A high-strength high-toughness bainite wear-resistant steel with tensile strength of 2100 MPa and a preparation method thereof

Abstract

The present application relates to a kind of high-strength high-toughness bainite wear-resistant steel of tensile strength 2100MPa level and its preparation method, belong to high-strength steel technical field, to solve at least one of the technical problems such as the strength, toughness, uniform elongation of existing high-strength wear-resistant steel, wear resistance, impact resistance, low cost, etc.Consideration.The wear-resistant steel in the present application has a lower bainite transformation temperature through specific component design, obtains small " hard phase " bainite ferrite, provides high strength, and retains a certain volume fraction of " soft phase " residual austenite, realizes high toughness and high plasticity;Obtain the design target of tensile strength ≥2100MPa, and keep the toughness and plasticity that meet engineering application requirements, and the uniform elongation is ≥7.0%, and U-shaped notch impact energy is ≥20J.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-strength steel, in particular to a high-strength high-toughness bainite wear-resistant steel with a tensile strength of 2100 MPa and a preparation method thereof. BACKGROUND

[0002] With the development of infrastructure construction and resource exploitation, the engineering machinery (such as excavator bucket teeth, loader blade, shield machine cutter), mine equipment (such as mine truck box, crusher liner, conveyor chute) and other fields are facing increasingly harsh working conditions. The key components of these equipment not only bear huge impact load and high stress, but also suffer from strong abrasive wear. Therefore, the strength, toughness, plasticity and wear resistance of the key structural materials are comprehensively required, and the ultra-high strength steel material with a tensile strength of 2100 MPa or more has become an urgent need in the industry.

[0003] At present, the widely used ultra-high strength wear-resistant steel adopts a martensite structure obtained by quenching + low-temperature tempering. The traditional martensite high-strength wear-resistant steel mainly relies on the addition of a large amount of Ni, Mo and other elements and the control of carbon content. This chemical composition design with high alloy cost, or the dependence on complex production process, limits its wide application. At the same time, the matching of its strength and toughness and plasticity is difficult to meet the current material requirements. Another technical route is to obtain nano bainite structure through isothermal quenching. The typical composition of this kind of steel is high C + Mn, Si, Cr, etc. After austenitizing, it is treated at 200-350℃ for isothermal treatment, to obtain fine bainite ferrite and achieve high strength. In order to realize bainite transformation at a lower temperature and match the strength and toughness, a large amount of expensive alloy elements such as Mo, Ni and Co are usually added, resulting in high material cost, or a complex heat treatment process is required, which is difficult to be applied on a large scale in cost-sensitive engineering machinery and mine equipment.

[0004] Therefore, it is of extremely important engineering application value and urgency to develop a new type of 2100 MPa grade wear-resistant steel with excellent strength, toughness and plasticity matching and controllable cost, and a high-efficiency preparation method thereof. SUMMARY

[0005] In view of the above analysis, the present application aims to provide a high-strength high-toughness bainite wear-resistant steel with a tensile strength of 2100 MPa and a preparation method thereof, to solve at least one of the technical problems of the existing high-strength wear-resistant steel, such as difficulty in matching strength, toughness and uniform elongation, and difficulty in matching wear resistance, impact resistance and low cost.

[0006] In a first aspect, the present application provides a high-strength high-toughness bainite wear-resistant steel with a tensile strength of 2100 MPa, and the composition of the wear-resistant steel is as follows in mass percent:

[0007] C: 0.66~0.88%, Mn: 1.55~1.85%, Cr: 0.50~0.68%, Si: 1.1~1.5%, Al: 0.9~1.0%, Ni: 0.30~0.45%, Mo: 0.15~0.65%, P≤0.02%, S≤0.01%, the balance being Fe and inevitable impurities.

[0008] Further, when C: 0.7~0.88%, then Ni: 0.40~0.45%, Mo: 0.35~0.45%.

[0009] Further, the microstructure of the wear-resistant steel comprises bainite ferrite and residual austenite.

[0010] Further, the volume fraction of the residual austenite in the microstructure is 15~25%.

[0011] In a second aspect, the present application provides a preparation method of the above-mentioned bainite wear-resistant steel with tensile strength of 2100MPa, comprising the following steps:

[0012] S1: alloy raw materials are vacuum smelted and cast to obtain a casting blank;

[0013] S2: the casting blank is forged, offline heat treated or online heat treated to obtain the wear-resistant steel.

[0014] Further, in S1, the vacuum degree of the vacuum smelting is ≤3Pa, the temperature is 1540~1580℃, and the smelting time is 40~60min.

