A method for improving the wear resistance of the working layer of high nickel-chromium infinitely chilled centrifugal composite cast iron roll

Abstract

The present invention belongs to the technical field of roller manufacturing, and specifically relates to a method for improving the wear resistance of the working layer of a high-nickel-chromium infinitely chilled centrifugal composite cast iron roller. The chemical components and their mass percentages of the roller working layer are: C 3.0-3.5%, Si 0.6-1.2%, Mn 0.6-1.05%, Ni 2.0-4.5%, Cr 0.7-2.0%, Mo 0.2-1.0%, V 0.1-1.0%, W 0.2-1.5%, P ≤ 0.1%, S ≤ 0.05%, and the remainder is Fe. During the centrifugal casting process of pouring the working layer molten iron, high-hardness WC composite particles are injected into the centrifuge casting mold along with the working layer molten iron, and then the core of the ductile iron roller is gravity cast, and the centrifugal composite roller is heat treated. The present invention can effectively solve the problem of poor wear resistance of conventional high-nickel-chromium infinitely chilled centrifugal composite cast iron rollers during use in the latter stage of hot-rolled plate and strip finishing.

Description

Technical Field

[0001] The invention belongs to the technical field of roller manufacturing, and in particular relates to a method for improving the wear resistance of a working layer of a high-nickel-chromium infinitely chilled centrifugal composite cast iron roller. Background Art

[0002] Steel production is a key indicator of industry development. Over half of all steel materials require rolling mills to form steel. Rollers, as the most critical component of rolling mills, come into direct contact with the workpiece during rolling and form, subjecting them to harsh service conditions. Rollers are the primary consumable component on rolling mills, with wear and tear accounting for 10% to 15% of rolling costs.

[0003] Centrifugal composite rolls feature simple process equipment, minimal machining effort, and low cost, making them the fastest-growing and most promising roll material. High-nickel-chromium infinitely chilled centrifugal composite cast iron rolls, due to their excellent wear resistance and thermal cracking resistance, have been adopted as work rolls in the finishing section of nearly all hot strip mills, both domestically and internationally. The roll working layer is constructed of infinitely chilled cast iron produced using a centrifugal casting process, while the roll neck and core are constructed of ductile iron, a material with excellent toughness, produced using a gravity casting process. The performance of high-nickel-chromium infinitely chilled centrifugal composite cast iron rolls is determined by the microstructure of the roll working layer. The roll matrix consists of bainite, a small amount of martensite, retained austenite, cementite, and graphite. Fine, high-hardness carbides dispersed throughout the matrix provide wear resistance, significantly enhancing the roll's overall wear resistance.

[0004] As rolled steel grades continue to rise and rolling processes become increasingly automated and rapid, rolling lines urgently need to extend the millimeter rolling depth of rolls and reduce roll change frequency. The rolling process for special plate and strip materials places increasingly stringent requirements on roll rolling force, red hardness, and wear resistance. Conventional high-nickel-chromium, infinitely chilled centrifugal composite cast iron rolls are no longer able to meet the requirements of special plate and strip rolling production.

[0005] To this end, the existing technology provides some solutions:

[0006] A Chinese patent application (publication number CN103074539A) proposes a centrifugally composited high-nickel-niobium wear-resistant cast iron roll and its casting method. By adding Nb, W, and V alloying elements to the working layer of a conventional high-nickel-chromium, infinitely chilled centrifugally composite cast iron roll, fine, granular, high-hardness carbides are produced. This precipitation-strengthening process improves wear resistance while maintaining good resistance to accidents. However, this alloying process is costly, and due to the significant difference in density between the W and V carbides and the molten iron, microstructure segregation is prone to occur, significantly affecting the wear resistance of the roll working layer.

[0007] A Chinese patent application (publication number CN100402687C) proposes a multi-component high-nickel-chromium alloy wear-resistant cast iron and its preparation process. This process, which introduces rare earth elements (Re, V, and Ti) as modifiers, alters the structure, morphology, and distribution of some carbides while also improving graphite morphology. This results in a multi-component high-nickel-chromium alloy wear-resistant cast iron material with high oxidation resistance and wear resistance. However, this process, which introduces rare earth elements as modifiers, is costly and has a low yield, making it unsuitable for large-scale production.

