Preparation method of centrifugal composite roller with super-thick working layer

Abstract

The invention discloses a preparation method of a centrifugal composite roller with an ultra-thick working layer, which belongs to the technical field of roller preparation and comprises the following steps: step A, taking waste steel, ferronickel, ferrovanadium, ferrochromium, ferromolybdenum, ferrotungsten and electrode powder as raw materials, and smelting outer-layer molten iron and core molten iron by adopting a power frequency or intermediate frequency furnace; b, after the smelting components reach the standard, the outer-layer molten iron and the core molten iron are heated, discharged out of the furnace and poured, and step inoculation is adopted during outer-layer pouring; c, after pouring is completed, a box is opened in a cold mode, and rough machining is conducted after the box is opened in the cold Step D, performing heat treatment on the product after the rough machining is finished; and E, after heat treatment is finished, finish machining is conducted till a finished product is obtained. According to the method, the problem of difference of the structure consistency in the working layer is solved, the stable working layer structure is obtained on the basis of the super-thick working layer, the structure uniformity of the whole working layer is achieved, and the stability of the working layer is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of roll preparation, in particular to a method for preparing an ultra-thick working layer centrifugal composite roll, which is suitable for a working roll at the rear section of a hot-rolled plate and strip rolling line. Background Art

[0002] As the economic situation of steel enterprises declines, some users have gradually increased the utilization rate of rolling mill rolls, mainly by increasing the diameter of new rolls and delaying scrapping. The thickening of working rolls, especially high-nickel-chromium working rolls containing graphite, leads to significant changes in the temperature field during the casting of the working layer. The precipitation of graphite and carbides is affected by quenching, resulting in obvious differences in the microstructure of the surface and inner working layers.

[0003] Therefore, how to maintain the consistency of the working layer organization in the design of thick working rolls and thus ensure the stability of the working layer is the primary problem that rolling mill manufacturers need to solve. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a centrifugal composite roller with an ultra-thick working layer, thereby solving the problem of differences in tissue consistency within the working layer.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for preparing a super-thick working layer centrifugal composite roller comprises the following steps:

[0007] Step A, using scrap steel, ferronickel, ferrovanadium, ferrochrome, ferromolybdenum, ferrotungsten, and electrode powder as raw materials, and using an industrial frequency or medium frequency furnace to smelt outer molten iron and core molten iron;

[0008] The chemical composition of the outer layer molten iron is: C: 3.0-3.8%, Si: 0.7-1.2%, Mn: 0.4-1.2%, P≤0.10%, S≤0.05%, Cr: 1.3-3.0%, Ni: 3.0-4.5%, Mo: 0.2-1.50%, W+V+Nb≤1.0%, and the balance is Fe; the chemical composition of the core molten iron is: C: 2.5-3.5%, Si: 1.5-3.0%, Mn: 0.1-1.0%, P≤0.10%, S≤0.1%, Cr≤1.0%, Ni≤2.0%, Mo: 0.1-2.0%, W+V+Nb≤0.8%, Mg≥0.04%, and the balance is Fe;

[0009] Step B, after the smelting composition reaches the standard, the outer layer molten iron and the core molten iron are heated separately, taken out of the furnace and poured, and the outer layer is poured by step inoculation;

[0010] Step C, cold opening the box after pouring, and performing rough processing after cold opening;

[0011] Step D: heat-treating the product after rough processing;

[0012] Step E: After the heat treatment, fine processing is performed until the finished product is obtained, and the working layer of the finished roller is ≥ 70 mm.

[0013] A further improvement of the technical solution of the present invention is that in step A, the outer layer molten iron smelting temperature is 1450-1500°C, and the core molten iron smelting temperature is 1350-1550°C.

[0014] A further improvement of the technical solution of the present invention is that in step B, in order to ensure the core performance, the core molten iron inoculant amount is designed according to any two of ferrosilicon, calcium silicon and barium iron inoculants in a ratio of 1:1, and the total amount added is 5-7%.

