High-toughness semi-steel for H-shaped steel rolling roller ring and preparation method of semi-steel roller

Abstract

The invention discloses a preparation method of high-toughness semi-steel for an H-shaped steel rolling roll collar and a semi-steel roll, and belongs to the technical field of steel rolling, the preparation method comprises the following steps: 1, preparing materials according to the chemical composition proportion of a semi-steel alloy material; 2, according to the total weight and the chemical component proportion of each furnace of semi-steel alloy, various raw materials and intermediate alloy are calculated and prepared respectively, and are added into a smelting furnace for smelting; thirdly, the temperature in the furnace is adjusted, the aluminum-cerium-rare earth intermediate alloy is added in batches, and heat preservation and standing are conducted; after standing is completed, the temperature of the molten steel is adjusted; 4, uniformly spreading an aluminum-cerium-rare earth intermediate alloy, an aluminum-yttrium intermediate alloy and a rare earth-silicon-calcium alterant at the bottom of the tundish, and pouring the molten steel into the tundish; fifthly, the semi-steel melt in the tundish is subjected to centrifugal casting; 6, normalizing and tempering the semi-steel casting; and finally, the semi-steel casting is subjected to high-temperature tempering treatment. The room-temperature impact absorbing energy of the semi-steel material reaches 20-28 J and is far higher than that of a traditional commercial semi-steel material.

Description

Technical Field

[0001] The invention belongs to the technical field of steel rolling, and particularly relates to a high-toughness semi-steel for H-beam rolling roller ring and a semi-steel roller and a preparation method thereof. Background Art

[0002] At present, my country is in the stage of high-quality development, and there is a huge demand for H-shaped steel with high dimensional accuracy and excellent comprehensive performance. H-shaped steel is mainly manufactured by rolling, so the toughness, wear resistance and fatigue resistance of the roller ring material are crucial. The carbon content of semi-steel material is 1.4%~2.3%. Semi-steel rollers not only have the high strength and toughness of cast steel rollers, but also have the good wear resistance of cast iron rollers. Semi-steel roller rings are usually used in the rough rolling stand and the front section of the finishing rolling of the plate and strip hot rolling mill, and are also widely used in the rough rolling and medium rolling stands for the production of steel, wire rods and bars. Among them, carbon and chromium are important elements for the formation of carbides in semi-steel rollers, which play an important role in improving the wear resistance of rollers. In order to improve the wear resistance of the rollers, it is often necessary to greatly increase the hardness of the material, which causes its impact toughness to decrease, which is easy to cause the surface of the roller to peel off or even break the roller, affecting the long-term service of the roller and the rhythm of steel rolling production. Therefore, improving the toughness of the roller material (generally measured by the impact absorption work) is a bottleneck problem faced by the industry. In view of this technical difficulty, it is particularly urgent to develop high-toughness semi-steel materials by optimizing chemical composition design and heat treatment process technology.

[0003] Chinese patent CN200910031123.0 discloses a patented technology of a semi-steel roller and its preparation method, which can improve the morphology and distribution uniformity of carbides and inhibit the segregation of alloy elements. However, its semi-steel material also contains a large amount of K and Na elements. On the one hand, these two elements are extremely active and difficult to accurately control during the production process, which increases the difficulty of process control; on the other hand, K and Na elements have low melting points. Under the harsh high temperature working conditions of the roller, these elements will melt, causing cracks to initiate and expand, making the roller surface peeling or even breaking.

[0004] The patented technology of US Patent US4165407A Adamite roll material for a rolling mill is characterized by low alloying component design, especially low Cr element, which is a key carbide-forming element in semi-steel materials. Although some other carbide-forming elements are added, the Cr content of no more than 0.8% still makes the semi-steel material of this patent invention have poor wear resistance due to insufficient carbide quantity.

