A method for preparing layered high-toughness high-chromium cast iron parts

Abstract

The invention discloses a method for preparing a layered high-toughness high-chromium cast iron part, comprising the following steps: weighing a chemical element group including C, Cr, Mn, Si, Ni, Mo, and Fe according to production requirements, wherein the Cr content exceeds 12wt% and the Cr / C mass ratio is greater than 4; heating and smelting the alloy components to obtain a mixed melt; casting immediately after smelting, and after casting to form an ingot, keeping it warm at 1000-500°C for 1-15h to make the chromium diffusion uniform and improve segregation. Keeping the casting warm at a certain temperature after casting can reduce the stress formed inside the casting due to the fast surface cooling rate and slow internal cooling rate of large castings, reduce the cracks caused by internal stress of the casting, and reduce the scrap rate of the product. The product performance test results show that the hardness of the layered high-chromium cast iron products after heat treatment of the present invention is generally greater than 50HRC, and the carbide is evenly distributed, with an upper and lower deviation of ≤5HRC, and no cracking occurs.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy and relates to a method for preparing a high-chromium cast iron part. Background Art

[0002] Cast iron with a Cr content of more than 12% is usually called high chromium cast iron. The as-cast structure is usually austenite and its transformation products, eutectic carbides (M7C3) or (M 23 C6) type carbide.

[0003] When the Cr content in cast iron exceeds 12%, the M7C3 carbides in the organization are closely packed hexagonal structures, and their shapes are roughly rod-shaped or sheet-shaped and distributed on the matrix, which reduces the separation effect of the network carbides on the matrix and has a higher hardness. When the Cr / C ratio is greater than 5, a large amount of M7C3 carbides can be obtained. Although cast iron containing M7C3 carbides has certain wear resistance and high strength and is widely used in industry, its service life is short in harsh working environments.

[0004] High chromium cast iron is mainly used to manufacture wear-resistant castings due to its excellent wear resistance, and is used in many industrial fields. Liners are the main wear-resistant parts in ball mills or roller mills, mainly used to grind metallurgical ores, coal, refractory materials and other powders.

[0005] In the mining industry, cast iron has a relatively simple smelting process, low cost, and certain wear resistance, and is widely used. Therefore, mechanical equipment in complex environments usually uses cast iron as the base material.

[0006] Although traditional wear-resistant cast iron materials have a certain resistance to wear, their effect is too single. Some high-hardness wear-resistant materials have poor impact toughness and cannot resist high-intensity cyclic load wear, which will cause peeling.

[0007] Domestic researchers have refined the cast iron structure, changed the carbides, and improved the toughness and wear resistance of high chromium cast iron by adding various alloy elements, changing the heat treatment process, or adding a variety of modifiers to high chromium cast iron.

[0008] CN106319334A discloses a high-chromium cast iron alloy material and a manufacturing method and application thereof. A high-chromium cast iron alloy material is designed, in which various elements are combined to form a troostite matrix and carbide particles uniformly distributed in the matrix. After casting, a destabilization treatment is performed, and after destabilization, two tempering treatments are performed, thereby improving the toughness and wear resistance of the material.

[0009] CN109014045A discloses a method for preparing a high-chromium cast iron hammer head. The invention improves the hardenability and hardenability of small high-chromium cast iron materials through smelting, heating and melting, casting, quenching, tempering and other methods.

[0010] However, the preparation process of high chromium cast iron in the prior art still has the following disadvantages:

[0011] First, the various elements of high-chromium cast iron products cooperate to form the required matrix and carbide particles evenly distributed in the matrix. It is difficult to achieve uniform cooling rate in large-scale industrial production. The carbide particles are dispersed and evenly distributed in the matrix. In addition, high-chromium cast iron has the problem that the higher the hardness, the lower the toughness. The higher the hardness, the greater the internal stress.

[0012] Secondly, in the preparation method of high chromium cast iron, the wall thickness of the blank is relatively small, about 6 to 60 mm, which is difficult to meet the workpiece requirements of large-scale industrial production. Summary of the invention

[0013] In view of this, the purpose of the present invention is to provide a method for preparing a layered high-toughness high-chromium cast iron part. The product has a layered hard phase with high hardness and a layered matrix phase with a relatively soft texture. The layered hard phase and the soft phase are alternately combined, which can solve the problem that the matrix and the carbide particles in the matrix cannot be evenly distributed in industrial production, and the obtained layered structure can solve the problem that the higher the hardness of high-chromium cast iron, the lower the toughness. The material can improve its impact toughness while ensuring its strength, so that the whole has better comprehensive performance and can be better used in large-scale industrial production.

