into silicone oil. The temperature of the quenching medium is 70 - 80 °C, and the distance from the steel cross-section to the water surface > 10 mm;

[0068] S5, Aging treatment: Place the quenched part obtained in step S4 in silicone oil at 180 °C and hold for 7 min, then heat it to 370 °C and hold for 15 min, and then water quench it to room temperature to obtain the alloy.

[0069] Example 4

[0070] Prepare raw materials according to the following weight ratios:

[0071] C: 0.50%, Si: 3.5%, Mn: 0.6%, Cr: 0.3%, Mo: 0.040%, Ti: 0.12%, B: 0.0025%, Al: 0.025%, N*: 0.0304%, and the balance is Fe and unavoidable impurities.

[0072] Prepare the alloy:

[0073] S1, Casting treatment: Heat the elements in a vacuum induction melting furnace under argon protection to 1550 - 1590 °C to melt the steel liquid according to the formula ratio. During casting, use a copper mold for rapid cooling, control the solidification rate ≥ 35 °C / s, obtain an ingot with a cross-sectional size of 180 mm × 45 mm, and the initial grain size ≤ 50 μm;

[0074] S2, Gradient forging treatment: Place the ingot obtained in step S1 in a gradient heating furnace, heat it to 1160 °C at a rate of 120 - 150 °C / h, introduce a N2 / H2 mixed gas with a volume ratio of 4:1, after holding for 4 hours, perform four-way alternating forging. The forging direction circulates in the order of X → Y → Z → diagonal direction. The deviation of the deformation amount in each direction ≤ 3%, the single-pass deformation amount is 20 - 25%, the cumulative forging ratio ≥ 4.5, and in the final forging stage, control the billet core temperature at 850 °C through laser temperature measurement;

[0075] S3, Temperature-controlled cooling: Immediately after final forging, perform water mist cooling. Use an adjustable annular nozzle array, maintain the atomizing water pressure at 0.8 - 1.2 MPa, control the water-gas volume ratio at 1:(3 - 5), and the cooling rate ≥ 80 °C / s, so that the surface temperature of the forging drops to 250 - 300 °C within 8 - 12 seconds, obtaining a fine-grained forging blank with a grain size grade ≥ 8;

[0076] S4, Composite quenching: Heat the forging blank obtained in step S3 to 940 °C and hold for 28 min, then perform water quenching to 150 - 180 °C in a way that the length direction is perpendicular to the water surface. The single water quenching time is 6 - 20 s; The number of continuous water quenching times is 2 times. Use an infrared temperature detector to monitor the temperature, and the probe measurement tilt angle is 120 - 150°; The first water quenching temperature ≤ 300 °C, the second water quenching temperature is 230 °C; After each water quenching, air cool to 200 - 230 °C and then put it into silicone oil. The temperature of the quenching medium is 70 - 80 °C, and the distance from the steel cross-section to the water surface > 10 mm;

[0077] S5, Aging treatment: Place the quenched part obtained in step S4 in silicone oil at 150 °C and hold for 7 min, then heat it to 380 °C and hold for 20 min, and then water quench to room temperature to obtain the alloy.

[0078] Example 5

[0079] Prepare raw materials according to the following weight ratio:

[0080] C: 0.55%, Si: 3.4%, Mn: 0.3%, Cr: 0.3%, Mo: 0.030%, Ti: 0.10%, B: 0.002%, Al: 0.02%, N*: 0.0283%, and the balance is Fe and unavoidable impurities.

[0081] Prepare the alloy:

[0082] S1, Casting Treatment: Heat the elements to 1550 - 1590°C in a vacuum induction melting furnace under argon protection according to the formula ratio to melt the steel liquid. During casting, use a copper mold for rapid cooling, control the solidification rate ≥ 35°C / s, obtain an ingot with a cross-sectional size of 180mm × 45mm, and the initial grain size ≤ 50μm;

[0083] S2, Gradient Forging Treatment: Place the ingot obtained in step S1 in a gradient heating furnace, heat it to 1180°C at a rate of 120 - 150°C / h, introduce a mixed gas of N2 / H2 with a volume ratio of 4:1, hold for 5 hours, and then perform four-way alternating forging. The forging direction circulates in the order of X → Y → Z → diagonal direction. The deviation of the deformation amount in each direction ≤ 3%, the single-pass deformation amount is 20 - 25%, the cumulative forging ratio ≥ 4.5, and the core temperature of the blank is controlled at 840°C by laser temperature measurement during the final forging stage;

