Refractory resistance to hot metal cold shrinkage stress testing device and method

Abstract

The application discloses a refractory anti-molten iron cold shrinkage stress testing device and method, and belongs to the technical field of iron making. The device comprises a testing support, a graphite crucible, a display, a temperature measuring meter and at least two tension testing components. The tension testing components are installed on the testing support, the lower ends of which are located in the graphite crucible and used for installing refractory samples. The predetermined distance between the lower end of each tension testing component and the bottom of the graphite crucible is sequentially increased by a predetermined height. The tension testing components detect the tension on the lower end thereof, and the display displays the tension. The temperature measuring meter measures the temperature of the molten iron. During the test, the number of the refractory samples immersed in the molten iron is sequentially increased, and the tension and the temperature of each sample are recorded synchronously with the cooling of the molten iron, so that the average tensile strength, the stress starting temperature, the stress early warning temperature and the suitable use temperature range of the refractory can be determined. The application can quantitatively evaluate the tensile stress formed on the refractory due to the solidification shrinkage of the molten iron, and provides a basis for the selection and temperature control of the refractory of the blast furnace hearth.

Description

Technical Field

[0001] This invention relates to the field of measuring the magnitude of the condensation stress of refractory materials in blast furnace hearths, and particularly to a device and method for testing the condensation stress of refractory materials. Background Technology

[0002] The blast furnace hearth is a crucial component containing molten iron and slag. Its lining, in direct contact with the molten iron, is constructed of refractory material (carbon bricks). Once in use, carbon bricks are subjected to prolonged erosion and scouring by the high-temperature flowing slag and iron. Furthermore, a thick layer of solidified iron adheres to their hot surfaces. Since the coefficient of thermal expansion of iron is approximately 2.4 times that of carbon bricks, the hot surfaces of the carbon bricks repeatedly experience stress from the contraction and expansion of the solidified iron layer as the furnace conditions fluctuate. This stress gradually forms on the hot surfaces, eventually leading to carbon brick spalling, erosion, and even hearth burn-through. Therefore, the ability of the carbon brick hot surfaces to resist the contraction and expansion stresses of solidified iron is of great significance for studying and controlling the hearth's resistance to molten iron damage and extending its service life.

[0003] Currently, existing technologies for the detection and monitoring of blast furnace hearths and linings mainly focus on monitoring the location and thickness of lining erosion (ablation), as detailed below: For example, existing technology provides a method for measuring the temperature of blast furnace hearth brick lining. During the construction of the blast furnace hearth brick lining, armored thermocouples are embedded on the same horizontal plane as the centerline of the taphole, along the outer side of the hearth brick lining. An automatic temperature recorder continuously records temperature changes at this location, allowing for timely maintenance measures to prevent hearth burn-through accidents. However, this method primarily predicts hearth erosion through thermocouple temperature measurement. The erosion site in a blast furnace is generally located 1.0 to 2.0 meters below the taphole, and the thermocouples are susceptible to severe corrosion from hearth gas leakage and dust, resulting in poor measurement accuracy and making it difficult to achieve ideal prediction results for hearth erosion.

[0004] Existing technology also discloses a non-destructive testing method for refractory materials inside a hot blast stove, which includes: cleaning the outer surface of the hot blast stove shell; offline calibration of the wave velocity of the excited shock wave; determining and numbering test points, dividing the test area on the outer surface of the furnace shell into test points; waveform detection, i.e., placing a detector at the test point, selecting two excitation points at a longitudinal distance of 0.2m to 0.5m from the test point, continuously striking the excitation points with the excitation device and collecting the reflected response waveform; performing data processing, and creating a cross-sectional diagram with the test point position as the abscissa and the calculated refractory thickness as the ordinate to determine the refractory damage status in each area of ​​the furnace. This method does not require opening the furnace shell or erecting scaffolding inside the furnace, and is relatively safe, efficient, and economical. However, it can only detect the refractory thickness (damage status) and cannot reflect the stress exerted on the refractory by molten iron.

[0005] Existing technology also discloses a blast furnace lining erosion monitoring device, which consists of optical fiber, a fiber-insulated flexible tube, a light generator, and a light receiver. During monitoring, a fiber-insulated flexible tube (i.e., a detector) fitted with an optical fiber is embedded in each brick joint of each layer in the hearth and furnace bottom to be monitored. When the light receiver does not receive a light signal, the specific location of the erosion can be detected. Although this device has strong anti-electromagnetic interference capability and a simple and reliable structure, it requires pre-embedding optical fibers in the hearth and judging the hearth erosion based on the presence or absence of a signal from the optical fibers. This has problems such as damaging the integrity of the brick lining, easy damage to the detection element, and difficulty in maintenance.

[0006] The prior art also discloses a method for measuring the erosion thickness of a blast furnace lining, which includes: collecting data from temperature and flow sensors on the cooling wall, inputting the data into a computer via an isolation template and adapter, and reading the outlet water temperature of each cooling wall from a database of cooling wall water temperature difference and heat flux intensity. And the heat flux intensity Q; the temperature of the hot surface of the cooling wall is determined sequentially according to Fourier's formula. ( ), charcoal brick cold surface temperature ( and the temperature of the hot surface of the charcoal brick ( Based on this, the location of the 1150℃ iron solidification erosion line in the hearth was determined, and the erosion curve of the hearth at 1150℃ was finally plotted. This method infers the temperature of each layer of the hearth refractory material by using the temperature difference of the cooling wall water and the heat flux intensity. However, because the temperature difference of the cooling wall is small, and the temperature difference between each cooling wall is also small, it is difficult to effectively measure the erosion of the hearth in actual use.

[0007] In summary, most existing technologies focus on online monitoring of the location and thickness of furnace lining erosion (ablation) during blast furnace operation. These technologies generally suffer from low measurement accuracy, susceptibility of detection elements to corrosion or damage, the need for pre-embedded elements which compromises the integrity of the brick lining, and difficulties in maintenance. More importantly, none of these technologies can measure and evaluate the shrinkage and expansion stresses exerted on the refractory materials (carbon bricks) during the thermal expansion and contraction of molten iron (solidified iron layer). Therefore, they cannot effectively evaluate the ability of blast furnace carbon bricks to resist damage from molten iron shrinkage stress, making it difficult to provide direct guidance for improving the performance and optimizing the structure of blast furnace refractory materials.