[0005] Generally speaking, in the existing patented technologies, some mainly focus on the composition design with high carbon and noble metal element contents, resulting in high production costs; while others mainly focus on the composition design with high carbon and low alloy element contents, resulting in poor service performance of semi-steel materials. Therefore, designing more economical and reasonable chemical compositions and optimizing the heat treatment process to prepare semi-steel materials with low cost and high performance are of great significance for the high-quality development of the steel industry. Summary of the Invention

[0006] The present invention provides a high-toughness semi-steel for H-beam rolling roll rings and a preparation method thereof for semi-steel rolls, aiming to produce high-toughness semi-steel materials for H-beam rolling roll rings and rolls prepared from such materials. The specific method includes process steps such as raw material preparation, melting, refining and alloying, deoxidation and secondary alloying, standing, slag skimming, transferring to an intermediate ladle, centrifugal casting, mold opening, and heat treatment.

[0007] In order to achieve the above object, the technical solution adopted in this application is as follows: A high-toughness semi-steel for H-beam rolling roll rings, the chemical composition of the semi-steel roll in mass percentage is: C: 1.8% - 2.0%; Si: 0.4% - 0.8%; Mn: 1.1% - 1.4%; Cr: 2.3% - 2.8%; Ni: 0.6% - 1.0%; Mo: 0.2% - 0.5%; La: 50 ppm - 100 ppm; Ce: 50 ppm - 200 ppm; Y: 50 ppm - 150 ppm; the balance is Fe and impurities.

[0008] A further improvement of the technical solution of the present invention lies in that: the chemical composition of the semi-steel in mass percentage is: C: 1.8% - 2.0%; Si: 0.5% - 0.7%; Mn: 1.2% - 1.4%; Cr: 2.4% - 2.7%; Ni: 0.8% - 1.0%; Mo: 0.3% - 0.5%; La: 50 ppm - 80 ppm; Ce: 80 ppm - 150 ppm; Y: 50 ppm - 100 ppm; the balance is Fe and impurities.

[0009] A preparation method of a high-toughness semi-steel roll for H-beam rolling roll rings includes the following steps: Step 1, prepare a semi-steel alloy melt; Among them, the designed chemical composition ratio of the semi-steel alloy melt (mass fraction) is: C: 1.8% - 2.0%; Si: 0.4% - 0.8%; Mn: 1.1% - 1.4%; Cr: 2.3% - 2.8%; Ni: 0.6% - 1.0%; Mo: 0.2% - 0.5%; La: 50 ppm - 100 ppm; Ce: 50 ppm - 200 ppm; Y: 50 ppm - 150 ppm; the balance is Fe and impurities; Calculate the content of each raw material according to the total weight of each furnace smelting and the above composition range, respectively prepare the feeding amounts of scrap steel and master alloy materials, and perform secondary alloying according to the composition after melting; put in the aluminum cerium master alloy and let it stand for 20 minutes; then put in the aluminum cerium master alloy again and let it stand for 10 minutes; Skim the slag from the molten steel with qualified composition; Evenly sprinkle aluminum cerium, aluminum yttrium master alloy and rare earth silicon calcium modifier on the bottom of the pre-baked tundish; Pour the standing molten steel out of the furnace into the tundish; Step 2: Drain the molten steel in the tundish into a centrifugal casting mold to obtain a semi-steel centrifugal casting with dense structure.

[0010] Step 3: Open the mold and take out the centrifugal casting, first perform normalizing heat treatment; then perform low-temperature tempering heat treatment on the casting; finally perform high-temperature tempering heat treatment on the casting; obtain a finished semi-steel material with uniform structure.

