A method for preparing alloy ductile iron rolls

Abstract

The application discloses a preparation method of alloy nodular cast iron roller and belongs to the technical field of high-performance roller preparation. The preparation method comprises the following steps: optimizing alloy nodular cast iron roller alloy proportion, increasing the mass percentage content of nickel on the basis of conventional products; pre-processing the alloy nodular cast iron roller blank; moving the pre-processed alloy nodular cast iron roller into a high-temperature resistance furnace, heating to 900-930 DEG C, and keeping warm for a period of time; adopting overall water cooling treatment on the alloy nodular cast iron roller after keeping warm; adopting air blowing treatment on the alloy nodular cast iron roller after water cooling; taking the alloy nodular cast iron roller out of the furnace after air blowing; adopting tempering treatment on the alloy nodular cast iron roller after air cooling; and cooling the alloy nodular cast iron roller to room temperature and discharging the furnace after tempering keeping warm. The application improves the hardness of the groove bottom and the side wall inside the alloy nodular cast iron roller pass, and improves the service performance of the product.

Description

Technical Field

[0001] This invention relates to the field of high-performance roll manufacturing technology, and in particular to a method for manufacturing alloy ductile iron rolls. Background Technology

[0002] For roughing rolls used in roughing mills, made of alloy ductile iron, the roll body is designed with grooves of varying depths and widths to meet the requirements of on-site rolling conditions. To meet usage requirements, the roll body needs to achieve a hardness of HSD45-55 to ensure high strength and wear resistance. The bottom and sidewalls of the grooves need to maintain the same hardness and wear resistance as the groove sides.

[0003] Conventional alloy ductile iron rolls have high carbon content, low strength, and high brittleness. The heat treatment process for conventional alloy ductile iron rolls is limited by the idea that cast products cannot be water-cooled for quenching. High-temperature quenching after exiting the furnace is done by blowing air through a spray quenching machine, resulting in low roll body hardness. Furthermore, the hardness of the groove bottom and sidewalls inside the roll die is lower than that of the roll body surface. This low hardness leads to the disadvantage of the roll body being not wear-resistant.

[0004] Therefore, it is necessary to develop new heat treatment technologies to improve the hardness of the inner groove bottom and sidewall of alloy ductile iron rolls and enhance product performance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing alloy ductile iron rolls, which improves the hardness of the inner groove bottom and sidewall of the alloy ductile iron roll, improves the roll body hardness, improves wear resistance, improves strength and toughness, and improves the performance of the product.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing alloy ductile iron rolls includes the following steps:

[0008] Step A: Optimize the alloy ratio of alloy ductile iron rolls, and increase the mass percentage of nickel based on conventional products;

[0009] Step B involves pre-processing the alloy ductile iron roll blank;

[0010] Step C: Move the pre-processed alloy ductile iron roll into a high-temperature resistance furnace, heat it to 900-930℃, and hold it at that temperature for a period of time; after holding, perform overall water cooling on the alloy ductile iron roll; after water cooling, perform air blowing on the alloy ductile iron roll; after air blowing, perform air cooling on the alloy ductile iron roll before removing it from the furnace; after air cooling, perform tempering on the alloy ductile iron roll; after tempering and holding, cool the alloy ductile iron roll to room temperature before unloading it from the furnace.

[0011] A further improvement to the technical solution of the present invention is that, in step A, the alloy ratio of the alloy ductile iron roll is improved by increasing the mass percentage of nickel to 1.5-2.5% based on the conventional product.

[0012] A further improvement of the technical solution of the present invention is that: in step C, the shortest holding time after the alloy ductile iron roll is heated in the high temperature resistance furnace is calculated by dividing the roll body diameter by 40, the unit of the shortest holding time is h, and the unit of the roll body diameter is mm.

[0013] A further improvement to the technical solution of the present invention is that, in step C, the water cooling time is 20-50 min; the air blowing time is 30-60 min; and the air cooling time is 60-90 min.

[0014] A further improvement of the technical solution of the present invention is that: in step C, the tempering temperature is 500-580℃ and the tempering holding time is 30-40h.

[0015] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows:

[0016] 1. Based on conventional products, this invention optimizes the alloy ratio of alloy ductile iron rolls, increasing the mass percentage of nickel from 1.0-1.6% to 1.5-2.5%, thereby improving the matrix strength and toughness and solving the problems of "high carbon content, low strength, and high brittleness" existing in conventional alloy ductile iron rolls.

[0017] 2. This invention breaks the mindset that casting products cannot be water-cooled. The high-temperature furnace exit adopts overall water-cooling quenching, which can simultaneously ensure that the bottom and sides of the roll body meet the process requirements, improve the quality and pass rate of the roll, reduce material waste, reduce scrap rate, and reduce costs. The high-temperature furnace exit adopts overall water cooling, which improves the overall cooling intensity of the product, thereby improving the product hardness, wear resistance, toughness, and performance. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be 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 effort.

[0019] Figure 1 This is a flowchart of the preparation method of alloy ductile iron rolls provided in the embodiments of the present invention. Detailed Implementation

[0020] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products or devices.

