Method for improving wear resistance of working layer of high-nickel-chromium infinite chilled centrifugal composite cast iron roll

Abstract

The invention belongs to the technical field of roller manufacturing, and particularly relates to a method for improving the wear resistance of a working layer of a high-nickel-chromium infinite chilled centrifugal composite cast iron roller. The roller working layer comprises the following chemical components in percentage by mass: 3.0 to 3.5 percent of C, 0.6 to 1.2 percent of Si, 0.6 to 1.05 percent of Mn, 2.0 to 4.5 percent of Ni, 0.7 to 2.0 percent of Cr, 0.2 to 1.0 percent of Mo, 0.1 to 1.0 percent of V, 0.2 to 1.5 percent of W, less than or equal to 0.1 percent of P, less than or equal to 0.05 percent of S and the balance of Fe. In the process of centrifugally casting and pouring the working layer molten iron, the high-hardness WC composite particles are injected into a casting mold of a centrifugal machine along with the working layer molten iron, and after the core part of the nodular cast iron roller is subjected to gravity casting, the centrifugal composite roller is subjected to heat treatment. The method can effectively solve the problem that a conventional high-nickel-chromium infinite chilled centrifugal composite cast iron roll is poor in wear resistance when being used in the rear section of finish rolling of a hot rolled strip.

Description

Technical Field

[0001] The present invention belongs to the technical field of roll manufacturing, and particularly relates to a method for improving the wear resistance of the working layer of a high-nickel-chromium infinitely chilled centrifugally compounded cast iron roll. Background Art

[0002] Steel production is one of the important indicators for measuring the development of the industry. Among all steel materials, more than half of the materials need to be formed by rolling mills. As the main component of the rolling mill, the roll is in direct contact with the rolled piece during the rolling process, and the service conditions are relatively harsh. It is the main consumable device on the rolling mill, and its consumption accounts for 10% - 15% of the rolling cost.

[0003] Centrifugally compounded rolls have the characteristics of simple process equipment, less machining, and low cost, and are the roll materials with the fastest development and the broadest application prospects. Among them, due to its good wear resistance and thermal crack resistance, the high-nickel-chromium infinitely chilled centrifugally compounded cast iron roll has been applied to the working rolls in the finishing section of almost all hot strip continuous rolling mills at home and abroad. The working layer of its roll body is made of infinitely chilled cast iron material produced by centrifugal casting process, and the roll neck and core are made of ductile iron with good strength and toughness produced by gravity casting process. Specifically, the service performance of the high-nickel-chromium infinitely chilled centrifugally compounded cast iron roll is determined by the microstructure of the working layer of the roll body. The matrix structure of the roll body is bainite + a small amount of martensite + retained austenite + cementite + graphite. Among them, fine and high-hardness carbides are dispersed in the matrix structure, which can provide wear-resistant phases for the roll and significantly improve the overall wear resistance of the roll.

[0004] Currently, the grades of rolled steel are continuously improving, the rolling process is becoming more and more automated and rapid, and the rolling line urgently needs to extend the mill rolling volume of the roll and reduce the roll changing frequency. The rolling process of special strip steel has higher and higher requirements for the rolling force, red hardness, and wear resistance of the roll. The conventional high-nickel-chromium infinitely chilled centrifugally compounded cast iron roll can no longer meet the requirements of the rolling production of special strip steel.

[0005] Therefore, some solutions are given in the prior art: Chinese Patent Application (Publication No. CN103074539A) proposes a centrifugally compounded 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 the roll body of the conventional high-nickel-chromium infinitely chilled centrifugally compounded cast iron, fine granular high-hardness carbides are obtained, which play a role in precipitation strengthening, and the wear resistance is improved while maintaining good accident resistance. However, this alloying treatment process has a high cost, and due to the large density difference between W and V carbides and molten iron, segregation of tissue components is likely to occur, which greatly affects the wear resistance of the working layer of the roll.

