Ni-coated particle reinforced high-strength and high-toughness steel and preparation method thereof

Abstract

The invention belongs to the field of high-strength and high-toughness steel, and particularly relates to Ni-coated particle reinforced high-strength and high-toughness steel and a preparation method thereof.The Ni-coated particle reinforced high-strength and high-toughness steel is obtained by doping nickel-coated ceramic powder into molten steel smelted from a high-strength and high-toughness steel base material and finally conducting pouring and homogenizing heat treatment. According to the invention, the nickel-coated ceramic powder is doped in the high-strength and high-toughness steel base material, and only homogenization heat treatment is carried out during heat treatment, so that the alloy steel with the yield strength of greater than 1300MPa and the tensile strength of greater than 1500MPa can be obtained. And moreover, quenching cracks and welding cracks generated in the subsequent machining process of existing high-strength and high-toughness steel can be effectively reduced, and the cold and hot impact resistance of the steel is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-strength and high-toughness steel, and particularly relates to a Ni-coated particle reinforced high-strength and high-toughness steel and a preparation method thereof. BACKGROUND

[0002] High-strength and high-toughness steel generally refers to an alloy steel with a yield strength greater than 1300 MPa and a tensile strength greater than 1500 MPa. High-strength and high-toughness steel is widely used in military and civilian fields. In the military field, it is mainly used as a protective material for tanks, armored vehicles, etc. In the civilian field, it is mainly used in special protection fields such as armored cash transport vehicles, stability maintenance vehicles, and some automobile steels.

[0003] For example, Domax500 steel produced by Swedish Stell AB has a tensile strength greater than 1500 MPa and good toughness and impact protection performance. For example, 38Cr2Mo2VA type high-strength and high-toughness steel in China has a tensile strength of up to 1725 MPa and a conditional yield strength of 1530 MPa. In addition, there are 300M steel, D6AC steel, AF1410 steel, Aermet100 steel, etc.

[0004] The defects of the existing high-strength and high-toughness steels mainly lie in some problems in manufacturing, use and performance. For example, internal surface straight defect and quenching crack may occur in the production process. High-strength and high-toughness steel is prone to welding cracks in the welding process, and the toughness of the welded part is usually lower than that of the base material, which increases the complexity in manufacturing and use.

[0005] Adding ceramic powder (such as BN, AlN, SiC, BC) to high-strength steel is a strengthening item, but if it is directly added to the molten steel, firstly, agglomeration will occur, causing composition segregation; secondly, the wetting effect of the ceramic powder in the steel is not good, and after solidification, a brittle item will be formed, reducing the performance of the steel.

[0006] Based on this, the application is proposed. SUMMARY

[0007] The application aims to provide a Ni-coated particle reinforced high-strength and high-toughness steel and a preparation method thereof to solve the above problems.

[0008] A Ni-coated particle reinforced high-strength and high-toughness steel, which is obtained by doping nickel-coated ceramic powder into molten steel for high-strength and high-toughness steel base material and then through pouring and homogenization heat treatment.

[0009] Further improvement, the yield strength of the Ni-coated particle reinforced high-strength and high-toughness steel is greater than 1300 MPa, and the tensile strength is greater than 1500 MPa.

[0010] A preparation method of a Ni-coated particle reinforced high-strength and high-toughness steel, comprising the following steps:

[0011] Step S1, melting high-strength high-toughness steel base material by vacuum induction melting furnace, when the molten steel temperature in the vacuum induction melting furnace reaches 1600-1610℃, adding nickel-coated ceramic powder, the adding amount of nickel-coated ceramic powder is 8-14g / kg, after adding, homogenizing treatment is carried out by electromagnetic stirring, to obtain molten steel to be poured;

[0012] Step S2, pouring the molten steel to be poured into a cast iron mold with high-pressure water cooling, and rapidly cooling, the cooling speed should not be less than 100℃ / s, to obtain a cast ingot;

[0013] Step S3, homogenizing heat treatment is carried out on the cast ingot, vacuum heat treatment is adopted, the treatment temperature is 800-810℃, and the holding time is 3h; during the vacuum heat treatment, electromagnetic wave treatment is carried out on the cast ingot according to the vertical direction of pouring; after the homogenizing heat treatment, the Ni-coated particle reinforced high-strength high-toughness steel is obtained.

[0014] Further improvement, the high-strength high-toughness steel base material is one of 38Cr2Mo2VA steel, 300M steel, D6AC steel, AF1410 steel and Aermet100 steel.