[0015] The technical solution of the present invention is further improved in that: in step B, the outer layer of molten iron is cooled to 1400-1440°C after smelting, and 3-6% of inoculant is added by immersion when it is taken out of the furnace. The inoculant is poured with the flow when the outer layer is poured, and the flow is completed within 1-3 minutes. When 1-2% of the outer layer of molten iron is poured, the flow inoculation begins, and the inoculation rate is controlled at 1-2kg / s when the inoculation begins. The inoculation ends when the remaining 1-2% of the outer layer of molten iron is poured, and the inoculation rate is 0.5-1kg / s at the end, and the rate is gradually slowed down during the process; the core molten iron is heated to a temperature of 1430-1465°C by electricity and taken out of the furnace. The core molten iron is poured by adding 5-7% of spheroidizing inoculant in a ladle, and poured when the temperature drops to 1350-1365°C.

[0016] A further improvement of the technical solution of the present invention is that in step B, the core pouring is started 35-55 minutes after the outer layer pouring is completed.

[0017] The further improvement of the technical solution of the present invention is that in step B, the outer layer inoculant is any one or any combination of ferrosilicon, calcium silicon, silicon-zirconium alloy, and ferromanganese alloy; the core spheroidizer is any one or a mixture of rare earth magnesium and cerium-rich rare earth.

[0018] The technical solution of the present invention is further improved in that: in step C, the box is opened cold 70-85 hours after the pouring is completed, and rough processing is performed after the cold opening, with a rough addition of 5-15mm in the diameter direction of the roller body and 5-200mm in the axial direction.

[0019] A further improvement of the technical solution of the present invention is that in step D, the heat treatment method is quenching heat treatment, the quenching heating temperature is 950-1200°C, and the heating time is 1-4h; air cooling is adopted for cooling, and when the roller body temperature reaches 400-450°C, the furnace is tempered, the tempering temperature is 500-555°C, and the tempering time is 20-40h.

[0020] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is:

[0021] 1. The present invention studies the high nickel-chromium material composition, manufacturing method, spheroidization, inoculation process, pouring process and other casting process parameters and heat treatment process of the ultra-thick working layer centrifugal composite roller, and specially designs the material components. On the basis of the ultra-thick working layer, a stable working layer structure is obtained, and the entire working layer structure is uniform.

[0022] 2. The outer layer material of the roller in the present invention is mainly for obtaining good uniformity of the structure of the ultra-thick working layer. By adopting a step inoculation method, the surface layer is quenched and the precipitation of graphite is limited. The graphite content is obtained by adding a higher content of inoculant. The deeper it is, the slower the solidification rate is and the more sufficient the graphite precipitation is. The graphite content is controlled by adding a low content of inoculant, so that the uniformity of the structure of the working layer can be ensured.

[0023] 3. The present invention adopts quenching heat treatment, so that under the design of thick working layer, the residual austenite is transformed more fully through austenitization and air cooling of the working layer, so that the working layer obtains a better stable structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative labor.

[0025] Figure 1 The present invention provides a method for preparing a centrifugal composite roller with an ultra-thick working layer. The surface layer of the centrifugal composite roller with an ultra-thick working layer prepared by the method is a structural picture before 5mm deep corrosion. The black phase is graphite.

[0026] Figure 2 The present invention provides a method for preparing a centrifugal composite roller with an ultra-thick working layer. The invention discloses a structural picture of the inner layer of a centrifugal composite roller with an ultra-thick working layer before corrosion to a depth of 60 mm, wherein the black phase is graphite. DETAILED DESCRIPTION

[0027] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or apparatus.

