A method for controlling the casting speed of steel casting by mold casting method

Abstract

A method for controlling the casting speed of steel casting by a die casting pouring method belongs to the technical field of die casting production technology in the metallurgical industry and is used to reasonably control the casting speed of steel casting by a die casting pouring method. The technical solution is: a temperature measurement blind hole is opened on the lower side of the ingot mold wall, and two temperature measurement points are formed at different depths along the radial direction. The temperature of the ingot mold wall is continuously and accurately detected during the casting process, and the temperature of the molten steel in the mold is calculated with a delay, thereby adjusting the casting speed of the molten steel in the ladle, controlling the temperature of the molten steel in the ingot mold, and finally achieving uniform solidification of the molten steel, avoiding looseness and shrinkage of the ingot. The present invention is the first of its kind in the die casting pouring method for steel casting, and solves the current urgent problems of timely mastering the temperature measurement of the molten steel pouring process in the ingot mold, monitoring the temperature changes during the entire casting period, and realizing automatic control of the size of the ladle steel flow and the casting speed, providing a reliable technical guarantee for the continuous production of high-quality ingots.

Description

Technical Field

[0001] The invention relates to a method for controlling the casting speed of steel casting by a die casting pouring method, and belongs to the technical field of die casting production process control in the metallurgical industry. Background Art

[0002] The pouring method is widely used in China for large-scale mold-cast steel ingots. During the pouring method, the molten steel enters the lower part of the ingot mold from the soup channel and spreads upward in the center, so the center area and the sub-center area are in liquid or paste state, and the center area solidifies last. The current casting speed of the molten steel is reflected by the change of the ladle scale per unit time and is controlled by a manual hydraulic switch. If the pouring speed is not properly controlled, it will cause uneven solidification of the molten steel, resulting in looseness and shrinkage of the ingot. So far, there is no method to automatically control the ladle pouring speed by monitoring the temperature change of the molten steel in the ingot mold, and it cannot guarantee the continuous production of high-quality ingots. Therefore, it is a problem that needs to be solved at present to timely grasp the measurement of the temperature of the molten steel pouring process in the ingot mold, monitor the temperature change during the entire casting period, and realize automatic control of the ladle steel flow size and pouring speed. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for controlling the casting speed of steel casting by the mold casting pouring method. This control method can grasp the temperature change of the molten steel in the ingot mold during the casting process, and then control the casting speed, thereby improving the internal quality of the ingot.

[0004] The technical solution to solve the above technical problems is:

[0005] A method for controlling the casting speed of steel casting by a mold casting pouring method, which is carried out by the following steps:

[0006] a. Open a temperature measuring blind hole on the lower side of the ingot mold wall, set a temperature measuring point in front and behind the temperature measuring blind hole, place temperature measuring thermocouples at the two temperature measuring points, the two temperature measuring points are at the same height as the bottom surface of the ingot mold, and the distances between the two temperature measuring points and the inner wall of the ingot mold are different;

[0007] b. The temperature of the molten steel in the ingot mold is calculated by the temperature measurement values ​​of two temperature measuring thermocouples. The calculation formula is as follows:

[0008] T 计算 =(T 1 -T 2 )×L 1 / L 2 +T 1

[0009] in,

[0010] T 1 is the measured temperature value of the first temperature measuring point;

[0011] T 2 is the measured temperature value of the second temperature measuring point;

[0012] T 计算 is the calculated temperature of the molten steel in the ingot mold;

[0013] L 1 is the distance between the first temperature measuring point and the inner wall of the ingot mold;

[0014] L 2 is the distance between the second temperature measuring point and the inner wall of the ingot mold;

[0015] c. Introduce the correction factor K and calculate the real-time temperature of the molten steel in the ingot mold as follows:

[0016] T 钢水 =K×[(T 1 -T 2 )×L 1 / L 2 +T 1 ]

[0017] Where K is the correction factor;

[0018] T 钢水 is the temperature of the molten steel in the ingot mold;

[0019] d. Based on the above-mentioned measurement and calculation of the molten steel temperature in the ingot mold, the opening degree of the hydraulic control slide brick is controlled through the hydraulic control pipeline system, and finally the steel pouring speed is controlled.

