Testing Method for Slag Erosion Resistance of Magnesia-Calcia Refractory Used in AOD Furnace

Abstract

The present invention relates to a method for detecting the slag erosion resistance of magnesia-calcia refractory materials for AOD furnaces. In this detection method, the working surface of the magnesia-calcia refractory material for AOD is cut and then broken and pulverized together with the final slag of AOD smelting to obtain a mixed and finely ground powder. Sampling is carried out by the quartering method, and the loss on ignition of the test sample is measured. If the absolute value of the difference in loss on ignition is less than 0.05, then pyrometric cones are prepared; otherwise, the test sample is mixed in a mixer until the difference in loss on ignition is less than 0.05, and then pyrometric cones are prepared. The pyrometric cones are placed on the cone table and the angle with the cone table is recorded for refractoriness detection, and the change in the angle is observed. When the angle changes by 15 - 25°, the temperature at this time is recorded, and the slag resistance of the magnesia-calcia refractory material for AOD furnaces is characterized by the temperature corresponding to the change in the angle. The method for detecting the slag erosion resistance of the magnesia-calcia refractory material for AOD furnaces according to the present invention has high detection accuracy, strong applicability, is simple and easy to implement, and has a low cost, and can largely ensure the stability of the AOD furnace life.

Description

Technical Field

[0001] The present invention relates to the field of refractories, and particularly to a method for detecting slag erosion resistance of magnesia-calcia refractories for AOD furnaces. Background Art

[0002] Magnesia-calcia refractories have excellent properties such as high refractoriness, good slag resistance, excellent thermal shock stability, good stability under high-temperature vacuum, and the ability to purify molten steel. They are the most suitable refractories for smelting stainless steel in AOD furnaces so far. The most severely damaged parts of the 45t AOD furnace and 180t AOD furnace of Baowu Taiyuan Iron and Steel Group are the trunnion slag lines, which seriously restrict the service life of the AOD furnace. The main reason for the damage of magnesia-calcia refractories at the trunnion slag line is the erosion of the slag on the refractories. Microscopic observation of the magnesia-calcia refractories found that after the slag penetrates into the refractories, it does not damage the structure of the refractories, but after the slag erodes the refractories, it will cause changes in the structure of the refractories, thereby affecting the furnace life.

[0003] At present, the research on slag resistance of refractories includes static slag resistance experiments and dynamic slag resistance experiments. The static slag resistance experiment generally uses the crucible method, that is, the slag is added to a crucible made of magnesia-calcia bricks of a fixed size. After high-temperature calcination, the specimen is cut, and the slag resistance is characterized by the erosion percentage and penetration percentage; in actual use, the slag is dynamic, and the erosion and penetration of the slag on the refractories are actually more severe; in addition, the hydration in the preparation process of the crucible and the limitation of the firing temperature will cause deviations in the experiment. The dynamic slag resistance experiments mainly include the rotary slag erosion method and the rotary rod method. These two methods are costly, and the tests and equipment are more complex than the static slag resistance experiment, and the hydration in the brick-making process cannot be avoided.

[0004] The present invention aims to overcome the defects of the prior art. The purpose is to provide a method for detecting slag erosion resistance of magnesia-calcia refractories for AOD furnaces. The detection method of slag erosion resistance of magnesia-calcia refractories for AOD furnaces avoids the influence of magnesia-calcia brick hydration, has high accuracy, strong applicability, is simple and easy to operate, has low cost, and can largely ensure the stability of the AOD furnace life. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for detecting slag erosion resistance of magnesia-calcia refractories for AOD furnaces in view of the above problems.

[0006] The object of the present invention is achieved as follows: A method for detecting the slag erosion resistance of magnesia-calcia refractory materials for AOD furnaces, comprising the following steps: Step 1: After cutting the working surface of magnesia-calcia refractory materials for AOD furnaces with a content of 45-55 wt%, it is broken and pulverized together with 45-55 wt% of the final slag of AOD smelting until it all passes through the test sieve. The fine powder less than 0.09 mm in the ground sample should be less than 50 wt%; Step 2: Sampling the ground sample by the quartering method and testing the loss on ignition of the sample. If the absolute value of the difference between the maximum and minimum values of the loss on ignition is less than 0.05, the sample after the loss on ignition test can be used to prepare pyrometric cones; otherwise, the sample is mixed in a mixer until the difference in loss on ignition is less than 0.05, and then pyrometric cones are prepared; The number of prepared pyrometric cones is 2-5; Step 3: Place the pyrometric cones into the cone table, fix them with refractory mud and then place them on the rotating table of the refractoriness furnace. Heat it at a heating rate of 8-10 °C / min to 1200-1300 °C, then turn on the rotating table of the refractoriness furnace, and then heat it at a rate of 2.5 °C / min until the temperature corresponding to the pyrometric cone bending 15-25° is reached. Record the picture and temperature of the pyrometric cone at this time. The higher the temperature, the stronger the slag erosion resistance.