[0015] Further, in S2, the offline heat treatment comprises austenitizing treatment and isothermal heat treatment.

[0016] Further, the temperature of the austenitizing treatment is 930~1000℃, and the holding time is 1.5~2 times of the diameter or thickness of the blank, wherein the holding time unit is min, and the diameter or thickness unit is mm.

[0017] The isothermal heat treatment is to cool the casting blank after austenitizing treatment to 220~240℃ and isothermally treat for 13~16h.

[0018] Further, the forging and online heat treatment further comprise rolling treatment, the temperature of the rolling treatment is 1050~1150℃, the finish rolling temperature is ≥930℃, and the thickness of the steel plate after rolling is 5~10mm.

[0019] Further, the online heat treatment comprises cooling the steel plate after rolling to 220~240℃ and isothermally treating for 13~16h.

[0020] Compared with the prior art, the application can achieve at least one of the following beneficial effects:

[0021] 1、The wear-resistant steel in the application has a lower bainite transformation temperature through specific component design, obtains fine "hard phase" bainite ferrite, provides high strength, and retains a certain volume fraction of "soft phase" residual austenite, realizes high toughness and high plasticity, obtains a design target of tensile strength ≥ 2100 MPa, and maintains toughness and plasticity meeting engineering application requirements, and uniform elongation ≥ 7.0%, and U-shaped notch impact energy ≥ 20 J.

[0022] 2、In the ultra-high strength wear-resistant steel, the bainite structure is a hard phase, which is obtained by isothermal transformation in a low-temperature bainite zone, has extremely high strength, and ensures that the strength level of the steel reaches 2100 MPa or more. Under the design of a high-carbon component, the residual austenite has high stability, plays a work hardening effect in the wear process, improves the hardness of the wear surface layer, and further improves the wear resistance. Thus, high strength + high work hardening performance is realized.

[0023] 3、The component system of the wear-resistant steel is suitable for different process requirements of forging and rolling. The processes adopted are conventional means of hot working and heat treatment, and special equipment is not required. In particular, different cooling modes such as air cooling and water cooling can be adopted after offline heat treatment or online heat treatment, the process adaptability is high, and it is conducive to industrial application.

[0024] In the application, the above technical solutions can be combined with each other to realize more preferred combination schemes. Other features and advantages of the application will be described in the subsequent specification, and some advantages will become apparent from the specification or be understood by implementing the application. The purposes and other advantages of the application can be realized and obtained from the contents specifically indicated in the specification and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings are included to provide a further understanding of the application and are incorporated herein and constitute a part of the application. The drawings illustrate embodiments of the application and, together with the description, serve to explain the principles of the application. In the drawings:

[0026] Figure 1 The microstructure diagram of the wear-resistant steel prepared for the embodiment 1 of the application;

[0027] Figure 2 The XRD diagram of the wear-resistant steel of the embodiment 2 of the application;

[0028] Figure 3 The microstructure diagram of the wear-resistant steel of the embodiment 3 of the application;

[0029] Figure 4 The tensile curve of the wear-resistant steel of the embodiment 4 of the application;

[0030] Figure 5 Tensile curve of the wear-resistant steel prepared for the inventive example 2;

[0031] Figure 6 Impact wear weight loss comparison of the wear-resistant steels prepared for the inventive example 1 and the comparative example 4. DETAILED DESCRIPTION

[0032] The preferred embodiments of the present application will be described in detail below with reference to the drawings, wherein the drawings constitute a part of the present application and serve to explain the principles of the present application together with the embodiments of the present application, but are not intended to limit the scope of the present application.

[0033] One specific embodiment of the present application discloses a high-strength high-toughness bainite wear-resistant steel with a tensile strength of 2100 MPa, and the components of the wear-resistant steel are as follows in percentage by mass:

[0034] C: 0.66~0.88%, Mn: 1.55~1.85%, Cr: 0.50~0.68%, Si: 1.1~1.5%, Al: 0.9~1.0%, Ni: 0.30~0.45%, Mo: 0.15~0.65%, P≤0.02%, S≤0.01%, and the balance being Fe and inevitable impurities.