[0028] The present invention is further described in detail below with reference to the accompanying drawings and embodiments:

[0029] A method for preparing a super-thick working layer centrifugal composite roller comprises the following steps:

[0030] Step A, using scrap steel, ferronickel, ferrovanadium, ferrochrome, ferromolybdenum, ferrotungsten, and electrode powder as raw materials, and using an industrial frequency or medium frequency furnace to smelt the outer layer molten iron and the core molten iron;

[0031] The chemical composition of the outer layer of molten iron is: C: 3.0-3.8%, Si: 0.7-1.2%, Mn: 0.4-1.2%, P≤0.10%, S≤0.05%, Cr: 1.3-3.0%, Ni: 3.0-4.5%, Mo: 0.2-1.50%, W+V+Nb≤1.0%, and the balance is Fe;

[0032] The chemical composition of the core molten iron is: C: 2.5-3.5%, Si: 1.5-3.0%, Mn: 0.1-1.0%, P≤0.10%, S≤0.1%, Cr≤1.0%, Ni≤2.0%, Mo: 0.1-2.0%, W+V+Nb≤0.8%, Mg≥0.04%, and the balance is Fe.

[0033] Step B, after the smelting composition reaches the standard, the outer layer molten iron smelting temperature is 1450-1500 ℃, and the core molten iron smelting temperature is 1350-1450 ℃. After the outer layer molten iron smelting is completed, the temperature is lowered to 1400-1440 ℃. When it is discharged from the furnace, 3-6% of the inoculant needs to be added by immersion. The inoculant is poured with the outer layer during pouring, and the flow is completed within 1-3min. When the outer layer molten iron is poured 1-2%, the flow inoculation begins. When the inoculation begins, the inoculation rate is controlled at 1-2kg / s. When the remaining 1-2% of the molten iron is poured, the inoculation is completed at 0.5-1kg / s. The rate is gradually slowed down during the process. The core molten iron is heated to a temperature of 1430-1465 ℃ by electricity and discharged from the furnace. The core molten iron is poured by adding 5-7% spheroidizing inoculant in a bag and poured when the temperature drops to 1350-1365 ℃.

[0034] Considering that the outer layer has more molten iron and the core has less molten iron, in order to ensure the performance of the core, the core molten iron flow inoculation amount is designed according to two of the inoculants such as ferrosilicon, calcium silicon, and barium iron in a 1:1 ratio, and the total amount is 5-7%. The core pouring begins 35-55 minutes after the outer layer pouring is completed.

[0035] Step C, cold unpacking after pouring for 70-85 hours, and rough machining after cold unpacking. The rough machining roller body diameter direction allowance is 5-15mm, and the axial allowance is 5-200mm. The axial allowance can be lengthened according to the size of the furnace body.

[0036] Step D, the heat treatment method is quenching heat treatment, the quenching heating temperature is 950-1200℃, the heating time is 1-4h, and the cooling is air cooling. When the roller body temperature reaches 400-450℃, the furnace is tempered, the tempering temperature is 500-555℃, and the tempering time is 20-40h.

[0037] Step E: After tempering, fine processing and testing are performed until the finished product is obtained, and the working layer of the finished roller is ≥ 70 mm (radial direction).

[0038] Example 1

[0039] A method for preparing a super-thick working layer centrifugal composite roller comprises: using scrap steel, nickel iron, vanadium iron, chromium iron, molybdenum iron, tungsten iron and electrode powder as raw materials, adopting a medium frequency furnace for smelting, and reaching a designed composition range: outer layer molten iron C: 3.8%, Si: 1.05%, Mn: 0.85%, P: 0.06%, S: 0.03%, Cr: 2.68%, Ni: 4.0%, Mo: 0.2%, W+V+Nb=0.15%, and the balance is Fe; core molten iron C: 3.36%, Si: 2.23%, Mn: 1.0%, P: 0.09%, S: 0.085%, Cr: 0.32%, Ni: 0.56%, Mo: 0.1%, W+V+Nb=0.8%, residual Mg: 0.045%, and the balance is Fe.

[0040] The outer layer of molten iron was melted at 1500℃, and after the composition met the standards, it was cooled to 1440℃ and then taken out of the furnace. The amount of molten iron poured for the outer layer was 4.98t. Incubation began after pouring 550kg, and incubation was stopped when 550kg was left. The initial incubation rate was 1.5kg / s, and the incubation rate at the end of incubation was 0.5kg / s. The incubation time was 2.3min.

[0041] The core molten iron is heated to 1450°C by electricity and then taken out of the furnace. 5.0% spheroidizing inoculant is added to the core molten iron in a ladle, and the temperature is reduced to 1350°C and poured 35 minutes after the outer layer is poured.