[0007] The magnesia-calcia refractory material for AOD is a refractory product used at the slag line of the AOD furnace.

[0008] The test sieve needs to comply with the provisions of GB / T 6003.1.

[0009] The detection method of the loss on ignition is as follows: Take a sample of 200-300 g; Dry it at 110-150 °C for 3-6 h, and then weigh it to obtain the mass A; The dried sample is burned at 1000-1100 °C for 3-5 h. The ceramic crucible used can withstand a high temperature of more than 1200 °C. After cooling, weigh it to obtain the mass B; The loss on ignition is (A - B) / A. If the loss on ignition is greater than 1 wt%, the magnesia-calcia refractory material needs to be taken again.

[0010] The height error between the mold for preparing the pyrometric cone and the height of the standard pyrometric cone is 0~+10%.

[0011] The refractory mud does not react with the pyrometric cone and the water content is below 0.05 wt%.

[0012] The flatness of the cone table is less than 2 mm.

[0013] The thermocouple used in the refractoriness furnace is a type B thermocouple and must be calibrated. The camera for recording the picture of the pyrometric cone can clearly observe the image of the pyrometric cone at 0-2000 °C.

[0014] The method for detecting the slag erosion resistance of magnesia-calcia refractory materials for AOD furnaces is the slag erosion resistance of magnesia-calcia refractory materials for AOD furnaces detected according to the method for detecting the slag erosion resistance of magnesia-calcia refractory materials for AOD furnaces described in any one of claims 1-8.

[0015] The beneficial effects of the present invention are as follows: The slag used in the present invention is the final slag of AOD smelting, which can be taken and used at any time. The results of the slag erosion resistance experiment have higher accuracy compared to only using the final slag of a certain smelting time or the prepared slag; since the working surface of the magnesia-calcia refractory material is in direct contact with the AOD slag, the working surface of the refractory material is selected, which can better reflect the erosion of the slag on the refractory material; the determination of the loss on ignition can not only detect the uniformity of the mixture of the final slag of smelting and the working surface of the refractory material, but also detect the degree of hydration of the magnesia-calcia refractory material before preparing the pyrometric cone, eliminating the influence of the hydration of the magnesia-calcia refractory material on the experiment.

[0016] Since the damage of the magnesia-calcia refractory material mainly comes from the erosion of the slag, and the penetration of the slag cannot damage the structure of the refractory material, the slag and the refractory material are fully mixed, assuming that the slag has penetrated into the refractory material, only considering the erosion of the slag on the refractory material, and excluding the influence of the penetration of the slag on the refractory material; when conducting the refractoriness experiment, if the refractoriness is used as the basis for erosion, a large amount of liquid phase has been generated at this time, and the refractory material has been completely eroded by the slag and has lost its high-temperature structure and can no longer be used as a refractory material; using the degree of bending as the judgment basis can effectively reflect the deformation process at high temperature, characterize the process of the structure change of the refractory material caused by the erosion of the slag, with high accuracy, strong applicability and low cost; the accurate characterization of the slag erosion resistance performance greatly guarantees the stability of the AOD furnace life.

[0017] Since the refractoriness testing device can automatically record the bending angle of the pyrometric cone, it avoids the influence of people on the experiment and improves the accuracy and stability of the experiment.

[0018] Therefore, the method for detecting the slag erosion resistance of the magnesia-calcia refractory material for AOD furnace prepared by the present invention avoids the influence of the hydration of the magnesia-calcia brick, has high accuracy, strong applicability, is simple and easy to implement, and has low cost, and can greatly guarantee the stability of the AOD furnace life. Specific embodiments

[0019] To achieve the above object, the technical solution adopted by the present invention is:

[0020] ① The slag used is the final slag of AOD smelting, which can be taken and used at any time. The results of the slag erosion resistance experiment have higher accuracy compared to only using the final slag of a certain smelting time or the prepared slag; ② The determination of the loss on ignition can not only detect the uniformity of the mixture of the final slag of smelting and the working surface of the refractory material, but also detect the degree of hydration of the magnesia-calcia refractory material before preparing the pyrometric cone, eliminating the influence of the hydration of the magnesia-calcia refractory material on the experiment; ③ Using the degree of bending as the judgment basis can effectively reflect the deformation process at high temperature, characterize the process of the structure change of the refractory material caused by the erosion of the slag, with high accuracy, strong applicability and low cost; the accurate characterization of the slag erosion resistance performance greatly guarantees the stability of the AOD furnace life.