[0015] Further improvement, the preparation method of the nickel-coated ceramic powder comprises the following steps:

[0016] Step P1, adding 200-300 mesh nickel powder into a stainless steel vacuum ball mill jar, the charging ratio is 40-80g / L, and the ball-to-material ratio is (15-20):1;

[0017] Step P2, the stainless steel vacuum ball mill jar is fully cleaned with alcohol, then vacuumized and filled with nitrogen, so that the pressure in the stainless steel vacuum ball mill jar reaches 0.1Mpa;

[0018] Step P3, the nickel powder is ball milled by the stainless steel vacuum ball mill jar, and the ball mill of the stainless steel vacuum ball mill jar adopts a planetary ball mill;

[0019] Step P4, after the nickel powder is ball milled, the air valve on the stainless steel vacuum ball mill jar is opened, and the stainless steel vacuum ball mill jar is left for 1.5-2h, then the nano ceramic particles are added, and the charging ratio is 20-30g / L;

[0020] The nano ceramic particles include but are not limited to BN, AlN, SiC, BC, etc;

[0021] Step P5, the stainless steel vacuum ball mill jar is vacuumized to a vacuum degree less than 0.01Mpa, and then ball milled;

[0022] After the ball milling is completed, the stainless steel vacuum ball mill jar is placed in a heat treatment furnace for heating, the heat treatment furnace is heated to 350-360℃, and the stainless steel vacuum ball mill jar is cooled to room temperature with the heat treatment furnace, the air valve on the stainless steel vacuum ball mill jar is opened to break the vacuum, and the powder in the stainless steel vacuum ball mill jar is taken out after standing for 40-60 min, to obtain the nickel-coated ceramic powder.

[0023] Further improvement, in step P1, the grinding balls are stainless steel round balls; the grinding balls are divided into large balls, medium balls, small balls and micro balls, the diameter of the large balls is 12 mm, the proportion of the large balls is 30%, the diameter of the medium balls is 10 mm, the proportion of the medium balls is 15%, the diameter of the small balls is 8 mm, the proportion of the small balls is 15%, the diameter of the micro balls is 5 mm, and the proportion of the micro balls is 40%.

[0024] In step P4, the ball-to-material ratio is adjusted to 18:1, the proportion of large balls is adjusted to 25%, the proportion of medium balls is adjusted to 20%, the proportion of small balls is adjusted to 20%, and the proportion of micro balls is adjusted to 35%.

[0025] Further improvement, in step P3, the ball milling parameters are: the rotation speed is 600-700 r / min, the ball milling is stopped for 30 s every 20 min, then the ball milling is rotated in the opposite direction, and the ball milling time is 7-8 h.

[0026] In step P5, the ball milling parameters are set as follows: the rotation speed is 800-1000 r / min, the ball milling is stopped for 30 s every 15 min, then the ball milling is rotated in the opposite direction, and the ball milling time is 4-6 h.

[0027] Further improvement, in step P5, electrodes are installed on the two ends of the stainless steel vacuum ball mill jar, an electric brush is used for electrically connecting the electrodes and an external pulse power source, pulse electricity is input during the ball milling, the pulse power source adopts a rectangular square wave, the pulse voltage is 100 V, the frequency is 5-10 Hz, and the pulse width is 0.2 ms; the ball milling parameters are set as follows: the rotation speed is 1000 r / min, the ball milling is stopped for 30 s every 15 min, and the ball milling time is 2.5-3 h.

[0028] Further improvement, in step P1, the grinding balls are stainless steel oval balls, the ratio of the long axis to the short axis of the stainless steel oval ball is 1.6:1; the ball-to-material ratio is 20:1; the long axis of the large balls is 12 mm, the proportion of the large balls is 30%, the long axis of the medium balls is 10 mm, the proportion of the medium balls is 15%, the long axis of the small balls is 8 mm, the proportion of the small balls is 15%, the long axis of the micro balls is 5 mm, and the proportion of the micro balls is 40%.

[0029] Further improvement, in step P3, the ball milling parameters are: the rotation speed is 600 r / min, the ball milling is stopped for 30 s every 20 min, and the ball milling time is 5-5.5 h.