[0008] Therefore, how to provide a test device and method for measuring and evaluating the shrinkage and expansion stresses exerted on refractory materials (carbon bricks) during the thermal expansion and contraction of molten iron (solidified iron layer) is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] The purpose of this invention is to provide a device and method for testing the resistance of refractory materials to molten iron shrinkage stress, so as to solve the problem that existing devices and methods for testing the resistance of refractory materials to molten iron shrinkage stress cannot measure and evaluate the shrinkage and expansion stresses exerted on refractory materials (carbon bricks) during the thermal expansion and contraction of molten iron (solidified iron layer).

[0010] To address the aforementioned technical problems, this invention provides a refractory resistance to molten iron shrinkage stress testing device, comprising a test bracket, a graphite crucible, a display, a temperature measuring meter, and at least two tensile testing components. The graphite crucible is used to hold molten iron. The tensile testing components are mounted on the test bracket, located above the graphite crucible, with their lower ends inside the graphite crucible. The lower end of the tensile testing components is used to mount refractory samples. The distance between the lower end of the tensile testing components and the bottom of the graphite crucible is a predetermined distance, and multiple predetermined distances increase sequentially with a predetermined height. The tensile testing components are used to detect the tensile force received by the lower end of the tensile testing components. The display is used to display the tensile force received by the lower end of each tensile testing component. The temperature measuring meter is used to measure the temperature of the molten iron inside the graphite crucible.

[0011] Optionally, the tensile testing assembly includes a tensile probe, a pull rod, and a sample clamp. The tensile probe is mounted on the test bracket, the pull rod connects the tensile probe and the sample clamp, and the sample clamp is used to hold the refractory sample. The height of the sample clamp is adjustable.

[0012] Optionally, it also includes a tension seat, through which the tension probe is mounted on the test bracket, and the tension probe is evenly distributed on the tension seat along the circumference.

[0013] Optionally, the temperature measuring instrument is an infrared temperature probe.

[0014] Optionally, the infrared temperature probe is located on the tension seat and at the center of the plurality of tension probes.

[0015] Optionally, a test base for supporting the graphite crucible may also be included.

[0016] Optionally, the test base includes a fixing sleeve, a fixing base, and a height adjustment component. The height adjustment component supports the fixing base and adjusts the height of the fixing base. The fixing sleeve is fixed above the fixing base and supports the graphite crucible.

[0017] Optionally, there may be multiple displays, each corresponding to a tensile testing component, for displaying the tensile force applied to the lower end of a single tensile testing component.

[0018] The present invention also provides a method for testing the resistance to molten iron cooling shrinkage stress of refractory materials using the above-described refractory material resistance to molten iron cooling shrinkage stress test device, wherein the refractory material sample comprises: The refractories include a cylindrical main body and at least two annular layers, the annular layers being sleeved on and integrally connected to the cylindrical main body. Multiple annular layers are distributed sequentially from bottom to top on the cylindrical main body, with the spacing between adjacent annular layers equal to a predetermined height. The method for testing the resistance of refractory materials to molten iron shrinkage stress includes: Multiple refractory samples are respectively installed on multiple tensile testing components of the testing device, and one refractory sample is installed on each tensile testing component; Multiple refractory samples are immersed in molten iron, and the number of annular layers of refractory samples immersed in molten iron increases sequentially starting from one layer. The tensile force measured by the tensile testing component is reset to zero, so that the tensile force displayed on the monitor is zero; Turn on the temperature measuring instrument and record the test data of how the tensile force measured by each tensile test component changes with temperature; The measured test data are analyzed to obtain the tensile properties of the refractory material under furnace hearth temperature fluctuations and the suitable operating temperature range.

[0019] Optionally, analyzing the measured test data to obtain the tensile properties and suitable operating temperature range of the refractory material under furnace hearth temperature fluctuations includes: dividing the tensile force measured by each tensile testing component at each temperature by the cross-sectional area of ​​the cylindrical main body to obtain the tensile strength of each refractory sample at each temperature; taking the average tensile strength of the broken refractory sample as the average tensile strength of the refractory material; for each refractory sample, determining the temperature at which the tensile strength of the refractory sample begins to be greater than zero as the stress initiation temperature, and determining the temperature at which the tensile strength of the refractory sample reaches 50% of the average tensile strength as the stress warning temperature; and comparing the stress warning temperature with the stress... The temperature range between the initial temperatures is defined as the stress formation temperature range; the temperature at which the refractory sample breaks is defined as the limit service temperature of the refractory at the corresponding immersion depth; the number of annular layers of the refractory sample immersed in the molten iron characterizes the depth of molten iron penetration of the refractory, obtaining the correspondence between immersion depth, tensile strength and temperature, as well as the stress formation temperature range and the limit service temperature at each immersion depth, which serve as the tensile properties of the refractory when the hearth temperature fluctuates. The temperature range above the stress warning temperature is defined as the suitable service temperature range of the refractory, and the temperature range below the stress warning temperature is defined as the temperature range where repeated fluctuations of the refractory need to be avoided.

[0020] The present invention provides a device and method for testing the resistance of refractory materials to molten iron cooling shrinkage stress, which has the following beneficial effects: First, by using multiple tensile testing components with progressively increasing immersion depths, multiple refractory samples are simultaneously subjected to shrinkage stress in the same graphite crucible and the same batch of molten iron, and the tensile force and temperature are measured simultaneously. A single test can obtain the corresponding law of tensile stress on the refractory at different immersion depths as a function of temperature. Since each refractory sample is in the same batch of molten iron and has a consistent temperature history, the measurement results are highly comparable to each other. This allows for the quantitative evaluation of the tensile stress formed on the refractory by the solidification shrinkage of molten iron, overcoming the shortcomings of existing technologies that can only monitor the location and thickness of furnace lining erosion but cannot measure and evaluate the stress exerted on the refractory by the shrinkage of molten iron.

[0021] Secondly, the tensile probe, pull rod, and sample clamp form a simple and reliable force transmission and measurement path. The tensile probe directly detects the tensile force on the lower end of the refractory sample, and the measurement is accurate. The height of the sample clamp is adjustable, which makes it easy to set the predetermined distance of each tensile testing component, thereby conveniently realizing the sequential increase of the immersion depth of multiple refractory samples.

