RU2568493C1 - Method of packing large-size isostatic moulding fine-grain graphite workpieces during graphitation - Google Patents

Method of packing large-size isostatic moulding fine-grain graphite workpieces during graphitation Download PDF

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RU2568493C1
RU2568493C1 RU2014134638/05A RU2014134638A RU2568493C1 RU 2568493 C1 RU2568493 C1 RU 2568493C1 RU 2014134638/05 A RU2014134638/05 A RU 2014134638/05A RU 2014134638 A RU2014134638 A RU 2014134638A RU 2568493 C1 RU2568493 C1 RU 2568493C1
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workpiece
thickness
graphite
core
length
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RU2014134638/05A
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Валентин Петрович Перевезенцев
Наталия Юрьевна Бейлина
Ольга Васильевна Рубинчик
Анна Дмитриевна Бакланова
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Акционерное общество "Научно-исследовательский институт конструкционных материалов на основе графита "НИИграфит"
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Abstract

FIELD: chemistry.
SUBSTANCE: method of packing fired carbonaceous large-size isostatic moulding fine-grain graphite workpieces during graphitation includes arrangement thereof vertically and horizontally across the core in columns, separated from each other by layers of core filling with thickness of about 0.2 times the diameter of the workpiece. The lateral sides of each workpiece are tightly attached to flat heat-transfer panels made of highly heat-conductive and high-temperature structural graphite. The width of the panel is equal to the diameter or thickness, in case of a workpiece with a rectangular cross-section, and the length is respectively equal to the length of the workpiece, the thickness is not less than 0.15 times of its diameter or thickness, in the case of a workpiece with a rectangular cross-section. The heat-transfer panels can be composite in the direction of their length.
EFFECT: reducing heat stress in the body of the workpiece, reducing graphite consumption and specific energy consumption owing to a 40% reduction of the mass of additional components of the graphite articles.
2 cl