[0035] Specifically, the roles of each component in the above high-strength high-toughness bainite wear-resistant steel are as follows:

[0036] C: In the present application, high carbon content is adopted to reduce the martensite start temperature of the steel to below 200℃, so as to ensure that the bainite phase change can be carried out at a relatively low temperature of 220~240℃, and obtain ultra-fine bainite ferrite structure. When the carbon content is too high, pearlite is easily formed during the cooling process, and more Mn, Mo and other alloy elements need to be added to inhibit the formation of pearlite, i.e. the alloy cost is increased. In the present application, the content of C element is 0.66~0.88%, for example, 0.66%, 0.68%, 0.70%, 0.72%, 0.74%, 0.76%, 0.78%, 0.80%, 0.82%, 0.84%, 0.86%, 0.88%.

[0037] Mn, Cr, Mo: the main purpose of matching addition is to improve the hardenability. Avoid the presence of pearlite structure during the isothermal process of high carbon wear-resistant steel cooling to bainite zone, deteriorate the strength and toughness. When the content of Mn element is high, composition segregation and other defects are prone to occur. When the content of Cr is too high, brittle carbides are prone to occur. Mo element is an expensive metal, and the cost will increase significantly when it is added in large quantities. In the present application, the content of Mn, Cr and Mo is 1.55-1.85% (for example, 1.55%, 1.60%, 1.65%, 1.70%, 1.75%, 1.80%, 1.85%), 0.50-0.68% (for example, 0.50%, 0.52%, 0.54%, 0.56%, 0.58%, 0.60%, 0.62%, 0.64%, 0.66%, 0.68%), 0.15-0.65% (for example, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%, 0.40%, 0.45%, 0.50%, 0.55%, 0.60%, 0.65%).

[0038] Si: suppresses the precipitation of cementite during bainite transformation process. So that the wear-resistant steel obtains bainite ferrite and residual austenite structure during bainite isothermal process. In the present application, the content of Si element is 1.1-1.5%, for example, 1.1%, 1.15%, 1.2%, 1.25%, 1.3%, 1.35%, 1.4%, 1.45%, 1.5%.

[0039] Al: on the one hand, the role of Al is similar to that of Si, which can effectively suppress the precipitation of cementite during bainite transformation process, on the other hand, the addition of Al element can promote bainite transformation, shorten the low temperature isothermal transformation time and improve the production efficiency. In the present application, the content of Al element is 0.9-1.0%, for example, 0.9%, 0.91%, 0.92%, 0.93%, 0.94%, 0.95%, 0.96%, 0.97%, 0.98%, 0.99%, 1%.

[0040] Ni: improves the stability of austenite, so that the residual austenite continuously transforms under external load, and the wear-resistant steel shows good work hardening performance. In addition, the addition of Ni helps to improve the toughness of high-strength wear-resistant steel. However, when the content of Ni is too high, the bainite transformation completion time will be greatly increased, which will affect the production rhythm. In the present application, the content of Ni element is 0.30-0.45%, for example, 0.30%, 0.32%, 0.34%, 0.36%, 0.38%, 0.40%, 0.42%, 0.44%, 0.45%.

[0041] S, P: the plasticity and toughness of the ultra-high strength steel are adversely affected, therefore, under the premise of not increasing the cost greatly, the lower S, P content should be controlled as much as possible. In the application, the content of S, P elements is controlled as S≤0.01%, P≤0.02% respectively.

[0042] It should be noted that, in order to avoid the pearlite structure in the high carbon steel cooling process and promote the bainite phase transition by adding a large amount of Ni, Mo, Co and other elements, in the application, the C-Mn-Cr-Mo-Ni matching part replaces the addition of Ni, Mo, Co and other elements, thereby reducing the alloy cost, and solving the contradiction between the performance and cost of the existing ultra-high strength wear-resistant steel.

[0043] Specifically, when C: 0.7~0.88%, then Ni: 0.40~0.45%, Mo: 0.35~0.45%.

[0044] It should be noted that when C≥0.7%, in order to ensure that the wear-resistant steel is still suitable for slow cooling production process such as air cooling, Mo≥0.35% is controlled to inhibit the generation of pearlite; at the same time, in order to ensure that high strength and high toughness matching is obtained under the condition of higher carbon design, Ni≥0.40% is controlled.

[0045] Specifically, the microstructure of the wear-resistant steel includes bainite ferrite and residual austenite.

[0046] Preferably, the volume fraction of residual austenite is 15~25%, for example, 15%, 16%, 18%, 20%, 22%, 24%, 25%.

[0047] It should be noted that in the ultra-high strength wear-resistant steel of the application, the bainite structure is a hard phase, which is obtained by isothermal in the low temperature bainite zone, and has very high strength, which ensures that the strength level of the steel reaches more than 2100 MPa. Under the condition of high carbon component design, the residual austenite has high stability, and in the wear process, it plays a work hardening effect, improves the wear surface hardness, and further improves the wear resistance. Thus, high strength + high work hardening performance is realized. When the volume fraction of residual austenite is higher than 25%, the strength level of the steel decreases, and the tensile strength is less than 2100 MPa.

