A method for testing the performance of a moulded heat activatable agent

Abstract

The present application relates to a kind of test methods of mould casting heat agent performance, the detection method is that mould casting heat agent is ground to 0.088mm below, the weighed good heat agent is placed into thermal analyzer, TG-DTG-DSC test is carried out.TG and DTG temperature-time (T-t), mass-temperature (m-T) curve is made, according to m-T curve, extrapolation initial temperature (Te) is made, Te is as ignition temperature, corresponding decomposition time is as ignition time.According to DSC curve, the curve is integrated, to calculate the heat value.According to DSC and DTG curve, the last peak of DSC curve corresponds to the extension termination temperature (Tc) as the highest combustion temperature.According to DSC, TG curve and T-t curve, the time between the initial temperature of the highest peak and the highest combustion temperature is as the duration of exothermic reaction after secondary ignition.The test method of mould casting heat agent performance described in the application has strong applicability, good safety, high temperature accuracy, and can effectively reduce the casting blank problem caused by mould casting heat agent according to the test results.

Description

Technical Field

[0001] This invention relates to the field of heating agents, and more particularly to a method for testing the performance of a molded heating agent. Background Technology

[0002] In-situ casting exothermic agents are primarily used to release heat, preventing problems such as shrinkage cavities and uneven shrinkage at the riser caused by temperature drops in the billet, which lead to a decrease in yield. They also serve to maintain heat, prevent secondary oxidation, and adsorb inclusions to purify the molten steel. Their performance characteristics include ignition time, ignition temperature, calorific value, maximum combustion temperature, and the duration of the exothermic reaction after secondary ignition. Among these, the calorific value directly affects heat replenishment and is the most important performance characteristic. The exothermic time directly relates to heat preservation performance and is second only to the calorific value. Therefore, some manufacturers use a specified holding temperature for a given time to characterize the heat preservation performance.

[0003] Currently, calorific value is mainly determined using an oxygen bomb calorimeter. The principle involves filling a sealed container with excess oxygen, igniting the exothermic agent, and measuring the calorific value after the agent has fully reacted. However, this method deviates significantly from actual usage, is expensive, inefficient, and its results are heavily influenced by the instrument, resulting in low reproducibility and applicability. Furthermore, it only measures calorific value and cannot test other parameters. Ignition temperature, ignition time, maximum combustion temperature, and the duration of heat release after secondary ignition are typically measured in an electric resistance furnace. This method effectively reflects actual usage conditions, but ignition temperature requires observation with the furnace door open, and ignition time and the duration of heat release need to be recorded manually, making it highly susceptible to human error. Moreover, this method carries inherent risks, produces rough results, and does not include calorific value. Therefore, a suitable testing method is needed that is both practical and reliable, with accurate temperature sensing elements, to directly reflect the quality of the exothermic agent and guide actual field use.

[0004] In view of the above, the present invention aims to overcome the defects of the prior art and provides a test method for the performance of molded heating agents. The test method for the performance of molded heating agents conforms to actual use conditions, has strong applicability, is safe and reliable, has accurate temperature detection elements, can intuitively reflect the quality of heating agents, and guide actual use on site. Summary of the Invention

[0005] The purpose of this invention is to address the above-mentioned problems by providing a method for testing the performance of molded heating agents.

[0006] The objective of this invention is achieved as follows: A method for testing the performance of a molded heating agent, comprising the following steps: Step 1: Weigh 10.0±1.00g of the molded heating agent and place it in a halogen rapid moisture analyzer to test the moisture content of the sample; if the moisture content is greater than 1.5wt%, it is directly judged as unqualified; if the moisture content is less than 1.5wt%, the moisture content is qualified. Grind the molded heating agent after the moisture test to below 0.088mm; Step 2: Before the experiment, use pure substances In, Sn, Zn, Ag, Au, Ni, and Pd to perform temperature and calorimetric calibration on the thermal analyzer; the heating rate is 10℃ / min, and then the blank baseline is determined. The blank baseline is subtracted during sample testing to ensure a flat baseline is obtained; Step 3: Take 3-10mg of the qualified molded heating agent and place it in the calibrated thermal analyzer, with a heating rate of 10℃ / min and an air atmosphere, to perform thermogravimetric and differential pressure analysis. Step 4: Using a thermal analyzer, generate temperature-time and mass-temperature curves for thermogravimetric analysis (TGA) and differential scanning calorimetry (DTG). Determine the extrapolated starting temperature, using it as the ignition temperature and the corresponding decomposition time as the ignition time. Alternatively, export the data and plot the intersection of the tangent line of the descending segment of the curve with the extended baseline; the temperature corresponding to this intersection is the ignition temperature, and the decomposition time corresponding to the ignition temperature is the ignition time. Step 5: Using a thermal analyzer, calculate the calorific value based on the peak area of ​​the exothermic peak in the differential scanning calorimetry curve. Alternatively, export the relevant data, integrate the differential scanning calorimetry curve, and calculate the calorific value accordingly. Based on the differential scanning calorimetry and DTG curves, the extrapolated termination temperature corresponding to the last peak of the differential scanning calorimetry curve is taken as the maximum combustion temperature. Based on the differential scanning calorimetry, thermogravimetric analysis, and temperature-time curves, the time between the starting temperature corresponding to the highest peak and the maximum combustion temperature is taken as the duration of the exothermic reaction after secondary ignition.