[0006] The Chinese patent application (Publication No. CN100402687C) proposes a multi-element high-nickel chromium alloy wear-resistant cast iron and its preparation process. By adopting a treatment process of introducing rare earth elements (Re, V, Ti) as modifiers, the structure, morphology and distribution of some carbides can be changed, and at the same time, it helps to improve the graphite morphology, obtaining a multi-element high-nickel chromium alloy wear-resistant cast iron material with high oxidation resistance and high wear resistance. However, the above process of introducing rare earth elements as modifiers has a high process cost and a low yield, and is not suitable for large-scale production.

[0007] The Chinese patent application (Publication No. CN108796352A) proposes a tungsten-modified high-chromium cast iron roll and its preparation method. By introducing the process of WC during the melting process of the working layer molten iron, the structure of the working layer is refined. During use, stress concentration can be reduced, and the overall wear resistance and thermal crack resistance of the high-chromium cast iron roll can be greatly improved. However, the density of WC is higher than that of the molten iron, and it is easy to settle at the bottom of the molten iron during the smelting process. Subsequently, serious gravity segregation will inevitably occur under the action of the centrifugal force field, resulting in the "peak effect", which increases energy consumption. Summary of the Invention

[0008] 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 a high-nickel chromium infinitely chilled centrifugal composite cast iron roll. This method does not interfere with the normal production of the centrifugal composite roll, has a low cost, strong operability, and can effectively solve the problem of poor wear resistance of conventional high-nickel chromium infinitely chilled centrifugal composite cast iron rolls during the finishing section of hot rolling strip.

[0009] In order to achieve the above purpose, the technical solution of the present invention is: A method for improving the wear resistance of the working layer of a high-nickel chromium infinitely chilled centrifugal composite cast iron roll, comprising the following steps: (1) Melting: According to the alloy composition of the working layer of high-nickel chromium cast iron, batching is carried out and added to the intermediate frequency furnace for smelting and adjusting the composition to be qualified. When the temperature of the molten iron reaches 1440 - 1480 °C, tapping is carried out, and at the same time, 0.1 - 0.2 wt% of ferrosilicon inoculant is added to the ladle with the flowing molten iron to obtain the working layer molten iron of the high-nickel chromium infinitely chilled centrifugal composite cast iron roll; Among them, the chemical components and their mass percentages of the working layer of the roll 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 balance is Fe; (2) Composite casting and forming: The working layer of the centrifugally composite cast iron roll is cast using a horizontal centrifuge. The casting mold temperature of the roll mold is 120 - 150 °C, and the rotational speed of the horizontal centrifuge is 900 - 1000 r / min. During the pouring process of the molten iron for the working layer, high-hardness WC composite particles are injected into the centrifuge mold along with the molten iron for the working layer, and the pouring temperature is 1340 - 1380 °C. (3)Heat treatment: The obtained composite roll is heated from room temperature to 380 - 450 °C at a rate of 15 - 20 °C / h, held for 7 - 10 h, and then cooled to room temperature in the furnace.

[0010] In the method for improving the wear resistance of the working layer of the high-nickel-chromium infinitely chilled centrifugally composite cast iron roll, in step (1), the mass percentage content of V in the working layer of the roll is 0.1 - 0.8%.

[0011] In the method for improving the wear resistance of the working layer of the high-nickel-chromium infinitely chilled centrifugally composite cast iron roll, in step (1), the mass percentage content of W in the working layer of the roll is 0.5 - 1.0%.

[0012] In the method for improving the wear resistance of the working layer of the high-nickel-chromium infinitely chilled centrifugally composite cast iron roll, in step (2), the high-hardness WC composite particles are prepared from WC powder and Fe powder in a weight ratio of 1:1; among them, the particle sizes of WC powder and Fe powder are 0.5 - 3 μm, and the content of WC composite particles in the working layer of the roll is 0.6 - 1.0 wt%.

[0013] The composite cast iron roll in the method for improving the wear resistance of the working layer of the high-nickel-chromium infinitely chilled centrifugally composite cast iron roll is an integral structure composed of composite centrifugal casting for the working layer and gravity casting for the nodular cast iron roll core.