[0022] Furthermore, the tensile probes are evenly distributed around the circumference on the tensile base, ensuring that multiple refractory samples from the same batch of molten iron are subjected to symmetrical forces and have the same temperature field, further improving the comparability of measurement results for samples at different immersion depths; the tensile base allows for the integrated installation of multiple tensile probes, resulting in a compact structure.

[0023] Furthermore, the temperature measuring instrument uses an infrared temperature probe to measure the temperature of molten iron in a non-contact manner, avoiding the corrosion of the temperature measuring element by the molten iron. It has accurate temperature measurement and a long service life, overcoming the shortcomings of existing technologies where thermocouples are easily corroded by furnace hearth gas leakage and dust, and have poor measurement accuracy.

[0024] Then, by adjusting the height of the fixed base using the height adjustment component, the graphite crucible can be raised and lowered as a whole, and the immersion depth of each refractory sample can be precisely set; the fixed sleeve forms a rigid support for the graphite crucible, ensuring that the relative position between the graphite crucible and the tension seat remains stable during the test. Attached Figure Description

[0025] Figure 1 This is a side view of the tensile testing component and tensile seat in the refractory material anti-cooling shrinkage stress testing device of the present invention; Figure 2 This is a top view of the tension seat in the refractory material resistance to water-cooled shrinkage stress testing device of the present invention; Figure 3 This is a schematic diagram of the overall structure of the refractory material resistance to iron water cooling shrinkage stress testing device of the present invention; Figure 4 This is a schematic diagram of the structure of the refractory material sample of the present invention.

[0026] Explanation of reference numerals in the attached figures: 100-Test bracket; 200-Graphite crucible; 300-Display; 400-Temperature meter; 500-Tension test assembly; 520-Pull rod; 530-Sample clamp; 600-Tension seat; 710-Fixing sleeve; 720-Fixing base; 730-Height adjustment component; 800-Refractory insulation material; 900-Refractory sample; 910-Cylindrical main body; 920-Annular sheet; 930-Molten iron. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] refer to Figure 1 , Figure 2 , Figure 3 and Figure 4 , Figure 1 This is a side view of the tensile testing component 500 and the tensile support 600 in the refractory material resistance to molten iron shrinkage stress testing device of the present invention. Figure 2 This is a top view schematic diagram of the tension seat 600 in the refractory material resistance to molten iron cooling shrinkage stress testing device of the present invention. Figure 3 This is a schematic diagram of the overall structure of the refractory material resistance to molten iron cooling shrinkage stress testing device of the present invention. Figure 4This is a schematic diagram of the structure of the refractory sample 900 of the present invention. This embodiment provides a refractory resistance to molten iron shrinkage stress testing device, which includes a test bracket 100, a graphite crucible 200, a display 300, a temperature measuring meter 400, and at least two tensile testing components 500. The graphite crucible 200 is used to hold molten iron 930; each tensile testing component 500 is mounted on the test bracket 100, located above the graphite crucible 200, with its lower end inside the graphite crucible 200; the lower end of each tensile testing component 500 is used to mount the refractory sample 900; the distance between the lower end of each tensile testing component 500 and the bottom of the graphite crucible 200 is a predetermined distance, and multiple predetermined distances increase sequentially with a predetermined height, thereby increasing the depth to which the refractory sample 900 mounted at the lower end of each tensile testing component 500 is immersed in the molten iron 930. Each tensile testing assembly 500 is used to detect the tensile force applied to its lower end. The display 300 is used to display the tensile force applied to the lower end of each tensile testing assembly 500. The temperature measuring meter 400 is used to measure the temperature of the molten iron 930 in the graphite crucible 200. In use, the refractory sample 900 is installed at the lower end of each tensile testing assembly 500 and immersed in the molten iron 930. During the cooling and solidification process, the molten iron 930 shrinks, and its hot surface solidified iron layer grips the refractory sample 900 and applies a downward tensile force to the refractory sample 900. This tensile force is detected by the tensile testing assembly 500 and displayed by the display 300. At the same time, the temperature of the molten iron 930 is measured by the temperature measuring meter 400, thus obtaining data on the change of tensile force on the refractory sample 900 with temperature.

[0029] By using multiple tensile testing components 500 with progressively increasing immersion depths, multiple refractory samples 900 are simultaneously subjected to shrinkage stress and their tensile force and temperature are measured in the same graphite crucible 200 and the same batch of molten iron 930. A single test can obtain the corresponding law of tensile stress on the refractory material at different immersion depths as a function of temperature. Since each refractory sample 900 is in the same batch of molten iron 930 and has a consistent temperature history, their measurement results are highly comparable. This allows for the quantitative evaluation of the tensile stress on the refractory material caused by the solidification shrinkage of molten iron 930, overcoming the shortcomings of existing technologies that can only monitor the location and thickness of furnace lining erosion but cannot measure and evaluate the stress exerted on the refractory material by the shrinkage of molten iron 930.

[0030] In this embodiment, the tensile strength refers to the ratio of the tensile force on the lower end of the tensile testing component 500 to the cross-sectional area of ​​the stressed portion of the refractory sample 900. Specifically, it is the stress value obtained by dividing the measured tensile force by the cross-sectional area of ​​the broken portion (cylindrical main body 910) of the refractory sample 900, expressed in megapascals (MPa). The display 300 can directly display the tensile force. The predetermined distance refers to the vertical distance from the lower end of the tensile testing component 500 to the bottom of the graphite crucible 200. The smaller the predetermined distance, the greater the depth to which the refractory sample 900 at the lower end of the tensile testing component 500 is immersed in the molten iron 930. The predetermined height refers to the difference between the predetermined distances corresponding to two adjacent tensile testing components 500, and its value is equal to the spacing between two adjacent annular layers 920 on the refractory sample 900, thereby ensuring that the number of annular layers 920 immersed in the molten iron 930 by two adjacent refractory samples 900 is exactly one less. The number of the at least two tensile test components 500 can be determined by the maximum number of layers that need to be immersed, and is usually consistent with the number of annular layers 920 on the refractory sample 900.