[0008] A Chinese patent application (publication number CN108796352A) proposes a tungsten-modified high-chromium cast iron roll and its manufacturing method. By introducing WC into the working layer during the smelting process, the work layer's microstructure is refined. During use, this reduces stress concentration, significantly improving the roll's overall wear resistance and thermal cracking resistance. However, WC, which has a higher density than molten iron, tends to settle to the bottom of the molten iron during the smelting process. Subsequently, the centrifugal force inevitably causes severe gravity segregation, resulting in a "spike effect" and increased energy consumption. Summary of the Invention

[0009] In order to overcome the above technical problems, the purpose of the present invention is to provide a method for improving the wear resistance of the working layer of high-nickel-chromium infinitely cold-hardened centrifugal composite cast iron rolls. This method does not interfere with the normal production of centrifugal composite rolls, has low cost, and strong operability. It can effectively solve the problem of poor wear resistance of conventional high-nickel-chromium infinitely cold-hardened centrifugal composite cast iron rolls during use in the later stage of hot-rolled plate and strip finishing.

[0010] In order to achieve the above object, the technical solution of the present invention is:

[0011] A method for improving the wear resistance of a high-nickel-chromium infinitely chilled centrifugal composite cast iron roll working layer comprises the following steps:

[0012] (1) Melting:

[0013] The ingredients are prepared according to the alloy composition of the high nickel-chromium cast iron working layer, added to the medium frequency furnace for smelting and adjusting the composition to meet the requirements, and the iron is tapped when the molten iron temperature reaches 1440-1480°C. At the same time, 0.1-0.2wt% of ferrosilicon inoculant is added to the molten iron ladle to obtain the high nickel-chromium infinitely chilled centrifugal composite cast iron roll working layer molten iron;

[0014] The chemical composition and mass percentage of the roller working layer are as follows: C 3.0-3.5%, Si 0.6-1.2%, Mn 0.6-1.05%, Ni 2.0-4.5%, Cr 0.7-2.0%, Mo 0.2-1.0%, V 0.1-1.0%, W 0.2-1.5%, P ≤ 0.1%, S ≤ 0.05%, and the balance is Fe;

[0015] (2) Composite casting:

[0016] A horizontal centrifuge is used to cast the centrifugal composite cast iron roll working layer. The roller mold casting temperature is 120-150°C and the horizontal centrifuge speed is 900-1000r / min. During the pouring of the working layer molten iron, high-hardness WC composite particles are injected into the centrifuge mold along with the working layer molten iron. The pouring temperature is 1340-1380°C.

[0017] (3) Heat treatment:

[0018] The obtained composite roller is heated to 380-450° C. at room temperature at a rate of 15-20° C. / h, kept at this temperature for 7-10 hours, and then cooled to room temperature along with the furnace.

[0019] The method for improving the wear resistance of the working layer of a high-nickel-chromium infinitely chilled centrifugal composite cast iron roll is as follows: in step (1), the mass percentage of V in the working layer of the roll is 0.1 to 0.8%.

[0020] The method for improving the wear resistance of the working layer of a high-nickel-chromium infinitely chilled centrifugal composite cast iron roll is as follows: in step (1), the W mass percentage of the working layer of the roll is 0.5-1.0%.

[0021] The method for improving the wear resistance of the working layer of a high-nickel-chromium infinitely chilled centrifugal composite cast iron roll is as follows: in step (2), the high-hardness WC composite particles are prepared by mixing WC powder and Fe powder in a weight ratio of 1:1; wherein the particle sizes of the WC powder and the Fe powder are 0.5 to 3 μm, and the content of the WC composite particles in the working layer of the roll is 0.6 to 1.0 wt%.

[0022] The method for improving the wear resistance of the working layer of a high-nickel-chromium infinitely chilled centrifugal composite cast iron roll is an integrated structure formed by composite centrifugal casting of the working layer and gravity casting of the ductile iron roll core.

[0023] The method for improving the wear resistance of the working layer of a high-nickel-chromium infinitely chilled centrifugal composite cast iron roll comprises the following steps of smelting the molten iron of the core of the ductile iron roll: smelting the molten iron of the core of the ductile iron roll in a medium-frequency induction furnace, adjusting the composition to meet the requirements, adding a silicon particle inoculant to the bottom of the ladle, and tapping the iron into the ladle when the tapping temperature reaches 1440-1460°C; and the molten iron enters a wire feeding station for inoculation and spheroidization.