[0042] Unpack and rough process 75 hours after pouring. After rough processing, quench and hold at 980℃ for 2.1h. Air cool to roller surface temperature of 435℃, then temper at 530℃ for 31h.

[0043] The working layer of the finished roller is 75mm (radial direction).

[0044] Example 2

[0045] A method for preparing a super-thick working layer centrifugal composite roller comprises: using scrap steel, nickel iron, vanadium iron, chromium iron, molybdenum iron, tungsten iron and electrode powder as raw materials, adopting a medium frequency furnace for smelting, and reaching a designed composition range: outer layer molten iron C: 3.0%, Si: 0.70%, Mn: 1.20%, P: 0.05%, S: 0.03%, Cr: 3.0%, Ni: 3.91%, Mo: 0.42%, W+V+Nb=1.0%, and the balance is Fe; core molten iron C: 3.50%, Si: 2.26%, Mn: 0.83%, P: 0.08%, S: 0.08%, Cr: 1.0%, Ni: 2.0%, Mo: 0.22%, W+V+Nb=0.52%, residual Mg: 0.04%, and the balance is Fe.

[0046] The outer layer of molten iron was melted at 1490℃, and after the composition met the standards, it was cooled to 1433℃ and then taken out of the furnace. The amount of molten iron poured for the outer layer was 5.2t. Incubation began after 780kg was poured, and incubation was stopped when 780kg was left. The initial incubation rate was 1.6kg / s, and the incubation rate at the end of incubation was 0.55kg / s. The incubation time was 2.7min.

[0047] The core molten iron is heated to 1455°C by electricity and then taken out of the furnace. 6.0% spheroidizing inoculant is added to the core molten iron in a ladle, and the temperature is reduced to 1356°C and poured 40 minutes after the outer layer is poured.

[0048] Unpack and rough process 78h after pouring. After rough processing, quench and hold at 1200℃ for 3.0h. After holding, air cool to roller surface temperature of 450℃, then temper at 530℃ for 40h.

[0049] The working layer of the finished roller is 82mm (radial direction).

[0050] Example 3

[0051] A method for preparing a super-thick working layer centrifugal composite roller comprises: using scrap steel, nickel iron, vanadium iron, chromium iron, molybdenum iron, tungsten iron and electrode powder as raw materials, adopting a medium frequency furnace for smelting, and reaching a designed composition range: outer layer molten iron C: 3.35%, Si: 1.2%, Mn: 0.4%, P: 0.05%, S: 0.03%, Cr: 2.65%, Ni: 4.5%, Mo: 1.5%, W+V+Nb=0.17%, and the balance is Fe; core molten iron C: 2.5%, Si: 2.28%, Mn: 0.78%, P: 0.07%, S: 0.08%, Cr: 0.36%, Ni: 0.69%, Mo: 0.60%, W+V+Nb=0.42%, residual Mg: 0.046%, and the balance is Fe.

[0052] The outer layer of molten iron was melted at 1450℃, and after the composition met the standards, it was cooled to 1426℃ and then taken out of the furnace. The amount of molten iron poured for the outer layer was 5.1t. Incubation began after 700kg was poured, and incubation was stopped when 700kg was left. The initial incubation rate was 1.48kg / s, and the incubation rate at the end of incubation was 0.52kg / s. The incubation time was 3.0min.

[0053] The core molten iron is heated to 1463℃ by electricity and then taken out of the furnace. 5.2% spheroidizing inoculant is added to the core molten iron in a ladle, and the temperature is reduced to 1355℃ and the outer layer is poured 42 minutes later.

[0054] Unpack and rough process 72 hours after pouring. After rough process, quench and hold at 980℃ for 2.7 hours. Air cool to roller surface temperature of 436℃, then temper at 555℃ for 35 hours.

[0055] The working layer of the finished roller is 80mm (radial direction).