[0048] It should be noted that the bainite of the wear-resistant steel in the application is composed of bainite ferrite (BF) and residual austenite (RA).

[0049] Specifically, the tensile strength of the wear-resistant steel is ≥2100 MPa, the uniform elongation is ≥7.0%, and the room temperature U-shaped notch impact energy is ≥20 J.

[0050] The wear-resistant steel in the application has a low bainite transformation temperature through specific component design, obtains fine "hard phase" bainite ferrite, provides high strength, and retains a certain volume fraction of "soft phase" residual austenite, realizes high toughness and high plasticity, obtains a design target of tensile strength ≥ 2100 MPa, and maintains toughness and plasticity meeting engineering application requirements, uniform elongation ≥ 7.0%, and U-shaped notch impact energy ≥ 20 J. High strength-high uniform elongation-high impact toughness not only ensures high wear resistance of the matrix, but also realizes high work hardening capacity and fracture resistance under impact and wear load. The strength-toughness-uniform elongation matching problem of the existing super-high strength wear-resistant steel is solved.

[0051] Another specific embodiment of the application discloses a preparation method of the above-mentioned 2100MPa-grade high-strength high-toughness bainite wear-resistant steel, comprising the following steps:

[0052] S1: alloy raw materials are vacuum smelted and cast to obtain a casting blank;

[0053] S2: the casting blank is forged and heat treated to obtain the wear-resistant steel.

[0054] Specifically, in S1, the vacuum degree of the vacuum smelting is ≤ 3 Pa, for example, 3 Pa, 2.9 Pa, 2.8 Pa, 2.7 Pa, 2.6 Pa, 2.5 Pa, 2.4 Pa, the temperature is 1540-1580℃, for example, 1540℃, 1545℃, 1550℃, 1555℃, 1560℃, 1565℃, 1570℃, 1575℃, 1580℃, and the smelting time is 40-60 min, for example, 40 min, 42 min, 44 min, 46 min, 48 min, 50 min, 52 min, 54 min, 56 min, 58 min, 60 min.

[0055] Specifically, in S1, the casting includes pouring, cooling, and annealing processes.

[0056] Preferably, the molten metal is injected into a mold, the billet diameter is 450-750 mm, for example, 450 mm, 470 mm, 490 mm, 510 mm, 530 mm, 550 mm, 570 mm, 590 mm, 610 mm, 630 mm, 650 mm, 670 mm, 690 mm, 710 mm, 730 mm, 750 mm; after pouring, the furnace is cooled for 25-35 min (for example, 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, 31 min, 32 min, 33 min, 34 min, 35 min), and then broken after 25-35 min of furnace cooling; after breaking, the mold is slowly cooled for 8-12 h (for example, 8 h, 8.5 h, 9 h, 9.5 h, 10 h, 10.5 h, 11 h, 11.5 h, 12 h) and demolded; the billet is sent into a furnace at 840-900°C (for example, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C) and held for 10-12 h (for example, 10 h, 10.2 h, 10.4 h, 10.6 h, 10.8 h, 11 h, 11.2 h, 11.4 h, 11.6 h, 11.8 h, 12 h), and then taken out after the furnace is cooled to below 400°C (for example, 395°C, 390°C, 385°C, 380°C, 375°C, 370°C, 365°C, 360°C).

[0057] It should be noted that the furnace is cooled for 25-35 min after pouring to prevent high-temperature oxidation and crack generation; the mold is slowly cooled for 8-12 h and demolded to ensure complete solidification, stress release, deformation prevention, and crack prevention; the billet is held in the furnace at 840-900°C to eliminate stress and homogenize the structure.

[0058] Specifically, in S2, the forging includes first-stage forging and / or second-stage forging.

[0059] In the first-stage forging, the heating temperature is 1180-1200°C, for example, 1180°C, 1182°C, 1184°C, 1186°C, 1188°C, 1190°C, 1192°C, 1194°C, 1196°C, 1198°C, 1200°C, the open-die temperature is ≥1050°C, for example, 1050°C, 1100°C, 1200°C, 1250°C, and the finish-die temperature is ≥850°C, for example, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C.