[0024] The method for improving the wear resistance of the working layer of a high-nickel-chromium infinitely chilled centrifugal composite cast iron roll is described. The gravity casting process of the core of the ductile iron roll is as follows: after the molten iron in the working layer is completely solidified, the roll mold is lifted out and combined with the bottom box and riser box for gravity casting. The pouring temperature of the molten iron in the core of the ductile iron roll is 1340-1360°C. After the pouring is completed, the mold is opened when the mold temperature is ≤150°C to form the composite roll.

[0025] The design idea of ​​the present invention is:

[0026] The invention is based on the conventional high nickel chromium infinitely cold hard centrifugal composite cast iron roll casting technology. Through process component adjustment, high hardness WC composite particles are injected into the centrifugal casting process along with high temperature molten iron. After gravity casting and unpacking, the centrifugal composite roll is heat treated.

[0027] Hard particle composite reinforcement: WC-Fe composite particles (WC:Fe = 1:1, particle size 0.5-3 μm, addition level 0.6-1.0 wt%) are simultaneously injected during the centrifugal casting process to form a "hard phase + tough matrix" composite structure. Existing technologies rely on alloying elements (such as Cr, Mo, and Nb) or layered designs, but no method for improving wear resistance through in-situ particle reinforcement has been disclosed.

[0028] Synergistic optimization of composition: Ni content (2.0-4.5%), Cr content (0.7-2.0%), and Mo (0.2-1.0%) in the working layer, but through the synergistic effect of Mo and V, the grains are refined and the distribution of WC particles is controlled to achieve a balance between hardness and toughness.

[0029] Composite casting process and heat treatment: The composite cast iron roll is an integrated structure composed of centrifugal casting of the working layer and gravity casting of the ductile iron roll core. Molten iron for the working layer is poured at a centrifuge speed of 900-1000 r / min, and WC particles are evenly dispersed by centrifugation. Simultaneously, the temperature is raised to 380-450°C at 15-20°C / h and held for 7-10 hours to significantly reduce residual stress.

[0030] Therefore, this invention introduces WC composite particles into the centrifugal casting process of high-nickel-chromium infinitely chilled cast iron rolls for the first time, combining composition optimization with heat treatment to form a multi-step synergistic strengthening mechanism. Through alloy strengthening, gradient microstructure design, and composite casting, the high-nickel-chromium infinitely chilled centrifugal composite cast iron maintains high hardness while optimizing toughness, addressing the brittle fracture and short lifespan associated with conventional chilled cast iron due to structural mutations and a single composition.

[0031] The advantages and beneficial effects of the present invention are as follows:

[0032] 1. The present invention adopts a process of introducing high-hardness WC composite particles into the centrifugal casting process, so that the WC particles are distributed in a gradient in the working layer of the high-nickel-chromium infinitely chilled centrifugal composite cast iron roll, effectively improving the segregation of WC particles in the working layer, thereby reducing the "peak effect".

[0033] 2. The high-hardness WC composite particles in the present invention are made by mixing WC powder and Fe powder in a certain proportion. At the same time, by controlling the particle size of the WC powder, the WC particles can be evenly distributed in the working layer of the high-nickel-chromium infinitely chilled centrifugal composite cast iron roll, playing the role of a dispersion-strengthened matrix, improving the wear resistance of the roll working layer, and thus enhancing the comprehensive service performance of the roll.

[0034] 3. The roller manufacturing process of the present invention has low cost, strong practicality, and high efficiency, and can achieve large-scale and multi-batch production. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1-Figure 3 This is an electron probe microanalysis (EPMA) test image of the sample without adding high hardness WC composite particles in Comparative Example 1 at a distance of 7.5 mm from the outer surface. Figure 1 This is the morphology diagram of Comparative Example 1. Figure 2 This is the C element distribution diagram of the C element-rich area in Comparative Example 1. Figure 3 This is the W element distribution diagram of the W element-rich area in comparative example 1.

