Bar wire kocks reducing ring and method of manufacture

Abstract

This invention discloses a Kocks sizing roll ring for bar and wire rod production and its manufacturing method, belonging to the technical field of manufacturing accessories for bar and wire rod rolling equipment. The roll ring consists of an outer high-carbon, high-vanadium high-speed steel working layer and an inner medium-carbon alloy steel core. The manufacturing method includes smelting the inner and outer layers of molten steel in separate furnaces and adding a stress modifier, controlling parameters to complete centrifugal casting, and then performing heat treatments such as spheroidizing annealing, high-temperature quenching, and multiple tempering before precision machining to the finished product. This invention achieves high red hardness and high wear resistance in the outer layer and high toughness in the core of the roll ring through material composition ratio and exclusive processes. The outer layer hardness is HSD90-100, and the core hardness is HSD35-45. The single-pass steel throughput reaches 40,000t, and the online time is extended by 4-6 times compared with conventional roll rings, making it suitable for harsh rolling conditions of high temperature, high pressure, and high wear.

Description

Technical Field

[0001] This invention relates to the field of manufacturing technology for parts of bar and wire rod rolling equipment, and in particular to a bar and wire rod Kocks sizing roller ring and its manufacturing method. Background Technology

[0002] Kocks reducing and sizing roller rings are key components after the finishing rolling process of bar and wire rods. They directly determine the dimensional accuracy, surface quality, and mechanical properties of the finished product. They operate under extreme conditions of high temperature (800-1000℃), high pressure, high wear, and high impact for a long time. They also need to withstand the thermal fatigue stress caused by thermal cycling. They have extremely high requirements for the rigidity, red hardness, wear resistance, and toughness of the material.

[0003] Existing roll rings are mostly made of a single material, either integrally cast or forged, such as high-chromium cast iron roll rings and forged steel roll rings. Their performance requires a compromise design: high-chromium cast iron relies on chromium carbides for wear resistance, but its hardness decreases significantly above 600℃, exhibiting poor red hardness and high brittleness, making it prone to network cracking and spalling under thermal cycling; forged steel has good toughness but insufficient hardness and poor wear resistance. These roll rings have low single-pass steel throughput and short online service life, which can no longer meet the rolling production requirements of special steels. Summary of the Invention

[0004] To address the technical problems of existing Kocks reduction sizing roll rings for bar and wire rods, such as the limited material options, the inability to balance wear resistance and toughness, and poor red hardness, this invention provides a Kocks reduction sizing roll ring for bar and wire rods and its manufacturing method. Through a centrifugal composite structure design and specific process parameters, the outer layer of the roll ring achieves high red hardness and high wear resistance, while the inner layer exhibits high toughness and high strength, making it suitable for extreme rolling conditions.

[0005] The technical solution adopted in this invention, which relates to a Kocks sizing roller ring for bar and wire rods and its manufacturing method, is as follows: A Kocks reducing and sizing roller ring for bar and wire rods comprises an outer working layer made of high-carbon, high-vanadium high-speed steel and an inner core made of medium-carbon alloy steel. The high-carbon, high-vanadium high-speed steel has the following chemical composition by mass percentage: C 2.0–3.0%, Si 0.5–1.0%, Mn 0.5–1.0%, Cr 4–8%, Ni 1–3%, Mo 4–6%, V 6–8%, W 2–4%, Nb 1–3%, P ≤0.03%, S ≤0.03%, with the remainder being Fe and unavoidable impurities. The medium-carbon alloy steel has the following chemical composition by mass percentage: C 0.3–0.6%, Si 0.2–0.4%, Mn 0.5–1.0%, Ni 0.5–1.0%, Mo 0.1–0.5%, Cr ≤0.2%, P ≤0.03%, S ≤0.03%. ≤0.03%, the remainder being Fe and unavoidable impurities.

[0006] A further improvement of the technical solution of the present invention is that the hardness of the outer working layer of the roller ring is HSD90-100, and the hardness of the inner core layer is HSD35-45.