[0030] Compared with the prior art, the present application has the following beneficial effects:

[0031] 1、The present application adopts the form of Ni-coated powder to make nickel-coated ceramic powder into the alloy steel, and the nanoceramic particles are brought to the grain boundaries in the process of solid solution of Ni in the steel, solving the problem that the nanoceramic particles cannot be directly added. The nanoceramic particles at the grain boundaries form a characteristic of dispersion distribution, avoiding the occurrence of agglomeration, strengthening the grain boundaries, preventing the growth of the grains, refining the grains, and synergistically improving the strength and toughness of the steel.

[0032] 2、In the present application, a part of Ni3N with relatively high hardness and viscosity is formed by ball milling under nitrogen, and then the ceramic particles are ball milled to form a coating layer of Ni3N, and finally the coating layer of Ni is formed by releasing N at high temperature. By adopting reasonable ball milling parameters and the reaction brought by pulse discharge, and the "thermal explosion" phenomenon of the material surface brought by the ellipsoidal grinding balls under the effect of pulse discharge, the nanoscale ceramic particles with high hardness are "pressed into" the Ni to form a complete coating effect.

[0033] 3、In the present application, by doping nickel-coated ceramic powder into the high-strength and high-toughness steel base material, only homogenization heat treatment is performed during heat treatment, and an alloy steel with a yield strength greater than 1300 MPa and a tensile strength greater than 1500 MPa can be obtained. And it can also effectively reduce the quenching cracks and welding cracks generated in the subsequent processing process of the existing high-strength and high-toughness steel, and improve the cold and hot impact resistance of the steel. DETAILED DESCRIPTION

[0034] The present application will be further described in detail through specific examples.

[0035] Example 1

[0036] Step 1, add 200 mesh nickel powder into a stainless steel vacuum ball mill tank, the charge ratio (the ratio of the added nickel powder to the volume of the stainless steel vacuum ball mill tank) is 80 g / L, and the ball-to-material ratio (the mass ratio between the grinding balls and the nickel powder) is 20:1; wherein the grinding balls are divided into large balls, medium balls, small balls and micro balls, the diameter of the large balls is 12 mm, the large ball ratio (the percentage of the mass of the large balls to the total mass of the grinding balls) is 30%, the diameter of the medium balls is 10 mm, the medium ball ratio (the percentage of the mass of the medium balls to the total mass of the grinding balls) is 15%, the diameter of the small balls is 8 mm, the small ball ratio (the percentage of the mass of the small balls to the total mass of the grinding balls) is 15%, and the diameter of the micro balls is 5 mm, the micro ball ratio (the percentage of the mass of the micro balls to the total mass of the grinding balls) is 40%.

[0037] Step 2, the stainless steel vacuum ball mill tank is cleaned with alcohol, and then is vacuumized and filled with nitrogen to make the pressure in the stainless steel vacuum ball mill tank reach 0.1 Mpa.

[0038] Step 3, the nickel powder is ball milled in the stainless steel vacuum ball mill tank, and the ball mill of the stainless steel vacuum ball mill tank adopts a planetary ball mill, and the ball milling parameters are as follows: the rotating speed is 600 r / min, the ball milling is stopped for 30 s every 20 min, and then the ball milling is rotated in the opposite direction, and the ball milling time is 7-8 h.

[0039] Step 4, after the ball milling of the nickel powder is completed, the air valve on the stainless steel vacuum ball mill tank is opened, and the stainless steel vacuum ball mill tank is left to stand for 1.5-2 h to make the nitrogen in the stainless steel vacuum ball mill tank be exhausted, and then the stainless steel vacuum ball mill tank is opened, and then the nano ceramic particles are added, the nano ceramic particles are BN, and the feeding ratio is 30 g / L; the ball-to-material ratio is adjusted to 18:1, the large ball ratio is adjusted to 25%, the medium ball ratio is adjusted to 20%, the small ball ratio is adjusted to 20%, and the micro ball ratio is adjusted to 35%.

[0040] Step 5, the stainless steel vacuum ball mill tank is vacuumized, and the vacuum degree reaches less than 0.01 Mpa. The ball milling parameters are set as follows: the rotating speed is 1000 r / min, the ball milling is stopped for 30 s every 15 min, and then the ball milling is rotated in the opposite direction, and the ball milling time is 4-6 h.

[0041] Step 6, after the ball milling is completed, the stainless steel vacuum ball mill tank is put into a heat treatment furnace for heating, the heat treatment furnace is heated to 350-360℃, and the heat treatment furnace is kept at this temperature for 45 min, and then the stainless steel vacuum ball mill tank is cooled to room temperature with the heat treatment furnace, the air valve on the stainless steel vacuum ball mill tank is opened to break the vacuum, and the stainless steel vacuum ball mill tank is left to stand for 40-60 min, and then the powder in the stainless steel vacuum ball mill tank is taken out, and the nickel-coated ceramic powder is obtained and is ready for use.

