Graphite electrode for steelmaking and preparation method thereof

Abstract

The invention discloses a graphite electrode for steelmaking and a preparation method thereof. The prepared graphite electrode for steelmaking is high in mechanical strength, low in resistivity and excellent in performance. The needle coke modified asphalt is prepared from the following raw material components in parts by weight: 100-200 parts of needle coke, 50-100 parts of modified asphalt and 2-8 parts of an additive. The pentaerythritol stearate and the phthalate are added into the preparation raw materials, so that the breaking strength of the material is improved, the boric acid and the sodium dihydrogen phosphate are added, the resistivity of the material is reduced, and the boric acid and the sodium dihydrogen phosphate have synergistic interaction.

Description

Technical Field

[0001] The invention belongs to the technical field of steelmaking, and in particular relates to a graphite electrode for steelmaking and a preparation method thereof. Background Art

[0002] Graphite electrodes for steelmaking are an indispensable key material in the electric arc furnace steelmaking process. Graphite electrodes are used as conductive materials in electric arc furnaces to generate high-temperature arcs through the interaction between current and gas, providing the necessary heat source for the steelmaking process. Graphite electrodes for steelmaking can be divided into three types according to their power levels: ordinary power, high power and ultra-high power, which are suitable for electric arc furnaces of different powers and capacities. Ultra-high power graphite electrodes have the characteristics of low resistivity, high mechanical strength, and good oxidation resistance, which can significantly improve steelmaking efficiency and reduce energy consumption.

[0003] The large-diameter, ultra-high power graphite electrodes used in large-capacity, ultra-high power electric furnaces carry a greatly increased current density during the steelmaking process, and the operating conditions are extremely harsh. Therefore, the physical and chemical properties of ultra-high power graphite electrodes must be greatly improved, such as reducing resistivity, increasing volume density and mechanical strength, reducing thermal expansion coefficient and improving thermal shock resistance. Summary of the invention

[0004] The object of the present invention is to provide a graphite electrode for steelmaking and a preparation method thereof.

[0005] A graphite electrode for steelmaking is prepared from the following raw material components in parts by weight: 100-200 parts of needle coke, 50-100 parts of quenched and tempered asphalt, and 2-8 parts of additives.

[0006] The needle coke is one or more of Xingya S-JA grade petroleum needle coke, Mizushima X grade needle coke, and New World HSP grade needle coke.

[0007] The modified asphalt has a quinoline insoluble matter content of 4-8wt%, a toluene insoluble matter content of 20-30wt%, a beta resin content of 18-22wt%, a softening point of 90-100°C, and a coking value of ≥55%.

[0008] The additive is a mixture of pentaerythritol stearate and phthalate in a mass ratio of 1:1.

[0009] The additive is prepared by mixing boric acid, sodium dihydrogen phosphate and water in a mass ratio of 1:1:5.

[0010] The method for preparing the graphite electrode for steelmaking is carried out according to the following steps:

[0011] (1) The needle coke is crushed, screened, and ground into graded materials of different particle sizes, each graded material is mixed evenly, heated to 150-170° C., and then poured into a kneading pot, dry mixed for 6-10 minutes, and then the tempered asphalt is added and wet mixed for 20-30 minutes, and then the additive is added and wet mixed for 5-8 minutes to make a paste;

[0012] (2) pressing the paste prepared in step (1) into a green embryo;

[0013] (3) The green embryo prepared in step (2) is placed in a calcining furnace for calcination, and after calcination, is placed in a graphitization furnace for graphitization, with an initial power of 800-1200 kVA, a rising power of 100-300 k VA / h, and a maximum temperature of the graphitization furnace of 2600-3000°C.

[0014] The particle size composition of the graded materials of different particle sizes in step (1) is: 5-7mm 15-25wt%, 1-3mm 20-35wt%, and the rest is less than 0.25mm.

[0015] The process parameters of the compression molding are as follows: using a 2500-ton press to evacuate and pre-press, the vacuum degree is below -0.08, the pre-pressing pressure is 20-30 MPa, and the extrusion molding is performed after the pre-pressing for 6-8 minutes.

[0016] The calcination process is: heating to 150-250°C at a speed of 25°C / h, then heating to 450-550°C at a speed of 10°C / h, then heating to 750-850°C at a speed of 20°C / h, and finally keeping the temperature for 2-4h.