[0020] In the above-mentioned method for controlling the casting speed of steel casting by the mold casting pouring method, there is an angle of 20-30 degrees between the two temperature measuring points in step a and the line connecting the center of the ingot mold, and the outside of the temperature measuring points is kept warm.

[0021] In the above-mentioned method for controlling the casting speed of steel casting by the mold casting pouring method, the correction coefficient K in step c is obtained by the following method: using an inserted thermocouple to perform temperature measurements at different time points for multiple times, and calculating the molten steel temperature at the corresponding time nodes, and obtaining the correction coefficient K by the ratio of the measured value to the calculated value.

[0022] The beneficial effects of the present invention are:

[0023] The present invention opens a temperature measuring blind hole on the lower side of the ingot mold wall, and forms two temperature measuring points arranged at different depths along the radial direction. The temperature of the ingot mold wall is continuously and accurately detected during the casting process, and the temperature of the molten steel in the mold is calculated with a delay, so as to adjust the casting speed of the molten steel in the ladle and control the temperature of the molten steel in the ingot mold, ultimately achieving uniform solidification of the molten steel and avoiding looseness and shrinkage of the ingot.

[0024] The present invention is the first of its kind in the steel casting process using the mold casting pouring method. It solves the current urgent problems of timely measuring the temperature of the molten steel in the ingot mold during the pouring process, monitoring the temperature changes during the entire casting period, and realizing automatic control of the size of the steel flow in the ladle and the pouring speed. It provides technical support for the continuous production of high-quality ingots and is worthy of promotion and use in the industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a cross-sectional view of the mold casting of the present invention;

[0026] Figure 2 3D view of steel pouring and temperature control;

[0027] Figure 3 This is the layout diagram of the thermocouple for measuring the temperature of the ingot mold;

[0028] Figure 4 This is the simulation diagram of heat conduction temperature of ingot mold;

[0029] Figure 5 The temperature variation with time of the selected point for the temperature measurement of the ingot mold part;

[0030] Figure 6 This is a comparison chart of the temperature calculated by temperature measurement in Example 1 and the actual measured temperature;

[0031] Figure 7 This is a comparison chart between the temperature calculated by temperature measurement and the actual measured temperature.

[0032] The markings in the figure are as follows: ladle 1, water inlet 2, hydraulic control slide brick 3, water outlet 4, hydraulic control pipeline 5, control unit 6, temperature display unit 7, first temperature measuring point 8, second temperature measuring point 9, steel pouring channel 10, center pouring pipe 11, ingot mold 12, cap mouth 13. DETAILED DESCRIPTION

[0033] The present invention continuously and accurately detects the temperature of the ingot mold wall during the casting process, and synchronously calculates the real-time temperature of the molten steel in the casting mold, thereby adjusting the casting speed of the molten steel in the ladle to open-loop control the temperature of the molten steel in the ingot mold, ultimately achieving uniform solidification of the molten steel and avoiding loosening and shrinkage of the ingot.

[0034] Figure 1 , 2 It is shown that during the casting process of the mold casting pouring method, the molten steel passes through the upper water inlet 2, the hydraulic control slide brick 3, the lower water inlet 4, the cap mouth 13, the middle pouring pipe 11, and the steel pouring channel 10 in sequence from the ladle 1, and finally enters the evenly arranged ingot mold 12, wherein the number and size of the ingot molds 12 are determined according to the weight of the molten steel in the ladle, and a U-shaped tube structure interconnected by the steel pouring channel 10 is formed between the multiple ingot molds 12, the molten steel levels keep rising synchronously, and the temperature of the molten steel in the multiple ingot molds 12 remains basically consistent.

[0035] The present invention adds a control unit 6 for collecting temperature data measured at different measuring points of the ingot mold 12, and after sorting and calculating, displays the temperature of the molten steel in the ingot mold 12 on the temperature display unit 7, and further controls the opening of the hydraulic control slide brick 3 through the hydraulic control pipeline 5 based on this temperature, and finally controls the steel pouring speed.

