Roller for rolling angle steel finished product rack and manufacturing method

Abstract

This invention discloses a rolling mill roll for angle steel finished product rolling and its manufacturing method, belonging to the field of angle steel hot rolling processing technology. The roll shaft and roll sleeve are of a mating structure. The roll shaft is made of 42CrMo forged steel, and the roll sleeve is a composite material formed by centrifugal casting. The outer layer is a high-speed steel wear-resistant working layer, and the inner layer is a graphite steel tough core. The roll sleeve is prepared by melting, centrifugal casting, heat treatment, and precision machining, and then hot-fitted to the roll shaft with an interference fit of 1.0-1.2‰. Each process has precise process parameter control. This invention achieves a combination of high wear resistance of the roll body and high strength and toughness of the roll neck. The roll body hardness is HSD80-90, the journal strength is ≥800Mpa, the online time is extended by 3-5 times, the single rolling capacity is increased to 1000t, and the steel sticking rate is 0, which greatly improves production efficiency and product qualification rate.

Description

Technical Field

[0001] This invention relates to the field of hot rolling processing technology for angle steel, and in particular to a rolling mill roll for rolling finished angle steel and its manufacturing method. Background Technology

[0002] Angle steel is a long strip of steel with an "L"-shaped end face. As one of the most basic and widely used structural steels, it has good bending resistance, compressive strength and connection performance due to its unique cross-sectional structure. It can effectively withstand loads in different directions and is widely used in almost all industrial fields such as building structures, transmission towers, mechanical equipment frames, containers, shelves, curtain wall keels, and railway vehicle manufacturing.

[0003] The finishing mill is the final rolling process in the hot rolling production of angle steel. The rolls used in this process directly determine the final dimensional accuracy, surface quality, and mechanical properties of the angle steel products. In existing technologies, the rolls in the finishing mill for angle steel mostly adopt a single-material, integral structure. This type of roll has several technical defects in actual rolling: First, localized wear on the rolls is severe, especially at the sharp corners of the angle steel die, where stress concentration easily occurs, and the wear rate is much faster than in other areas. Uneven wear quickly leads to dimensional deviations in the product, requiring frequent roll replacements or regrinding, severely impacting production efficiency and increasing production costs. Second, due to poor cooling at the roll apex, oxide scale from the steel easily adheres to the roll surface, forming a steel-sticking phenomenon, which in turn creates periodic defects in the batch of angle steel products, significantly reducing the first-pass yield of angle steel manufacturers. Third, integral rolls cannot simultaneously achieve both wear resistance of the roll body and toughness of the roll neck. If wear resistance of the roll body is prioritized, the roll neck is prone to breakage; if roll neck toughness is ensured, the wear resistance of the roll body is insufficient, resulting in extremely low single-pass steel throughput.

[0004] To address the aforementioned issues, there is an urgent need to develop a new method for manufacturing rolls for angle steel finished product rolling mills. This method should achieve a balance between the wear resistance of the roll body and the toughness of the roll neck, solving problems such as poor wear resistance of the roll pass, edge chipping, steel sticking, and roll neck breakage. It should also increase the online service life and single rolling volume of the rolls, reduce production costs, and improve the product qualification rate. Summary of the Invention

[0005] To address the problems of severe localized wear in traditional rolls, poor cooling at roll apex angles, and the difficulty in balancing wear resistance of the roll body and toughness of the roll neck in integral rolls, this invention provides a roll for rolling angle steel finished product stands and its manufacturing method. The roll adopts an interlocking structure, achieving a perfect combination of roll body wear resistance and roll neck toughness. Simultaneously, through precise control of process parameters, the overall mechanical properties and assembly strength of the roll are guaranteed, overcoming the shortcomings of existing technologies.

[0006] The technical solution adopted in this invention, which relates to a rolling mill roll for rolling angle steel finished products and its manufacturing method, is as follows: A rolling mill roll for rolling angle steel finished products is characterized in that: the rolling mill roll is a mating structure of a roll shaft and a roll sleeve, the roll sleeve is a composite material structure formed by centrifugal casting, the composite material structure includes an outer wear-resistant working layer and an inner tough core, and the roll shaft is made of high-toughness forged steel.

[0007] A further improvement of the technical solution of the present invention is that: the outer wear-resistant working layer of the roller sleeve composite material structure is made of a new type of high-speed steel, and the inner tough core is made of graphite steel.