[0056] Example 4

[0057] A method for preparing a super-thick working layer centrifugal composite roller comprises: using scrap steel, nickel iron, vanadium iron, chromium iron, molybdenum iron, tungsten iron and electrode powder as raw materials, adopting a medium frequency furnace for smelting, and reaching the design composition range of ductile iron: outer layer molten iron C: 3.32%, Si: 1.08%, Mn: 0.95%, P: 0.05%, S: 0.035%, Cr: 2.57%, Ni: 3.0%, Mo: 0.39%, W+V+Nb=0.18%, and the balance is Fe; core molten iron C: 3.37%, Si: 1.5%, Mn: 0.75%, P: 0.085%, S: 0.07%, Cr: 0.33%, Ni: 0.64%, Mo: 2.0%, W+V+Nb=0.40%, residual Mg: 0.044%, and the balance is Fe.

[0058] The outer layer of molten iron was melted at 1497℃, and after the composition met the standards, it was cooled to 1412℃ and then taken out of the furnace. The amount of molten iron poured for the outer layer was 4.3t. Incubation began after 450kg was poured, and incubation was stopped when 450kg was left. The initial incubation rate was 1.3kg / s, and the incubation rate at the end of incubation was 0.50kg / s. The incubation time was 2.1min.

[0059] The core molten iron is heated to 1458°C by electricity and then taken out of the furnace. 7.0% spheroidizing inoculant is added to the core molten iron in a ladle, and the temperature is reduced to 1362°C and poured 55 minutes after the outer layer is poured.

[0060] Unpack and rough process 76 hours after pouring. After rough process, quench and hold at 950℃ for 2.5 hours. Air cool to roller surface temperature of 431℃, then temper at 525℃ for 37 hours.

[0061] The working layer of the finished roller is 70mm (radial direction).

[0062] Example 5

[0063] A preparation method of an ultra-thick working layer centrifugal composite roller comprises: using scrap steel, nickel iron, vanadium iron, chromium iron, molybdenum iron, tungsten iron and electrode powder as raw materials, adopting a medium frequency furnace for smelting, and reaching the design composition range of ductile iron: outer layer molten iron C: 3.33%, Si: 1.05%, Mn: 0.87%, P: 0.06%, S: 0.04%, Cr: 1.3%, Ni: 3.89%, Mo: 0.29%, W+V+Nb=0.15%, and the balance is Fe; core molten iron C: 3.0%, Si: 2.26%, Mn: 0.77%, P: 0.08%, S: 0.06%, Cr: 0.38%, Ni: 0.60%, Mo: 0.29%, W+V+Nb=0.43%, residual Mg: 0.048%, and the balance is Fe.

[0064] The outer layer of molten iron was melted at 1474℃, and after the composition met the standards, it was cooled to 1406℃ and then taken out of the furnace. The amount of molten iron poured for the outer layer was 5.15t. Incubation began after 530kg was poured, and incubation was stopped when 530kg was left. The initial incubation rate was 1.6kg / s, and the incubation rate at the end of incubation was 0.53kg / s. The incubation time was 2.5min.

[0065] The core molten iron is heated to 1430℃ by electricity and then taken out of the furnace. 6.4% spheroidizing inoculant is added to the core molten iron in a ladle, and the temperature is reduced to 1355℃ and poured 50 minutes after the outer layer is poured.

[0066] Unpack and rough process 85 hours after pouring. After rough processing, quench and hold at 980℃ for 4 hours. After holding, air cool to roller surface temperature of 400℃, then temper at 500℃ for 20 hours.

[0067] The working layer of the finished roller is 75mm (radial direction).

[0068] Example 6

[0069] A method for preparing a super-thick working layer centrifugal composite roller comprises: using scrap steel, nickel iron, vanadium iron, chromium iron, molybdenum iron, tungsten iron and electrode powder as raw materials, adopting a medium frequency furnace for smelting, and reaching the design composition range of ductile iron: outer layer molten iron C: 3.35%, Si: 1.01%, Mn: 0.96%, P: 0.07%, S: 0.04%, Cr: 2.35%, Ni: 3.99%, Mo: 0.31%, W+V+Nb=0.18%, and the balance is Fe; core molten iron C: 3.33%, Si: 2.28%, Mn: 0.1%, P: 0.08%, S: 0.04%, Cr: 0.35%, Ni: 0.55%, Mo: 0.21%, W+V+Nb=0.48%, residual Mg: 0.051%, and the balance is Fe.