Description

The invention relates to the production of graphitized structural materials, and in particular to the operation of graphitization.
Currently, the graphitization of such preforms is carried out in industrial graphitization furnaces according to the Acheson method (1). Billets in the core are located standing or lying across the furnace in columns within the core size of a particular furnace. The workpiece columns are separated by core layers of coke (KM) core filling or Pecokoks fines (PCM) fraction (4-15) mm thick with a thickness of approximately 0.2V (in is the column width of the loaded workpieces). The core is surrounded on all sides by layers of heat-insulating powder (350-500) mm thick on the sides of the core and on the upper side (the so-called "blanket"). KM or PCM fractions (0-4) mm are used as heat insulating fillings. In graphitization furnaces according to the Acheson method, the heating of graphite preforms in the core is carried out from core layers of bedding, i.e. from two sides, which leads to large temperature gradients in the sides of the workpieces, i.e. to high temperature stresses and, as a consequence, to the appearance of cracks and the destruction of workpieces. Therefore, the electrical modes of graphitization are developed with the calculation of the heating rate of 20-25 ° C / h in the temperature range 0-1800 ° C. This leads to a company duration of more than 80 hours and a high specific energy consumption. Even under such “soft” modes of core heating, the yield of suitable preforms of fine-grained graphite of isostatic pressing with a diameter of 338 mm and a length of 800 mm in production at one of the electrode plants does not exceed 40 percent of the batch loaded into the furnace.
A known method of packaging carbon cylindrical billets in a graphitization furnace, which allows graphitization to equalize the temperature field along the entire length of the workpiece, which provides more uniform heating of the workpiece along its length (2). The distinguishing features of this invention is the alternation of vertical and horizontal rows of the load with respect to the longitudinal axis of the furnace.
This method has the following disadvantages.
In the method of packaging according to the above invention, the temperature field does not equalize over the entire side surface of the workpiece, the temperature field is aligned only along the length of the workpiece. The heating mode for large workpieces must be very slow to ensure a low level of thermal stresses, that is, to preserve the integrity of the workpiece, this will require an increased consumption of specific energy. The actual duration of the campaign will be more than 80 hours.
The method is also complicated in the execution of core loading, as it requires additional templates and ensuring the stability of the columns of blanks arranged vertically.
Currently, the task is to manufacture large-sized preforms of fine-grained graphite of isostatic pressing with a diameter of 500 mm or more and a length of up to 1000 mm.
The basis of the invention is the task of reducing the specific energy consumption for graphitization of large-sized preforms of fine-grained graphite isostatic pressing in a graphitization furnace and increasing the yield of prefabricated.
The proposed new method of packaging large-sized preforms of fine-grained graphite with isostatic pressing during graphitization, including arranging the preforms in the core vertically or horizontally across the core into columns separated from each other by core layers with a thickness of approximately 0.2 of the diameter of the large-sized preform, characterized in that on the sides of each heat-transfer flat panels equal to the diameter (or thickness, in the case of a rectangular cross-section workpiece) are placed close to it ) And a length respectively equal to the length of the preform and thickness not less than 0.15 of its diameter (or thickness, in the case of rectangular billet) made of high thermal conductivity and high structural graphite. In addition, heat transfer panels can be made integral in the direction of their length.
The proposed method of core assembly of a graphitization furnace can be applied to graphitization of large-sized isostatic pressing blanks having a different cross-sectional shape, for example, rectangular. In this case, the width of the panel will be not less than the thickness of the bulky workpiece.
As a material for the manufacture of panels, it is better to use blanks of structural graphite of the GMZ, PPG, ZOPG grades, as well as blanks of electrode graphite. In the direction of the length of the panel can be composite, that is, made of separate parts, in the sum equal to the length of the workpiece.
In the case of traditional loading into columns, a large billet is heated from the front and back sides of the intercolumn layers of core filling. This leads to an uneven temperature field over the entire side surface of the workpiece. The main and main task of the panels is to deliver additional heat from the core inter-pillar interlayers in which the electrical energy is converted into heat to the side surfaces of large-sized blanks. This provides conditions for comprehensive heating of the workpiece, close to axisymmetric, that is, it increases the heat-absorbing surface area of the workpiece by more than 1.5 times, thereby increasing the speed of heating the workpiece with the same temperature gradient and thermal stress level. The time of the graphitization campaign is reduced, the specific energy consumption is reduced at high yield of billets.
Compared with the prototype, in the proposed method of core packing during graphitization of large-sized billets, the physical and technical basis of the process of heating large-sized billets is changed. In the prototype, when moving along the core along the axis of the furnace, the electric current is evenly distributed over the core cross section, i.e. in relation to a separate large-sized billet placed in the filling. Thus, heat is transferred from the inter-column layers of core filling to large-sized workpiece. Part of the heat due to the high thermal conductivity of the bedding provides lateral heating of the workpiece. In this case, although there is a partial equalization of the temperature field on the surface of the large-sized workpiece, a certain level of thermal stresses remains in the body of the large-sized workpiece.
In the proposed method of core packing during graphitization of large-sized workpieces, the distribution of electric current strength over the core cross section will be uneven. Consider a separate core loading element - the workpiece and adjacent side panels. In each such element we have three electrical conductors located parallel to each other. Two of them are composed of an inter-column core core bed of a given thickness and panels (in width) arranged in series in the direction of the furnace axis, and the third one is from the same core core bed and workpiece diameter. The total lengths of each of the conductors are the same. Our panel conductors have lower resistance due to the fact that the resistivity of graphite panels is lower than the resistivity of the fired blank. In accordance with Kirchhoff’s law, the distribution of current strength across parallel conductors is inversely proportional to electrical resistance. Therefore, the current density on the end surfaces of the panels will be higher than on the front and rear sides of the large workpiece. Since heat generation depends on the square of the current strength, there will be a higher temperature on the end surfaces of the panels than on the front and back sides of the workpiece. The high thermal conductivity of the material of the side panels ensures the maintenance of a correspondingly high temperature on the side surfaces of the large workpiece, i.e. creates heating conditions on its lateral surfaces the same as on its front and rear sides. In the four-sided direction of the heat flux of a large-sized workpiece, the temperature field along its lateral surface will be more uniform than with the direction of the prototype, and, therefore, the level of thermal stress is lower at the same core heating speeds. The thickness of the side panels must be at least 0.15 of the diameter of the workpiece. In this case, the heat-absorbing surface area of the two panels will be ≥0.30 d × h, and the area of the equal-sized parallelepiped blank with dimensions d x (π / 2 × r) × h will be (π / 2 × r) × h.
The electrical resistance of half of the workpiece and two halves of the panels will be respectively
Figure 00000001
and
Figure 00000002
In this expression, 40 μΩ × m and 8 μΩ × m are the electrical resistivity of the calcined billet and GMZ graphite panels at a temperature of 0 ° C. Their ratio R blanks / R panels ≈2. This means that more electric current will flow through the side panels and there will be more heat generation in the area of the heat transfer surfaces of the panels, which means that the temperature is higher. When the thermal conductivity of graphite is much higher than that of the calcined billet, heat will be transferred to the contact zone of the panels with the billet and provide heating of the billet from the sides, creating a more uniform heating of the billet from all sides.
The proposed method was tested during graphitization of workpieces with a diameter of 338 mm and a length of 800 mm. Panels 55 × 338 × 800 mm in size were made of GMZ graphite. The graphitization campaign lasted 60 hours, which reduced energy consumption by 15%. This is also one of the positive aspects of the proposed method. The results of the industrial verification of the proposed method are positive. Defects on the cracks of the workpieces were not observed. According to their physical and technical properties, they corresponded to technical conditions.
The proposed method of core packing during graphitization of large-sized preforms of fine-grained graphite of isostatic pressing is also convenient because in the absence of flat preforms of graphite of the required length, the heat transfer panels can be made of individual parts, that is, lengthwise components. In a number of experiments, the side panels were cut in length into two parts, each of which had dimensions of 400 × 338 × 55 mm. The results showed that with composite panels, the yield of blanks turned out to be at the same level as with solid lengths.
Thus, the introduction of heat transfer panels when loading large-sized preforms of fine-grained graphite of isostatic pressing into the graphitization furnace allows heat to be supplied to the side parts of the preforms and to ensure the preform is heated from four sides. This reduces the level of thermal stresses in the body of the workpiece. With this method of core packing, the specific energy consumption is reduced by 15% due to a 25% reduction in the lead time of the graphitization process compared to the prototype. Graphite consumption for the manufacture of component parts is reduced due to simpler forms of smaller overall dimensions.
Information sources
1. V.P. Sosedov, E.F. Chalykh. "Graphitization of carbon materials." M .: "Metallurgy", 1987, p. 126-166.
2. USSR author's certificate No. 998337, MKI C01B 31/04, publ. 02/23/1983, "The method of packaging carbon cylindrical billets in a graphitization furnace."

