Method for evaluating service life of carbon sleeve of silicon steel continuous annealing furnace

Abstract

The invention discloses a method for evaluating the service life of a carbon sleeve of a silicon steel continuous annealing furnace, which comprises the following steps of: drying the carbon sleeve, and weighing the mass of the carbon sleeve; putting the dried carbon sleeve sample into a hearth of a heating furnace, and introducing dry high-purity nitrogen into the hearth; a heating curve is set, mixed gas of dry high-purity nitrogen and hydrogen is introduced, and heating is started; after the temperature in the furnace reaches the set temperature, wet mixed gas of nitrogen and hydrogen is introduced; after heat preservation is conducted for a period of time, dry mixed gas of nitrogen and hydrogen is introduced, and introduction of wet mixed gas of nitrogen and hydrogen is stopped; when the temperature in the hearth is reduced to be lower than the set temperature, stopping introducing the hydrogen firstly, and then stopping introducing the nitrogen; taking out the cooled carbon sleeve sample in the hearth, weighing the mass of the sample, calculating the weight loss ratio of the sample, and evaluating the service life of the carbon sleeve according to the weight loss ratio. According to the method, the service life of the carbon sleeve can be evaluated in a short time, so that the risk of online trial of the carbon sleeve is reduced, and production and safety accidents are avoided.

Description

Technical Field

[0001] The invention specifically relates to a method for evaluating the service life of a carbon sleeve of a silicon steel continuous annealing furnace. Background Art

[0002] Graphite has a unique laminated structure, low hardness, good self-lubrication, and small thermal expansion coefficient. Graphite carbon sleeves are the best furnace bottom rollers for supporting and transmitting steel strips in silicon steel continuous annealing furnaces. Graphite materials are chemically inert in non-oxygen media and will not undergo any chemical changes at room temperature and pressure. However, the temperature at which graphite begins to have an obvious oxidation reaction is about 450°C, and it begins to react with water vapor above 700°C and with CO2 above 900°C. The graphite carbon sleeves in the silicon steel continuous annealing furnace need to be used in a high temperature environment of 800°C to 1000°C for a long time, or even above 1050°C. The carbon sleeves running in the silicon steel continuous annealing furnace may be corroded by oxidizing media (such as H2O, CO2, O2, etc.). How to accurately and scientifically detect and evaluate the service life of carbon sleeves under special atmosphere conditions in silicon steel continuous annealing furnaces is particularly important for the silicon steel and carbon industries.

[0003] The maintenance cycle of silicon steel continuous annealing line is generally 6 to 8 months, or even longer, so it is difficult to evaluate the service life of the carbon sleeve through online testing. In the silicon steel continuous annealing furnace, the atmosphere is generally high-purity nitrogen, high-purity hydrogen, or a mixed atmosphere of high-purity nitrogen and hydrogen, and there may be a high dew point. Therefore, it is necessary to refer to the actual environmental conditions of the carbon sleeve, adopt scientific accelerated test methods, and use appropriate test equipment to evaluate its service life in a shorter time.

[0004] Graphite has a unique layered structure, low hardness, good self-lubrication, small thermal expansion coefficient, excellent thermodynamic properties and nuclear properties, and is widely used in silicon steel, atomic energy, refractory materials, conductive materials, lubricating materials and other fields. The graphite substrate itself has poor antioxidant properties and generally needs to be treated with antioxidants before use. Even after antioxidant treatment, graphite materials and components will still react with O2, H2O, CO2, etc. under certain temperature conditions, resulting in material failure and even causing serious safety accidents. The maintenance cycle of the silicon steel continuous withdrawal line is very long, and it is difficult to evaluate the service life of the graphite carbon sleeve through online testing. Therefore, it is necessary to refer to the actual environmental conditions of the carbon sleeve, use appropriate test equipment, and adopt scientific accelerated test methods to evaluate its antioxidant properties in a relatively short period of time, and then more accurately evaluate its service life, so as to reduce the risk of online trials and avoid production and safety accidents. Summary of the invention

[0005] The purpose of the present invention is to provide a method for evaluating the service life of a carbon sleeve of a silicon steel continuous annealing furnace, which can evaluate the service life of the carbon sleeve in a relatively short time to reduce the risk of online trial use and avoid production and safety accidents.