[0084] S3, Temperature-controlled Cooling: Immediately perform water mist cooling after final forging. Use an adjustable annular nozzle array, maintain the atomizing water pressure at 0.8 - 1.2MPa, control the water-gas volume ratio at 1:(3 - 5), and the cooling rate ≥ 80°C / s, so that the surface temperature of the forging drops to 250 - 300°C within 8 - 12 seconds, and obtain a fine-grained forging blank with a grain size grade ≥ 8;

[0085] S4, Composite Quenching: Heat the forging blank obtained in step S3 to 950°C and hold for 35min, then perform water quenching to 150 - 180°C in a way that the length direction is perpendicular to the water surface. The single water quenching time is 6 - 20s; the continuous water quenching times are 4 times. Use an infrared temperature detector to monitor the temperature, and the measuring tilt angle of the probe is 120 - 150°; the first water quenching temperature ≤ 300°C, and the second water quenching temperature is 200°C; after each water quenching, air cool to 200 - 230°C and then put it into silicone oil. The temperature of the quenching medium is 70 - 80°C, and the distance from the steel cross-section to the water surface > 10mm;

[0086] S5, Aging Treatment: Place the quenched part obtained in step S4 in silicone oil at 160°C and hold for 6min, then heat it to 390°C and hold for 15min, and then water quench to room temperature to obtain the alloy.

[0087] Example 6

[0088] Prepare raw materials according to the following weight ratio:

[0089] C: 0.40%, Si: 2.8%, Mn: 0.7%, Cr: 0.4%, Mo: 0.045%, Ti: 0.12%, B: 0.003%, Al: 0.03%, N*: 0.0321%, and the balance is Fe and unavoidable impurities.

[0090] Prepare the alloy:

[0091] S1, Melting and casting treatment: Heat the elements according to the formula ratio to 1550 - 1590 °C in a vacuum induction melting furnace under argon protection to melt the steel liquid. During casting, use a copper mold for rapid cooling, control the solidification rate ≥ 35 °C / s, obtain an ingot with a cross-sectional size of 180 mm × 45 mm, and the initial grain size ≤ 50 μm;

[0092] S2, Gradient forging treatment: Place the ingot obtained in step S1 in a gradient heating furnace, heat it to 1200 °C at a rate of 120 - 150 °C / h, introduce a N2 / H2 mixed gas with a volume ratio of 4:1, after holding for 4 hours, perform four-way alternating forging. The forging direction circulates in the order of X → Y → Z → diagonal direction. The deviation of the deformation amount in each direction ≤ 3%, the single-pass deformation amount is 20 - 25%, the cumulative forging ratio ≥ 4.5, and in the final forging stage, control the temperature of the billet core at 810 °C through laser temperature measurement;

[0093] S3, Temperature-controlled cooling: Immediately after final forging, perform water mist cooling. Use an adjustable annular nozzle array, maintain the atomizing water pressure at 0.8 - 1.2 MPa, control the water-gas volume ratio at 1:(3 - 5), the cooling rate ≥ 80 °C / s, so that the surface temperature of the forging drops to 250 - 300 °C within 8 - 12 seconds, and obtain a fine-grained forging blank with a grain size grade ≥ 8;

[0094] S4, Composite quenching: Heat the forging blank obtained in step S3 to 900 °C and hold for 31 min, then perform water quenching to 150 - 180 °C in a way that the length direction is perpendicular to the water surface. The single water quenching time is 6 - 20 s; the number of continuous water quenching is 2 times. Use an infrared temperature detector to monitor the temperature, and the measuring inclination angle of the probe is 120 - 150°; the first water quenching temperature ≤ 300 °C, the second water quenching temperature is 200 °C; after each water quenching, air cool to 200 - 230 °C and then put it into silicone oil, the temperature of the quenching medium is 70 - 80 °C, and the distance from the steel cross-section to the water surface > 10 mm;

[0095] S5, Aging treatment: Place the quenched part obtained in step S4 in silicone oil at 180 °C and hold for 6 min, then heat it to 400 °C and hold for 30 min, and then water quench to room temperature to obtain the alloy.

