Pole piece roller forge piece and preparation method thereof

Abstract

The invention discloses a pole piece roller forge piece and a preparation method thereof, and relates to the technical field of equipment manufacturing, and the pole piece roller forge piece comprises the following chemical components in percentage by mass: 0.75-1.05% of C; 1.0 to 2.5 parts of Si; 0.3 to 1.0 part of Mn; p: less than or equal to 0.015; s: less than or equal to 0.010; 1.0 to 2.0 parts of Cr; 0.01 to 0.1 part of Nb; v: 0.05 to 0.25 part; mo: less than or equal to 0.2; ni + Cu: less than or equal to 0.6; n is greater than or equal to 200 ppm, and the balance is Fe and inevitable impurities. By optimizing chemical components (for example, the use of precious alloy elements such as Cr and Mo is reduced, and the content of Si is increased), the material cost is remarkably reduced while the performance is guaranteed. Meanwhile, elements such as Nb, V and N are added to form tiny carbonitride, the effects of composite microalloying and grain refining can be achieved, then the high-temperature hardness maintaining capacity of the material is remarkably improved, and the problems that in the prior art, under the high-temperature working condition, the hardness is poor, the material cost is high, the structure uniformity and performance stability are poor, and the high-temperature hardness attenuation is large are solved.

Description

Technical Field

[0001] This invention relates to the field of equipment manufacturing technology, and in particular to an electrode roll forging and its preparation method. Background Technology

[0002] With the development of wet-process battery electrode rolling technology, electrode rollers need to withstand higher pressure and frictional loads. Simultaneously, rolling mills are evolving towards larger diameters, wider widths, and higher speeds, placing higher demands on electrode roller manufacturing. Research has found that the operating performance of electrode rollers at different temperatures significantly affects the uniformity of electrode thickness. For example, at 20℃, the thickness uniformity is Δ≤1.9μm; at 90℃, Δ≤1.3μm; and at 160℃, Δ≤0.8μm. However, existing wet-process electrode rollers have significant shortcomings under high-temperature conditions:

[0003] On the one hand, although the hardness of traditional electrode rollers can reach 65-67 HRC at room temperature, the hardness will decrease by 8%-10% under high temperature conditions of 120-150℃. The higher the temperature, the more severe the hardness decay. Even after cryogenic treatment or multi-stage heat treatment, it is still difficult to effectively improve its ability to maintain high temperature hardness. This leads to poor uniformity of battery electrode thickness and reduced product yield, becoming a key factor restricting the improvement of wet-process battery electrode quality.

[0004] On the other hand, the commonly used high-carbon, high-chromium alloy steel materials, when using dual-frequency induction continuous quenching technology, suffer from limitations in production processes, making it difficult to fully realize the material's performance potential and effectively improve the uniformity of roller surface hardness to a higher level. Existing wet-process battery electrode rollers have significant shortcomings in terms of hardness retention under high-temperature conditions, cost control, and process stability, failing to meet the comprehensive technical requirements of the new energy battery industry for electrode rollers with high-temperature stability, ultra-high hardness, low cost, and high uniformity. Summary of the Invention

[0005] In view of the above analysis and in view of the shortcomings of the prior art, the present invention aims to provide an electrode roll forging and its preparation method, which solves at least one of the problems in the prior art such as poor hardness under high temperature conditions, high material cost, poor microstructure uniformity and performance stability, and large hardness decay at high temperature.

[0006] The objective of this invention is mainly achieved through the following technical solutions:

[0007] This invention discloses an electrode roll forging, the chemical composition of which, by mass percentage, is:

[0008] C: 0.75-1.05; Si: 1.0-2.5; Mn: 0.3-1.0; P: ≤0.015; S: ≤0.010;

[0009] Cr: 1.0-2.0; Nb: 0.01-0.1; V: 0.05-0.25; Mo: ≤0.2; Ni+Cu: ≤0.6; N: ≥200ppm, balance being Fe and unavoidable impurities.

[0010] Preferably, the N content in the chemical composition of the electrode roll forging is controlled at 200ppm-300ppm.

[0011] Preferably, the surface hardness of the electrode roll forging is ≥66HRC.

[0012] Preferably, the surface hardness of the electrode roll forging is ≥68HRC.

[0013] Preferably, the surface hardness uniformity of the electrode roll forging is within ±0.3 HRC.

[0014] Preferably, the surface roughness Ra value of the electrode roll forging is ≤0.8.

[0015] Preferably, the total Nb and V content in the chemical composition of the electrode roll forging is controlled between 0.08% and 0.1%.

[0016] Preferably, the grain size of the electrode roll forging is ≥8.

[0017] Preferably, the surface hardness of the electrode roll forging decreases by ≤2% under high temperature conditions of 140-160℃.

[0018] A method for preparing an electrode roll forging, comprising:

[0019] By reducing the Cr and Mo content in the electrode roll forgings, increasing the Si content, and adding Nb, V, and N, the material's ability to retain high-temperature hardness is improved, high-temperature hardness decay is reduced, and costs are lowered.

[0020] By sequentially processing electrode rollers through induction heating, quenching and cooling, and low-temperature tempering, the hardness decay under high-temperature conditions of 140-160℃ is reduced.

[0021] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0022] (1) This invention significantly reduces material costs while ensuring performance by optimizing chemical composition (e.g., reducing the use of expensive alloying elements such as Cr and Mo, and increasing Si content). At the same time, the addition of elements such as Nb, V, and N forms tiny carbonitrides, which improves the material's ability to retain high-temperature hardness and reduces high-temperature hardness decay. This solves the problem that existing materials are expensive and have insufficient hardness retention under high-temperature conditions, resulting in large high-temperature hardness decay. Under high-temperature conditions of 140-160℃, the hardness decay is controlled within 2%-3%.

[0023] (2) This invention obtains steel ingots with uniform composition and dense structure by strictly controlling parameters such as melting rate and slag layer thickness through electroslag remelting process, which significantly improves the uniformity of material structure and performance stability, and provides high-quality raw materials for subsequent processing; it solves the problem that traditional manufacturing processes are difficult to obtain high-quality steel ingots with uniform composition and dense structure, resulting in poor uniformity of structure and performance stability, and the maximum deviation rate of the hardness measurement value of the finished roll surface at room temperature is ≤3%.

[0024] (3) This invention employs multi-pass forging (such as “upsetting-drawing-finishing”) and strictly controls the heating temperature and holding time to ensure that the forging blank reaches the required specifications and dimensions, while eliminating the as-cast structure, refining the grains, and improving the overall performance and uniformity of the material; it solves the problem that traditional forging processes cannot guarantee the dimensional accuracy and structural uniformity of forgings, resulting in unstable performance.

[0025] (4) The present invention adopts induction hardening process combined with deep cryogenic treatment to ensure that the hardened layer depth is ≥20-25mm, the hardness uniformity after hardening is high, and the hardness decay is controlled within 2%-3% or even not decayed under high temperature conditions of 140-160℃, which significantly improves the high temperature stability and service life of the electrode roller; it solves the problem that the traditional induction hardening process is difficult to achieve a uniform hardened layer and the hardness decay is serious under high temperature conditions.

[0026] (5) The present invention adopts a low temperature tempering process of 160-200℃ to eliminate quenching stress, stabilize the martensitic structure, further control the hardness grade and uniformity of the roller body, and ensure that the electrode roller maintains high hardness and high uniformity under high temperature conditions, effectively improving product quality; it solves the problem that the existing low temperature tempering process is difficult to stabilize the martensitic structure, resulting in insufficient hardness uniformity and high temperature stability.

[0027] (6) This invention significantly improves the wear resistance and precision of the electrode roller by controlling the surface roughness (Ra≤0.8) and surface strengthening treatment (such as chrome plating or tungsten carbide spraying), further enhancing its performance under high temperature conditions, and solving the problem that the traditional electrode roller has insufficient surface wear resistance and precision, making it difficult to meet the usage requirements under high temperature conditions.

[0028] (7) This invention significantly reduces material costs by optimizing chemical composition, employing electroslag remelting, strictly controlling parameters such as melting rate and slag layer thickness, using multi-pass forging with strict control of heating temperature and holding time, employing surface roughness control (Ra≤0.8) and surface strengthening treatment, using induction hardening combined with cryogenic treatment, and employing a low-temperature tempering process at 160-200℃. Simultaneously, it exhibits excellent hardness retention, high wear resistance, and precision under high-temperature conditions, significantly improving the material's structural uniformity and performance stability. The final product demonstrates excellent performance under high-temperature conditions, meeting the high-performance requirements of the new energy battery industry for electrode rollers. Attached Figure Description

[0029] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0030] Figure 1 This is a high-magnification micrograph of the electrode roller of Embodiment 1 of the present invention.

[0031] Figure 2 This is a high-magnification micrograph of the electrode roller in Comparative Example 1. Detailed Implementation

[0032] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0033] On one hand, this invention discloses an electrode roll forging, the chemical composition of which, by mass percentage, is:

[0034] C: 0.75-1.05; Si: 1.0-2.5; Mn: 0.3-1.0; P: ≤0.015; S: ≤0.010;

[0035] Cr: 1.0-2.0; Nb: 0.01-0.1; V: 0.05-0.25; Mo: ≤0.2; Ni+Cu: ≤0.6; N: ≥200ppm, balance being Fe and unavoidable impurities.

[0036] Specifically, C is a major factor affecting the hardness and strength of forgings. It can also form carbides with Cr and Mo, and especially with N, it can combine with microalloyed Nb and V to form carbonitrides, which can play a role in precipitation strengthening and grain refinement, thereby improving the properties of steel. Considering the hardness grade, ductility and toughness requirements, and manufacturing difficulty of the invented steel, the C content is controlled between 0.75% and 1.05%.

[0037] Si, as a typical matrix strengthening element, can significantly improve the strength and hardness of steel when dissolved in it. Especially during the low-temperature tempering stage, it can significantly inhibit the activity of C in martensite, limit the formation of carbides such as Fe3C, and prevent the martensitic matrix from undergoing significant tempering softening behavior at high temperatures. However, when the silicon content in steel exceeds 3%, its plasticity and toughness will be significantly reduced. Therefore, the Si content in the steel of this invention is controlled at 1.0% to 2.5%.

[0038] Mn: As an inherent element in steel, it is a good deoxidizer and desulfurizer. In particular, Mn has a strong ability to stabilize austenite and can improve the hardenability of steel. However, Mn can also easily increase the temper brittleness sensitivity of steel. The Mn content in the steel of this invention is controlled at 0.3% to 1.0%.

[0039] P: As one of the unavoidable harmful elements in steel, the content of P in the steel of this invention is required to be ≤0.015%.

[0040] S: As one of the unavoidable harmful elements in steel, the content of S in the steel of this invention is required to be ≤0.010%.

[0041] Cr: As the most important element in steel to improve hardenability, it also has a certain secondary hardening effect, which can improve the hardness of high carbon steel without making the steel brittle; however, Cr easily forms various forms of carbides with C, and easily consumes the C content in the matrix during tempering. Therefore, the Cr content in the steel of this invention is controlled at 1.0% to 2.0%.

[0042] Mo significantly improves hardenability and hot strength, prevents temper brittleness, and enhances the tempering stability of steel, allowing parts to be tempered at higher temperatures, thereby effectively reducing residual stress and maintaining hardness. However, Mo readily combines with C to form carbides, increasing the difficulty of dissolution during final heat treatment and thus reducing the matrix strength. Furthermore, the raw material cost of this alloying element is relatively high. Therefore, the Mo content in the steel of this invention is controlled to be ≤0.2%, preferably 0.15–0.2%.

[0043] Nitrogen (Nb): A commonly used microalloying element in steel, it has a strong affinity for carbon (C) and nitrogen (N). The nitrides, carbides, or carbonitrides formed can act as precipitation strengthening agents during forging, inhibiting recrystallization. Especially during heat treatment, its difficulty in dissolving allows it to pin grain boundaries, refining the grains and ensuring quenching at higher temperatures. This better utilizes the material's potential and significantly improves the steel's overall performance. The Nb content in the invented steel is controlled at 0.01%-0.1%.

[0044] V: Similar in function to Nb, it is also a commonly used microalloying element in steel. However, when used alone, the V(CN) it forms has a low dissolution temperature, making it difficult to effectively pin grain boundaries and refine grains at higher quenching temperatures. Therefore, it is often used in combination with Nb to achieve a composite microalloying effect. The V content in the invented steel is controlled at 0.05%-0.25%.