[0021] A method for detecting the slag erosion resistance of magnesia-calcium refractories for AOD furnaces. The steps of the preparation method are as follows: Step 1: Cut the working surface of magnesia-calcium refractories for AOD furnaces accounting for 45-55wt% and mix them with the final slag of AOD smelting accounting for 45-55wt%, and then break and crush them until all pass through a 0.18mm test sieve. The fine powder less than 0.09mm in the ground sample should be less than 50wt%.

[0022] Step 2: Take samples of the ground samples by the quartering method and test the loss on ignition of the samples. If the absolute value of the difference between the maximum and minimum values of the loss on ignition is less than 0.05, the samples after the loss on ignition test can be used to prepare pyrometric cones; otherwise, mix the samples in a mixer until the difference in loss on ignition is less than 0.05, and then prepare pyrometric cones; the number of prepared pyrometric cones is 2-5.

[0023] Step 3: Place the pyrometric cones into the cone platform, fix them with refractory mortar, and then place them on the rotating table of the refractoriness furnace. Heat at a heating rate of 8-10°C / min to 1200-1300°C, then turn on the rotating table of the refractoriness furnace, and then heat at a rate of 2.5°C / min (this heating rate is the heating rate specified in GB / T 7322 and GB / T 13794) to the temperature corresponding to when the pyrometric cone bends 15-25°. Record the picture and temperature of the pyrometric cone at this time. The higher the temperature, the stronger the slag erosion resistance.

[0024] The magnesia-calcium refractories for AOD furnaces are refractory products used at the slag line of AOD furnaces.

[0025] The test sieve needs to comply with the provisions of GB / T 6003.1.

[0026] The detection method of the loss on ignition is as follows: Take 200-300g of samples; dry them at 110-150°C for 3-6h, and then weigh (mass A); burn the dried samples at 1000-1100°C for 3-5h (using a ceramic crucible that can withstand high-temperature calcination above 1200°C), cool them, and then weigh (mass B); the loss on ignition is (A - B) / A. If the loss on ignition is greater than 1wt%, re-take the magnesia-calcium refractories.

[0027] The height error between the mold for preparing the pyrometric cone and the height of the standard pyrometric cone is 0~+10%.

[0028] The refractory mortar does not react with the pyrometric cone and the water content is below 0.05wt%.

[0029] The flatness of the cone platform is less than 2mm.

[0030] The thermocouple of the refractoriness furnace is a B-type thermocouple and must be calibrated; the camera for recording the picture of the pyrometric cone can clearly observe the image of the pyrometric cone at 0-2000°C.

[0031] The slag erosion resistance detection method of the magnesia-calcia refractory for AOD furnace is based on the slag erosion resistance of the magnesia-calcia refractory for AOD furnace detected by the slag erosion resistance detection method of the magnesia-calcia refractory for AOD furnace according to any one of claims 1 to 8.

[0032] The present invention will be further described below in conjunction with specific embodiments, and it is not a limitation to its protection scope.

[0033] To avoid repetition, the equipment and materials involved in the specific embodiments are uniformly described as follows and will not be repeated in the embodiments:

[0034] The magnesia-calcia refractory for AOD is a refractory product used at the slag line of the AOD furnace.

[0035] The test sieve needs to comply with the provisions of GB / T 6003.1.

[0036] The detection method of ignition loss is as follows: Take 200 g of samples; dry at 110 °C for 4 h, and then weigh (mass A); burn the dried samples at 1050 °C for 4 h (the used ceramic crucible can withstand a high temperature of more than 1200 °C), and weigh after cooling (mass B); the ignition loss is (A - B) / A. If the ignition loss is greater than 1 wt%, new magnesia-calcia refractory needs to be taken.

[0037] The error between the height of the mold for preparing the pyrometric cone and the height of the standard pyrometric cone is 0 to +10%.

[0038] The refractory mud does not react with the pyrometric cone and the water content is below 0.05 wt%.

[0039] The flatness of the frustum is less than 2 mm.

[0040] The thermocouple for the refractoriness furnace is a type B thermocouple and must be calibrated; the camera for recording the pictures of the pyrometric cone can clearly observe the images of the pyrometric cone at 0 - 2000 °C.