[0060] Preferably, the first stage forging is to form a round billet with a diameter of 220-250 mm (for example, 220 mm, 225 mm, 230 mm, 235 mm, 240 mm, 245 mm, 250 mm) or a square billet with a size of 220-250 (for example, 220 mm, 225 mm, 230 mm, 235 mm, 240 mm, 245 mm, 250 mm) x 220-250 mm (for example, 220 mm, 225 mm, 230 mm, 235 mm, 240 mm, 245 mm, 250 mm).

[0061] The heating temperature for the second stage forging is 1180-1200℃ (for example, 1180℃, 1182℃, 1184℃, 1186℃, 1188℃, 1200℃), the open forging temperature is ≥1050℃ (for example, 1050℃, 1100℃, 1150℃, 1200℃), the final forging temperature is ≥850℃ (for example, 850℃, 900℃, 950℃, 1000℃), and the second stage forging is to form a plate with a thickness of 15-30 mm (for example, 15 mm, 17 mm, 19 mm, 21 mm, 23 mm, 25 mm, 27 mm, 29 mm, 30 mm).

[0062] Specifically, in S2, the heat treatment is offline heat treatment or online heat treatment.

[0063] Specifically, in S2, the offline heat treatment includes austenitizing treatment and isothermal heat treatment.

[0064] It should be noted that when offline heat treatment is used, the forging includes first stage forging and second stage forging.

[0065] Preferably, the temperature of the austenitizing treatment is 930-1000℃ (for example, 930℃, 940℃, 950℃, 960℃, 970℃, 980℃, 990℃, 1000℃), the holding time (unit: min) is calculated according to 1.5-2 (for example, 1.5, 1.6, 1.7, 1.8, 1.9, 2) times the diameter or thickness (unit: mm) of the billet, and the isothermal heat treatment is to cool the cast billet after austenitizing treatment to 220-240℃ (for example, 220℃, 222℃, 224℃, 226℃, 228℃, 230℃, 232℃, 234℃, 236℃, 238℃, 240℃) and isothermally treated for 13-16 h (for example, 13 h, 13.2 h, 13.4 h, 13.6 h, 13.8 h, 14 h, 14.2 h, 14.4 h, 14.6 h, 14.8 h, 15 h, 15.2 h, 15.4 h, 15.6 h, 15.8 h, 16 h).

[0066] More preferably, the cooling method is air cooling, water cooling or mist cooling.

[0067] Specifically, when the heat treatment is an online heat treatment, the forging includes a first stage forging and / or a second stage forging, and after the forging, a rolling treatment is further included, and then the online heat treatment is performed.

[0068] Preferably, the temperature of the rolling treatment is 1050-1150℃, for example, 1050℃, 1060℃, 1070℃, 1080℃, 1090℃, 1100℃, 1110℃, 1120℃, 1130℃, 1140℃, 1150℃, the final rolling temperature is ≥930℃, for example, 930℃, 940℃, 950℃, 960℃, 970℃, 980℃, 990℃, 1000℃, and the thickness of the steel plate after rolling is 5-10mm, for example, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm, 10mm.

[0069] Preferably, the online heat treatment includes cooling the steel plate after rolling to 220-240℃, for example, 220℃, 222℃, 224℃, 226℃, 228℃, 230℃, 232℃, 234℃, 236℃, 238℃, 240℃, and isothermally treated for 13-16h, for example, 13h, 13.5h, 14h, 14.5h, 15h, 15.5h, 16h.

[0070] Preferably, the cooling is air cooling, water cooling or mist cooling.

[0071] It should be noted that the component system of the wear-resistant steel is suitable for different process requirements of forging and rolling. The processes adopted are conventional means of hot working and heat treatment, and special equipment is not required. In particular, different cooling methods such as air cooling and water cooling can be adopted after offline heat treatment or during online heat treatment, and the process adaptability is high, which is beneficial to industrial application.

[0072] The technical solutions of the present application will be further explained and described in combination with specific examples.

[0073] In the examples and comparative examples, the chemical components are shown in Table 1, and the balance is Fe and unavoidable impurities.

[0074] Table 1

[0075]

[0076] Example 1

[0077] The preparation method of the one kind of high-strength and high-toughness bainite wear-resistant steel with a tensile strength of 2100MPa in the embodiment includes the following steps:

[0078] S1: alloy raw materials are vacuum smelted and cast to obtain a casting blank;

[0079] The vacuum degree of the vacuum smelting is 2.7 Pa, the temperature is 1540 ℃, and the smelting time is 60 min. The casting comprises: injecting the smelted metal liquid into a casting mold, and the casting blank has a diameter of 450 mm; after pouring, the furnace is cooled for 25 min, then the vacuum is broken, and after the vacuum is broken, the mold is slowly cooled for 8 h and demolded; the casting blank is sent into a furnace at 840 ℃ for heat preservation for 10 h, and the furnace is cooled to below 380 ℃ and then taken out of the furnace;

[0080] S2: forging and offline heat treatment are performed on the casting blank to obtain the wear-resistant steel;

[0081] The forging comprises two stages. The first stage forging comprises: a heating temperature of 1180 ℃, an open forging temperature of 1080 ℃, and a final forging temperature of 860 ℃, and the forging is performed into a round blank with a diameter of 220 mm.