[0007] The rapid moisture meter uses a halogen lamp for heating, has a moisture readability of 0.01wt%, and can reach a temperature of 100-150℃. It requires periodic calibration.

[0008] The pure substances In, Sn, Zn, Ag, Au, Ni, and Pd are all standard substances with a purity of over 99%.

[0009] The thermal analyzer is a synchronous thermal analyzer with an operating temperature range of 25-1600℃. The thermal balance resolution can reach 0.03μg, the temperature fluctuation can reach ±0.1℃, and the temperature resolution can reach 0.1℃. The resolution, accuracy, and sensitivity of differential scanning calorimetry can all reach 0.1μW.

[0010] By adopting the above technical solution, this invention has the following advantages compared with the prior art: The synchronous thermal analyzer is a precision instrument with a good temperature control system and high temperature accuracy; at the same time, the heat control is precise, which is beneficial for the calculation of calorific value. Before detection, its temperature can be calibrated with pure substances, and a blank baseline can be measured to obtain a flat baseline, which facilitates the finding of ignition temperature, maximum combustion temperature, and the duration of the exothermic reaction after secondary ignition. Similarly, a flat baseline is beneficial for the accurate calculation of calorific value. Furthermore, the instrument has good safety assurance and is highly safe.

[0011] In-mold exothermic agents generally consist of an exothermic agent, an oxidizing agent, a co-solvent, and a flame retardant. The exothermic agent is mainly aluminum powder and silicon powder, the oxidizing agent is mainly nitrates and metal oxides, the co-solvent is mainly fluorides and halides, and the flame retardant is mainly carbon materials, thus controlling the reaction rate. Therefore, the DSC curve of a conventional exothermic agent has two main peaks. The first peak originates from the decomposition of the oxidizing agent. Nitrates decompose at around 400℃, releasing oxygen (the first peak). The oxygen oxidizes the exothermic agent, and the oxidizing agent, upon heating, melts the co-solvent. Then, the exothermic agent reacts exothermically with the metal oxide, resulting in the second peak, which often has two or more smaller peaks. Since the reaction begins with the oxygen released from the decomposition of nitrates, the decomposition temperature of the nitrate is taken as the ignition temperature, and the corresponding decomposition time is taken as the ignition time, which can be determined based on the TG and DTG curves. The second peak primarily originates from the exothermic agent (aluminothermic reaction). Because the aluminothermic reaction rate is controlled, the second peak has a relatively long duration, which is used to determine the duration of the exothermic reaction after secondary ignition. The second peak eventually coincides with the baseline, indicating the maximum combustion temperature. If the baseline is not horizontal, an extrapolated termination temperature (Tc) can be used to determine the maximum combustion temperature. Integrating the DSC curve yields the calorific value.

[0012] In summary, using a thermal analyzer to test the performance of molded exothermic agents can provide a one-time test of performance parameters such as ignition temperature, ignition time, duration of exothermic reaction after secondary ignition, maximum combustion temperature, and calorific value. This method closely reflects actual usage conditions and has strong applicability. The thermal analyzer is safe and reliable, with accurate temperature detection elements, and can directly reflect the quality of the exothermic agent, guiding actual on-site use. Detailed Implementation

[0013] The technical solution adopted in this invention is as follows: it can test a variety of molded exothermic agents (carbon steel, stainless steel, expansion agent), with strong universality; it can test the ignition temperature, ignition time, duration of exothermic reaction after secondary ignition, maximum combustion temperature, calorific value and other performance characteristics in one test, which is consistent with actual use and has strong applicability; the testing instrument is safe and reliable, and the temperature detection element is accurate; it can intuitively reflect the quality of the exothermic agent and guide actual use on site.