[0096] Example 7

[0097] Prepare raw materials according to the following weight ratio:

[0098] C: 0.33%, Si: 3.7%, Mn: 0.6%, Cr: 0.3%, Mo: 0.020%, Ti: 0.09%, B: 0.002%, Al: 0.02%, N*: 0.0225%, and the balance is Fe and unavoidable impurities.

[0099] Prepare the alloy:

[0100] S1, Melting and Casting Treatment: Heat the elements to 1550 - 1590 °C in a vacuum induction melting furnace under argon protection according to the formula ratio to melt the steel liquid. During casting, use a copper mold for rapid cooling, control the solidification rate ≥ 35 °C / s, obtain an ingot with a cross-sectional size of 180 mm × 45 mm, and the initial grain size ≤ 50 μm;

[0101] S2, Gradient Forging Treatment: Place the ingot obtained in step S1 in a gradient heating furnace, heat it to 1150 °C at a rate of 120 - 150 °C / h, introduce a N2 / H2 mixed gas with a volume ratio of 4:1, after holding for 4 hours, perform four-way alternating forging, and the forging direction cycles in the order of X → Y → Z → diagonal direction. The deviation of the deformation amount in each direction ≤ 3%, the single-pass deformation amount is 20 - 25%, the cumulative forging ratio ≥ 4.5, and in the final forging stage, control the temperature of the billet core at 820 °C through laser temperature measurement;

[0102] S3, Temperature-controlled Cooling: Immediately perform water mist cooling after final forging. Use an adjustable annular nozzle array, maintain the atomizing water pressure at 0.8 - 1.2 MPa, control the water-gas volume ratio at 1:(3 - 5), and the cooling rate ≥ 80 °C / s, so that the surface temperature of the forging drops to 250 - 300 °C within 8 - 12 seconds, and obtain a fine-grained forging blank with a grain size grade ≥ 8;

[0103] S4, Composite Quenching: Heat the forging blank obtained in step S3 to 900 °C and hold for 30 min, then perform water quenching to 150 - 180 °C in a way that the length direction is perpendicular to the water surface, and the single water quenching time is 6 - 20 s; Continuously perform water quenching 3 times, use an infrared temperature detector to monitor the temperature, and the probe measurement tilt angle is 120 - 150°; The first water quenching temperature ≤ 300 °C, the second water quenching temperature is 230 °C; After each water quenching, air cool to 200 - 230 °C and then put it into silicone oil, the temperature of the quenching medium is 70 - 80 °C, and the distance from the steel cross-section to the water surface > 10 mm;

[0104] S5, Aging Treatment: Place the quenched part obtained in step S4 in silicone oil at 180 °C and hold for 7 min, then heat it to 400 °C and hold for 30 min, and then water quench to room temperature to obtain the alloy.

[0105] Example 8

[0106] Prepare raw materials according to the following weight ratio:

[0107] C: 0.30%, Si: 3.3%, Mn: 0.8%, Cr: 0.2%, Mo: 0.050%, Ti: 0.10%, B: 0.002%, Al: 0.02%, N*: 0.0286%, and the balance is Fe and unavoidable impurities.

[0108] Prepare the alloy:

[0109] S1, Melting and Casting Treatment: Heat the elements to 1550 - 1590 °C in a vacuum induction melting furnace under argon protection according to the formula ratio to melt the steel liquid. During casting, use a copper mold for rapid cooling, control the solidification rate ≥ 35 °C / s, obtain an ingot with a cross-sectional size of 180 mm × 45 mm, and the initial grain size ≤ 50 μm;

[0110] S2, Gradient Forging Treatment: Place the ingot obtained in step S1 in a gradient heating furnace, heat it to 1170 °C at a rate of 120 - 150 °C / h, introduce a N2 / H2 mixed gas with a volume ratio of 4:1, after holding for 5 hours, perform four-way alternating forging. The forging direction cycles in the order of X → Y → Z → diagonal direction, the deviation of the deformation amount in each direction ≤ 3%, the single-pass deformation amount is 20 - 25%, the cumulative forging ratio ≥ 4.5, and in the final forging stage, control the temperature of the billet core at 800 °C through laser temperature measurement;