[0041] Example 1

[0042] A slag erosion resistance detection method of the magnesia-calcia refractory for AOD furnace. The steps of the detection method described in this example are as follows:

[0043] Step 1: Cut the working surface of 50 wt% of the magnesia-calcia refractory for AOD and crush it together with 50 wt% of the final slag of AOD smelting to all pass through a 0.18 mm test sieve, and the fine powder less than 0.09 mm in the ground samples should be less than 50 wt%.

[0044] Step 2: Sample the ground specimen using the quartering method, and test the loss on ignition of the specimen. If the absolute value of the difference between the maximum and minimum values of the loss on ignition is less than 0.05, the specimen after the loss on ignition test can be used to prepare the pyrometric cones; otherwise, mix the specimen in a mixer until the difference in loss on ignition is less than 0.05, and then prepare the pyrometric cones. The number of pyrometric cones prepared is 5.

[0045] Step 3: Place the pyrometric cones into the cone holder, fix them with refractory mortar, and then place them on the rotating table of the refractoriness furnace. Heat at a heating rate of 10 °C / min until 1200 °C, then turn on the rotating table of the refractoriness furnace, and then heat at a rate of 2.5 °C / min until the temperature corresponding to the pyrometric cones bending 20° is reached. Record the pyrometric cone pictures and temperature at this time. The higher the temperature, the stronger the slag erosion resistance.

[0046] Through testing, for the slag erosion resistance detection method of the magnesia-calcia refractory material for AOD furnace in this example, the temperature corresponding to the pyrometric cones bending 20° is 1660 °C, and the service life of the AOD is 47 furnaces.

[0047] Example 2

[0048] A magnesia-calcia refractory material for AOD smelting nickel-based alloys and its preparation method. The steps of the detection method in this example are as follows:

[0049] Step 1: Cut the working surface of 50 wt% of the magnesia-calcia refractory material for AOD and break and pulverize it together with 50 wt% of the final slag of AOD smelting until it all passes through a 0.18 mm test sieve. The fine powder less than 0.09 mm in the ground specimen should be less than 50 wt%.

[0050] Step 2: Sample the ground specimen using the quartering method, and test the loss on ignition of the specimen. If the absolute value of the difference between the maximum and minimum values of the loss on ignition is less than 0.05, the specimen after the loss on ignition test can be used to prepare the pyrometric cones; otherwise, mix the specimen in a mixer until the difference in loss on ignition is less than 0.05, and then prepare the pyrometric cones. The number of pyrometric cones prepared is 5.

[0051] Step 3: Place the pyrometric cones into the cone holder, fix them with refractory mortar, and then place them on the rotating table of the refractoriness furnace. Heat at a heating rate of 9 °C / min until 1250 °C, then turn on the rotating table of the refractoriness furnace, and then heat at a rate of 2.5 °C / min until the temperature corresponding to the pyrometric cones bending 20° is reached. Record the pyrometric cone pictures and temperature at this time. The higher the temperature, the stronger the slag erosion resistance.

[0052] Through testing, for the slag erosion resistance detection method of the magnesia-calcia refractory material for AOD furnace in this example, the temperature corresponding to the pyrometric cones bending 20° is 1750 °C, and the service life of the AOD is 71 furnaces.

[0053] Example 3

[0054] A kind of magnesia-calcia refractory for AOD smelting of nickel-based alloy and its preparation method. The steps of the detection method in this embodiment are as follows:

[0055] Step 1: Cut the working surface of 50wt% magnesia-calcia refractory for AOD and crush it together with 50wt% final slag of AOD smelting until it all passes through a 0.18mm test sieve. The fine powder less than 0.09mm in the ground sample should be less than 50wt%.

[0056] Step 2: Take samples of the ground sample by the quartering method and test the loss on ignition of the sample. If the absolute value of the difference between the maximum and minimum values of the loss on ignition is less than 0.05, the sample after the loss on ignition test can be used to prepare the pyrometric cones; otherwise, mix the sample in a mixer until the difference in loss on ignition is less than 0.05, and then prepare the pyrometric cones; the number of prepared pyrometric cones is 5.

[0057] Step 3: Place the pyrometric cones into the cone table, fix them with refractory mud and then place them on the rotating table of the refractoriness furnace. Heat at a heating rate of 10°C / min to 1300°C, then turn on the rotating table of the refractoriness furnace, and then heat at a rate of 2.5°C / min to the temperature corresponding to when the pyrometric cone bends 20°. Record the picture and temperature of the pyrometric cone at this time. The higher the temperature, the stronger the slag erosion resistance.