[0017] Beneficial effects of the present invention: The graphite electrode for steelmaking prepared by the present invention has high mechanical strength, low resistivity and excellent performance. Pentaerythritol stearate and phthalate are added to the raw materials to improve the flexural strength of the material, and boric acid and sodium dihydrogen phosphate are added to reduce the resistivity of the material, and all of them have synergistic effects. DETAILED DESCRIPTION

[0018] In order to facilitate the understanding of the present invention, the present invention will be described more fully below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0019] Example 1

[0020] A graphite electrode for steelmaking is made of the following raw material components in parts by weight: 150 parts of Mizushima X-grade needle coke, 80 parts of modified asphalt, and 6 parts of additives; the modified asphalt has a quinoline insoluble content of 6wt%, a toluene insoluble content of 25wt%, a β-resin content of 20wt%, a softening point of 95°C, and a coking value of 60%; the additive is a mixture of pentaerythritol stearate and phthalate in a mass ratio of 1:1.

[0021] The method for preparing the graphite electrode for steelmaking is carried out according to the following steps:

[0022] (1) crushing, screening and grinding needle coke into graded materials of different particle sizes, mixing the graded materials uniformly, heating to 160° C., and then pouring them into a kneading pot, dry mixing for 8 minutes, adding tempered asphalt and wet mixing for 25 minutes, and then adding additives and continuing wet mixing for 6 minutes to prepare a paste; the particle size composition of the graded materials of different particle sizes is: 5-7 mm 20wt%, 1-3 mm 30wt%, and the rest is less than 0.25 mm;

[0023] (2) pressing the paste prepared in step (1) to form a green embryo; the process parameters of the pressing and molding are as follows: using a 2500-ton press to evacuate and pre-press, the vacuum degree is -0.1, the pre-pressing pressure is 25 MPa, and the pre-pressing is performed for 7 minutes before extrusion molding;

[0024] (3) placing the green embryo prepared in step (2) into a roasting furnace for roasting, and then placing it into a graphitization furnace for graphitization after roasting, with an initial power of 1000 kVA, a rising power of 200 kVA / h, and a maximum temperature of the graphitization furnace of 2800°C; the roasting process is as follows: heating to 200°C at a rate of 25°C / h, then heating to 500°C at a rate of 10°C / h, then heating to 800°C at a rate of 20°C / h, and finally keeping warm for 3 hours.

[0025] Example 2

[0026] A graphite electrode for steelmaking is made from the following raw material components in parts by weight: 100 parts of Xingya S-JA grade petroleum needle coke, 50 parts of modified asphalt, and 3 parts of additives; the modified asphalt has a quinoline insoluble content of 4wt%, a toluene insoluble content of 20wt%, a β-resin content of 18wt%, a softening point of 90°C, and a coking value of 58%; the additive is a mixture of pentaerythritol stearate and phthalate in a mass ratio of 1:1.

[0027] The method for preparing the graphite electrode for steelmaking is carried out according to the following steps:

[0028] (1) crushing, screening and grinding needle coke into graded materials of different particle sizes, mixing the graded materials uniformly, heating to 150° C., and then pouring them into a kneading pot, dry mixing for 6 minutes, adding tempered asphalt and wet mixing for 20 minutes, and then adding additives and continuing wet mixing for 5 minutes to prepare a paste; the particle size composition of the graded materials of different particle sizes is: 5-7 mm 15wt%, 1-3 mm 20wt%, and the rest less than 0.25 mm;

[0029] (2) pressing the paste prepared in step (1) to form a green embryo; the process parameters of the pressing and molding are as follows: using a 2500-ton press to evacuate and pre-press, the vacuum degree is -0.08, the pre-pressing pressure is 20 MPa, and the pre-pressing is performed for 6 minutes before extrusion molding;

[0030] (3) The green embryo prepared in step (2) is placed in a roasting furnace for roasting, and after roasting, is placed in a graphitization furnace for graphitization, with an initial power of 800 kVA, a rising power of 100 kVA / h, and a maximum temperature of the graphitization furnace of 2600°C; the roasting process is as follows: the temperature is increased to 150°C at a rate of 25°C / h, then increased to 450°C at a rate of 10°C / h, then increased to 750°C at a rate of 20°C / h, and finally kept warm for 2 hours.