[0111] S3, Temperature-controlled Cooling: Immediately after final forging, perform water mist cooling. Use an adjustable annular nozzle array, maintain the atomizing water pressure at 0.8 - 1.2 MPa, control the water-gas volume ratio at 1:(3 - 5), the cooling rate ≥ 80 °C / s, so that the surface temperature of the forging drops to 250 - 300 °C within 8 - 12 seconds, and obtain a fine-grained forging blank with a grain size grade ≥ 8;

[0112] S4, Composite Quenching: Heat the forging blank obtained in step S3 to 940 °C and hold for 30 min, then perform water quenching to 150 - 180 °C in a way that the length direction is perpendicular to the water surface, the single water quenching time is 6 - 20 s; the number of continuous water quenching times is 4 times, use an infrared temperature detector to monitor the temperature, the probe measurement tilt angle is 120 - 150°; the first water quenching temperature ≤ 300 °C, the second water quenching temperature is 220 °C; after each water quenching, air cool to 200 - 230 °C and then put it into silicone oil, the temperature of the quenching medium is 70 - 80 °C, and the distance from the steel cross-section to the water surface > 10 mm;

[0113] S5, Aging Treatment: Place the quenched part obtained in step S4 in silicone oil at 150 °C and hold for 6 min, then heat it to 350 °C and hold for 15 min, and then water quench to room temperature to obtain the alloy.

[0114] Example 9

[0115] Prepare raw materials according to the following weight ratio:

[0116] C: 0.60%, Si: 3.1%, Mn: 0.6%, Cr: 0.4%, Mo: 0.030%, Ti: 0.09%, B: 0.002%, Al: 0.01%, N*: 0.0250%, the balance is Fe and unavoidable impurities.

[0117] Prepare the alloy:

[0118] S1, Casting treatment: Heat the elements to 1550 - 1590 °C in a vacuum induction melting furnace under argon protection according to the formula ratio to melt the steel liquid. During casting, use a copper mold for rapid cooling, control the solidification rate ≥ 35 °C / s, and obtain an ingot with a cross-sectional size of 180 mm × 45 mm, with an initial grain size ≤ 50 μm;

[0119] S2, Gradient forging treatment: Place the ingot obtained in step S1 in a gradient heating furnace, heat it to 1160 °C at a rate of 120 - 150 °C / h, introduce a N2 / H2 mixed gas with a volume ratio of 4:1, hold for 4 hours, and then perform four-way alternating forging. The forging direction cycles in the order of X → Y → Z → diagonal direction, with the deviation of the deformation amount in each direction ≤ 3%, the single-pass deformation amount 20 - 25%, the cumulative forging ratio ≥ 4.5, and control the temperature of the billet core at 810 °C through laser temperature measurement during the final forging stage;

[0120] S3, Temperature-controlled cooling: Immediately perform water mist cooling after final forging. Use an adjustable annular nozzle array, maintain the atomized water pressure at 0.8 - 1.2 MPa, control the water-gas volume ratio at 1:(3 - 5), and the cooling rate ≥ 80 °C / s, so that the surface temperature of the forging drops to 250 - 300 °C within 8 - 12 seconds, and obtain a fine-grained forging blank with a grain size grade ≥ 8;

[0121] S4, Composite quenching: Heat the forging blank obtained in step S3 to 920 °C and hold for 30 min, then perform water quenching to 150 - 180 °C in a way that the length direction is perpendicular to the water surface, with a single water quenching time of 6 - 20 s; The number of continuous water quenching times is 2 times, use an infrared temperature detector to monitor the temperature, and the probe measurement tilt angle is 120 - 150°; The first water quenching temperature ≤ 300 °C, and the second water quenching temperature is 210 °C; After each water quenching, air cool to 200 - 230 °C and then put it into silicone oil, with the quenching medium temperature at 70 - 80 °C, and the distance from the steel cross-section to the water surface > 10 mm;

[0122] S5, Aging treatment: Place the quenched part obtained in step S4 in silicone oil at 160 °C and hold for 7 min, then heat it to 350 °C and hold for 20 min, and then water quench to room temperature to obtain the alloy.

[0123] Comparative Example 1

[0124] Prepare raw materials according to the following weight ratio:

[0125] C: 0.35%, Si: 3.7%, Mn: 0.2%, Cr: 0.4%, Mo: 0.025%, Ti: 0.10%, B: 0.0015%, Al: 0.015%, N*: 0.0270%, and the balance is Fe and unavoidable impurities.

