A method for manufacturing cast steel by suppressing casting hot cracks

Abstract

The present invention relates to a method for manufacturing cast steel for inhibiting casting hot cracks, comprising the following steps: S1: molding, manufacturing a sand mold according to a product size, and laying a temperature measuring device in the sand mold, wherein the temperature measuring device is located on the surface of the sand mold in contact with the cast steel liquid; S2: smelting, obtaining the cast steel liquid; S3: casting, casting the cast steel liquid into the sand mold; S4: after the casting is completed, applying electromagnetic induction heating to the sand mold, adjusting the intensity of the electromagnetic induction according to the surface temperature of the cast billet measured by the temperature measuring device, and controlling the cooling rate of the cast billet to be 5-10°C / h, until the cast billet surface temperature T is cooled to 0.8T. m ~0.85T m Stop electromagnetic induction heating when T m It is the melting point temperature of cast steel; S5: cooling and boxing to obtain cast steel parts.

Description

Technical Field

[0001] The invention relates to a method for manufacturing cast steel, by which the occurrence of thermal cracks in the casting process can be effectively suppressed. Background Art

[0002] Cast steel is a common material used in various mechanical structures. However, there are many casting cracks in cast steel, among which thermal cracks are the most common. Since cast steel has a wide solidification range, when the surface layer of the casting has solidified, the interior of the casting is often not completely solidified, and only many dense dendrites are formed. There is still some molten steel between these dendrites. At this time, the strength of the steel is very low, and thermal cracks are generated during the solidification shrinkage process.

[0003] Casting hot cracks are easy to distinguish, and their surface is oxidized and has no metallic luster. For steel castings, the surface of the hot cracks is almost black. On the one hand, the hot cracks of cast steel will affect the various properties of steel castings, and on the other hand, they also need to be repaired by welding. Repair welding increases manpower and process costs, and welding HAZ will also produce secondary defects or affect the performance of castings.

[0004] Therefore, inhibiting the occurrence of thermal cracks during the casting process of cast steel is crucial to improving the quality of steel castings and reducing the production process cost and labor cost of steel castings. Summary of the invention

[0005] The present invention provides a method for manufacturing cast steel capable of suppressing casting thermal cracks. The cast steel produced by the method has casting thermal cracks effectively suppressed, greatly improving the casting quality of the cast steel parts, eliminating the need for subsequent repair welding process, improving the yield of the cast steel parts, and reducing production costs and labor costs.

[0006] The technical objectives of the present invention are achieved by the following means.

[0007] The object of the present invention is to provide a method for manufacturing cast steel for suppressing casting hot cracks, comprising the following steps:

[0008] S1: molding, manufacturing a sand mold according to the product size, and laying a temperature measuring device in the sand mold, wherein the temperature measuring device is located on the surface of the sand mold in contact with the cast steel liquid;

[0009] S2: smelting to obtain molten steel;

[0010] S3: Casting, pouring the molten steel into the sand mold;

[0011] S4: After casting, electromagnetic induction heating is applied to the sand mold. According to the surface temperature of the casting billet measured by the temperature measuring device, the intensity of electromagnetic induction is adjusted to control the cooling rate of the casting billet to 5-10℃ / h until the casting billet surface temperature T is cooled to 0.8T.m ~0.85T m Stop electromagnetic induction heating when T m is the melting point temperature of cast steel;

[0012] S5: Cooling and boxing to obtain steel castings.

[0013] Next, the composition design principle of the present invention is introduced.

[0014] As described in the background technology, steel castings often have the problem of casting thermal cracks. The main reason for this problem is the difference in solidification rate, or because the solidification temperature range of cast steel is large, the part close to the sand mold (i.e., the surface of the steel casting) solidifies much faster than the core. This asynchrony of solidification leads to the generation of casting thermal cracks in steel castings.

[0015] The inventors of the present invention take the above-mentioned technical problems as the starting point, and by pre-installing a temperature measuring device in the sand mold, the temperature of the surface of the ingot can be grasped in real time. More importantly, the present invention applies electromagnetic induction heating to the sand mold after casting is completed, controls the intensity of the electromagnetic induction, and causes the ingot to cool slowly at a lower speed in the sand mold. Furthermore, the cooling speeds of the surface and core of the ingot are made close, which reduces the differences in the cooling and solidification process of different parts, and makes the cooling and solidification progress of various parts of the ingot converge during the cooling process after casting, thereby suppressing the occurrence of casting hot cracks. At the same time, the electromagnetic induction heating process will cause the cast steel liquid to generate eddy currents, thereby achieving the purpose of stirring, thereby ensuring the uniform composition of the steel billet, reducing segregation, and further suppressing the occurrence of casting hot cracks.