[0042] Step 7, a vacuum induction melting furnace is used to melt high-toughness steel (for example, 38Cr2Mo2VA type high-toughness steel, and the chemical components are as follows: C: 0.36-0.41%; Si: 0.17-0.37%; Mn: 0.5-0.8%; Cr: 1.7-2.1%; Mo: 1.9-2.1%; V: 0.45-0.6%; and the rest is Fe), and when the temperature of the molten steel in the vacuum induction melting furnace reaches 1600-1610℃, the nickel-coated ceramic powder prepared by the above method is added, and the addition amount of the nickel-coated ceramic powder (the ratio of the nickel-coated ceramic powder to the molten steel) is 14 g / kg, and then the electromagnetic stirring is used to homogenize the molten steel to obtain the molten steel to be poured.

[0043] Step 8, the molten steel to be poured is poured into a cast iron mold with high-pressure water cooling, and the cooling speed is not less than 100℃ / s to obtain a cast ingot.

[0044] Step 9, the ingot is subjected to homogenization heat treatment, the vacuum heat treatment is adopted, the treatment temperature is 800-810℃, and the heat preservation time is 3h; during the vacuum heat treatment, electromagnetic waves are introduced into the ingot according to the vertical direction of pouring; after the homogenization heat treatment, product 1 is obtained.

[0045] Example 2

[0046] Step 1, 300 mesh nickel powder is added into a stainless steel vacuum ball mill tank, the feeding ratio (the ratio of the added nickel powder to the volume of the stainless steel vacuum ball mill tank) is 40g / L, and the ball-to-material ratio (the mass ratio between the milling balls and the nickel powder) is 15:1; wherein the milling balls are divided into large balls, medium balls, small balls and micro balls, the diameter of the large balls is 12mm, the large ball ratio (the percentage of the mass of the large balls to the total mass of the milling balls) is 30%, the diameter of the medium balls is 10mm, the medium ball ratio (the percentage of the mass of the medium balls to the total mass of the milling balls) is 15%, the diameter of the small balls is 8mm, the small ball ratio (the percentage of the mass of the small balls to the total mass of the milling balls) is 15%, the diameter of the micro balls is 5mm, and the micro ball ratio (the percentage of the mass of the micro balls to the total mass of the milling balls) is 40%.

[0047] Step 2, the stainless steel vacuum ball mill tank is thoroughly cleaned with alcohol, the stainless steel vacuum ball mill tank is evacuated, and then filled with nitrogen to make the pressure in the stainless steel vacuum ball mill tank reach 0.1Mpa.

[0048] Step 3, the stainless steel vacuum ball mill tank is used to ball mill the nickel powder, the ball mill of the stainless steel vacuum ball mill tank adopts a planetary ball mill, and the ball milling parameters are as follows: the rotation speed is 700r / min, the ball milling is stopped for 30s every 20min of ball milling, then the ball milling is rotated in the opposite direction, and the ball milling time is 7-8h.

[0049] Step 4, after the ball milling of the nickel powder is completed, the air valve on the stainless steel vacuum ball mill tank is opened, and the stainless steel vacuum ball mill tank is left to stand for 1.5-2h to make the nitrogen in the stainless steel vacuum ball mill tank exhaust, then the stainless steel vacuum ball mill tank is opened, and then nano ceramic particles are added, the nano ceramic particles are BN, and the feeding ratio is 20g / L; the ball-to-material ratio is adjusted to 28:1, the large ball ratio is adjusted to 25%, the medium ball ratio is adjusted to 20%, the small ball ratio is adjusted to 20%, and the micro ball ratio is adjusted to 35%.

[0050] Step 5, the stainless steel vacuum ball mill tank is subjected to vacuum treatment, and the vacuum degree reaches less than 0.01Mpa. The ball milling parameters are set as follows: the rotation speed is 800r / min, the ball milling is stopped for 30s every 15min of ball milling, then the ball milling is rotated in the opposite direction, and the ball milling time is 4-6h.