[0070] The outer layer of molten iron was melted at 1465℃, and after the composition met the standards, it was cooled to 1400℃ and then taken out of the furnace. The amount of molten iron poured for the outer layer was 3.8t. Incubation began after 400kg was poured, and incubation was stopped when 400kg was left. The initial incubation rate was 2kg / s, and the incubation rate at the end of incubation was 1kg / s. The incubation time was 1min.

[0071] The core molten iron is heated to 1460℃ by electricity and then taken out of the furnace. 7.1% spheroidizing inoculant is added to the core molten iron in a ladle, and the temperature is reduced to 1350℃ and the outer layer is poured 30 minutes later.

[0072] Unpack and rough process 70 hours after pouring. After rough processing, quench and hold at 975℃ for 1 hour. Air cool to roller surface temperature of 437℃, then temper at 540℃ for 35 hours.

[0073] The working layer of the finished roller is 73mm (radial direction).

[0074] Comparative Example 1

[0075] A preparation method of an ultra-thick working layer centrifugal composite roller comprises: using scrap steel, nickel iron, vanadium iron, chromium iron, molybdenum iron, tungsten iron and electrode powder as raw materials, adopting a medium frequency furnace for smelting, and reaching the design composition range of ductile iron: outer layer molten iron C: 3.37%, Si: 1.03%, Mn: 0.98%, P: 0.06%, S: 0.05%, Cr: 2.46%, Ni: 4.0%, Mo: 0.35%, W+V+Nb=0.19%, and the balance is Fe; core molten iron C: 3.35%, Si: 2.24%, Mn: 0.78%, P: 0.07%, S: 0.04%, Cr: 0.36%, Ni: 0.58%, Mo: 0.26%, W+V+Nb=0.41%, residual Mg: 0.045%, and the balance is Fe.

[0076] The outer layer of molten iron was melted at 1465℃, and after the composition met the standards, it was cooled to 1435℃ and then taken out of the furnace. The amount of molten iron poured for the outer layer was 4.5t. Incubation began after 470kg was poured, and incubation was stopped when 470kg was left. The incubation rate was always 1.02kg / s, and the incubation time was 2.6min.

[0077] The core molten iron is heated to 1465℃ by electricity and then taken out of the furnace. 6.8% spheroidizing inoculant is added to the core molten iron in a ladle, and the temperature is reduced to 1365℃ and poured 55 minutes after the outer layer is poured.

[0078] Unpack and roughly charge 73 hours after pouring. After rough charging, quench and hold at 970℃ for 2.3 hours. Air cool to roller surface temperature of 435℃, then temper at 530℃ for 36 hours.

[0079] The working layer of the finished roller is 78mm (radial direction).

[0080] The finished roll working layers prepared in Examples 1-6 and Comparative Example 1 were subjected to product structure testing, and the test results are shown in Table 1 below:

[0081] Table 1 Product tissue test results

[0082] Test items Working layer graphite content range Example 1 0.93-1.31 Example 2 0.83-1.23 Example 3 0.88-1.30 Example 4 0.91-1.28 Example 5 0.84-1.30 Example 6 0.87-1.28 Comparative Example 1 0.97-2.12