[0011] A further improvement of the technical solution of the present invention lies in: in the said Step 1, the chemical composition ratio of the semi-steel material is designed as C: 1.8%-2.0%; Si: 0.5%-0.7%; Mn: 1.2%-1.4%; Cr: 2.4%-2.7%; Ni: 0.8%-1.0%; Mo: 0.3%-0.5%; La: 50ppm-80ppm; Ce: 80ppm-150ppm; Y: 50ppm-100ppm; the balance is Fe and impurities; prepare the semi-steel alloy melt according to the set composition, including the following steps: Step 1.1: Calculate and prepare raw materials such as ordinary scrap steel, ferrosilicon, ferromanganese, ferrochromium, ferromolybdenum, nickel plate, carburant, aluminum cerium, aluminum yttrium and rare earth silicon calcium modifier respectively according to the total weight of each furnace of aluminum alloy and the chemical composition ratio; Step 1.2: Add ordinary scrap steel, ferrosilicon, ferromanganese, ferrochromium, ferromolybdenum, nickel plate, carburant into the smelting furnace for melting respectively; after melting, perform composition detection, and perform secondary alloying according to the actual element content to make the composition of the molten steel meet the required range; Step 1.3: Adjust the temperature in the furnace to 1560-1580°C, put one-third of the aluminum cerium rare earth master alloy into the furnace, keep warm and stand for 20 minutes; Step 1.4: After standing, put one-third of the aluminum cerium rare earth master alloy into the furnace again, keep warm and stand for 10 minutes; Step 1.5: After standing, adjust the temperature of the molten steel to 1450-1480°C, and then skim the slag from the molten steel melt; Step 1.6: Bake the tundish at 700 °C, and then evenly sprinkle the remaining one-third of the aluminum-cerium rare earth master alloy, all of the aluminum-yttrium master alloy, and the rare earth silicon-calcium modifier on the bottom of the tundish. The composition of the modifier is (mass fraction) 31% Fe - 40% Si - 12% La - 12% Ce - 5% Ca; Step 1.7: Pour the molten steel after slag skimming in Step 1.5 into the tundish.

[0012] A further improvement of the technical solution of the present invention lies in: in the second step, centrifugal casting is performed on the semi-steel molten steel melt, including the following steps: Step 2.1: Set the rotational speed of the centrifugal mold to 450 revolutions per minute; Step 2.2: Pour the semi-steel melt in the tundish into the rotating mold.

[0013] A further improvement of the technical solution of the present invention lies in: in the third step, heat treatment is performed on the centrifugally cast semi-steel casting, including the following steps: Step 3.1: Perform normalizing heat treatment on the semi-steel casting using a stepped heat treatment system; first, put the semi-steel casting into the furnace at room temperature, heat it up with the furnace to 300 °C and hold for 4 hours; then heat it up to 700 °C and hold for 5 hours; finally, heat it up to 950 °C and hold for 10 hours; Step 3.2: Cool the semi-steel casting that has completed the normalizing heat treatment with the furnace to 480 °C, and then perform tempering treatment at this temperature, with the holding time being 5 hours; Step 3.3: Heat up the semi-steel casting that has completed the low-temperature tempering heat treatment in Step 3.2 with the furnace to 530 °C, and then perform high-temperature tempering treatment at this temperature, with the holding time being 15 hours; after the holding is completed, take it out of the furnace and air-cool it to room temperature.

[0014] Due to the adoption of the above technical solution, the beneficial effects obtained by the present invention are: Rare earth elements (RE) are added to the semi-steel material of the present invention. Rare earth elements are relatively active and can significantly purify the steel quality, deoxidize and desulfurize, modify inclusions, etc. in semi-steel, and can also spheroidize carbides in semi-steel. There are two ways to add rare earth in semi-steel. One is to add it in the form of master alloy, and the other is to add it in the form of rare earth silicon-calcium modifier.

[0015] In this application, the lanthanum (La) element is added in the form of a rare earth silicon calcium modifier, with a content of 50 ppm - 100 ppm; a part of the cerium (Ce) element is added in the form of a rare earth silicon calcium modifier, and the other part is added in the form of an aluminum-based master alloy. The aluminum-based master alloy is added three times, namely at the melting stage, before tapping, and at the bottom of the ladle, with one-third of the total amount added each time, and the total content is 50 ppm - 200 ppm; a large amount of research work has shown that heavy rare earth elements have a more significant effect on improving the properties of semi-steel. Therefore, the yttrium (Y) element is added in the form of an aluminum-based master alloy, and the addition method is bottom addition in the ladle, with a total content of 50 ppm - 150 ppm.