[0045] Nitrogen (N): As the most important element in composite microalloyed steel, it is mainly used to combine with Nb and V to form composite carbonitrides, while reducing the binding of Nb and V to carbon, thereby controlling the carbon content in the matrix to maintain a high level. However, for high-carbon steel, it is difficult to achieve a high N content in engineering. The nitrogen content in the steel of this invention is controlled at not less than 200 ppm.

[0046] Ni+Cu: Not used as a major element. Considering factors such as the source of raw materials in steelmaking, the content of Ni+Cu is controlled to be ≤0.6%.

[0047] The remainder consists of Fe and unavoidable impurities.

[0048] In practice, this invention optimizes the chemical composition, particularly by adding elements such as Nb, V, and N, to form micro-carbonitrides. These carbonitrides are difficult to dissolve during heat treatment, acting as grain boundary pinning and grain refinement, thereby significantly improving the material's ability to maintain high-temperature hardness. It also reduces the amount of precious metals (such as Cr and Mo) used, significantly lowering material costs. Simultaneously, the addition of Si improves the matrix's resistance to tempering, ensuring the material maintains high hardness under high-temperature conditions. This invention solves the problems of insufficient hardness retention under high-temperature conditions in existing materials, leading to severe hardness decay and high costs of traditional materials, making it difficult to meet the comprehensive technical requirements of the new energy battery industry for electrode rollers: "high-temperature stability, ultra-high hardness, low cost, and high uniformity."

[0049] Compared with existing technologies, this invention significantly reduces material costs while maintaining performance by optimizing chemical composition (such as reducing the use of expensive alloying elements like Cr and Mo, and increasing Si content). Simultaneously, the addition of elements like Nb, V, and N forms micro-carbonitrides, improving the material's ability to retain high-temperature hardness and reducing high-temperature hardness decay. This solves the problems of high cost and insufficient hardness retention under high-temperature conditions, leading to significant high-temperature hardness decay in existing materials.

[0050] Preferably, the nitrogen content (N) in the chemical composition of the electrode roll forging is controlled at 200ppm-300ppm to further improve the precipitation strengthening effect and grain refinement ability of the material.

[0051] Preferably, the surface hardness of the electrode roll forging is ≥66HRC.

[0052] More preferably, the surface hardness of the electrode roll forging decreases by ≤2% under high temperature conditions of 140℃-160℃.

[0053] More preferably, the surface hardness uniformity of the electrode roll forging is within ±0.3 HRC.

[0054] More preferably, the surface roughness Ra value of the electrode roll forging is ≥0.8.

[0055] When implemented, the above settings can further improve dimensional stability and wear resistance under high-temperature conditions (140℃-160℃).

[0056] Compared with existing technologies, this invention significantly improves the wear resistance and precision of electrode rollers through surface roughness control (Ra≥0.8) and surface strengthening treatment (such as chrome plating or tungsten carbide spraying), further enhancing their performance under high-temperature conditions. This solves the problem that traditional electrode rollers have insufficient surface wear resistance and precision, making it difficult to meet the requirements of high-temperature conditions.

[0057] Preferably, the total Nb and V content in the chemical composition of the electrode roll forging is controlled at 0.08%-0.1% to further improve the grain size and tempering resistance.

[0058] More preferably, the grain size of the electrode roll forging is ≥8.

[0059] On the other hand, this invention discloses a method for preparing electrode roll forgings, comprising:

[0060] By reducing the Cr and Mo content in the electrode roll forgings, increasing the Si content, and adding Nb, V, and N, the material's ability to retain high-temperature hardness is improved, high-temperature hardness decay is reduced, and costs are lowered.

[0061] By sequentially processing electrode rollers through induction heating, quenching and cooling, and low-temperature tempering, the hardness decay under high-temperature conditions of 140-160℃ is reduced.

[0062] Specifically, including:

[0063] S1. Raw material preparation:

[0064] Raw materials are proportioned according to the designed chemical composition, and the chemical composition of molten steel is controlled to meet the target requirements through electric furnace roughing and vacuum refining.

[0065] S2. Steel ingot preparation:

[0066] The molten steel after vacuum refining is vacuum cast into electrode rod blanks, which are then used as consumable electrodes for electroslag remelting to obtain steel ingots.

[0067] S3. Preparation of forging blanks:

[0068] The steel ingot is forged in multiple passes, and the forging ratio is controlled to be ≥2.0 to obtain the target size electrode roll blank;

[0069] S4. Post-forging heat treatment:

[0070] The forged electrode roll blanks are subjected to normalizing, spheroidizing annealing, and hydrogen diffusion annealing to eliminate forging stress, reduce the hydrogen content in the steel, and obtain a spheroidal pearlite structure.

[0071] S5, Conditioning:

[0072] The electrode roll blanks were quenched by oil cooling and tempered at high temperature in sequence to complete the post-forging heat treatment, resulting in a uniform and fine tempered sorbite structure and a partial granular carbide metallographic structure.

[0073] S6. Final heat treatment:

[0074] The quenched and tempered electrode roll blanks are processed in the following order: induction heating of electrode rolls, quenching and cooling, and low-temperature tempering.

[0075] Induction heating: After preheating the entire electrode roller, medium frequency or power frequency induction heating is used;

[0076] Quenching and cooling: A staged quenching and cooling process is adopted using an overall spray method, and the cooling rate is controlled to exceed the critical cooling rate of the material to ensure that the hardened layer depth is ≥20-25mm;

[0077] Low-temperature tempering: The quenched electrode rolls are placed in a tempering furnace to eliminate quenching stress, stabilize the martensitic structure, and control the hardness grade and uniformity of the roll body.

[0078] In practice, this invention employs multi-pass forging (such as "upsetting-drawing-finishing") and strictly controls the heating temperature and holding time to ensure that the forging blank reaches the required size specifications. At the same time, it eliminates the as-cast structure, refines the grains, and improves the overall performance and uniformity of the material. This solves the problem that traditional forging processes cannot guarantee the dimensional accuracy and microstructure uniformity of forgings, leading to unstable performance.

[0079] This invention employs induction hardening combined with cryogenic treatment to ensure a hardened layer depth ≥20-25mm, resulting in high uniformity of hardness after hardening. Furthermore, the hardness decay is controlled within 2%-3% or even non-decay at high temperatures of 140-160℃, significantly improving the high-temperature stability and service life of the electrode roller. This invention solves the problems of traditional induction hardening processes, which struggle to achieve a uniform hardened layer and suffer severe hardness decay at high temperatures.

[0080] Specifically, step S1 includes:

[0081] S101, chemical composition by mass percentage: C: 0.75-1.05; Si: 1.0-2.5; Mn: 0.3-1.0; P: ≤0.015; S: ≤0.010; Cr: 1.0-2.0; Nb: 0.01-0.1; V: 0.05-0.25; Mo: ≤0.2; Ni+Cu: ≤0.6; N: ≥200ppm, balance being Fe and unavoidable impurities.

[0082] S102, Raw material ratio:

[0083] Based on the designed chemical composition, select appropriate raw materials (such as pig iron, scrap steel, alloying elements, etc.) and accurately proportion them to ensure that the chemical composition of the raw materials meets the design requirements, thus providing an accurate raw material basis for the subsequent smelting process.

[0084] S103, Electric furnace refining:

[0085] The proportioned raw materials are added to the electric furnace for melting and smelting. The melting and oxidation temperature is controlled at 1540℃±100℃ and the melting time is 40min±20min to ensure that the molten steel is fully melted and impurities are initially removed.

[0086] S104, Vacuum Refining:

[0087] Aluminum blocks are added to the bottom of the refining ladle as a deoxidizer. After the molten steel is poured into the refining ladle, the slag-forming agent is added in two batches. Two-thirds of the slag-forming agent is added in the first batch, and the remaining slag is added after 15 minutes. The composition of the slag-forming agent is: the mass ratio of quaternary slag system CaF2:Al2O3:CaO:MgO = 50±5:30±5:15±2:5±1.

[0088] After the slag is formed, aluminum powder is added as a deoxidizer in two batches to further remove oxygen from the molten steel, reduce the oxide content in the molten steel, improve the purity of the molten steel, and reduce the impurity content.

[0089] S105, Vacuum degassing:

[0090] Vacuum degassing is performed, requiring a vacuum level not exceeding 300 Pa, to remove gases (such as hydrogen and oxygen) from the molten steel, thereby further improving the purity of the steel.

[0091] S106. Component Analysis and Adjustment:

[0092] After vacuum degassing, temperature and composition samples are taken to check whether the chemical composition of the molten steel meets the target requirements. If the composition does not meet the requirements, fine-tuning is performed; once the chemical composition meets the target requirements, the steel is tapped, with soft argon blowing lasting 20-30 minutes at a temperature of 1500℃-1510℃, and the molten steel is poured into the tundish or ingot mold.

[0093] During implementation, by optimizing the chemical composition, especially by adding elements such as Nb, V and N, the material's ability to retain high-temperature hardness and its microstructure uniformity were improved, while costs were reduced.

[0094] Compared with existing technologies, this invention achieves significant improvements in high-temperature performance by precisely controlling the chemical composition of the molten steel. This ensures that the chemical composition of the molten steel meets design requirements, and in particular, optimized composition design (such as the addition of elements like Nb, V, and N) can significantly improve the high-temperature performance of the material. Furthermore, this invention removes gases and impurities from the molten steel through vacuum refining, ensuring the purity and uniformity of the steel composition.

[0095] Specifically, step S2 includes:

[0096] S201. Vacuum casting preparation:

[0097] Preheat the ingot mold to 120℃-200℃ to ensure that the mold is dry and the temperature is uniform, preventing cracks from forming in the molten steel during the pouring process due to excessive temperature differences. At the same time, reduce the cooling rate of the molten steel to ensure the stability of the pouring process.

[0098] S202, Vacuum casting:

[0099] The vacuum-refined molten steel is vacuum-cast to produce electrode rod blanks of specific specifications. During the casting process, argon gas is introduced into the ingot mold for 6-10 minutes, after which the argon gas pipe is removed, and the top of the ingot mold is covered before casting. The argon gas protection pressure is 0.2 kg / cm². 2 -1kg / cm 2 .

[0100] Vacuum casting and argon protection can effectively reduce the gas content in molten steel, avoid oxidation and inclusions, and ensure the purity and quality of steel ingots.

[0101] S203, Electrode rod blank preparation:

[0102] After casting, the electrode rod blank is demolded 3-4 hours later to obtain the electrode rod blank. The diameter and weight of the electrode rod blank are determined according to specific requirements, for example, a diameter of 350 mm and a weight of 3.5 tons. Producing high-quality electrode rod blanks provides suitable consumable electrodes for subsequent electroslag remelting.

[0103] The consumable electrode was annealed at a temperature of 860℃±50℃ for 25h±1h and then furnace cooled to 350℃±20℃ before being removed from the furnace.

[0104] S204, Electroslag Remelting Preparation:

[0105] The prepared electrode rod blank is installed on the electroslag remelting equipment, ensuring that the electrode rod blank is aligned with the crystallizer. This ensures that the electrode rod blank melts uniformly during the electroslag remelting process, avoiding compositional inhomogeneity and microstructural defects caused by eccentric melting.

[0106] S205, Electroslag Remelting Parameter Settings:

[0107] Based on the specifications and material characteristics of the steel ingot, the process parameters for electroslag remelting are set. Specific parameters include:

[0108] Maintain a melting rate of 500-600 kg / h;

[0109] The amount of slag is 250kg-500kg;

[0110] The slag layer thickness is 250mm-300mm;

[0111] The amount of aluminum granules used is equal to the amount of slag.

[0112] The aluminum granules are added every 5 min ± 2 min during the remelting process until the remelting is complete. After the furnace is shut down, the mixture is cooled in the crystallizer for 110 min ± 20 min before being sent to the forging process.

[0113] Slag system composition (mass ratio of CaF2:Al2O3:CaO:MgO in quaternary slag system = 50±5:30±5:15±2:5±1).

[0114] During implementation, the process parameters of electroslag remelting are precisely controlled to ensure that the steel ingot has a uniform composition and dense structure, avoiding defects such as porosity and inclusions.

[0115] S206, Electroslag Remelting Process:

[0116] Electroslag remelting was carried out under atmosphere-protected conditions;

[0117] During the remelting process, aluminum granules are added every 10 minutes for deoxidation, and the amount of aluminum granules used is equal to the amount of slag.

