A 5%Cr cold rolling working roll and its preparation method

Abstract

The invention discloses a 5%Cr cold rolling work roll and a preparation method thereof, belonging to the technical field of roll manufacturing. The chemical components and weight percentages of the material are: C0.80-1.20%; Si0.40-1.50%; Mn0.20-1.00%; Cr4.50-6.50%; Mo0.20-1.00%; W0.50-1.50%; Nb0.10-0.50%; S≤0.025%; P≤0.025%; the rest are Fe and inevitable impurities. The preparation process is: a cold rolling roll billet is prepared according to each chemical component and content, the cold rolling roll billet is subjected to rough turning and quenching and tempering treatment, and the roll body is subjected to quenching and tempering treatment. The invention adds microalloys for modification treatment, which plays a role in improving the size, shape and distribution of carbides, refining grains, and strengthening the matrix, and the final roll body hardness reaches 90HSD-100HSD.

Description

Technical Field

[0001] The invention belongs to the technical field of roller manufacturing, and in particular relates to a 5% Cr cold rolling working roller and a preparation method thereof. Background Art

[0002] Cold rolling production is developing towards thin plate, high precision, high strength and high efficiency, which puts higher requirements on the performance of cold rolling rolls. Cold rolling rolls should continuously improve Cr5% and roughness retention, so as to extend the roll replacement cycle and ensure the surface quality of the plate. At present, cold rolling rolls generally use Cr5 material. On the basis of Cr content of 5%, a small amount of alloy elements such as Mo and V are added. Mo and V are carbide forming elements, which form carbides in steel as wear-resistant particles. When rolling ordinary carbon steel, the rolling force is small and the deformation resistance of the rolled material is small. Conventional Cr5 material cold rolling work rolls can meet its use requirements. With the increase in the proportion of high-value-added plates such as high-strength steel and silicon steel rolled by major steel mills, the deformation resistance during rolling increases, the surface quality requirements are improved, and the production efficiency of the rolling mill is improved, which requires the roll to be on the machine for a longer time to reduce the number of roll changes, and puts higher requirements on the wear resistance of the roll. Summary of the invention

[0003] The object of the present invention is to provide a 5% Cr cold rolling work roll and a preparation method thereof, which can improve the wear resistance and machine time of the Cr5 material cold rolling roll.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is:

[0005] A 5% Cr cold rolling work roll, the chemical components and weight percentage of the material are: C0.80-1.20%; Si0.40-1.50%; Mn0.20-1.00%; Cr4.50-6.50%; Mo0.20-1.00%; W0.50-1.50%; Nb0.10-0.50%; S≤0.025%; P≤0.025%; the rest are Fe and unavoidable impurities.

[0006] A further improvement of the technical solution of the present invention is that the chemical components and weight percentages of the material are: C 0.85-0.95%; Si 0.6-1.00%; Mn 0.25-0.8%; Cr 4.80-6.0%; Mo 0.25-0.50%; W 0.60-1.20%; Nb 0.12-0.25%; S 0.003-0.012%; P 0.009-0.016%; the rest are Fe and unavoidable impurities.

[0007] A method for preparing a 5% Cr cold rolling work roll comprises the following steps:

[0008] Step A: preparing steel raw materials according to the chemical components and weight percentages in the cold rolling roll material, preparing roll blanks according to the roll blank production process, first smelting molten steel and then casting into electrode rods, annealing, electroslag remelting, forging, and turning to obtain roll blanks;

[0009] Step B performs rough turning and quenching and tempering treatment on the cold rolling roll steel billet;

[0010] Step C: quenching and tempering heat treatment of the roller body;

[0011] Step D is to perform fine processing on the roller blank, and the roller body hardness reaches 90-100 HSD.

[0012] A further improvement of the technical solution of the present invention is that: in step A, an electric arc furnace and a LF / VD refining furnace are used for smelting steel, microalloying is added after good deoxidation, the molten steel is molded into an electrode rod, and then the electrode rod is annealed, and then the electrode rod is made into an electroslag ingot by an electroslag remelting method. After the composition is tested to be qualified, the electroslag ingot is heated and forged into a forging blank, the forging blank is heat treated, and finally turned, and it can be used as a roller blank after passing the inspection.