[0006] The technical solution adopted by the present invention is: A method for evaluating the service life of a carbon sleeve of a silicon steel continuous annealing furnace comprises the following steps: Step 1, drying the carbon sleeve and weighing its mass W0; turning on the gas humidifier, starting the humidifier to heat up, and turning on the electric heating system; Step 2, open the door of the heating furnace, place the dried carbon jacket sample into the furnace, close the door, and introduce dry high-purity nitrogen; Step 3, setting a heating curve, introducing a mixture of dry high-purity nitrogen and hydrogen, and starting to heat up; Step 4, when the temperature in the furnace reaches the set temperature T1, open the wet ball valve, start to introduce the wet nitrogen and hydrogen mixed gas, and then close the dry ball valve to stop introducing the dry nitrogen and hydrogen mixed gas; Step 5, after keeping warm for a period of time, open the dry ball valve, introduce a mixed gas of dry nitrogen and hydrogen, and then close the wet ball valve to stop introducing the mixed gas of wet nitrogen and hydrogen; Step 6, when the temperature in the furnace drops below the set temperature T2, then close the hydrogen ball valve, wait until the flame at the hydrogen ignition burner is extinguished, close the nitrogen ball valve, and stop introducing gas; Step 7, open the furnace door, take out the sample after cooling in the furnace, weigh the mass W1 of the sample, calculate its weight loss rate SZL, and evaluate the service life of the carbon sleeve according to the weight loss rate SZL; The specific process of evaluating the service life of the carbon sleeve according to the weight loss rate SZL is: when the weight loss rate SZL≤1.0%, the service life of the carbon sleeve is more than 8 months; when 1%<weight loss rate SZL≤3%, the service life of the carbon sleeve is 6 to 8 months; when 3%<weight loss rate SZL<5%, the service life of the carbon sleeve is 3 to 6 months; when the weight loss rate SZL≥5%, the service life of the carbon sleeve is less than 3 months.

[0007] Preferably, before the step 1, the carbon sleeve is processed into a cylindrical sample of φ30 mm×30 mm, or a cube sample of 30 mm×30 mm×30 mm.

[0008] Preferably, in step 1, the drying temperature is within the temperature range of 105°C to 110°C.

[0009] Preferably, the outer jacket of the pipeline for introducing nitrogen and hydrogen is provided with an electric heating system. Preferably, in the step 1, the gas humidifier is turned on, the target dew point is set to 85°C, and the humidifier is started to heat up. Dry nitrogen and hydrogen refer to nitrogen and hydrogen that have not been humidified by the gas humidifier, and wet nitrogen and hydrogen refer to nitrogen and hydrogen that have been humidified by the gas humidifier, forming high dew point nitrogen and hydrogen. Preferably, in step 2, high-purity nitrogen is introduced for 10 to 20 minutes at a nitrogen flow rate of 20 to 30 L / min.

[0010] In a specific embodiment, it is preferred to introduce high-purity nitrogen for 15 minutes at a nitrogen flow rate of 25 L / min.

[0011] Preferably, in step 3, the maximum temperature of the temperature rise curve is set to 1150° C. to 1250° C.; a mixed gas of high-purity nitrogen and hydrogen is introduced, and the gas flow rate is 25 L / min to 35 L / min.

[0012] In the specific embodiment, it is preferred that the highest temperature of the temperature rise curve is set to 1200° C.; a mixed gas of high-purity nitrogen and hydrogen is introduced, and the gas flow rate is 30 L / min.

[0013] Preferably, in step 4, the temperature T1 is set to 1150°C-1250°C.

[0014] In the specific embodiment, it is preferred that in step 4, when the temperature in the furnace reaches the set temperature T1=1200°C, the wet ball valve is opened to introduce a mixed gas of wet nitrogen and hydrogen, and then the introduction of the mixed gas of dry nitrogen and hydrogen is stopped.

