Production process for reducing cost and improving quality of graphite electrode joint

Abstract

The invention relates to a graphite electrode joint production process capable of reducing cost and improving quality, and relates to the field of graphite electrode manufacturing, the graphite electrode joint production process comprises the following steps: roasting a pressed blank to form a whole roasted blank, carrying out first mechanical processing on the roasted blank, cutting the whole blank into single blank sections with the length of 0-20mm, and carrying out second mechanical processing on the roasted blank; meanwhile, turning or grinding the shape of the blank section until the shape of the blank section is the same as the geometric contour of a finished product joint, and reserving 0-20mm machining allowance in the radial direction, so that the weight of the blank section is reduced by 15-40%; then the pre-machined blank section is sequentially subjected to vacuum pressurization impregnation, gradient temperature control secondary roasting and high-temperature graphitization treatment, in the process, redundant materials are pre-cut off, so that the infiltration consumption and thermotechnical energy consumption of an impregnant are remarkably reduced, and the reserved allowance space actively adapts to graphitization thermal expansion deformation; and finally, secondary finish machining is carried out on the graphitized blank, all the allowance is cut off with the tolerance precision smaller than or equal to 0.1 mm, and essential bridging of a material pore structure and cliff type reduction of the microcrack occurrence rate are synchronously achieved, so that the high-volume-density and high-yield electrode connector is obtained.

Description

Technical Field

[0001] This invention relates to the field of graphite electrode manufacturing technology, specifically to a production process for graphite electrode connectors that reduces costs and improves quality. Background Technology

[0002] Currently, the graphite electrode connector industry generally adopts a continuous production process using a single blank: after the pressed blank is fired as a whole, it is directly impregnated, fired multiple times, and graphitized, and finally cut into individual connectors. This method has two major drawbacks:

[0003] High costs: Due to the existence of 30-40% redundant blanks, the consumption of asphalt in the impregnation process increases, the consumption of natural gas in the calcination process increases, the electricity consumption in the graphitization process increases, and the consumption of auxiliary materials in each process increases. As a result, the production cost of each process is high, making the unit cost of the joint twice that of the electrode body.

[0004] Bottleneck in quality improvement: Due to the existence of 30-40% redundant billets, and the fact that these redundant billets are located on the outside of the billet, most of the asphalt cokes on the surface during the impregnation process, and less asphalt and coke enters the core. When the finished joint is machined, the billet with high surface bulk density is removed, while the remaining core material has low bulk density. Traditional processes rely on simply increasing the number of impregnations to improve material density. However, the pore closure rate encounters a physical limit and cannot penetrate the core. The penetration rate is lower closer to the center, and the increase in bulk density cannot meet the requirements.

[0005] This solution, through disruptive process restructuring, incorporates a pre-processing step after baking to remove redundant blanks, thereby reducing costs and improving quality. It simultaneously breaks through production cost barriers and achieves a leap in material performance, fundamentally solving the industry's technological dilemma. Summary of the Invention

[0006] In order to solve the problems of the prior art, the present invention provides a production process for graphite electrode connectors that reduces costs and improves quality.

[0007] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution, including the following steps:

[0008] S1: The electrode connector blank is baked to obtain a baked blank;

[0009] S2: Transform the production of whole blanks into customized processing of individual joints;

[0010] S3: Perform the first mechanical processing, i.e., pre-processing, on the calcined blank, which includes:

[0011] The entire roasted blank is cut into individual joint blank segments, the length of which is 0-20mm longer than the finished joint;

[0012] The blank section is machined to the same geometric contour as the finished joint, and a machining allowance of 0-20mm is retained in the radial direction. The allowance is used to accommodate the thermal expansion deformation and finishing of subsequent processes.

[0013] S4: Pre-processing can be carried out in processes such as roasting, impregnation, second roasting, second impregnation, and third roasting to remove redundant blanks. However, pre-processing after the first roasting is the most effective way to remove redundant blanks, resulting in the greatest cost reduction and the best quality improvement.

[0014] S5: Pre-processing to remove redundant blanks in any process after the baking process and before graphitization is a secret technology protected by this patent.

[0015] S6: The processed blanks are sequentially impregnated, fired a second time (impregnated a second time, fired a third time), and graphitized to form a graphitized joint blank.

[0016] S7: Perform a second machining process on the graphitized connector blank to remove all excess material and control the dimensional tolerance to ≤0.1mm to obtain the finished electrode connector.