[0126] Prepare the alloy:

[0127] S1, ingot casting treatment: Heat the elements to 1550 - 1590 °C in a vacuum induction melting furnace under argon protection according to the formula ratio to melt the steel liquid. During casting, use a copper mold for rapid cooling, control the solidification rate ≥ 35 °C / s, obtain an ingot with a cross-sectional size of 180 mm × 45 mm, and the initial grain size ≤ 50 μm;

[0128] S2, gradient forging treatment: Place the ingot obtained in step S1 in a gradient heating furnace, heat it to 1160 °C at a rate of 120 - 150 °C / h, introduce a N2 / H2 mixed gas with a volume ratio of 4:1, after holding for 3 hours, perform four-way alternating forging. The forging direction cycles in the order of X → Y → Z → diagonal direction. The deviation of the deformation amount in each direction ≤ 3%, the single-pass deformation amount is 20 - 25%, the cumulative forging ratio ≥ 4.5, and in the final forging stage, control the temperature of the billet core at 1000 °C through laser temperature measurement;

[0129] S3, temperature-controlled cooling: Immediately perform water mist cooling after final forging. Use an adjustable annular nozzle array, maintain the atomized water pressure at 0.8 - 1.2 MPa, control the water-gas volume ratio at 1:(3 - 5), the cooling rate ≥ 80 °C / s, so that the surface temperature of the forging drops to 250 - 300 °C within 8 - 12 seconds, and obtain a fine-grained forging blank with a grain size grade ≥ 8;

[0130] S4, composite quenching: Heat the forging blank obtained in step S3 to 930 °C and hold for 50 min, then perform water quenching to 150 - 180 °C in a way that the length direction is perpendicular to the water surface. The single water quenching time is 6 - 20 s; The number of continuous water quenching is 3 times. Use an infrared temperature detector to monitor the temperature, and the probe measurement tilt angle is 120 - 150°; The first water quenching temperature ≤ 300 °C, the second water quenching temperature is 260 °C; After each water quenching, air cool to 200 - 230 °C and then put it into silicone oil, the temperature of the quenching medium is 70 - 80 °C, and the distance from the steel cross-section to the water surface > 10 mm;

[0131] S5, aging treatment: Place the quenched part obtained in step S4 in silicone oil at 230 °C and hold for 6 min, then heat to 250 °C and hold for 5 min, and then water quench to room temperature to obtain the alloy.

[0132] Comparative Example 2

[0133] Prepare raw materials according to the following weight ratio:

[0134] C: 0.58%, Si: 3.1%, Mn: 0.8%, Cr: 0.2%, Mo: 0.048%, Ti: 0.14%, B: 0.0028%, Al: 0.028%, N*: 0.0350%, and the balance is Fe and unavoidable impurities.

[0135] Prepare the alloy:

[0136] S1, Melting and Casting Treatment: Heat the elements according to the formula ratio to 1550 - 1590 °C in a vacuum induction melting furnace under argon protection to melt the steel liquid. During casting, use a copper mold for rapid cooling, control the solidification rate ≥ 35 °C / s, obtain an ingot with a cross-sectional size of 180 mm × 45 mm, and the initial grain size ≤ 50 μm;

[0137] S2, Gradient Forging Treatment: Place the ingot obtained in step S1 in a gradient heating furnace, heat it to 1170 °C at a rate of 120 - 150 °C / h, introduce a N2 / H2 mixed gas with a volume ratio of 4:1, after holding for 3 hours, perform four-way alternating forging. The forging direction circulates in the order of X → Y → Z → diagonal direction. The deviation of the deformation amount in each direction ≤ 3%, the single-pass deformation amount is 20 - 25%, the cumulative forging ratio ≥ 4.5, and in the final forging stage, control the temperature of the billet core at 840 °C through laser temperature measurement;

[0138] S3, Temperature-controlled Cooling: Immediately after final forging, perform water mist cooling. Use an adjustable annular nozzle array, maintain the atomizing water pressure at 0.8 - 1.2 MPa, control the water-gas volume ratio at 1:(3 - 5), the cooling rate ≥ 80 °C / s, so that the surface temperature of the forging drops to 250 - 300 °C within 8 - 12 seconds, and obtain a fine-grained forging blank with a grain size grade ≥ 8;