[0051] Step 6, after the ball milling is completed, the stainless steel vacuum ball mill pot is placed in a heat treatment furnace for heating, the heat treatment furnace is heated to 440-450℃, and the stainless steel vacuum ball mill pot is cooled to room temperature with the heat treatment furnace, the air valve on the stainless steel vacuum ball mill pot is opened to break the vacuum, and the powder in the stainless steel vacuum ball mill pot is taken out after standing for 40-60 min, to obtain the nickel-coated ceramic powder, which is ready for use.

[0052] Step 7, a vacuum induction melting furnace is used to melt high-toughness steel (such as 38Cr2Mo2VA type high-toughness steel), when the temperature of the molten steel in the vacuum induction melting furnace reaches 1640-1650℃, the nickel-coated ceramic powder prepared by the above method is added, the addition amount of the nickel-coated ceramic powder (the ratio of the nickel-coated ceramic powder to the amount of molten steel) is 8g / kg, and after the addition, electromagnetic stirring is used for homogenization treatment to obtain the molten steel to be poured.

[0053] Step 8, the molten steel to be poured is poured into a cast iron mold with high-pressure water cooling for rapid cooling, the cooling speed should not be less than 100℃ / s, and the ingot is obtained.

[0054] Step 9, the ingot is subjected to homogenization heat treatment, the vacuum heat treatment method is used, the treatment temperature is 910-920℃, and the holding time is 2h; during the vacuum heat treatment, electromagnetic waves are introduced into the ingot according to the vertical direction of pouring; after the homogenization heat treatment is completed, product 2 is obtained.

[0055] Example 3

[0056] Step 1, 200 mesh nickel powder is added to a stainless steel vacuum ball mill pot, the feeding ratio is 80g / L, the milling balls are stainless steel oval balls (the ratio of the long axis to the short axis is 1.6:1), and the ball-to-material ratio is 20:1; among them, the milling balls are divided into large balls, medium balls, small balls and micro balls, the long axis of the large balls is 12mm, the large balls account for 30%, the long axis of the medium balls is 10mm, the medium balls account for 15%, the long axis of the small balls is 8mm, the small balls account for 15%, and the long axis of the micro balls is 5mm, and the micro balls account for 40%.

[0057] Step 2, the stainless steel vacuum ball mill pot is thoroughly cleaned with alcohol, the stainless steel vacuum ball mill pot is evacuated, and then filled with nitrogen to make the pressure in the stainless steel vacuum ball mill pot reach 0.1Mpa.

[0058] Step 3, the stainless steel vacuum ball mill pot is used for ball milling of the nickel powder, the ball mill of the stainless steel vacuum ball mill pot adopts a planetary ball mill, the ball milling parameters are as follows: the rotation speed is 600r / min, the ball milling is stopped for 30s every 20min of ball milling, and the ball milling time is 5-5.5h.

[0059] Step 4, after the completion of the nickel powder ball milling, the vent valve on the stainless steel vacuum ball mill jar is opened, and the nitrogen gas in the stainless steel vacuum ball mill jar is allowed to escape for 1.5-2 hours. Then the stainless steel vacuum ball mill jar is opened, and nano-sized ceramic particles, which are BN, are added. The feeding ratio is 30 g / L. The ball-to-material ratio is still 20:1. The large ball ratio is 30%, the medium ball ratio is 15%, the small ball ratio is 15%, and the micro ball ratio is 40%.

[0060] Step 5, the stainless steel vacuum ball mill jar is vacuumized, and the vacuum degree is less than 0.01 Mpa. The two ends of the stainless steel vacuum ball mill jar are equipped with electrodes, and the electrodes are electrically connected with the external pulse power source through a brush. A pulse current is applied during the ball milling. The pulse power source adopts a rectangular square wave. The pulse voltage is 100 V, the frequency is 5-10 Hz, and the pulse width is 0.2 ms. The ball milling parameters are set as follows: the rotation speed is 1000 r / min, the ball milling is stopped for 30 s every 15 min, and the ball milling time is 2.5-3 h.

[0061] Step 6, after the completion of the ball milling, the stainless steel vacuum ball mill jar is placed in a heat treatment furnace for heating. The heat treatment furnace is heated to 350-360℃, and the stainless steel vacuum ball mill jar is cooled to room temperature with the heat treatment furnace. The vent valve on the stainless steel vacuum ball mill jar is opened to break the vacuum, and the powder in the stainless steel vacuum ball mill jar is taken out after standing for 40-60 min. Thus, the nickel-coated ceramic powder is obtained and ready for use.