[0118] The remelting process continues until the electrode rod billet is completely melted. Electroslag remelting further purifies the molten steel, removing impurities and gases, while aluminum particles are used for deoxidation to ensure the purity of the steel ingot.

[0119] S207. Cooling and Inspection:

[0120] After electroslag remelting is completed, the ingot is cooled in the crystallizer for 100-120 minutes after the furnace is shut down. Then, a surface inspection is performed to clean defects such as slag grooves from the ingot surface. This ensures uniform cooling of the ingot and avoids defects such as cracks caused by excessively rapid cooling. Simultaneously, surface defects are cleaned to ensure the surface quality of the ingot.

[0121] In practice, this invention uses electroslag remelting to strictly control parameters such as melting rate and slag layer thickness to obtain steel ingots with uniform composition and dense structure, significantly improving the material's structural uniformity and performance stability, and providing high-quality raw materials for subsequent processing; it solves the problem that traditional manufacturing processes are unable to obtain high-quality steel ingots with uniform composition and dense structure, resulting in poor structural uniformity and performance stability.

[0122] Compared with existing technologies, this invention reduces the gas content in molten steel by using vacuum casting and argon protection, thus avoiding oxidation and the generation of inclusions; and by using electroslag remelting, it precisely controls process parameters to ensure that the steel ingot has uniform composition and dense structure, thus avoiding defects such as porosity and inclusions.

[0123] Specifically, step S3 includes:

[0124] S301. Cleaning of steel ingot surface:

[0125] Inspect the surface quality of the electroslag remelted ingot, clean up defects such as slag grooves and oxide scale on the surface of the ingot, ensure that the surface is clean and flat, remove surface defects, and prevent the introduction of impurities or defects in the subsequent forging process, which would affect the quality of the forging.

[0126] S302, Temperature-controlled heating:

[0127] The heating rate of the steel ingot should be controlled to ≤70℃ / h, the heating temperature should be 1130℃-1170℃, and the holding time should be calculated based on the diameter of the steel ingot, satisfying the formula:

[0128] T≥D / 100;

[0129] Where D is the diameter of the steel ingot (unit: mm) and T is the holding time (unit: h).

[0130] Objective: To ensure uniform internal temperature of steel ingots by precisely controlling heating parameters, thereby avoiding forging defects caused by uneven temperature.

[0131] S303, multi-pass forging:

[0132] According to the forging drawing and related forging process, the heated steel ingot is forged in multiple passes.

[0133] The specific process sequence for step S303 is as follows:

[0134] First upsetting: The ratio for the first upsetting should be controlled between 1.6 and 2.2;

[0135] First drawing: The forging blank after the first upsetting is drawn out, and the first drawing ratio is controlled between 2.0 and 2.6;

[0136] Reheating: After the first drawing of the forging blank, control the heating rate of the steel ingot to ≤70℃ / h, and reheat the temperature to 1130℃-1170℃. The holding time is calculated according to the diameter of the steel ingot and satisfies the formula: T≥D / 100.

[0137] Second upsetting: The reheated forging blank is then subjected to a second upsetting, with the upsetting ratio controlled between 1.8 and 2.4.

[0138] Second drawing: This involves completing the second drawing of the upset forging blank, with the first drawing ratio controlled between 2.0 and 2.6.

[0139] Finishing: The forging blank after the second drawing is finished to correct the eccentricity of the roll body and roll neck, so as to ensure the dimensional accuracy and shape of the forging blank.

[0140] During implementation, multiple forging processes are used to refine the grains, optimize the microstructure, and improve the strength and toughness of the material, while ensuring that the forging blank reaches the target size.

[0141] S304, Cooling treatment:

[0142] After forging is completed, the forging blank is subjected to air cooling or wind cooling treatment. The initial roll body temperature is ≥750℃, the cooling rate is controlled at ≥50℃ / h to avoid the precipitation of network carbides, and the temperature is cooled to 450℃.

[0143] During implementation, the cooling rate is controlled to prevent the precipitation of network carbides, thereby ensuring the uniformity of the material's structure and the stability of its performance.

[0144] Compared with existing technologies, this invention ensures the smooth progress of subsequent forging processes and avoids the introduction of impurities by cleaning surface defects of steel ingots; refines grains and breaks down as-cast structures through multi-pass forging (upsetting, drawing, and finishing), thereby improving the strength and toughness of the material; ensures that the forging blank reaches the target size, providing a high-quality blank for subsequent processing; and avoids forging defects and the precipitation of network carbides by controlling heating and cooling parameters, thus ensuring the performance stability of the material.

[0145] Specifically, step S4 includes:

[0146] S401. Furnace preparation:

[0147] The forged electrode roll blanks are hoisted into the heating furnace, ensuring that the blanks are arranged neatly to avoid contact or collision with each other, thus providing good heating conditions for the heat treatment process and ensuring uniform heating.

[0148] S402, Normalizing treatment:

[0149] Heat the blank to 950℃±50℃, and control the heating rate to ≤70℃ / h to avoid thermal stress caused by excessive temperature difference.

[0150] Continue to hold at 950℃±50℃ for 15-18 hours to ensure uniform temperature throughout the blank;

[0151] After the heat preservation is completed, the rolls are removed from the furnace and air-cooled or wind-cooled. The initial roll temperature is ≥800℃, and the temperature is cooled to about 350℃.

[0152] Specifically, the time for the entire furnace to be lowered should be controlled within 40 minutes, and the distance between rollers should be ≥0.3m to ensure the air cooling effect.

[0153] During implementation, normalizing treatment eliminates residual stress generated during forging, refines grains, improves the mechanical properties of the material, and provides a good microstructure for subsequent spheroidizing annealing.

[0154] S403, Spheroidizing Annealing:

[0155] The normalized blank is put back into the annealing furnace and heated to 810℃±50℃, and held for 15-19 hours.

[0156] Continue cooling in two stages during the annealing process:

[0157] First stage: Cool down to 710℃±20℃ and keep warm for 45-55 hours;

[0158] Second stage: Continue to control the cooling rate to ≤30℃ / h, and after cooling down to 580℃±20℃, raise the temperature to 680℃±20℃ to carry out isothermal spheroidization;

[0159] Finally, the furnace is cooled to 250℃±20℃ before being unloaded.

[0160] Objective: To obtain a spheroidized pearlite structure through spheroidizing annealing, thereby reducing the material hardness, improving machinability, and reducing brittleness, thus preparing the material for subsequent quenching and tempering treatment.

[0161] S404, hydrogen diffusion annealing:

[0162] The spheroidized annealed blank is placed in an annealing furnace and heated to 650-680℃;

[0163] Maintain this temperature for 120-150 hours to ensure sufficient diffusion and discharge of hydrogen;

[0164] After annealing, the furnace was cooled to room temperature.

[0165] Hydrogen diffusion annealing reduces the hydrogen content in steel, prevents white spot defects, and significantly improves the toughness and reliability of the material.

[0166] Compared with existing technologies, this invention effectively eliminates residual stress generated during forging through normalizing treatment, avoiding cracks or deformation during subsequent processing and use; refines grains, improving the mechanical properties of the material and enhancing its strength and toughness; obtains spheroidized pearlite structure through spheroidizing annealing, reducing material hardness, improving machinability, and reducing brittleness; and significantly reduces hydrogen content in steel through hydrogen diffusion annealing, preventing white spot defects and improving the toughness and reliability of the material.

[0167] A roughing step is provided between step S4 and step S5, including:

[0168] The heat-treated electrode roll blank is rough-machined to ensure that the basic shape, size and allowance of the electrode roll blank meet the requirements of subsequent processing.

[0169] Specifically, the roughing process includes:

[0170] S001. Pre-processing inspection:

[0171] The heat-treated electrode roll blanks are inspected for appearance and dimensions to ensure there are no cracks, deformations or other obvious defects, in order to confirm the quality of the heat-treated blanks and provide qualified blanks for rough machining.

[0172] S002, Clamping and Positioning:

[0173] Mount the electrode roll blank on a CNC lathe and clamp it with a suitable fixture (such as a three-jaw chuck, center, etc.) to ensure that the clamping is firm and the coaxiality meets the requirements, so as to ensure the stability and machining accuracy of the electrode roll during the processing and avoid machining errors caused by improper clamping.

[0174] S003, Dimensional Measurement and Planning:

[0175] Use measuring tools (such as calipers and micrometers) to measure the key dimensions of the electrode roll blank, and plan the rough machining allowance according to the drawing requirements to ensure that the dimensions and allowance after rough machining meet the requirements of subsequent finish machining, and avoid over-machining or under-machining.

[0176] S004. Rough machining of the outer diameter of the roller body:

[0177] The outer diameter of the roller body is rough-machined using carbide cutting tools;

[0178] Set the cutting parameters (such as cutting speed, feed rate, and depth of cut) according to the process requirements;

[0179] During rough machining, ensure that the machining dimensions meet the drawing requirements and leave sufficient allowance (such as a minimum turning amount of 17mm and a maximum turning amount of 20mm on one side).

[0180] S005, Rough machining of roll neck and related areas:

[0181] Rough machining is performed on the roll neck and related areas to ensure dimensional accuracy and surface quality;

[0182] Using appropriate cutting tools and cutting parameters, the roll neck is turned or ground.

[0183] Check the dimensions and surface quality after processing to ensure they meet design requirements.

[0184] This step ensures the basic shape and dimensions of the roller neck and related areas, improving the overall accuracy of the electrode roller and the convenience of subsequent processing.

[0185] S006. Size Inspection and Adjustment:

[0186] Use high-precision measuring tools (such as micrometers and calipers) to inspect the dimensions of the rough-machined electrode rollers;

[0187] Based on the test results, adjustments or reprocessing are made to any parts that do not meet the requirements.

[0188] This step ensures that the dimensional accuracy after rough machining meets the requirements of subsequent machining, avoiding machining problems caused by dimensional deviations.

[0189] Specifically, step S5 includes:

[0190] S501. Preparations before quenching:

[0191] After the electrode roll blank has undergone post-forging heat treatment, the surface is cleaned to ensure that there is no oxide scale, oil or other impurities on the surface. This ensures uniform heat transfer during quenching and avoids uneven quenching or quenching cracks caused by surface defects.

[0192] S502, Quenching and Heating:

[0193] The cleaned blank is placed in a quenching furnace and heated in sections to 910℃±50℃. The heating rate is controlled to be ≤70℃ / h to avoid thermal stress and ensure that the overall temperature of the blank is uniform, thus avoiding thermal stress and deformation caused by excessive temperature difference.

[0194] S503, thermal insulation treatment:

[0195] The blank is held at 910℃±50℃ for 15-19 hours to ensure uniform internal temperature and complete austenitization. The heat treatment ensures the uniformity of the internal structure of the blank, providing a good microstructure basis for subsequent quenching.

[0196] S504, oil quenching:

[0197] Procedure: After the heat treatment is completed, remove the forging from the furnace and perform oil quenching. The oil quenching time should be calculated based on the diameter D of the forging, at a rate of 25-30 minutes per 100mm, to ensure that the quenching process is uniform and thorough.

[0198] Objective: To obtain a uniform quenched martensitic structure through oil quenching, thereby improving the hardness and strength of the material and preventing the formation of quenching cracks.

[0199] S505, Preparations before tempering:

[0200] The quenched blank should be loaded into the tempering furnace within 10-40 minutes to avoid stress concentration caused by rapid temperature drop, ensure the smooth progress of the tempering process, and avoid uneven tempering caused by temperature differences.

[0201] S506, Tempering Heating:

[0202] The blank is heated to 610℃±50℃, and the heating rate is controlled to ≤70℃ / h to avoid thermal stress and ensure that the temperature of the blank is uniform during tempering, so as to avoid thermal stress and deformation caused by excessive temperature difference.

[0203] S507, Tempering and Insulation:

[0204] At 610℃±50℃, the specific holding time is calculated based on the diameter D of the forging, multiplied by (5h-5.5h) per 100mm thickness, to ensure a sufficient tempering process, obtain a uniform tempered sorbite structure, eliminate quenching stress through tempering and holding, stabilize the structure, and obtain good comprehensive mechanical properties, including high strength and good toughness.