[0016] The material invented in this patent improves the toughness of the semi-steel material through a unique composition design, and the impact energy absorption at room temperature reaches 20 - 28 J. Moreover, in this invention, rare earth microalloying is achieved by adding rare earth in multiple steps, which can significantly purify the steel quality and improve the rare earth recovery rate; at the same time, by combining the joint action of light rare earth and heavy rare earth, the impact toughness of the semi-steel material is further improved. Description of the Drawings

[0017] Figure 1 It is the metallographic structure diagram of the semi-steel roll ring prepared by using Example 1 of the present invention; Figure 2 It is the metallographic structure diagram of the semi-steel roll ring prepared in the comparative example. Detailed Description of the Invention

[0018] The technical solutions of the present invention will be described in detail below in combination with the specific embodiments.

[0019] Example 1 The designed chemical composition ratio of the semi-steel alloy melt (mass fraction) is: C 1.9%, Si 0.7%, Mn 1.2%, Cr 2.6%, Ni 1.0%, Mo 0.3%, La 80 ppm, Ce 151 ppm, Y 79 ppm, and the balance is Fe and unavoidable impurities; ordinary scrap steel, ferrosilicon, ferromanganese, ferrochromium, ferromolybdenum, nickel plate, and carburant are respectively added to the melting furnace for melting. After melting, secondary alloying is carried out according to the actual element content; the temperature in the furnace is adjusted to 1560 °C, and one-third of the aluminum-cerium rare earth master alloy is added to the furnace, and it is kept warm and static for 20 minutes; after standing, another one-third of the aluminum-cerium rare earth master alloy is added to the furnace, and it is kept warm and static for 10 minutes; after standing, the temperature of the molten steel is adjusted to 1480 °C, and then the molten steel melt is skimmed; the tundish is baked at 700 °C, and then the remaining one-third of the aluminum-cerium rare earth master alloy, all of the aluminum-yttrium master alloy, and the rare earth silicon calcium modifier are evenly spread on the bottom of the ladle; the composition of the rare earth silicon calcium modifier is 31% Fe - 40% Si - 12% La - 12% Ce - 5% Ca by mass percentage.

[0020] Pour the molten steel into the tundish; then set the rotational speed of the centrifugal mold to 450 revolutions per minute, and pour the semi-steel melt in the tundish into the rotating mold; perform normalizing heat treatment on the semi-steel casting. First, put the semi-steel casting into the furnace at room temperature, heat it up to 300 °C with the furnace and hold for 4 hours; then heat it up to 700 °C and hold for 5 hours; finally, heat it up to 950 °C and hold for 10 hours; after the heat preservation is completed, cool the semi-steel casting with the furnace to 480 °C, and then hold it at this temperature for tempering treatment, with the holding time of 5 hours; after the heat preservation is completed, heat the semi-steel casting with the furnace to 530 °C, and then hold it at this temperature for high-temperature tempering treatment, with the holding time of 15 hours; after the heat preservation is completed, take it out of the furnace and air-cool it to room temperature. After testing, the tensile strength of the semi-steel is 856 MPa, and the impact energy absorbed at room temperature is 20.3 J measured by an impact specimen with a size of 10 mm * 10 mm.