[0062] Step 7, a vacuum induction melting furnace is used to melt high-toughness steel (such as 38Cr2Mo2VA type high-toughness steel). When the temperature of the molten steel in the vacuum induction melting furnace reaches 1600-1610℃, the nickel-coated ceramic powder prepared by the above method is added. The addition amount of the nickel-coated ceramic powder (the ratio of the nickel-coated ceramic powder to the amount of molten steel) is 14 g / kg. After the addition, electromagnetic stirring is used for homogenization treatment to obtain the molten steel to be poured.

[0063] Step 8, the molten steel to be poured is poured into a cast iron mold with high-pressure water cooling for rapid cooling, and the cooling speed should not be less than 100℃ / s to obtain an ingot.

[0064] Step 9, the ingot is subjected to homogenization heat treatment. The vacuum heat treatment method is used, the treatment temperature is 800-810℃, and the holding time is 3 h. During the vacuum heat treatment, electromagnetic waves are applied to the ingot according to the vertical direction of pouring. After the homogenization heat treatment, product 3 is obtained.

[0065] Comparative Example 1

[0066] In this example, the difference from Example 3 is that the pulse power source in Step 5 of this example does not release pulse current to the stainless steel vacuum ball mill jar during the ball milling, but only performs vacuum ball milling. The rest is the same.

[0067] Comparative Example 2

[0068] The example is compared with Example 3, the only difference is that the grinding ball used in the example is a stainless steel ball, and the rest is the same.

[0069] Comparative Example 3

[0070] The example is compared with Example 1, BN is replaced by SiC, and the rest is unchanged.

[0071] Example 4

[0072] The example is compared with Example 3, BN is replaced by SiC, and the rest is unchanged.

[0073] Example 5

[0074] The example is compared with Example 1, BN is replaced by AlN, and the rest is unchanged.

[0075] 1. Steel characterization test

[0076] 50 samples of the product are randomly taken, and the average value and variance of the yield strength and the average value of the tensile strength are measured.

[0077] 2. After heating the product, it is perforated by a perforating machine and finally processed into a steel pipe. The steel pipe is heated to 200℃ and naturally cooled to room temperature, and then put into liquid carbon dioxide for 30min, and such cold and hot treatment is carried out for 3 times, to obtain a cold and hot treated steel pipe sample. High-strength and high-toughness steel is prone to quenching cracks when making steel pipes, and is also prone to welding cracks during welding; therefore, if there are defects inside the cold and hot treated steel pipe sample obtained by the above treatment, the above defects can be enlarged, and cracks are more likely to occur. 50 samples are randomly taken, welded by plasma arc welding, after welding, whether cracks exist is detected by visual method and ultrasonic detection method, the number of samples with cracks is counted, and the crack rate = the number of samples with cracks / 50.

[0078] The test results are shown in Table 1:

[0079] Table 1

[0080] Mean value of yield strength / MPa Variance of yield strength Mean value of tensile strength / MPa Crack rate / % Example 1 1489 7254 1695 60 Example 2 1377 3967 1581 50 Example 3 1553 350 1722 2 Comparative Example 1 1462 6623 1604 46 Comparative Example 2 1443 8005 1629 52 Reference 1 1493 946 1667 42 Reference 2 981 557 1170 / Comparative Example 3 1128 9012 1308 / Example 4 1609 772 1838 8 Example 5 1399 603 1685 6

[0081] The present application adopts the form of Ni-coated powder to make nickel-coated ceramic powder, and the nanoceramic particles are brought to the grain boundary during the solid solution process of Ni in steel, solving the problem of direct addition. The nanoceramic particles at the grain boundary form a dispersed distribution, avoiding the occurrence of agglomeration, strengthening the grain boundary, preventing grain growth, and refining the grain, so that the strength and toughness of the steel are synergistically improved.

[0082] In the preparation process of the Ni-coated ceramic powder, if the ball milling is directly performed on the Ni and the ceramic powder, flaky Ni is formed due to the softness and high viscosity of the Ni material, which is not conducive to the formation of uniformly coated particles. In the present application, a part of the Ni3N with relatively high hardness and viscosity is first formed by ball milling under nitrogen, and then the ceramic particles are ball milled to form a coating layer of the Ni3N, and then the N is released at high temperature, and finally the coating layer of the Ni is formed. By adopting reasonable ball milling parameters and the reaction brought by the pulse discharge, and the "thermal explosion" phenomenon of the material surface brought by the ellipsoidal grinding ball under the pulse discharge effect, the further refinement and reaction of the material are promoted, the nanoscale ceramic particles with high hardness can be "pressed into" the Ni, and the complete coating effect is formed.