[0031] Example 3

[0032] A graphite electrode for steelmaking is prepared from the following raw material components in parts by weight: 200 parts of New World HSP-grade needle coke, 100 parts of modified asphalt, and 8 parts of additives; the modified asphalt has a quinoline insoluble content of 8wt%, a toluene insoluble content of 30wt%, a β-resin content of 22wt%, a softening point of 100°C, and a coking value of 65%; the additive is prepared by mixing boric acid, sodium dihydrogen phosphate, and water in a mass ratio of 1:1:5.

[0033] The method for preparing the graphite electrode for steelmaking is carried out according to the following steps:

[0034] (1) crushing, screening and grinding needle coke into graded materials of different particle sizes, mixing the graded materials uniformly, heating to 170° C., and then pouring them into a kneading pot, dry mixing for 10 minutes, adding tempered asphalt for wet mixing for 30 minutes, and then adding additives, and continuing wet mixing for 8 minutes to prepare a paste; the particle size composition of the graded materials of different particle sizes is: 5-7 mm 25wt%, 1-3 mm 35wt%, and the rest is less than 0.25 mm;

[0035] (2) pressing the paste prepared in step (1) to form a green embryo; the process parameters of the pressing and molding are as follows: using a 2500-ton press to evacuate and pre-press, the vacuum degree is -0.12, the pre-pressing pressure is 30 MPa, and the pre-pressing is performed for 8 minutes before extrusion molding;

[0036] (3) The green embryo prepared in step (2) is placed in a roasting furnace for roasting, and after roasting, is placed in a graphitization furnace for graphitization, with an initial power of 1200 kVA, a rising power of 300 kVA / h, and a maximum temperature of the graphitization furnace of 3000°C; the roasting process is: heating to 250°C at a rate of 25°C / h, then heating to 550°C at a rate of 10°C / h, then heating to 850°C at a rate of 20°C / h, and finally keeping warm for 4 hours.

[0037] Comparative Example 1

[0038] A graphite electrode for steelmaking is made from the following raw material components in parts by weight: 150 parts of Mizushima X-grade needle coke, 80 parts of modified asphalt, and 6 parts of pentaerythritol stearate; the modified asphalt has a quinoline insoluble content of 6wt%, a toluene insoluble content of 25wt%, a beta resin content of 20wt%, a softening point of 95°C, and a coking value of 60%.

[0039] The method for preparing the graphite electrode for steelmaking is carried out according to the following steps:

[0040] (1) crushing, screening and grinding needle coke into graded materials of different particle sizes, mixing the graded materials uniformly, heating to 160° C., and then pouring them into a kneading pot, dry mixing for 8 minutes, adding tempered asphalt and wet mixing for 25 minutes, and then adding pentaerythritol stearate and continuing wet mixing for 6 minutes to prepare a paste; the particle size composition of the graded materials of different particle sizes is: 5-7 mm 20wt%, 1-3 mm 30wt%, and the rest less than 0.25 mm;

[0041] (2) pressing the paste prepared in step (1) to form a green embryo; the process parameters of the pressing and molding are as follows: using a 2500-ton press to evacuate and pre-press, the vacuum degree is -0.1, the pre-pressing pressure is 25 MPa, and the pre-pressing is performed for 7 minutes before extrusion molding;

[0042] (3) placing the green embryo prepared in step (2) into a roasting furnace for roasting, and then placing it into a graphitization furnace for graphitization after roasting, with an initial power of 1000 kVA, a rising power of 200 kVA / h, and a maximum temperature of the graphitization furnace of 2800°C; the roasting process is as follows: heating to 200°C at a rate of 25°C / h, then heating to 500°C at a rate of 10°C / h, then heating to 800°C at a rate of 20°C / h, and finally keeping warm for 3 hours.

[0043] Comparative Example 2

[0044] A graphite electrode for steelmaking is made of the following raw material components in parts by weight: 150 parts of Water Island X-grade needle coke, 80 parts of modified asphalt, and 6 parts of phthalate; the modified asphalt has a quinoline insoluble content of 6wt%, a toluene insoluble content of 25wt%, a beta resin content of 20wt%, a softening point of 95°C, and a coking value of 60%.

