Method for improving surface quality of cast ingot

Abstract

The invention discloses a method for improving the surface quality of a cast ingot to solve the problem of serious surface oxidation of the cast ingot, and provides a method for adding a slow cooling process to the cast ingot after casting to effectively reduce the surface oxidation degree of the cast ingot, and after molten steel casting, standing an ingot mold in a hearth of a vacuum induction furnace for pressure maintaining, and slowly cooling along with the furnace for a certain time, and demolding after the temperature of the cast ingot is reduced to a relatively low temperature, so that oxidation on the surface of the cast ingot can be effectively reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of metal smelting, and in particular relates to a method for improving the surface quality of ingots. Background Art

[0002] The surface quality of ingots is one of the important indicators for evaluating the quality of ingots, which directly affects the subsequent processing performance and finished product quality of ingots. The surface quality of ingots is not only related to the appearance of ingots, but also directly affects its internal quality, processing performance and the quality of the final product. Therefore, in the casting process, strict control of the surface quality of ingots is the key to ensure the quality of finished products. There are many factors that affect the surface quality of ingots, such as casting speed, casting temperature, mold temperature, mold heat transfer rate, etc.

[0003] At present, after the test steel is cast using a metal mold during laboratory pilot smelting, the surface quality of the ingot is average, the surface oxide scale is thick, and it is not easy to fall off. During subsequent hot rolling, it will remain on the surface of the steel plate, seriously affecting the quality of the test sample, and thus affecting the test results. Summary of the invention

[0004] In order to overcome the shortcomings of existing test steel ingots, that the oxide scale on the surface is thick and not easy to fall off, and will remain on the surface of the steel plate during hot rolling, seriously affecting the quality of the test sample, the purpose of the present invention is to provide a method for improving the surface quality of the ingot.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for improving the surface quality of an ingot, comprising the following steps:

[0007] ①Put the weighed pure iron raw material into the crucible of the vacuum induction furnace, put the alloys to be added into the alloy tank, put in the ingot mold and riser brick, and close the vacuum furnace cover;

[0008] ② Turn on the cooling water of the vacuum induction furnace and the control cabinet, start the Roots pump to pump the air in the induction furnace to below 40Pa, then fill it with argon to 0.5-0.7 standard atmospheric pressure, first heat at low power for 5-10 minutes, then gradually increase the power to heat until all the raw materials are melted, then deoxidize and alloy, maintain for a certain period of time to promote uniform distribution of the alloy, slowly pour the molten steel into the ingot mold, and stop heating;

[0009] ③ Place the cast ingot mold in the vacuum induction furnace to maintain pressure, take 50-80 minutes of slow cooling time with the furnace, then open the vacuum furnace cover, lift out the ingot mold, demould, and check the surface quality of the ingot;

[0010] ④Hot-roll the ingot and check the surface quality of the steel plate.

[0011] Furthermore, the Roots pump is started to evacuate the air in the induction furnace to below 40Pa, and then argon gas is filled in to 0.5 standard atmospheric pressure.

[0012] Furthermore, the Roots pump is started to evacuate the air in the induction furnace to below 40 Pa, and then argon gas is filled in to 0.6 standard atmospheric pressure.

[0013] Furthermore, the Roots pump is started to evacuate the air in the induction furnace to below 40 Pa, and then argon gas is filled in to 0.7 standard atmospheric pressure.

[0014] Furthermore, a slow cooling time of 60-70 minutes is adopted.

[0015] Furthermore, a 60-min slow cooling time is adopted.

[0016] Furthermore, after slow cooling for 60 minutes, the temperature of the ingot is lower than 100°C, the degree of oxidation on the surface of the ingot is small, the oxide scale is very thin, and the surface is smooth.

[0017] Furthermore, after the ingot was rolled with slow cooling for 60 minutes, the surface quality of the steel plate was the smoothest, and when sampling for physical property inspection was performed, less waste was produced and the plate utilization rate was higher.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are:

[0019] The present invention places the cast ingot in the furnace of a vacuum induction furnace to maintain pressure, slowly cools it with the furnace for a certain period of time, and then demoulds it after the temperature of the ingot drops to a relatively low temperature, thereby effectively reducing the oxidation degree of the ingot surface and improving the surface quality of the ingot. DETAILED DESCRIPTION

[0020] Example 1

[0021] A method for improving the surface quality of an ingot, comprising the following steps:

[0022] ① Place the weighed pure iron raw material in the crucible of the vacuum induction furnace, put the alloys to be added in the alloy tank, put in the ingot mold and riser brick, and close the vacuum furnace cover.

[0023] ② Turn on the cooling water of the vacuum induction furnace and the control cabinet, start the Roots pump to pump the air in the induction furnace to below 40Pa, and then fill it with argon to 0.6 standard atmospheric pressure. First heat at low power for 8 minutes, and then gradually increase the power to heat until all the raw materials are melted, then deoxidize and alloy, maintain a certain time to promote uniform distribution of the alloy, slowly pour the molten steel into the ingot mold, and stop heating.