[0017] The core technology of this patent, and the key focus of patent protection, lies in transforming the production of the entire blank into customized processing of individual joints. While pre-processing to remove redundant blanks can be implemented in processes such as baking, impregnation, second baking, second impregnation, and third baking, pre-processing after the first baking stage yields the best results, with the greatest cost reduction and the best quality improvement. The core requirement of this patent is that any pre-processing to remove redundant blanks after the first baking stage and before graphitization constitutes a unique technological advantage protected by this patent.

[0018] This process directly solves two long-standing problems in the electrode connector industry by precisely controlling two machining processes (the first with a 0-20mm allowance and the final finishing) and coordinating the impregnation-second firing-graphitization process:

[0019] High cost problem: The first machining removes 15-40% of the redundant weight of the baked blank, which significantly reduces the consumption of impregnating agent, natural gas, and graphitization electricity, thus reducing the unit production cost.

[0020] Quality bottleneck: After pre-processing, redundant blanks are removed, increasing the specific surface area of ​​the blanks and improving the coal tar pitch impregnation permeability by over 20%. The impregnating pitch can directly penetrate the core of the blank, increasing coking and significantly improving bulk density. This reduces pitch consumption and improves impregnation quality, resulting in a 0.04-0.08 g / cm³ increase in joint bulk density. 3 .

[0021] In one specific implementation, during the first machining process, the weight of the pre-processed blank removed accounts for 15%-40% of the total weight of the baked blank.

[0022] In one specific implementation, the machining allowance in step S2 is achieved through turning or grinding processes.

[0023] In one specific implementation, the second machining process uses a precision machining process to control the joint size tolerance to ≤0.1mm.

[0024] In one specific implementation, the reduced billet weight from the first machining process leads to a 20%-40% reduction in impregnating agent consumption, a 18%-25% reduction in natural gas consumption during the second calcination, and a 15%-30% reduction in electricity consumption during the graphitization process.

[0025] In one specific embodiment, the impregnation process uses a coal tar pitch impregnating agent, the amount of which adheres to the surface of the billet segment ≤0.8 g / cm². 2 .

[0026] The beneficial effects of this invention are as follows:

[0027] 1. By breaking down the continuous production of the entire blank into customized processing of individual joints, and innovatively adding a pre-processing step after baking, redundant blanks are precisely removed, fundamentally reducing the amount of raw materials processed in high-energy-consuming processes (impregnation, graphitization), significantly reducing the consumption of expensive impregnating agents and the duration of high-temperature treatment, the electrode joint is transformed from a "cost amplifier" into a "profit-added component".

[0028] 2. The regularized surface of the pre-processed blank breaks down the internal stress barrier caused by traditional whole-material processing, allowing the impregnating agent to penetrate deeply along the geometrically optimized path; combined with the uniform heating characteristics of the segmented blank in the secondary firing, the carbon atom arrangement order is reconstructed at the molecular level, realizing the essential closure of the material's pore structure and obtaining a graphite joint with a stable high-density core.

[0029] 3. The pioneering "pre-shaping-final finishing" two-stage processing strategy actively adapts to the thermal expansion deformation of the graphitization process by reserving a dynamic allowance space (0-20mm) in the first processing, eliminating the proliferation of microcracks caused by thermal stress concentration in traditional processes; at the same time, it avoids the risk of local defect diffusion in the entire billet, transforming qualified joints from "probabilistic products" into "deterministic outputs". Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the overall process flow of the present invention. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] A production process for a connector used in graphite electrodes with a diameter of Φ450mm that reduces costs and improves quality.

[0033] Step 1: Preparation of the molding preform

[0034] Petroleum coke green billets (ash content ≤0.3%) with a diameter of Φ252mm and a length of 1560mm were molded under a pressure of 160MPa for 120 seconds to obtain a density of 1.65g / cm³. 3 The pressed blank.

[0035] Step 2: Roasting

[0036] The molded preform is placed in a ring-type baking furnace and processed according to the following temperature control curve:

[0037] 0-200℃: Heating rate 15℃ / h (excluding moisture);

[0038] 200-800℃: Heating rate 10℃ / h (volatile matter decomposition);

[0039] 800-1200℃: Heating rate 5℃ / h (coking stage);

[0040] Hold at 1200℃ for 48 hours (to form a baked blank);

[0041] After naturally cooling to 80℃, the product is removed from the furnace and has a bulk density ≥1.60 g / cm³. 3 The baked blanks.

[0042] Step 3: First machining

[0043] Cutting and segmenting: Use a diamond circular saw to cut the entire baked blank into blank segments with a length of 263mm (the finished joint is designed to be 250mm long, with an axial allowance of 13mm, accounting for 5.2% of the finished length; if the joint is small, the allowance needs to be increased to 10%-20% proportionally).