[0036] ‌ Figure 4-Figure 6 This is an electron probe microanalysis (EPMA) test image of the sample with high hardness WC composite particles added in Example 1 at a distance of 7.5 mm from the outer surface. Figure 4 This is a morphology diagram of Example 1. Figure 5 This is the C element distribution diagram of the C element-rich area in Example 1. Figure 6 This is the W element distribution diagram of the W element-rich area in Example 1. DETAILED DESCRIPTION

[0037] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with embodiments.

[0038] Example 1 (adding high hardness WC composite particles):

[0039] In this embodiment, a method for improving the wear resistance of a working layer of a high nickel-chromium infinitely chilled centrifugal composite cast iron roll comprises the following steps:

[0040] (1) Melting: The ingredients are prepared according to the alloy composition of the high nickel-chromium cast iron working layer. Pig iron, scrap rolls, scrap steel, white iron chips, ferromanganese, ferrochrome, ferromolybdenum, nickel plate, and ferrovanadium are added to the medium frequency induction furnace in the proportion of the high nickel-chromium cast iron working layer alloy composition. When the molten iron temperature reaches 1460℃, the iron is tapped. At the same time, 0.15wt% ferrosilicon inoculant is added to the molten iron ladle to obtain the high nickel-chromium infinitely chilled centrifugal composite cast iron roll working layer molten iron.

[0041] The chemical composition and mass percentage of the roller working layer are: C3.24%, Si0.81%, Mn0.75%, Ni3.6%, Cr1.73%, Mo0.56%, V0.48%, W0.75%, P0.03%, S0.02%, and the balance is Fe.

[0042] The smelting of the ductile iron roll core molten iron is carried out in a medium frequency induction furnace. After the composition is adjusted to meet the requirements, silicon particle inoculant is added to the bottom of the ladle. When the tapping temperature reaches 1450℃, the iron is tapped into the ladle and the molten iron enters the wire feeding station for inoculation and spheroidization treatment.

[0043] The chemical composition and mass percentage of the ductile iron roll core are: C3.34%, Si2.24%, Mn0.65%, P0.031%, S0.007%, Ni0.34%, Cr0.23%, Mg0.057%, and the balance is Fe.

[0044] (2) Composite casting: Use a horizontal centrifuge to cast the centrifugal composite cast iron roll working layer. The roller mold casting temperature is 120°C and the horizontal centrifuge speed is 920r / min.

[0045] To cast the high-nickel-chromium, infinitely chilled centrifugally composite cast iron roll working layer, high-hardness WC composite particles are injected into a centrifuge mold along with the working layer molten iron at a pouring temperature of 1360°C. Specifically, the high-hardness WC composite particles are composed of WC powder and Fe powder in a 1:1 weight ratio. The particle size of the WC and Fe powders ranges from 0.5 to 3 μm, and the WC composite particles comprise 0.8 wt% of the roll working layer.

[0046] The core of the ductile iron roll is cast. When the working layer of molten iron is completely solidified, the roll mold is lifted out and combined with the bottom box and riser box for gravity casting at a pouring temperature of 1350°C. After pouring is completed, the roll mold is opened when the temperature reaches 130°C to obtain the composite roll.

[0047] (3) Heat treatment: The obtained composite roller was heated to 400°C at a rate of 20°C / h at room temperature, kept at this temperature for 8 h, and then cooled to room temperature in the furnace.

[0048] Comparative Example 1 (without adding high-hardness WC composite particles):

[0049] In this comparative example, the preparation method of the cast iron roll is as follows:

[0050] (1) Melting: The ingredients are prepared according to the alloy composition of the high nickel-chromium cast iron working layer. Pig iron, scrap rolls, scrap steel, white iron chips, ferromanganese, ferrochrome, ferromolybdenum, nickel plate, and ferrovanadium are added to the medium frequency induction furnace in the proportion of the high nickel-chromium cast iron working layer alloy composition. When the molten iron temperature reaches 1460℃, the iron is tapped and 0.15wt% ferrosilicon inoculant is added to the ladle. The high nickel-chromium infinitely chilled centrifugal composite cast iron roll working layer molten iron is obtained.

[0051] The chemical composition and mass percentage of the roller working layer are: C3.24%, Si0.81%, Mn0.75%, Ni3.6%, Cr1.73%, Mo0.56%, V0.48%, W0.75%, P0.03%, S0.02%, and the balance is Fe.