[0008] A further improvement of the technical solution of the present invention is that, by mass percentage, the chemical composition of the outer wear-resistant working layer includes: C 1.5-2%, Si 0.5-1.0%, Mn 0.6-1.2%, Cr 4.0-6.0%, Ni 1.0-2.0%, Mo 3.0-6.0%, V 4.0-6.0%, Nb 0.5-1.0%, with the remainder being Fe and unavoidable impurities; The chemical composition of the inner tough core, by mass percentage, includes: C 0.8-1.5%, Si 1.2-1.8%, Mn 0.5-1.0%, Cr ≤0.3%, Ni ≤0.5%, Mo ≤0.5%, with the remainder being Fe and unavoidable impurities.

[0009] A method for manufacturing a roll for rolling angle steel finished product stands, comprising the following steps: S1, Smelting; S2, centrifugal casting; S2.1. Control the centrifuge speed at 400-600 r / min. When pouring the outer wear-resistant working layer of molten steel, add 0.5-1.0 kg / t of glass slag with the flow. S2.2 The pouring interval between the outer wear-resistant working layer and the inner tough core is controlled to be 5-10 minutes. After the interval is reached, the inner layer of molten steel is poured into the inner side of the formed outer wear-resistant working layer. S3. Heat Treatment: After rough machining, the centrifugally cast roller rings undergo high-temperature quenching and multiple tempering treatments. The quenching temperature is controlled at 1100-1200℃, and the tempering temperature is controlled at 540-580℃. S4. Precision machining: The heat-treated roller sleeve is machined to the preset finished size. The inner hole of the roller sleeve is precision ground by a grinding machine. The inner hole size after precision grinding forms an interference fit with the roller shaft assembly part. The interference is controlled at 1.0-1.2‰. The assembly parts of the roller shaft are also machined using a grinding machine, with machining precision matching the inner hole of the roller sleeve to ensure an interference fit of 1.0-1.2‰. S5, Roller shaft-roller sleeve interference fit; S5.1. Place the precision-machined roller set into a low-temperature resistance furnace for preheating at a temperature of 250-350℃ and a holding time of 10-20h. S5.2 After the roller sleeve is preheated and kept warm, it is taken out of the furnace within 8 minutes and placed on the hot charging pit. The hot charging pit is a circular reinforced concrete structure with a pit opening diameter of φ700mm and a pit depth of ≥2m. S5.3. Use a crane to lift the processed roller shaft, so that the roller shaft passes through the inner hole of the roller sleeve to complete the heat assembly; S5.4 After the hot fitting is completed, the roller sleeve is subjected to slow cooling treatment. The roller sleeve is wrapped with heat insulation material until the roller sleeve temperature is ≤50℃.

[0010] A further improvement of the above technical solution of the present invention is that step S1 includes the following steps: S1.1 According to the chemical composition requirements of the outer wear-resistant working layer and the inner tough core, pig iron, scrap steel, raw material and alloy are added to different medium frequency furnaces in a preset order for smelting to obtain qualified outer and inner molten steel. S1.2 Control the outer layer of molten steel to exit the furnace at a temperature of 1550-1600℃ and the inner layer of molten steel to exit the furnace at a temperature of 1500-1560℃.

[0011] A further improvement of the above technical solution of the present invention is that: in step S3, the quenching temperature is 1100-1160℃, the quenching holding time is 8-12h; the tempering is performed 3 times, and the holding time for each tempering is 30-50h.

[0012] A further improvement of the above technical solution of the present invention is that: the heat insulation material in step S45.4 includes aluminum silicate needled blanket, and the aluminum silicate needled blanket is removed after the roller sleeve is naturally cooled to ≤50°C.

[0013] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows: This invention designs the roll as a mating structure of roll shaft and roll sleeve. The roll shaft bears the alternating stress during the rolling process, and the roll sleeve is made of a composite material of high-speed steel on the outer layer and graphite steel on the inner layer. This achieves a combination of high wear resistance and high red hardness of the roll and high strength, toughness and fatigue resistance of the roll neck. It solves the problem of existing integral rolls that are difficult to balance wear resistance and toughness from the perspective of structure and materials, and effectively avoids accidents such as roll die breakage and roll neck fracture.

[0014] The roller sleeve of this invention is manufactured using a centrifugal casting process. Through separate furnace smelting, precise furnace temperature control, and reasonable pouring interval, the metallurgical bonding of the inner and outer layers of the roller sleeve is achieved, ensuring the overall bonding strength of the roller sleeve. At the same time, glass slag is added during pouring to improve the density and purity of the outer working layer, further enhancing the wear resistance of the roller sleeve.

