High-alloy forged steel roller material for rolling automobile sheet and manufacturing method of high-alloy forged steel roller material

Abstract

The invention discloses a high-alloy forged steel roller material for automobile sheet rolling and a manufacturing method thereof, and is characterized in that the high-alloy forged steel roller material comprises the following chemical components in percentage by mass: 0.40-0.80% of carbon, 0.80-1.00% of silicon, 0.40-1.0% of manganese, less than or equal to 0.020% of phosphorus, less than or equal to 0.010% of sulfur, 4.00-6.00% of chromium, 0.40-1.0% of nickel, 1.40-2.40% of molybdenum, 0.90-1.80% of vanadium, and the balance of iron and inevitable trace impurities with the content of less than 0.01. Compared with the prior art, the method has the characteristics of high yield and stable quality in roller blank preparation, and has the characteristics of high roughness retentivity and grindability in final roller forming processing, and compared with the prior art, the method has the advantages of high roughness retentivity and grindability.

Description

Technical Field

[0001] The invention relates to the technical field of high alloy forged steel roll preparation, in particular to a high alloy forged steel roll material for automobile plate rolling and a manufacturing method thereof. Background Art

[0002] In recent years, with the development demand for lightweight, high-strength and high-surface quality of cold-rolled automotive steel, as well as the improvement of the quality and efficiency of cold-rolled roller grinding, high requirements have been put forward for the roughness retention performance, wear resistance, and grindability of the rollers. Companies such as Ax, Hitachi, and Steinhoff have successively developed high-speed steel rollers, whose carbon and alloy element content in the composition design has been greatly increased, with high wear resistance and accident resistance, which has improved the rolling stability at the customer end and reduced the rolling accident rate; however, due to the high content of alloy components such as C, Cr, Mo, V, and W in high-speed steel rollers, the difficulty of roller blank preparation has been greatly increased, and high requirements have been put forward for steel smelting, electroslag and forging processes. The high content of alloy elements is prone to component segregation, carbide enrichment, and segregation during the roller blank smelting process, and it is difficult to effectively eliminate eutectic carbides and original cast structure defects during the forging process. If the forging temperature is not selected properly, cracking and other phenomena will occur. The scrap rate of roll blank preparation remains high and the quality stability is poor, which brings great difficulties to the delivery and smooth promotion of high-speed steel roll products. Secondly, due to the high content of alloy elements in high-speed steel rolls, there is a high risk of cracking during heat treatment during the manufacturing process. It is difficult to meet the technical indicators of high hardness and low residual stress according to the existing heat treatment process. In addition, the high proportion of alloy elements forms carbides with high wear resistance. It is difficult to grind to the roughness and surface quality requirements required for rolling during the grinding process, which reduces the grinding efficiency of rolls and restricts the promotion and application of high-speed steel rolls.

[0003] Therefore, based on the above technical problems, the present application proposes a high alloy forged steel roll material for automobile plate rolling with high roughness retention and grindability and a manufacturing method thereof. Summary of the invention

[0004] The object of the present invention is to overcome the deficiencies of the prior art and to provide a high alloy forged steel roll material for automobile plate rolling with high roughness retention and grindability and a method for manufacturing the same.

[0005] In order to achieve the above-mentioned purpose, the present invention provides a high-alloy forged steel roll material for automobile plate rolling and a manufacturing method thereof, which is characterized by being composed of the following components, and its chemical composition is expressed in mass percentage: carbon 0.40-0.80, silicon 0.80-1.00, manganese 0.40-1.0, phosphorus ≤0.020, sulfur ≤0.010, chromium 4.00-6.00, nickel 0.40-1.0, molybdenum 1.40-2.40, vanadium 0.90-1.80, and the remainder is iron and inevitable trace impurities with a content of less than 0.01.

[0006] Furthermore, the preparation method for electroslag remelting includes the following steps: 1) After the consumable electrode is slowly cooled, the iron oxide scale on the surface of the consumable electrode is removed by a rotary peeling machine; 2) The electroslag remelting slag system adopts a ternary slag system of CaF2, CaO, and Al2O3; 3) Add appropriate amount of aluminum powder at the beginning of electroslag remelting; 4) During the electroslag remelting process, high-resistance slag is used with a large filling ratio for production; 5) During remelting, the melting rate is controlled at (720-680) kg / h.