[0036] The present invention takes the following steps:

[0037] The first step is to set the temperature measurement point.

[0038] A temperature measuring blind hole is opened on the lower side of the ingot mold 12 wall, and a temperature measuring point is set in the front and back of the temperature measuring blind hole, which are the first temperature measuring point 8 and the second temperature measuring point 9 respectively. Temperature measuring thermocouples are placed in the first temperature measuring point 8 and the second temperature measuring point 9 respectively. The first temperature measuring point 8 and the second temperature measuring point 9 are at the same height as the bottom surface of the ingot mold 12. The first temperature measuring point 8 and the second temperature measuring point 9 are at different distances from the inner wall of the ingot mold 12. There is an angle of 20-30 degrees between the first temperature measuring point 8 and the second temperature measuring point 9 and the center line of the ingot mold 12.

[0039] In the second step, the temperature of the molten steel in the ingot mold 12 is calculated by the temperature measurement values ​​of the two temperature measuring thermocouples.

[0040] Since the distance difference between the two temperature measuring thermocouples and the center of the steel ingot mold 12 is much smaller than the distance between the two temperature measuring thermocouples and the center of the steel ingot mold 12, for the sake of simplicity of calculation, the distance difference between the two temperature measuring thermocouples and the center of the steel ingot mold is ignored, and the heat transfer value Q1≈Q2 is taken, the following formula can be obtained:

[0041] Q1=λ×(T 钢水 -T 1 ) / L 1

[0042] Q2=λ×(T 1 -T 2 ) / L 2

[0043] Wherein, Q1 is the heat transfer from the molten steel in the ingot mold 12 to the first temperature measuring point 8;

[0044] Q2 is the heat transferred from the first temperature measuring point 8 to the second temperature measuring point 9 in the ingot mold 12;

[0045] λ is the heat transfer coefficient of the ingot mold;

[0046] T 1 is the measured temperature value of the first temperature measuring point 8;

[0047] T 2 is the measured temperature value of the second temperature measuring point 9;

[0048] T钢水 is the temperature of the molten steel in the ingot mold 12;

[0049] L 1 is the distance between the first temperature measuring point 8 and the inner wall of the ingot mold 12;

[0050] L 2 is the distance between the second temperature measuring point 9 and the inner wall of the ingot mold 12;

[0051] After derivation, we get:

[0052] T 计算 =(T 1 -T 2 )×L 1 / L 2 +T 1

[0053] The third step is to introduce the correction coefficient K to calculate the real-time temperature of the molten steel in the ingot mold.

[0054] Since the conductivity coefficient of the ingot mold 12 material is relatively large, after the molten steel enters the ingot mold 12 through the steel pouring channel 10, the ingot mold 12 begins to heat up rapidly near the temperature measuring point. After about 7-10 minutes, a balanced steady state is reached through the heat transfer of the newly flowing molten steel in the ingot mold 12 and the heat dissipated by the ingot mold 12 to the surrounding air, that is, Q1≈Q2.

[0055] In the present invention, the error factors such as the conversion of different thermal conductivities between the molten steel and the protective slag, the protective slag and the air gap, the air gap and the inner wall of the ingot mold 12, the approximate consistency of the thermal equilibrium steady state, and the introduction of the correction coefficient K due to the hysteresis of the thermal conductivity of the ingot mold are considered, and the corrected formula is finally formed as follows:

[0056] T 钢水 =K×[(T 1 -T 2 )×L 1 / L 2 +T 1 ]

[0057] The above correction is made in consideration of the influence of the heat transfer time of the steel ingot mold 12. The real-time temperature of the molten steel in the steel ingot mold 12 cannot be measured. It is similar to the logic that the light received on the earth is the light received by the sun eight minutes ago. The temperature measured on the steel ingot mold 12 is the molten steel data n minutes before the measurement time, and the temperature is corrected by the correction coefficient. Considering the control timeliness, the control unit 6 of the present invention preferably uses 15 minutes as the control time node, that is, after 15 minutes of mold casting, the temperature of each temperature measurement point reaches stability, such as Figure 5 The simulation temperature is shown in Figure 6 It shows how fast the temperature of the temperature measuring points at different distances reaches stability. Through the above corrected formula, a more accurate temperature of the molten steel in the ingot mold can be obtained.