[0082] The second stage forging comprises: a heating temperature of 1180 ℃, an open forging temperature of 1080 ℃, and a final forging temperature of 865 ℃, and the forging is performed into a plate blank with a thickness of 15 mm.

[0083] The plate blank is subjected to offline heat treatment, and the offline heat treatment comprises austenitizing treatment and isothermal heat treatment. The austenitizing treatment is performed at a temperature of 980 ℃ for 25 min. The isothermal heat treatment is performed by water cooling the steel plate after austenitizing treatment to 220 ℃ and isothermal treatment for 16 h.

[0084] Embodiment 2

[0085] The embodiment provides a preparation method of a high-strength and high-toughness bainite wear-resistant steel with a tensile strength of 2100 MPa, which comprises the following steps:

[0086] S1: alloy raw materials are subjected to vacuum smelting and casting to obtain a casting blank.

[0087] The vacuum degree of the vacuum smelting is 1.9 Pa, the temperature is 1580 ℃, and the smelting time is 40 min. The casting comprises: injecting the smelted metal liquid into a casting mold, and the casting blank has a diameter of 750 mm; after pouring, the furnace is cooled for 35 min, then the vacuum is broken, and after the vacuum is broken, the mold is slowly cooled for 12 h and demolded; the casting blank is sent into a furnace at 900 ℃ for heat preservation for 12 h, and the furnace is cooled to below 390 ℃ and then taken out of the furnace.

[0088] S2: forging and offline heat treatment are performed on the casting blank to obtain the wear-resistant steel.

[0089] The forging comprises two stages. The first stage forging comprises: a heating temperature of 1200 ℃, an open forging temperature of 1100 ℃, and a final forging temperature of 863 ℃. The forging is performed into a square blank with a size of 250*250 mm.

[0090] Second stage forging: heating temperature 1200℃, open forging temperature 1100℃, final forging temperature 870℃, forging into a slab with thickness of 30mm:

[0091] The slab is subjected to offline heat treatment, which includes austenitizing treatment at a temperature of 930℃ for 60min and isothermal heat treatment by mist cooling the cast slab after austenitizing treatment to 230℃ and isothermal treatment for 15h.

[0092] Example 3

[0093] The preparation method of the high-strength high-toughness bainite wear-resistant steel with a tensile strength of 2100MPa in this embodiment comprises the following steps:

[0094] S1: alloy raw materials are subjected to vacuum smelting and casting to obtain a cast slab;

[0095] The vacuum smelting has a vacuum degree of 3Pa and a temperature of 1560℃, and the smelting time is 50min. The casting comprises: pouring the smelted metal liquid into a casting mold, and the cast slab has a diameter of 600mm; after pouring, the furnace is cooled for 30min, then the vacuum is broken, and the mold is slowly cooled for 10h after the vacuum is broken and the mold is removed; the cast slab is sent into a furnace at 870℃ for heat preservation for 11h, and then the furnace is cooled to below 390℃ and the cast slab is taken out of the furnace;

[0096] S2: the cast slab is subjected to forging, rolling and online heat treatment to obtain the wear-resistant steel;

[0097] The forging has a heating temperature of 1180℃, an open forging temperature of 1050℃ and a final forging temperature of 870℃. The forging is into a square billet with a size of 230×230mm;

[0098] The square billet is subjected to rolling treatment at a temperature of 1080℃ and a final rolling temperature of 950℃, and the thickness of the steel plate after rolling is 10mm. The online heat treatment comprises water cooling the rolled steel plate to 230℃ and isothermal treatment for 13h.

[0099] Example 4

[0100] The preparation method of the high-strength high-toughness bainite wear-resistant steel with a tensile strength of 2100MPa in this embodiment comprises the following steps:

[0101] S1: alloy raw materials are subjected to vacuum smelting and casting to obtain a cast slab;

[0102] The vacuum degree of the vacuum smelting is 2.5 Pa, the temperature is 1550 ℃, the smelting time is 45 min, the casting includes: pouring the smelted metal liquid into a casting mold, the casting blank has a diameter of 450 mm; after pouring, the casting blank is slowly cooled for 28 min after breaking the vacuum, and is slowly cooled for 9 h after breaking the vacuum and taking out the mold; the casting blank is sent into a furnace at 860 ℃ and is kept for 11 h, and is taken out after the furnace cooling to below 370 ℃.