[0021] Example 2 The designed chemical composition ratio of the semi-steel alloy melt (mass fraction) is: C 1.8%, Si 0.6%, Mn 1.4%, Cr 2.7%, Ni 0.9%, Mo 0.4%, La 51 ppm, Ce 108 ppm, Y 103 ppm, and the balance is Fe and unavoidable impurities; add ordinary scrap steel, ferrosilicon, ferromanganese, ferrochrome, ferromolybdenum, nickel plate, and carburant into the melting furnace for melting respectively, and perform secondary alloying according to the actual element content after melting; adjust the temperature in the furnace to 1570 °C, put one-third of the aluminum-cerium rare earth master alloy into the furnace, heat and hold for 20 minutes; after standing, put another one-third of the aluminum-cerium rare earth master alloy into the furnace, heat and hold for 10 minutes; after standing, adjust the temperature of the molten steel to 1460 °C, and then perform slag skimming treatment on the molten steel melt; bake the tundish at 700 °C, and then evenly spread the remaining one-third of the aluminum-cerium rare earth master alloy, all of the aluminum-yttrium master alloy and rare earth silicon-calcium modifier at the bottom of the tundish; pour the molten steel into the tundish; then set the rotational speed of the centrifugal mold to 450 revolutions per minute, and pour the semi-steel melt in the tundish into the rotating mold; perform normalizing heat treatment on the semi-steel casting. First, put the semi-steel casting into the furnace at room temperature, heat it up to 300 °C with the furnace and hold for 4 hours; then heat it up to 700 °C and hold for 5 hours; finally, heat it up to 950 °C and hold for 10 hours; after the heat preservation is completed, cool the semi-steel casting with the furnace to 480 °C, and then hold it at this temperature for tempering treatment, with the holding time of 5 hours; after the heat preservation is completed, heat the semi-steel casting with the furnace to 530 °C, and then hold it at this temperature for high-temperature tempering treatment, with the holding time of 15 hours; after the heat preservation is completed, take it out of the furnace and air-cool it to room temperature. After testing, the tensile strength of the semi-steel is 823 MPa, and the impact energy absorbed at room temperature is 25.9 J measured by an impact specimen with a size of 10 mm * 10 mm.

[0022] Example 3 The designed chemical composition ratio of the semi-steel alloy melt (mass fraction) is: C 2.0%, Si 0.5%, Mn 1.3%, Cr 2.4%, Ni 0.8%, Mo 0.5%, La 55 ppm, Ce 132 ppm, Y 50 ppm, and the balance is Fe and unavoidable impurities; ordinary scrap steel, ferrosilicon, ferromanganese, ferrochrome, ferromolybdenum, nickel plate, and carburizer are respectively added to the melting furnace for melting. After melting is complete, secondary alloying is carried out according to the actual element content; the temperature in the furnace is adjusted to 1580 °C, and one-third of the aluminum-cerium rare earth master alloy is added to the furnace, and it is kept warm and static for 20 minutes; after standing is complete, another one-third of the aluminum-cerium rare earth master alloy is added to the furnace, and it is kept warm and static for 10 minutes; after standing is complete, the molten steel temperature is adjusted to 1450 °C, and then slag skimming treatment is carried out on the molten steel melt; the tundish is baked at 700 °C, and then the remaining one-third of the aluminum-cerium rare earth master alloy, all of the aluminum-yttrium master alloy, and the rare earth silicon-calcium modifier are evenly spread on the bottom of the ladle; the molten steel is poured into the tundish; then the rotational speed of the centrifugal mold is set to 450 revolutions per minute, and the semi-steel melt in the tundish is poured into the rotating mold; normalizing heat treatment is carried out on the semi-steel casting. First, the semi-steel casting is put into the furnace at room temperature and heated up to 300 °C with the furnace and kept warm for 4 hours; then it is heated up to 700 °C and kept warm for 5 hours; finally, it is heated up to 950 °C and kept warm for 10 hours; after heat preservation is complete, the semi-steel casting is cooled with the furnace to 480 °C, and then tempering treatment is carried out with heat preservation at this temperature, and the heat preservation time is 5 hours; after heat preservation is complete, the semi-steel casting is heated up with the furnace to 530 °C, and then high-temperature tempering treatment is carried out with heat preservation at this temperature, and the heat preservation time is 15 hours; after heat preservation is complete, it is taken out of the furnace and air-cooled to room temperature. After testing, the tensile strength of the semi-steel is 801 MPa, and the impact energy absorbed at room temperature is 28.0 J measured by an impact specimen with a size of 10 mm * 10 mm.