[0014] The inventor has continuously innovated and reformed through long-term exploration and attempts, as well as multiple experiments and efforts, to solve the above technical problems. The technical solution provided by the present invention is to provide a method for preparing a layered high-toughness high-chromium cast iron part, comprising the following steps:

[0015] S1: Weigh the alloy components

[0016] Weigh a group of chemical elements including C, Cr, Mn, Si, Ni, Mo, and Fe according to production requirements, wherein the Cr content exceeds 12wt% and the Cr / C mass ratio is greater than 4;

[0017] S2: Smelting

[0018] The alloy components are heated to below 1800°C for smelting to obtain a mixed melt;

[0019] S3: Heat preservation after casting

[0020] Casting is carried out immediately after smelting, and the casting temperature is greater than 1200°C. After the ingot is formed by casting, it is kept at 1000-500°C for 1-15 hours to make the chromium diffusion uniform and improve segregation.

[0021] The alloy composition is selected so that Cr / C is greater than 4, and during the solidification process, a high-hardness eutectic carbide (Fe, Cr)7C3 is formed in a roughly lath-shaped, rod-shaped, or sheet-shaped structure.

[0022] The distribution of chromium in high chromium cast iron is that chromium is mainly dissolved in austenite and chromium carbides, with a small amount distributed in other types of carbides and inclusions. When chromium is dissolved in the matrix, the stability of austenite is improved and the continuous cooling curve shifts to the right, thus enhancing the hardenability of the material. On the other hand, the (Cr, Fe)7C3 type high-hardness carbides formed by chromium and carbon enhance the hardness and wear resistance of high chromium cast iron, obtaining relatively good wear resistance.

[0023] Manganese, as an alloying element and a common element, has the function of expanding the austenite phase region and reducing the starting temperature of martensite transformation. It can increase the amount of primary austenite in high chromium cast iron and refine the grains, thus improving the hardness and hardenability of high chromium cast iron materials.

[0024] The content of silicon in high chromium cast iron cannot be too high. Most of the silicon element is dissolved in the matrix, which has a high strengthening effect on the matrix. During the solidification process of cast iron, silicon will gather on the grain boundaries of eutectic carbides, changing the morphology of eutectic carbides to a certain extent. As its content increases, the content of ferrite in the matrix will increase, increasing the soft phase required for the layered matrix in the present invention.

[0025] Nickel can be dissolved in austenite in large quantities and is not easy to form other forms of carbides. The combined effect of nickel and chromium can make austenite more stable. It also improves the hardenability of high chromium cast iron and strengthens the density of the matrix structure.

[0026] Part of molybdenum can participate in the formation of carbides, and the other part is dissolved in the matrix. It can also increase the eutectoid transformation temperature of cast iron, strengthen austenite, and improve the hardenability of high-chromium cast iron. When molybdenum works together with copper, nickel, chromium and other elements, it will greatly improve the hardenability.

[0027] According to one embodiment of the method for preparing layered high-toughness high-chromium cast iron parts of the present invention, in step S3, after casting to form an ingot, it is immediately placed in a preheated box-type heat treatment furnace for insulation to prevent the temperature of the ingot from cooling to room temperature and to ensure the time for uniform diffusion of chromium. The solidified ingot should be kept at a certain temperature to make the chromium diffusion as uniform as possible and improve segregation.

[0028] According to one embodiment of the method for preparing layered high-toughness high-chromium cast iron parts of the present invention, after the ingot is first kept warm, the following steps are also included:

[0029] S4: Heat treatment

[0030] Cool to the pearlite temperature range or bainite temperature range and keep warm for 1 to 15 hours;

[0031] Cool to room temperature or directly enter the subsequent process;

[0032] Heat to 1200-600°C, cool to the bainite or lath martensite transformation temperature range, and keep warm for 1-10 hours;

[0033] Cool to room temperature or directly enter the subsequent process;

[0034] Heat to 700-150℃ for tempering and keep warm for 1-10h.

[0035] The sample after heat preservation is rapidly cooled or furnace cooled or air cooled to room temperature, and the layered high-toughness high-chromium cast iron is obtained after cooling.

[0036] After the ingot is quenched, it is cooled to the bainite or lath martensite transformation temperature range to obtain a layered structure. Tempering is performed to obtain troostite or troostite or tempered martensite structure to improve the toughness of the structure.