[0103] S2: forging, rolling and online heat treatment are performed on the casting blank to obtain the wear-resistant steel.

[0104] The forging includes two stages. The first stage forging has a heating temperature of 1180 ℃, an open forging temperature of 1080 ℃ and a final forging temperature of 860 ℃, and the forging is performed to form a 220*250 mm square blank.

[0105] The second stage forging has a heating temperature of 1180 ℃, an open forging temperature of 1080 ℃ and a final forging temperature of 865 ℃, and the forging is performed to form a 30 mm thick plate blank.

[0106] The plate blank is subjected to rolling treatment, the temperature of the rolling treatment is 1130 ℃, the final rolling temperature is 940 ℃, the thickness of the steel plate after rolling is 5 mm, and the online heat treatment includes air cooling the steel plate after rolling to 240 ℃ and isothermal treatment for 16 h.

[0107] Embodiment 5

[0108] The embodiment provides a preparation method of a 2100 MPa-grade high-strength and high-toughness bainite wear-resistant steel, and the method comprises the following steps:

[0109] S1: alloy raw materials are subjected to vacuum smelting and casting to obtain a casting blank.

[0110] The vacuum degree of the vacuum smelting is 2.5 Pa, the temperature is 1550 ℃, the smelting time is 45 min, the casting includes: pouring the smelted metal liquid into a casting mold, the casting blank has a diameter of 450 mm; after pouring, the casting blank is slowly cooled for 28 min after breaking the vacuum, and is slowly cooled for 9 h after breaking the vacuum and taking out the mold; the casting blank is sent into a furnace at 860 ℃ and is kept for 11 h, and is taken out after the furnace cooling to below 370 ℃.

[0111] S2: forging, rolling and online heat treatment are performed on the casting blank to obtain the wear-resistant steel.

[0112] The forging includes two stages. The first stage forging has a heating temperature of 1180 ℃, an open forging temperature of 1080 ℃ and a final forging temperature of 860 ℃, and the forging is performed to form a 220*250 mm square blank.

[0113] The second stage forging has a heating temperature of 1180 ℃, an open forging temperature of 1080 ℃ and a final forging temperature of 865 ℃, and the forging is performed to form a 30 mm thick plate blank.

[0114] The slab is subjected to a rolling process at a temperature of 1130°C, a finish rolling temperature of 940°C, and a thickness of the steel plate after rolling of 5 mm, and the on-line heat treatment comprises air cooling the steel plate after rolling to 240°C and isothermal treatment for 16 h.

[0115] The method for preparing the wear-resistant steel of Comparative Example 1 is the same as that of Example 1.

[0116] The method for preparing the wear-resistant steel of Comparative Example 2 is similar to that of Example 2, except that in S2, the isothermal treatment is performed for 8 h.

[0117] The method for preparing the wear-resistant steel of Comparative Example 3 is similar to that of Example 3, except that in S2, the steel plate is water-cooled to 300°C.

[0118] The wear-resistant steel of Comparative Example 4 is a 4Cr5MoSiV1 steel in the prior art, which is prepared by using a method in the prior art.

[0119] Experimental Example 1

[0120] (1) The mechanical properties and microstructure of the wear-resistant steels prepared in each example and comparative example are shown in Table 2.

[0121] Table 2

[0122]

[0123] The microstructure of the wear-resistant steel of Example 1 is shown in Figure 1 , and the microstructure comprises bainite ferrite and residual austenite. The XRD of the wear-resistant steel of Example 2 is shown in Figure 2 , and the volume fraction of the residual austenite is calculated to be 19%. The microstructure of the wear-resistant steel of Example 3 is shown in Figure 3 , and the microstructure comprises bainite ferrite and residual austenite. The tensile curve of the wear-resistant steel of Example 4 is shown in Figure 4 .

[0124] As can be seen from Table 1 and Table 2, the component design of Comparative Example 1 does not meet the requirements of the present application, and the pearlite structure appears in the cooling process, and the tensile strength and uniform elongation are both reduced.

[0125] Comparative Example 2 has a shorter isothermal time compared with Example 2, so that the bainite transformation is not sufficient, and the stability of the austenite is lower, and the strength of the steel is lower than 2100 MPa. The tensile curve of the wear-resistant steel of Comparative Example 2 is shown in Figure 5 .