[0023] Example 4 The designed chemical composition ratio of the semi-steel alloy melt (by mass fraction) is: C 2.0%, Si 0.5%, Mn 1.3%, Cr 2.6%, Ni 0.9%, Mo 0.4%, La 63 ppm, Ce 82 ppm, Y 96 ppm, and the balance is Fe and unavoidable impurities; ordinary scrap steel, ferrosilicon, ferromanganese, ferrochromium, ferromolybdenum, nickel plate, and carburizer are respectively added to the melting furnace for melting, and after melting is complete, secondary alloying is carried out according to the actual element content; the temperature in the furnace is adjusted to 1580 °C, and one-third of the aluminum cerium rare earth master alloy is added to the furnace, and it is kept warm and static for 20 minutes; after the static state is completed, one-third of the aluminum cerium rare earth master alloy is added to the furnace again, and it is kept warm and static for 10 minutes; after the static state is completed, the temperature of the molten steel is adjusted to 1480 °C, and then slag skimming treatment is carried out on the molten steel melt; the tundish is baked at 700 °C, and then the remaining one-third of the aluminum cerium rare earth master alloy, all of the aluminum yttrium master alloy, and the rare earth silicon calcium modifier are evenly spread on the bottom of the tundish; the molten steel is poured into the tundish; then the rotational speed of the centrifugal mold is set to 450 revolutions per minute, and the semi-steel melt in the tundish is poured into the rotating mold; normalizing heat treatment is carried out on the semi-steel casting. First, the semi-steel casting is put into the furnace at room temperature and heated up to 300 °C with the furnace and kept warm for 4 hours; then it is heated up to 700 °C and kept warm for 5 hours; finally, it is heated up to 950 °C and kept warm for 10 hours; after the heat preservation is completed, the semi-steel casting is cooled with the furnace to 480 °C, and then tempering treatment is carried out with heat preservation at this temperature, and the heat preservation time is 5 hours; after the heat preservation is completed, the semi-steel casting is heated up to 530 °C with the furnace, and then high-temperature tempering treatment is carried out with heat preservation at this temperature, and the heat preservation time is 15 hours; after the heat preservation is completed, it is taken out of the furnace and air-cooled to room temperature. After testing, the tensile strength of the semi-steel is 859 MPa, and the impact energy absorbed at room temperature is 24.2 J measured by an impact specimen with a size of 10 mm * 10 mm.

[0024] Example 5 The designed chemical composition ratio of the semi-steel alloy melt (mass fraction) is: C 1.8%, Si 0.6%, Mn 1.2%, Cr 2.6%, Ni 0.8%, Mo 0.4%, La 68 ppm, Ce 143 ppm, Y 92 ppm, and the balance is Fe and inevitable impurities; ordinary scrap steel, ferrosilicon, ferromanganese, ferrochromium, ferromolybdenum, nickel plate, and carburizer are respectively added to the melting furnace for melting, and after melting is complete, secondary alloying is carried out according to the actual element content; the temperature in the furnace is adjusted to 1560 °C, and one-third of the aluminum-cerium rare earth master alloy is added to the furnace, and it is kept warm and static for 20 minutes; after the static state is completed, one-third of the aluminum-cerium rare earth master alloy is added to the furnace again, and it is kept warm and static for 10 minutes; after the static state is completed, the temperature of the molten steel is adjusted to 1450 °C, and then slag skimming treatment is carried out on the molten steel melt; the tundish is baked at 700 °C, and then the remaining one-third of the aluminum-cerium rare earth master alloy, all of the aluminum-yttrium master alloy, and the rare earth silicon-calcium modifier are evenly spread on the bottom of the tundish; the molten steel is poured into the tundish; then the rotational speed of the centrifugal mold is set to 450 revolutions per minute, and the semi-steel melt in the tundish is poured into the rotating mold; normalizing heat treatment is carried out on the semi-steel casting. First, the semi-steel casting is put into the furnace at room temperature and heated up with the furnace to 300 °C and kept warm for 4 hours; then it is heated up to 700 °C and kept warm for 5 hours; finally, it is heated up to 950 °C and kept warm for 10 hours; after the heat preservation is completed, the semi-steel casting is cooled with the furnace to 480 °C, and then tempering treatment is carried out with heat preservation at this temperature, and the heat preservation time is 5 hours; after the heat preservation is completed, the semi-steel casting is heated up with the furnace to 530 °C, and then high-temperature tempering treatment is carried out with heat preservation at this temperature, and the heat preservation time is 15 hours; after the heat preservation is completed, it is taken out of the furnace and air-cooled to room temperature. After testing, the tensile strength of the semi-steel is 828 MPa, and the impact energy absorbed at room temperature is 23.1 J measured by an impact specimen with a size of 10 mm * 10 mm.