[0139] S4, Composite Quenching: Heat the forging blank obtained in step S3 to 940 °C and hold for 10 min, then perform water quenching to 150 - 180 °C in a way that the length direction is perpendicular to the water surface. The single water quenching time is 6 - 20 s; the number of continuous water quenching is 1 time. Use an infrared temperature detector to monitor the temperature, and the probe measurement tilt angle is 120 - 150°; the first water quenching temperature ≤ 300 °C, the second water quenching temperature is 190 °C; after each water quenching, air cool to 200 - 230 °C and then put it into silicone oil, the temperature of the quenching medium is 70 - 80 °C, and the distance from the steel cross-section to the water surface > 10 mm;

[0140] S5, Aging Treatment: Place the quenched part obtained in step S4 in silicone oil at 170 °C and hold for 6 min, then heat it to 250 °C and hold for 10 min, and then water quench to room temperature to obtain the alloy.

[0141] Note: The calculation method of the partitioning time in the above Examples 1 - 9 and Comparative Examples 1 - 2 is as follows:

[0142] Boundary Conditions:

[0143] The flux is continuous at the martensite / austenite interface, and no carbide precipitates (Si inhibits cementite)

[0144] Diffusion Formula:

[0145]

[0146] D = 2.0×10 -5 e(-(148000 / 8.314×623) = 3.1×10 -1 7m 2 / S

[0147] Diffusion distance:

[0148] X1 = √Dt = √3.1×10-17×350 ≈ 10.5×10 -7 m = 105nm

[0149] X2 = √Dt = √3.1×10-17×1800 ≈ 2.4×10 -7 m = 240nm

[0150] When the partitioning time is 6 minutes, the distance greater than the thin-film-like RA of the microstructure is <100 nm. The conservative method takes 10 min.

[0151] Test example

[0152] The properties of the alloys prepared in the above Examples 1-9 and Comparative Examples 1-2 were tested, and the test results are shown in Table 1 below.

[0153] Table 1 Test results of the properties of the alloys prepared in Examples 1-9 and Comparative Examples 1-2

[0154]

[0155] Reference Figure 1 As shown, from the microstructure diagrams of Example 1 and Comparative Example 1, it can be seen that the nano-TiC in Comparative Example 1 precipitated significantly, while Example 1 significantly avoided the precipitation of coarse carbides. Reference Figure 2 As shown, Examples 1-9 have excellent tensile properties. Reference Figure 3 As shown, the Charpy impact fracture morphology diagrams of Examples 1-9 show that the specimens have excellent impact resistance. Reference Figure 4 As shown, the impact wear morphology diagram of Comparative Example 1 shows that there are large areas of spalling and cracks, while there are very few spalling and cracks in Example 1. Reference Figure 5 and Figure 6 As shown, the XRD residual stress test of Example 1 shows that the residual stress < 100 Mpa; for the steel specimens with the same composition, the residual stress of Comparative Example 1 at different quenching partitioning times > 600 Mpa.

[0156] From the above test results, it can be seen that the application examples 1-9 have obvious advantages in comprehensive performance compared with the comparative examples 1-2. This is mainly because in this application, the dosages of various elements and the mutual limiting ratios between the elements are optimized and defined simultaneously, and the process of preparation and synthesis is optimized and innovated. This is the result of the combined action of matching and defining various parameters in the process for the components of the formula. While in comparative examples 1-2, because the technical solutions defined in this application are not adopted, obvious disadvantages appear in the above performance tests, which further proves the necessity of the technical solutions defined in this application for the technical effects and solving technical problems of this application.

[0157] All technical features in this embodiment can be modified in appearance according to actual needs.

[0158] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention can also be implemented in other ways. Any obvious replacement without departing from the concept of the technical solution of the present invention is within the protection scope of the present invention.

Claims

1. A multiphase composite strengthened alloy for wear parts of construction machinery, characterized in that: The chemical composition of the alloy by weight percentage includes: C: 0.3 - 0.6%, Si: 2.8 - 3.7%, Mn: 0.1 - 0.9%, Cr: 0.2 - 0.5%, Mo: 0.02 - 0.05%, Ti: 0.09 - 0.13%, B: 0.001 - 0.003%, Al: 0.01 - 0.03%, the balance being Fe and unavoidable impurities; wherein, the C / Si mass ratio = 0.09 - 0.19; the Ti / N mass ratio = 3.5 - 4.0; the total content of Mn + Cr ≤ 1.1%.