[0015] Preferably, in step 5, after keeping warm for 2.5 to 3.5 hours, the valve of the dry ball is opened to introduce a mixed gas of dry nitrogen and hydrogen, and the introduction of the mixed gas of wet nitrogen and hydrogen is stopped.

[0016] In a specific embodiment, it is preferred that in step 5, after keeping the temperature at 1200° C. for 2.5 to 3.5 hours, the dry ball valve is opened to introduce a mixed gas of dry nitrogen and hydrogen.

[0017] Preferably, in step 6, the temperature T2 is set to 40°C; When the temperature in the furnace drops below 40°C, adjust the nitrogen flow rate to 25L / min, then close the hydrogen ball valve. After the flame at the hydrogen ignition burner is extinguished, close the nitrogen ball valve and stop introducing gas.

[0018] Preferably, in step 7, the formula for calculating the weight loss rate is: Weight loss rate (SZL) = 100% × (W0-W1) / W0, where W0 is the mass of the sample after drying, and W1 is the mass of the sample after cooling after the antioxidant test. The beneficial effects of the present invention are: This method can simulate the test of accelerating the service life of the carbon sleeve. According to the weight loss rate of the carbon sleeve sample after the test, the service life of the carbon sleeve can be evaluated in a short time to reduce the risk of online trial and avoid production and safety accidents. It can also be used as a quality and service life evaluation method for graphite materials in the metallurgical, nuclear and carbon industries. At the same time, silicon steel product manufacturers can also refer to the evaluation of the anti-oxidation performance and service life of the carbon sleeve, and choose suitable carbon sleeve products according to their own silicon steel production lines and product conditions, which can improve silicon steel production efficiency and product quality and reduce production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of a carbon sleeve service life acceleration test device in an embodiment of the present invention.

[0020] In the figure: 1-furnace door; 2-hydrogen ignition burner; 3-exhaust ball valve; 4-guide pipe; 5-furnace chamber; 6-furnace shell; 7-heat-resistant and thermal insulation material; 8-heating and temperature control system; 9-hydrogen ball valve; 10-hydrogen flow meter; 11-nitrogen ball valve; 12-nitrogen flow meter; 13-gas mixing chamber; 14-mixing ball valve; 15-gas humidifier; 16-mixing dry ball valve; 17-mixing wet ball valve; 18-ventilation pipe; 19 electric heating system. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] In the description of the present invention, it should be understood that if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like are involved, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0023] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be directly connected or indirectly connected through an intermediate medium. It can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] Example 1 A method for evaluating the service life of a carbon sleeve of a silicon steel continuous annealing furnace comprises the following steps: Step 1, processing the carbon sleeve into a cylindrical sample of φ30mm×30mm, drying it at a temperature range of 105°C to 110°C, and weighing its mass W0; Step 2, open the furnace door 1, put the carbon jacket sample into the furnace 5, close the furnace door 1, open the exhaust ball valve 3, close the mixing ball valve 14, open the mixed dry ball valve 16, open the nitrogen ball valve 11, the nitrogen flow rate is 25L / min, and pass dry nitrogen for 15min; Step 3, turn on the gas humidifier 15, set the target dew point to 85°C, start heating the humidifier 15, and turn on the electric heating system 19; Step 4, turn on the heating temperature control system 8 of the heating furnace, set the heating curve, the highest temperature is 1200℃: the heating rate from room temperature to 800℃ is 8-12℃ / min, the best is 10℃ / min, the heating rate from 800℃ to 1000℃ is 3-8℃ / min, the best is 5℃ / min; the heating rate from 1000℃ to 1100℃ is 2-4℃ / min, the best is 3℃ / min; the heating rate from 1100℃ to 1200℃ is 1-3℃ / min, the best is 2℃ / min. Introduce dry high-purity hydrogen and nitrogen, the hydrogen flow rate is 15L / min, the nitrogen flow rate is 15L / min, ignite the hydrogen of the hydrogen ignition burner 2, and start heating; Step 5, when the temperature in the furnace reaches 1200°C and it is confirmed that the water temperature of the humidifier 15 has reached 85°C, open the mixing ball valve 14, open the nitrogen and hydrogen mixed wet ball valve 17, close the nitrogen and hydrogen mixed dry ball valve 16, and start to introduce wet high-purity nitrogen and hydrogen mixed gas; Step 6, after keeping the temperature at 1200° C. for 3 hours, open the mixed dry gas ball valve 16, introduce the nitrogen and hydrogen mixed dry gas, close the nitrogen and hydrogen mixed gas ball valve 14, close the nitrogen and hydrogen mixed wet gas ball valve 17, and stop introducing the wet nitrogen and hydrogen mixed gas; Step 7, when the temperature in the furnace drops below 40°C, adjust the nitrogen flow rate to 25L / min, then close the hydrogen ball valve 9, and after the flame of the hydrogen ignition burner 2 is extinguished, close the nitrogen ball valve 11 to stop introducing the gas; Step 8, open the furnace door 1, take out the sample after cooling in the furnace, weigh the mass W1 of the carbon jacket sample, and calculate its weight loss rate.