[0014] The steps of a test method for the performance of a molded heating agent are as follows: Weigh 10.0±1.00g of the molded heating agent and place it in a halogen rapid moisture analyzer to test the moisture content of the sample (test temperature is 110℃); if the moisture content is greater than 1.5wt%, it is directly judged as unqualified; if the moisture content is less than 1.5wt%, the moisture content is qualified. After the moisture test, grind the molded heating agent to below 0.088mm.

[0015] Before the experiment, the thermal analyzer was calibrated using pure substances In (156.6℃), Sn (231.9℃), Zn (419.6℃), Ag (961.8℃), Au (1064.2℃), Ni (1456.0℃), and Pd (1554.0℃). The heating rate was 10℃ / min. Then, the blank baseline was measured. The blank baseline was subtracted during the sample test to ensure that a flat baseline was obtained.

[0016] Take 3-10 mg (appropriate amount) of the properly ground molded exothermic agent (the amount of exothermic agent should match the thermal analyzer) and place it into a calibrated thermal analyzer (there are many types and models of thermal analyzers on the market; any one that meets the requirements for test temperature and accuracy is acceptable; the data obtained so far comes from Taiyuan University of Technology, Wuhan University of Science and Technology, Northeastern University, China Iron and Steel Research Institute and Beijing University of Science and Technology). The heating rate is 10℃ / min, the atmosphere is air, and thermogravimetric (TG) and differential scanning calorimetry (DSC) curves are tested.

[0017] A thermal analyzer is used to generate temperature-time (Tt) curves and mass-temperature (mT) curves for TG and DTG (the rate of weight loss of a substance per unit time). The system automatically determines the extrapolated onset temperature (Te), which is taken as the ignition temperature, and the corresponding decomposition time is taken as the ignition time. Alternatively, the data can be exported, and the intersection of the tangent line of the descending segment of the curve and the extended baseline can be plotted. The temperature corresponding to this intersection is the ignition temperature, and the decomposition time corresponding to the ignition temperature is taken as the ignition time. JY / T 0589.2-2020 "General Rules for Thermal Analysis Methods Part 2: Differential Thermal Analysis" 10.1.1 Characteristic Temperature and Time clearly specifies this type of method.

[0018] Similarly, the calorific value can be automatically calculated based on the DSC curve using a thermal analyzer. Relevant data can also be exported, and the DSC curve can be integrated to calculate the calorific value (integration is a basic operation that can be performed using a simple Excel spreadsheet; the author used the graphing software Origin for integration, inputting data and clicking "integrate" to obtain the calorific value). Based on the DSC and DTG curves, the epitaxial termination temperature (Tc) corresponding to the final peak of the DSC curve is taken as the maximum combustion temperature. Based on the DSC, TG, and Tt curves, the time between the initial temperature corresponding to the highest peak and the maximum combustion temperature is taken as the duration of the exothermic reaction after secondary ignition.

[0019] The rapid moisture analyzer uses a halogen lamp for heating, has a moisture readability of 0.01wt%, and can reach a temperature of 100-150℃. It requires calibration at least once a year. (JY / T 0589.2-2020 "General Rules for Thermal Analysis Methods Part 2: Differential Thermal Analysis" 7.4.1 a states that it requires periodic calibration).

[0020] The pure substances In (156.6℃), Sn (231.9℃), Zn (419.6℃), Ag (961.8℃), Au (1064.2℃), Ni (1456.0℃), and Pd (1554.0℃) are standard substances, each with a purity of not less than 99 wt%. (Appendix 2 of JY / T 0589.2-2020 General Rules for Thermal Analysis Methods Part 2: Differential Thermal Analysis).

[0021] The thermal analyzer is a simultaneous thermal analyzer, with an operating temperature range of 25-1600℃. The thermal balance resolution can reach 0.03 μg, the temperature fluctuation can be within ±0.1℃, and the temperature resolution can reach 0.1℃. The resolution, accuracy, and sensitivity of the DSC can all reach 0.1 μW (as specified in JY / T 0589.1-2020 "General Rules for Thermal Analysis Methods Part 1: General Rules" 7.3).

[0022] The test method for the performance of the die-casting heating agent is based on the test method described above for the performance of the die-casting heating agent.

[0023] The present invention will be further described below with reference to specific embodiments, but this is not intended to limit the scope of protection thereof.