[0031] Based on the above-mentioned device, each tensile testing component 500 includes a tensile probe, a pull rod 520, and a sample clamp 530. The tensile probe is mounted on the test bracket 100; one end of the pull rod 520 is connected to the tensile probe, and the other end is connected to the sample clamp 530; the sample clamp 530 is used to hold the refractory sample 900, and the height of the sample clamp 530 is adjustable. In use, the refractory sample 900 is clamped on the sample clamp 530, and the tensile force it receives is transmitted to the tensile probe through the pull rod 520, which detects and outputs the force to the display 300; by adjusting the height of the sample clamp 530, the predetermined distance from the lower end of the refractory sample 900 to the bottom of the graphite crucible 200 can be changed, thereby setting the depth at which the refractory sample 900 is immersed in the molten iron 930.

[0032] The tensile probe, pull rod 520 and sample clamp 530 constitute a simple and reliable force transmission and measurement path. The tensile probe directly detects the tensile force on the lower end of the refractory sample 900, and the measurement is accurate. The height of the sample clamp 530 is adjustable, so that the predetermined distance of each tensile testing component 500 can be set separately, thereby conveniently realizing the sequential increase of the immersion depth of multiple refractory samples 900.

[0033] The tensile probe can be a high-temperature tensile sensor with a range of 0 to 500 N and an accuracy of ±0.5% of full scale. Its range covers the maximum tensile force (approximately 235 N) experienced by the refractory specimen 900 before it breaks during the test. The pull rod 520 can be made of heat-resistant alloy or corundum, with a diameter of 8 to 12 mm. A heat-insulating section is provided near the tensile probe to ensure that the temperature transmitted to the tensile probe does not exceed 80°C, thus preventing high temperatures from affecting the measurement accuracy of the tensile probe. The height of the sample clamp 530 is adjustable, meaning that the installation position of the sample clamp 530 on the pull rod 520 can be adjusted along the axial direction of the pull rod 520 to change the height of the lower end of the refractory specimen 900. It should be noted that those skilled in the art should understand that "the pull rod 520 connects the tensile probe and the sample clamp 530" means that the pull rod 520 connects the tensile probe and the sample clamp 530 as a force transmission path.

[0034] Furthermore, the sample clamp 530 is threadedly connected to the pull rod 520. Specifically, an external or internal thread is provided at the lower end of the pull rod 520, and a matching thread is provided on the sample clamp 530. The axial position of the sample clamp 530 on the pull rod 520 is adjusted by the depth of engagement. The threaded connection between the sample clamp 530 and the pull rod 520 makes the height adjustment of the sample clamp 530 convenient and precise, and facilitates the installation and replacement of the refractory sample 900.

[0035] When using a threaded connection, the height of the sample clamp 530 can be continuously and precisely adjusted by rotating it. The adjustment amount can be calculated by the pitch, which makes it easy to accurately set the height difference between adjacent sample clamps 530 to be equal to the spacing of the annular layer 920. At the same time, the threaded connection facilitates the assembly, disassembly and replacement of the sample clamp 530 and the pull rod 520.

[0036] Furthermore, the device also includes a tension seat 600, through which tension probes are mounted on the test bracket 100, and multiple tension probes are evenly distributed along the circumference of the tension seat 600. The tension seat 600 is fixed to the upper part of the test bracket 100, and the multiple tension probes are arranged at equal angular intervals along the same circumference with the central axis of the tension seat 600 as the center. Each tension probe is connected to a pull rod 520, a sample clamp 530, and a refractory sample 900 below it.

[0037] The tensile probes are evenly distributed around the circumference on the tensile base 600, ensuring that multiple refractory samples 900 in the same batch of molten iron 930 are subjected to symmetrical forces and have the same temperature field, further improving the comparability of measurement results for samples at different immersion depths; the tensile base 600 integrates and installs multiple tensile probes, resulting in a compact structure.

[0038] Multiple tensile probes are evenly distributed along the circumference, so that the corresponding multiple refractory samples 900 are symmetrically arranged along the same circumference within the graphite crucible 200. The distances from each refractory sample 900 to the crucible center and the crucible wall are equal, thus placing them in a basically uniform molten iron 930 temperature field. The tensile base 600 serves as a common mounting base for multiple tensile probes, integrating multiple measurement components into one unit, resulting in a compact structure and convenient installation.

[0039] Furthermore, the temperature measuring instrument 400 is an infrared temperature probe 400. The infrared temperature probe 400 measures the temperature of the molten iron 930 in the graphite crucible 200 in a non-contact manner, outputting and recording the measured temperature of the molten iron 930. The use of an infrared temperature probe 400 in the temperature measuring instrument 400 for non-contact measurement of the molten iron 930 temperature avoids corrosion of the temperature sensing element by the molten iron 930, resulting in accurate temperature measurement and a long service life. This overcomes the shortcomings of existing technologies where thermocouples are susceptible to corrosion from furnace hearth gas leakage and dust, and have poor measurement accuracy.

[0040] The infrared temperature probe 400 has a range of 400 to 1800℃ and an accuracy of ±5℃. The emissivity can be set to 0.85 during temperature measurement. The infrared temperature measurement method is aligned with the surface of the molten iron 930, eliminating the need to insert the temperature measuring element into the molten iron 930 and avoiding corrosion of the temperature measuring element by the high temperature of the molten iron 930.

[0041] The infrared temperature probe 400 is located on the tension base 600 and at the center of multiple tension probes. That is, the infrared temperature probe 400 is set at the center of the tension base 600, and multiple tension probes are evenly distributed around the infrared temperature probe 400 along the circumference.

[0042] The infrared temperature probe 400 is located at the center of multiple tensile probes, so that the temperature of the molten iron 930 measured by it is representative of all refractory samples 900. This ensures that the tensile data measured by each tensile testing component 500 can be recorded synchronously under the same temperature reference, thereby accurately establishing the correspondence between tensile force and temperature.

[0043] The infrared temperature probe 400 is located at the center of multiple tensile probes, with its temperature measurement direction facing downwards and directly towards the central area of ​​the molten iron 930 liquid surface in the graphite crucible 200. Since multiple refractory samples 900 are symmetrically arranged with the infrared temperature probe 400 as the center, the temperature of the molten iron 930 measured by the infrared temperature probe 400 is representative of each refractory sample 900 and can be used as a common temperature reference for the tensile data measured by each tensile testing component 500.