[0015] This invention employs a heat treatment process involving high-temperature quenching and multiple tempering to precisely control the quenching and tempering temperatures and holding times. This ensures the high hardness and wear resistance of the high-speed steel outer layer of the roller sleeve, eliminates quenching stress, improves the toughness of the roller sleeve, and prevents cracking and chipping during use.

[0016] This invention employs an interference fit method to assemble the roll shaft and roll sleeve. By precisely controlling the interference amount, the preheating temperature and holding time of the roll sleeve, the hot fitting operation time, and the slow cooling process, the assembly strength of the roll shaft and roll sleeve is guaranteed, relative rotation between the two is avoided during the rolling process, and the hot fitting stress is eliminated, thus ensuring the overall assembly accuracy of the roll.

[0017] The rolls prepared by this invention have excellent performance, with a roll body hardness of HSD80-90 and a roll neck strength of ≥800Mpa. Compared with conventional semi-steel rolls, the online service life is extended by 3-5 times, effectively reducing the frequency of roll replacement and grinding, improving production efficiency and reducing production costs. Detailed Implementation

[0018] 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

[0019] 1. The roller can be made of 42CrMo forged steel with excellent strength and toughness.

[0020] 2. The roller sleeve is made of composite material and produced by centrifugal casting process. The outer layer is made of a new type of high-speed steel with high wear resistance and high hardness, which ensures a sufficient working layer thickness with high wear resistance. The inner layer is made of graphite steel, which has a certain toughness and plasticity to resist the stress caused by heat charging.

[0021] The following table shows the composition and weight percentage of the working layer and core of a roll sleeve for rolling angle steel finished product stands: wt% C Si Mn Cr Ni Mo V Nb working layer 1.7 0.80 0.86 5.05 1.44 4.50 6.0 0.8 Core 1.30 1.80 0.80 0.20 0.50 0.30 A method for manufacturing rolls for rolling angle steel finished products includes the following steps: S1, Smelting: S1.1. According to the chemical composition requirements of the inner and outer layers of the roll sleeve for rolling mill frame of new high-speed steel angle steel, pig iron, scrap steel, material head, alloy, etc. are added to different medium frequency furnaces in sequence to obtain qualified molten steel in the inner and outer layers. S1.2 The outer layer of molten steel is tapped at 1580℃, and the inner layer of molten iron is tapped at 1550℃ for rapid tapping. S2, Centrifugal casting: S2.1 The centrifuge speed is controlled at 500 r / min. When casting the outer layer, 1.0 kg / t of glass slag is added with the flow. S2.2 The time interval between the outer layer and the inner layer is controlled at 10 minutes. After the time is up, pour in the molten steel for the inner layer. S3. Heat treatment: After rough machining of the roller ring, it undergoes high-temperature quenching and three tempering cycles. The quenching temperature is controlled at 1150℃, and the tempering temperature is controlled at 560℃.

[0022] S4. Precision turning: The roll sleeves for rolling the angle steel finished product stand are machined to the finished product size. The inner hole is precision ground using a grinding machine. The inner hole size must achieve an interference fit with the roll shaft of the angle steel finished product stand rolling mill, and the interference amount is controlled within 1.2‰.

[0023] S5. Assembly: S5.1. Place the rolls for rolling the angle steel finished product frame into a low-temperature resistance furnace, preheat to 320℃, and hold for 20 hours; S5.2 After preheating and heat preservation of the roll sleeves for rolling angle steel finished product frame, quickly remove them from the furnace and place them on the hot charging pit; S5.3 Use a crane to lift the pre-processed angle steel finished product stand rolling mill roll shafts. The roll shaft assembly part is processed by a grinding machine. The roll shaft quickly passes through the roll sleeve of the angle steel finished product stand rolling mill for hot loading. S5.4 After hot mounting, wrap the rectification roller sleeve with aluminum silicate needled blanket and allow it to cool slowly. The aluminum silicate needled blanket can be removed when the slow cooling temperature is ≤50℃.

[0024] The performance of the roll manufactured in this embodiment is compared with that of a conventional roll as follows: Hardness / HSD Single rolling quantity / t Steel adhesion rate Standard angle steel material 50-60 200 80% Composite high-speed steel 85-95 1000 0 In the above embodiments, a rolling mill roll for angle steel finished product frame rolling and a manufacturing method are provided. The rolling mill roll prepared in this embodiment is applied to the production of angle steel finished product frame rolling. The single rolling capacity reaches 1000t, there is no steel sticking phenomenon, the online service time of the rolling mill roll is extended by 5 times compared with conventional semi-steel material rolling mill rolls, the rolled angle steel products have high dimensional accuracy and good surface quality, and the first pass rate is increased to over 99.5%.