[0007] Furthermore, the preparation method for forging a roll blank comprises the following steps: 1) Use the upper semicircular anvil and lower flat anvil forging method; place the ingot riser upward during the blanking and upsetting process; 2) The forging heating temperature is 1150~1180℃, of which the initial forging temperature is 1120~1150℃; 3) According to the forging ratio and product size, three-fire forging is adopted, in which the furnace temperature is appropriately lowered in the last fire to reduce the final forging temperature; 4) Post-forging heat treatment is divided into two normalizing and one spheroidizing annealing; ①One-time normalizing: that is, preheating and normalizing after forging; air cooling to 500℃ after forging, and then supercooling to about 250℃ in the furnace after air cooling; ② Secondary normalizing: heat the workpiece to 1030℃ for 8 hours, then take it out of the furnace and air cool it; ③ Spheroidizing annealing: Heat the workpiece to 500~600℃ for 4 hours, then heat it to 900±5℃ (isothermal coefficient is 2min / mm), furnace cool it to 700~750℃ (isothermal coefficient is 2min / mm), then furnace cool it to ≤400℃ and continue to air cool it to room temperature.

[0008] 5) In the final heat treatment, the quenching temperature is short-time heating at 1040~1060℃, and the tempering is secondary high-temperature tempering at 500~550℃; 6) Ultra-deep cryogenic treatment is performed between the two high-temperature tempering processes, that is, the workpiece is placed in a closed liquid nitrogen cooling box and kept at -120°C for 3 to 4 hours.

[0009] Furthermore, a specially designed grinding wheel is used to grind the workpiece after the heat treatment, so that the surface roughness of the workpiece after grinding is in the range of Ra0.8~1.0.

[0010] The present invention adopts the above-mentioned solution, and its beneficial effects are: In the preparation of roll blanks, it has the characteristics of high yield rate and stable quality, which reduces the production cost. Secondly, in the final forming process of the rolling mill rolls, it has the characteristics of high roughness retention and grindability, which are greatly improved compared with the existing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the structure of the upper anvil and the lower anvil in the blank forging in this embodiment. DETAILED DESCRIPTION

[0012] In order to facilitate the understanding of the present invention, the present invention is described more fully below with reference to the accompanying drawings. The accompanying drawings provide preferred embodiments of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. The purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly and comprehensively understood.

[0013] In this embodiment, a high alloy forged steel roll material for automobile plate rolling and a manufacturing method thereof are composed of the following components, and their chemical compositions are expressed in mass percentage: carbon 0.40-0.80, silicon 0.80-1.00, manganese 0.40-1.0, phosphorus ≤0.020, sulfur ≤0.010, chromium 4.00-6.00, nickel 0.40-1.0, molybdenum 1.40-2.40, vanadium 0.90-1.80, and the remainder is iron and unavoidable trace impurities with a content of less than 0.01. Specifically, the alloy element content of the conventional cold rolling work roll material is less than 6%. In this embodiment, the work roll material The alloy element content is between 8% and 9%, and at the same time, its carbide content increases accordingly, thereby meeting the high wear resistance and accident resistance requirements of the working roll; secondly, avoid increasing the alloy element content, and give full play to the characteristics of alloy carbides and matrix structure through optimized design of alloy element ratio, so that the material has the high wear resistance and accident resistance of general high-speed steel rolls at the use end; in addition, through process control of alloy carbide type, morphology, proportion, distribution, etc., the material has higher grindability, avoiding excessive alloy element content that leads to a significant decrease in roll grindability, thereby reducing the production efficiency of the grinding roll room and the efficiency of roll use and maintenance.