[0205] S508, Cooling and Inspection:

[0206] After the heat preservation is completed, the blank is cooled to ≤250℃ and then removed from the furnace. After the blank is cooled to room temperature, a final inspection is carried out to ensure that there are no cracks, deformations or other defects, and to ensure that the quality of the heat-treated blank meets the requirements of subsequent processing and use.

[0207] Compared with existing technologies, this invention obtains a uniform quenched martensite structure through oil quenching, which significantly improves the hardness and strength of the material; and eliminates quenching stress and stabilizes the structure through tempering treatment, obtaining a uniform tempered sorbite structure, which improves the toughness and comprehensive mechanical properties of the material.

[0208] Preferably, a semi-finishing step is provided between step S5 and step S6, including:

[0209] The outer circle of the quenched and tempered electrode roll blank is semi-finished to ensure that the basic shape, size, allowance and roughness of the electrode roll blank meet the requirements of subsequent processing.

[0210] Specifically, the semi-finishing steps include:

[0211] S011. Pre-processing inspection:

[0212] The appearance and dimensions of the tempered electrode roll blanks are inspected to ensure that there are no cracks, deformations or other obvious defects, so as to confirm the quality of the blanks after tempering and provide qualified blanks for semi-finishing.

[0213] S012, Clamping and Positioning:

[0214] Mount the electrode roll blank on a CNC lathe and clamp it with a suitable fixture (such as a three-jaw chuck, center, etc.) to ensure that the clamping is firm and the coaxiality meets the requirements, so as to ensure the stability and machining accuracy of the electrode roll during the processing and avoid machining errors caused by improper clamping.

[0215] S013, Dimensional Measurement and Planning:

[0216] Use measuring tools (such as calipers and micrometers) to measure the key dimensions of the electrode roll blank, and plan the semi-finishing allowance according to the drawing requirements to ensure that the dimensions and allowance after semi-finishing meet the requirements of subsequent finishing, and avoid over-processing or under-processing.

[0217] S014, Semi-finishing of the outer diameter of the roller body:

[0218] The outer diameter of the roller body is semi-finished using carbide cutting tools;

[0219] Set the cutting parameters (such as cutting speed, feed rate, and depth of cut) according to the process requirements;

[0220] During the semi-finishing process, ensure that the machining dimensions meet the drawing requirements and leave sufficient allowance (such as a minimum single-sided turning amount of 17mm and a maximum of 20mm).

[0221] Ensure that the surface roughness after processing reaches Ra=0.8 or below.

[0222] This step, through semi-finishing, further optimizes the dimensional accuracy and surface roughness of the outer circle of the roller body, providing suitable allowance and surface quality for subsequent finishing.

[0223] S015. Dimensional Inspection and Adjustment:

[0224] Use high-precision measuring tools (such as micrometers and calipers) to inspect the dimensions of the semi-finished electrode rolls;

[0225] Based on the test results, adjustments or reprocessing are made to the parts that do not meet the requirements to ensure that the dimensional accuracy after semi-finishing meets the requirements of subsequent processing and to avoid processing problems caused by dimensional deviations.

[0226] S016, Roughness inspection:

[0227] The surface roughness of the outer cylindrical surface of the machined roller is inspected using a surface roughness tester to ensure that the surface roughness reaches Ra=0.8 or below.

[0228] This step ensures that the surface roughness meets the requirements, satisfying the wear resistance and precision needs in actual use.

[0229] S017. Balance Check:

[0230] Check the allowance of each part of the semi-finished electrode roller to ensure that the allowance is uniform and sufficient, so as to ensure that there is enough allowance for subsequent finishing and avoid processing defects caused by insufficient allowance.

[0231] S018. Cleaning and Protection:

[0232] Clean the semi-finished electrode rollers to remove surface chips and oil.

[0233] Apply rust-preventive oil or take other protective measures to prevent the processed surface from rusting or being damaged, so as to ensure the surface quality of the electrode roller during subsequent storage and transportation and prevent surface corrosion caused by environmental factors.

[0234] During implementation, semi-finishing is used to ensure that the surface roughness of the outer circle of the roller body reaches Ra=0.8 or below, so as to meet the wear resistance and precision requirements in actual use.

[0235] Specifically, step S6 includes:

[0236] S601, Preheating treatment:

[0237] The quenched and tempered electrode roll blank is preheated as a whole, with the preheating temperature controlled at 280℃±20℃ and the holding time being 15-19 hours.

[0238] During implementation, preheating reduces thermal stress caused by excessive temperature differences during induction heating, while also improving the thermal conductivity of the material to ensure the uniformity of induction heating.

[0239] S602, Induction heating:

[0240] The preheated electrode roll blank is mounted on a dedicated induction hardening integrated machine tool;

[0241] Medium-frequency induction heating is used, and the heating temperature is set to 990℃±50℃;

[0242] According to the process requirements, the heating power and time are controlled in stages:

[0243] Phase 1: 800kW±100kW, heating for 20 minutes±5 minutes;

[0244] Second stage: 480kW±100kW, heating for 20 minutes±5 minutes;

[0245] Third stage: 300kW±100kW, heating for 20 minutes±5 minutes;

[0246] Maintain the sensing frequency at 150Hz±50Hz, the rotation speed at 5 rpm±2 rpm, and the single-sided gap between the roller and the sensor at 70mm±10mm.

[0247] During implementation, induction heating is used to ensure that the surface and near-surface area of ​​the electrode roller reach a uniform austenitizing temperature, providing a good microstructure basis for quenching.

[0248] S603, Quenching and Cooling:

[0249] After induction heating is completed, overall spray quenching and cooling are performed immediately.

[0250] Control the cooling rate to exceed the material's critical cooling rate to ensure a hardened layer depth ≥20mm-25mm; quenching cooling is divided into three stages:

[0251] First stage: water pressure 0.4MPa±0.05MPa, lasting 20-30 minutes;

[0252] Second stage: water pressure 0.25MPa±0.05MPa, lasting 40-50 minutes;

[0253] Third stage: water pressure 0.15MPa±0.05MPa, lasting 90-100 minutes.

[0254] During implementation, staged quenching cooling is used to ensure that the quenching process is uniform and sufficient, avoiding quenching cracks caused by excessively rapid cooling, while obtaining a hardened layer of uniform depth.

[0255] S604, cryogenic treatment:

[0256] The quenched electrode rolls are placed in a cryogenic equipment and kept at -90℃ for 3-6 hours.

[0257] After the insulation is complete, place it in the air to defrost and return to room temperature.

[0258] Objective: To further promote the transformation of retained austenite, stabilize the microstructure, reduce residual stress, and improve the hardness and dimensional stability of the material through cryogenic treatment.

[0259] S605, Low-temperature tempering:

[0260] The cryogenically treated electrode rolls are placed in a tempering furnace and heated to 170℃±20℃.

[0261] Hold at 170℃±20℃ for 75-96 hours to ensure a thorough tempering process;

[0262] After the heat preservation is completed, the furnace is cooled to ≤50℃ before being removed from the furnace.

[0263] During implementation, low-temperature tempering is used to eliminate quenching stress, stabilize the martensitic structure, control the hardness grade and uniformity of the roller body, and ensure that the hardness decay is ≤2%-3% under high-temperature conditions of 140-160℃.

[0264] A finishing step is provided after step S6, including:

[0265] S7: Perform local machining on the roller body and related areas of the final heat-treated electrode roll blank to ensure that the surface roughness meets the requirement of Ra=0.8 or below, so as to meet the wear resistance and precision requirements in actual use.

[0266] Step S7 includes:

[0267] S701. Pre-processing inspection:

[0268] The final heat-treated electrode roll blank is visually inspected to ensure that there are no cracks, deformations or other surface defects, thereby ensuring that the surface quality of the heat-treated electrode roll blank is good and providing a qualified blank for finishing.

[0269] S702, Positioning and Clamping:

[0270] Mount the electrode roll blank on a CNC lathe and use a center rest or center for positioning and clamping to ensure that the clamping is firm and the coaxiality meets the requirements, so as to ensure the stability and machining accuracy of the electrode roll during the processing and avoid machining errors caused by improper clamping.

[0271] S703, Finishing of the outer diameter of the roller body:

[0272] The outer diameter of the roller body is precision machined using carbide cutting tools;

[0273] Set the cutting parameters (such as cutting speed, feed rate, and depth of cut) according to the process requirements;

[0274] During the finishing process, ensure that the machining dimensions meet the requirements of the drawings and that the surface roughness reaches Ra=0.8 or below.

[0275] This step involves precision machining to ensure the dimensional accuracy and surface roughness of the outer circle of the roller body, meeting the wear resistance and precision requirements in actual use.

[0276] S704, finish machining of roll neck and related areas:

[0277] The roll neck and related areas are precision machined to ensure dimensional accuracy and surface quality.

[0278] Using appropriate cutting tools and cutting parameters, the roll neck is turned or ground.

[0279] Check the dimensions and surface roughness after machining to ensure they meet design requirements.

[0280] S705, Surface roughness inspection:

[0281] The surface roughness tester is used to inspect the outer diameter of the machined roller body and the surface of the roller neck to ensure that the surface roughness reaches Ra=0.8 or below.

[0282] This step ensures that the surface roughness meets the requirements, satisfying the wear resistance and precision needs in actual use.

[0283] S706, Dimensional Inspection:

[0284] High-precision measuring tools (such as micrometers, calipers, and coordinate measuring machines) are used to inspect the dimensions of the processed electrode rollers to ensure that all dimensions meet the requirements of the drawings, thereby ensuring the dimensional accuracy of the processed electrode rollers and meeting the assembly and functional requirements in actual use.

[0285] S707. Visual Inspection and Repair:

[0286] Perform a visual inspection on the processed electrode rollers to ensure that there are no knife marks, scratches or other surface defects;

[0287] Minor defects that are found are repaired to ensure surface quality.

[0288] This step ensures the appearance quality of the electrode rollers and prevents surface defects from affecting their service life and performance.

[0289] S708. Cleaning and Protection:

[0290] Clean the processed electrode rollers to remove chips and oil stains from the surface;

[0291] Apply rust-preventive oil or take other protective measures to prevent the processed surface from rusting or being damaged.

[0292] This step ensures the surface quality of the electrode rollers during subsequent storage and transportation, preventing surface corrosion caused by environmental factors.

[0293] Compared with the prior art, through the above sub-steps, the present invention ensures that the surface roughness of the outer circle of the roller body and the roller neck reaches Ra=0.8 or below, meeting the wear resistance and precision requirements in actual use; through precision machining and strict testing, it ensures that the dimensional accuracy of the electrode roller meets the design requirements, improving assembly and performance; through visual inspection and finishing, it ensures that the surface of the electrode roller is free of defects, improving the overall quality of the product; through cleaning and protective treatment, it ensures the surface quality of the electrode roller during subsequent storage and transportation, extending its service life.

[0294] Compared with existing technologies, this invention significantly reduces material costs by optimizing chemical composition, employing electroslag remelting, strictly controlling parameters such as melting rate and slag layer thickness, using multi-pass forging with strict control of heating temperature and holding time, controlling surface roughness (Ra≤0.8) and surface strengthening treatment, using induction hardening combined with cryogenic treatment, and employing a low-temperature tempering process at 160-200℃. Simultaneously, it exhibits excellent hardness retention, high wear resistance, and precision under high-temperature conditions, significantly improving the material's microstructure uniformity and performance stability. The final product demonstrates superior performance under high-temperature conditions, meeting the high-performance requirements of the new energy battery industry for electrode rollers.

[0295] The following embodiments and comparative examples are provided to better illustrate the present invention:

[0296] Example 1

[0297] This embodiment discloses an electrode roll forging, with a roll body diameter of... A roll forging with a roll body length of 700mm has a net weight of 3.65 tons;

[0298] The chemical composition by mass percentage is as follows: C: 0.97%, Si: 2.1%, Mn: 0.5%, Cr: 1.85%, Nb: 0.08%, V: 0.08%, Mo: 0.15%, Ni: 0.3%, Cu: 0.1%, N: 220ppm, with the balance being Fe and unavoidable impurities.