[0016] Based on actual production, the inventor of the present invention has determined the reasonable range of the cooling rate of the billet after casting, that is, 5-10h / ℃. If the cooling rate is too fast, the differentiation of the solidification process of different parts of the billet will increase, and the casting hot cracks cannot be effectively suppressed. Although in theory the slower the cooling rate, the better, the inventor found that the hot cracks of the steel castings finally obtained at a lower cooling rate are no different from the cooling rate of 5-10℃ / h, and no hot cracks were observed in both. The disadvantages of too low cooling rate are mainly: on the one hand, the cooling rate is too slow, which is not conducive to taking into account production efficiency; on the other hand, a lower cooling rate requires stronger electromagnetic induction to resist the temperature drop of the billet, which will cause an increase in energy consumption; more importantly, the cooling rate is too slow, causing the billet to stay in the high temperature zone for too long, which will cause the grain size of the steel casting to become larger, affecting the mechanical properties of the steel casting. On the basis of taking into account the effect of suppressing hot cracks, production efficiency, production cost and grain size, the inventor of the present invention determined that the cooling rate of the billet after casting is 5-10h / ℃.

[0017] In addition, it is also necessary to control the temperature applied when stopping electromagnetic induction heating to ensure that the occurrence of thermal cracks in steel castings is suppressed. On the one hand, if the temperature for stopping electromagnetic induction heating is too high, the ingot has not yet fully solidified. After the electromagnetic induction heating is stopped, the cooling rate of the ingot is accelerated, and the asynchronous solidification will still lead to the occurrence of thermal cracks. On the other hand, if the temperature for stopping electromagnetic induction heating is too low (that is, the electromagnetic induction heating time is too long), the ingot has been completely solidified. Excessive electromagnetic induction heating will not have further effect on improving thermal cracks in steel castings and energy consumption will increase. At the same time, if the high temperature zone of the ingot after solidification is kept warm for too long, it will cause excessive grain growth, which is not conducive to the guarantee of the mechanical properties of the ingot. The inventor comprehensively considered the effect of suppressing thermal cracks in the ingot, the energy consumption cost and the guarantee of the grain size of the ingot, and determined through experiments that the best time to stop electromagnetic induction heating is when the surface temperature of the ingot is 0.8T m ~0.85T m .

[0018] By controlling the intensity of electromagnetic induction to control the cooling rate of the ingot and controlling the timing of stopping electromagnetic induction heating, a steel casting with no casting hot cracks and an ingot grain size not less than grade 5 can be obtained.

[0019] As a further improvement, there are multiple temperature measuring devices, which are respectively arranged at different positions of the sand mold, so that the temperatures of different surfaces and different parts of the casting can be collected, thereby more accurately measuring the surface temperature of the ingot; as a non-limiting statement, the temperature measuring device can be a thermocouple, and the surface temperature of the ingot is calculated by averaging the temperatures measured by multiple thermocouples, thereby more accurately measuring and controlling the surface temperature of the ingot.

[0020] As a further improvement plan, the molten steel is sampled before casting to detect the composition of the molten steel, and T is calculated based on the composition of the molten steel. m In this way, T is calculated by analyzing the composition of the molten steel. m , which can guide the stop time of subsequent electromagnetic induction heating. As a non-limiting description, the molten steel T m The calculation can refer to the book calculation (refer to "Steelmaking Production" edited by Luo Liping and Liu Huijie, 1st edition in February 2016, first printing in February 2016, published by Metallurgical Industry Press, the calculation formula for the approximate melting point of steel recorded on pages 163-165), that is, t 熔 =1538-∑△ t · w [ i ] % -7 (Formula 1); t 熔 - Melting point of steel, ℃; 1538- Melting point of pure iron, ℃; △ t-The decrease in the melting point of pure iron when the content of a certain element increases by 1%, ℃; w [ i ] % -Steel i Mass fraction of elements; 7-It is generally believed that the gas in steel can reduce the melting point of pure iron by about 7°C; △ t This can be obtained by looking up the table in Table 5-1 on page 164 of the above book. m The value can also be calculated through other empirical formulas.