[0037] According to an embodiment of the method for preparing layered high-toughness and high-chromium cast iron parts of the present invention, in step S4, the cooling method is furnace cooling or air cooling.

[0038] According to one embodiment of the method for preparing a layered high-toughness high-chromium cast iron part of the present invention, the alloy component is selected from:

[0039] The first chemical element group:

[0040] C: 2.1-4.02wt%, Cr: 12-30wt%, Mo: 0.1-3.0wt%, P<0.2wt%, S<0.3wt%, rare earth elements: 0-0.60wt%, the balance is Fe; P and S are inevitable impurities;

[0041] One or more of the second chemical element group:

[0042] Si: 0.1~3.0wt%, Mn: 0.1~3.0wt%, Cu: 0~1.4wt%, Ti: 0~0.2wt%, V: 0~6.0wt%, W: 0~6.0wt%, Al: 0~3.0wt %, Ni: 0~3.0wt%, B: 0~0.3wt%, Zn: 0~0.3wt%, Nb: 0~0.3wt%, Re: 0~0.3wt%, Ca: 0~0.3wt%, Sn: 0~0.3wt%.

[0043] Rare earth has the function of modifying inclusions, purifying molten iron and improving the interface condition between carbides and the matrix. It can significantly improve the morphology and distribution of eutectic carbides and significantly refine the matrix structure, thereby increasing the resistance to crack initiation and propagation.

[0044] Boron has a great influence on the hardness of high chromium cast iron. It can not only increase the hardness of carbides in high chromium cast iron to form harder compounds, but also dissolve into the matrix to increase the hardness of the matrix, greatly enhancing the matrix's ability to protect and support carbides.

[0045] According to one embodiment of the method for preparing layered high-toughness and high-chromium cast iron parts of the present invention, the rare earth elements include one or more of lanthanum, cerium, yttrium, praseodymium, neodymium, samarium, europium, and terbium.

[0046] According to one embodiment of the method for preparing a layered high-toughness high-chromium cast iron part of the present invention, the first chemical element group includes:

[0047] C: 2.4-4.0wt%, Cr: 14-25wt%, Mo: 0.5wt%, P<0.2wt%, S<0.3wt%, La: 0-0.60wt%, the balance is Fe; P and S are inevitable impurities;

[0048] According to one embodiment of the method for preparing a layered high-toughness high-chromium cast iron part of the present invention, the alloy component is selected from:

[0049] One or more of the second chemical element group:

[0050] Si: 0.13~2.0wt%, Mn: 0.5~1.8wt%, Cu: 0.2~1.0wt%, Ti: 0.02wt%, V: 0.1wt%, W: 0~6.0wt%, Al: 0~3.0wt%, Ni: 0.1 to 0.54wt%, B: 0 to 0.3wt%, Zn: 0 to 0.3wt%, Nb: 0 to 0.3wt%, Re: 0 to 0.3wt%, Ca: 0 to 0.3wt%, Sn: 0 to 0.3wt%.

[0051] Compared with the prior art, one of the above technical solutions has the following advantages:

[0052] a) The method for preparing layered high-toughness high-chromium cast iron parts of the present invention obtains the required lath-shaped and rod-shaped (Cr, Fe)7C3 type high-hardness carbides during high-temperature solidification molding. The hardness of Cr7C3 carbides is about 2300 HV, which is generally greater than the hardness of martensite and can ensure the high hardness of the obtained material. When the Cr / C of high-chromium cast iron is 4 to 8, stable M7C3 carbides can be obtained. The increase of carbides makes most of the carbon exist in the carbides, and a carbon-poor zone is generated around, forming an austenite matrix with low carbon content, which is beneficial to improve the impact toughness of the material; and the content of carbides increases and is evenly distributed, which improves the hardness of the material and improves the wear resistance accordingly. The increase of carbides also protects the matrix. Because the distance between carbides is reduced, the opportunity for abrasive particles to contact the matrix is ​​reduced, and the wear amount of the matrix is ​​reduced; when subjected to low impact loads, (Cr, Fe)7C3 plays a major role in resisting impact abrasive wear, and the matrix mainly plays a role in supporting carbides.

[0053] b) Keeping the castings at a certain temperature after casting can reduce the stress formed inside the castings due to fast surface cooling and slow internal cooling of large castings, reduce cracks caused by internal stress in the castings, and reduce the scrap rate of products.