[0299] Prepared by the following method:

[0300] S1. Raw material preparation:

[0301] Raw materials are proportioned according to the designed chemical composition, and the chemical composition of molten steel is controlled to meet the target requirements through electric furnace roughing and vacuum refining, including:

[0302] (1) Electric Furnace Preliminary Smelting: Pig iron and steel plates are added according to the final composition as described above, with pig iron accounting for 20% of the total material weight and the remainder being steel plates. The materials are melted and smelted in an electric furnace at an oxidation temperature of approximately 1540℃, a melting time of 40 minutes, and a tapping temperature of 1620℃. Based on the designed chemical composition, suitable raw materials (such as pig iron, scrap steel, alloying elements, etc.) are selected and precisely proportioned to ensure that the chemical composition of the raw materials meets the design requirements, providing an accurate raw material basis for subsequent smelting processes. The proportioned raw materials are added to the electric furnace for melting and smelting, controlling the oxidation temperature and melting time to ensure that the molten steel is fully melted and impurities are initially removed. After vacuum degassing, temperature and composition samples are taken to check whether the chemical composition of the molten steel meets the target requirements. If the composition does not meet the requirements, fine-tuning is performed; once the chemical composition meets the target requirements, the molten steel is tapped into an intermediate ladle or ingot mold.

[0303] (2) Refining process: Preheat the ingot mold to 200℃ to ensure that the ingot mold is dry and the temperature is uniform, to prevent the molten steel from cracking due to excessive temperature difference during the pouring process, and at the same time reduce the cooling rate of the molten steel to ensure the stability of the pouring process.

[0304] Before adding molten steel from the electric arc furnace, 50 kg of aluminum blocks are placed at the bottom of the refining ladle. After the molten steel is added, the slag-forming materials are added in two batches: two-thirds of the slag-forming agent is added first, followed by the remaining slag 15 minutes later. The types and total weight of the slag-forming agents are: 1500 kg of lime; 200 kg of silica; and 450 kg of alumina powder. After slag formation, the deoxidizer used is Al powder, weighing 50 kg. The Al powder is added in two batches, with a 20-minute interval between each batch. When the molten steel temperature reaches 1550℃ or below, alloying is performed. The alloy is adjusted to the target range according to the steel grade composition.

[0305] (3) Vacuum degassing operation: The vacuum degree is required to be no higher than 300Pa and the vacuum degassing time is 35min. After the vacuum degassing operation is completed, the temperature is measured and the composition sample is taken. After the target composition range is reached, argon gas soft blowing is performed. The duration of argon gas soft blowing is 20-30min and the temperature is 1500-1510℃. Steel can be produced.

[0306] S2. Steel ingot preparation:

[0307] The vacuum-refined molten steel is vacuum-cast into electrode rod blanks, which are then used as consumable electrodes for electroslag remelting to obtain steel ingots, including:

[0308] (4) Casting the electrode blank: Preheat the ingot mold to 200℃, then fill the center injection tube and ingot mold with argon gas for 10 minutes. After that, remove the argon gas tube, cover the top of the ingot mold with a lid, and then proceed with casting. Argon gas is used for protection during the entire casting process, and the argon gas protection pressure is 1 kg / cm². 2The casting time is 14 minutes, and the mold is removed after 4 hours.

[0309] (5) Annealing: Annealing temperature 860℃, holding time 25h, furnace cooling to 350℃ before unloading.

[0310] (6) Electroslag Remelting: The electrode rod billet is used as a consumable electrode. The billet diameter is 350 mm and the weight is 3.5 t. During the electroslag remelting process, the melting rate is maintained at 500-550 kg / h, the crystallizer diameter is 600 mm, the slag amount is 260 kg, and the slag system is a quaternary slag system with CaF2:Al2O3:CaO:MgO ratio of 50:30:15:5 and a slag layer thickness of 250 mm. During the electroslag remelting process, aluminum granules are added for deoxidation, and the amount of aluminum granules is equal to the amount of slag. The aluminum granules are added every 5 minutes during the remelting process until the remelting is completed. After the furnace is shut down, the billet is cooled in the crystallizer for 100 minutes before being sent to the forging process. Electroslag remelting is carried out under protective atmosphere conditions. During the remelting process, aluminum granules are added every 10 minutes for deoxidation, and the amount of aluminum granules is equal to the amount of slag. The remelting process continues until the electrode rod billet is completely melted. The molten steel is further purified by electroslag remelting to remove impurities and gases, while the purity of the steel ingot is ensured by deoxidation with aluminum particles.

[0311] After electroslag remelting is completed, the ingot is cooled in the crystallizer for 100-120 minutes after the furnace is shut down. Then, a surface inspection is performed to clean defects such as slag grooves from the ingot surface. This ensures uniform cooling of the ingot and avoids defects such as cracks caused by excessively rapid cooling. Simultaneously, surface defects are cleaned to ensure the surface quality of the ingot.

[0312] Specific parameters:

[0313] Maintain a melting rate of 600 kg / h.

[0314] The amount of slag is 500 kg.

[0315] The slag layer thickness is 300mm.

[0316] S3. Preparation of forging blanks:

[0317] The steel ingot is forged in multiple passes, with the forging ratio controlled at ≥4.0, to obtain the target size electrode roll blank; including:

[0318] (7) Forging: Check the surface quality of the electroslag remelted ingot, clean the slag grooves, oxide scale and other defects on the surface of the steel ingot, ensure that the surface is clean and flat, remove surface defects, and prevent the introduction of impurities or defects in the subsequent forging process, which would affect the quality of the forging.

[0319] Control the heating rate of the steel ingot to ≤70℃ / h, and gradually heat the electroslag ingot obtained in step (6) to 1150℃ in stages, hold it at that temperature for 11h for diffusion homogenization, then upset it to 800mm (upsetting ratio 2.0), and draw it to... (Drawing ratio 2.4). Then reheat to 1150℃, hold for 10 hours, remove from the oven, upset to 800mm (upsetting ratio 2.3), and draw to... (Draw ratio 2.2), heat to 1150℃ and hold for 8 hours. Use a flat anvil on top and a V-shaped anvil on the bottom for finishing to produce the finished product. Forge the small tables at both ends to the required dimensions and correct the eccentricity of the roll body and roll neck. The roll body diameter is 770mm (black skin). Measure the concentricity deviation of the roll body and roll neck and correct the actual deviation of 10mm.

[0320] (8) Controlled cooling after forging: The workpiece obtained in step (7) is hoisted to the air-cooling area. When the workpiece is hoisted to the air-cooling area after forging, the temperature of the roller body is ≥750℃. Forced air cooling is performed using a 10KW high-power axial flow fan, and the temperature is cooled to 470℃ for 2 hours before loading into the furnace.

[0321] S4. Post-forging heat treatment:

[0322] The forged electrode roll blanks are subjected to normalizing, spheroidizing annealing, and hydrogen diffusion annealing to eliminate forging stress, reduce the hydrogen content in the steel, and obtain a spheroidal pearlite microstructure; including:

[0323] (9) Normalizing treatment: After the workpiece obtained in step (8) is placed in the heating furnace and the furnace is assembled, it is heated to 950℃ in sections. After holding the temperature for 15 hours, it is taken out of the furnace and the whole furnace is lifted off the trolley for forced air cooling. Specifically, the workpiece is quickly lifted out of the furnace and placed in the air field for cooling. When the normalizing workpiece is lifted to the air cooling site, the roller body temperature is ≥800℃. A 10KW high-power axial flow fan is used for forced air cooling. Ten fans blow against each other at intervals. If there are multiple pieces in the furnace, the time for lifting the whole furnace is controlled within 40 minutes. The distance between the rollers is ≥0.3m. After the surface temperature is about 350℃, it is put into the furnace for spheroidizing annealing. The overall air cooling time is 4.0 hours.

[0324] (10) Spheroidizing annealing: Place the workpiece obtained in step (9) into an annealing furnace, heat it to 810℃ and hold it for 15 hours, then heat it in two stages: hold it at 710℃ for 45 hours, first cool it to 580℃ with a temperature control of ≤30℃ / h, then raise it to 680℃ and hold it for 120 hours, and finally cool it to 250℃ before taking it out of the furnace.

[0325] (11) Hydrogen diffusion annealing:

[0326] The spheroidized annealed blank is placed in an annealing furnace and heated to 650℃;

[0327] Maintain this temperature for 120 hours to ensure that the hydrogen gas is fully diffused and discharged.

[0328] After annealing, the furnace was cooled to room temperature.

[0329] (12) Rough car, including:

[0330] S001. Pre-processing inspection:

[0331] The heat-treated electrode roll blanks are inspected for appearance and dimensions to ensure there are no cracks, deformations or other obvious defects, in order to confirm the quality of the heat-treated blanks and provide qualified blanks for rough machining.

[0332] S002, Clamping and Positioning:

[0333] Mount the electrode roll blank on a CNC lathe and clamp it with a suitable fixture (such as a three-jaw chuck, center, etc.) to ensure that the clamping is firm and the coaxiality meets the requirements, so as to ensure the stability and machining accuracy of the electrode roll during the processing and avoid machining errors caused by improper clamping.

[0334] S003, Dimensional Measurement and Planning:

[0335] Use measuring tools (such as calipers and micrometers) to measure the key dimensions of the electrode roll blank, and plan the rough machining allowance according to the drawing requirements to ensure that the dimensions and allowance after rough machining meet the requirements of subsequent finish machining, and avoid over-machining or under-machining.

[0336] S004. Rough machining of the outer diameter of the roller body:

[0337] The outer diameter of the roller body is rough-machined using carbide cutting tools;

[0338] Set the cutting parameters (such as cutting speed, feed rate, and depth of cut) according to the process requirements;

[0339] During rough machining, ensure that the machining dimensions meet the drawing requirements and leave sufficient allowance (such as a minimum turning amount of 17mm and a maximum turning amount of 20mm on one side).

[0340] S005, Rough machining of roll neck and related areas:

[0341] Rough machining is performed on the roll neck and related areas to ensure dimensional accuracy and surface quality;

[0342] Using appropriate cutting tools and cutting parameters, the roll neck is turned or ground.

[0343] Check the dimensions and surface quality after processing to ensure they meet design requirements.

[0344] This step ensures the basic shape and dimensions of the roller neck and related areas, improving the overall accuracy of the electrode roller and the convenience of subsequent processing.

[0345] S006. Size Inspection and Adjustment:

[0346] Use high-precision measuring tools (such as micrometers and calipers) to inspect the dimensions of the rough-machined electrode rollers;

[0347] Based on the test results, adjustments or reprocessing are made to any parts that do not meet the requirements;

[0348] This step ensures that the dimensional accuracy after rough machining meets the requirements of subsequent machining, avoiding machining problems caused by dimensional deviations.

[0349] The workpiece obtained in step (11) is rough-machined according to the machining drawings. The center of the roller body is used as the center line of the entire roller during rough machining, and the minimum turning amount on one side of the roller body is 17mm and the maximum is 20mm.

[0350] S5. The conditioning process includes:

[0351] (13) Clean the surface of the electrode roll blank after the forging heat treatment to ensure that there is no oxide scale, oil or other impurities on the surface, and ensure uniform heat transfer during the quenching process to avoid uneven quenching or quenching cracks caused by surface defects; use oil cooling quenching and high temperature tempering to process the electrode roll blank after the forging heat treatment to obtain a uniform and fine tempered sorbite structure and a part of granular carbide metallographic structure.

[0352] The workpiece obtained in step (12) is placed in a quenching furnace and heated in sections to 910°C. After holding at the temperature for 15 hours, it is then oil-quenched for 190 minutes. After quenching, the blank is visually inspected to ensure that there are no quenching cracks or other defects. Problems that may occur during the quenching process are promptly identified and dealt with to ensure the quality of the blank.

[0353] Within 40 minutes of quenching, the material should be promptly placed into the tempering furnace. The furnace should be heated to 610℃, with a heating rate controlled at ≤70℃ / h. Tempering should be carried out for 30 hours, followed by furnace cooling to ≤250℃ before removal from the furnace. This ensures a thorough tempering process, resulting in a uniform tempered sorbite structure. Tempering and holding eliminate quenching stress, stabilize the microstructure, and achieve excellent comprehensive mechanical properties, including high strength and good toughness.

[0354] (14) Semi-finishing: The workpiece obtained in step (13) is semi-finished according to the process drawings. In particular, the outer circle of the electrode roller body needs to be rough ground to ensure that its roughness reaches Ra=0.8 or below, including:

[0355] S011. Pre-processing inspection:

[0356] The appearance and dimensions of the tempered electrode roll blanks are inspected to ensure that there are no cracks, deformations or other obvious defects, so as to confirm the quality of the blanks after tempering and provide qualified blanks for semi-finishing.