[0044] Furthermore, the device also includes a test base for supporting the graphite crucible 200. The test base is positioned below the graphite crucible 200, supporting and bolstering it. The test base provides stable support for the graphite crucible 200, preventing displacement of the graphite crucible 200 during the test and thus ensuring the accuracy of the measurement data.

[0045] The test base provides stable support for the graphite crucible 200 below, keeping the graphite crucible 200 in a fixed position during the test. Since the molten iron 930 will generate a reaction force on the graphite crucible 200 when it cools and shrinks, if the crucible is displaced, the immersion depth of the refractory sample 900 will change, resulting in distorted measurement data. The test base is used to avoid such displacement.

[0046] Furthermore, the test base includes a fixing sleeve 710, a fixing base 720, and a height adjustment component 730. The height adjustment component 730 supports the fixing base 720 and adjusts its height; the fixing sleeve 710 is fixed above the fixing base 720 and supports the graphite crucible 200. In use, the graphite crucible 200 is placed inside and supported by the fixing sleeve 710. By adjusting the height adjustment component 730, the fixing base 720, together with the fixing sleeve 710 and the graphite crucible 200, is raised or lowered as a whole, thereby adjusting the height of the graphite crucible 200 relative to the lower end of each refractory sample 900, and thus setting the immersion depth of each refractory sample 900. By adjusting the height of the fixed base 720 through the height adjustment component 730, the graphite crucible 200 can be raised and lowered as a whole, and the immersion depth of each refractory sample 900 can be precisely set; the fixed sleeve 710 forms a rigid support for the graphite crucible 200, ensuring that the relative position between the graphite crucible 200 and the tension seat 600 remains stable during the test.

[0047] When the height adjustment component 730 is adjusted, the fixed base 720 rises and falls accordingly, driving the fixed sleeve 710 and the graphite crucible 200 therein to rise and fall together. Since the height of the lower end of each tensile testing component 500 has been set by the sample clamp 530, raising and lowering the graphite crucible 200 can make the shallowest immersion refractory sample 900 just immerse in one annular layer 920, and the remaining refractory samples 900 will be immersed in one more layer according to the predetermined height, so that the number of immersion layers of multiple refractory samples 900 increases sequentially from one layer.

[0048] Furthermore, a refractory heat-insulating material 800 is provided inside the fixed sleeve 710, between the upper surface of the fixed base 720 and the bottom of the graphite crucible 200. That is, the refractory heat-insulating material 800 is filled or laid in the inner cavity of the fixed sleeve 710, between the upper surface of the fixed base 720 and the bottom of the graphite crucible 200, with the graphite crucible 200 resting on this refractory heat-insulating material 800. Providing the refractory heat-insulating material 800 between the fixed base 720 and the bottom of the graphite crucible 200 reduces heat dissipation at the bottom of the crucible, facilitating the cooling of the molten iron 930 at a near-actual rate, and also catches the molten iron 930 in the event of crucible breakage, preventing damage to the device and preventing safety accidents.

[0049] The refractory insulation material 800 can be made of mullite fiber felt, with a thickness of 20 to 30 mm. This refractory insulation material 800 reduces heat loss from the bottom of the graphite crucible 200 to the fixed base 720 and slows down the temperature drop of the molten iron 930. On the other hand, when the graphite crucible 200 breaks at high temperature and the molten iron 930 leaks out, it can catch the leaked molten iron 930 and prevent the molten iron 930 from directly contacting and burning the fixed base 720 and other device components.

[0050] Furthermore, the number of height adjustment components 730 is at least three. At least three height adjustment components 730 are spaced apart below the fixed base 720, collectively supporting the fixed base 720. Using at least three height adjustment components 730 to support the fixed base 720 ensures that the fixed base 720 and the graphite crucible 200 on it are locked in place, maintaining a horizontal and stable position, thus preventing the crucible from tilting during the test and affecting the accuracy of the immersion depth of each refractory sample 900.

[0051] The number of height adjustment components 730 is at least three. Three or more support points can determine and lock the plane on which the fixed base 720 is located. Each height adjustment component 730 can adopt a screw structure with an adjustment stroke of 0 to 50 mm and an adjustment accuracy of 1 mm. The fixed base 720 can be kept horizontal by finely adjusting each height adjustment component 730.

[0052] Furthermore, the fixing sleeve 710 and the fixing base 720 are connected by bolts. That is, bolts are installed between the bottom of the fixing sleeve 710 and the fixing base 720 to secure the two together. The bolted connection between the fixing sleeve 710 and the fixing base 720 is firm and reliable, and easy to install and disassemble, facilitating the cleaning and replacement of the graphite crucible 200.

[0053] The fixed sleeve 710 and the fixed base 720 are connected by bolts, which is reliable and easy to install and disassemble. After the test, the bolts can be removed and the fixed sleeve 710 can be removed to clean the crucible or replace the graphite crucible 200.

[0054] Furthermore, the height adjustment components 730 are mounted on the test bracket 100. Specifically, the lower ends of each height adjustment component 730 are fixed to the test bracket 100, which supports the height adjustment components 730, their fixed bases 720, fixed sleeves 710, and the graphite crucible 200. The mounting of the height adjustment components 730 on the test bracket 100 ensures a rigid connection between the graphite crucible 200 and the tension seat 600 on the same test bracket 100, preventing measurement distortion caused by relative displacement and further guaranteeing the accuracy of the measurement data.

[0055] The height adjustment component 730 is installed on the test bracket 100, so that the graphite crucible 200 and the tension seat 600 are rigidly connected as a whole through the same test bracket 100; since the tension test component 500 is also installed on the test bracket 100, the two share the same bracket reference, which can prevent relative displacement between the graphite crucible 200 and the tension seat 600.

[0056] Furthermore, the test bracket 100 is a cuboid frame. Specifically, the test bracket 100 adopts a cuboid frame structure, with its upper crossbeam used to mount the tension seat 600 and its bottom used to mount the height adjustment component 730. The cuboid frame of the test bracket 100 provides structural stability, simple processing, and facilitates the installation of the tension seat 600 and the height adjustment component 730, providing a stable common mounting reference for all components.