[0007] A method for manufacturing a Kocks reduction sizing roller ring for bar and wire rods, comprising the following steps: S1. Separate furnace smelting: Separate furnace smelting is carried out according to the chemical composition requirements of the working layer and the core. After obtaining qualified molten steel, it is taken out of the furnace separately. Corresponding tempering agent is added to the molten steel and stirred. S2. Centrifugal casting: Adjust the centrifuge to the preset speed, first pour the working layer of molten steel, and after a preset time interval, pour the core of molten steel to complete the forming of the roll ring blank. S3. Heat treatment: After the roll ring blank is demolded, it is subjected to spheroidizing annealing, rough machining, high-temperature quenching and multiple tempering treatments in sequence. S4. Finishing: The heat-treated roll ring blank is precision machined to the finished size.

[0008] A further improvement of the technical solution of the present invention is that: in step S1, the working layer and the core molten steel are smelted in different medium-frequency furnaces, and the power supply time is controlled according to the smelting and tapping time; the tapping temperature of the working layer molten steel is 1520-1580℃, and the tapping temperature of the core molten steel is 1500-1560℃; the modifier added to the working layer is K-RE, with an addition amount of 0.6-1.2%, and the modifier added to the core is Ba-Si, with an addition amount of 0.6-1.2%.

[0009] A further improvement of the technical solution of the present invention is that: in step S2, the centrifuge speed is controlled at 600-800 r / min, and 0.5-1.0 kg / t of glass slag is added with the flow when pouring the molten steel of the working layer; the pouring interval between the working layer and the core molten steel is 5-10 min.

[0010] A further improvement of the technical solution of the present invention is that: in step S3, the spheroidizing annealing temperature is Ac1+10-30℃, specifically 840-860℃, the holding time is 20-30h, and a furnace cooling process is adopted.

[0011] A further improvement of the technical solution of the present invention is that: in step S3, the high-temperature quenching temperature is Accm+100-160℃, specifically 1100-1200℃, and the holding temperature is 4-8h; the tempering temperature is 540-580℃, the holding temperature is 20-30h, and the tempering is performed 3-4 times.

[0012] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows: The high hardness of the outer working layer (HSD90-100) of the roller ring of this invention achieves high wear resistance, while the high hardness of the inner core (HSD35-45) ensures high toughness, solving the problem of compromising the performance of a single material. The MC-type VC carbide of the outer working layer has good high-temperature stability, and combined with the secondary hardening effect, it has excellent red hardness, maintaining high hardness even at rolling temperatures of 800-1000℃. The roller ring of this invention has strong overall resistance to thermal fatigue and impact, and is not prone to failure problems such as cracking, peeling, and splitting, reducing the frequency of roller changes and production costs in the rolling process. At the same time, the roller ring prepared by this invention has high strength, good red hardness, good wear resistance, and good accident resistance. After being put into use, it has low wear and online time is extended by 4-6 times compared with conventional high-chromium cast iron materials. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the Kocks roller ring structure. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. In the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concepts of this invention. Example 1

[0015] This embodiment provides a Kocks reduction sizing roll ring for bar and wire rods. The chemical composition of the high-carbon, high-vanadium high-speed steel in the working layer and the medium-carbon alloy steel in the core of the roll ring, expressed as a percentage by mass, is shown in the table below: C Si Mn Cr W V Ni Mo Nb working layer 2.36 0.62 0.65 5.25 2.85 6.12 1.54 5.28 1.21 Core 0.42 0.28 0.88 0.18 0.75 0.23 0.01 The remainder consists of Fe and unavoidable impurities.

[0016] This embodiment also provides a method for manufacturing a Kocks sizing roller ring for bar and wire rods, comprising the following steps: S1. Separate furnace smelting: S1.1 According to the chemical composition requirements of the inner and outer layers of the centrifugal composite high carbon high vanadium high speed steel roller ring for bar and wire rod reduction and sizing, pig iron, scrap steel, material head, alloy, etc. are added to two medium frequency furnaces in sequence. The outer layer of molten steel is energized first. After melting and clearing, the core molten iron is energized to obtain qualified molten steel in the inner and outer layers. S1.2. The outer layer of molten steel is tapped out of the furnace at 1560℃ and quickly, with 1.0% / t of K-RE composite modifier added to the ladle and stirred. The inner layer of molten iron is tapped out of the furnace at 1540℃ and quickly, with 0.8% of inoculant Ba-Si added along with the flow and stirred.