[0045] The method for preparing the graphite electrode for steelmaking is carried out according to the following steps:

[0046] (1) crushing, screening and grinding needle coke into graded materials of different particle sizes, mixing the graded materials uniformly, heating to 160° C., and then pouring them into a kneading pot, dry mixing for 8 minutes, adding tempered asphalt and wet mixing for 25 minutes, and then adding phthalate and continuing wet mixing for 6 minutes to prepare a paste; the particle size composition of the graded materials of different particle sizes is: 5-7 mm 20wt%, 1-3 mm 30wt%, and the rest less than 0.25 mm;

[0047] (2) pressing the paste prepared in step (1) to form a green embryo; the process parameters of the pressing and molding are as follows: using a 2500-ton press to evacuate and pre-press, the vacuum degree is -0.1, the pre-pressing pressure is 25 MPa, and the pre-pressing is performed for 7 minutes before extrusion molding;

[0048] (3) placing the green embryo prepared in step (2) into a roasting furnace for roasting, and then placing it into a graphitization furnace for graphitization after roasting, with an initial power of 1000 kVA, a rising power of 200 kVA / h, and a maximum temperature of the graphitization furnace of 2800°C; the roasting process is as follows: heating to 200°C at a rate of 25°C / h, then heating to 500°C at a rate of 10°C / h, then heating to 800°C at a rate of 20°C / h, and finally keeping warm for 3 hours.

[0049] Comparative Example 3

[0050] A graphite electrode for steelmaking is made of the following raw material components in parts by weight: 200 parts of New World HSP-grade needle coke, 100 parts of modified asphalt, and 8 parts of additives; the modified asphalt has a quinoline insoluble content of 8wt%, a toluene insoluble content of 30wt%, a β-resin content of 22wt%, a softening point of 100°C, and a coking value of 65%; the additive is made of a mixture of boric acid and water in a mass ratio of 2:5.

[0051] The method for preparing the graphite electrode for steelmaking is carried out according to the following steps:

[0052] (1) crushing, screening and grinding needle coke into graded materials of different particle sizes, mixing the graded materials uniformly, heating to 170° C., and then pouring them into a kneading pot, dry mixing for 10 minutes, adding tempered asphalt for wet mixing for 30 minutes, and then adding additives, and continuing wet mixing for 8 minutes to prepare a paste; the particle size composition of the graded materials of different particle sizes is: 5-7 mm 25wt%, 1-3 mm 35wt%, and the rest is less than 0.25 mm;

[0053] (2) pressing the paste prepared in step (1) to form a green embryo; the process parameters of the pressing and molding are as follows: using a 2500-ton press to evacuate and pre-press, the vacuum degree is -0.12, the pre-pressing pressure is 30 MPa, and the pre-pressing is performed for 8 minutes before extrusion molding;

[0054] (3) The green embryo prepared in step (2) is placed in a roasting furnace for roasting, and after roasting, is placed in a graphitization furnace for graphitization, with an initial power of 1200 kVA, a rising power of 300 kVA / h, and a maximum temperature of the graphitization furnace of 3000°C; the roasting process is: heating to 250°C at a rate of 25°C / h, then heating to 550°C at a rate of 10°C / h, then heating to 850°C at a rate of 20°C / h, and finally keeping warm for 4 hours.

[0055] Comparative Example 4

[0056] A graphite electrode for steelmaking is prepared from the following raw material components in parts by weight: 200 parts of New World HSP-grade needle coke, 100 parts of modified asphalt, and 8 parts of additives; the modified asphalt has a quinoline insoluble content of 8wt%, a toluene insoluble content of 30wt%, a β-resin content of 22wt%, a softening point of 100°C, and a coking value of 65%; the additive is prepared by mixing sodium dihydrogen phosphate and water in a mass ratio of 2:5.

[0057] The method for preparing the graphite electrode for steelmaking is carried out according to the following steps:

[0058] (1) crushing, screening and grinding needle coke into graded materials of different particle sizes, mixing the graded materials uniformly, heating to 170° C., and then pouring them into a kneading pot, dry mixing for 10 minutes, adding tempered asphalt for wet mixing for 30 minutes, and then adding additives, and continuing wet mixing for 8 minutes to prepare a paste; the particle size composition of the graded materials of different particle sizes is: 5-7 mm 25wt%, 1-3 mm 35wt%, and the rest is less than 0.25 mm;

[0059] (2) pressing the paste prepared in step (1) to form a green embryo; the process parameters of the pressing and molding are as follows: using a 2500-ton press to evacuate and pre-press, the vacuum degree is -0.12, the pre-pressing pressure is 30 MPa, and the pre-pressing is performed for 8 minutes before extrusion molding;

[0060] (3) The green embryo prepared in step (2) is placed in a roasting furnace for roasting, and after roasting, is placed in a graphitization furnace for graphitization, with an initial power of 1200 kVA, a rising power of 300 kVA / h, and a maximum temperature of the graphitization furnace of 3000°C; the roasting process is: heating to 250°C at a rate of 25°C / h, then heating to 550°C at a rate of 10°C / h, then heating to 850°C at a rate of 20°C / h, and finally keeping warm for 4 hours.