[0014] In the method for improving the wear resistance of the working layer of the high-nickel-chromium infinitely chilled centrifugally composite cast iron roll, the melting process of the molten iron for the nodular cast iron roll core is as follows: The molten iron for the nodular cast iron roll core is melted in an intermediate frequency induction furnace. After adjusting the composition to be qualified, silicon grain inoculant is added to the bottom of the ladle, and when the tapping temperature reaches 1440 - 1460 °C, the molten iron is tapped into the ladle; the molten iron enters the wire feeding station for inoculation and spheroidization treatment.

[0015] In the method for improving the wear resistance of the working layer of the high-nickel-chromium infinitely chilled centrifugally composite cast iron roll, the gravity casting process of the nodular cast iron roll core is as follows: After the molten iron for the working layer is completely solidified, the roll mold is lifted out and combined with the bottom box and the riser box for gravity casting. The pouring temperature of the molten iron for the nodular cast iron roll core is 1340 - 1360 °C; after pouring is completed, the mold is opened when the mold temperature ≤ 150 °C to form a composite roll.

[0016] The design concept of the present invention is: Based on the conventional casting technology of high-nickel chromium infinitely chilled centrifugal composite cast iron rolls, through process composition adjustment, high-hardness WC composite particles are introduced into the molten iron during the centrifugal casting process. After the gravity casting mold is opened, heat treatment is carried out on the centrifugal composite rolls.

[0017] Hard particle composite strengthening: During the centrifugal casting process, WC-Fe composite particles (WC:Fe = 1:1, particle size 0.5 - 3μm, addition amount 0.6 - 1.0wt%) are injected synchronously to form a "hard phase + ductile matrix" composite structure. Most of the existing technologies rely on alloying elements (such as Cr, Mo, Nb) or layered design, and do not disclose a method for improving wear resistance through in-situ particle strengthening.

[0018] Component synergy optimization: The 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 the balance of hardness and toughness.

[0019] Composite casting process and heat treatment: The composite cast iron roll is an integral structure composed of composite centrifugal casting of the working layer and gravity casting of the ductile iron roll core. The molten iron of the working layer is poured at a centrifuge speed of 900 - 1000 r / min, and combined with the centrifugal uniform dispersion technology of WC particles. At the same time, it is heated to 380 - 450°C at a rate of 15 - 20°C / h and held for 7 - 10 h, significantly reducing the residual stress.

[0020] Therefore, the present invention first introduces WC composite particles into the centrifugal casting process of high-nickel chromium infinitely chilled cast iron rolls, combines composition optimization and heat treatment to form a multiple synergistic strengthening mechanism. High-nickel chromium infinitely chilled centrifugal composite cast iron optimizes toughness while maintaining high hardness through alloy strengthening, gradient microstructure design, and composite casting process, solving the problems of easy brittle cracking and short service life caused by sudden tissue change and single composition in ordinary chilled cast iron.

[0021] The advantages and beneficial effects of the present invention are as follows: 1. The present invention adopts the process of introducing high-hardness WC composite particles during the centrifugal casting process, so that the WC particles show a gradient distribution in the working layer of the high-nickel chromium infinitely chilled centrifugal composite cast iron roll, effectively improving the segregation phenomenon of WC particles in the working layer, and thus reducing the effect of the "peak effect".

[0022] 2. The high-hardness WC composite particles in the present invention are composed of WC powder and Fe powder mixed 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 a role of dispersion strengthening in the matrix, improving the wear resistance of the working layer of the roll, and thus enhancing the comprehensive service performance of the roll.

[0023] 3. The manufacturing process of the roll of the present invention has relatively low cost, strong practicability, and high efficiency, and can achieve mass production in multiple batches. Description of the Drawings

[0024] Figures 1-3 It is an electron probe microanalysis (EPMA) detection diagram at a position 7.5 mm away from the outer surface of the sample without adding high-hardness WC composite particles in Comparative Example 1. Among them, Figure 1 It is the morphology diagram of Comparative Example 1, Figure 2 It is the C element distribution diagram of the C-rich element region in Comparative Example 1, Figure 3 It is the W element distribution diagram of the W-rich element region in Comparative Example 1.