[0052] The molten iron for the core of the ductile iron roll is smelted in a medium-frequency induction furnace. After the composition is adjusted to meet the requirements, a silicon inoculant is added to the bottom of the ladle. When the tapping temperature reaches 1450°C, the iron is tapped into the ladle. The molten iron enters the wire feeding station for inoculation and spheroidization.

[0053] The chemical composition and mass percentage of the ductile iron roll core are: C3.34%, Si2.24%, Mn0.65%, P0.031%, S0.007%, Ni0.34%, Cr0.23%, Mg0.057%, and the balance is Fe.

[0054] (2) Composite casting: Use a horizontal centrifuge to cast the centrifugal composite cast iron roll working layer. The roller mold casting temperature is 120°C and the horizontal centrifuge speed is 920r / min.

[0055] Casting high nickel chromium infinitely chilled centrifugal composite cast iron roll working layer, the working layer molten iron is poured into the centrifuge casting mold, and the pouring temperature is 1360℃.

[0056] The core of the ductile iron roll is cast. When the working layer of molten iron is completely solidified, the roll mold is lifted out and combined with the bottom box and riser box for gravity casting at a pouring temperature of 1350°C. After pouring is completed, the roll mold is opened when the temperature reaches 130°C to obtain the composite roll.

[0057] (3) Heat treatment: The obtained composite roller was heated to 400°C at a rate of 20°C / h at room temperature, kept at this temperature for 8 h, and then cooled to room temperature in the furnace.

[0058] like Figures 1-6As shown in the figure, the EPMA test graph of the sample without high hardness WC composite particles and the sample with high hardness WC composite particles at a distance of 7.5 mm from the outer surface. It can be seen from the figure that the W element-rich area and the C element-rich area in the sample with high hardness WC composite particles overlap, and only a small amount of WC particles are observed to be agglomerated near the matrix and carbides. This shows that the present invention can effectively improve the segregation of WC particles in the working layer, thereby reducing the effect of the "spike effect". In addition, as Figure 1-Figure 3 As shown in Figure 2, without adding high-hardness WC composite particles, the carbon content is relatively low, and part of the carbides appear honeycomb-like; Figures 4 to 6 As shown in the figure, after adding high-hardness WC composite particles, the carbon content increased significantly, and the honeycomb carbides basically disappeared. This shows that high-hardness WC composite particles significantly increased the carbon content of carbides and improved the morphology of some carbides to a certain extent.

[0059] Example 2 (adding high hardness WC composite particles):

[0060] In this embodiment, a method for improving the wear resistance of a working layer of a high nickel-chromium infinitely chilled centrifugal composite cast iron roll comprises the following steps:

[0061] (1) Melting: The ingredients are prepared according to the alloy composition of the high nickel-chromium cast iron working layer. Pig iron, scrap rolls, scrap steel, white iron chips, ferromanganese, ferrochrome, ferromolybdenum, nickel plate, and ferrovanadium are added to the medium frequency induction furnace in the proportion of the high nickel-chromium cast iron working layer alloy composition. When the molten iron temperature reaches 1468℃, the iron is tapped. At the same time, 0.12wt% ferrosilicon inoculant is added to the molten iron ladle to obtain the high nickel-chromium infinitely chilled centrifugal composite cast iron roll working layer molten iron.

[0062] The chemical composition and mass percentage of the roller working layer are: C3.31%, Si0.89%, Mn0.74%, Ni3.70%, Cr1.80%, Mo0.45%, V0.16%, W0.66%, P0.043%, S0.021%, and the balance is Fe.

[0063] The smelting of the ductile iron roll core molten iron is carried out in a medium frequency induction furnace. After the composition is adjusted to meet the requirements, silicon particle inoculant is added to the bottom of the ladle. When the tapping temperature reaches 1460℃, the iron is tapped into the ladle and the molten iron enters the wire feeding station for inoculation and spheroidization treatment.

[0064] The chemical composition and mass percentage of the ductile iron roll core are: C3.35%, Si2.28%, Mn0.67%, P0.038%, S0.012%, Ni0.28%, Cr0.38%, Mg0.068%, and the balance is Fe.