[0058] In the present invention, the correction coefficient K is obtained by the following method: using an inserted thermocouple to measure the temperature at different time points for multiple times, and calculating the molten steel temperature at the corresponding time nodes, and obtaining the correction coefficient K through the ratio of the measured value and the calculated value.

[0059] The fourth step is to control the steel pouring speed.

[0060] According to the temperature of the molten steel in the ingot mold 12 obtained by the above measurement and calculation, the opening degree of the hydraulic control slide brick 3 is controlled through the hydraulic control pipeline 5, and finally the steel pouring speed is controlled.

[0061] The present invention controls the temperature of the molten steel in the ingot mold 12 by adjusting the casting speed of the molten steel in the ladle, so as to achieve uniform and stable temperature of the molten steel in the ingot, and finally achieve uniform solidification of the molten steel, thereby avoiding looseness and shrinkage of the ingot.

[0062] The above-mentioned method for measuring and calculating the molten steel temperature in the ingot mold 12 also includes an empirical data curve for multi-furnace big data collection and analysis of the temperature values ​​measured at the temperature measuring points. After a simple comparison of the cast-in-place furnaces, the difference between the molten steel temperature value and the molten steel temperature value of the empirical casting is timely analyzed.

[0063] The temperature measurement method at the temperature measurement point of the present invention can adopt various temperature measurement methods such as thermocouple and induction temperature measurement. In the preferred embodiment, a temperature measuring thermocouple can be used for temperature measurement, and the temperature measurement accuracy of the temperature measurement point can be controlled within ±3°C, and the calculated temperature can be controlled within ±15°C.

[0064] The measured temperature value at the first temperature measuring point 8 of the present invention also carries out big data collection and analysis of multiple furnaces. After simple comparison, the difference between the molten steel temperature value and the empirical casting temperature value is timely analyzed. When the deviation is large, real-time adjustment can be made.

[0065] Example 1

[0066] In the implementation of temperature measurement of a 42-ton ingot mold in a mold casting plant to produce mold steel 1.2738, the temperature measurement method of the present invention was used to control the steel pouring speed, and the entire pouring cycle was 65 minutes.

[0067] The wall thickness of the steel ingot mold 12 is 300mm. A 200mm deep temperature measurement blind hole is opened at 200mm from the bottom of the ingot mold. The blind hole opening diameter is φ40mm. The first temperature measurement point 8 is arranged 100mm away from the inner wall, and the second temperature measurement point 9 is arranged 150mm away from the inner wall, forming a 30-degree angle with the first temperature measurement point 8 in the horizontal direction to avoid mutual influence. The outer side of the temperature measurement point is insulated to reduce the influence of the opening on normal heat conduction or radiation.

[0068] The temperature measuring circuit is connected to the control unit by a plug-in circuit. When the steel ingot mold 12 is demoulded, the circuit is coiled, fixed and protected, so as not to affect the demoulding and other operations.

[0069] According to the specific production process of a factory producing die steel 1.2738, an inserted thermocouple was used to measure the temperature at different time points for many times. At the same time, the molten steel temperature was calculated at the corresponding time nodes. The correction coefficient K was obtained by the ratio of the measured value to the calculated value.

[0070]

[0071] When the same steel grade is subsequently cast, the temperature calculated by temperature measurement is compared with the actual temperature. Figure 6 .

[0072] In this embodiment, the fitted K value curve is used to monitor and verify the temperature of mold steel 1.2738 with the same subsequent process conditions and different casting temperatures. The calculated temperature is compared with the measured temperature of the inserted thermocouple, and the temperature control accuracy is within ±5°C, as shown in the following table.

[0073]

[0074] When measuring the second furnace, the measured temperature showed that the temperature was lower than the empirical value. The opening of the casting mouth was increased, and finally qualified organizational properties were obtained.