[0061] Experimental example:

[0062] According to the standard GB3074.1-1982 "Measurement Method for Flexural Strength of Graphite Electrode", the flexural strength (MPa) of the graphite electrodes prepared in Example 1-2 and Comparative Example 1-2 was measured. Each group of experiments was measured 3 times and the average value was taken. The experimental results were statistically analyzed using SPSS24.0 software. The quantitative data results were expressed as x±(mean±standard deviation). The Kolmogorov-Smirnov test method was used for data normality test. For data that conformed to normal distribution, the mean difference between the two groups was compared using t-test, and P<0.05 was considered statistically significant. The measurement results are shown in Table 1:

[0063] Table 1

[0064]

[0065] Note: * represents P < 0.05 compared with the group in Example 1.

[0066] According to the standard GB / T 6717-1986 "Method for Determining the Resistivity of Carbon Materials", the resistivity (μΩm) of the graphite electrodes prepared in Example 3 and Comparative Examples 3-4 was measured. The measurement results are shown in Table 2:

[0067] Table 2

[0068]

[0069] Note: * represents P < 0.05 compared with the group in Example 3.

[0070] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A graphite electrode for steelmaking, characterized in that: The invention is prepared from the following raw material components in parts by weight: 100-200 parts of needle coke, 50-100 parts of tempered asphalt and 2-8 parts of additives.

2. The graphite electrode for steelmaking according to claim 1, characterized in that: The needle coke is one or more of Xingya S-JA grade petroleum needle coke, Mizushima X grade needle coke, and New World HSP grade needle coke.

3. The graphite electrode for steelmaking according to claim 1, characterized in that: The modified asphalt has a quinoline insoluble matter content of 4-8wt%, a toluene insoluble matter content of 20-30wt%, a beta resin content of 18-22wt%, a softening point of 90-100°C, and a coking value of ≥55%.

4. The graphite electrode for steelmaking according to claim 1, characterized in that: The additive is a mixture of pentaerythritol stearate and phthalate in a mass ratio of 1:

1.

5. The graphite electrode for steelmaking according to claim 1, characterized in that: The additive is prepared by mixing boric acid, sodium dihydrogen phosphate and water in a mass ratio of 1:1:

5.

6. The method for preparing the graphite electrode for steelmaking according to claim 1, characterized in that: Follow these steps: (1) The needle coke is crushed, screened, and ground into graded materials of different particle sizes, each graded material is mixed evenly, heated to 150-170° C., and then poured into a kneading pot, dry mixed for 6-10 minutes, and then the tempered asphalt is added and wet mixed for 20-30 minutes, and then the additive is added and wet mixed for 5-8 minutes to make a paste; (2) pressing the paste prepared in step (1) into a green embryo; (3) The green embryo prepared in step (2) is placed in a calcining furnace for calcination, and after calcination, is placed in a graphitization furnace for graphitization, with an initial power of 800-1200 kVA, a rising power of 100-300 k VA / h, and a maximum temperature of the graphitization furnace of 2600-3000°C.

7. The method for preparing a graphite electrode for steelmaking according to claim 7, characterized in that: The particle size composition of the graded materials of different particle sizes in step (1) is: 5-7mm 15-25wt%, 1-3mm 20-35wt%, and the rest is less than 0.25mm.

8. The method for preparing a graphite electrode for steelmaking according to claim 7, characterized in that: The process parameters of the compression molding are as follows: vacuum pre-pressing with a 2500-ton press, a vacuum degree of less than -0.08, a pre-pressing pressure of 20-30 MPa, and extrusion molding after pre-pressing for 6-8 minutes.

9. The method for preparing a graphite electrode for steelmaking according to claim 7, characterized in that: The calcination process is: heating to 150-250°C at a speed of 25°C / h, then heating to 450-550°C at a speed of 10°C / h, then heating to 750-850°C at a speed of 20°C / h, and finally keeping the temperature for 2-4h.

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