[0126] Comparative Example 3 has a higher isothermal temperature compared with Example 3, and the width of the bainite ferrite obtained is wider, and the tensile strength and uniform elongation are both reduced.

[0127] Comparative Example 4 is a prior high-strength steel 4Cr5MoSiV1, the alloy cost of which is significantly higher than that of the steel in the present application.

[0128] In order to compare the impact wear resistance of the high-strength and high-toughness wear-resistant steel in the present application with that of the prior steel 4Cr5MoSiV1, the wear weight loss of the two steels under impact conditions was compared by using a MLD-10 dynamic load impact abrasive wear testing machine.

[0129] The impact sample size was 10 mm x 10 mm x 30 mm, the impact load was 4.5 J, the impact frequency was 200 times per minute, and the impact time was 15 min and 45 min.

[0130] The test results are shown in Table 1. Figure 6 The wear weight loss of the two steels was similar. The high-strength and high-toughness wear-resistant steel in the present application was obtained under the condition of low alloy cost, and the impact wear resistance was comparable to that of the steel 4Cr5MoSiV1 with higher alloy cost.

[0131] The above description is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application.

Claims

1. A high-strength high-toughness bainite wear-resistant steel of tensile strength grade 2100 MPa, characterized in that, The wear-resistant steel component is in mass percentage: C: 0.66~0.88%, Mn: 1.55~1.85%, Cr: 0.61~0.68%, Si: 1.1~1.22%, Al: 0.9~1.0%, Ni: 0.30~0.45%, Mo: 0.15~0.65%, P≤0.02%, S≤0.01%, the balance being Fe and inevitable impurities; The preparation method of the wear-resistant steel comprises the following steps: S1: alloy raw materials are vacuum smelted and cast to obtain a casting blank; S2: the casting blank is forged, offline heat treated or online heat treated to obtain the wear-resistant steel. In S2, the offline heat treatment comprises austenitizing treatment and isothermal heat treatment; the temperature of the austenitizing treatment is 930~990℃, and the holding time is 1.5~2 times the diameter or thickness of the blank, wherein the holding time unit is min, and the diameter or thickness unit is mm; the isothermal heat treatment is to cool the casting blank after austenitizing treatment to 220~240℃ and isothermally treat for 13~16h; the cooling mode is air cooling, water cooling or mist cooling; In S2, the forging and online heat treatment further comprise rolling treatment, the temperature of the rolling treatment is 1050~1150℃, the finish rolling temperature is ≥930℃, and the thickness of the steel plate after rolling is 5~10mm; the online heat treatment comprises cooling the steel plate after rolling to 220~240℃ and isothermally treating for 13~16h; the cooling mode is air cooling, water cooling or mist cooling; The microstructure of the wear-resistant steel comprises bainite ferrite and residual austenite; the volume fraction of the residual austenite in the microstructure is 15~25%; The tensile strength of the wear-resistant steel is ≥2100MPa, the uniform elongation is ≥7.0%, and the room temperature U-notch impact energy is ≥20J.

2. The high-strength high-toughness bainite wear-resistant steel of grade 2100 MPa in tensile strength according to claim 1, characterized by the fact that, When C: 0.7~0.88%, then Ni: 0.40~0.45%, Mo: 0.35~0.45%.

3. A method of manufacturing the high-strength high- toughness bainite wear- resistant steel of grade 2100 MPa tensile strength according to claim 1 or 2, characterized in that, Comprise the following steps: S1: alloy raw materials are vacuum smelted and cast to obtain a casting blank; S2: the casting blank is forged, offline heat treated or online heat treated to obtain the wear-resistant steel.

4. The preparation method according to claim 3, characterized in that, In S1, the vacuum degree of the vacuum smelting is ≤3Pa, the temperature is 1540~1580℃, and the smelting time is 40~60min.

5. The preparation method according to claim 3, characterized in that, The temperature of the austenitizing treatment is 930~980℃, and the holding time is 1.6~2 times the diameter or thickness of the blank; The isothermal heat treatment is to cool the casting blank after austenitizing treatment to 230~240℃ and isothermally treat for 15~16h.

6. The preparation method according to claim 3, characterized in that, The forging and online heat treatment further comprise rolling treatment, the temperature of the rolling treatment is 1080~1150℃.

7. The preparation method according to claim 6, characterized in that, The online heat treatment comprises cooling the steel plate after rolling to 230~240℃.

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