[0357] S012, Clamping and Positioning:

[0358] Mount the electrode roll blank on a CNC lathe and clamp it with a suitable fixture (such as a three-jaw chuck, center, etc.) to ensure that the clamping is firm and the coaxiality meets the requirements, so as to ensure the stability and machining accuracy of the electrode roll during the processing and avoid machining errors caused by improper clamping.

[0359] S013, Dimensional Measurement and Planning:

[0360] Use measuring tools (such as calipers and micrometers) to measure the key dimensions of the electrode roll blank, and plan the semi-finishing allowance according to the drawing requirements to ensure that the dimensions and allowance after semi-finishing meet the requirements of subsequent finishing, and avoid over-processing or under-processing.

[0361] S014, Semi-finishing of the outer diameter of the roller body:

[0362] The outer diameter of the roller body is semi-finished using carbide cutting tools;

[0363] Set the cutting parameters (such as cutting speed, feed rate, and depth of cut) according to the process requirements;

[0364] During the semi-finishing process, ensure that the machining dimensions meet the drawing requirements and leave sufficient allowance (such as a minimum single-sided turning amount of 17mm and a maximum of 20mm).

[0365] Ensure that the surface roughness after processing reaches Ra=0.8 or below.

[0366] This step, through semi-finishing, further optimizes the dimensional accuracy and surface roughness of the outer circle of the roller body, providing suitable allowance and surface quality for subsequent finishing.

[0367] S015. Dimensional Inspection and Adjustment:

[0368] Use high-precision measuring tools (such as micrometers and calipers) to inspect the dimensions of the semi-finished electrode rolls;

[0369] Based on the test results, adjustments or reprocessing are made to the parts that do not meet the requirements to ensure that the dimensional accuracy after semi-finishing meets the requirements of subsequent processing and to avoid processing problems caused by dimensional deviations.

[0370] S016, Roughness inspection:

[0371] The surface roughness of the outer cylindrical surface of the machined roller is inspected using a surface roughness tester to ensure that the surface roughness reaches Ra=0.8 or below.

[0372] This step ensures that the surface roughness meets the requirements, satisfying the wear resistance and precision needs in actual use.

[0373] S017. Balance Check:

[0374] Check the allowance of each part of the semi-finished electrode roller to ensure that the allowance is uniform and sufficient, so as to ensure that there is enough allowance for subsequent finishing and avoid processing defects caused by insufficient allowance.

[0375] S018. Cleaning and Protection:

[0376] Clean the semi-finished electrode rollers to remove surface chips and oil.

[0377] Apply rust-preventive oil or take other protective measures to prevent the processed surface from rusting or being damaged, so as to ensure the surface quality of the electrode roller during subsequent storage and transportation and prevent surface corrosion caused by environmental factors.

[0378] S6. Final heat treatment:

[0379] The quenched and tempered electrode roll blanks are processed in the following order: induction heating of electrode rolls, quenching and cooling, and low-temperature tempering.

[0380] Induction heating: After preheating the entire electrode roller, medium frequency or power frequency induction heating is used;

[0381] Quenching and cooling: A staged quenching and cooling process is adopted using an overall spray method, and the cooling rate is controlled to exceed the critical cooling rate of the material to ensure that the hardened layer depth is ≥20mm-25mm;

[0382] Low-temperature tempering: The quenched electrode rolls are placed in a tempering furnace to eliminate quenching stress, stabilize the martensitic structure, and control the hardness grade and uniformity of the roll body.

[0383] Specifically, it includes:

[0384] (15) Induction heat treatment: The workpiece obtained in step (14) is preheated in an electric furnace at 280℃ for 15 hours. It is then induction heated and quenched on a special induction hardening integrated machine tool manufactured using the "one-shot method" principle. In step (14), the target temperature for induction heating is 990℃, the process power is 800KW / 20min+480KW / 20min+300KW / 20min, the frequency is 150Hz, the rotation speed is 5 revolutions / min, and the single-sided gap between the roll and the inductor is 70mm. After heating, the workpiece is quenched as a whole, and the quenching water pressure is 0.4MPa / 20min+0.25MPa / 40min+0.15MPa / 90min.

[0385] (16) Deep cryogenic treatment: The workpiece obtained in step (15) is subjected to deep cryogenic treatment, kept at -96℃ for 3 hours or less, and then placed in the air to defrost and return to room temperature.

[0386] (17) Low temperature tempering: The workpiece obtained in step (16) is placed in a box furnace at 170°C for low temperature tempering. The tempering is held at 75h and then cooled to ≤50°C before being taken out of the furnace.

[0387] (18) Hardness test: The workpiece obtained in step (17) is polished along four mother lines at 90° intervals on the roller body and then tested for hardness.

[0388] (19) Finishing: The workpiece obtained in step (18) is precision turned and ground according to the drawing.

[0389] (20) Flaw detection: The workpiece obtained in step (19) is subjected to flaw detection in accordance with GB13314.

[0390] (21) Inspection, packaging and warehousing: The workpieces obtained in step (20) are inspected for straightness, concentricity and light transmittance, and then packaged and delivered.

[0391] Example 2

[0392] This embodiment discloses an electrode roll forging, which differs from Embodiment 1 in that: the roll body diameter... A roll forging with a roll body length of 950mm has a net weight of 5.18 tons;

[0393] The chemical composition by mass percentage is as follows: C: 0.94%, Si: 1.9%, Mn: 0.5%, Cr: 1.85%, Nb: 0.08%, V: 0.08%, Mo: 0.15%, Ni: 0.3%, Cu: 0.1%, N: 230ppm, with the balance being Fe and unavoidable impurities.

[0394] Prepared by the following method:

[0395] (1) Electric furnace smelting: pig iron and steel plates are added according to the above-mentioned component content in the final composition. Pig iron accounts for 20% of the total material weight, and the remainder is steel plates. The materials are melted and smelted in the electric furnace. The melting and oxidation temperature is about 1540℃, the melting time is 40min, and the tapping temperature is 1620℃.

[0396] (2) The specific process of refining is as follows: Before adding the molten steel from the electric furnace roughing process, 50 kg of aluminum blocks are added to the bottom of the refining ladle; after the molten steel is added, the slag-forming material is added in two batches. The first batch contains two-thirds of the slag-forming agent, and the remaining slag is added after 15 minutes. The types and total weight of the slag-forming agent are: 1500 kg of lime; 200 kg of silica; 450 kg of alumina powder; after the slag is formed, the deoxidizer used is Al powder, with a weight of 50 kg; the Al powder is added in two batches, with an interval of 20 minutes between each batch. When the temperature of the molten steel reaches 1550℃ or below, alloying is performed. The alloy is adjusted to the target range according to the steel composition. Then, vacuum degassing is performed, requiring a vacuum degree not higher than 300 Pa and a vacuum degassing time of 35 minutes; after the vacuum degassing is completed, temperature and composition samples are taken. After reaching the target composition range, argon soft blowing is performed, with a duration of 20-30 minutes and a temperature of 1500-1510℃, at which point the steel can be tapped.

[0397] (3) Vacuum degassing operation: The vacuum degree is required to be no higher than 300Pa and the vacuum degassing time is 35min. After the vacuum degassing operation is completed, the temperature is measured and the composition sample is taken. After the target composition range is reached, argon gas soft blowing is performed. The duration of argon gas soft blowing is 20-30min and the temperature is 1500-1510℃. Steel can be produced.

[0398] (4) Casting electrode blanks: Preheat the ingot mold to 120°C, then fill the ingot mold with argon gas. Each ingot mold is filled with argon gas for 6 minutes. Then remove the argon gas pipe, cover the ingot mold with a lid, and then cast. Argon gas is used to protect the casting process. The argon gas protection flow rate is 20 m3 / h, the casting time is 14 minutes, and the mold is removed after 5 hours.

[0399] (5) Annealing, annealing temperature 860℃, holding time 25h, furnace cooling to 350℃ and then unloading.

[0400] (6) Electroslag remelting: The electrode rod billet is used as a consumable electrode. The electrode billet diameter is 400 mm and the weight is 4.5 t. During the electroslag remelting process, the melting rate is maintained at 530-580 kg / h, the crystallizer diameter is 670 mm, the slag amount is 270 kg, and the slag system is a quaternary slag system with CaF2:Al2O3:CaO:MgO ratio of 50:30:15:5 and a slag layer thickness of about 250 mm. Aluminum granules are added during the electroslag remelting process for deoxidation. The amount of aluminum granules is equal to the amount of slag. The aluminum granules are added every 5 minutes during the remelting process until the remelting is completed. After the furnace is shut down, the material is cooled in the crystallizer for 110 minutes before being sent to the forging process.

[0401] (7) Forging: The electroslag ingot obtained in step (6) is gradually heated to 1150℃ in segments, held for 11 hours for diffusion homogenization, then upset to 1000mm (upsetting ratio 2.1), and drawn to... (Drawing ratio 2.3). Then reheat to 1150℃, hold for 11 hours, remove from the oven, upset to 950mm (upsetting ratio 2.3), and draw to... (Draw ratio 2.2), heat to 1150℃ and hold for 8 hours. Use a flat anvil on top and a V-shaped anvil on the bottom for finishing to produce the finished product. Forge the small tables at both ends to the required dimensions and correct the eccentricity of the roll body and roll neck. The roll body diameter is 820mm (black skin). Measure the concentricity deviation of the roll body and roll neck and correct the actual deviation of 10mm.

[0402] (8) Controlled cooling after forging: The workpiece obtained in step (7) is hoisted to the air-cooling area. When the workpiece is hoisted to the air-cooling area after forging, the temperature of the roller body is ≥745℃. Forced air cooling is performed using a 10KW high-power axial flow fan, and the temperature is cooled to 465℃ for 2 hours before loading into the furnace.

[0403] (9) Normalizing treatment: After the workpiece obtained in step (8) is placed in the heating furnace and the furnace is assembled, it is heated to 950℃ in sections. After holding the temperature for 16 hours, it is taken out of the furnace and the whole furnace is lifted off the trolley for forced air cooling. Specifically, the workpiece is quickly lifted out of the furnace and placed in the air field for cooling. When the normalizing workpiece is lifted to the air cooling site, the roller body temperature is ≥800℃. A 10KW high-power axial flow fan is used for forced air cooling. Ten fans blow against each other at intervals. If there are multiple pieces in the furnace, the time for lifting the whole furnace is controlled within 40 minutes. The distance between the rollers is ≥0.3m. After the surface temperature is about 350℃, it is put into the furnace for spheroidizing annealing. The overall air cooling time is 4.5 hours.

[0404] (10) Spheroidizing annealing: Place the workpiece obtained in step (9) into an annealing furnace, heat it to 810℃ and hold it for 16 hours, then heat it in two stages: hold it at 710℃ for 45 hours, first cool it to 580℃ with a temperature control of ≤30℃ / h, then raise it to 680℃ and hold it for 130 hours, and finally cool it to 250℃ before taking it out of the furnace.

[0405] (11) Hydrogen diffusion annealing:

[0406] The spheroidized annealed blank is placed in an annealing furnace and heated to 680℃;

[0407] Maintain this temperature for 120 hours to ensure that the hydrogen gas is fully diffused and discharged.

[0408] After annealing, the furnace was cooled to room temperature.

[0409] (12) Rough turning: The workpiece obtained in step (11) is rough turned according to the machining drawings. The center of the roller body is used as the center line of the entire roller. The minimum turning amount on one side of the roller body is 17mm and the maximum is 20mm.

[0410] (13) Overall tempering: Place the workpiece obtained in step (12) into a quenching furnace, heat it in sections to 910℃, hold it at that temperature for 16 hours, and then remove it from the furnace for oil quenching for 200 minutes. After quenching, promptly load it into a tempering furnace within 40 minutes. Heat it in the tempering furnace to 610℃, hold it for 32 hours, and then furnace cool it to ≤250℃ before removing it from the furnace.

[0411] (14) Semi-finishing: The workpiece obtained in step (13) is semi-finished according to the process drawings. In particular, the outer circle of the electrode roller body needs to be rough ground to ensure that its roughness reaches Ra=0.8 or below.

[0412] (15) Induction heat treatment: The workpiece obtained in step (14) is preheated in an electric furnace at 280℃ for 16 hours. It is then induction heated and quenched on a special induction hardening integrated machine tool manufactured using the "one-shot method" principle. In step (14), the target temperature for induction heating is 990℃, the process power is 800KW / 25min+480KW / 20min+300KW / 20min, the frequency is 150Hz, the rotation speed is 5 revolutions / min, and the single-sided gap between the roll and the inductor is 70mm. After heating, the workpiece is quenched as a whole, and the quenching water pressure is 0.4MPa / 25min+0.25MPa / 40min+0.15MPa / 90min.