2. The multiphase composite strengthened alloy for wearing parts of construction machinery according to claim 1, characterized in that: The matrix metallographic structure of the alloy contains martensite, secondary martensite, bainite and retained austenite, wherein the alloying elements Cr, Si, Mn, Mo are dissolved in the matrix, and the carbide is spherical TiC with a size of 10 - 30 nm.

3. The multiphase composite strengthening alloy for wearing parts of construction machinery according to claim 1, characterized in that: The yield strength of this alloy is ≥1766 MPa; the tensile strength is ≥2000 MPa; the Vickers hardness is ≥560 HV; the V-notch impact energy at 20 °C is ≥20 J / cm 2 ; the volume fraction of retained austenite is ≥20%.

4. A method for gradient-controlled preparation of a multiphase composite strengthened alloy for wear-prone parts of construction machinery according to any one of claims 1-3, characterized in that: It includes the following steps: S1, melting and casting treatment: Heat each element to 1550 - 1590 °C in a vacuum induction melting furnace under argon protection according to the formula ratio to melt the steel liquid. During casting, use a copper mold for rapid cooling, control the solidification rate ≥ 35 °C / s, and obtain an ingot with a cross-sectional size of 180 mm × 45 mm; S2, gradient forging treatment: Place the ingot obtained in step S1 in a gradient heating furnace, heat it to 1150 - 1200 °C at a rate of 120 - 150 °C / h, introduce a N2 / H2 mixed gas with a volume ratio of 4:1, hold for 3 - 6 hours and then perform four-way alternating forging. The single-pass deformation amount is 20 - 25%, the cumulative forging ratio ≥ 4.5, and in the final forging stage, control the temperature of the billet core at 800 - 880 °C by laser temperature measurement; S3, temperature-controlled cooling: Immediately perform water mist cooling after final forging, with a cooling rate ≥ 80 °C / s, so that the surface temperature of the forging drops to 250 - 300 °C within 8 - 12 seconds, and obtain a fine-grained forging blank with a grain size grade ≥ 8; S4, composite quenching: Heat the forging blank obtained in step S3 to 900 - 950 °C and hold for 25 - 35 min, perform water quenching to 150 - 180 °C in a way that the length direction is perpendicular to the water surface. The temperature of the quenching medium is 70 - 80 °C, and the distance from the steel cross-section to the water surface > 10 mm; S5, aging treatment: Place the quenched part obtained in step S4 in silicone oil at 150 - 180 °C and hold for 6 min, then heat it to 350 - 400 °C and hold for 10 - 30 min and then water quench to room temperature.

5. The gradient controllability preparation method of a multiphase composite strengthened alloy for wearing parts of construction machinery according to claim 5, characterized in that: During melting in step S1, the initial grain size ≤ 50 μm.

6. The gradient controllable preparation method of a multiphase composite strengthened alloy for wearing parts of construction machinery according to claim 5, characterized in that: During four-way alternating forging in step S2, the forging direction circulates in the order of X → Y → Z → diagonal direction, and the deviation of the deformation amount in each direction ≤ 3%.

7. The gradient controllability preparation method of a multiphase composite strengthened alloy for wear parts of construction machinery according to claim 5, characterized in that: In step S3, the water mist cooling uses an adjustable annular nozzle array, the atomizing water pressure is maintained at 0.8 - 1.2 MPa, and the water-gas volume ratio is controlled at 1:(3 - 5).

8. The gradient controllable preparation method of a multiphase composite strengthened alloy for wear parts of construction machinery according to claim 5, characterized in that: The water quenching process parameters in step S4 satisfy: the single water quenching time is 6 - 20 s; the number of continuous water quenching times is 2 - 4 times; the first water quenching temperature ≤ 300 °C, the second water quenching temperature ≥ 200 °C; after each water quenching, air cool to 200 - 230 °C and then put it into silicone oil.

9. The gradient controllable preparation method of a multiphase composite strengthened alloy for wearing parts of construction machinery according to claim 5, characterized in that: In the water quenching process of step S4, use an infrared temperature detector to monitor the temperature, and the probe measurement tilt angle is 120 - 150°.

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