[0021] As a further improvement, step S4 specifically includes the following steps: S41: After the casting is completed, electromagnetic induction heating is applied to the sand mold, and the intensity of the electromagnetic induction is adjusted so that the temperature measured by each temperature measuring device is within T m S42: After the temperature measured by each temperature measuring device reaches the standard, adjust the intensity of electromagnetic induction and control the cooling rate of the billet to 5-10℃ / h until the billet surface temperature T is cooled to 0.8T m ~0.85T m Stop electromagnetic induction heating.

[0022] After the casting and filling of the cast steel is completed, the temperature of the molten steel drops rapidly after contacting the surface of the casting mold and solidifies to form a solidified shell. At this time, the surface temperature of the casting blank measured may not truly, objectively and accurately reflect the temperature of the entire casting blank. Therefore, the present invention adjusts the intensity of electromagnetic induction, firstly performs electromagnetic induction heating on the sand mold so that the temperatures measured by each temperature measuring device are all within T m In the above, it is preferred to control the difference between each temperature to be within 10°C, so that the solidified shell on the surface of the ingot can be filled and melted, and the molten steel liquid on the surface of the solidified shell and the unsolidified steel liquid in the core are fully mixed under the action of electromagnetic induced eddy currents, thereby ensuring the uniformity of the temperature of the ingot (molten steel) in the entire mold, ensuring accurate temperature measurement, and also ensuring uniform composition to prevent element segregation.

[0023] Of course, it is preferred to control the temperature measured by each temperature measuring device in step S41 not to be higher than the temperature during casting of cast steel. Too high a temperature is not conducive to energy consumption control on the one hand, and it is also easy to cause the molten steel to boil on the other hand. The boiling molten steel is easy to wash the sand mold, causing defects such as sand inclusion, which can directly lead to the deformation of the sand mold and the scrapping of the casting. Considering energy consumption and product qualification rate, it is preferred to control the temperature to T m ~T m +10℃.

[0024] As a further improvement, the step of preheating the sand mold is further included before step S3. By preheating the sand mold, the solidification rate of the mold surface after the molten steel is poured and filled can be reduced, so that the measured surface temperature of the ingot can more accurately reflect the actual temperature of the entire ingot in the mold.

[0025] The present invention has the following technical effects.

[0026] The present invention can grasp the temperature of the surface of the ingot in real time by pre-laying a temperature measuring device in the sand mold. After casting is completed, electromagnetic induction heating is applied to the sand mold and the intensity of the electromagnetic induction is controlled according to the temperature measured by the temperature measuring device, so that the ingot is slowly cooled at a lower speed in the sand mold, thereby making the cooling speed of the surface and the core of the ingot close to each other, reducing the difference between different parts in the cooling and solidification process, making the cooling and solidification progress of various parts of the ingot converge during the cooling process after casting, thereby suppressing the occurrence of casting hot cracks, and at the same time, eddy currents are generated in the cast steel liquid during the electromagnetic induction heating process to achieve the purpose of stirring, thereby ensuring the uniformity of the composition of the steel billet, reducing segregation, and further suppressing the occurrence of casting hot cracks. DETAILED DESCRIPTION

[0027] In order to enable ordinary technicians in the field to fully understand the technical solutions and beneficial effects of the present invention, further explanation is given below in conjunction with specific test examples.

[0028] The cast steels of the following test examples were produced according to the following method.

[0029] S1: Molding: sand molds are manufactured according to product dimensions. The sizes of cast steel in this test example are all rectangular (ingot length is 800 mm, width is 400 mm, height is 400 mm). Quartz sand is used for molding and bonded with clay. Six thermocouples are laid in each sand mold, corresponding to the center position of each surface of the rectangular body of the cast steel billet; and the thermocouples are laid on the surface of the sand mold that contacts the cast steel liquid.

[0030] S2: According to the target composition, the materials are prepared and smelted to obtain molten steel. The composition of the molten steel is tested before casting and listed in Table 1. The melting point T of the cast steel is calculated according to the tested composition using the above formula 1. m (℃), listed in Table 2.

[0031] S3: Casting: pouring the molten steel into sand molds. Each furnace of molten steel is used to cast 6 sand molds.