[0014] Furthermore, the preparation method for electroslag remelting includes the following steps: 1) After the consumable electrode is slowly cooled, the oxidized iron scale on the surface of the consumable electrode is removed by a rotary peeling machine, thereby reducing the further oxidation of the consumable electrode and the generation of new inclusions during the electroslag remelting process; 2) The electroslag remelting slag system adopts a ternary slag system of CaF2, CaO, and Al2O3. Specifically, CaF2 can reduce the melting point, viscosity, and surface tension of the slag, CaO can increase the basicity of the slag and improve the desulfurization efficiency, and Al2O3 can significantly reduce the electrical conductivity of the slag, reduce power consumption, and improve productivity. Through the combination of the above ternary slag system, the absorption of moisture from the atmosphere during the production process can be minimized, and the hydrogen content in the steel ingot can be increased after electroslag remelting (w(H)≤ ), which improves the purity of molten steel; 3) Adding an appropriate amount of aluminum powder at the beginning of electroslag remelting can reduce the concentration of FeO and SiO2 in the slag, thereby ensuring the overall composition of the produced steel ingots is consistent; 4) During the electroslag remelting process, high-resistance slag is used with a large filling ratio for production. Specifically, the above filling ratio is preferably 0.7. During the electroslag remelting, the shape of the end of the consumable electrode is close to a plane, and the metal molten pool is shallow and flat, thereby increasing the size of the cylindrical section on the side of the metal molten pool and improving the crystal quality of the steel ingot; secondly, after the high-temperature homogenization treatment of the steel ingot, it has a certain diffusion effect on the carbide segregation, which helps to reduce the level of point segregation; 5) During remelting, the melting rate is controlled at (720-680) kg / h, which is more convenient for forming a shallow and flat metal molten pool, thereby reducing segregation defects.

[0015] Furthermore, the preparation method for forging a roll blank comprises the following steps: 1) Use the upper semicircular anvil and lower flat anvil forging method; place the ingot riser upward during the blanking and upsetting process. For details, see the attached Figure 1 As shown in the figure, combined with the characteristics of high deformation resistance and low thermoplasticity of high alloy steel, the ingot riser is placed upward during the blanking and upsetting process. The semicircular design of the upper anvil during upsetting can press the edge of the ingot downward, forming a bulge in the middle concave part, making the riser end defect convex, thereby obtaining a good end forging structure, reducing the riser defect removal, and improving the yield rate of the roll blank; 2) The forging heating temperature is 1150~1180℃, of which the initial forging temperature is 1120~1150℃; 3) According to the forging ratio and product size, three-fire forging is adopted, in which the furnace temperature is appropriately lowered in the last fire, and the final forging temperature is lowered. It should be noted that, combined with the characteristics of high-alloy steel materials, the forging temperature range is narrow and the deformation increases with the deformation, the work hardening effect is obvious, the core is prone to forging cracks, and the surface and end faces are prone to cracks due to excessive cooling, etc., by adopting three-fire forging and appropriately lowering the furnace temperature in the last fire, the final forging temperature is lowered, so as to achieve the purpose of controlling network carbides and grain growth; 4) The post-forging heat treatment is divided into two normalizing and one spheroidizing annealing, which is more convenient for further grain refinement of the workpiece, making the carbide distribution more uniform, and improving the network carbide generated during the forging process; ①One-time normalizing: that is, preheating and normalizing after forging; air cooling to 500℃ after forging, and then supercooling to about 250℃ in the furnace after air cooling; ② Secondary normalizing: heat the workpiece to 1030℃ for 8 hours, then take it out of the furnace and air cool it; ③ Spheroidizing annealing: Heat the workpiece to 500~600℃ for 4 hours, then heat it to 900±5℃ (isothermal coefficient is 2min / mm), furnace cool it to 700~750℃ (isothermal coefficient is 2min / mm), then furnace cool it to ≤400℃ and continue to air cool it to room temperature.

[0016] 5) In the final heat treatment, the quenching temperature is short-time heating at 1040~1060℃, and the tempering adopts secondary high-temperature tempering at 500~550℃, so as to give full play to the characteristics of secondary hardening of the formed workpiece (the surface hardness of the rolling mill can reach above 64HRC).

[0017] 6) Ultra-deep cryogenic treatment is performed between the two high-temperature tempering processes, that is, the workpiece is placed in a closed liquid nitrogen cooling box and kept at -120°C for 3 to 4 hours, so that the unstable phase in the workpiece is further transformed into a stable martensite structure, while reducing the content of residual austenite structure and improving the organizational stability of the workpiece.