[0083] As shown in Table 1, the graphite precipitation of the ultra-thick working layer centrifugal composite roller produced by the uniform inoculation method in Control Example 1 is significantly higher than that of the ultra-thick working layer centrifugal composite roller produced by the step inoculation method in Examples 1-6, and the wear resistance of the ultra-thick working layer centrifugal composite roller decreases in the later period of use. By adopting the step inoculation method, such as Figure 1 , 2 As shown, the uniformity of the structure of the entire working layer of the ultra-thick working layer centrifugal composite roller can be effectively guaranteed, thereby ensuring the good and stable performance of the roller from the time the new roller is put into use to the time it is scrapped.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a super-thick working layer centrifugal composite roller, characterized in that: The following steps are involved: Step A, using scrap steel, ferronickel, ferrovanadium, ferrochrome, ferromolybdenum, ferrotungsten, and electrode powder as raw materials, and using an industrial frequency or medium frequency furnace to smelt outer molten iron and core molten iron; The chemical composition of the outer layer molten iron is: C: 3.0-3.8%, Si: 0.7-1.2%, Mn: 0.4-1.2%, P≤0.10%, S≤0.05%, Cr: 1.3-3.0%, Ni: 3.0-4.5%, Mo: 0.2-1.50%, W+V+Nb≤1.0%, and the balance is Fe; the chemical composition of the core molten iron is: C: 2.5-3.5%, Si: 1.5-3.0%, Mn: 0.1-1.0%, P≤0.10%, S≤0.1%, Cr≤1.0%, Ni≤2.0%, Mo: 0.1-2.0%, W+V+Nb≤0.8%, Mg≥0.04%, and the balance is Fe; Step B, after the smelting composition reaches the standard, the outer layer molten iron and the core molten iron are heated separately, taken out of the furnace and poured, and the outer layer is poured by step inoculation; Step C, cold opening the box after pouring, and performing rough processing after cold opening; Step D: heat-treating the product after rough processing; Step E: After the heat treatment, fine processing is performed until the finished product is obtained, and the working layer of the finished roller is ≥ 70 mm.

2. The method for preparing a super-thick working layer centrifugal composite roller according to claim 1, characterized in that: In step A, the outer layer molten iron smelting temperature is 1450-1500°C, and the core molten iron smelting temperature is 1350-1550°C.

3. The method for preparing a super-thick working layer centrifugal composite roller according to claim 1, characterized in that: In step B, in order to ensure the core performance, the core molten iron inoculant amount is designed according to any two of ferrosilicon, calcium silicon, and barium iron inoculants in a ratio of 1:1, and the total amount added is 5-7%.

4. The method for preparing a super-thick working layer centrifugal composite roller according to claim 1, characterized in that: In step B, the outer layer of molten iron is cooled to 1400-1440°C after smelting, and 3-6% of inoculant is added by immersion before being taken out of the furnace. The inoculant is poured with the flow when the outer layer is poured, and the flow is completed within 1-3 minutes. When 1-2% of the outer layer of molten iron is poured, the flow inoculation begins, and the inoculation rate is controlled at 1-2kg / s at the beginning of inoculation. The inoculation ends when the remaining 1-2% of the outer layer of molten iron is poured, and the inoculation rate is 0.5-1kg / s at the end, and the rate is gradually slowed down during the process; the core molten iron is heated to a temperature of 1430-1465°C by electricity and taken out of the furnace. The core molten iron is added with 5-7% spheroidizing inoculant in a ladle, and poured when the temperature drops to 1350-1365°C.

5. The method for preparing a super-thick working layer centrifugal composite roller according to claim 1, characterized in that: In step B, the core pouring starts 35-55 minutes after the outer layer pouring is completed.

6. The method for preparing a super-thick working layer centrifugal composite roller according to claim 1, characterized in that: In step B, the outer layer inoculant is any one or any combination of ferrosilicon, calcium silicon, silicon-zirconium alloy, and ferromanganese alloy; the core spheroidizer is any one or a mixture of rare earth magnesium and cerium-rich rare earth.

7. The method for preparing a super-thick working layer centrifugal composite roller according to claim 1, characterized in that: In step C, the box is opened cold 70-85 hours after the pouring is completed, and rough processing is performed after the cold opening, with a rough allowance of 5-15mm in the roller body diameter direction and 5-200mm in the axial direction.

8. The method for preparing a super-thick working layer centrifugal composite roller according to claim 1, characterized in that: In step D, the heat treatment method is quenching heat treatment, the quenching heating temperature is 950-1200℃, and the heating time is 1-4h; cooling is air cooling, and when the roller body temperature reaches 400-450℃, the furnace is tempered, the tempering temperature is 500-555℃, and the tempering time is 20-40h.

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