[0017] S2, Centrifugal casting: S2.1 The centrifuge speed is controlled at 660 r / min. The outer layer is poured first. When pouring the outer layer, 1.0 kg / t of glass slag is added with the flow. S2.2 After the outer layer is poured, start timing. When the time reaches 8 minutes, start pouring the core steel.

[0018] S3, Heat Treatment: S3.1 After the roller ring rotates in the centrifuge for 90 minutes, stop the machine, open the box and demold the roller ring. Then put the roller ring into the heat treatment furnace for spheroidizing annealing. The annealing temperature is controlled at 860℃ and the holding time is 20 hours. Then the power is turned off and the furnace is cooled. S3.2 After the roll circular annealing is completed, the product is taken out of the furnace for rough machining; S3.3 After rough machining of the roller ring, it is placed in a high-temperature furnace, the temperature is controlled at 1180℃, and it is held for 4 hours. After quenching, it is placed in a low-temperature furnace, the temperature is controlled at 560℃, and it is tempered three times.

[0019] S4. Precision machining: After the centrifugal composite high-carbon high-vanadium high-speed steel roller ring is tempered, it is taken out of the furnace to the processing workshop and precision machined to the finished product size.

[0020] The centrifugal composite high-carbon high-vanadium high-speed steel roller ring prepared in this embodiment has high strength, good red hardness, good wear resistance, and low wear after use. The single rolling capacity is increased from 8,000t to 40,000t. Example 2

[0021] This embodiment provides a Kocks reduction sizing roll ring for bar and wire rods. The chemical composition of the high-carbon, high-vanadium high-speed steel in the working layer and the medium-carbon alloy steel in the core of the roll ring, expressed as a percentage by mass, is shown in the table below: C Si Mn Cr W V Ni Mo Nb working layer 2.30 0.72 0.65 4.25 2.25 6.82 1.04 5.58 1.18 Core 0.38 0.40 0.68 0.16 0.80 0.20 The remainder consists of Fe and unavoidable impurities.

[0022] This embodiment also provides a method for manufacturing a Kocks sizing roller ring for bar and wire rods, comprising the following steps: S1. Separate furnace smelting: S1.1 According to the chemical composition requirements of the inner and outer layers of the centrifugal composite high carbon high vanadium high speed steel roll ring for bar and wire rod rolling, pig iron, scrap steel, material head, alloy, etc. are added to two medium frequency furnaces in sequence. The outer layer of molten steel is energized first. After melting and clearing, the core molten iron is energized to obtain qualified molten steel in the inner and outer layers. S1.2. The outer layer of molten steel is tapped out of the furnace at 1558℃ and then quickly tapped out. 1.0% / t of K-RE composite modifier is added to the ladle and stirred. The inner layer of molten iron is tapped out of the furnace at 1542℃ and then quickly tapped out. 0.8% of inoculant Ca-Si is added with the flow and stirred.

[0023] S2, Centrifugal casting: S2.1 The centrifuge speed is controlled at 680 r / min. The outer layer is poured first. When pouring the outer layer, 1.0 kg / t of glass slag is added with the flow. S2.2 After the outer layer is poured, start timing. When the time reaches 8 minutes, start pouring the core steel.

[0024] S3, Heat Treatment: S3.1 After the roller ring rotates in the centrifuge for 160 minutes, stop the machine, open the box and demold the roller ring. Put the roller ring into the heat treatment furnace for spheroidizing annealing. The annealing temperature is controlled at 850℃ and the holding time is 18 hours. Then the power is turned off and the furnace is cooled. S3.2 After the roll circular annealing is completed, the product is taken out of the furnace for rough machining; S3.3 After rough machining of the roller ring, it is placed in a high-temperature furnace, the temperature is controlled at 1175℃, and it is held for 4 hours. After being taken out of the furnace, it is quenched. After quenching, it is placed in a low-temperature furnace, the temperature is controlled at 560℃, and it is tempered three times.

[0025] S4. Precision machining: After the centrifugal composite high-carbon high-vanadium high-speed steel roller ring is tempered, it is taken out of the furnace to the processing workshop and precision machined to the finished product size.