[0057] The test bracket 100 adopts a rectangular frame, which is simple and stable. It is easy to install the tension seat 600 on the upper part and the height adjustment component 730 on the bottom, and provides vertical guidance space for the lifting and lowering of the graphite crucible 200.

[0058] Furthermore, there are multiple displays 300, each corresponding to one of the multiple tensile testing components 500. Each display 300 displays the tensile force acting on the lower end of a single tensile testing component 500. That is, each tensile testing component 500 is equipped with an independent display 300, and each display 300 displays the tensile force measured by its corresponding tensile testing component 500 in real time. The one-to-one correspondence between multiple displays 300 and tensile testing components 500 allows for simultaneous reading of the tensile force acting on each refractory sample 900, facilitating a direct comparison of the stress conditions of samples at different immersion depths and improving the efficiency and accuracy of test data reading and recording.

[0059] The number of displays 300 is the same as the number of tensile testing components 500 and corresponds one-to-one. During the test, each display 300 displays the tensile force on the corresponding refractory sample 900. Since the immersion depth of each refractory sample 900 is different, the magnitude of the tensile force on the refractory samples 900 at the same temperature can be read and compared intuitively through multiple displays 300.

[0060] This embodiment also provides a method for testing the resistance to molten iron cooling shrinkage stress of a refractory sample 900 using the aforementioned refractory ... The first step is to install multiple refractory samples 900 onto multiple tensile testing components 500 of the testing device, with one refractory sample 900 installed on each tensile testing component 500. The second step is to immerse multiple refractory samples 900 in molten iron 930, and the number of annular sheets 920 immersed in the molten iron 930 for multiple refractory samples 900 increases sequentially from one sheet. The third step is to zero the tensile force measured by the tensile testing component 500, so that the tensile force displayed on the monitor 300 is zero; Fourth step, turn on the temperature measuring meter 400 and record the test data of how the tensile force measured by each tensile test component 500 changes with temperature; The fifth step is to analyze the measured test data to obtain the tensile properties of the refractory material under furnace hearth temperature fluctuations and its suitable operating temperature range.

[0061] The cylindrical main body 910 on the refractory sample 900 is the part that is subjected to force and broken by tension. The annular sheet 920 is used to be held by the solidified iron layer to withstand and transmit the tensile force generated by the cold contraction of the molten iron 930. The annular sheets 920 are distributed sequentially from bottom to top with the adjacent spacing equal to the predetermined height. In conjunction with the predetermined distance of each tensile test component 500, the predetermined height increases sequentially, so that the number of annular sheets 920 immersed in the molten iron 930 by two adjacent refractory samples 900 is exactly one sheet apart. Therefore, the immersion depth of multiple refractory samples 900 corresponds to the immersion depth that increases sequentially from one sheet.

[0062] The third step is to zero the reading because the refractory sample 900 will be subject to the buoyancy of the molten iron 930 after being immersed in it. If the reading is not zeroed, the buoyancy will be added to the tensile force measured later. Therefore, the reading must be zeroed after the sample is immersed and before the data is recorded so that the recorded value starts from zero.

[0063] In the fourth step, as the molten iron 930 cools naturally and its temperature decreases, the solidified iron layer gradually forms and shrinks. Gradually increasing tensile force is applied to each refractory sample 900. The temperature measuring instrument 400 and each tensile testing component 500 synchronously record the temperature and the corresponding tensile force (or tensile strength). The temperature recording interval can be once every 5 to 10°C temperature drop, and the recorded temperature range can be from 1200°C to 800°C to cover the solidification range of the molten iron 930 and the working temperature range of the hot surface of the refractory material in the blast furnace hearth.

[0064] This method uses a refractory sample 900 with an integrally formed cylindrical main body 910 and multiple annular layers 920 to simulate the multi-layered structure formed after the hot surface of the refractory in the blast furnace hearth is penetrated by molten iron 930. By sequentially increasing the number of layers of multiple refractory samples 900 immersed in molten iron 930 and simultaneously and continuously recording the tensile force and temperature of each sample during natural cooling, complete data on the change of tensile force of the refractory with temperature at different immersion depths can be obtained in a single test. Zeroing before measurement eliminates the influence of the buoyancy of molten iron 930, making the measured tensile force data accurate and reliable.

[0065] Furthermore, the fifth step involves analyzing the measured test data to obtain the tensile properties of the refractory material under furnace hearth temperature fluctuations and its suitable operating temperature range, specifically including: (1) Divide the tensile force measured by each tensile test component 500 at each temperature by the cross-sectional area of ​​the cylindrical main body 910 to obtain the tensile strength of each refractory sample 900 at each temperature. (2) The average tensile strength of the refractory specimen 900 at the time of fracture is taken as the average tensile strength of the refractory. (3) For each refractory specimen 900, the temperature at which the tensile strength of the refractory specimen 900 begins to be greater than zero is determined as the stress initiation temperature, the temperature at which the tensile strength of the refractory specimen 900 reaches 50% of the average tensile strength is determined as the stress warning temperature, and the temperature range between the stress warning temperature and the stress initiation temperature is determined as the stress formation temperature range. (4) The temperature at which the refractory specimen 900 breaks is determined as the limit service temperature of the refractory at the immersion depth corresponding to the refractory specimen 900. (5) The number of annular layers 920 in which the refractory sample 900 is immersed in molten iron 930 is used to characterize the depth of penetration of the refractory into molten iron 930. The corresponding relationship between penetration depth, tensile strength and temperature, as well as the stress formation temperature range and limit service temperature at each penetration depth are obtained as the tensile properties of the refractory when the hearth temperature fluctuates. The temperature range above the stress warning temperature is taken as the suitable service temperature range of the refractory, and the temperature range below the stress warning temperature is taken as the temperature range that the refractory needs to avoid repeated fluctuations.