[0024] ③ Place the ingot mold after casting in the vacuum induction furnace to maintain pressure, take 60 minutes of slow cooling time, then open the vacuum furnace cover, lift out the ingot mold, demould, and check the surface quality of the ingot. Inspection found that with the extension of slow cooling time, the surface quality of the ingot is getting better and better. After 60 minutes of slow cooling, the ingot temperature is lower than 100℃, the degree of oxidation on the surface of the ingot is small, the oxide scale is very thin, and the surface is smooth.

[0025] ④ Hot-roll the ingot and check the surface quality of the steel plate. After the ingot is slowly cooled for 60 minutes, the surface quality of the steel plate is the smoothest. When sampling for physical property inspection, there is less waste and the plate utilization rate is higher.

[0026] Application effect of the present invention: Through the implementation of the above method, the oxidation degree of the ingot surface will be effectively reduced, the surface quality of the ingot will be improved, the surface of the steel plate after hot rolling will be relatively smooth, which is conducive to the sampling of various physical property samples, less waste cutting and higher plate utilization rate.

[0027] Comparative Example:

[0028] A method for improving the surface quality of an ingot, comprising the following steps:

[0029] ① Place the weighed pure iron raw material in the crucible of the vacuum induction furnace, put the alloys to be added in the alloy tank, put in the ingot mold and riser brick, and close the vacuum furnace cover.

[0030] ② Turn on the cooling water of the vacuum induction furnace and the control cabinet, start the Roots pump to pump the air in the induction furnace to below 40Pa, and then fill it with argon to 0.6 standard atmospheric pressure. First heat at low power for 8 minutes, and then gradually increase the power to heat until all the raw materials are melted, then deoxidize and alloy, maintain a certain time to promote uniform distribution of the alloy, slowly pour the molten steel into the ingot mold, and stop heating.

[0031] ③ Place the cast ingot mold in the vacuum induction furnace to maintain pressure, take different slow cooling times such as 20min, 30min, 40min, 60min, etc., then open the vacuum furnace cover, lift out the ingot mold, demould, and check the surface quality of the ingot. Inspection found that with the extension of slow cooling time, the surface quality of the ingot is getting better and better. After 60min of slow cooling, the ingot temperature is lower than 100℃, the degree of oxidation on the surface of the ingot is small, the oxide scale is very thin, and the surface is smooth. Other methods cannot achieve this effect.

[0032] ④ The ingots with different slow cooling time were hot rolled by the same process to check the surface quality of the steel plate. By comparison, it was found that after the ingot with slow cooling for 60 minutes was rolled, the surface quality of the steel plate was the smoothest, and when sampling for physical property inspection, there was less waste and the plate utilization rate was higher; others could not achieve this effect.

[0033] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for improving the surface quality of an ingot, characterized in that: The steps include: ①Put the weighed pure iron raw material into the crucible of the vacuum induction furnace, put the alloys to be added into the alloy tank, put in the ingot mold and riser brick, and close the vacuum furnace cover; ② Turn on the cooling water of the vacuum induction furnace and the control cabinet, start the Roots pump to pump the air in the induction furnace to below 40Pa, then fill it with argon to 0.5-0.7 standard atmospheric pressure, first heat at low power for 5-10 minutes, then gradually increase the power to heat until all the raw materials are melted, then deoxidize and alloy, maintain for a certain period of time to promote uniform distribution of the alloy, slowly pour the molten steel into the ingot mold, and stop heating; ③ Place the cast ingot mold in the vacuum induction furnace to maintain pressure, take 50-80 minutes of slow cooling time with the furnace, then open the vacuum furnace cover, lift out the ingot mold, demould, and check the surface quality of the ingot; ④Hot-roll the ingot and check the surface quality of the steel plate.

2. The method for improving the surface quality of an ingot according to claim 1, characterized in that: Start the Roots pump to pump the air in the induction furnace to below 40Pa, and then fill it with argon to 0.5 standard atmospheric pressure.

3. The method for improving the surface quality of ingot casting according to claim 1, characterized in that: Start the Roots pump to pump the air in the induction furnace to below 40Pa, and then fill it with argon to 0.6 standard atmospheric pressure.

4. The method for improving the surface quality of ingot casting according to claim 1, characterized in that: Start the Roots pump to pump the air in the induction furnace to below 40Pa, and then fill it with argon to 0.7 standard atmospheric pressure.

5. The method for improving the surface quality of ingot casting according to claim 1, characterized in that: Take 60-70 minutes of slow cooling time in the furnace.

6. The method for improving the surface quality of ingot casting according to claim 5, characterized in that: Take 60 minutes of slow cooling time in the furnace.

7. The method for improving the surface quality of ingot casting according to claim 6, characterized in that: After slow cooling for 60 minutes, the temperature of the ingot is lower than 100°C, the degree of oxidation on the surface of the ingot is small, the oxide scale is very thin, and the surface is smooth.

8. The method for improving the surface quality of ingot casting according to claim 6 or 7, characterized in that: After the ingot is rolled with slow cooling for 60 minutes, the surface quality of the steel plate is the smoothest. When sampling for physical property inspection, less waste is produced and the plate utilization rate is higher.