[0065] (2) Composite casting: Use a horizontal centrifuge to cast the centrifugal composite cast iron roll working layer. The roller mold casting temperature is 130 °C and the horizontal centrifuge speed is 980 r / min.

[0066] To cast the high-nickel-chromium, infinitely chilled centrifugally composite cast iron roll working layer, high-hardness WC composite particles are injected into a centrifuge mold along with the working layer molten iron at a pouring temperature of 1370°C. Specifically, the high-hardness WC composite particles are composed of WC powder and Fe powder in a 1:1 weight ratio. The particle size of the WC and Fe powders ranges from 0.5 to 3 μm, and the WC composite particles comprise 0.7 wt% of the roll working layer.

[0067] The core of the ductile iron roll is cast. When the working layer of molten iron is completely solidified, the roll mold is lifted out and combined with the bottom box and riser box for gravity casting at a pouring temperature of 1360°C. After pouring is completed, the roll mold is opened when the temperature reaches 120°C to obtain the composite roll.

[0068] (3) Heat treatment: The obtained composite roller was heated to 380°C at a rate of 19°C / h at room temperature, kept at this temperature for 10 h, and then cooled to room temperature in the furnace.

[0069] Example 3 (adding high hardness WC composite particles):

[0070] In this embodiment, a method for improving the wear resistance of a working layer of a high nickel-chromium infinitely chilled centrifugal composite cast iron roll comprises the following steps:

[0071] (1) Melting: The ingredients are prepared according to the alloy composition of the high nickel-chromium cast iron working layer. Pig iron, scrap rolls, scrap steel, white iron chips, ferromanganese, ferrochrome, ferromolybdenum, nickel plate, and ferrovanadium are added to the medium frequency induction furnace in the proportion of the high nickel-chromium cast iron working layer alloy composition. When the molten iron temperature reaches 1450℃, the iron is tapped. At the same time, 0.18wt% ferrosilicon inoculant is added to the molten iron ladle to obtain the high nickel-chromium infinitely chilled centrifugal composite cast iron roll working layer molten iron.

[0072] The chemical composition and mass percentage of the roller working layer are: C3.42%, Si0.88%, Mn0.75%, Ni4.0%, Cr1.88%, Mo0.46%, V0.25%, W0.85%, P0.028%, S0.016%, and the balance is Fe.

[0073] The smelting of the ductile iron roll core molten iron is carried out in a medium frequency induction furnace. After the composition is adjusted to meet the requirements, silicon particle inoculant is added to the bottom of the ladle. When the tapping temperature reaches 1440℃, the iron is tapped into the ladle and the molten iron enters the wire feeding station for inoculation and spheroidization treatment.

[0074] The chemical composition and mass percentage of the ductile iron roll core are: C3.38%, Si2.35%, Mn0.68%, P0.041%, S0.019%, Ni0.37%, Cr0.23%, Mg0.059%, and the balance is Fe.

[0075] (2) Composite casting: Use a horizontal centrifuge to cast the centrifugal composite cast iron roll working layer. The roller mold casting temperature is 135°C and the horizontal centrifuge speed is 950r / min.

[0076] To cast the high-nickel-chromium, infinitely chilled centrifugally composite cast iron roll working layer, high-hardness WC composite particles are injected into a centrifuge mold along with the working layer molten iron at a pouring temperature of 1350°C. Specifically, the high-hardness WC composite particles are composed of WC powder and Fe powder in a 1:1 weight ratio. The particle size of the WC and Fe powders ranges from 0.5 to 3 μm, and the WC composite particles comprise 0.9 wt% of the roll working layer.

[0077] The core of the ductile iron roll is cast. When the working layer of molten iron is completely solidified, the roll mold is lifted out and combined with the bottom box and riser box for gravity casting at a pouring temperature of 1340°C. After pouring, the roll mold is opened when the temperature reaches 110°C to obtain the composite roll.

[0078] (3) Heat treatment: The obtained composite roller was heated to 450°C at a rate of 15°C / h at room temperature, kept at this temperature for 7 h, and then cooled to room temperature in the furnace.

[0079] As shown in Table 1 and Table 2, in order to further reflect the technical effects of the present invention, the present invention conducted hardness tests (according to GB / T8263-2010 standard) and wear tests (according to GB12444-2006 standard) on the high nickel-chromium infinitely chilled centrifugal composite cast iron rolls obtained in Example 1 and Comparative Example 1.