[0054] c) The purpose of secondary isothermal treatment of the casting in the pearlite (P) interval or the bainite (B) interval is to prevent the genetic genes of austenite that appear after quenching and form the lath structure of P or B in advance.

[0055] d) Obtain the required layered bainite or lath martensite structure in the quenching stage, and obtain tempered troostite or tempered martensite structure in the tempering stage. The obtained structure is matched according to the product performance requirements so that the two hard phase structures of layered carbide and cementite are combined with the soft phase layered structure of ferrite to achieve the best performance. Layered high-toughness high-chromium cast iron parts have a high-hardness layered hard phase and a soft layered matrix phase. The layered hard phase and soft phase are alternately combined to improve the impact toughness (greater than 6J / cm2) of the material while ensuring high strength. 2 ), so that the overall comprehensive performance is better and can be better used in large-scale industrial production.

[0056] e) The present invention forms lath-shaped and chrysanthemum-shaped carbide hard phases and a softer matrix structure. The main carbides that resist wear are M7C3 and other types. In the prior art, carbides are brittle and easily break and fall off during wear. According to the process of the present invention, secondary hardening occurs after tempering, and secondary carbides are precipitated at the grain boundaries of the matrix structure. During the wear process, granular secondary carbides are dispersed at the grain boundaries of the matrix, which have a certain pinning effect, thereby increasing the resistance of the matrix to microscopic plastic deformation during wear and reducing weight loss due to wear. In addition, the layered structure formed by alternating soft and hard phases does not decrease but increases the overall hardness, wear resistance, and toughness of the material.

[0057] f) The initial hardness of the product prepared according to the process of the present invention is generally greater than 50HRC, which is lower than that of the conventional process, but its impact toughness is significantly greater than that of the conventional process, and the hardness of the product will be improved during subsequent use, showing the characteristic of becoming harder with use.

[0058] g) The product performance test results show that the hardness of the layered high chromium cast iron products after heat treatment of the present invention is generally greater than 50HRC, and the carbides are evenly distributed with an upper and lower deviation of ≤5HRC, and no cracking occurs. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 The present invention discloses a metallographic structure diagram of a layered high-toughness high-chromium cast iron part obtained by the method of the present invention. DETAILED DESCRIPTION

[0060] The following is a description with reference to the accompanying drawings and a specific embodiment.

[0061] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention.

[0062] Example 1

[0063] The method for preparing the layered high-toughness high-chromium cast iron part described in this embodiment comprises the following steps:

[0064] The alloy composition is selected as follows: C: 2.8wt%, Cr: 18.2wt%, Mn: 1.02wt%, Si: 0.13wt%, Mo: 0.5wt%, Ni: 0.54wt%, Cu: 0.2wt%, Ti: 0.02%, V: 0.1%, and the balance is Fe and inevitable impurities.

[0065] The alloy components are heated to 1800° C. for smelting to obtain a mixed melt.

[0066] After smelting, casting is carried out at a casting temperature of 1400°C. After casting to form an ingot, the temperature is reduced to 960°C and kept for 5 hours, then reduced to 700°C and kept for 6 hours, and then slowly cooled to room temperature.

[0067] Heat to 950℃ for quenching process and keep warm for 4h.

[0068] Reduce to 550℃, the bainite transformation temperature, keep warm for 8h, and air cool or furnace cool to room temperature.

[0069] Then raise the temperature to 450℃ for tempering and keep it for 6h.

[0070] After heat preservation, air cooling or furnace cooling to room temperature is performed to obtain layered high-toughness high-chromium cast iron parts.

[0071] The hardness of the layered high-toughness high-chromium cast iron product in this embodiment can reach 56.7HRC. After one week of service, the hardness of the product can reach 59.2HRC. The impact toughness is: 8.3J / cm 2 . Metallographic structure diagram Figure 1 shown.

[0072] Example 2

[0073] The method for preparing the layered high-toughness high-chromium cast iron part described in this embodiment comprises the following steps:

[0074] The alloy composition is selected as follows: C: 2.9wt%, Cr: 15wt%, Mn: 1.8wt%, Si: 1.45wt%, Mo: 0.5wt%, Ni: 0.5wt%, Cu: 1.0wt%, Ti: 0.02%, V: 0.1%, and the balance is Fe and inevitable impurities.

[0075] The alloy components are heated to 1800° C. for smelting to obtain a mixed melt.