[0026] Comparison of performance indicators between roller rings manufactured in Examples 1 and 2 and roller rings manufactured from conventional materials: Hardness / HSD Single steel throughput / t Standard high-chromium cast iron material 70-80 8000 Forged steel 50-60 5000 Example 1 95 40000 Example 2 98 40000 In the above embodiments, a Kocks sizing roller ring for bar and wire rods and a manufacturing method are provided. The centrifugal composite high-carbon high-vanadium high-speed steel roller ring prepared by the present invention has high strength, good red hardness, good wear resistance, and forms an oxide film in the early stage of rolling, which acts as an "anti-impact pad". At the same time, it realizes the transformation of sliding friction into rolling friction in the rolling process, resulting in less wear after use on the machine, and the single rolling capacity is increased from 8000t to 40000t.

[0027] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the concept and scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the inventive concept should fall within the protection scope of the present invention. All technical contents for which protection is sought in this invention are fully described in the claims.

Claims

1. A Kocks reducing mill ring for rod wire, characterized in that: The system comprises an outer working layer made of high-carbon, high-vanadium high-speed steel and an inner core made of medium-carbon alloy steel. The chemical composition of the high-carbon, high-vanadium high-speed steel, by mass percentage, is: C 2.0–3.0%, Si 0.5–1.0%, Mn 0.5–1.0%, Cr 4–8%, Ni 1–3%, Mo 4–6%, V 6–8%, W 2–4%, Nb 1–3%, P ≤0.03%, S ≤0.03%, with the remainder being Fe and unavoidable impurities. The chemical composition of the medium-carbon alloy steel, by mass percentage, is: C 0.3–0.6%, Si 0.2–0.4%, Mn 0.5–1.0%, Ni 0.5–1.0%, Mo 0.1–0.5%, Cr ≤0.2%, P ≤0.03%, S ≤0.03%. ≤0.03%, the remainder being Fe and unavoidable impurities.

2. A Kocks reducing mill ring for rod wire, according to claim 1, characterized in that: The hardness of the outer working layer of the roller ring is HSD90-100, and the hardness of the inner core layer is HSD35-45.

3. A manufacturing method of a bar wire Kocks reducing mill ring, characterized by, The method for manufacturing the roller ring according to any one of claims 1-2 comprises the following steps: S1. Separate furnace smelting: Separate furnace smelting is carried out according to the chemical composition requirements of the working layer and the core. After obtaining qualified molten steel, it is taken out of the furnace separately. Corresponding tempering agent is added to the molten steel and stirred. S2. Centrifugal casting: Adjust the centrifuge to the preset speed, first pour the working layer of molten steel, and after a preset time interval, pour the core of molten steel to complete the forming of the roll ring blank. S3. Heat treatment: After the roll ring blank is demolded, it is subjected to spheroidizing annealing, rough machining, high-temperature quenching and multiple tempering treatments in sequence. S4. Finishing: The heat-treated roll ring blank is precision machined to the finished size.

4. A method of manufacturing a Kocks reducing mill roll ring according to claim 3, characterized in that: In step S1, the working layer and the core molten steel are smelted in different medium-frequency furnaces, and the power supply time is controlled according to the smelting and tapping time. The tapping temperature of the working layer molten steel is 1520-1580℃, and the tapping temperature of the core molten steel is 1500-1560℃. The modifier added to the working layer is K-RE, with an addition amount of 0.6-1.2%, and the modifier added to the core is Ba-Si, with an addition amount of 0.6-1.2%.

5. A method of manufacturing a Kocks reducing mill roll ring according to claim 3, characterized in that: In step S2, the centrifuge speed is controlled at 600-800 r / min, and 0.5-1.0 kg / t of glass slag is added with the flow when pouring the molten steel for the working layer; the interval between pouring the molten steel for the working layer and the core is 5-10 min.

6. A method of manufacturing a Kocks reducing mill roll ring according to claim 3, characterized in that: In step S3, the spheroidizing annealing temperature is Ac1+10-30℃, specifically 840-860℃, the holding time is 20-30h, and the furnace cooling process is adopted.

7. A method of manufacturing a Kocks reducing mill roll ring according to claim 3, characterized in that: In step S3, the high-temperature quenching temperature is Accm+100-160℃, specifically 1100-1200℃, and the holding temperature is 4-8h; the tempering temperature is 540-580℃, the holding temperature is 20-30h, and the tempering is performed 3-4 times.

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