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0022] like Figure 1 As shown, a method for preparing an alloy ductile iron roll includes the following steps:

[0023] Step A: Optimize the alloy ratio of alloy ductile iron rolls, increasing the nickel mass percentage from 1.0-1.6% to 1.5-2.5% based on conventional products;

[0024] Step B: Pre-process the alloy ductile iron roll blank, and machine the roll shape to near the final shape;

[0025] Step C: Move the pre-processed alloy ductile iron roll into a high-temperature resistance furnace and heat it to 900-930℃. Hold it at this temperature for a period of time. The minimum holding time is calculated by dividing the roll diameter by 40. The unit for the minimum holding time is h, and the unit for the roll diameter is mm. After holding, perform overall water cooling treatment on the alloy ductile iron roll for 20-50 min. After water cooling, perform air blowing treatment on the alloy ductile iron roll for 30-60 min. After air blowing, perform air cooling treatment on the alloy ductile iron roll for 60-90 min. After air cooling, perform tempering treatment on the alloy ductile iron roll at a tempering temperature of 500-580℃ for 30-40 h. After holding, cool the alloy ductile iron roll to room temperature and remove it from the furnace.

[0026] Example 1

[0027] The diameter of the roll neck of the alloy ductile iron roll is 1200mm. Before heat treatment, the roll is machined to near the final shape. Then it is heated to 920℃ in a high-temperature resistance furnace, held for 30 hours, water-cooled for 30 minutes, blown with air for 60 minutes, air-cooled for 70 minutes and then loaded into the furnace. It is then tempered at 550℃ for 36 hours. After the holding period, it is cooled to room temperature in the furnace and then unloaded from the furnace.

[0028] Comparative Example 1

[0029] The diameter of the roll neck of the alloy ductile iron roll is 1200mm. Before heat treatment, the roll is machined to near the final shape. Then it is heated to 920℃ in a high-temperature resistance furnace, held for 30 hours, and then removed from the furnace. It is cooled by blowing air for 120 minutes and air-cooled for 90 minutes before being loaded into the furnace. It is then tempered at 530℃ for 36 hours. After the holding period, it is cooled to room temperature in the furnace before being unloaded.

[0030] The products of Example 1 and Comparative Example 1 were subjected to hardness testing and related tests in accordance with the national standard GB / T 13313~2008. The test results are shown in Tables 1, 2 and 3.

[0031] Table 1. Hardness and metallographic structure test results of the products from Example 1 and Comparative Example 1

[0032]

[0033] Table 2. Results of tensile mechanical properties of products from Example 1 and Comparative Example 1

[0034]

[0035] Table 3. Microhardness test results of products from Example 1 and Comparative Example 1

[0036]

[0037] With the same alloy ratio for alloy ductile iron rolls, a comparison of the heat treatment method of this application (Example 1) and the conventional heat treatment method (Comparative Example 1) shows that by enhancing the cooling intensity of the product, the tempering temperature can be increased, and the hardness of the alloy ductile iron rolls prepared by the conventional heat treatment process is improved. Higher hardness of the alloy ductile iron rolls results in better wear resistance; higher tempering temperatures lead to better strength and toughness, which is more beneficial for the use of alloy ductile iron rolls.

[0038] According to the metallographic structure test results in Table 1, after increasing the cooling intensity of the alloy ductile iron rolls, the microstructure changes from fine pearlite to tempered sorbite, which is denser and more conducive to use.

[0039] According to the performance test results in Tables 1, 2, and 3, after improving the cooling intensity of the alloy ductile iron rolls, Example 1, which is heat-treated by a special process, has high tensile strength, high impact energy, and better strength-toughness combination, making it more suitable for use.

[0040] According to the performance test results in Tables 1, 2, and 3, after improving the cooling intensity of the alloy ductile iron rolls, Example 1, which is heat-treated by a special process, has a higher microhardness (HV57.3, 429.9-372.6=57.3) than conventionally heat-treated products, and better wear resistance.

[0041] Furthermore, the upper and lower limits and ranges of the process parameters (such as mass percentage content, temperature, time, etc.) of the present invention can all achieve the present invention, and examples are not listed here.

[0042] In summary, this invention optimizes the alloy composition of alloy ductile iron rolls, increasing the nickel content from 1.0-1.6% to 1.5-2.5%, thereby improving the matrix strength and toughness and solving the problems of "high carbon content, low strength, and high brittleness" inherent in conventional alloy ductile iron rolls. It also breaks the limitation of traditional casting products being unable to be water-cooled, optimizing the high-temperature normalizing and quenching process of alloy ductile iron rolls from air-blast cooling to overall water cooling, improving the overall cooling intensity of the product, thus increasing hardness, wear resistance, and overall strength and toughness, ultimately enhancing the product's performance. Practical verification shows that the hardness of over 30 alloy ductile iron rolls subjected to experimental heat treatment all met the user's requirement of HSD50-55, achieving a 100% pass rate.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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 of producing an alloyed nodular iron roll, characterized by: The method comprises the following steps: Step A, optimizing the alloy proportion of the alloyed nodular iron roller, increasing the mass percentage of nickel to 1.5-2.5% on the basis of conventional products; Step B, pre-processing the alloyed nodular iron roller blank; Step C, moving the pre-processed alloyed nodular iron roller into a high-temperature resistance furnace, heating to 900-930 ℃, and keeping for a period of time, the shortest keeping time being calculated according to the roller body diameter divided by 40; after the keeping, carrying out overall water cooling treatment on the alloyed nodular iron roller; after the water cooling, carrying out air blowing treatment on the alloyed nodular iron roller; after the air blowing, taking the alloyed nodular iron roller out of the furnace after air cooling; after the air cooling, carrying out tempering treatment on the alloyed nodular iron roller; After the tempering keeping, cooling the alloyed nodular iron roller to room temperature and taking it out of the furnace; The shortest keeping time of the alloyed nodular iron roller after heating in the high-temperature resistance furnace is h, and the roller body diameter is mm; The water cooling time is 20-50 min; the air blowing time is 30-60 min; and the air cooling time is 60-90 min; The tempering temperature is 500-580 ℃, and the tempering keeping time is 30-40 h.

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