[0025] Example 2 The weight loss rate is further limited on the basis of Example 1, and the limited Example 2 can directly evaluate the service life of the carbon sleeve.

[0026] In step 8, the formula for calculating the weight loss rate is: weight loss rate (SZL) = 100% × (W0-W1) / W0, where W0 is the mass of the sample after drying, and W1 is the mass of the sample after cooling after the antioxidant test is completed.

[0027] According to the actual oxidation weight loss rate (SZL) of the carbon sleeve, the service life of the carbon sleeve can be directly evaluated by referring to the following basis: When SZL≤1.0%, the service life of the carbon sleeve is more than 8 months; When 1%<SZL≤3%, the service life of the carbon sleeve is 6 to 8 months; When 3%<SZL<5%, the service life of the carbon sleeve is 3 to 6 months; When SZL ≥ 5%, the service life of the carbon sleeve is less than 3 months.

[0028] Therefore, the carbon sleeve service life accelerated test device is used to implement the silicon steel continuous annealing furnace carbon sleeve service life evaluation method. According to the weight loss rate of the carbon sleeve sample after the test, the service life of the carbon sleeve can be evaluated in a short time to reduce the risk of online trial and avoid production and safety accidents. It can also be used as a quality and service life evaluation method for graphite materials in the metallurgical, nuclear and carbon industries. Silicon steel companies can refer to the evaluation of the anti-oxidation performance and service life of the carbon sleeve and choose suitable carbon sleeve products according to their own silicon steel production lines and product conditions.

[0029] like Figure 1 As shown, the carbon sheath service life accelerated test device of the present invention comprises a heating furnace, a heating and temperature control system 8, a heat-resistant and heat-insulating material 7 and a furnace shell 6 are sequentially sheathed outside the furnace of the heating furnace, a ventilation pipe 18 is connected to one end of the furnace, an electric heating system 19 is wrapped outside the ventilation pipe 18, the ventilation pipe 18 is respectively connected to one end of a dry gas pipe and a wet gas pipe, a mixed dry gas ball valve 16 and a mixed wet gas ball valve 17 are respectively provided on the dry gas pipe and the wet gas pipe, a gas mixing chamber 13 is connected to the other end of the dry gas pipe and the wet gas pipe, a gas humidifier 15 is provided on the wet gas pipe, the gas mixing chamber 13 is respectively connected to a hydrogen pipe and a nitrogen pipe, a hydrogen ball valve 9 and a nitrogen ball valve 11 are respectively provided on the hydrogen pipe and the nitrogen pipe, flow meters are provided on the hydrogen pipe and the nitrogen pipe, respectively, a hydrogen flow meter 10 and a nitrogen flow meter 12.