[0025] ‌ Figures 4-6 It is an electron probe microanalysis (EPMA) detection diagram at a position 7.5 mm away from the outer surface of the sample with added high-hardness WC composite particles in Example 1. Among them, Figure 4 It is the morphology diagram of Example 1, Figure 5 It is the C element distribution diagram of the C-rich element region in Example 1, Figure 6 It is the W element distribution diagram of the W-rich element region in Example 1. Detailed Embodiments

[0026] In order to better understand the above technical solutions, the above technical solutions will be described in detail below in conjunction with embodiments.

[0027] Example 1 (adding high-hardness WC composite particles): In this example, a method for improving the wear resistance of the working layer of a high-nickel-chromium infinitely chilled centrifugal composite cast iron roll includes the following steps: (1) Melting: Charge according to the alloy composition of the high-nickel-chromium cast iron working layer, and add pig iron, waste rolls, scrap steel, white iron filings, ferromanganese, ferrochromium, ferromolybdenum, nickel plates, and ferrovanadium into the intermediate frequency induction furnace according to the alloy composition ratio of the high-nickel-chromium cast iron working layer. When the molten iron temperature reaches 1460 °C, tap the iron, and at the same time add 0.15 wt% of ferrosilicon inoculant into the ladle with the flowing molten iron to obtain the molten iron of the working layer of the high-nickel-chromium infinitely chilled centrifugal composite cast iron roll.

[0028] The chemical components and their mass percentages of the working layer of the roll are: C 3.24%, Si 0.81%, Mn 0.75%, Ni 3.6%, Cr 1.73%, Mo 0.56%, V 0.48%, W 0.75%, P 0.03%, S 0.02%, and the balance is Fe.

[0029] The melting of the molten iron for the core of the ductile iron roll is carried out in an intermediate frequency induction furnace. After the composition is adjusted to be qualified, silicon grain inoculants are added to the bottom of the ladle. When the tapping temperature reaches 1450 °C, the molten iron is tapped into the ladle, and the molten iron enters the wire feeding station for inoculation and nodulizing treatment.

[0030] The chemical components and their mass percentages of the core of the ductile iron roll are: C 3.34%, Si 2.24%, Mn 0.65%, P 0.031%, S 0.007%, Ni 0.34%, Cr 0.23%, Mg 0.057%, and the balance is Fe.

[0031] (2) Composite casting forming: The working layer of the centrifugal composite cast iron roll is cast using a horizontal centrifuge. The casting mold temperature of the roll mold is 120 °C, and the rotational speed of the horizontal centrifuge is 920 r / min.

[0032] The working layer of the high-nickel-chromium infinitely chilled centrifugal composite cast iron roll is cast. High-hardness WC composite particles are injected into the centrifuge mold together with the molten iron of the working layer. The pouring temperature is 1360 °C. Specifically, the high-hardness WC composite particles are prepared from WC powder and Fe powder in a weight ratio of 1:1. Among them, the particle sizes of WC powder and Fe powder are 0.5 - 3 μm, and the content of WC composite particles in the working layer of the roll is 0.8 wt%.

[0033] The core of the ductile iron roll is cast. After the molten iron of the working layer is completely solidified, the roll mold is lifted out and combined with the bottom box and the riser box for gravity casting. The pouring temperature is 1350 °C. After pouring is completed, the mold is opened when the temperature of the roll mold is 130 °C to obtain the composite roll.

[0034] (3) Heat treatment: The obtained composite roll is heated from room temperature to 400 °C at a rate of 20 °C / h, held for 8 h, and then cooled to room temperature in the furnace.

[0035] Comparative Example 1 (without adding high-hardness WC composite particles): In this comparative example, the preparation method of the cast iron roll is as follows: (1) Melting: Ingredients are prepared according to the alloy composition of the high-nickel-chromium cast iron working layer. Pig iron, waste rolls, scrap steel, white iron chips, ferromanganese, ferrochromium, ferromolybdenum, nickel plates, and ferrovanadium are added to the intermediate frequency induction furnace according to the alloy composition ratio of the high-nickel-chromium cast iron working layer. When the temperature of the molten iron reaches 1460 °C, the molten iron is tapped, and at the same time, 0.15 wt% of ferrosilicon inoculant is added to the ladle with the flowing molten iron. The molten iron for the working layer of the high-nickel-chromium infinitely chilled centrifugal composite cast iron roll is obtained.