[0058] The slag erosion resistance detection method of the magnesia-calcia refractory for AOD furnace in this embodiment is detected: the temperature corresponding to when the pyrometric cone bends 20° is greater than 1800°C, and the service life of AOD is 72 - 84 furnaces.

[0059] At present, the maximum temperature measurement of the existing standard pyrometric cones in the laboratory is 1800°C, and the maximum temperature measurement of the internationally recognized pyrometric cones is also 1800°C. Therefore, the temperature listed here can only be written as greater than 1800°C; above 1800°C, the temperature measurement deviation of the B-type thermocouple is relatively large. The B-type thermocouple can accurately measure the temperature up to 1600°C, and can measure up to 1800°C after correction. At higher temperatures, it cannot be detected; in addition, the national standard stipulates that the thermocouple is the B-type thermocouple. Therefore, when the national professional institution detects a temperature greater than 1800°C, it is directly written as greater than 1800°C or greater than CN180.

[0060] The above are only specific embodiments of the present invention, but the structural features within the protection scope of the present invention are not limited to this. Any changes or modifications made by any person skilled in the art within the field of the present invention are covered by the patent scope of the present invention.

Claims

1. A method for detecting the slag erosion resistance of magnesia-calcia refractory materials used in AOD furnaces, characterized in that: It includes the following steps: Step 1: Cut the working surface of the magnesia-calcia refractory material for AOD with 45-55wt% and crush it together with 45-55wt% of the final slag of AOD smelting until it all passes through the test sieve. The fine powder less than 0.09mm in the ground sample should be less than 50wt%; Step 2: Sample the ground sample by the quartering method and test the loss on ignition of the sample. If the absolute value of the difference between the maximum and minimum values of the loss on ignition is less than 0.05, the sample after the loss on ignition test can be used to prepare the pyrometric cones; otherwise, mix the sample in a mixer until the difference in loss on ignition is less than 0.05, and then prepare the pyrometric cones; the number of prepared pyrometric cones is 2-5; Step 3: Place the pyrometric cones in the cone table, fix them with refractory mud and then place them on the rotating table of the refractoriness furnace. Heat at a heating rate of 8-10°C / min to 1200-1300°C, then open the rotating table of the refractoriness furnace, and then heat at a rate of 2.5°C / min until the temperature corresponding to the pyrometric cone bending 15-25° is reached. Record the picture and temperature of the pyrometric cone at this time. The higher the temperature, the stronger the slag erosion resistance.

2. The method for detecting the slag erosion resistance of magnesia-calcia refractory materials used in AOD furnaces according to claim 1, characterized in that: The magnesia-calcia refractory material for AOD is a refractory product used at the slag line of the AOD furnace.

3. The method for detecting the slag erosion resistance of magnesia-calcia refractory materials used in AOD furnaces according to claim 1, characterized in that: The test sieve needs to comply with the regulations of GB / T 6003.

1.

4. The method for detecting the slag erosion resistance of magnesia-calcia refractory materials used in AOD furnaces according to claim 1, characterized in that: The detection method of the loss on ignition is as follows: Take a sample of 200-300g; dry it at 110-150°C for 3-6h, and then weigh to obtain the mass A; burn the dried sample at 1000-1100°C for 3-5h. The ceramic crucible used can withstand a high temperature of more than 1200°C. After cooling, weigh to obtain the mass B; the loss on ignition is (A - B) / A. If the loss on ignition is greater than 1wt%, re-take the magnesia-calcia refractory material.

5. The method for detecting the slag erosion resistance of magnesia-calcia refractory materials used in AOD furnaces according to claim 1, characterized in that: The height error between the mold for preparing the pyrometric cone and the height of the standard pyrometric cone is 0~+10%.

6. The method for detecting the slag erosion resistance of magnesia-calcia refractory materials used in AOD furnaces according to claim 1, characterized in that: The refractory mud does not react with the pyrometric cone and the water content is below 0.05wt%.

7. The method for detecting the slag erosion resistance of magnesia-calcia refractory materials used in AOD furnaces according to claim 1, characterized in that: The flatness of the cone table is less than 2mm.

8. The method for detecting the slag erosion resistance of magnesia-calcia refractory materials used in AOD furnaces according to claim 1, characterized in that: The thermocouple used in the refractoriness furnace is a type B thermocouple and must be calibrated. The camera for recording the picture of the pyrometric cone can clearly observe the image of the pyrometric cone at 0-2000°C.