[0066] In step (1), the cross-sectional area of ​​the cylindrical main body 910 is calculated based on its diameter. For example, when the diameter of the cylindrical main body 910 is 10 mm, its cross-sectional area is approximately 78.5 square millimeters. The tensile force (in Newtons) measured at each temperature is divided by this cross-sectional area (in square millimeters) to obtain the tensile strength in megapascals. In step (2), the tensile strength of the broken refractory sample 900 at the moment of breakage is the tensile strength of the sample. The average tensile strength of each broken sample is taken as the average tensile strength of the refractory. When the number of broken samples in the test is small, cylindrical samples of the same batch of refractory and the same specifications can be taken on a tensile testing machine to supplement the tensile strength measurement, and the average value is taken together. In step (3), 50% of the average tensile strength is taken as the criterion for stress warning because the refractory material has a high resistance to fatigue crack propagation under cyclic tensile stress below 50% of its tensile strength. Once the tensile stress exceeds this value, repeated loading will significantly accelerate the initiation and propagation of hot surface stress cracks in the refractory material. In step (5), the more annular layers 920 are immersed, the greater the depth of penetration of the refractory material by molten iron 930.

[0067] This method converts tensile force into tensile strength, determines the average tensile strength, stress initiation temperature, stress warning temperature, and ultimate service temperature, and characterizes the penetration depth by using the number of annular 920-degree immersion layers. Ultimately, it obtains the correspondence between penetration depth, tensile strength, and temperature, thereby quantitatively providing the tensile properties of refractory materials under hearth temperature fluctuations, the suitable service temperature range, and the temperature intervals where repeated fluctuations should be avoided. Based on this, the resistance to molten iron shrinkage stress of different refractory materials can be compared and selected, guiding the blast furnace to rationally control hearth temperature fluctuations, reduce refractory material damage, and extend hearth service life.

[0068] To further illustrate the scheme and effect of this embodiment, taking a carbon brick A for a blast furnace as an example, the above-mentioned device and method were used to conduct a test on the resistance to molten iron shrinkage stress.

[0069] Five refractory samples 900 are fabricated from carbon brick A. Each sample has a cylindrical main body 910 with a diameter of 10 mm (cross-sectional area of ​​approximately 78.5 square millimeters). Five annular layers 920 are integrally fabricated on the main body, each layer having an outer diameter of 20 mm, a thickness of 5 mm, a gap of 5 mm, and a spacing of 10 mm between adjacent layers. A tension seat 600 is fixed to the upper crossbeam of a cuboid test bracket 100. Five tension probes are evenly distributed around the circumference of the tension seat 600, and an infrared temperature probe 400 is located at the center of the tension seat 600. Five sample clamps 530 are screwed onto five pull rods 520, and the height difference between adjacent sample clamps 530 is adjusted to 10 mm (equal to the layer spacing). The five refractory samples 900 are then installed on the sample clamps 530. A graphite crucible 200 containing approximately 3 kg of molten iron at a temperature of 1500°C is placed on a fixed sleeve 710. The bottom of the fixed sleeve 710 is bolted to a fixed base 720. A mullite fiber felt with a thickness of approximately 25 mm is laid between the inside of the fixed sleeve 710, the upper surface of the fixed base 720, and the bottom of the graphite crucible 200. The fixed base 720 is raised by adjusting four height adjustment components 730, so that samples 1 to 5 have 1, 2, 3, 4, and 5 annular layers 920 immersed in the molten iron 930, respectively.

[0070] Zero the readings of the five tensile probes so that the tensile force displayed on all five monitors 300 is zero. Turn on the infrared temperature probe 400 and allow the molten iron 930 to cool naturally in the air (the measured cooling rate is approximately 4℃ / min). Record the tensile force on the five samples every 10℃ drop in temperature, and convert the tensile force to tensile strength by dividing the tensile force by the cross-sectional area of ​​the cylindrical main body 910. The tensile strength of the five samples of carbon brick A during solidification and cooling from 1200℃ to 800℃ (the average value of three parallel tests, in MPa; "broken" in the table indicates that the sample broke at that temperature, and no further data is provided thereafter) is shown in the table below.

[0071] Tensile strength of carbon brick sample A as temperature decreases (unit: MPa) Analysis of the above data: Sample No. 5 broke at 1000℃ (tensile strength at break: 3.23 MPa), and Sample No. 4 broke at 890℃ (tensile strength at break: 3.30 MPa). Three additional cylindrical samples of the same specification from the same batch of carbon brick A were tested on a tensile testing machine, and their tensile strengths were 2.85, 3.10, and 3.35 MPa, respectively. The average tensile strength was taken as 3.10 MPa, and 50% of the average tensile strength is 1.55 MPa. Based on this, the characteristic temperatures of the samples at each immersion depth are determined as shown in the table below.

[0072] Characteristic temperatures of carbon brick A samples at various immersion depths The results above show that the greater the immersion depth, the greater the tensile stress on the refractory material at the same temperature, and the tensile stress increases monotonically as the temperature decreases. When one piece is immersed, the highest tensile stress experienced by the sample during the entire cooling process is only 0.82 MPa (approximately 26% of the average tensile strength), far below 50% of the average tensile strength, and it can withstand multiple temperature fluctuations. When two or three pieces are immersed, the tensile stress exceeds 50% of the average tensile strength after the temperature drops below 930℃ and 1020℃, respectively. When four or five pieces are immersed, the tensile stress exceeds 50% of the average tensile strength after the temperature drops below 1040℃ and 1050℃, respectively, and they eventually break at 890℃ and 1000℃, respectively. Based on this, the suitable operating temperature range for carbon brick A is as follows: In the early stage of furnace hearth use, when the hot surface of the carbon brick is relatively regular and the molten iron 930 is immersed to a shallow depth (no more than 3 pieces, i.e., no more than 30 mm), the temperature of the hot surface of the carbon brick should be kept above 1020℃, avoiding repeated fluctuations below 1020℃; when the hot surface of the carbon brick is eroded into an irregular shape and the molten iron 930 is immersed to a depth of more than 4 pieces (more than 40 mm), the temperature of the hot surface of the carbon brick should be kept above 1050℃, avoiding repeated fluctuations below 1050℃, otherwise the tensile stress formed by the shrinkage of the solidified iron will exceed the tensile strength of the carbon brick, directly causing the carbon brick to crack and peel off.

[0073] In another embodiment of the present invention, the thickness of the annular layer 920 can be changed to 10 mm, and the gap can be maintained at 5 mm. This results in a 15 mm spacing between adjacent layers, and the height difference between adjacent sample clamps 530 can be synchronously adjusted to 15 mm. The remaining steps are the same as in the previous example. In this case, the solidified iron bonding area of ​​a single layer increases, and the tensile strength measured under the same number of immersed layers is approximately 8% to 12% higher than in the previous example. The stress warning temperature also increases by approximately 10 to 20°C, making it suitable for evaluating refractory conditions with thicker hot-surface cracking layers.