Claims (2)

1. The method of packaging carbon burnt large-sized preforms of fine-grained graphite isostatic pressing during graphitization, including the location of the workpieces vertically and horizontally across the core in columns separated from each other by core layers with a thickness of approximately 0.2 diameter of the workpiece, characterized in that on the sides of each workpiece close to it, heat transfer flat panels are placed, with a width equal to the diameter or thickness, in the case of a blank of rectangular cross section, and with a length of equal to the length of the workpiece, with a thickness of at least 0.15 of its diameter or thickness, in the case of a workpiece of rectangular cross section, made of high-heat-conducting and high-temperature structural graphite.
2. The method according to p. 1, characterized in that the heat transfer panels can be made integral in the direction of their length.
RU2014134638/05A 2014-08-26 2014-08-26 Method of packing large-size isostatic moulding fine-grain graphite workpieces during graphitation RU2568493C1 (en)

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU998337A1 (en) * 1981-08-20 1983-02-23 Государственный Научно-Исследовательский И Проектно-Конструкторский Институт Электродной Промышленности Method for making packages of cylindrical carbon blanks in graphitization furnaces
SU1685868A1 (en) * 1989-07-11 1991-10-23 Предприятие П/Я М-5409 Method for bundling long and large carbon blanks in roasting
SU1691300A1 (en) * 1987-10-30 1991-11-15 Предприятие П/Я М-5409 Method of stacking carbon blanks
SU1692937A1 (en) * 1988-07-05 1991-11-23 Предприятие П/Я М-5409 Method for packing of carbon cylindrical billets for graphitation
SU1764283A1 (en) * 1990-05-15 1994-05-15 Государственный научно-исследовательский институт конструкционных материалов на основе графита Method of packing elongated carbon blanks in graphitizing furnaces
SU1790136A1 (en) * 1990-09-25 1995-06-27 Государственный научно-исследовательский, проектный и конструкторский институт электродной промышленности Carbon-containing charge for large-sized graphitized blanks
RU2059591C1 (en) * 1992-03-18 1996-05-10 Государственный научно-исследовательский институт конструкционных материалов на основе графита Graphitization furnaces sample packing method

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU998337A1 (en) * 1981-08-20 1983-02-23 Государственный Научно-Исследовательский И Проектно-Конструкторский Институт Электродной Промышленности Method for making packages of cylindrical carbon blanks in graphitization furnaces
SU1691300A1 (en) * 1987-10-30 1991-11-15 Предприятие П/Я М-5409 Method of stacking carbon blanks
SU1692937A1 (en) * 1988-07-05 1991-11-23 Предприятие П/Я М-5409 Method for packing of carbon cylindrical billets for graphitation
SU1685868A1 (en) * 1989-07-11 1991-10-23 Предприятие П/Я М-5409 Method for bundling long and large carbon blanks in roasting
SU1764283A1 (en) * 1990-05-15 1994-05-15 Государственный научно-исследовательский институт конструкционных материалов на основе графита Method of packing elongated carbon blanks in graphitizing furnaces
SU1790136A1 (en) * 1990-09-25 1995-06-27 Государственный научно-исследовательский, проектный и конструкторский институт электродной промышленности Carbon-containing charge for large-sized graphitized blanks
RU2059591C1 (en) * 1992-03-18 1996-05-10 Государственный научно-исследовательский институт конструкционных материалов на основе графита Graphitization furnaces sample packing method

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Title
СОСЕДОВ В.П., ЧАЛЫХ Е.Ф., Графитация углеродистых материалов, Москва, Металлургия, 1987, с.с. 126-166. *

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