[0044] Rough machining of the outer surface: Performed on a CNC lathe:

[0045] Specifically: rotational speed: 250 rpm, feed rate: 0.2 mm / r, depth of cut: 5 mm on one side;

[0046] Outer diameter: 7.5mm allowance per side, accounting for 3.3% of the diameter;

[0047] Weight control after removal: The weight of a single segment after processing was reduced from 30kg to 23kg.

[0048] Step 4: Soaking

[0049] Load the processed blanks into the impregnation tank and proceed in sequence:

[0050] 1. Vacuuming: Maintain -0.098MPa for 60 minutes;

[0051] 2. Inject coal tar pitch (softening point 85℃): Pressurize to 1.2MPa and maintain for 70 minutes;

[0052] 3. After depressurization, let it drain for 30 minutes;

[0053] The impregnation weight gain rate is controlled at 18-22% (compared to 25-30% in traditional processes), which corresponds to a 26.7% reduction in impregnation agent consumption.

[0054] Step 5: Second roasting

[0055] Gradient heating is carried out in a tunnel kiln:

[0056] 0-300℃: 10℃ / h (focus on controlling the 280-320℃ range for 8 hours to eliminate stress cracks);

[0057] 300-800℃: 15℃ / h;

[0058] Keep warm at 800℃ for 24 hours;

[0059] Achieve a bulk density ≥1.72 g / cm³ 3 The second-fired blank.

[0060] Step 6: Graphitization

[0061] Using an Atchison furnace with petroleum coke as packing, the following is executed:

[0062] Power on and heat up to 2800℃ (rate 150℃ / h);

[0063] 2800℃ constant temperature for 18 hours;

[0064] After natural cooling for ≥120 hours, the product is ready to be removed from the oven.

[0065] The resistivity of the graphitized preform is ≤8.0μΩ·m.

[0066] Step 7: Second machining

[0067] Precision machining using a five-axis CNC machine tool:

[0068] Specifically: rotational speed: 300 rpm, feed rate: 0.05 mm / r, cutting tool: diamond-coated insert;

[0069] The end face is machined to a length of 250mm ± 0.1mm;

[0070] Surface roughness Ra≤3.2μm.

[0071] Step 8: Quality Inspection

[0072] Bulk density determination: ≥1.78 g / cm³ (Archimedes method) 3 ;

[0073] Yield calculation: After continuous production of 500 pieces, the yield rate reaches 85% after removing out-of-tolerance / cracked products.

[0074] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A manufacturing process for graphite electrode connectors that reduces costs and improves quality, characterized in that, Includes the following steps: S1: The electrode connector molding blank is baked to obtain a baked blank; S2: Transform the production of whole blanks into customized processing of individual joints; S3: Perform the first mechanical processing, i.e., pre-processing, on the calcined blank, which includes: The entire roasted blank is cut into individual joint blank segments, the length of which is 0-20mm longer than the finished joint; The blank section is machined to the same geometric contour as the finished joint, and a machining allowance of 0-20mm is retained in the radial direction. The allowance is used to accommodate the thermal expansion deformation and finishing of subsequent processes. S4: Pre-processing can be carried out in processes such as roasting, impregnation, second roasting, second impregnation, and third roasting to remove redundant blanks. However, pre-processing after the first roasting is the most effective way to remove redundant blanks, resulting in the greatest cost reduction and the best quality improvement. S5: Pre-processing to remove redundant blanks in any process after the baking process and before graphitization is a secret technology protected by this patent. S6: The processed blanks are sequentially impregnated, fired a second time (impregnated a second time, fired a third time), and graphitized to form a graphitized joint blank. S7: Perform a second machining process on the graphitized connector blank to remove all excess material and control the dimensional tolerance to ≤0.1mm to obtain the finished electrode connector.

2. The production process for reducing costs and improving quality of graphite electrode connectors according to claim 1, characterized in that: In the first machining process, the weight of the blank removed accounts for 15%-40% of the total weight of the baked blank.

3. The production process for reducing costs and improving quality of graphite electrode connectors according to claim 1, characterized in that: The machining allowance in step S2 is achieved through turning or grinding processes.

4. The production process for reducing costs and improving quality of graphite electrode connectors according to claim 1, characterized in that: The second machining process uses a precision machining process to control the joint size tolerance to ≤0.1mm.

5. The production process for reducing costs and improving quality of graphite electrode connectors according to claim 1, characterized in that: The electrode connector produced by the process has a volume density ≥ 1.78g / cm 3 。 6. The production process for reducing costs and improving quality of graphite electrode connectors according to claim 1, characterized in that: The reduction in billet weight due to the first machining process reduces impregnating agent consumption by 20%-40%, natural gas consumption during the second calcination by 18%-25%, and electricity consumption during the graphitization process by 15%-30%.

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