[0083] Reference 1 refers to a commercially available 38Cr2Mo2VA steel block (after heat treatment: 990-1010℃ oil quenching, 590-610℃ tempering twice for a total of 4h, air cooling), which is purchased from Dongguan Maochen Metal Material Co., Ltd.

[0084] Reference 2 refers to a commercially available 38Cr2Mo2VA blank (without heat treatment), which is a steel block obtained after the blank is treated by the heat treatment process of step 9 of the embodiment 3 of the present application. As can be seen from Table 1, if the 38Cr2Mo2VA blank is not subjected to special heat treatment, the strength and toughness of the blank are poor.

[0085] It is known in the art that the 38Cr2Mo2VA steel material is used to improve the hardness by using the secondary hardening mechanism when tempered at 500-600℃. However, defects such as distortion, cracks, and increased brittleness may occur during the tempering process. For example, rapid tempering may cause cracks, and tempering brittleness may also affect the material properties.

[0086] In the present application, by doping the nickel-coated ceramic powder into the high-strength and high-toughness steel base material, only homogenization heat treatment is performed during heat treatment, and an alloy steel with a yield strength greater than 1300MPa and a tensile strength greater than 1500MPa can be obtained. And it can also effectively reduce the quenching cracks and welding cracks generated in the subsequent processing of the existing high-strength and high-toughness steel, and improve the cold and hot impact resistance of the steel.

[0087] As can be seen from the embodiment 1 and the embodiment 2, although the yield strength and tensile strength indicators both reach the standard of high-strength and high-toughness steel, the yield strength variance and crack rate are abnormally high, indicating that the dispersion, precipitation effect and uniformity of the doped nickel-coated ceramic powder in the steel material are very poor.

[0088] As can be seen from the embodiment 3 and the comparative examples 1 and 2, the ellipsoidal grinding ball is necessary for the pulse discharge, and the effect brought by the ellipsoidal grinding ball is better, and finally the nickel-coated ceramic powder with better refinement effect and easier dispersion into the high-strength and high-toughness steel base material is formed.

[0089] From the comparative example 3, it can be seen that if the ceramic powder is SiC, it is more difficult to coat, and if the process of example 1 is used, the performance of the final alloy steel cannot reach the requirement of high-strength and high-toughness steel. However, if the process of example 3 is used, the performance of the final alloy steel can reach the requirement of high-strength and high-toughness steel.

[0090] The preferred embodiments of the present application have been described above with the preferred embodiments, but the present application is not limited to the above examples, and various modifications and changes can be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A Ni-coated particle-reinforced high-strength, high-toughness steel, characterized in that: Nickel-coated ceramic powder is added to molten steel made from high-strength and high-toughness steel substrate, and then cast and homogenized by heat treatment.

2. The Ni-coated particle-reinforced high-strength and high-toughness steel according to claim 1, characterized in that: The Ni-coated particle-reinforced high-strength and high-toughness steel has a yield strength greater than 1300 MPa and a tensile strength greater than 1500 MPa.

3. The method for preparing Ni-coated particle-reinforced high-strength and high-toughness steel according to claim 1, characterized in that, Includes the following steps: Step S1: High-strength and high-toughness steel substrate is smelted in a vacuum induction melting furnace. When the temperature of the molten steel in the vacuum induction melting furnace reaches 1600-1610℃, nickel-coated ceramic powder is added. The amount of nickel-coated ceramic powder added is 8-14g / kg. After adding, it is homogenized by electromagnetic stirring to obtain the molten steel to be poured. Step S2: Pour the molten steel to be poured into a high-pressure water-cooled cast iron mold for rapid cooling. The cooling rate shall not be less than 100℃ / s to obtain an ingot. Step S3: The ingot is subjected to homogenization heat treatment using vacuum heat treatment at a temperature of 800-810℃ for 3 hours. During the vacuum heat treatment, electromagnetic waves are introduced into the ingot in the direction perpendicular to the pouring. After the homogenization heat treatment is completed, the Ni-coated particle-reinforced high-strength and high-toughness steel is obtained.

4. The method for preparing Ni-coated particle-reinforced high-strength and high-toughness steel according to claim 3, characterized in that: The high-strength and high-toughness steel substrate is one of 38Cr2Mo2VA steel, 300M steel, D6AC steel, AF1410 steel, and Aermet100 steel.