[0024] To avoid repetition, the equipment and materials involved in the specific implementation are described in a unified manner as follows, and will not be repeated in the examples: The rapid moisture meter is heated by a halogen lamp, the moisture readability is 0.01wt%, the temperature can reach 100-150℃, and it needs to be calibrated regularly.

[0025] The pure substances In (156.6℃), Sn (231.9℃), Zn (419.6℃), Ag (961.8℃), Au (1064.2℃), Ni (1456.0℃) and Pd (1554.0℃) are standard substances, and their purity is not less than 99wt%.

[0026] The thermal analyzer is a synchronous thermal analyzer with an operating temperature range of 25-1600℃. The thermal balance resolution can reach 0.03μg, the temperature fluctuation can reach ±0.1℃, the temperature resolution can reach 0.1℃, and the resolution, accuracy, and sensitivity of the DSC can all reach 0.1μW. Example 1

[0027] A test method for the performance of stainless steel molded heating agent. The steps of the test method described in this embodiment are as follows: Weigh 10.0g of stainless steel molded heating agent and place it in a rapid moisture analyzer to test the moisture content of the sample (test temperature: 110℃); if the moisture content is greater than 1.5wt%, it is directly judged as unqualified; if the moisture content is less than 1.5wt%, the moisture content is qualified. After the moisture test, grind the stainless steel molded heating agent to below 0.088mm.

[0028] The thermal analyzer was calibrated using pure substances In (156.6℃), Sn (231.9℃), Zn (419.6℃), Ag (961.8℃), Au (1064.2℃), Ni (1456.0℃), and Pd (1554.0℃) at a heating rate of 10℃ / min. Then, a blank baseline was measured. The blank baseline was subtracted during sample testing to ensure a flat baseline.

[0029] Take 10 mg of the properly ground stainless steel die-casting exothermic agent and place it into a calibrated thermal analyzer. The heating rate is 10℃ / min and the atmosphere is air. Perform thermogravimetric (TG) and differential scanning calorimetry (DSC) curve tests.

[0030] Using the built-in software of the thermal analyzer, temperature-time (Tt) curves and mass-temperature (mT) curves of TG and DTG were generated.

[0031] The system automatically determined the ignition temperature to be 420.7℃, with a corresponding ignition time of 26s. The thermal analyzer's built-in software calculated the calorific value to be 36090kJ / kg, the maximum combustion temperature to be 1543℃, the duration of the exothermic reaction after secondary ignition to be 82min, and the moisture content to be 0.07wt%. Example 2

[0032] A test method for the performance of carbon steel molded heating agent. The steps of the test method described in this embodiment are as follows: Weigh 10.0g of carbon steel molded heating agent and place it in a rapid moisture analyzer to test the moisture content of the sample (test temperature: 110℃); if the moisture content is greater than 1.5wt%, it is directly judged as unqualified; if the moisture content is less than 1.5wt%, the moisture content is qualified. After the moisture test, grind the carbon steel molded heating agent to below 0.088mm.

[0033] The thermal analyzer was calibrated using pure substances In (156.6℃), Sn (231.9℃), Zn (419.6℃), Ag (961.8℃), Au (1064.2℃), Ni (1456.0℃), and Pd (1554.0℃) (the standard for temperature calibration is JY / T0589-2020). The heating rate was 10℃ / min. Then, the blank baseline was measured. The blank baseline was subtracted during the sample test to ensure a flat baseline.

[0034] Take 10 mg of properly ground carbon steel die casting exothermic agent and place it into a calibrated thermal analyzer. The heating rate is 10℃ / min, and the atmosphere is air. Perform thermogravimetric (TG) and differential scanning calorimetry (DSC) curve tests.

[0035] Using the built-in software of the thermal analyzer, temperature-time (Tt) curves and mass-temperature (mT) curves of TG and DTG were generated.

[0036] The system automatically determined the ignition temperature to be 680.3℃, with a corresponding ignition time of 35s. The thermal analyzer's built-in software calculated the calorific value to be 19150kJ / kg, the maximum combustion temperature to be 1320℃, the duration of the exothermic reaction after secondary ignition to be 57min, and the moisture content to be 0.06wt%. Example 3

[0037] A test method for the performance of an expandable die-casting exothermic agent (expanding agent). The steps of the test method described in this embodiment are as follows: Weigh 10.0g of the expandable die-casting exothermic agent (expanding agent) and place it in a rapid moisture analyzer to test the moisture content of the sample (test temperature: 110℃); if the moisture content is greater than 1.5wt%, it is directly judged as unqualified; if the moisture content is less than 1.5wt%, the moisture content is qualified. After the moisture test, grind the expandable die-casting exothermic agent to below 0.088mm.