[0025] Comparative example Using traditional commercial semi-steel materials, the chemical composition (mass fraction) is as follows: The composition (mass fraction) of the prepared semi-steel materials is: C 1.7%, Si 0.3%, Mn 0.8%, Cr 2.2%, Ni 0.6%, Mo 0.6%, La 33 ppm, Ce 56 ppm, and the balance is Fe and unavoidable impurities; Add ordinary scrap steel, ferrosilicon, ferromanganese, ferrochromium, ferromolybdenum, nickel plate, and carburant into the melting furnace for melting. After melting is complete, perform secondary alloying according to the actual element content; Adjust the temperature in the furnace to 1620 °C, hold for 10 minutes; After standing is complete, adjust the molten steel temperature to 1500 °C, and then perform slag skimming on the molten steel melt; Bake the tundish at 700 °C, and then evenly spread rare earth silicon calcium modifier at the bottom of the tundish; Pour the molten steel into the tundish; Then set the rotational speed of the centrifugal mold to 450 revolutions per minute, and pour the semi-steel melt in the tundish into the rotating mold; Perform normalizing heat treatment on the semi-steel casting. First, put the semi-steel casting into the furnace at room temperature, heat up with the furnace to 200 °C and hold for 5 hours; Then heat up to 650 °C and hold for 5 hours; Finally, heat up to 930 °C and hold for 15 hours; After holding is complete, cool the semi-steel casting with the furnace to 450 °C, and then perform tempering treatment by holding at this temperature for 6 hours; After holding is complete, heat up the semi-steel casting with the furnace to 510 °C, and then perform high-temperature tempering treatment by holding at this temperature for 20 hours; After holding is complete, take it out of the furnace and air-cool to room temperature. After testing, the tensile strength of the semi-steel is 725 MPa, and the impact energy absorbed at room temperature is 6.8 J using an impact specimen with dimensions of 10 mm * 10 mm.

[0026] It can be seen from Examples 1-5 that the semi-steel alloy material prepared by the technical solution provided by the present invention has high strength and impact energy absorbed at room temperature, and excellent toughness.

[0027] It can be seen from the metallographic structure diagrams of Example 1 of this application and the comparative example that the ferrite in the sample of the material of this application after magnesium-based rare earth microalloying treatment is relatively round and the size of a single ferrite is also smaller. This microstructure creates conditions for the material to inhibit crack initiation and propagation.

[0028] Although the embodiments of the present invention have been disclosed as above, it is not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the illustrated examples described herein.

Claims

1. A high-toughness semi-steel for H-beam rolling roller ring, characterized in that: Its chemical composition and mass percentage are: C: 1.8%-2.0%; Si: 0.4%-0.8%; Mn: 1.1%-1.4%; Cr: 2.3%-2.8%; Ni: 0.6%-1.0%; Mo: 0.2%-0.5%; La: 50ppm-100ppm; Ce: 50ppm-200ppm; Y: 50ppm-150ppm; the balance is Fe and impurities.

2. The high-toughness semi-steel for H-beam rolling roller ring according to claim 1, characterized in that: The chemical composition mass percentage of the semi-steel is: C: 1.8%-2.0%; Si: 0.5%-0.7%; Mn: 1.2%-1.4%; Cr: 2.4%-2.7%; Ni: 0.8%-1.0%; Mo: 0.3%-0.5%; La: 50ppm-80ppm; Ce: 80ppm-150ppm; Y: 50ppm-100ppm; the balance is Fe and impurities.