[0080] Table 1 Hardness test results

[0081] project HRC / HSD Comparative Example 1 57 / 77 Example 1 59 / 80 Example 2 60 / 81 Example 3 62 / 84

[0082] Table 2 Wear test results

[0083] project Friction coefficient Comparative Example 1 0.46 Example 1 0.42 Example 2 0.40 Example 3 0.39

[0084] Wear test results show that samples without high-hardness WC composite particles exhibited deep wear scars and greater wear, while samples with high-hardness WC composite particles exhibited shallow wear scars and less wear. This demonstrates that the method provided by the present invention for improving the wear resistance of high-nickel-chromium infinitely chilled centrifugally composite cast iron rolls can significantly enhance the wear resistance of the rolls, thereby improving their overall service performance.

Claims

1. A method for improving the wear resistance of the working layer of a high nickel-chromium infinitely chilled centrifugal composite cast iron roll, characterized in that: The steps include: (1) Melting: The ingredients are prepared according to the alloy composition of the high nickel-chromium cast iron working layer, added to the medium frequency furnace for smelting and adjusting the composition to meet the requirements, and the iron is tapped when the molten iron temperature reaches 1440-1480°C. At the same time, 0.1-0.2wt% of ferrosilicon inoculant is added to the molten iron ladle to obtain the high nickel-chromium infinitely chilled centrifugal composite cast iron roll working layer molten iron; The chemical composition and mass percentage of the roller working layer are as follows: C 3.0-3.5%, Si 0.6-1.2%, Mn 0.6-1.05%, Ni 2.0-4.5%, Cr 0.7-2.0%, Mo 0.2-1.0%, V 0.1-0.8%, W 0.5-1.0%, P ≤ 0.1%, S ≤ 0.05%, and the balance is Fe; (2) Composite casting: A horizontal centrifuge is used to cast the centrifugal composite cast iron roll working layer. The roller mold casting temperature is 120-150°C and the horizontal centrifuge speed is 900-1000r / min. During the pouring of the working layer molten iron, high-hardness WC composite particles are injected into the centrifuge mold along with the working layer molten iron. The pouring temperature is 1340-1380°C. In step (2), the high-hardness WC composite particles are prepared by mixing WC powder and Fe powder in a weight ratio of 1:1; wherein the particle size of the WC powder and the Fe powder is 0.5 to 3 μm, and the content of the WC composite particles in the roller working layer is 0.6 to 1.0 wt%; by controlling the particle size of the WC powder, the WC particles can be evenly distributed in the high-nickel-chromium infinitely chilled centrifugal composite cast iron roller working layer, playing a role of dispersion-strengthening matrix; (3) Heat treatment: The obtained composite roller is heated to 380-450° C. at room temperature at a rate of 15-20° C. / h, kept at this temperature for 7-10 hours, and then cooled to room temperature along with the furnace.

2. A method for improving the wear resistance of the working layer of a high nickel-chromium infinitely chilled centrifugal composite cast iron roll according to claim 1, characterized in that: The composite cast iron roll is an integrated structure formed by composite centrifugal casting of the working layer and gravity casting of the ductile iron roll core.

3. A method for improving the wear resistance of the working layer of a high nickel-chromium infinitely chilled centrifugal composite cast iron roll according to claim 2, characterized in that: The smelting process of the ductile iron roll core molten iron is as follows: the ductile iron roll core molten iron is smelted in a medium frequency induction furnace. After the composition is adjusted to meet the requirements, a silicon particle inoculant is added to the bottom of the ladle. When the tapping temperature reaches 1440-1460℃, the iron is tapped into the ladle; the molten iron enters the wire feeding station for inoculation and spheroidization treatment.

4. A method for improving the wear resistance of a working layer of a high nickel-chromium infinitely chilled centrifugal composite cast iron roll according to claim 2 or 3, characterized in that: The gravity casting process of the ductile iron roll core is as follows: when the working layer of molten iron is completely solidified, the roller mold is lifted out and combined with the bottom box and riser box for gravity casting. The pouring temperature of the molten iron of the ductile iron roll core is 1340-1360℃; after pouring is completed, the mold temperature is ≤150℃ and the mold is opened to form a composite roll.

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