[0025] 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 rolling mill roll for rolling angle steel finished products, characterized in that: The roll is a mating structure of a roll shaft and a roll sleeve. The roll sleeve is a composite material structure formed by centrifugal casting. The composite material structure includes an outer wear-resistant working layer and an inner tough core. The roll shaft is made of high-toughness forged steel.

2. The rolling mill roll for angle steel finished product frame rolling according to claim 1, characterized in that: The outer wear-resistant working layer of the roller sleeve composite material structure is made of a new type of high-speed steel, and the inner tough core is made of graphite steel.

3. A rolling mill roll for rolling angle steel finished product frame according to claim 2, characterized in that: The chemical composition of the outer wear-resistant working layer, by mass percentage, includes: C 1.5-2%, Si 0.5-1.0%, Mn 0.6-1.2%, Cr 4.0-6.0%, Ni 1.0-2.0%, Mo 3.0-6.0%, V 4.0-6.0%, Nb 0.5-1.0%, with the remainder being Fe and unavoidable impurities; The chemical composition of the inner tough core, by mass percentage, includes: C 0.8-1.5%, Si 1.2-1.8%, Mn 0.5-1.0%, Cr ≤0.3%, Ni ≤0.5%, Mo ≤0.5%, with the remainder being Fe and unavoidable impurities.

4. A method for manufacturing rolls for rolling angle steel finished product frames, characterized in that: The method for manufacturing the roll according to any one of claims 1-3 comprises the following steps: S1, Smelting; S2, centrifugal casting; S2.

1. Control the centrifuge speed at 400-600 r / min. When pouring the outer wear-resistant working layer of molten steel, add 0.5-1.0 kg / t of glass slag with the flow. S2.2 The pouring interval between the outer wear-resistant working layer and the inner tough core is controlled to be 5-10 minutes. After the interval is reached, the inner layer of molten steel is poured into the inner side of the formed outer wear-resistant working layer. S3. Heat Treatment: After rough machining, the centrifugally cast roller rings undergo high-temperature quenching and multiple tempering treatments. The quenching temperature is controlled at 1100-1200℃, and the tempering temperature is controlled at 540-580℃. S4. Precision machining: The heat-treated roller sleeve is machined to the preset finished size. The inner hole of the roller sleeve is precision ground by a grinding machine. The inner hole size after precision grinding forms an interference fit with the roller shaft assembly part. The interference is controlled at 1.0-1.2‰. The assembly parts of the roller shaft are also machined using a grinding machine, with machining precision matching the inner hole of the roller sleeve to ensure an interference fit of 1.0-1.2‰. S5, Roller shaft-roller sleeve interference fit; S5.

1. Place the precision-machined roller set into a low-temperature resistance furnace for preheating at a temperature of 250-350℃ and a holding time of 10-20h. S5.2 After the roller sleeve is preheated and kept warm, it is taken out of the furnace within 8 minutes and placed on the hot charging pit. The hot charging pit is a circular reinforced concrete structure with a pit opening diameter of φ700mm and a pit depth of ≥2m. S5.

3. Use a crane to lift the processed roller shaft, so that the roller shaft passes through the inner hole of the roller sleeve to complete the heat assembly; S5.4 After the hot fitting is completed, the roller sleeve is subjected to slow cooling treatment. The roller sleeve is wrapped with heat insulation material until the roller sleeve temperature is ≤50℃.

5. A method for manufacturing rolls for rolling angle steel finished product frames according to claim 4, characterized in that, Step S1 includes the following steps: S1.1 According to the chemical composition requirements of the outer wear-resistant working layer and the inner tough core, pig iron, scrap steel, raw material and alloy are added to different medium frequency furnaces in a preset order for smelting to obtain qualified outer and inner molten steel. S1.2 Control the outer layer of molten steel to exit the furnace at a temperature of 1550-1600℃ and the inner layer of molten steel to exit the furnace at a temperature of 1500-1560℃.

6. A method for manufacturing a roll for rolling an angle steel finished product frame according to claim 4, characterized in that: In step S3, the quenching temperature is 1100-1160℃, and the quenching holding time is 8-12h; the tempering is performed 3 times, and the holding time for each tempering is 30-50h.

7. A method for manufacturing a roll for rolling angle steel finished product frame according to claim 4, characterized in that: The insulation material in step S5.4 includes aluminum silicate needled blanket, which is removed after the roller sleeve cools naturally to ≤50℃.