[0013] The further improvement of the technical solution of the present invention is that when molten steel is smelted, microalloy is added to perform modification treatment under sufficient deoxidation, the microalloy composition is V 75-85%, N 15-25%, and the amount of microalloy added is 0.05-0.20%.

[0014] The further improvement of the technical solution of the present invention is that the specific process of the tempering treatment is: heating the cold-rolled roller billet after rough turning to 860-900°C and keeping it at this temperature for 8-12 hours; water quenching the roller billet after keeping it at this temperature for 15-30 minutes, and then heating the roller billet to 600-650°C for high-temperature tempering for 20-30 hours.

[0015] A further improvement of the technical solution of the present invention is that the specific process of quenching treatment in step C is: transferring the cold-rolled roller billet after quenching and tempering treatment to a dual-frequency induction quenching device, the quenching temperature is 930 to 970°C, the quenched roller billet enters a liquid nitrogen medium at -150 to -60°C for deep cooling, the deep cooling time is 4 to 10 hours, the deep-cooled roller billet is warmed up to room temperature in the air, and then the roller billet is heated to 120 to 200°C for low-temperature tempering, and the low-temperature tempering time is 48 to 120 hours.

[0016] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is:

[0017] Under the same use conditions, the roll replacement cycle of the cold rolling roll of the present invention is increased by more than 30% compared with the roll made of conventional Cr5 material.

[0018] The present invention has made great improvements in the chemical composition and weight percentage of the cold rolling roller material. The present invention increases the W content. W is a strong carbide-forming element, which forms high-hardness WC carbide, so that the roller has high hardness and good wear resistance. As a strong carbide-forming element, W has a higher hardness than carbides of elements such as Cr and Mo, and can significantly improve the wear resistance of the roller. However, W is easy to form large carbides, so how to improve the morphology and distribution of carbides and obtain a good organizational state is the key to ensuring the performance of the roller. V, N, and Nb, as microalloying elements, have the effects of improving the size, morphology and distribution of carbides, refining grains, and strengthening the matrix. At the same time, in order to give full play to the precipitation strengthening effect of V in steel, the chemical ratio of V and N in steel is close to 3.6, and V microalloying is carried out in the form of V-N alloy. Using VN alloy, every 0.01% V added can bring in 0.001% N in ionic state. Increasing the nitrogen content in steel can save 20 to 33% of the alloying element V under the same precipitation strengthening effect.

[0019] The present invention makes a great improvement on the smelting process of the cold rolling roll, and adds microalloys for modification, such as V, N, Nb and other microalloying elements, to improve the size, morphology and distribution of carbides, refine the grains and strengthen the matrix. The uniformity of the microstructure is significantly improved and the grain size is significantly refined. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below in conjunction with embodiments:

[0021] Example 1

[0022] (1) Refining steel materials, making the chemical composition and content of the steel materials reach the required range, and using relevant production processes to produce cold-rolled roll blanks. Specifically, the steel raw materials are smelted in an electric arc furnace and a LF / VD refining furnace, and after good deoxidation, microalloying is added for modification. The microalloy composition is V79%, N21%, and the addition amount is 0.1%. The molten steel is molded into electrodes, and then the electrode rods are annealed, and then the electrode rods are made into electroslag ingots by electroslag remelting.

[0023] After final testing, the chemical components and percentages of the electroslag ingot in this embodiment are as follows:

[0024] C The Mn Cr You V W Nb P S 0.88 0.65 0.28 4.90 0.33 0.08 0.66 0.16 0.017 0.005

[0025] The rest is Fe and unavoidable impurities. After the composition is qualified, the electroslag ingot is heated, forged into a forging blank, heat treated, and finally turned. After passing the inspection, it can be used as a roll blank;

[0026] The roll blank is subjected to preliminary heat treatment and the roll body is subjected to quenching and tempering heat treatment, and the roll body hardness reaches 95HSD.

[0027] (2) Rough turning and tempering treatment of the roller blank.

[0028] Specifically, the rough-turned roll blank is heated to 900°C and kept at this temperature for 8 hours; the kept roll blank is water quenched for 20 minutes, and then the roll blank is heated to 630°C for high-temperature tempering for 21 hours.