[0413] (16) Deep cryogenic treatment: The workpiece obtained in step (15) is subjected to deep cryogenic treatment, kept at -96℃ for 3 hours or less, and then placed in the air to defrost and return to room temperature.

[0414] (17) Low temperature tempering: The workpiece obtained in step (16) is placed in a box furnace at 170℃ for low temperature tempering. The tempering is held at 80h and then cooled to ≤50℃ before being taken out of the furnace.

[0415] (18) Hardness test: The workpiece obtained in step (17) is polished along four mother lines at 90° intervals on the roller body and then tested for hardness.

[0416] (19) Finishing: The workpiece obtained in step (18) is precision turned and ground according to the drawing.

[0417] (20) Flaw detection: The workpiece obtained in step (19) is subjected to flaw detection in accordance with GB13314.

[0418] (21) Inspection, packaging and warehousing: The workpieces obtained in step (20) are inspected for straightness, concentricity and light transmittance, and then packaged and delivered.

[0419] Example 3

[0420] This embodiment discloses an electrode roll forging, which differs from Embodiment 1 in that: the roll body diameter... A roll forging with a roll body length of 1300mm has a net weight of 9.89 tons;

[0421] The chemical composition by mass percentage is as follows: C: 0.93%, Si: 2.0%, Mn: 0.5%, Cr: 1.86%, Nb: 0.07%, V: 0.08%, Mo: 0.16%, Ni: 0.2%, Cu: 0.1%, N: 235ppm, with the balance being Fe and unavoidable impurities.

[0422] Prepared by the following method:

[0423] (1) Electric furnace primary smelting: pig iron and steel plates are added according to the above-mentioned component content in the final composition. Pig iron accounts for 20% of the total material weight, and the remainder is steel plates. The materials are melted and smelted in the electric furnace. The melting and oxidation temperature is about 1540℃, the melting time is 45min, and the tapping temperature is 1620℃.

[0424] (2) The specific process for refining is as follows: Before adding molten steel from the electric furnace, 60 kg of aluminum blocks are added to the bottom of the refining ladle; after the molten steel is added, the slag-forming material is added in two batches. Two-thirds of the slag-forming agent is added first, followed by the remaining slag after 15 minutes. The types and total weight of the slag-forming agent are: 1600 kg of lime; 220 kg of silica; and 480 kg of alumina powder. After slag formation, the deoxidizer used is Al powder, weighing 50 kg; the Al powder is added in two batches, with a 20-minute interval between each batch. When the molten steel temperature reaches 1550℃ or below, alloying is performed. The alloy is adjusted to the target range according to the steel composition.

[0425] (3) Vacuum degassing operation, the vacuum degree should not exceed 300Pa, and the vacuum degassing time should be 35min. After the vacuum degassing operation is completed, the temperature is measured and the composition sample is taken. After the target composition range is reached, argon gas soft blowing is performed. The duration of argon gas soft blowing is 20-30min and the temperature is 1500-1510℃. Steel can be tapped.

[0426] (4) Casting the electrode blank: Preheat the ingot mold to 120-200℃, then fill the center injection tube and ingot mold with argon gas for 6-10 minutes. After that, remove the argon gas tube, cover the top of the ingot mold with a lid, and then proceed with casting. Argon gas is used for protection during the entire casting process, and the argon gas protection pressure is 0.2-1 kg / cm³. 2 The casting time is 12-14 minutes, and the product is demolded after 3-4 hours.

[0427] (5) Annealing, annealing temperature 860℃, holding time 25h, furnace cooling to 350℃ and then unloading.

[0428] (6) Electroslag remelting: The electrode rod billet is used as a consumable electrode. The electrode billet diameter is 500 mm and the weight is 5 t. During the electroslag remelting process, the melting rate is maintained at 530-580 kg / h, the crystallizer diameter is 700 mm, the slag amount is 300 kg, and the slag system is a quaternary slag system with CaF2:Al2O3:CaO:MgO ratio of 47:33:18:2 and a slag layer thickness of 260 mm. During the electroslag remelting process, aluminum granules are added for deoxidation. The amount of aluminum granules is equal to the amount of slag. The aluminum granules are added every 7 minutes during the remelting process until the remelting is completed. After the furnace is shut down, the material is cooled in the crystallizer for 120 minutes before being sent to the forging process.

[0429] (7) Forging: The electroslag ingot obtained in step (6) is gradually heated to 1150℃ in segments, held for 14 hours for diffusion homogenization, then upset to 1200mm (upsetting ratio 2.1), and drawn to... (Drawing ratio 2.2). Then reheat to 1150℃, hold for 14 hours, remove from the oven, upset to 1200mm (upsetting ratio 2.1), and draw to... (Draw ratio 2.4) Heat to 1150℃ and hold for 9.5h. Use a flat anvil and a V-shaped anvil to finish the product. Forge the small plates at both ends to the required size and correct the eccentricity of the roll body and roll neck. The roll body diameter is 950mm. Measure the concentricity deviation of the roll body and roll neck and correct the actual deviation by 10mm. Controlled cooling after forging. Hoist the workpiece obtained in step (7) to the air-cooling area. When hoisting to the air-cooling area after forging, the roll body temperature is ≥740℃. Use a 10KW high-power axial flow fan for forced air cooling. Cool to 460℃ for 2.5h and load into the furnace.

[0430] (8) Normalizing treatment: After the workpiece obtained in step (8) is placed in the heating furnace and the furnace is assembled, it is heated to 950℃ in stages. After holding the temperature for 18 hours, it is taken out of the furnace and the whole furnace is lifted off the trolley for forced air cooling. Specifically, the workpiece is quickly lifted out of the furnace and placed in the air field for cooling. When the normalizing workpiece is lifted to the air cooling site, the roller body temperature is ≥800℃. A 10KW high-power axial flow fan is used for forced air cooling. Ten fans blow against each other at intervals. If there are multiple pieces in the furnace, the time for lifting the whole furnace is controlled within 40 minutes. The distance between the rollers is ≥0.3m. After the surface temperature is about 350℃, it is put into the furnace for spheroidizing annealing. The overall air cooling time is 5.0h.

[0431] (9) Spheroidizing annealing: Place the workpiece obtained in step (9) into an annealing furnace, heat it to 810℃ and hold it for 18 hours, then heat it in two stages: hold it at 710℃ for 50 hours, first cool it to 580℃ with a temperature control of ≤30℃ / h, then raise it to 670℃ and hold it for 140 hours, and finally cool it in the furnace to 250℃ before taking it out of the furnace.

[0432] (10) Hydrogen diffusion annealing:

[0433] The spheroidized annealed blank is placed in an annealing furnace and heated to 650-680℃;

[0434] Maintain this temperature for 120-150 hours to ensure that hydrogen is fully diffused and discharged.

[0435] After annealing, the furnace was cooled to room temperature.

[0436] (11) Rough turning: The workpiece obtained in step (10) is rough turned according to the machining drawings. The center of the roller body is used as the center line of the entire roller. The minimum turning amount on one side of the roller body is 17mm and the maximum is 20mm.

[0437] (12) Overall tempering: Place the workpiece obtained in step (11) into a quenching furnace, heat it in sections to 910℃, hold it at that temperature for 18 hours, and then oil-quench it for 225 minutes. After quenching, promptly load it into a tempering furnace within 40 minutes. Heat it in the tempering furnace to 610℃, hold it for 36 hours, and then furnace-cool it to ≤250℃ before removing it from the furnace.

[0438] (13) Semi-finishing: The workpiece obtained in step (12) is semi-finished according to the process drawings. In particular, the outer circle of the electrode roller body needs to be rough ground to ensure that its roughness reaches Ra=0.8 or below.

[0439] (14) Induction heat treatment: The workpiece obtained in step (13) is preheated in an electric furnace at 280℃ and held for 18 hours. It is then induction heated and quenched on a special induction hardening integrated machine tool manufactured using the "one-shot method" principle. In step (14), the target temperature for induction heating is 990℃, the process power is 800KW / 30min+480KW / 25min+300KW / 25min, the frequency is 150Hz, the rotation speed is 5 revolutions / min, and the single-sided gap between the roll and the inductor is 70mm. After heating, the entire workpiece is quenched. The quenching water pressure is 0.4MPa / 30min+0.25MPa / 40min+0.15MPa / 100min.

[0440] (15) Deep cryogenic treatment: The workpiece obtained in step (14) is subjected to deep cryogenic treatment, kept at -96℃ for 3.5 hours or less, and then placed in the air to defrost and return to room temperature.

[0441] (16) Low temperature tempering: The workpiece obtained in step (15) is placed in a box furnace at 170℃ for low temperature tempering. The tempering is held at 90h and then cooled to ≤50℃ before being taken out of the furnace.

[0442] (17) Hardness test: The workpiece obtained in step (16) is polished along four mother lines at 90° intervals on the roller body and then tested for hardness.

[0443] (18) Finishing: The workpiece obtained in step (17) is precision turned and ground according to the drawing.

[0444] (19) Flaw detection: The workpiece obtained in step (18) is subjected to flaw detection in accordance with GB13314.

[0445] (20) Inspection, packaging and warehousing: The workpiece obtained in step (19) is inspected for straightness, concentricity and light transmittance, and then packaged and delivered.

[0446] Example 4

[0447] This embodiment discloses an electrode roll forging, which differs from Embodiment 1 in that: the roll body diameter... A roll forging with a roll body length of 1550mm and a net weight of 12.01 tons, including:

[0448] The chemical composition by mass percentage is as follows: C: 0.92%, Si: 1.9%, Mn: 0.6%, Cr: 1.83%, Nb: 0.08%, V: 0.07%, Mo: 0.17%, Ni: 0.2%, Cu: 0.1%, N: 240ppm, with the balance being Fe and unavoidable impurities.

[0449] Prepared by the following method:

[0450] (1) Electric furnace primary smelting: pig iron and steel plates are added according to the above-mentioned component content in the final composition. Pig iron accounts for 20% of the total material weight, and the remainder is steel plates. The materials are melted and smelted in the electric furnace. The melting and oxidation temperature is about 1540℃, the melting time is 50min, and the tapping temperature is 1620℃.

[0451] (2) The specific process for refining is as follows: Before adding molten steel from the electric furnace roughing process, 65 kg of aluminum blocks are added to the bottom of the refining ladle; after the molten steel is added, the slag-forming material is added in two batches. The first batch contains two-thirds of the slag-forming agent, and the remaining slag is added 15 minutes later. The types and total weight of the slag-forming agent are: 1650 kg of lime; 230 kg of silica; and 490 kg of alumina powder. After the slag is formed, the deoxidizer used is Al powder, with a weight of 70 kg; the Al powder is added in two batches, with an interval of 20 minutes between each batch. When the temperature of the molten steel reaches 1550℃ or below, alloying is performed. The alloy is adjusted to the target range according to the steel composition.

[0452] (3) Vacuum degassing operation requires a vacuum degree not higher than 300Pa and a vacuum degassing time of 35min. After the vacuum degassing operation is completed, temperature is measured and composition is sampled. After reaching the target composition range, argon gas soft blowing is performed. The duration of argon gas soft blowing is 20-30min and the temperature is 1510-1520℃. Steel can be tapped.

[0453] (4) Casting electrode blanks: Preheat the ingot mold to 120-200℃, then fill the center injection tube and ingot mold with argon gas for 6-10 minutes, then remove the argon gas tube, cover the top of the ingot mold with a lid and then cast. Argon gas is used to protect the casting process. The argon gas protection pressure is 0.2-1 kg / cm2, the casting time is 12-14 minutes, and the mold is removed after 3.5-4 hours.

[0454] (5) Annealing, annealing temperature 860℃, holding time 25h, furnace cooling to 350℃ and then unloading.