[0032] S41: After the casting is completed, electromagnetic induction heating is applied to each sand mold, and the intensity of electromagnetic induction is adjusted so that the temperature measured by each thermocouple is within T m ~T m +5℃ range.

[0033] S42: After the temperature measured by each thermocouple reaches the standard, the intensity of electromagnetic induction is adjusted to control the cooling rate of the ingot to V, until the ingot is cooled to the average temperature measured by each thermocouple, that is, the surface temperature of the ingot is T, and then the electromagnetic induction heating is stopped. V (℃ / h) and T (℃) of each test example are shown in Table 2.

[0034] S5: Cooling and boxing to obtain steel castings.

[0035] Table 1: Composition of various cast steels, %, the remainder is Fe.

[0036]

[0037] During the cooling process, the six steel castings with test number i (i is 1-4) were subjected to different cooling rates V (℃ / h) and electromagnetic induction heating stop temperatures T (℃), which were recorded as i-1-i-6, respectively, and are recorded in Table 2. The hot cracks of the obtained steel castings were observed under a microscope at a magnification of 100X, and the grain size of each steel casting was determined by the straight line intercept method in the determination method of the average grain size of metals in GB / T6394-2017, and the results are recorded in Table 2.

[0038] Table 2: Melting point, cooling process parameters and test results of various steels.

[0039]

[0040] The above embodiments and comparative examples are further analyzed and explained below in conjunction with Table 2.

[0041] The cooling rates and electromagnetic induction heating stop temperatures of test numbers 1-1, 1-2, 2-1, 2-2, 3-1, 3-2, 4-1, and 4-2 in Table 2 all meet the requirements of the present invention, and the steel castings finally obtained have no thermal cracks after inspection, and the grain size can reach 5 or more, which meets the requirements of the invention. The above test numbers are embodiments of the present invention. The cooling rates and / or electromagnetic induction heating stop temperatures of test numbers 1-3, 1-4, 1-5, 1-6, 2-3, 2-4, 2-5, 2-6, 3-3, 3-4, 3-5, 3-6, 4-3, 4-4, 4-5, and 4-6 do not meet the requirements of the present invention, and steel castings without thermal cracks and with a grain size of 5 or more cannot be obtained.

[0042] Below, the above comparative examples are specifically analyzed.

[0043] Comparative Examples 1-3 have the same cast steel composition as Examples 1-2, and the electromagnetic induction heating stop temperature is also the same, both of which are within the scope of the present invention. However, since the cooling rate is too low, it is not within the scope of the present invention. Although the final castings have no thermal cracks, the cooling rate is too low and the castings stay in the high temperature zone for too long, resulting in excessive grain growth, which cannot meet the requirement of the present invention for a cast steel grain size of more than level 5.

[0044] Comparative Examples 1-4 have the same cast steel composition as Examples 1-2, and the electromagnetic induction heating stop temperature is also the same, both of which are within the scope of the present invention. However, due to their excessively high cooling rates, they are not within the scope of the present invention. Although the resulting cast steel has a higher grain size, the cooling rate is too high, resulting in a large temperature gradient during the solidification of the cast steel, and a greater difference in the solidification progress of different parts, which results in thermal cracks in the resulting cast steel.

[0045] Comparative Example 1-5 has the same cast steel composition and cooling rate as Example 1-1, both of which are within the required range of the present invention. However, since the stop temperature of the electromagnetic induction heating is too low, it is not within the scope of the present invention. Although the final casting has no thermal cracks, since the stop temperature of the electromagnetic induction heating is too low, the casting stays in the high temperature zone for too long, resulting in excessive grain growth, and the requirement of the present invention for a cast steel grain size of more than level 5 cannot be met.

[0046] Comparative Example 1-6 has the same cast steel composition and cooling rate as Example 1-1, both of which are within the required range of the present invention. However, since the stop temperature of the electromagnetic induction heating is too high, it is not within the scope of the invention. Although the final cast billet has a higher grain size grade, the stop temperature of the electromagnetic induction heating is too high and the cast billet has not yet fully solidified. After the electromagnetic induction heating is stopped, the cooling rate of the cast billet is accelerated, and the asynchronous solidification will still lead to the occurrence of hot cracks in the cast steel.

[0047] Comparative Example 2-3 has the same cast steel composition as Example 2-1, and the electromagnetic induction heating stop temperature is also the same, both of which are within the scope of the present invention. However, since its cooling rate is too low, it is not within the scope of the present invention. Although the final casting has no thermal cracks, the cooling rate is too low and the casting stays in the high temperature zone for too long, resulting in excessive grain growth, which cannot meet the requirement of the present invention for a cast steel grain size of more than level 5.