[0018] Furthermore, a specially designed grinding wheel is used to grind the workpiece after the heat treatment, so that the surface roughness of the workpiece after grinding is in the range of Ra0.8~1.0. It should be noted that the main raw material of the specially designed grinding wheel is preferably 5SG abrasive, which starts from small submicron particles and is made into abrasive grains through processes such as drying, crushing, and sintering, so that the abrasive grains become a collection of tiny (submicron) ceramic grains with extremely high purity of aluminum oxide, so that each abrasive grain contains billions of grains, so that the abrasive grains of the grinding wheel become more firm and have the characteristics of crushability, so that the surface roughness of the roller after grinding can be controlled in the range of Ra0.8~1.0, and the surface has no defects such as short scratches, spiral marks, and chatter marks, which can meet the rolling needs of high-grade automotive plates.

[0019] The embodiments described above are only preferred embodiments of the present invention and are not intended to limit the present invention in any form. Any technician familiar with the art who, without departing from the scope of the technical solution of the present invention, makes more possible changes and modifications to the technical solution of the present invention using the technical content disclosed above, or modifications are all equivalent embodiments of the present invention. Therefore, any equivalent and equivalent changes made according to the ideas of the present invention without departing from the content of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A high alloy forged steel roll material for automobile sheet rolling and a manufacturing method thereof, characterized in that It is composed of the following components, and its chemical composition is expressed in mass percentage: carbon 0.40-0.80, silicon 0.80-1.00, manganese 0.40-1.0, phosphorus ≤0.020, sulfur ≤0.010, chromium 4.00-6.00, nickel 0.40-1.0, molybdenum 1.40-2.40, vanadium 0.90-1.80, and the balance is iron and inevitable trace impurities with a content of less than 0.

01.

2. The high alloy forged steel roll material for automobile sheet rolling and the manufacturing method thereof according to claim 1, characterized in that: The preparation method for electroslag remelting processing comprises the following steps: 1) After the consumable electrode is slowly cooled, the iron oxide scale on the surface of the consumable electrode is removed by a rotary peeling machine; 2) The electroslag remelting slag system adopts a ternary slag system of CaF2, CaO, and Al2O3; 3) Add appropriate amount of aluminum powder at the beginning of electroslag remelting; 4) During the electroslag remelting process, high-resistance slag is used with a large filling ratio for production; 5) During remelting, the melting rate is controlled at (720-680) kg / h.

3. The high alloy forged steel roll material for automobile sheet rolling and the manufacturing method thereof according to claim 1, characterized in that: The preparation method for forging a roll blank comprises the following steps: The forging method of upper semicircular anvil and lower flat anvil is adopted; during the process of blanking and upsetting, the ingot is placed with the riser facing upwards; The forging heating temperature is 1150~1180℃, of which the initial forging temperature is 1120~1150℃; According to the forging ratio and product size, three-fire forging is adopted, in which the furnace temperature is appropriately lowered in the last fire to reduce the final forging temperature; The post-forging heat treatment is divided into two normalizing and one spheroidizing annealing; ①One-time normalizing: that is, preheating and normalizing after forging; air cooling to 500℃ after forging, and then supercooling to about 250℃ in the furnace after air cooling; ② Secondary normalizing: heat the workpiece to 1030℃ for 8 hours, then take it out of the furnace and air cool it; ③ Spheroidizing annealing: heat the workpiece to 500~600℃ for 4 hours, then heat it to 900±5℃ for 2min / mm, furnace cool it to 700~750℃ (isothermal coefficient is 2min / mm), then furnace cool it to ≤400℃ and continue to air cool it to room temperature; In the final heat treatment, the quenching temperature is short-time heating at 1040~1060℃, and the tempering is secondary high-temperature tempering at 500~550℃; Ultra-deep cryogenic treatment is carried out between the two high-temperature tempering processes, that is, the workpiece is placed in a closed liquid nitrogen cooling box and kept at -120℃ for 3 to 4 hours.

4. The high alloy forged steel roll material for automobile sheet rolling and the manufacturing method thereof according to claim 1, characterized in that: A specially designed grinding wheel is used to grind the workpiece after heat treatment, so that the surface roughness of the workpiece after grinding is within the range of Ra0.8~1.0.

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