[0455] (6) Electroslag remelting: The electrode rod billet is used as a consumable electrode. The electrode billet diameter is 550 mm and the weight is 6 t. During the electroslag remelting process, the melting rate is maintained at 550-600 kg / h, the crystallizer diameter is 720 mm, the slag amount is 350 kg, and the slag system is a quaternary slag system with CaF2:Al2O3:CaO:MgO ratio of 52:30:15:3 and a slag layer thickness of 260 mm. During the electroslag remelting process, aluminum granules are added for deoxidation. The amount of aluminum granules is equal to the amount of slag. The aluminum granules are added every 8 minutes during the remelting process until the remelting is completed. After the furnace is shut down, the material is cooled in the crystallizer for 150 minutes before being sent to the forging process.

[0456] (7) Forging: The electroslag ingot obtained in step (6) is gradually heated to 1150℃ in segments, held for 19 hours for diffusion homogenization, then upset to 850mm (upsetting ratio 2.1), and drawn to... (Drawing ratio 3.3). Then reheat to 1150℃, hold for 14 hours, remove from the oven, upset to 1250mm (upsetting ratio 2.2), and draw to... (Draw ratio 2.4), heat to 1150℃ and hold for 10 hours. Use a flat anvil on top and a V-shaped anvil on the bottom for finishing to produce the finished product. Forge the small tables at both ends to the required dimensions and correct the eccentricity of the roll body and roll neck. The roll body diameter is 990mm (black skin). Measure the concentricity deviation of the roll body and roll neck and correct the actual deviation by 10mm.

[0457] (8) Controlled cooling after forging: The workpiece obtained in step (7) is hoisted to the air-cooling area. When the workpiece is hoisted to the air-cooling area after forging, the temperature of the roller body is ≥735℃. Forced air cooling is performed using a 10KW high-power axial flow fan, and the temperature is cooled to 455℃ for 2.5 hours before loading into the furnace.

[0458] (9) Normalizing treatment: After the workpiece obtained in step (8) is placed in the heating furnace and the furnace is assembled, it is heated to 950℃ in stages. After holding the temperature for 19 hours, it is taken out of the furnace and the whole furnace is lifted off the trolley for forced air cooling. Specifically, the workpiece is quickly lifted out of the furnace and placed in the air field for cooling. When the normalizing workpiece is lifted to the air cooling site, the roller body temperature is ≥800℃. A 10KW high-power axial flow fan is used for forced air cooling. Ten fans blow against each other at intervals. If there are multiple pieces in the furnace, the time for lifting the whole furnace is controlled within 40 minutes. The distance between the rollers is ≥0.3m. After the surface temperature is about 350℃, it is put into the furnace for spheroidizing annealing. The overall air cooling time is 5.5 hours.

[0459] (10) Spheroidizing annealing: Place the workpiece obtained in step (9) into an annealing furnace, heat it to 810℃ and hold it for 19 hours, then heat it in two stages: hold it at 710℃ for 55 hours, first cool it to 580℃ with a temperature control of ≤30℃ / h, then raise it to 670℃ and hold it for 150 hours, and finally cool it in the furnace to 250℃ before taking it out of the furnace.

[0460] (11) Hydrogen diffusion annealing:

[0461] The spheroidized annealed blank is placed in an annealing furnace and heated to 650℃;

[0462] Maintain this temperature for 120 hours to ensure that the hydrogen gas is fully diffused and discharged.

[0463] After annealing, the furnace was cooled to room temperature.

[0464] (12) Rough turning: The workpiece obtained in step (11) is rough turned according to the machining drawings. The center of the roller body is used as the center line of the entire roller. The minimum turning amount on one side of the roller body is 17mm and the maximum is 20mm.

[0465] (13) Overall tempering: Place the workpiece obtained in step (12) into a quenching furnace, heat it in sections to 910℃, hold it at that temperature for 19 hours, and then oil-quench it for 240 minutes. After quenching, promptly load it into a tempering furnace within 40 minutes. Heat it in the tempering furnace to 610℃, hold it for 38 hours, and then furnace-cool it to ≤250℃ before removing it from the furnace.

[0466] (14) Semi-finishing: The workpiece obtained in step (13) is semi-finished according to the process drawings. In particular, the outer circle of the electrode roller body needs to be rough ground to ensure that its roughness reaches Ra=0.8 or below.

[0467] (15) Induction heat treatment: The workpiece obtained in step (14) is preheated in an electric furnace at 280℃ for 19 hours. It is then induction heated and quenched on a special induction hardening integrated machine tool manufactured using the "one-shot method" principle. In step (15), the target temperature for induction heating is 990℃, the process power is 800KW / 35min+480KW / 30min+300KW / 30min, the frequency is 150Hz, the rotation speed is 5 revolutions / min, and the single-sided gap between the roll and the inductor is 70mm. After heating, the workpiece is quenched as a whole, and the quenching water pressure is 0.4MPa / 35min+0.25MPa / 45min+0.15MPa / 110min.

[0468] (16) Deep cryogenic treatment: The workpiece obtained in step (15) is subjected to deep cryogenic treatment, kept at -96℃ for 4 hours or less, and then placed in the air to defrost and return to room temperature.

[0469] (17) Low temperature tempering: The workpiece obtained in step (16) is placed in a box furnace at 170°C for low temperature tempering. The tempering is held at 96h and then cooled to ≤50°C before being taken out of the furnace.

[0470] (18) Hardness test: The workpiece obtained in step (17) is polished along four mother lines at 90° intervals on the roller body and then tested for hardness.

[0471] (19) Finishing: The workpiece obtained in step (18) is precision turned and ground according to the drawing.

[0472] (20) Flaw detection: The workpiece obtained in step (19) is subjected to flaw detection in accordance with GB13314.

[0473] (21) Inspection, packaging and warehousing: The workpieces obtained in step (20) are inspected for straightness, concentricity and light transmittance, and then packaged and delivered.

[0474] The test results of each embodiment are shown in Table 1 and Table 2. Table 1 shows the high magnification test results of the electrode roller. Each embodiment has an average of 4 busbars on the electrode roller, and 7 hardness points are taken on an average of 7 busbars as shown in Table 2. Table 2 shows the hardness value (HRC) of the electrode roller and the test results of the hardened layer.

[0475] Table 1 High-magnification inspection results of electrode rollers

[0476]

[0477] In Table 1, category A represents sulfide inclusions, category B represents alumina inclusions, category C represents silicate inclusions, and category D represents spherical oxide inclusions. These are all common concepts in the field. Non-metallic inclusions are evaluated according to the rating chart in GB / T 10561 (using method A to test non-metallic inclusions). Among them, carbide banding and liquid precipitation are evaluated according to GB / T 18254-2016, and carbide network and spheroidized structures are evaluated according to the third level chart in GB / T 1299-2014. As can be seen from Table 1, the inclusion, network carbide, banded carbide, and liquid precipitation indicators of the embodiments of the present invention all meet the high standards.

[0478] Table 2. Finished product inspection data for Roller 1 in Example 2

[0479]

[0480] The hardness values ​​in Table 2 were evaluated according to GB / T 13313-2008, and the hardened layer depth was evaluated with reference to GB / T 13314-2008. Table 2 shows that the hardness values ​​of all embodiments after tempering at 170℃ for 75 hours reached 66 HRC or below, which also provides sufficient assurance for controlling the hardness without decay when the invented roller is used under high-temperature conditions such as 140-160℃; the generatrix in Table 2 is the positioning line on the roller surface parallel to the axis.

[0481] Comparative Example 1

[0482] The difference from Example 1 is that the components used, by mass percentage, are: C 0.90%, Si 0.39%, Mn 0.30%, Cr 3.09%, Mo 0.24%, V 0.10%, P 0.0060%, S 0.0003%, Ni 0.06%, Cu 0.04%, with the balance being Fe and unavoidable impurities. No Nb or N elements were added.

[0483] When manufacturing forgings of the same specifications as in Example 1, the remaining steps are the same as in Example 1. The final obtainable hardness (HRC) of the electrode roll surface is shown in Table 3 below. In particular, when tested at 150°C, the hardness of the roll surface will decrease at different rates, with an overall decrease of at least 5% and an individual point decrease of more than 8%. In particular, the uniformity of the roll surface hardness is also deviated, which is reflected in the electrode quality as the key problem of poor electrode thickness consistency (the ratio of the maximum deviation value to the average hardness of each point, with the maximum deviation rate being greater than 8.8%).

[0484] Table 3. Hardness measurements of the surface of the finished product prepared in Comparative Example 1 at room temperature.

[0485]

[0486] Comparative Example 2

[0487] The difference from Example 1 lies in the final heat treatment, which employs dual-frequency induction heating for surface quenching. Specifically, the workpiece meeting the processing requirements is preheated in a 350℃ electric furnace for 15 hours, followed by surface quenching using a 50Hz & 250Hz dual-frequency induction hardening machine. The 50Hz induction heating temperature is 900℃ with a power of 800KW, and the 250Hz induction heating temperature is 900℃ with a power of 400KW. The workpiece descent speed is 0.7mm / s, the rotation speed is 20r / min, the quenching water pressure is 0.4MPa, the single-sided gap between the roll and the inductor is 20mm, and the cooling time is 210min. After deep cryogenic treatment at -70℃ for 5 hours, the workpiece is placed in air to defrost and warm to room temperature. Finally, it is tempered at 125℃ for 150 hours and cooled to ≤50℃ before being removed from the furnace. The alloy composition and other steps are the same as in Example 1.

[0488] The final obtainable roller surface hardness (HRC) is shown in Table 4 below. Especially when tested at 150℃, the roller surface hardness will decrease at different rates, with an overall decrease of at least 5% and an individual point decrease of more than 8%. In particular, the uniformity of roller surface hardness is also deviated, which is reflected in the key problem of poor thickness consistency of the electrode.

[0489] Table 4. Hardness measurements of the finished product surface of the preparation roller in Comparative Example 2 at room temperature.

[0490]

[0491] The results show:

[0492] As can be seen from Examples 1-4, the hardness decay is controlled within 2%-3% under high temperature conditions of 140-160℃, or even not decayed, which significantly improves the high temperature stability and service life of the electrode roller compared with Comparative Examples 1-2; the maximum deviation rate of the hardness measurement value of the finished roller surface at room temperature is ≤3%, which is far better than Comparative Examples 1-2 (>8.8%).

[0493] contrast Figure 1 (Microscopic metallographic image of the finished product from Example 1) and Figure 2 (Microscopic metallographic image of the finished product of Comparative Example 1) It can be seen that the sulfide inclusions, alumina inclusions, silicate inclusions, and spherical oxide inclusions in the finished product of Example 1 are significantly less than those in Comparative Example 1, and the grain size is higher (≥8).

[0494] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A type of electrode roll forging, characterized in that, The chemical composition, expressed as a percentage by mass, is as follows: C: 0.75-1.05; Si: 1.0-2.5; Mn: 0.3-1.0; P: ≤0.015; S：≤0.010； Cr：1.0-2.0； Nb: 0.01-0.1; V: 0.05-0.25; Mo: ≤0.2; Ni+Cu: ≤0.6; N: ≥200ppm, balance being Fe and unavoidable impurities.

2. The electrode roll forging according to claim 1, characterized in that, In the chemical composition of the electrode roll forging, the nitrogen content is controlled at 200ppm-300ppm.

3. The electrode roll forging according to claim 2, characterized in that, The surface hardness of the electrode roll forging is ≥66HRC.

4. The electrode roll forging according to claim 2, characterized in that, The surface hardness of the electrode roll forging is ≥68HRC.

5. The electrode roll forging according to claim 1, characterized in that, The surface hardness uniformity of the electrode roll forging is within ±0.3 HRC.

6. The electrode roll forging according to claim 1, characterized in that, The surface roughness Ra value of the electrode roll forging is ≤0.

8.

7. The electrode roll forging according to claim 1, characterized in that, The total Nb and V content in the chemical composition of the electrode roll forging is controlled between 0.08% and 0.1%.

8. The electrode roll forging according to claim 1, characterized in that, The grain size of the electrode roll forging is ≥8.

9. The electrode roll forging according to claim 1, characterized in that, The surface hardness of the electrode roll forging is ≤2% under high temperature conditions of 140-160℃.

10. A method for preparing an electrode roll forging, characterized in that, For preparing the electrode roll forging according to any one of claims 1-9, comprising: By reducing the Cr and Mo content in the electrode roll forgings, increasing the Si content, and adding Nb, V, and N, the material's ability to retain high-temperature hardness is improved, high-temperature hardness decay is reduced, and costs are lowered. By sequentially processing electrode rollers through induction heating, quenching and cooling, and low-temperature tempering, the hardness decay under high-temperature conditions of 140-160℃ is reduced.

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