[0076] After smelting, casting is carried out at a casting temperature of 1300°C. After casting to form an ingot, the temperature is reduced to 960°C and kept for 6 hours, then reduced to 650°C and kept for 6 hours, and then slowly cooled to room temperature.

[0077] Heat to 900℃ for quenching process and keep warm for 5h.

[0078] Reduce to bainite transformation temperature 450℃, keep warm for 8h, and air cool or furnace cool to room temperature.

[0079] After quenching, heat up to 500℃ for tempering and keep warm for 5h.

[0080] After heat preservation, air cooling or furnace cooling to room temperature is performed to obtain layered high-toughness high-chromium cast iron parts.

[0081] The hardness of the layered high-toughness high-chromium cast iron product in this embodiment can reach 55.4HRC. After one week of service, the hardness of the product can reach 58.66HRC. The impact toughness is: 9.6J / cm 2 .

[0082] Example 3

[0083] The method for preparing the layered high-toughness high-chromium cast iron part described in this embodiment comprises the following steps:

[0084] The alloy composition is selected as follows: C: 2.4wt%, Cr: 20.42wt%, Mn: 0.8wt%, Si: 1.95wt%, Mo: 0.5wt%, Ni: 0.5wt%, Cu: 0.5wt%, Ti: 0.02%, V: 0.1%, and the balance is Fe and inevitable impurities.

[0085] The alloy components are heated to 1800° C. for smelting to obtain a mixed melt.

[0086] After smelting, casting is carried out at a casting temperature of 1300°C. After casting to form an ingot, the temperature is reduced to 800°C and kept for 6 hours, then reduced to 600°C and kept for 8 hours, and then slowly cooled to room temperature.

[0087] Heat to 1000℃ for quenching process and keep warm for 3h.

[0088] Reduce to 400℃, the bainite transformation temperature, keep warm for 6h, and then air cool or furnace cool to room temperature.

[0089] After quenching, the temperature is raised to 350℃ for tempering and kept at this temperature for 6h.

[0090] After heat preservation, air cooling or furnace cooling to room temperature is performed to obtain layered high-toughness high-chromium cast iron parts.

[0091] The hardness of the layered high-toughness high-chromium cast iron product in this embodiment can reach 53.2HRC. After one week of service, the hardness of the product can reach 57.3HRC. The impact toughness is: 8.5J / cm 2 .

[0092] Example 4

[0093] The method for preparing the layered high-toughness high-chromium cast iron part described in this embodiment comprises the following steps:

[0094] Select the alloy composition: C: 2.8wt%, Cr: 14wt%, Mn: 1.5wt%, Si: 2wt%, Mo: 0.5wt%, Ni: 0.1wt%, La: 0.5wt%, Cu: 1.0wt%, Ti: 0.02%, V: 0.1%, and the balance is Fe and inevitable impurities.

[0095] The alloy components are heated to 1700° C. for smelting to obtain a mixed melt.

[0096] After smelting, casting is carried out at a casting temperature of 1400°C. After casting to form an ingot, the temperature is reduced to 750°C, kept warm for 8 hours, and then slowly cooled to 300°C and kept warm for 8 hours.

[0097] Heat to 960℃ for quenching process and keep warm for 4h.

[0098] Reduce the temperature to 350℃, keep warm for 8h, and directly enter the tempering process.

[0099] Heat up to 450℃ for tempering and keep warm for 6h.

[0100] After heat preservation, air cooling or furnace cooling to room temperature is performed to obtain layered high-toughness high-chromium cast iron parts.

[0101] The hardness of the layered high-toughness high-chromium cast iron product in this embodiment can reach 61.15HRC. After one week of service, the hardness of the product can reach 63.22HRC. The impact toughness is: 7.52J / cm 2 .

[0102] Example 5

[0103] The method for preparing the layered high-toughness high-chromium cast iron part described in this embodiment comprises the following steps:

[0104] Select the alloy composition: C: 4..02wt%, Cr: 25wt%, Mn: 0.5wt%, Si: 1wt%, Mo: 0.5wt%, Ni: 0.1wt%, Cu: 1.0wt%, Ti: 0.02%, V: 0.1%, the remainder is Fe, and inevitable impurities.

[0105] The alloy components are heated to 1800° C. for smelting to obtain a mixed melt.

[0106] After smelting, casting is carried out at a casting temperature of 1400°C. After casting to form an ingot, the temperature is reduced to 650°C, kept warm for 8 hours, and then slowly cooled to 450°C and kept warm for 6 hours.