[0048] Comparative Example 2-4 has the same cast steel composition as Example 2-1, and the electromagnetic induction heating stop temperature is also the same, both of which are within the scope of the present invention. However, due to its excessively high cooling rate, it is not within the scope of the present invention. Although the final cast steel has a higher grain size grade, due to the excessively high cooling rate, the temperature gradient is large during the solidification process of the cast steel, and the difference in solidification progress in different parts increases, resulting in thermal cracks in the final cast steel.

[0049] Comparative Example 2-5 has the same cast steel composition and cooling rate as Example 2-1, both of which are within the required range of the present invention. However, since the stop temperature of the electromagnetic induction heating is too low, it is not within the scope of the present invention. Although the final casting has no thermal cracks, since the stop temperature of the electromagnetic induction heating is too low, the casting stays in the high temperature zone for too long, resulting in excessive grain growth, and the requirement of the present invention for the cast steel grain size to be above level 5 cannot be met.

[0050] Comparative Example 2-6 has the same cast steel composition and cooling rate as Example 2-1, both of which are within the required range of the present invention. However, since the stop temperature of the electromagnetic induction heating is too high, it is not within the scope of the invention. Although the final cast billet has a higher grain size grade, since the stop temperature of the electromagnetic induction heating is too high, the cast billet has not yet fully solidified. After the electromagnetic induction heating is stopped, the cooling rate of the cast billet is accelerated, and the asynchronous solidification will still lead to the occurrence of hot cracks in the cast steel.

[0051] The cast steel composition of Comparative Example 3-3 is the same as that of Examples 3-1 and 3-2. Its electromagnetic induction heating stop temperature is too low and its cooling rate is too low, both of which are outside the scope of the invention. Although the final casting has no thermal cracks, due to the too low cooling rate and the too low electromagnetic induction heating stop temperature, the casting stays in the high temperature zone for too long, resulting in excessive grain growth, which cannot meet the requirement of the present invention for the cast steel grain size of above level 5.

[0052] The cast steel composition of Comparative Example 3-4 is the same as that of Examples 3-1 and 3-2. The electromagnetic induction heating stop temperature is too high and the cooling rate is too high, both of which are not within the scope of the invention. Although the final cast billet has a higher grain size grade, due to the excessively high cooling rate, the temperature gradient is large during the solidification process of the cast billet, and the differentiation of solidification progress in different parts increases. In addition, the electromagnetic induction heating stop temperature is too high, and the cast billet has not yet fully solidified. After the electromagnetic induction heating is stopped, the cooling rate of the cast billet is accelerated, and the solidification is asynchronous, resulting in thermal cracks in the final cast steel.

[0053] Comparative Example 3-5 has the same cast steel composition and cooling rate as Example 3-2, both of which are within the required range of the present invention. However, since the stop temperature of the electromagnetic induction heating is too low, it is not within the scope of the invention. Although the final casting has no thermal cracks, since the stop temperature of the electromagnetic induction heating is too low, the casting stays in the high temperature zone for too long, resulting in excessive grain growth, and the requirement of the present invention for the cast steel grain size to be above level 5 cannot be met.

[0054] Comparative Example 3-6 has the same cast steel composition and cooling rate as Example 3-2, both of which are within the required range of the present invention. However, since the stop temperature of electromagnetic induction heating is too high, it is not within the scope of the invention. Although the final cast billet has a higher grain size grade, since the stop temperature of electromagnetic induction heating is too high, the cast billet has not yet fully solidified. After the electromagnetic induction heating is stopped, the cooling rate of the cast billet is accelerated, and the asynchronous solidification will still lead to the occurrence of hot cracks in the cast steel.

[0055] Comparative Example 4-3 has the same cast steel composition as Example 4-1, and the electromagnetic induction heating stop temperature is also the same, both of which are within the scope of the present invention. However, since its cooling rate is too low, it is not within the scope of the present invention. Although the final casting has no thermal cracks, the cooling rate is too low and the casting stays in the high temperature zone for too long, resulting in excessive grain growth, which cannot meet the requirement of the present invention for a cast steel grain size of more than level 5.