[0038] The thermal analyzer was calibrated using pure substances In (156.6℃), Sn (231.9℃), Zn (419.6℃), Ag (961.8℃), Au (1064.2℃), Ni (1456.0℃), and Pd (1554.0℃) at a heating rate of 10℃ / min. Then, a blank baseline was measured. The blank baseline was subtracted during sample testing to ensure a flat baseline.

[0039] Take 3 mg of properly ground expandable die-casting exothermic agent and place it into a calibrated thermal analyzer. The heating rate is 10℃ / min, and the atmosphere is air. Perform thermogravimetric (TG) and differential scanning calorimetry (DSC) curve tests.

[0040] Using the built-in software of the thermal analyzer, temperature-time (Tt) curves and mass-temperature (mT) curves of TG and DTG were generated.

[0041] The system automatically determined the ignition temperature to be 1043.6℃, ​​the corresponding ignition time to be 9 minutes, the thermal analyzer's built-in software to calculate the calorific value to be 8243 kJ / kg, the maximum combustion temperature to be 1095℃, the duration of the exothermic reaction after secondary ignition to be 0 minutes, and the moisture content to be 0.06 wt%.

[0042] The above description is only a specific embodiment of the present invention, but the structural features protected by the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A method for testing the performance of a molded heating agent, characterized in that: The process includes the following steps: Step 1: Weigh 10.0±1.00g of the die-casting heating agent and place it in a halogen rapid moisture analyzer to test the moisture content of the sample; if the moisture content is greater than 1.5wt%, it is directly judged as unqualified; if the moisture content is less than 1.5wt%, the moisture content is qualified. After the moisture test, grind the die-casting heating agent to below 0.088mm. Step 2: Before the experiment, the thermal analyzer was calibrated for temperature and calorimetry using pure substances In, Sn, Zn, Ag, Au, Ni, and Pd. The heating rate was 10℃ / min. Then, the blank baseline was measured. The blank baseline was subtracted during the sample test to ensure a flat baseline was obtained. Step 3: Take 3-10mg of the properly ground molded exothermic agent and put it into the calibrated thermal analyzer. The heating rate is 10℃ / min and the atmosphere is air. Perform thermogravimetric and differential scanning calorimetry curve tests. Step 4: Use a thermal analyzer to generate temperature-time curves and mass-temperature curves for thermogravimetric analysis and DTG, determine the extrapolation starting temperature, take the starting temperature as the ignition temperature, take the corresponding decomposition time as the ignition time, export the data, and take the intersection of the tangent line of the falling segment of the curve and the extension line of the baseline. The temperature corresponding to the intersection of the tangent line of the falling segment of the curve and the baseline extension line is the ignition temperature, and the decomposition time corresponding to the ignition temperature is the ignition time. Step 5: Calculate the calorific value using a thermal analyzer based on the peak area of ​​the exothermic peak in the differential scanning calorimetry (DSC) curve, export the relevant data, integrate the DTC curve, and calculate the calorific value accordingly. Based on the DTC and DTG curves, the epitaxial termination temperature corresponding to the last peak of the DTC curve is taken as the maximum combustion temperature. Based on the DTC, thermogravimetric curves, and temperature-time curves, the time between the initial temperature corresponding to the highest peak and the maximum combustion temperature is taken as the duration of the exothermic reaction after secondary ignition.

2. The method for testing the performance of a die-casting exothermic agent according to claim 1, characterized in that: The rapid moisture meter uses a halogen lamp for heating, has a moisture readability of 0.01wt%, and can reach a temperature of 100-150℃. It requires periodic calibration.

3. The method for testing the performance of a molded heating agent according to claim 1, characterized in that: The pure substances In, Sn, Zn, Ag, Au, Ni, and Pd are all standard substances with a purity of over 99%.

4. The method for testing the performance of a die-casting exothermic agent according to claim 1, characterized in that: The thermal analyzer is a synchronous thermal analyzer with an operating temperature range of 25-1600℃. The thermal balance resolution can reach 0.03μg, the temperature fluctuation can reach ±0.1℃, and the temperature resolution can reach 0.1℃. The resolution, accuracy, and sensitivity of differential scanning calorimetry can all reach 0.1μW.