[0029] (3) Quenching and tempering the roller blank.

[0030] Specifically, the roller blank after quenching and tempering treatment is transferred to a dual-frequency induction quenching device with a heating temperature of 970°C. The quenched roller blank enters a liquid nitrogen medium at -130°C for deep cooling for 5 hours. The deep-cooled roller blank is warmed up to room temperature in the air, and then heated to 130°C for low-temperature tempering for 80 hours.

[0031] (4) The roller blank is finely processed to obtain a cold-rolled roller.

[0032] Embodiment 2 to Embodiment 6

[0033] The manufacturing methods of each embodiment are the same as that of embodiment 1. The process conditions, chemical components and percentages in the cold rolling roller material, and the surface hardness of the finished product are shown in the following table:

[0034]

[0035]

Claims

1. A 5%Cr cold rolling work roll, characterized in that: The chemical components and weight percentage of the material are: C 0.80~1.20%; Si 0.40~1.50%; Mn 0.20~1.00%; Cr 4.50~6.50%; Mo 0.20~1.00%; W 0.50~1.50%; Nb 0.10~0.50%; S ≤ 0.025%; P ≤ 0.025%; the rest are Fe and unavoidable impurities.

2. A 5%Cr cold rolling work roll according to claim 1, characterized in that: The chemical components and weight percentage of the material are: C 0.85~0.95%; Si 0.6~1.00%; Mn 0.25~0.8%; Cr 4.80~6.0%; Mo0.25~0.50%; W 0.60~1.20%; Nb 0.12~0.25%; S 0.003~0.012%; P 0.009~0.016%; the rest are Fe and unavoidable impurities.

3. A method for preparing a 5%Cr cold rolling work roll, characterized in that: The following steps are involved: Step A: preparing steel raw materials according to the chemical components and weight percentages in the cold rolling roll material, preparing roll blanks according to the roll blank production process, first smelting molten steel and then casting into electrode rods, annealing, electroslag remelting, forging, and turning to obtain roll blanks; Step B: performing rough turning and quenching and tempering treatment on the cold rolling roll steel billet; Step C: quenching and tempering heat treatment of the roller body; Step D is to finish the roller blank, and the roller body hardness reaches 90-100 HSD.

4. The method for preparing a 5%Cr cold rolling work roll according to claim 3, characterized in that: In step A, the steel is smelted in an electric arc furnace and a LF / VD refining furnace. After good deoxidation, microalloying is added for modification. The molten steel is molded into an electrode rod, and then the electrode rod is annealed. The electrode rod is then made into an electroslag ingot by an electroslag remelting method. After the composition is tested to be qualified, the electroslag ingot is heated and forged into a forging blank. The forging blank is heat treated and finally turned. After passing the test, it can be used as a roller blank.

5. The method for preparing a 5%Cr cold rolling work roll according to claim 4, characterized in that: During molten steel smelting, microalloys are added for modification under sufficient deoxidation conditions. The microalloy composition is V 75~85%, N 15~25%, and the amount of microalloy added is 0.05~0.20%.

6. The method for preparing a 5%Cr cold rolling work roll according to claim 3, characterized in that: The specific process of quenching and tempering treatment is: heating the cold-rolled roll billet after rough turning to 860~900℃, and keeping it at this temperature for 8~12h; water quenching the roll billet after keeping at this temperature for 15~30min, and then heating the roll billet to 600~650℃ for high temperature tempering, and the high temperature tempering time is 20~30h.

7. The method for preparing a 5%Cr cold rolling work roll according to claim 3, characterized in that: The specific process of quenching treatment in step C is as follows: the cold-rolled roll billet after quenching and tempering treatment is transferred to a dual-frequency induction quenching device, the quenching temperature is 930~970°C, the quenched roll billet enters a liquid nitrogen medium at -150~-60°C for deep cooling, the deep cooling time is 4~10h, the deep-cooled roll billet is warmed up to room temperature in the air, and then the roll billet is heated to 120~200°C for low-temperature tempering, and the low-temperature tempering time is 48~120h.

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