5. The method for preparing Ni-coated particle-reinforced high-strength and high-toughness steel according to claim 3, characterized in that: The preparation method of the nickel-coated ceramic powder includes the following steps: Step P1: Add 200-300 mesh nickel powder into a stainless steel vacuum ball mill jar at a feeding ratio of 40-80 g / L and a ball-to-powder ratio of (15-20):

1. Step P2: The stainless steel vacuum ball mill jar is thoroughly cleaned with alcohol, then evacuated and filled with nitrogen to bring the pressure inside the stainless steel vacuum ball mill jar to 0.1 MPa. Step P3: The stainless steel vacuum ball mill jar is used to ball mill nickel powder. The ball mill in the stainless steel vacuum ball mill jar is a planetary ball mill. Step P4: After the nickel powder ball milling is completed, open the air valve on the stainless steel vacuum ball mill jar, let it stand for 1.5 to 2 hours, open the stainless steel vacuum ball mill jar, and then add nano-sized ceramic particles at a feeding ratio of 20 to 30 g / L. Step P5: Vacuum the stainless steel vacuum ball mill jar until the vacuum level is less than 0.01 MPa, and then perform ball milling. Step P6: After ball milling, place the stainless steel vacuum ball mill jar into a heat treatment furnace for heating. Heat the jar to 350-360°C and hold for 45 minutes. Let the stainless steel vacuum ball mill jar cool to room temperature with the heat treatment furnace. Open the vent valve on the stainless steel vacuum ball mill jar to break the vacuum. Let it stand for 40-60 minutes. Take out the powder from the stainless steel vacuum ball mill jar to obtain nickel-coated ceramic powder.

6. The method for preparing Ni-coated particle-reinforced high-strength and high-toughness steel according to claim 5, characterized in that: In step P1, the grinding balls are made of stainless steel spheres; the grinding balls are divided into large balls, medium balls, small balls and micro balls. The diameter of the large balls is 12mm, and the large balls account for 30% of the total. The diameter of the medium balls is 10mm, and the medium balls account for 15% of the total. The diameter of the small balls is 8mm, and the small balls account for 15% of the total. The diameter of the micro balls is 5mm, and the micro balls account for 40% of the total. In step P4, the ball-to-material ratio is adjusted to 18:1, the proportion of large balls is adjusted to 25%, the proportion of medium balls is adjusted to 20%, the proportion of small balls is adjusted to 20%, and the proportion of micro balls is adjusted to 35%.

7. The method for preparing Ni-coated particle-reinforced high-strength and high-toughness steel according to claim 6, characterized in that: In step P3, the ball milling parameters are: rotation speed of 600-700 r / min, stop ball milling for 30 seconds every 20 minutes of ball milling, then rotate the ball mill in the opposite direction, and the ball milling time is 7-8 hours; In step P5, the ball milling parameters are set as follows: rotation speed of 800-1000 r / min, stop for 30 seconds every 15 minutes of ball milling, then rotate the ball mill in the opposite direction, and the ball milling time is 4-6 hours.

8. The method for preparing Ni-coated particle-reinforced high-strength and high-toughness steel according to claim 5, characterized in that: In step P5, electrodes are installed at both ends of the stainless steel vacuum ball mill jar. The electrodes are electrically connected to the external pulse power supply using brushes. During ball milling, pulse current is applied. The pulse power supply uses a rectangular square wave with a pulse voltage of 100V, a frequency of 5-10Hz, and a pulse width of 0.2ms. The ball milling parameters are set as follows: rotation speed of 1000r / min, stopping for 30s every 15min of ball milling, and ball milling time of 2.5-3h.

9. The method for preparing Ni-coated particle-reinforced high-strength and high-toughness steel according to claim 8, characterized in that: In step P1, the grinding balls are stainless steel elliptical balls with a major axis to minor axis ratio of 1.6:1; the ball-to-material ratio is 20:1; the major axis of the large balls is 12mm, and the large balls account for 30%; the major axis of the medium balls is 10mm, and the medium balls account for 15%; the major axis of the small balls is 8mm, and the small balls account for 15%; and the major axis of the microballs is 5mm, and the microballs account for 40%.

10. The method for preparing Ni-coated particle-reinforced high-strength and high-toughness steel according to claim 9, characterized in that: In step P3, the ball milling parameters are: rotation speed of 600 r / min, ball milling is stopped for 30 seconds every 20 minutes, and the ball milling time is 5 to 5.5 hours.