[0030] It is composed of a heating furnace, a flow guide pipe 4, a gas humidifier 15, an electric heating system 19, etc., wherein the heating furnace includes a furnace chamber 5, a furnace shell 6, heat-resistant insulation materials 7, and a heating temperature control system 8. The purity of the high-purity nitrogen and hydrogen introduced during the experiment is above 99.99%, and the weighing balance has a sensitivity of 0.01g. It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0031] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for evaluating the service life of a carbon sleeve of a silicon steel continuous annealing furnace, characterized in that: The following steps are involved: Step 1, drying the carbon sleeve and weighing its mass W0; Step 2, open the door of the heating furnace, place the dried carbon jacket sample into the furnace of the heating furnace, close the door, and introduce dry high-purity nitrogen into the furnace; Step 3, setting a heating curve, introducing a mixture of dry high-purity nitrogen and hydrogen, and starting to heat up; Step 4, when the temperature in the furnace reaches the set temperature T1, a mixed gas of wet nitrogen and hydrogen is introduced, and then the introduction of the mixed gas of dry nitrogen and hydrogen is stopped; Step 5, after keeping warm for a period of time, introducing a mixed gas of dry nitrogen and hydrogen, and then stopping the introduction of the mixed gas of wet nitrogen and hydrogen; Step 6, when the temperature in the furnace drops below the set temperature T2, first stop introducing hydrogen, and then stop introducing nitrogen; Step 7, open the furnace door, take out the carbon jacket sample after cooling in the furnace, weigh the mass W1 of the sample, calculate its weight loss rate SZL, and evaluate the service life of the carbon jacket according to the weight loss rate SZL.

2. The method for evaluating the service life of a carbon sleeve of a silicon steel continuous annealing furnace according to claim 1, characterized in that: The specific process of evaluating the service life of the carbon sleeve according to the weight loss rate SZL is: when the weight loss rate SZL≤1.0%, the service life of the carbon sleeve is more than 8 months; when 1%<weight loss rate SZL≤3%, the service life of the carbon sleeve is 6 to 8 months; when 3%<weight loss rate SZL<5%, the service life of the carbon sleeve is 3 to 6 months; when the weight loss rate SZL≥5%, the service life of the carbon sleeve is less than 3 months.

3. The method for evaluating the service life of a carbon sleeve of a silicon steel continuous annealing furnace according to claim 1, characterized in that: In the step 1, the carbon sleeve drying temperature is controlled within a temperature range of 105°C to 110°C.

4. The method for evaluating the service life of a carbon sleeve of a silicon steel continuous annealing furnace according to claim 1, characterized in that: The jacket of the pipeline for nitrogen and hydrogen is equipped with an electric heating system.

5. The method for evaluating the service life of a carbon sleeve of a silicon steel continuous annealing furnace according to claim 1, characterized in that: In the step 2, the carbon jacket sample is placed in the furnace, and after the furnace door is closed, dry high-purity nitrogen is introduced for 10 to 20 minutes at a nitrogen flow rate of 20 to 30 L / min.

6. The method for evaluating the service life of a carbon sleeve of a silicon steel continuous annealing furnace according to claim 1, characterized in that: In step 3, the maximum temperature of the heating curve is set to 1150° C. to 1250° C.; a mixed gas of dry high-purity nitrogen and hydrogen is introduced, and the gas flow rate is 25 L / min to 35 L / min.

7. The method for evaluating the service life of a carbon sleeve of a silicon steel continuous annealing furnace according to claim 1, characterized in that: In step 4, the temperature T1 is set to 1150°C to 1250°C.

8. The method for evaluating the service life of a carbon sleeve of a silicon steel continuous annealing furnace according to claim 1, characterized in that: In the step 5, after keeping warm for 2.5 to 3.5 hours, the dry ball valve is opened to introduce dry gas, and the wet ball valve is closed to stop introducing the mixed gas of wet nitrogen and hydrogen.

9. The method for evaluating the service life of a carbon sleeve of a silicon steel continuous annealing furnace according to claim 1, characterized in that: In step 6, the temperature T2 is set to 40°C.

10. The method for evaluating the service life of a carbon sleeve of a silicon steel continuous annealing furnace according to claim 1, characterized in that: The formula for calculating weight loss rate is: Weight loss rate (SZL) = 100% × (W0-W1) / W0, where W0 is the mass of the sample after drying, and W1 is the mass of the sample after cooling after the antioxidant test.

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