[0036] The chemical components and their mass percentages of the working layer of the roll are: C 3.24%, Si 0.81%, Mn 0.75%, Ni 3.6%, Cr 1.73%, Mo 0.56%, V 0.48%, W 0.75%, P 0.03%, S 0.02%, and the balance is Fe.

[0037] The melting of the molten iron for the core of the ductile iron roll is carried out in an intermediate frequency induction furnace. After melting the molten iron for the core of the ductile iron roll and adjusting the composition to be qualified, silicon grain inoculant is added to the bottom of the ladle. When the tapping temperature reaches 1450 °C, the molten iron is tapped into the ladle. The molten iron enters the wire feeding station for inoculation and spheroidization treatment.

[0038] The chemical components and their mass percentage contents of the core of the ductile iron roll are: C 3.34%, Si 2.24%, Mn 0.65%, P 0.031%, S 0.007%, Ni 0.34%, Cr 0.23%, Mg 0.057%, and the balance is Fe.

[0039] (2) Composite casting forming: Use a horizontal centrifuge to cast the working layer of the centrifugal composite cast iron roll. The casting mold temperature of the roll mold is 120 °C, and the rotational speed of the horizontal centrifuge is 920 r / min.

[0040] Cast the working layer of the high-nickel-chromium infinitely chilled centrifugal composite cast iron roll, and inject the molten iron of the working layer into the centrifuge mold. The pouring temperature is 1360 °C.

[0041] Cast the core of the ductile iron roll. After the molten iron of the working layer is completely solidified, lift the roll mold out and assemble it with the bottom box and the riser box for gravity casting. The pouring temperature is 1350 °C. After pouring is completed, open the box when the temperature of the roll mold is 130 °C to obtain the composite roll.

[0042] (3) Heat treatment: Heat the obtained composite roll from room temperature to 400 °C at a speed of 20 °C / h, hold for 8 h, and then cool to room temperature in the furnace.

[0043] As Figures 1-6 shown, the EPMA detection diagrams of the samples without adding high-hardness WC composite particles and with adding 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-rich element region coincides with the C-rich region in the sample with added high-hardness WC composite particles, and only a small amount of WC particles are observed to agglomerate near the matrix and carbides. It shows that the present invention can effectively improve the segregation phenomenon of WC particles in the working layer, and thus reduce the effect of the "peak effect". In addition, as Figures 1-3 shown, in the case of not adding high-hardness WC composite particles, the carbon content is relatively low, and some carbides show a honeycomb shape; as Figures 4 to 6 shown, after adding high-hardness WC composite particles, the carbon content increases significantly, and at the same time, the honeycomb-shaped carbides basically disappear. It shows that the high-hardness WC composite particles can significantly increase the carbon content of the carbides and improve the morphology of some carbides to a certain extent.

[0044] Example 2 (adding high-hardness WC composite particles): 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: (1) Melting: The ingredients are prepared according to the alloy composition of the high nickel-chromium cast iron working layer, and pig iron, scrap rolls, scrap steel, white iron chips, ferromanganese, ferrochrome, ferromolybdenum, nickel plate, and ferrovanadium are added to the medium frequency induction furnace according to the proportion of the high nickel-chromium cast iron working layer alloy composition. When the molten iron temperature reaches 1468°C, the iron is tapped, and 0.12wt% ferrosilicon inoculant is added to the molten iron ladle to obtain high nickel-chromium infinitely chilled centrifugal composite cast iron roll working layer molten iron.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] (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 980r / min.

[0049] Casting high nickel-chromium infinitely cold hard centrifugal composite cast iron roll working layer, high hardness WC composite particles are injected into the centrifuge mold along with the working layer molten iron, and the pouring temperature is 1370°C. Specifically, the high hardness WC composite particles are composed of WC powder and Fe powder in a weight ratio of 1:1. Among them, the particle size of WC powder and Fe powder is 0.5-3μm, and the content of WC composite particles in the roll working layer is 0.7wt%.