3. A method for preparing a high-toughness semi-steel roller for H-beam rolling roller ring, characterized in that The steps include: Step 1, preparing a semi-steel alloy melt; calculating the content of each raw material according to the total weight of each furnace smelting and the above-mentioned composition range, preparing the raw materials for melting according to the feeding amount, and adjusting the temperature of the smelting furnace after the molten steel composition meets the required range, adding the aluminum-cerium master alloy in batches, and letting it stand; Adjust the temperature of the molten steel, and perform slag treatment on the molten steel that meets the composition requirements; evenly spread the intermediate alloy material and rare earth silicon calcium modifier on the bottom of the baked tundish; pour the molten steel after slag removal into the tundish; Step 2: draining the molten steel in the tundish into a centrifugal casting mold to obtain a semi-steel centrifugal casting with a dense structure; Step 3: Open the mold to take out the centrifugal casting, first perform normalizing heat treatment; then perform low-temperature tempering heat treatment on the casting; finally perform high-temperature tempering heat treatment on the casting; obtain a finished semi-steel material with uniform structure.

4. The method for preparing a high-toughness semi-steel roll for H-beam rolling roll ring according to claim 3, characterized in that The specific steps of step three are as follows: Step 3.1, adopting a step heat treatment system to perform normalizing heat treatment on the semi-steel casting; firstly, the semi-steel casting is put into the furnace at room temperature, and the temperature is raised to 300°C and kept for 4 hours; then the temperature is raised to 700°C and kept for 5 hours; finally, the temperature is raised to 950°C and kept for 10 hours; Step 3.2, the semi-steel casting that has completed the normalizing heat treatment is cooled to 480°C in the furnace, and then kept at this temperature for tempering treatment for 5 hours; Step 3.3, the semi-steel casting which has completed the low-temperature tempering heat treatment in the above step 3.2 is heated to 530°C in the furnace, and then kept at this temperature for high-temperature tempering treatment for 15 hours; after the insulation is completed, it is taken out of the furnace and air-cooled to room temperature.

5. The method for preparing a high-toughness semi-steel roller for H-beam rolling roller ring according to claim 3, characterized in that: In step 1, according to the total weight and chemical composition ratio of each furnace of aluminum alloy, the raw materials are calculated and prepared respectively: ordinary scrap steel, ferrosilicon, ferromanganese, ferrochrome, ferromolybdenum, nickel plate, recarburizer, aluminum cerium, aluminum yttrium and rare earth silicon calcium modifier; ordinary scrap steel, ferrosilicon, ferromanganese, ferrochrome, ferromolybdenum, nickel plate, recarburizer are added into the smelting furnace for melting respectively; after melting, the composition is tested, and secondary alloying is carried out according to the actual content of the elements, so that the composition of the molten steel meets the required range.

6. The method for preparing a high-toughness semi-steel roller for H-beam rolling roller ring according to claim 5, characterized in that: In step 1, after the secondary alloying molten steel composition meets the requirements, the furnace temperature is adjusted to 1560-1580°C, one third of the total amount of aluminum-cerium rare earth master alloy is added to the furnace, and the furnace is kept warm and allowed to stand for 20 minutes.

7. The method for preparing a high-toughness semi-steel roller for H-beam rolling roller ring according to claim 6, characterized in that: After standing for 20 minutes, add one-third of the aluminum-cerium rare earth master alloy into the furnace again, keep warm and stand for 10 minutes; after the standing is completed, adjust the temperature of the molten steel to 1450-1480°C, and then skim the molten steel.

8. The method for preparing a high-toughness semi-steel roller for H-beam rolling roller ring according to claim 7, characterized in that: The tundish is baked at 700°C, and then the remaining one-third of the aluminum-cerium rare earth master alloy, all the aluminum-yttrium master alloy and the rare earth silicon-calcium modifier are evenly spread on the bottom of the tundish, wherein the modifier composition is 31% Fe-40% Si-12% La-12% Ce-5% Ca in mass percentage.

9. The method for preparing a high-toughness semi-steel roller for H-beam rolling roller ring according to claim 3, characterized in that: In step 2, the semi-steel molten steel is centrifugally cast, and the rotation speed of the centrifugal mold is set to 450 revolutions per minute; the semi-steel molten steel in the tundish is poured into the rotating mold.

10. The high-toughness semi-steel roller for H-beam rolling roller ring according to claim 1, characterized in that: The roller adopts an impact specimen with a size of 10mm*10mm to test the room temperature impact absorption energy of 20-28J.

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