[0075] Example 2

[0076] In the implementation of temperature measurement of 9Cr2Mo mold steel produced by a 39-ton ingot mold in a certain mold casting plant, the temperature measurement method of the present invention was used to control the steel pouring speed, and the entire pouring cycle was 72 minutes.

[0077] The wall thickness of the steel ingot mold 12 is 300mm. A 200mm deep temperature measurement blind hole is opened at 200mm from the bottom of the ingot mold. The blind hole opening diameter is φ40mm. The first temperature measurement point 8 is arranged 100mm away from the inner wall, and the second temperature measurement point 9 is arranged 150mm away from the inner wall, forming a 30-degree angle with the first temperature measurement point 8 in the horizontal direction to avoid mutual influence. The outer side of the temperature measurement point is insulated to reduce the influence of the opening on normal heat conduction or radiation.

[0078] The temperature measuring circuit is connected to the control unit by a plug-in circuit. When the steel ingot mold 12 is demoulded, the circuit is coiled, fixed and protected, so as not to affect the demoulding and other operations.

[0079] According to the specific production process of a factory producing die steel 9Cr2Mo, an inserted thermocouple was used to measure the temperature at different time points for many times. At the same time, the molten steel temperature was calculated at the corresponding time nodes. The correction coefficient K was obtained by the ratio of the measured value to the calculated value.

[0080]

[0081] When the same steel grade is subsequently cast, the temperature calculated by temperature measurement is compared with the actual temperature. Figure 7 .

[0082] In this embodiment, the fitted K value curve is used to monitor and verify the temperature of the mold steel 9Cr2Mo with the same subsequent process conditions and different casting temperatures. The calculated temperature is compared with the measured temperature of the inserted thermocouple, and the temperature control accuracy is within ±7°C, as shown in the following table.

[0083]

[0084]

[0085] When measuring the first and second furnaces, the measured temperature showed that the temperature was higher than the empirical value, and the opening of the casting mouth was reduced, and finally qualified organizational properties were obtained.

Claims

1. A method for controlling the casting speed of steel casting by a die casting pouring method, characterized in that: It proceeds in the following steps: a. A temperature measuring blind hole is opened on the lower side of the ingot mold (12) wall, and a temperature measuring point is set in front and behind the temperature measuring blind hole, and a temperature measuring thermocouple is placed at the two temperature measuring points, and the two temperature measuring points are equidistant from the bottom surface of the ingot mold (12), and the distances between the two temperature measuring points and the inner wall of the ingot mold (12) are different; b. The temperature of the molten steel in the ingot mold (12) is calculated by the temperature measurement values ​​of the two temperature measuring thermocouples. The calculation method formula is as follows: T 计算 =(T1-T2)×L1 / L2+ T1 in, T1 is the measured temperature value of the first temperature measurement point (8); T2 is the measured temperature value of the second temperature measuring point (9); T 计算 is the temperature of the molten steel in the ingot mold (12); L1 is the distance between the first temperature measuring point (8) and the inner wall of the ingot mold; L2 is the distance between the second temperature measuring point (9) and the inner wall of the ingot mold; c. Introduce the correction factor K and calculate the real-time temperature of the molten steel in the ingot mold as follows: T 钢水 =K×[(T1-T2)×L1 / L2 + T1] Where K is the correction factor; The correction coefficient K is obtained by the following method: using an inserted thermocouple to measure the temperature at different time points for many times, and calculating the temperature of the molten steel at the corresponding time nodes, and obtaining the correction coefficient K by the ratio of the measured value to the calculated value; d. Based on the above-mentioned measured and calculated temperature of the molten steel in the ingot mold, the opening degree of the hydraulic control slide brick (3) is controlled through the hydraulic control pipeline (5), and finally the steel pouring speed is controlled.

2. The method for controlling the casting speed of steel casting by the mold casting pouring method according to claim 1, characterized in that: There is an angle of 20-30 degrees between the two temperature measuring points in step a and the center line of the steel ingot mold (12), and the outside of the temperature measuring points is kept warm.

Images