[0050] Casting ductile iron roll core, 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, and the pouring temperature is 1360℃. After the pouring is completed, the roll mold temperature is opened when it reaches 120℃ to obtain the composite roll.

[0051] (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.

[0052] Example 3 (addition of high hardness WC composite particles): 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: (1) Melting: The ingredients are prepared according to the alloy composition of the high nickel-chromium cast iron working layer, and pig iron, scrap rolls, scrap steel, white iron chips, ferromanganese, ferrochrome, ferromolybdenum, nickel plate, and ferrovanadium are added in a medium frequency induction furnace according to the proportion of the high nickel-chromium cast iron working layer alloy composition. When the molten iron temperature reaches 1450°C, the iron is tapped, and 0.18wt% of ferrosilicon inoculant is added to the molten iron ladle to obtain high nickel-chromium infinitely chilled centrifugal composite cast iron roll working layer molten iron.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] (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.

[0057] Casting high nickel-chromium infinitely cold hard centrifugal composite cast iron roll working layer, high hardness WC composite particles are injected into the centrifuge mold along with the working layer molten iron, and the pouring temperature is 1350°C. Specifically, the high hardness WC composite particles are composed of WC powder and Fe powder in a weight ratio of 1:1. Among them, the particle size of WC powder and Fe powder is 0.5-3μm, and the content of WC composite particles in the roll working layer is 0.9wt%.

[0058] Casting ductile iron roll core, 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, and the pouring temperature is 1340℃. After the pouring is completed, the roll mold temperature is 110℃ and the composite roll is obtained.

[0059] (3)Heat treatment: The obtained composite roll was heated from room temperature to 450 °C at a rate of 15 °C / h, held for 7 h, and then cooled to room temperature in the furnace.

[0060] As shown in Table 1 and Table 2, in order to further reflect the technical effects of the present invention, hardness tests (according to the GB / T 8263-2010 standard) and wear experiments (according to the GB 12444-2006 standard) were carried out on the high-nickel-chromium infinitely chilled centrifugal composite cast iron rolls obtained in Example 1 and Comparative Example 1, and the test results are presented.

[0061] Table 1 Hardness test results Item HRC / HSD Comparative Example 1 57 / 77 Example 1 59 / 80 Example 2 60 / 81 Example 3 62 / 84 Table 2 Wear test results Item Coefficient of friction Comparative Example 1 0.46 Example 1 0.42 Example 2 0.40 Example 3 0.39 The wear test results show that the surface wear marks of the sample without the addition of high-hardness WC composite particles are deep and the wear amount is large, while the surface wear marks of the sample with the addition of high-hardness WC composite particles are shallow and the wear amount is small. This indicates that the method provided by the present invention for improving the wear resistance of high-nickel-chromium infinitely chilled centrifugal composite cast iron rolls can greatly improve the wear resistance of the rolls, thereby improving the comprehensive service performance of the rolls.

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: According to the alloy composition of the high nickel-chromium cast iron working layer, the ingredients are added to the medium frequency furnace for smelting and adjustment to meet the requirements. When the molten iron temperature reaches 1440-1480°C, the iron is tapped, and at the same time, 0.1-0.2wt% of ferrosilicon inoculant is added to the 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 0.1-1.0%, W 0.2-1.5%, 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 roller working layer, the roller mold casting mold 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 casting mold along with the working layer molten iron, and the pouring temperature is 1340-1380°C; (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 in 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: In step (1), the mass percentage of V in the working layer of the roller is 0.1-0.8%.

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 1, characterized in that: In step (1), the mass percentage of W in the working layer of the roller is 0.5-1.0%.

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 1, characterized in that: 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 roller working layer is 0.6 to 1.0 wt%.

5. 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 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.

6. 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 5, 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, and after the composition is adjusted to meet the requirements, silicon particle inoculant is added to the bottom of the ladle, and when the tapping temperature reaches 1440-1460°C, the iron is tapped into the ladle; the molten iron enters the wire feeding station for inoculation and spheroidization treatment.

7. 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 5 or 6, characterized in that: The gravity casting process of the core of the ductile iron roll is as follows: when 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 temperature is opened when it is ≤150°C to form a composite roll.

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