[0074] In another embodiment of the present invention, another type of carbon brick B was tested under the same sample specifications and test conditions as described above. Its average tensile strength was measured to be 2.20 MPa (50% of which is 1.10 MPa). When three samples were immersed, carbon brick B reached 50% of its average tensile strength at 1050℃ (compared to 1020℃ for carbon brick A), and broke at 930℃ (the three samples of carbon brick A did not break throughout the process). It is evident that under the same 930℃ solidification shrinkage conditions of molten iron, carbon brick B's resistance to 930℃ cold shrinkage stress is significantly weaker than that of carbon brick A, and its suitable operating temperature range is narrower. Therefore, the resistance of different refractories to 930℃ cold shrinkage stress can be quantitatively ranked, guiding the selection of blast furnace hearth refractories and the formulation of temperature regimes.

[0075] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0076] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A testing device for the resistance of refractory materials to molten iron cooling shrinkage stress, characterized in that, The device includes a test stand, a graphite crucible, a display, a temperature measuring instrument, and at least two tensile testing components. The graphite crucible is used to hold molten iron. The tensile testing components are mounted on the test stand, located above the graphite crucible, with their lower ends inside the graphite crucible. The lower end of the tensile testing components is used to mount refractory samples. The distance between the lower end of the tensile testing components and the bottom of the graphite crucible is a predetermined distance, and multiple predetermined distances increase sequentially with a predetermined height. The tensile testing components are used to detect the tensile force received by the lower end of the tensile testing components. The display is used to display the tensile force received by the lower end of each tensile testing component. The temperature measuring instrument is used to measure the temperature of the molten iron inside the graphite crucible.

2. The refractory material resistance to molten iron cooling shrinkage stress testing device as described in claim 1, characterized in that, The tensile testing assembly includes a tensile probe, a pull rod, and a sample clamp. The tensile probe is mounted on the test bracket. The pull rod connects the tensile probe and the sample clamp. The sample clamp is used to hold the refractory sample, and the height of the sample clamp is adjustable.

3. The refractory material resistance to molten iron cooling shrinkage stress testing device as described in claim 2, characterized in that, It also includes a tension seat, through which the tension probe is mounted on the test bracket, and the tension probe is evenly distributed on the tension seat along the circumference.

4. The refractory material resistance to molten iron cooling shrinkage stress testing device as described in claim 3, characterized in that, The temperature measuring instrument is an infrared temperature probe.

5. The refractory material resistance to molten iron cooling shrinkage stress testing device as described in claim 3, characterized in that, The infrared temperature measuring probe is located on the tension base and at the center of the plurality of tension probes.

6. The refractory material resistance to molten iron cooling shrinkage stress testing device as described in claim 1, characterized in that, It also includes a test base for supporting the graphite crucible.

7. The refractory material resistance to molten iron cooling shrinkage stress testing device as described in claim 6, characterized in that, The test base includes a fixing sleeve, a fixing base, and a height adjustment component. The height adjustment component supports the fixing base and adjusts the height of the fixing base. The fixing sleeve is fixed above the fixing base and supports the graphite crucible.

8. The refractory material resistance to molten iron cooling shrinkage stress testing device as described in claim 1, characterized in that, The number of displays is multiple, and each display corresponds to a tensile testing component to display the tensile force applied to the lower end of a single tensile testing component.

9. A method for testing the resistance to molten iron cooling shrinkage stress of refractory materials using the apparatus described in any one of claims 1-8, characterized in that, The refractory specimen is used for the resistance to molten iron cooling shrinkage stress test, and the refractory specimen comprises: The refractories include a cylindrical main body and at least two annular layers, the annular layers being sleeved on and integrally connected to the cylindrical main body. Multiple annular layers are distributed sequentially from bottom to top on the cylindrical main body, with the spacing between adjacent annular layers equal to a predetermined height. The method for testing the resistance of refractory materials to molten iron shrinkage stress includes: Multiple refractory samples are respectively installed on multiple tensile testing components of the testing device, and one refractory sample is installed on each tensile testing component; Multiple refractory samples are immersed in molten iron, and the number of annular layers of refractory samples immersed in molten iron increases sequentially starting from one layer. The tensile force measured by the tensile testing component is reset to zero, so that the tensile force displayed on the monitor is zero; Turn on the temperature measuring instrument and record the test data of how the tensile force measured by each tensile test component changes with temperature; The measured test data are analyzed to obtain the tensile properties of the refractory material under furnace hearth temperature fluctuations and the suitable operating temperature range.

10. The method for testing the resistance of refractory materials to molten iron cooling shrinkage stress as described in claim 9, characterized in that, Analyzing the measured test data to obtain the tensile properties and suitable operating temperature range of the refractory material under furnace hearth temperature fluctuations includes: dividing the tensile force measured by each tensile testing component at each temperature by the cross-sectional area of ​​the cylindrical main body to obtain the tensile strength of each refractory sample at each temperature; taking the average tensile strength of the broken refractory sample as the average tensile strength of the refractory material; for each refractory sample, determining the temperature at which the tensile strength of the refractory sample begins to be greater than zero as the stress initiation temperature, and determining the temperature at which the tensile strength of the refractory sample reaches 50% of the average tensile strength as the stress warning temperature; and comparing the stress warning temperature with the stress initiation temperature. The temperature range between the temperatures is defined as the stress formation temperature range; the temperature at which the refractory sample breaks is defined as the limit service temperature of the refractory at the corresponding immersion depth; the number of annular layers of the refractory sample immersed in the molten iron characterizes the depth of molten iron penetration of the refractory, and the corresponding relationship between immersion depth, tensile strength and temperature is obtained, as well as the stress formation temperature range and the limit service temperature at each immersion depth, which are used as the tensile properties of the refractory when the hearth temperature fluctuates, and the temperature range above the stress warning temperature is defined as the suitable service temperature range of the refractory, and the temperature range below the stress warning temperature is defined as the temperature range in which the refractory needs to avoid repeated fluctuations.

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