[0056] Comparative Example 4-4 has the same cast steel composition as Example 4-1, and the electromagnetic induction heating stop temperature is also the same, both of which are within the scope of the present invention. However, due to its excessively high cooling rate, it is not within the scope of the present invention. Although the final cast steel has a higher grain size grade, the cooling rate is too high, the temperature gradient is large during the solidification process of the cast steel, and the difference in solidification progress in different parts increases, resulting in thermal cracks in the final cast steel.

[0057] Comparative Example 4-5 has the same cast steel composition as Examples 4-1 and 4-2, and its electromagnetic induction heating stop temperature is too high and its cooling rate is too low, both of which are not within the scope of the invention. Due to its too low cooling rate, the billet stays in the high temperature zone for too long, resulting in excessive grain growth, which cannot meet the requirement of the cast steel grain size of more than 5 levels of the present invention; and, due to the too high electromagnetic induction heating stop temperature, the billet has not yet fully solidified, and the billet cooling rate is accelerated after the electromagnetic induction heating is stopped, and the solidification is not synchronized, resulting in thermal cracks in the final cast steel.

[0058] Comparative Example 4-6 has the same cast steel composition as Examples 4-1 and 4-2, but its electromagnetic induction heating stop temperature is too low and its cooling rate is too high, which are not within the scope of the invention. Due to its high cooling rate, the temperature gradient is large during the solidification of the ingot, and the difference in the solidification progress of different parts is increased, resulting in thermal cracks in the final cast steel; and, due to the low electromagnetic induction heating stop temperature, the ingot stays in the high temperature zone for too long, resulting in excessive growth of the grains, which cannot meet the requirements of the cast steel grain size of 5 or above of the present invention.

[0059] From the above, it is not difficult to see that the present invention controls the cooling rate of the cast steel billet within a certain temperature range by applying electromagnetic induction heating, and controls the stop time of the electromagnetic induction heating, and finally obtains a cast steel billet without thermal cracks and with a grain size of 5 or above, ensuring that cast steel parts with excellent casting quality and performance are obtained.

[0060] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0061] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for manufacturing cast steel for suppressing casting hot cracks, characterized in that: The steps include: S1: molding, manufacturing a sand mold according to the product size, and laying a temperature measuring device in the sand mold, wherein the temperature measuring device is located on the surface of the sand mold in contact with the cast steel liquid; S2: smelting to obtain molten steel; S3: Casting, pouring the molten steel into the sand mold; S4: After casting, electromagnetic induction heating is applied to the sand mold. According to the surface temperature of the casting billet measured by the temperature measuring device, the intensity of electromagnetic induction is adjusted to control the cooling rate of the casting billet to 5-10℃ / h until the casting billet surface temperature T is cooled to 0.8T. m ~0.85T m Stop electromagnetic induction heating when T m is the melting point temperature of cast steel; S5: Cooling and boxing to obtain steel castings.

2. A method for manufacturing cast steel for suppressing casting hot cracks according to claim 1, characterized in that: There are multiple temperature measuring devices, which are respectively arranged at different positions of the sand mold.

3. The method for manufacturing cast steel for suppressing casting hot cracks according to claim 1, characterized in that: The temperature measuring device is a thermocouple.

4. The method for manufacturing cast steel for suppressing casting hot cracks according to claim 1, characterized in that: The surface temperature of the casting strand is calculated by averaging the temperatures measured by a plurality of thermocouples.

5. The method for manufacturing cast steel for suppressing casting hot cracks according to claim 1, characterized in that: It also includes sampling the molten steel before casting to detect the composition of the molten steel, and calculating T based on the composition of the molten steel. m steps.

6. The method for manufacturing cast steel for suppressing casting hot cracks according to claim 1, characterized in that: Step S4 specifically includes the following steps: S41: After the casting is completed, electromagnetic induction heating is applied to the sand mold, and the intensity of the electromagnetic induction is adjusted so that the temperature measured by each temperature measuring device is within T m above; S42: After the temperatures measured by the temperature measuring devices meet the standards, the intensity of electromagnetic induction is adjusted to control the cooling rate of the ingot to 5-10°C / h until the surface temperature T of the ingot is within 0.8T. m ~0.85T m Stop electromagnetic induction heating.

7. The method for manufacturing cast steel for suppressing casting hot cracks according to claim 1, characterized in that: Before step S3, a step of preheating the sand mold is also included.

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