[0107] Heat to 980℃ for quenching process, keep warm for 6h, then reduce to 200℃, keep warm for 6h, and directly enter the tempering process.

[0108] Heat to 300℃ for tempering and keep warm for 6h.

[0109] After heat preservation, air cooling or furnace cooling to room temperature is performed to obtain layered high-toughness high-chromium cast iron parts.

[0110] The hardness of the layered high-toughness high-chromium cast iron product in this embodiment can reach 64.8HRC. After one week of service, the hardness of the product can reach 66.4HRC. The impact toughness is: 6.89J / cm 2 .

[0111] It should be noted that all the insulation time in the above examples needs to be determined according to the thickness of the product. For castings with a thickness greater than 25 mm, the insulation time needs to be extended by one hour for every 25 mm increase in the thickness of the casting.

[0112] Example

[0113] Based on any one of Examples 1 to 5, the alloy components are replaced with the alloy components in any one of Examples 6 to 12 in Table 1 below.

[0114]

[0115]

[0116] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing layered high-toughness high-chromium cast iron parts, characterized in that: The steps include: S1: Weigh the alloy components Weigh the alloy components according to production requirements, wherein the alloy components include a first chemical element group and a second chemical element group: The first chemical element group: C: 2.1~4.02wt%, Cr: 12~30wt%, Mo: 0.1~3.0wt%, P<0.2wt%, S<0.3wt%, rare earth elements: 0~0.60wt%, Si: 0.1~3.0wt%, Mn: 0.1~3.0wt%, Cu: 0.1~1.4wt%, Ti: 0.05~0.2wt%; P and S are unavoidable impurities; The second chemical element group: V: 0~6.0wt%, W: 0~6.0wt%, Al: 0~3.0wt%, Ni: 0~3.0wt%, B: 0~0.3wt%, Zn: 0~0.3wt%, Nb: 0~0.3wt%, Re: 0~0.3wt%, Ca: 0~0.3wt%, Sn: 0~0.3wt%; The balance is Fe, and the Cr / C mass ratio is greater than 4; S2: Smelting The alloy components are heated to below 1800°C for smelting to obtain a mixed melt; S3: Heat preservation after casting Casting is carried out immediately after smelting, and the casting temperature is greater than 1200℃. After the ingot is cast, it is kept at 1000~500℃ for 1~15h to make the chromium diffusion uniform and improve segregation; S4: Heat treatment Cool to the pearlite temperature range or bainite temperature range and keep warm for 1~15h; Cool to room temperature or directly enter the subsequent process; Heat to 1200~600℃, cool to the bainite or lath martensite transformation temperature range, and keep warm for 1~10h; Cool to room temperature or directly enter the subsequent process; Heat to 700~150℃ for tempering and keep warm for 1~10h.

2. The method for preparing layered high-toughness high-chromium cast iron parts according to claim 1, characterized in that: In step S3, after the ingot is formed by casting, it is immediately placed in a preheated box-type heat treatment furnace for insulation to prevent the temperature of the ingot from cooling to room temperature and to ensure the time for uniform diffusion of chromium.

3. The method for preparing layered high-toughness high-chromium cast iron parts according to claim 1, characterized in that: In step S4, the cooling method is furnace cooling or air cooling.

4. The method for preparing layered high-toughness high-chromium cast iron parts according to claim 1, characterized in that: The rare earth element includes one or more of lanthanum, cerium, yttrium, praseodymium, neodymium, samarium, europium, and terbium.

5. The method for preparing layered high-toughness high-chromium cast iron parts according to claim 1, characterized in that: The first chemical element group includes: C: 2.4~4.0wt%, Cr: 14~25wt%, Mo: 0.5wt%, P<0.2wt%, S<0.3wt%, La: 0~0.60wt%, Si: 0.13~2.0wt%, Mn: 0.5~1.8wt%, Cu: 0.2~1.0wt%, Ti: 0.02wt%; P and S are unavoidable impurities.

6. The method for preparing layered high-toughness high-chromium cast iron parts according to claim 1, characterized in that: The second chemical element group: V: 0.1wt%, W: 0~6.0wt%, Al: 0~3.0wt%, Ni: 0.1~0.54wt%, B: 0~0.3wt%, Zn: 0~0.3wt%, Nb: 0~0.3wt%, Re: 0~0.3wt%, Ca: 0~0.3wt%, Sn: 0~0.3wt%.

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